1
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Mondal S, Bravaya KB. Complex potential energy surfaces with projected CAP technique: Vibrational excitation of N2. J Chem Phys 2024; 161:024106. [PMID: 38984953 DOI: 10.1063/5.0212647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Accepted: 06/12/2024] [Indexed: 07/11/2024] Open
Abstract
The projected complex absorbing potential (CAP) technique is one of the methods that allow one to extend the bound state methods for computing resonances' energies and widths. Here, we explore the accuracy of the potential energy curves generated with different electronic structure theory methods in combination with the projected CAP technique by considering resonant vibrational excitation (RVE) of N2 by electron impact as a model process. We report RVE cross sections computed using the boomerang model with potential energy curves obtained with CAP-based extended multistate complete active space perturbation theory (XMS-CASPT2) and equation of motion coupled-cluster method for electron attachment with single and double substitution (EOM-EA-CCSD) methods. We also compare potential energy curves computed with several electronic structure methods, including XMS-CASPT2, EOM-EA-CCSD, multireference configuration interaction with singles (MR-CIS) and singles and doubles (MR-CISD). A good agreement is observed between the experiment and simulated RVE cross sections obtained with the potential energy curves generated with XMS-CASPT2 and EOM-EA-CCSD methods, thus highlighting the potential of the projected CAP technique combined with accurate electronic structure methods for dynamical simulations of the processes that proceed through metastable electronic states.
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Affiliation(s)
- Soubhik Mondal
- Department of Chemistry, Boston University, Boston, Massachusetts 02215, USA
| | - Ksenia B Bravaya
- Department of Chemistry, Boston University, Boston, Massachusetts 02215, USA
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2
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Sarma P, Karmakar PK. Effects of negative ions on equilibrium solar plasmas in the fabric of gravito-electrostatic sheath model. Sci Rep 2024; 14:16087. [PMID: 38997327 PMCID: PMC11245523 DOI: 10.1038/s41598-024-66774-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 07/03/2024] [Indexed: 07/14/2024] Open
Abstract
The gravito-electrostatic sheath (GES) model, exploring the solar wind plasma (SWP) origin from the solar interior plasma (SIP) via the solar surface boundary (SSB), is revaluated by including realistic negative ionic species. A constructive numerical analysis of the structuring equations shows that the SIP volume shrinks with an increase in the negative ion concentration. This shrinking nature is independent of ion mass and plasma temperature. The electric potential is insensitive to the negative ion concentration, mass, and plasma temperature. The solar plasma flow dynamics is studied with the Mach number and current density profiles. The sonic transition of the SWP depends on the Ti/Te-ratio. The current density responds to the negative ion density and Ti/Te-ratio in both the SIP and SWP. A deviation from the local quasi-neutrality state is observed in the SIP. The GES model equations result in a modified GES-Bohm sheath criterion in a well justifiable and validated form. The obtained results are then compared with the various observed outcomes and previous GES-based predictions. The relevance of this multi-parametric solar plasma analysis is lastly emphasized on the basis of the current solar research progressions.
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Affiliation(s)
- Pankaj Sarma
- Department of Physics, Tezpur University, Napaam, Tezpur, Assam, 784028, India
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3
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Ashworth EK, Ashworth SH, Bull JN. Spectroscopy and dynamics of isolated anions: Versatile instrumentation for photodetachment and photoelectron spectroscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2024; 95:075103. [PMID: 38984887 DOI: 10.1063/5.0207759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Accepted: 06/19/2024] [Indexed: 07/11/2024]
Abstract
Molecular anions are appealing targets for study because, compared with their neutral and cationic counterparts, they can be probed with conventional laboratory lasers without the need for multiphoton ionization schemes, and they provide spectroscopic details on the corresponding neutral molecules. Here, we describe a section of a modular instrument designed to perform high-throughput photoelectron and photodetachment spectroscopy of gas-phase anions, with future provision for time-resolved and isomer-selective spectroscopy. The instrument framework allows for the incorporation and adaptation of several ion sources, as demonstrated here with plasma (electric) discharge sources providing variable hard to soft ion generation conditions. The generated anions are separated according to their mass-to-charge ratio through time-of-flight mass spectrometry (m/zΔm/z = 500-600) and are focused into a set of perpendicular velocity-map imaging electrodes (ΔEE≈4%), where mass-selected anions are probed using laser light and the ejected electrons are velocity-map imaged. Instrument performance is demonstrated through the acquisition of photodetachment and photoelectron spectra for CH2CN-, showing sharp resonances in the vicinity of the detachment threshold assigned to rovibrational states of a dipole-bound anion and broader lifetime-limited spectral features at photon energies well above the threshold assigned to prompt autodetachment from a temporary anion resonance. Similar measurements could be performed on any molecular anions generated in the sources.
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Affiliation(s)
- Eleanor K Ashworth
- School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - Stephen H Ashworth
- School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - James N Bull
- School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom
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4
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Clarke CJ, Verlet JRR. Dynamics of Anions: From Bound to Unbound States and Everything In Between. Annu Rev Phys Chem 2024; 75:89-110. [PMID: 38277700 DOI: 10.1146/annurev-physchem-090722-125031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2024]
Abstract
Gas-phase anions present an ideal playground for the exploration of excited-state dynamics. They offer control in terms of the mass, extent of solvation, internal temperature, and conformation. The application of a range of ion sources has opened the field to a vast array of anionic systems whose dynamics are important in areas ranging from biology to star formation. Here, we review recent experimental developments in the field of anion photodynamics, demonstrating the detailed insight into photodynamical and electron-capture processes that can be uncovered. We consider the electronic and nuclear ultrafast dynamics of electronically bound excited states along entire reaction coordinates; electronically unbound states showing that photochemical concepts, such as chromophores and Kasha's rule, are transferable to electron-driven chemistry; and nonvalence states that straddle the interface between bound and unbound states. Finally, we consider likely developments that are sure to keep the field of anion dynamics buoyant and impactful.
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Affiliation(s)
- Connor J Clarke
- Department of Chemistry, Durham University, Durham, United Kingdom;
| | - Jan R R Verlet
- Department of Chemistry, Durham University, Durham, United Kingdom;
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5
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Salzmann H, McCoy AB, Weber JM. Infrared Spectrum of the Pyrene Anion in the CH Stretching Region. J Phys Chem A 2024; 128:4225-4232. [PMID: 38753443 DOI: 10.1021/acs.jpca.4c00966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2024]
Abstract
In this work, we report the infrared spectrum of the pyrene anion, measured using messenger tagging with up to three Ar atoms. We assign the spectrum using density functional theory and vibrational perturbation theory. We discuss our results in the context of computed and experimental spectra from the literature as well as recent observations from astronomical sources, addressing the question of whether polycyclic aromatic hydrocarbon anions could contribute to the strong infrared emission bands at 3.29 μm from carbon-rich regions of space.
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Affiliation(s)
- Heinrich Salzmann
- JILA and Department of Chemistry, University of Colorado, Boulder, Colorado 80309-0440, United States
| | - Anne B McCoy
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - J Mathias Weber
- JILA and Department of Chemistry, University of Colorado, Boulder, Colorado 80309-0440, United States
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6
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Cassidy JP, Hofierka J, Cunningham B, Green DG. Many-body theory calculations of positronic-bonded molecular dianions. J Chem Phys 2024; 160:084304. [PMID: 38407288 DOI: 10.1063/5.0188719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Accepted: 01/26/2024] [Indexed: 02/27/2024] Open
Abstract
The energetic stability of positron-dianion systems [A-; e+; A-] is studied via many-body theory, where A- includes H-, F-, Cl-, and the molecular anions (CN)- and (NCO)-. Specifically, the energy of the system as a function of ionic separation is determined by solving the Dyson equation for the positron in the field of the two anions using a positron-anion self-energy as constructed in Hofierka et al. [Nature 606, 688 (2022)] that accounts for correlations, including polarization, screening, and virtual-positronium formation. Calculations are performed for a positron interacting with H22-, F22-, and Cl22- and are found to be in good agreement with previous theory. In particular, we confirm the presence of two minima in the potential energy of the [H-; e+; H-] system with respect to ionic separation: a positronically bonded [H-; e+; H-] local minimum at ionic separations r ∼ 3.4 Å and a global minimum at smaller ionic separations r ≲ 1.6 Å that gives overall instability of the system with respect to dissociation into a H2 molecule and a positronium negative ion, Ps-. The first predictions are made for positronic bonding in dianions consisting of molecular anionic fragments, specifically for (CN)22- and (NCO)22-. In all cases, we find that the molecules formed by the creation of a positronic bond are stable relative to dissociation into A- and e+A- (positron bound to a single anion), with bond energies on the order of 1 eV and bond lengths on the order of several ångstroms.
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Affiliation(s)
- J P Cassidy
- Centre for Light-Matter Interactions, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland, United Kingdom
| | - J Hofierka
- Centre for Light-Matter Interactions, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland, United Kingdom
| | - B Cunningham
- Centre for Light-Matter Interactions, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland, United Kingdom
| | - D G Green
- Centre for Light-Matter Interactions, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland, United Kingdom
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7
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Nag P, Ranković M, Polášek M, Čurík R, Slaughter DS, Fedor J. Contrasting Dynamics in Isoelectronic Anions Formed by Electron Attachment. J Phys Chem Lett 2024; 15:895-902. [PMID: 38241169 PMCID: PMC10839900 DOI: 10.1021/acs.jpclett.3c03460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2023] [Revised: 01/09/2024] [Accepted: 01/12/2024] [Indexed: 01/21/2024]
Abstract
Cyanogen NCCN and cyanoacetylene HCCCN are isoelectronic molecules, and as such, they have many similar properties. We focus on the bond cleavage in these induced by the dissociative electron attachment. In both molecules, resonant electron attachment produces CN- with very similar energy dependence. We investigate the very different dissociation dynamics, in each of the two molecules, revealed by velocity map imaging of this common fragment. Different dynamics are manifested both in the excess energy partitioning and in the angular distributions of fragments. Based on the comparison with electron energy loss spectra, which provide information about possible parent states of the resonances (both optically allowed and forbidden excited states of the neutral target), we ascribe the observed effect to the distortion of the nuclear frame during the formation of core-excited resonance in cyanoacetylene. The proposed mechanism also explains a puzzling difference in the magnitude of the CN- cross section in the two molecules which has been so far unexplained.
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Affiliation(s)
- P. Nag
- J.
Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, 18223 Prague, Czech
Republic
| | - M. Ranković
- J.
Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, 18223 Prague, Czech
Republic
| | - M. Polášek
- J.
Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, 18223 Prague, Czech
Republic
| | - R. Čurík
- J.
Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, 18223 Prague, Czech
Republic
| | - D. S. Slaughter
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - J. Fedor
- J.
Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, 18223 Prague, Czech
Republic
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8
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Gyamfi JA, Jagau TC. A New Strategy to Optimize Complex Absorbing Potentials for the Computation of Resonance Energies and Widths. J Chem Theory Comput 2024. [PMID: 38261549 DOI: 10.1021/acs.jctc.3c01039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2024]
Abstract
Complex absorbing potentials (CAPs) are artificial potentials added to electronic Hamiltonians to make the wave function of metastable electronic states square-integrable. This makes the electronic-structure theory of resonances comparable to that of bound states, thus reducing the complexity of the problem. However, the most often used box and Voronoi CAPs depend on several parameters that have a substantial impact on the numerical results. Among these parameters are the CAP strength and a set of spatial parameters that define the onset of the CAP. It has been a common practice to minimize the perturbation of the resonance states due to the CAP by optimizing the strength parameter while fixing the onset parameters, although the performance of this approach strongly depends on the chosen onset. Here, we introduce a more general approach that allows one to optimize not only the CAP strength but also the spatial parameters. We show that fixing the CAP strength and optimizing the spatial parameters is a reliable way to minimize CAP perturbations. We illustrate the performance of this new approach by computing resonance energies and widths of the temporary anions of dinitrogen, ethylene, and formic acid. This is done at the Hartree-Fock and equation-of-motion coupled-cluster singles and doubles levels of theory using full and projected box and Voronoi CAPs.
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Affiliation(s)
- Jerryman A Gyamfi
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium
| | - Thomas-C Jagau
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium
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9
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Simons J. An environmental impact statement for molecular anions. Phys Chem Chem Phys 2024; 26:1564-1586. [PMID: 38126406 DOI: 10.1039/d3cp04842j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
A molecular anion's (MA's) chemical reactivity and physical behavior can be quite different when it is surrounded by other molecules than when it exists in isolation. This sensitivity to the surrounding environment is especially high for anions because their outermost valence electrons are typically loosely bound and exist in rather spatially diffuse orbitals, allowing even weak intermolecular interactions arising from the environment to have strong effects. This Perspective offers illustrations of such sensitivity for a variety of cases including (i) the effect of solvation on electron binding energies, (ii) how some "well known" anions need to have solvent molecules around to even exist as stable species, (iii) how internal Coulomb repulsions within a multiply charged MA can provide temporary stability toward electron loss, (iv) how MAs arrange themselves spatially near liquid/vapor interfaces in manners that can produce unusual reactivity, (v) how nearby cationic sites can facilitate electron attachment to form a MA site elsewhere, (vi) how internal vibrational or rotational energy can make a MA detach an electron.
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Affiliation(s)
- Jack Simons
- Henry Eyring Center for Theoretical Chemistry, Department of Chemistry, University of Utah, Salt Lake City, UT, 84112, USA.
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10
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Larson Å, Orel AE. Mutual neutralization in collisions of Li + with CN . Phys Chem Chem Phys 2024; 26:1977-1983. [PMID: 38116632 DOI: 10.1039/d3cp05373c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
The mutual neutralization reaction in collisions of Li+ with CN- is a promising candidate for rigorous multi-dimensional ab initio studies of atom-molecule charge transfer processes. The reaction is driven by the non-adiabatic interaction between the lowest two 1A' electronic states at large Li-CN distances, resulting in a large cross section for mutual neutralization. As a first step, the relevant adiabatic potential energy surfaces and non-adiabatic interaction are computed ab initio, and the process is studied quantum mechanically using the vibrational sudden approximation, where the vibrational and rotational motions of the CN molecule are assumed to be frozen during the collision.
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Affiliation(s)
- Åsa Larson
- Department of Physics, Stockholm University, SE-106 91 Stockholm, Sweden.
| | - Ann E Orel
- Department of Chemical Engineering, University of California, Davis, California 95616, USA
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11
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An S, Kim D, Kim J, Kim SK. Excited-state chemistry of the nitromethane anion mediated by the dipole-bound states revealed by photofragment action spectroscopy. Chem Sci 2023; 14:12231-12237. [PMID: 37969601 PMCID: PMC10631229 DOI: 10.1039/d3sc04342h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Accepted: 10/12/2023] [Indexed: 11/17/2023] Open
Abstract
We report the first experimental observation of the excited dipole-bound state (DBS) of the cryogenically cooled nitromethane anion (CH3NO2-), where the excess electron is loosely attached to the singlet or triplet neutral-core. Photofragment and photodetachment action spectra have been employed for the dynamic exploration of Feshbach resonances located even far above the electron detachment threshold, giving excitation profiles from the ground anionic state (D0) to the DBSs which match quite well with the spectral structures of the photoelectron spectra. This indicates that the electron transfer from the nonvalence orbital (of DBS) to the valence orbital (of anion) is mainly responsible for the anionic fragmentation channels, giving strong evidence for that the DBS plays a dynamic doorway-role in the anionic fragmentation reactions. Photofragment action spectra have also been obtained for the anionic clusters of (CH3NO2)2-, (CH3NO2)3-, or (CH3NO2·H2O)-, giving the relative yields of various fragments as a function of the excitation energy for each cluster. The absorption profiles of the anionic clusters exhibit substantial blue-shifts compared to the bare nitromethane anion as their ground states are much stabilized by solvation. The anionic fragmentation pattern varies among different clusters, giving essential clues for the thorough understanding of the whole anionic dynamics such as the dynamic role of the short-lived nonvalence-bound states of the clusters.
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Affiliation(s)
- Sejun An
- Department of Chemistry, KAIST Daejeon 34141 Republic of Korea
| | - Dabin Kim
- Department of Chemistry, KAIST Daejeon 34141 Republic of Korea
| | - Junggil Kim
- Department of Chemistry, KAIST Daejeon 34141 Republic of Korea
| | - Sang Kyu Kim
- Department of Chemistry, KAIST Daejeon 34141 Republic of Korea
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12
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Bogot A, Lioubashevski O, Heber O, Zajfman D, Strasser D. Simultaneous electrostatic trapping of merged cation & anion beams. Phys Chem Chem Phys 2023; 25:25701-25710. [PMID: 37721452 DOI: 10.1039/d3cp03633b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/19/2023]
Abstract
Simultaneous trapping of merged cation and anion beams in the hybrid electrostatic ion beam trap (HEIBT) opens new opportunities for the study of the interactions of isolated atomic molecular or cluster ions with oppositely charged ionic species. Application of the trapped merged beams requires a detailed understanding of the trapping dynamics and the effect of the Coulombic attractive and repulsive forces between the ions on their motion in the trap. The simultaneous trapping regime is explored experimentally for SF6- anion and SF5+ cation beams and compared to realistic ion trajectory simulations. The respective stability of the simultaneously trapped cation and anion beams is experimentally tracked by nondestructive and mass sensitive image charge monitoring. An approximate analytical potential model is presented for modeling the dynamics of trapped ions, providing insight into the role of ion-ion interactions, and suggesting a simplified mirror design.
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Affiliation(s)
- Alon Bogot
- The Hebrew University of Jerusalem, Institute of Chemistry, Jerusalem 91904, Israel.
| | - Oleg Lioubashevski
- The Hebrew University of Jerusalem, Institute of Chemistry, Jerusalem 91904, Israel.
| | - Oded Heber
- Weizmann Institute of Science, Department of Particle Physics and Astrophysics, Rehovot 7610001, Israel
| | - Daniel Zajfman
- Weizmann Institute of Science, Department of Particle Physics and Astrophysics, Rehovot 7610001, Israel
| | - Daniel Strasser
- The Hebrew University of Jerusalem, Institute of Chemistry, Jerusalem 91904, Israel.
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13
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Feng B, Sanov A. Microsolvation of Hot Ions: Spectroscopy and Statistical Mechanics of Phenide-Water Interactions. J Phys Chem A 2023; 127:6437-6446. [PMID: 37498135 DOI: 10.1021/acs.jpca.3c02737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/28/2023]
Abstract
Thermal excitation alters the spectroscopic signatures of solvated ions and affects their interactions with neighboring molecules. By analyzing the photoelectron spectra of microhydrated phenide (Ph-), the temperatures of the Ph-·H2O and Ph-·(H2O)2 clusters from a hot ion source were determined to be 560 and 520 K, respectively, vs 700 K for unsolvated Ph-. Compared to theory predictions for cold clusters, the high temperature of the environment significantly reduces the average hydration stabilization of the ions and the corresponding band shifts in their spectra. The results are discussed in terms of a statistical model that describes the energy content of the intermolecular (IM) degrees of freedom of the cluster, ⟨EIM⟩. We show that over the entire solvation energy range, the density of states associated with the IM modes of Ph-·H2O, of which there are only 6, is more than an order of magnitude greater than that associated with the 27 internal vibrations of the core anion. The results suggest that the observed cluster temperatures are not determined by the ion source but represent the intrinsic properties of the clusters. The energetics and statistical mechanics of microsolvation limit the excitation that the IM degrees of freedom can sustain without significant solvent evaporation on the timescale of the experiment. The limit is expressed as a characteristic solvation temperature (CST), which is the maximum canonical temperature of a stable cluster ensemble. Driven by evaporative cooling, the terminal cluster temperature from a hot ion source will always be close to the cluster's CST. Only if the source temperature is lower than CST will the observed cluster temperature be determined by the source conditions. An approximate rule is proposed for estimating the characteristic temperature of any cluster using the inflection point on the ⟨EIM⟩ vs T curve.
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Affiliation(s)
- Beverly Feng
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States
| | - Andrei Sanov
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States
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14
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Li J, Tu Z, Xiang H, Li Y, Song H. Theoretical studies on the kinetics and dynamics of the BeH + + H 2O reaction: comparison with the experiment. Phys Chem Chem Phys 2023; 25:20997-21005. [PMID: 37503894 DOI: 10.1039/d3cp02322b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
The reaction of BeH+ with background gaseous H2O may play a role in qubit loss for quantum information processing with Be+ as trapped ions, and yet its reaction mechanism has not been well understood until now. In this work, a globally accurate, full-dimensional ground-state potential energy surface (PES) for the BeH+ + H2O reaction was constructed by fitting a total of 170 438 ab initio energy points at the level of RCCSD(T)-F12/aug-cc-pVTZ using the fundamental invariant-neural network method. The total root-mean-square error of the final PES was 0.178 kcal mol-1. For comparison, quasi-classical trajectory calculations were carried out on the PES at an experimental temperature of 150 K. The obtained thermal rate constant and product branching ratio of the BeD+ + H2O reaction agreed quite well with experimental results. In addition, the vibrational state distributions and energy disposals of the products were calculated and rationalized using the sudden vector projection model.
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Affiliation(s)
- Jiaqi Li
- College of Physical Science and Technology, Huazhong Normal University, Wuhan 430079, China.
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China.
| | - Zhao Tu
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China.
- School of Chemical and Environmental Engineering, Hubei Minzu University, Enshi 445000, China
| | - Haipan Xiang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China.
- School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Yong Li
- College of Physical Science and Technology, Huazhong Normal University, Wuhan 430079, China.
| | - Hongwei Song
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China.
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15
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Schröder B. Ab Initio Rovibrational Spectroscopy of the Acetylide Anion. Molecules 2023; 28:5700. [PMID: 37570670 PMCID: PMC10420331 DOI: 10.3390/molecules28155700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 07/22/2023] [Accepted: 07/22/2023] [Indexed: 08/13/2023] Open
Abstract
In this work the rovibrational spectrum of the acetylide anion HCC- is investigated using high-level electronic structure methods and variational rovibrational calculations. Using a composite approach the potential energy surface and dipole surface is constructed from explicitly correlated coupled-cluster accounting for corrections due to core-valence correlation, scalar relativistic effects and higher-order excitation effects. Previous approaches for approximating the latter are critically evaluated. Employing the composite potential, accurate spectroscopic parameters determined from variational calculations are presented. In comparison to the few available reference data the present results show excellent agreement with ground state rotational constants within 0.005% of the experimental value. Intensities determined from the variational calculations suggest the bending fundamental transition ν2 around 510 cm-1 to be the best target for detection. The rather weak CD stretching fundamental ν1 in deuterated isotopologues show a second-order resonance with the (0,20,1) state and the consequences are discussed in some detail. The spectroscopic parameters and band intensities provided for a number of vibrational bands in isotopologues of the acetylide anion should facilitate future spectroscopic investigations.
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Affiliation(s)
- Benjamin Schröder
- Institute of Physical Chemistry, University of Goettingen, Tammannstr. 6, 37077 Göttingen, Germany
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16
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Ayasli A, Khan A, Michaelsen T, Gstir T, Ončák M, Wester R. Imaging Frontside and Backside Attack in Radical Ion-Molecule Reactive Scattering. J Phys Chem A 2023. [PMID: 37354118 DOI: 10.1021/acs.jpca.3c02856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/26/2023]
Abstract
We report on the reactive scattering of methyl iodide, CH3I, with atomic oxygen anions O-. This radical ion-molecule reaction can produce different ionic products depending on the angle of attack of the nucleophile O- on the target molecule. We present results on the backside and frontside attack of O- on CH3I, which can lead to I- and IO- products, respectively. We combine crossed-beam velocity map imaging with quantum chemical calculations to unravel the chemical reaction dynamics. Energy-dependent scattering experiments in the range of 0.3-2.0 eV relative collision energy revealed that three different reaction pathways can lead to I- products, making it the predominant observed product. Backside attack occurs via a hydrogen-bonded complex with observed indirect, forward, and sideways scattered iodide products. Halide abstraction via frontside attack produces IO-, which mainly shows isotropic and backward scattered products at low energies. IO- is observed to dissociate further to I- + O at a certain energy threshold and favors more direct dynamics at higher collision energies.
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Affiliation(s)
- Atilay Ayasli
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25/3, 6020 Innsbruck, Austria
| | - Arnab Khan
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25/3, 6020 Innsbruck, Austria
| | - Tim Michaelsen
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25/3, 6020 Innsbruck, Austria
| | - Thomas Gstir
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25/3, 6020 Innsbruck, Austria
| | - Milan Ončák
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25/3, 6020 Innsbruck, Austria
| | - Roland Wester
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25/3, 6020 Innsbruck, Austria
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17
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Kocheril GS, Gao HW, Wang LS. Observation of a long-lived triplet excited state and strong electron correlation effects in the copper oxide anion (CuO-) using cryogenic photoelectron imaging. J Chem Phys 2023; 158:236101. [PMID: 37318178 DOI: 10.1063/5.0151516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 05/30/2023] [Indexed: 06/16/2023] Open
Affiliation(s)
- G Stephen Kocheril
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA
| | - Han-Wen Gao
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA
| | - Lai-Sheng Wang
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA
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18
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Abstract
This Perspective attempts to shed light on developments in the theoretical and experimental study of molecular anions highlighting more recent workers in the field. The species I discuss include (i) valence-bound (singly and multiply charged) anions including atmospheric, catalytic, superhalogen, interfacial, and more; (ii) dipole- and correlation-bound anions including their role as doorways to other states and their appearance "in space", and (iii) metastable anions focusing on tools needed for their theoretical treatment. I also briefly discuss angular distributions of photodetached electrons and their growing utilization in experiments and theory. A recurring theme is the dependence of electron binding energies (EBEs) on the surrounding environment. Some anions that are nonexistent as isolated species evolve to be stable but with small EBEs when weakly solvated (e.g., as in a cluster or at an air-solvent interface). Others existing in isolation only as metastable species become stable when the underlying molecular framework contains one or more positively charged group (e.g., protonated side chains in a peptide) that generates a stabilizing Coulomb potential. On the other hand, a destabilizing Coulomb potential between/among negative sites in a multiply charged anion decreases the EBEs of each such site and generates a repulsive Coulomb barrier that can affect stability.
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Affiliation(s)
- Jack Simons
- Henry Eyring Center for Theoretical Chemistry, Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
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19
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Das S, Samanta K. Recent Advances in the Study of Negative-Ion Resonances Using Multiconfigurational Propagator and a Complex Absorbing Potential. Chemphyschem 2023; 24:e202200546. [PMID: 36223261 DOI: 10.1002/cphc.202200546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 10/12/2022] [Indexed: 02/03/2023]
Abstract
The transient resonances are a challenge to bound state quantum mechanics. These states lie in the continuum part of the spectrum of the Hamiltonian. For this, one has to treat a continuum problem due to electron-molecule scattering and the many-electron correlation problem simultaneously. Moreover, the description of a resonance requires a wavefunction that bridges the part that resembles a bound state with another that resembles a continuum state such that the continuity of the wavefunction and its first derivative with respect to the distance between the incoming projectile and the target is maintained. A review of the recent advances in the theoretical investigation of the negative-ion resonances (NIR) is presented. The NIRs are ubiquitous in nature. They result from the scattering of electrons off of an atomic or molecular target. They are important for numerous chemical processes in upper atmosphere, space and even biological systems. A contextual background of the existing theoretical methods as well as the newly-developed multiconfigurational propagator tools based on a complex absorbing potential are discussed.
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Affiliation(s)
- Subhasish Das
- School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Kansapada, Argul, 752050, India
| | - Kousik Samanta
- School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Kansapada, Argul, 752050, India
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20
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Das S, Samanta K. Investigation of electron-induced scattering resonances using a multiconfigurational polarization propagator and a complex absorbing potential. Chem Phys 2023. [DOI: 10.1016/j.chemphys.2022.111712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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21
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Ru B, Sanov A. Photoelectron Spectra of Hot Polyatomic Ions: A Statistical Treatment of Phenide. J Phys Chem A 2022; 126:9423-9439. [DOI: 10.1021/acs.jpca.2c07361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Beverly Ru
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona85721, United States
| | - Andrei Sanov
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona85721, United States
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22
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Murakami T, Iida R, Hashimoto Y, Takahashi Y, Takahashi S, Takayanagi T. Ring-Polymer Molecular Dynamics and Kinetics for the H – + C 2H 2 → H 2 + C 2H – Reaction Using the Full-Dimensional Potential Energy Surface. J Phys Chem A 2022; 126:9244-9258. [DOI: 10.1021/acs.jpca.2c05851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Tatsuhiro Murakami
- Department of Chemistry, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama City, Saitama338-8570, Japan
- Department of Materials & Life Sciences, Faculty of Science & Technology, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo102-8554, Japan
| | - Ryusei Iida
- Department of Chemistry, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama City, Saitama338-8570, Japan
| | - Yu Hashimoto
- Department of Chemistry, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama City, Saitama338-8570, Japan
| | - Yukinobu Takahashi
- Department of Chemistry, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama City, Saitama338-8570, Japan
| | - Soma Takahashi
- Department of Chemistry, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama City, Saitama338-8570, Japan
| | - Toshiyuki Takayanagi
- Department of Chemistry, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama City, Saitama338-8570, Japan
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23
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Sagan CR, Anstöter CS, Thodika M, Wilson KD, Matsika S, Garand E. Spectroscopy and Theoretical Modeling of Tetracene Anion Resonances. J Phys Chem Lett 2022; 13:10245-10252. [PMID: 36301005 DOI: 10.1021/acs.jpclett.2c02931] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The positions and widths of the optically allowed electronic states of the tetracene radical anion located above the detachment threshold energy (i.e anion resonances) are mapped out using total photodetachment yield spectroscopy of cryogenically cooled ions. The presence of these states is detected via the sharp increase in the photodetachment yield compared to that of the monotonic nonresonant direct photodetachment background. The resolution of the resulting spectrum is limited by the ∼5 cm-1 line width of the tunable laser and thus provides a stringent benchmark for computations of the energies and autodetachment lifetimes of these resonance states. The experimental results are compared to high-level electronic structure computations and line width modeling using the orbital stabilization method. These theoretical results are found to be in near quantitative agreement with the experimental data, highlighting their capability to accurately describe the energies and lifetimes of anion resonances for relatively large molecules.
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Affiliation(s)
- Cole R Sagan
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave, Madison, Wisconsin 53706, United States
| | - Cate S Anstöter
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
- Department of Chemistry, University of York, Heslington YO10 5DD, U.K
| | - Mushir Thodika
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Kenneth D Wilson
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave, Madison, Wisconsin 53706, United States
| | - Spiridoula Matsika
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Etienne Garand
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave, Madison, Wisconsin 53706, United States
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24
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Kang DH, Kim J, Eun HJ, Kim SK. State-Specific Chemical Dynamics of the Nonvalence Bound State of the Molecular Anions. Acc Chem Res 2022; 55:3032-3042. [PMID: 36206486 DOI: 10.1021/acs.accounts.2c00512] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Nonvalence bound states (NBS) are anionic states where the excess electron is extremely loosely bound to the neutral core through long-range potentials. In contrast to the valence orbitals of which the electron occupancy determines the molecular structure, as well as the chemical reactivity, the nonvalence orbital is quite diffuse and located far from the neutral core. The NBS can be classified into the dipole-bound state (DBS), quadruple-bound state (QBS), or correlation-bound state (CBS) according to the nature of the electron-neutral interaction, although their interaction potentials may cooperatively contribute. The NBS is ubiquitous in nature and has the strong implications in atmospheric, interstellar, or biological chemistry. Accordingly, NBS has long been conceived to play the role of the doorway into the formation of a stable anion or dissociative electron attachment (DEA). Despite intensive and extensive studies, however, the quantum-mechanical nature of NBS is still far from being thorough understanding. Herein, we describe a new aspect of state-specific NBS-mediated chemical dynamics, which has been revealed through a series of recent studies by our group. We have employed picosecond time-resolved pump-probe spectroscopy combined with cryogenically cooled ion trap and velocity-map imaging techniques to study closed-shell anions generated by electrospray ionization. DBS vibrational Feshbach resonances are prepared by the optical excitation of phenoxide, for instance, and their individual lifetimes have been precisely measured in a state-specific manner to reveal the strong mode-dependency of the autodetachment rate. Fermi's golden rule turns out to be extremely useful for a rational explanation of the experiment, although the more sophisticated theoretical model is desirable for the more quantitative analysis. For the DBS of para-chlorophenoxide or para-bromophenoxide where the polarizability of neutral core is substantial, the Fermi's golden rule based on the charge-dipole potential needs to be significantly modified to include the correlation effects to explain the exceptionally slow autodetachment rates. For the QBS of 4-cyanophenoxide, the mode-specific behavior of the quadrupole ellipsoid tensor explains the strong mode-dependent autodetachment rate. Meanwhile, the nonadiabatic transition of the excess electron into the valence orbital can result in stable anion formation or immediate chemical bond rupture. In the DBS of ortho-, meta-, or para-iodophenoxide, the transformation of the loosely bound excess electron into the πσ* antibonding orbital occurs to give I- as a final fragment. The fragmentation mediated by DBS occurs competitively with the concomitant autodetachment, paving a new way of the reaction control by tuning the quantum-mechanical nature of the DBS Feshbach resonance. This experimental observation provides the foremost evidence for the dynamic role of the DBS as a doorway into anion chemistry, such as DEA. The ponderomotive force on the electron in the nonvalence orbital has been demonstrated for the first time in a strong optical field, giving great promise for the manipulation of polyatomic molecules in terms of the spatial location, as well as the AC-Stark control of the chemical reaction.
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Affiliation(s)
- Do Hyung Kang
- Department of Chemistry, KAIST, Daejeon34141, Republic of Korea
| | - Jinwoo Kim
- Department of Chemistry, KAIST, Daejeon34141, Republic of Korea
| | - Han Jun Eun
- Department of Chemistry, KAIST, Daejeon34141, Republic of Korea
| | - Sang Kyu Kim
- Department of Chemistry, KAIST, Daejeon34141, Republic of Korea
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25
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Abstract
Negative ions are important in many areas of science and technology, e.g., in interstellar chemistry, for accelerator-based radionuclide dating, and in anti-matter research. They are unique quantum systems where electron-correlation effects govern their properties. Atomic anions are loosely bound systems, which with very few exceptions lack optically allowed transitions. This limits prospects for high-resolution spectroscopy, and related negative-ion detection methods. Here, we present a method to measure negative ion binding energies with an order of magnitude higher precision than what has been possible before. By laser-manipulation of quantum-state populations, we are able to strongly reduce the background from photodetachment of excited states using a cryogenic electrostatic ion-beam storage ring where keV ion beams can circulate for up to hours. The method is applicable to negative ions in general and here we report an electron affinity of 1.461 112 972(87) eV for 16O.
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26
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Gyamfi JA, Jagau TC. Ab Initio Molecular Dynamics of Temporary Anions Using Complex Absorbing Potentials. J Phys Chem Lett 2022; 13:8477-8483. [PMID: 36054015 PMCID: PMC9486942 DOI: 10.1021/acs.jpclett.2c01969] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2022] [Accepted: 08/15/2022] [Indexed: 06/15/2023]
Abstract
Dissociative electron attachment, that is, the cleavage of chemical bonds induced by low-energy electrons, is difficult to model with standard quantum-chemical methods because the involved anions are not bound but subject to autodetachment. We present here a new computational development for simulating the dynamics of temporary anions on complex-valued potential energy surfaces. The imaginary part of these surfaces describes electron loss, whereas the gradient of the real part represents the force on the nuclei. In our method, the forces are computed analytically based on Hartree-Fock theory with a complex absorbing potential. Ab initio molecular dynamics simulations for the temporary anions of dinitrogen, ethylene, chloroethane, and the five mono- to tetrachlorinated ethylenes show qualitative agreement with experiments and offer mechanistic insights into dissociative electron attachments. The results also demonstrate how our method evenhandedly deals with molecules that may undergo dissociation upon electron attachment and those which only undergo autodetachment.
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27
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Gayvert JR, Bravaya KB. Application of Box and Voronoi CAPs for Metastable Electronic States in Molecular Clusters. J Phys Chem A 2022; 126:5070-5078. [PMID: 35881428 DOI: 10.1021/acs.jpca.2c04892] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The complex absorbing potential (CAP) approach offers a practical tool for characterization of energies and lifetimes of metastable electronic states, such as temporary anions and core ionized states. Here, we present an implementation of the smooth Voronoi CAP combined with the equation-of-motion coupled cluster with single and double substitutions method for metastable states. The performances of the smooth Voronoi CAP and box CAP are compared for different classes of systems: resonances in isolated molecules and localized and delocalized resonances in molecular clusters. The benchmark calculations show that the Voronoi CAP is generally more robust when applied to molecular clusters, but box CAPs are equally reliable for localized resonances or in the cases when the resonance does not exhibit significant electron density delocalization into the intramolecular region. As such, the choice of the CAP shape and onset should be guided by the character of the metastable states.
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Affiliation(s)
- James R Gayvert
- Department of Chemistry, Boston University, Boston, Massachusetts 02215, United States
| | - Ksenia B Bravaya
- Department of Chemistry, Boston University, Boston, Massachusetts 02215, United States
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28
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Laws BA, Levey ZD, Sanov A, Stanton JF, Schmidt TW, Gibson ST. Velocity map imaging spectroscopy of C 2H - and C 2D -: A benchmark study of vibronic coupling interactions. J Chem Phys 2022; 157:044305. [PMID: 35922361 DOI: 10.1063/5.0100297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
High-resolution velocity-map imaged photoelectron spectra of the ethynyl anions C2H- and C2D- are measured at photon wavelengths between 355 and 266 nm to investigate the complex interactions between the closely lying X̃2Σ+ and Ã2Π electronic states. An indicative kinetic energy resolution of 0.4%, together with the full angular dependence of the fast electrons, provides a detailed description of the vibronically coupled structure. It is demonstrated that a modest quadratic vibronic coupling model, parameterized by the quasidiabatic ansatz, is sufficient to accurately recreate all the observed vibronic interactions. Simulated spectra are shown to be in excellent agreement with the experimental data, verifying the proposed model and providing a framework that may be used to accurately simulate spectra of larger C2nH monohydride carbon chains. New spectral assignments are supported by experimental electron anisotropy measurements and Dyson orbital calculations.
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Affiliation(s)
- Benjamin A Laws
- School of Chemistry, University of New South Wales, Sydney NSW 2052, Australia
| | - Zachariah D Levey
- School of Chemistry, University of New South Wales, Sydney NSW 2052, Australia
| | - Andrei Sanov
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, USA
| | - John F Stanton
- Department of Chemistry, University of Florida, Gainesville, Florida 32611, USA
| | - Timothy W Schmidt
- School of Chemistry, University of New South Wales, Sydney NSW 2052, Australia
| | - Stephen T Gibson
- Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
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29
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Sensing the ortho Positions in C6Cl6 and C6H4Cl2 from Cl2− Formation upon Molecular Reduction. Molecules 2022; 27:molecules27154820. [PMID: 35956769 PMCID: PMC9369944 DOI: 10.3390/molecules27154820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 07/22/2022] [Accepted: 07/25/2022] [Indexed: 11/17/2022] Open
Abstract
The geometrical effect of chlorine atom positions in polyatomic molecules after capturing a low-energy electron is shown to be a prevalent mechanism yielding Cl2−. In this work, we investigated hexachlorobenzene reduction in electron transfer experiments to determine the role of chlorine atom positions around the aromatic ring, and compared our results with those using ortho-, meta- and para-dichlorobenzene molecules. This was achieved by combining gas-phase experiments to determine the reaction threshold by means of mass spectrometry together with quantum chemical calculations. We also observed that Cl2− formation can only occur in 1,2-C6H4Cl2, where the two closest C–Cl bonds are cleaved while the chlorine atoms are brought together within the ring framework due to excess energy dissipation. These results show that a strong coupling between electronic and C–Cl bending motion is responsible for a positional isomeric effect, where molecular recognition is a determining factor in chlorine anion formation.
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30
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Bâldea I. Comprehensive Quantum Chemical Characterization of the Astrochemically Relevant HC
n
H Chain Family: An Attempt to Aid Astronomical Observations. ADVANCED THEORY AND SIMULATIONS 2022. [DOI: 10.1002/adts.202200244] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Ioan Bâldea
- Theoretical Chemistry Heidelberg University Im Neuenheimer Feld 229 D‐69120 Heidelberg Germany
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31
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Kumar S, Izadi F, Ončák M, Limão-Vieira P, Denifl S. Hexachlorobenzene-negative ion formation in electron attachment experiments. Phys Chem Chem Phys 2022; 24:13335-13342. [PMID: 35608112 DOI: 10.1039/d2cp01360f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this contribution, we report a comprehensive study on the formation of hexachlorobenzene (C6Cl6) negative ions probed by low-energy electron interactions from 0 up to 12 eV in a gas-phase crossed beam experiment. The anionic yields as a function of the electron energy reveal a rich fragmentation pattern of the dissociative electron attachment process, yet the most intense ion has been assigned to the non-dissociated parent anion that survives long enough within the detection time window. Other less intense fragment anions have been assigned as Cl-, Cl2-, C6Cl4-, and C6Cl5-. The experimental results are accompanied by quantum chemical calculations at various levels of accuracy, providing an insight into the electronic structure, thermochemical thresholds, electron affinities and structures of neutral and anionic molecular species. The electron attachment process induces a considerable geometry change in the temporary-negative ion relative to the neutral molecule, where the most intense fragment anion assigned to Cl- can be formed solely through a curve crossing involving a π*/σ* coupling. The yield of chlorine anions shows a signature of vibrational excitation reminiscent of a Jahn-Teller distortion.
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Affiliation(s)
- S Kumar
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal.
| | - F Izadi
- Institute for Ion Physics and Applied Physics, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria.
| | - M Ončák
- Institute for Ion Physics and Applied Physics, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria.
| | - P Limão-Vieira
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal.
| | - S Denifl
- Institute for Ion Physics and Applied Physics, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria.
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32
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Stockett MH, Bull JN, Schmidt HT, Zettergren H. Statistical vibrational autodetachment and radiative cooling rates of para-benzoquinone. Phys Chem Chem Phys 2022; 24:12002-12010. [PMID: 35535575 DOI: 10.1039/d2cp00490a] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We report measurements of the statistical vibrational autodetachment (VAD, also called thermionic emission) and radiative cooling rates of isolated para-benzoquinone (pBQ, C6H4O2) radical anions using the cryogenic electrostatic ion storage ring facility DESIREE. The results are interpreted using master equation simulations with rate coefficients calculated using statistical detailed balance theory. The VAD rate is determined by measuring the time-dependent yield of neutral pBQ due to spontaneous electron emission from a highly-excited ensemble of anions formed in an electron-attachment ion source. Competition with radiative cooling quenches the VAD rate after a critical time of τc = 11.00(5) ms. Master equation simulations which reproduce the VAD yield provide an estimate of the initial effective vibrational temperature of the ions of 1100(20) K, and provide insight into the anion formation scenario. A second measurement of the radiative cooling rate of pBQ- stored for up to 0.5 s was achieved using time-dependent photodetachment action spectroscopy across the 2Au ← 2B2g and 2B2u ← 2B2g transitions. The rate at which hot-band contributions fade from the action spectrum is quantified by non-negative matrix factorisation. This is found to be commensurate with the average vibrational energy extracted from the simulations, with 1/e lifetimes of 0.16(3) s and 0.1602(7) s, respectively. Implications for astrochemistry are discussed.
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Affiliation(s)
- Mark H Stockett
- Department of Physics, Stockholm University, Stockholm, Sweden.
| | - James N Bull
- School of Chemistry, University of East Anglia, Norwich, UK
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33
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Mogren Al Mogren M, Ben Abdallah D, Dhaif Allah Al Harbi S, Senent ML. Collision excitation of c-C 3H -(X 1A 1) by He. J Chem Phys 2022; 156:184302. [PMID: 35568567 DOI: 10.1063/5.0089458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Accurate modeling of anionic abundances in the interstellar and circumstellar media requires calculations of collisional data with the most abundant species that are usually He atoms and H2 molecules. In this paper, we focus on smaller cyclic molecular anion, c-C3H-, an astrophysical candidate, following the detection of larger CnH- carbon chains. From a new three-dimensional potential energy surface, the rotational (de-)excitation of the c-C3H-(X1A1) anion by collision with He is investigated. The surface is obtained in the supermolecular approach at the CCSD(T)-F12/aug-cc-pVTZ level of theory. Fully quantum close-coupling calculations of inelastic integral cross sections are performed on a grid of collisional energies large enough to ensure the convergence of the state-to-state rate coefficients for the 34 first rotational levels up to jKa,Kc = 77,0 of c-C3H- and temperatures ranging from 5 to 100 K. For this collisional system, rate coefficients exhibit a strong dominance in favor of 21,2 → l1,1 downward transition. This transition was previously used for the detection of the cyclic parent c-C3H. The c-C3H--He rate coefficients (∼10-11 cm3 s-1) are of the same order of magnitude as those of the detected anions CnH- (as C2H-, C4H-, and C6H-) in collision with He and one order of magnitude smaller than those with H2. The critical densities of H2 were also estimated, and a discussion on the validity of the local thermodynamic equilibrium conditions is carried out. This work represents the contribution to understanding and modeling abundances and chemistry of hydrocarbon radicals, CnH, in astrophysical media.
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Affiliation(s)
- Muneerah Mogren Al Mogren
- Faculty of Science, Department of Chemistry, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
| | - Driss Ben Abdallah
- Laboratoire de Physique Moléculaire, Ecole Supérieure des Sciences et Techniques de Tunis, 5 Av. Taha Hussein, Tunis 1008, Tunisia
| | - Sarah Dhaif Allah Al Harbi
- Department of Chemistry, College of Science, Imam Mohammad Ibn Saud Islamic University, Riyadh 11623, Saudi Arabia
| | - Maria Luisa Senent
- Departamento de Química y Física Teóricas, Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121, Unidad Asociada GIFMAN, CSIC-UHU, Madrid 28006, Spain
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34
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Bâldea I. HC nH - Anion Chains with n ≤ 8 Are Nonlinear and Their Permanent Dipole Makes Them Potential Candidates for Astronomical Observation. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27103100. [PMID: 35630577 PMCID: PMC9144574 DOI: 10.3390/molecules27103100] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 04/30/2022] [Accepted: 05/09/2022] [Indexed: 11/16/2022]
Abstract
To be detectable in space via radio astronomy, molecules should have a permanent dipole moment. This is the plausible reason why HCnH chains are underproportionally represented in the interstellar medium in comparison with the isoelectronically equivalent HCnN chain family, which is the most numerous homologous series astronomically observed so far. In this communication, we present results of quantum chemical calculations for the HCnH family at several levels of theory: density functional theory (DFT/B3LYP), coupled-cluster expansions (ROCCSD(T)), and G4 composite model. Contradicting previous studies, we report here that linear HCnH− anion chains with sizes of astrochemical interest are unstable (i.e., not all calculated frequencies are real). Nonlinear cis and trans HCnH− anion chains turn out to be stable both against molecular vibrations (i.e., all vibrational frequencies are real) and against electron detachment (i.e., positive electroaffinity). The fact that the cis anion conformers possess permanent dipole is the main encouraging message that this study is aiming at conveying to the astrochemical community, as this makes them observable by means of radio astronomy.
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Affiliation(s)
- Ioan Bâldea
- Theoretical Chemistry, Heidelberg University, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany
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35
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Song K, Song H, Li J. Validating experiments for the reaction H 2 + NH 2- by dynamical calculations on an accurate full-dimensional potential energy surface. Phys Chem Chem Phys 2022; 24:10160-10167. [PMID: 35420091 DOI: 10.1039/d2cp00870j] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ion-molecule reactions play key roles in the field of ion related chemistry. As a prototypical multi-channel ion-molecule reaction, the reaction H2 + NH2- → NH3 + H- has been studied for decades. In this work, we develop a new globally accurate potential energy surface (PES) for the title system based on hundreds of thousands of sampled points over a wide dynamically relevant region that covers long-range interacting configuration space. The permutational invariant polynomial-neural network (PIP-NN) method is used for fitting and the resulting total root mean squared error (RMSE) is extremely small, 0.026 kcal mol-1. Extensive dynamical and kinetic calculations are carried out on this PIP-NN PES. Impressively, a unique phenomenon of significant reactivity suppression by exciting the rotational mode of H2 is reported, supported by both the quasi-classical trajectory (QCT) and quantum dynamics (QD) calculations. Further analysis uncovers that exciting the H2 rotational mode would prevent the formation of the reactant complex and thus suppress the reactivity. The calculated rate coefficients for H2/D2 + NH2- agree well with the experimental results, which show an inverse temperature dependence from 50 to 300 K, consistent with the capture nature of this barrierless reaction. The significant kinetic isotope effect observed by experiments is well reproduced by the QCT computations as well.
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Affiliation(s)
- Kaisheng Song
- School of Chemistry and Chemical Engineering & Chongqing Key Laboratory of Theoretical and Computational Chemistry, Chongqing University, Chongqing 401331, P. R. China.
| | - Hongwei Song
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China.
| | - Jun Li
- School of Chemistry and Chemical Engineering & Chongqing Key Laboratory of Theoretical and Computational Chemistry, Chongqing University, Chongqing 401331, P. R. China.
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36
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Sajeev Y, Thodika M, Matsika S. A Unique QP Partitioning and Siegert Width Using Real-Valued Continuum-Remover Potential. J Chem Theory Comput 2022; 18:2863-2874. [DOI: 10.1021/acs.jctc.1c01096] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Y. Sajeev
- Theoretical Chemistry Section, Bhabha Atomic Research Centre, Mumbai 400085, India
| | - Mushir Thodika
- Department of Chemistry, Temple University, 1901 N 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Spiridoula Matsika
- Department of Chemistry, Temple University, 1901 N 13th Street, Philadelphia, Pennsylvania 19122, United States
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37
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Dore L, Bizzocchi L, Lattanzi V, Melosso M, Tamassia F, McCarthy MC. First Laboratory Detection of N 13CO - and Semiexperimental Equilibrium Structure of the NCO - Anion. J Phys Chem A 2022; 126:1899-1904. [PMID: 35285635 PMCID: PMC8958587 DOI: 10.1021/acs.jpca.2c00313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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The cyanate anion
(NCO–) is a species of considerable
astrophysical relevance. It is widely believed to be embedded in interstellar
ices present in young stellar objects but has not yet been detected
in the dense gas of the interstellar medium. Here we report highly
accurate laboratory measurements of the rotational spectrum of the
N13CO– isotopologue at submillimeter
wavelengths along with the detection of three additional lines of
the parent isotopologue up to 437.4 GHz. With this new data, the rotational
spectrum of both isotopologues can be predicted to better 0.25 km
s–1 in equivalent radial velocity up to 1 THz, more
than adequate for an astronomical search in any source. Moreover,
a semiexperimental equilibrium structure of the anion is derived by
combining the experimental ground-state rotational constants of the
two isotopologues with theoretical vibrational corrections, obtained
by using the coupled-cluster method with inclusion of single and double
excitations and perturbative inclusion of triple excitations (CCSD(T)).
The estimated accuracy of the two bond distances is on the order of
5 × 10–4 Å: a comparison to the values
obtained by geometry optimization with the CCSD(T) method and the
use of a composite scheme, including additivity and basis-set extrapolation
techniques, reveals that this theoretical procedure is very accurate.
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Affiliation(s)
- Luca Dore
- Dipartimento di Chimica "Giacomo Ciamician", Università di Bologna, Via Selmi 2, I-40126 Bologna, Italy
| | - Luca Bizzocchi
- Dipartimento di Chimica "Giacomo Ciamician", Università di Bologna, Via Selmi 2, I-40126 Bologna, Italy
| | - Valerio Lattanzi
- Center for Astrochemical Studies, Max Planck Institut für Extraterrestrische Physik Gießenbachstraße 1, D-85748 Garching bei München, Germany
| | - Mattia Melosso
- Dipartimento di Chimica "Giacomo Ciamician", Università di Bologna, Via Selmi 2, I-40126 Bologna, Italy.,Scuola Superiore Meridionale, Università di Napoli Federico II, Largo San Marcellino 10, I-80138 Naples, Italy
| | - Filippo Tamassia
- Dipartimento di Chimica Industriale "Toso Montanari", Università di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy
| | - Michael C McCarthy
- Center for Astrophysics
- Harvard & Smithsonian, 60 Garden St., Cambridge, Massachusetts 02138, United States
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38
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Gayvert JR, Bravaya KB. Projected CAP-EOM-CCSD method for electronic resonances. J Chem Phys 2022; 156:094108. [DOI: 10.1063/5.0082739] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- James R Gayvert
- Boston University Department of Chemistry, United States of America
| | - Ksenia B. Bravaya
- Department of Chemistry, Boston University, United States of America
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39
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Associative detachment in anion-atom reactions involving a dipole-bound electron. Nat Commun 2022; 13:818. [PMID: 35145072 PMCID: PMC8831523 DOI: 10.1038/s41467-022-28382-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 12/27/2021] [Indexed: 11/21/2022] Open
Abstract
Associative electronic detachment (AED) between anions and neutral atoms leads to the detachment of the anion’s electron resulting in the formation of a neutral molecule. It plays a key role in chemical reaction networks, like the interstellar medium, the Earth’s ionosphere and biochemical processes. Here, a class of AED involving a closed-shell anion (OH−) and alkali atoms (rubidium) is investigated by precisely controlling the fraction of electronically excited rubidium. Reaction with the ground state atom gives rise to a stable intermediate complex with an electron solely bound via dipolar forces. The stability of the complex is governed by the subtle interplay of diabatic and adiabatic couplings into the autodetachment manifold. The measured rate coefficients are in good agreement with ab initio calculations, revealing pronounced steric effects. For excited state rubidium, however, a lower reaction rate is observed, indicating dynamical stabilization processes suppressing the coupling into the autodetachment region. Our work provides a stringent test of ab initio calculations on anion-neutral collisions and constitutes a generic, conceptual framework for understanding electronic state dependent dynamics in AEDs. Associative electronic detachment (AED) reactions of anions play a key role in many natural processes. Here, Hassan and colleagues investigate AED reactions between hydroxyl anions and ultracold rubidium atoms in a hybrid atom-ion trap, revealing different dynamics for collisions with ground and electronically excited state rubidium.
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40
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Hassan SZ, Tauch J, Kas M, Nötzold M, Wester R, Weidemüller M. Quantum state-dependent anion-neutral detachment processes. J Chem Phys 2022; 156:094304. [DOI: 10.1063/5.0082734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Saba Zia Hassan
- Physikalisches Institut, Ruprecht Karls Universität Heidelberg Physikalisches Institut, Germany
| | - Jonas Tauch
- Ruprecht Karls Universität Heidelberg Physikalisches Institut, Germany
| | - Milaim Kas
- Deutsches Elektronen-Synchrotron, Germany
| | | | - Roland Wester
- Institute for Ion Physics and Applied Physics, Universität Innsbruck Fakultät für Mathematik Informatik und Physik, Austria
| | - Matthias Weidemüller
- Physikalisches Institut, Ruprecht Karls Universität Heidelberg Fakultät für Physik und Astronomie, Germany
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41
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Xiang H, Tian L, Li Y, Song H. Energy- and Local-Gradient-Based Neural Network Method for Accurately Describing Long-Range Interaction: Application to the H 2 + CO + Reaction. J Phys Chem A 2022; 126:352-363. [PMID: 34989591 DOI: 10.1021/acs.jpca.1c09719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The long-range interaction plays an important role in theoretically describing ion-molecule reaction. However, most energy-based neural network fitting methods usually introduce spurious long-range interactions. In this work, we propose an energy- and local-gradient-based neural network (ELGNN) method to fit potential energy surfaces (PESs). K-means clustering is employed to divide the whole configuration space into three regions: reactant asymptotic region, interaction region, and product asymptotic region. In the interaction region, only the energies of sampled points are computed, while in the asymptotic regions, the gradients of partially sampled configurations are calculated as well, and both the energies and energy gradients (if necessary) are used to fit long-range interactions. These regions are joined together by switching functions. The ELGNN method is first applied to fit the PES of the H2 + CO+ reaction, which has significant long-range interactions. It is found that the ELGNN method works better than the energy-based NN method in describing long-range interactions. The dynamics and kinetics of the reaction are then investigated on the new PES.
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Affiliation(s)
- Haipan Xiang
- College of Physical Science and Technology, Huazhong Normal University, Wuhan 430079, China.,State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Li Tian
- College of Physical Science and Technology, Huazhong Normal University, Wuhan 430079, China.,State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Yong Li
- College of Physical Science and Technology, Huazhong Normal University, Wuhan 430079, China
| | - Hongwei Song
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
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42
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Zhu Y, Li R, Song H. Kinetic and dynamic studies of the NH 2+ + H 2 reaction on a high-level ab initio potential energy surface. Phys Chem Chem Phys 2022; 24:25663-25672. [DOI: 10.1039/d2cp03859e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The dynamics and kinetics of the NH2+ + H2 reaction are investigated on a newly developed ab initio potential energy surface using the quasi-classical trajectory method.
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Affiliation(s)
- Yongfa Zhu
- School of Chemistry and Chemical Engineering, Hubei Polytechnic University, Huangshi 435003, China
| | - Rui Li
- School of Chemistry and Chemical Engineering, Hubei Polytechnic University, Huangshi 435003, China
| | - Hongwei Song
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
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43
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Bull JN, Anstöter CS, Stockett MH, Clarke CJ, Gibbard JA, Bieske EJ, Verlet JRR. Nonadiabatic Dynamics between Valence, Nonvalence, and Continuum Electronic States in a Heteropolycyclic Aromatic Hydrocarbon. J Phys Chem Lett 2021; 12:11811-11816. [PMID: 34870432 DOI: 10.1021/acs.jpclett.1c03532] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Internal conversion between valence-localized and dipole-bound states is thought to be a ubiquitous process in polar molecular anions, yet there is limited direct evidence. Here, photodetachment action spectroscopy and time-resolved photoelectron imaging with a heteropolycyclic aromatic hydrocarbon (hetero-PAH) anion, deprotonated 1-pyrenol, is used to demonstrate a subpicosecond (τ1 = 160 ± 20 fs) valence to dipole-bound state internal conversion following excitation of the origin transition of the first valence-localized excited state. The internal conversion dynamics are evident in the photoelectron spectra and in the photoelectron angular distributions (β2 values) as the electronic character of the excited state population changes from valence to nonvalence. The dipole-bound state subsequently decays through mode-specific vibrational autodetachment with a lifetime τ2 = 11 ± 2 ps. These internal conversion and autodetachment dynamics are likely common in molecular anions but difficult to fingerprint due to the transient existence of the dipole-bound state. Potential implications of the present excited state dynamics for interstellar hetero-PAH anion formation are discussed.
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Affiliation(s)
- James N Bull
- School of Chemistry, Norwich Research Park, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - Cate S Anstöter
- Department of Chemistry, Temple University, 1901 N 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Mark H Stockett
- Department of Physics, Stockholm University, Stockholm SE-106 91, Sweden
| | - Connor J Clarke
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Jemma A Gibbard
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Evan J Bieske
- School of Chemistry, University of Melbourne, Melbourne, VIC 3010, Australia
| | - Jan R R Verlet
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
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44
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Rocha CMR, Linnartz H. High-level ab initio quartic force fields and spectroscopic characterization of C 2N . Phys Chem Chem Phys 2021; 23:26227-26240. [PMID: 34787132 DOI: 10.1039/d1cp03505c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
While it is now well established that large carbon chain species and radiative electron attachment (REA) are key ingredients triggering interstellar anion chemistry, the role played by smaller molecular anions, for which REA appears to be an unlikely formation pathway, is as yet elusive. Advancing this research undoubtedly requires the knowledge (and modeling) of their astronomical abundances which, for the case of C2N-, is largely hindered by a lack of accurate spectroscopic signatures. In this work, we provide such data for both ground -CCN-(3Σ-) and low-lying c-CNC-(1A1) isomers and their singly-substituted isotopologues by means of state-of-the-art rovibrational quantum chemical techniques. Their quartic force fields are herein calibrated using a high-level composite energy scheme that accounts for extrapolations to both one-particle and (approximate) -particle basis set limits, in addition to relativistic effects, with the final forms being subsequently subject to nuclear motion calculations. Besides standard spectroscopic attributes, the full set of computed properties includes fine and hyperfine interaction constants and can be readily introduced as guesses in conventional experimental data reduction analyses through effective Hamiltonians. On the basis of benchmark calculations performed anew for a minimal test set of prototypical triatomics and limited (low-resolution) experimental data for -CCN-(3Σ-), the target accuracies are determined to be better than 0.1% of experiment for rotational constants and 0.3% for vibrational fundamentals. Apart from laboratory investigations, the results here presented are expected to also prompt future astronomical surveys on C2N-. To this end and using the theoretically-predicted spectroscopic constants, the rotational spectra of both -CCN-(3Σ-) and c-CNC-(1A1) are derived and their likely detectability in the interstellar medium is further explored in connection with working frequency ranges of powerful astronomical facilities. Our best theoretical estimate places c-CNC-(1A1) at about 15.3 kcal mol-1 above the ground-state -CCN-(3Σ-) species.
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Affiliation(s)
- C M R Rocha
- Laboratory for Astrophysics, Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, The Netherlands.
| | - H Linnartz
- Laboratory for Astrophysics, Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, The Netherlands.
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45
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Dobulis MA, Thompson MC, Jarrold CC. Identification of Isoprene Oxidation Reaction Products via Anion Photoelectron Spectroscopy. J Phys Chem A 2021; 125:10089-10102. [PMID: 34755517 DOI: 10.1021/acs.jpca.1c08176] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We present a study on the oxidation of isoprene under several different conditions that may model both atmospheric and combustion chemistry. Anions, formed by passing isoprene/oxidant gas mixtures through a pulsed discharge generating a range of species, are separated via mass spectrometry and characterized by anion photoelectron (PE) spectroscopy supported by computations. Specifically, a UV-irradiated isoprene/O2 mixture, which additionally produces O3, and an isoprene/O2/H2 mixture, which generates •OH when passed through the discharge, were sampled. The mass spectra of ions generated under both conditions show the production of intact molecular ions, ion-molecule complexes (e.g., O2-, O4-, and O2-·isoprene), and singly deprotonated species (e.g., deprotonated isoprene, C5H7-). In addition, both smaller and oxidized fragments are observed using both gas mixtures, though relative abundances differ. From the UV-irradiated isoprene/O2 gas mixture, additional intact molecular products of reactions initiated by ozonolysis of isoprene, methylglyoxal, and dimethylglyoxal were observed. Fragmentation and oxidation of isoprene observed in both gas mixtures included species with m/z 39, 53, 67, 69, and 83 that we attribute to a series of alkyl- and alkenoxide-based anions. The coexistence of intact molecules and complexes with fragments and reaction products demonstrates the versatility of this ion source as a simple and efficient anion formation method for studying species that may be relevant in atmospheric and combustion chemistry.
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Affiliation(s)
- Marissa A Dobulis
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Michael C Thompson
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Caroline Chick Jarrold
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
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46
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Laws BA, Levey ZD, Schmidt TW, Gibson ST. Velocity Map Imaging Spectroscopy of the Dipole-Bound State of CH 2CN -: Implications for the Diffuse Interstellar Bands. J Am Chem Soc 2021; 143:18684-18692. [PMID: 34726415 DOI: 10.1021/jacs.1c08762] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Weakly bound anionic systems present a new domain for negative ion spectroscopy. Here we report on a multifaceted study of the CH2CN- dipole-bound state, employing high-resolution photoelectron spectroscopy from 130 different wavelengths, velocity-map imaging at threshold, and laser scanning photodetachment experiments. This uncovers a wide variety of different vibrational and rotational autodetaching resonances. By examination of both sides of the problem, absorption from the anion to the dipole-bound state and vibrational/rotational autodetachment to the neutral, a complete model of the dipole-bound chemistry is formed. Precise values for the electron affinity EA = 12468.9(1) cm-1, dipole binding energy DBE = 40.2(3) cm-1, and anion inversion splitting ω5 = 115.9(2) cm-1 are obtained. This model is then employed to study possible astronomical implications, revealing good agreement between the K = 1 ← 0 CH2CN- dipole transition and the λ8040 diffuse interstellar band.
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Affiliation(s)
- Benjamin A Laws
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia.,Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia
| | - Zachariah D Levey
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Timothy W Schmidt
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Stephen T Gibson
- Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia
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47
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Pan M, Xiang H, Li Y, Song H. Study on the kinetics and dynamics of the H 2 + NH 2- reaction on a high-level ab initio potential energy surface. Phys Chem Chem Phys 2021; 23:17848-17855. [PMID: 34612274 DOI: 10.1039/d1cp02423j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Gas-phase ion-molecule reactions play major roles in many fields of chemistry and physics. The reaction of an amino radical anion with a hydrogen molecule is one of the simplest proton transfer reactions involving anions. A globally accurate full-dimensional potential energy surface (PES) for the NH2- + H2 reaction is developed by the fundamental invariant-neural network method, resulting in a root mean square error of 0.116 kcal mol-1. Quasi-classical trajectory calculations are then carried out on the newly developed PES to give integral cross sections, differential cross sections and thermal rate coefficients. This reaction has two reaction channels, proton transfer and hydrogen exchange. The reactivity of the proton transfer channel is about one or two orders of magnitude stronger than that of the hydrogen exchange channel in the energy range studied. Vibrational excitation of H2 promotes the proton transfer reaction, while fundamental excitation of each vibrational mode of NH2- has a negligible effect. In addition, the theoretical rate coefficients of the proton transfer reaction on the PES show inverse temperature dependence from 150 to 750 K, in accordance with the available experimental results.
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Affiliation(s)
- Mengyi Pan
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China.
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48
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Sandström H, Rahm M. The Beginning of HCN Polymerization: Iminoacetonitrile Formation and Its Implications in Astrochemical Environments. ACS EARTH & SPACE CHEMISTRY 2021; 5:2152-2159. [PMID: 34476321 PMCID: PMC8397470 DOI: 10.1021/acsearthspacechem.1c00195] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 07/08/2021] [Accepted: 07/14/2021] [Indexed: 05/12/2023]
Abstract
Hydrogen cyanide (HCN) is known to react with complex organic materials and is a key reagent in the formation of various prebiotic building blocks, including amino acids and nucleobases. Here, we explore the possible first step in several such processes, the dimerization of HCN into iminoacetonitrile. Our study combines steered ab initio molecular dynamics and quantum chemistry to evaluate the kinetics and thermodynamics of base-catalyzed dimerization of HCN in the liquid state. Simulations predict a formation mechanism of iminoacetonitrile that is consistent with experimentally observed time scales for HCN polymerization, suggesting that HCN dimerization may be the rate-determining step in the assembly of more complex reaction products. The predicted kinetics permits for iminoacetonitrile formation in a host of astrochemical environments, including on the early Earth, on periodically heated subsurfaces of comets, and following heating events on colder bodies, such as Saturn's moon Titan.
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49
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Simpson M, Nötzold M, Michaelsen T, Wild R, Gianturco FA, Wester R. Influence of a Supercritical Electric Dipole Moment on the Photodetachment of C_{3}N^{-}. PHYSICAL REVIEW LETTERS 2021; 127:043001. [PMID: 34355920 DOI: 10.1103/physrevlett.127.043001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 04/28/2021] [Accepted: 05/26/2021] [Indexed: 06/13/2023]
Abstract
Threshold photodetachment spectroscopy of the molecular ion C_{3}N^{-} has been performed at both 16(1) and 295(2) K in a 22-pole ion trap. The 295(2) K spectrum shows a large increase in the cross section with an onset about 200 cm^{-1} below threshold, which is explained by significant vibrational excitation of the trapped ions at room temperature. This excitation disappears at cryogenic temperatures leading to an almost steplike onset of the cross section at threshold, which cannot be adequately described with a Wigner threshold law. Instead, we show that the model developed by O'Malley for photodetachment from neutrals with large permanent dipoles [Phys. Rev. 137, A1668 (1965)PHRVAO0031-899X10.1103/PhysRev.137.A1668] fits very well to the data. A high-resolution scan of the threshold region yields additional features, which we assign to the rotational P and R branches of an electronic transition to a dipole-bound state with ^{1}Σ^{+} symmetry. This state is found 2(1) cm^{-1} below threshold in very good agreement with a recent computational prediction. We furthermore refine the value of the electron affinity of C_{3}N to be 34 727(1) cm^{-1}.
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Affiliation(s)
- Malcolm Simpson
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Markus Nötzold
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Tim Michaelsen
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Robert Wild
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Franco A Gianturco
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Roland Wester
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
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50
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Hart CA, Mabbs R. Stabilized resonances are no less exciting. Nat Chem 2021; 13:721-722. [PMID: 34294913 DOI: 10.1038/s41557-021-00755-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- C Annie Hart
- Department of Chemistry, Washington University, One Brookings Dr. St. Louis, MO, USA
| | - Richard Mabbs
- Department of Chemistry, Washington University, One Brookings Dr. St. Louis, MO, USA.
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