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Kasai T, Muthiah B, Po X, Yan C, Lin K, Tanudji J, Diño WA. Pattern analysis of the impact‐parameter dependent trajectories for the H +
H
2
exchange reaction at
T
=
3
and
300 K
: A characteristic propensity for reactive versus nonreactive trajectories found in the time‐dependent interaction potential and a roaming‐like libration motion at cold temperature. J CHIN CHEM SOC-TAIP 2022. [DOI: 10.1002/jccs.202100539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Toshio Kasai
- Department of Chemistry National Taiwan University Taipei Taiwan
- Department of Applied Physics Osaka University Suita Japan
| | | | - Xin‐Hui Po
- Department of Chemistry National Taiwan University Taipei Taiwan
- Department of Statistics National Chengchi University Taipei Taiwan
| | - Chu‐Chun Yan
- Department of Chemistry National Taiwan University Taipei Taiwan
| | - King‐Chuen Lin
- Department of Chemistry National Taiwan University Taipei Taiwan
- Department of Chemistry, Institute of Atomic and Molecular Sciences Academia Sinica Taipei Taiwan
| | | | - Wilson Agerico Diño
- Department of Applied Physics Osaka University Suita Japan
- Center for Atomic and Molecular Technologies Osaka University Suita Japan
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2
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Tsai PY, Palazzetti F. Photodissociation dynamics of CO-forming channel of methyl formate at 193 nm: a computational study. Mol Phys 2021. [DOI: 10.1080/00268976.2021.1977405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Po-Yu Tsai
- Department of Chemistry, National Chung Hsing University, Taichung, Taiwan
| | - Federico Palazzetti
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy
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3
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Nakamura M, Chang HP, Lin KC, Kasai T, Che DC, Palazzetti F, Aquilanti V. Stereodynamic Imaging of Bromine Atomic Photofragments Eliminated from 1-Bromo-2-methylbutane Oriented via Hexapole State Selector. J Phys Chem A 2019; 123:6635-6644. [PMID: 31177785 DOI: 10.1021/acs.jpca.9b04048] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Both single-laser and two-laser experiments were conducted to look into the ion-imaging of Br*(2P1/2) and Br(2P3/2) photofragmented from 1-bromo-2-methylbutane in the range 232-240 nm via a detection scheme of (2+1) resonance-enhanced multiphoton ionization. The angular analysis of these photofragment distributions yields the anisotropy parameter β = 1.88 ± 0.06 for the Br* excited state which arises from a parallel transition, while β = 0.63 ± 0.09 for the Br ground state indicates the contribution from both a perpendicular transition and a non-adiabatic transition. When a hexapole coupled with an orienting field was implemented, the parent molecules are spatially oriented to yield an orientation efficiency |⟨cos θ⟩| of 0.15. Besides the χ angle between the recoil velocity v and the transition dipole moment μ, orienting molecules allows for the evaluation of the angle α between v and the permanent molecular dipole moment d. The angular analysis of Br* photofragment distribution yields χ = 11.5° and α in the range from 160° to 180° with weak dependency. In the two-laser experiments, the angular anisotropy of Br photofragment distribution was found to be smaller (0.38 ± 0.10) when the photolysis wavelength was red-shifted to 240 nm, suggesting the increasing contributions from perpendicular transitions.
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Affiliation(s)
- Masaaki Nakamura
- Department of Chemistry , National Taiwan University , Taipei 10617 , Taiwan
| | - Hsiu-Pu Chang
- Department of Chemistry , National Taiwan University , Taipei 10617 , Taiwan
| | - King-Chuen Lin
- Department of Chemistry , National Taiwan University , Taipei 10617 , Taiwan.,Institute of Atomic and Molecular Sciences , Academia Sinica , Taipei 10617 , Taiwan
| | - Toshio Kasai
- Department of Chemistry , National Taiwan University , Taipei 10617 , Taiwan.,Institute of Scientific and Industrial Research , Osaka University , Ibaraki, Osaka 567-0047 , Japan
| | - Dock-Chil Che
- Department of Chemistry, Graduate School of Science , Osaka University , Toyonaka, Osaka 560-0043 , Japan
| | - Federico Palazzetti
- Dipartimento di Chimica, Biologia e Biotecnologie , Università di Perugia , 06123 Perugia , Italy
| | - Vincenzo Aquilanti
- Dipartimento di Chimica, Biologia e Biotecnologie , Università di Perugia , 06123 Perugia , Italy.,Istituto di Struttura della Materia , Consiglio Nazionale delle Ricerche , 00016 Rome , Italy
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4
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Nucleophilic substitution vs elimination reaction of bisulfide ions with substituted methanes: exploration of chiral selectivity by stereodirectional first-principles dynamics and transition state theory. J Mol Model 2019; 25:227. [PMID: 31317347 DOI: 10.1007/s00894-019-4126-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 07/07/2019] [Indexed: 10/26/2022]
Abstract
Control of molecular orientation is emerging as crucial for the characterization of the stereodynamics of kinetics processes beyond structural stereochemistry. The special role played in chiral discrimination phenomena has been particularly emphasized by Aquilanti and collaborators after their extensive probes of experimental control of molecular alignment and orientation. In this work, the manifestation of the Aquilanti mechanism has been demonstrated for the first time in first-principles molecular dynamics simulations: stationary points characterized on potential energy surfaces have been calculated for the study of chemical reactions occurring between the bisulfide anion HS- and oriented prototypical chiral molecules CHFXY (where X = CH3 or CN and Y = Cl or I). The important reaction channels are those corresponding to bimolecular nucleophilic substitution (SN2) and to bimolecular elimination (E2): their relative role has been assessed and alternative pathways due to the mirror forms of the oriented chiral molecule are revealed by the different reactivity of the two enantiomers of CHFCNI in SN2 reaction.
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5
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Nakamura M, Palazzetti F, Tsai PY, Yang SJ, Lin KC, Kasai T, Che DC, Lombardi A, Aquilanti V. Vectorial imaging of the photodissociation of 2-bromobutane oriented via hexapolar state selection. Phys Chem Chem Phys 2019; 21:14164-14172. [PMID: 30350830 DOI: 10.1039/c8cp04270e] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Molecular orientation techniques are becoming available in the study of elementary chemical processes, in order to highlight those structural and dynamical properties that would be concealed by random rotational motions. Recently successful orientation was achieved for asymmetric-top and chiral molecules of much larger complexity than hitherto. In this work, we report and discuss the correlation between the vectors' photofragment recoil velocity v, transition dipole moment μ, and permanent dipole moment d in a dissociation experiment on hexapole oriented 2-bromobutane, photoinitiated by a linearly polarized laser. The sliced ion images of the Br*(2P1/2) and Br(2P3/2) photofragments were acquired at 234.0 and 254.1 nm, respectively, by a (2 + 1) resonance-enhanced multiphoton ionization technique. A detailed analysis of the sliced ion images obtained at a tilting angle 45° of laser polarization provides information on the correlation of the three vectors, which are confined by two polar angles α and χ and one azimuthal angle φμd in the recoil frame. The sliced ion images of Br fragments eliminated individually from the enantiomers at 254.1 nm yield an asymmetric factor close to zero; for this reason the photofragment angular distributions do not show significant differences. The elimination of the Br* fragment at 234.0 nm is mainly correlated with a parallel transition, giving rise to a large anisotropy parameter of 1.85, and thus can be considered as a single state excitation. The resulting recoil frame angles are optimized to 163° ± 8° and 164° ± 1° for α and χ, respectively, whereas φμd is approaching 0° for the best fit. Since for the present molecule, the three vectors have an only slight spatial arrangement, the photofragment angular distributions of the two enantiomers do not show appreciable differences. Theoretical and computational simulations provide us the basis to state that oriented enantiomers can be discriminated on-the-fly in photodissociation processes even initiated by non-circularly polarized light, provided that the three vectors encountered above have specific three-dimensional arrangements. The fact that Br fragment elimination involves a multi-potential dissociation carries uncertainties in theoretical estimates of the vector direction. Therefore, this work represents a preliminary but significant step on the road to chiral discrimination on-the-fly, which is shown to be best propitiated in molecules where vectors are far from having degenerate mutual angular directions.
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Affiliation(s)
- Masaaki Nakamura
- Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan.
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6
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From statistical thermodynamics to molecular kinetics: the change, the chance and the choice. RENDICONTI LINCEI. SCIENZE FISICHE E NATURALI 2018. [DOI: 10.1007/s12210-018-0749-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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7
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Kasai T, Che DC, Tsai PY, Nakamura M, Muthiah B, Lin KC. Roaming and chaotic behaviors in collisional and photo-initiated molecular-beam reactions: a role of classical vs. quantum nonadiabatic dynamics. RENDICONTI LINCEI. SCIENZE FISICHE E NATURALI 2018. [DOI: 10.1007/s12210-018-0709-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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8
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Falcinelli S, Vecchiocattivi F, Alagia M, Schio L, Richter R, Stranges S, Catone D, Arruda MS, Mendes LAV, Palazzetti F, Aquilanti V, Pirani F. Double photoionization of propylene oxide: A coincidence study of the ejection of a pair of valence-shell electrons. J Chem Phys 2018; 148:114302. [PMID: 29566526 DOI: 10.1063/1.5024408] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Propylene oxide, a favorite target of experimental and theoretical studies of circular dichroism, was recently discovered in interstellar space, further amplifying the attention to its role in the current debate on protobiological homochirality. In the present work, a photoelectron-photoion-photoion coincidence technique, using an ion-imaging detector and tunable synchrotron radiation in the 18.0-37.0 eV energy range, permits us (i) to observe six double ionization fragmentation channels, their relative yields being accounted for about two-thirds by the couple (C2H4+, CH2O+) and one-fifth by (C2H3+, CH3O+); (ii) to measure thresholds for their openings as a function of photon energy; and (iii) to unravel a pronounced bimodality for a kinetic-energy-released distribution, fingerprint of competitive non-adiabatic mechanisms.
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Affiliation(s)
- Stefano Falcinelli
- Dipartimento di Ingegneria Civile ed Ambientale, Università di Perugia, Via G. Duranti 93, 06125 Perugia, Italy
| | - Franco Vecchiocattivi
- Dipartimento di Ingegneria Civile ed Ambientale, Università di Perugia, Via G. Duranti 93, 06125 Perugia, Italy
| | - Michele Alagia
- IOM-CNR Tasc, Km 163.5, Area Science Park, 34149 Basovizza, Trieste, Italy
| | - Luca Schio
- IOM-CNR Tasc, Km 163.5, Area Science Park, 34149 Basovizza, Trieste, Italy
| | - Robert Richter
- Elettra-Sincrotrone Trieste, Area Science Park, 34149 Basovizza, Trieste, Italy
| | - Stefano Stranges
- IOM-CNR Tasc, Km 163.5, Area Science Park, 34149 Basovizza, Trieste, Italy
| | - Daniele Catone
- Istituto di Struttura della Materia (CNR-ISM), Area della Ricerca di Roma Tor Vergata, Via del Fosso del Cavaliere, 100-00133 Roma, Italy
| | - Manuela S Arruda
- Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy
| | - Luiz A V Mendes
- Instituto de Fìsica, Universidade Federal da Bahia, Campus Universitario de Ondina, 40210-340 Salvador, BA, Brazil
| | - Federico Palazzetti
- Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy
| | - Vincenzo Aquilanti
- Istituto di Struttura della Materia (CNR-ISM), Area della Ricerca di Roma Tor Vergata, Via del Fosso del Cavaliere, 100-00133 Roma, Italy
| | - Fernando Pirani
- Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy
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9
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Lombardi A, Palazzetti F. Chirality in molecular collision dynamics. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:063003. [PMID: 29350184 DOI: 10.1088/1361-648x/aaa1c8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Chirality is a phenomenon that permeates the natural world, with implications for atomic and molecular physics, for fundamental forces and for the mechanisms at the origin of the early evolution of life and biomolecular homochirality. The manifestations of chirality in chemistry and biochemistry are numerous, the striking ones being chiral recognition and asymmetric synthesis with important applications in molecular sciences and in industrial and pharmaceutical chemistry. Chiral discrimination phenomena, due to the existence of two enantiomeric forms, very well known in the case of interaction with light, but still nearly disregarded in molecular collision studies. Here we review some ideas and recent advances about the role of chirality in molecular collisions, designing and illustrating molecular beam experiments for the demonstration of chiral effects and suggesting a scenario for a stereo-directional origin of chiral selection.
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Affiliation(s)
- Andrea Lombardi
- Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto 8, 06123, Perugia, Italy. Consortium for Computational Molecular and Materials Sciences (CMS)2, Via Elce di Sotto, 8, 06123 Perugia, Italy
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10
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Cernuto A, Pirani F, Martini LM, Tosi P, Ascenzi D. The Selective Role of Long-Range Forces in the Stereodynamics of Ion-Molecule Reactions: The He + +Methyl Formate Case From Guided-Ion-Beam Experiments. Chemphyschem 2018; 19:51-59. [PMID: 29045020 DOI: 10.1002/cphc.201701096] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Indexed: 12/20/2022]
Abstract
Long-range intermolecular forces play a crucial role in controlling the outcome of ion-molecule chemical reactions, such as those determining the disappearance of organic or inorganic "complex" molecules recently detected in various regions of the interstellar medium due to collisions with abundant interstellar atomic ions (e.g. H+ and He+ ). Theoretical treatments, for example, based on simple capture models, are nowadays often adopted to evaluate the collision-energy dependence of reactive cross sections and the temperature dependent rate coefficients of many ion-molecule reactions. The obtained results are widely used for the modelling of phenomena occurring in different natural environments or technological applications such as astrophysical and laboratory plasmas. Herein it is demonstrated, through a combined experimental and theoretical investigation on a prototype ion-molecule reaction (He+ +methyl formate), that the dynamics, investigated in detail, shows some intriguing features that can lead to rate coefficients at odds with the expectations (e.g. Arrhenius versus anti-Arrhenius behaviour). Therefore, this study casts light on some new and general guidelines to be properly taken into account for a suitable evaluation of rate coefficients of ion-molecule reactions.
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Affiliation(s)
- Andrea Cernuto
- Dipartimento di Fisica, Universitá di Trento, Via Sommarive 14, 38123, Trento, Italy
| | - Fernando Pirani
- Dipartimento di Chimica, Biologia e Biotecnologie, Universitá di Perugia, Via Elce di Sotto 8, Perugia, Italy.,Istituto di Nanotecnologia (CNR NANOTEC), 70126, Bari, Italy
| | - Luca Matteo Martini
- Dipartimento di Fisica, Universitá di Trento, Via Sommarive 14, 38123, Trento, Italy
| | - Paolo Tosi
- Dipartimento di Fisica, Universitá di Trento, Via Sommarive 14, 38123, Trento, Italy
| | - Daniela Ascenzi
- Dipartimento di Fisica, Universitá di Trento, Via Sommarive 14, 38123, Trento, Italy
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11
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Nakamura M, Yang SJ, Lin KC, Kasai T, Che DC, Lombardi A, Palazzetti F, Aquilanti V. Stereodirectional images of molecules oriented by a variable-voltage hexapolar field: Fragmentation channels of 2-bromobutane electronically excited at two photolysis wavelengths. J Chem Phys 2017; 147:013917. [DOI: 10.1063/1.4981025] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Affiliation(s)
- Masaaki Nakamura
- Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan
| | - Shiun-Jr Yang
- Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan
| | - King-Chuen Lin
- Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Toshio Kasai
- Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan
- Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan
| | - Dock-Chil Che
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Andrea Lombardi
- Università di Perugia, Dipartimento di Chimica, Biologia e Biotecnologie, 06123 Perugia, Italy
| | - Federico Palazzetti
- Università di Perugia, Dipartimento di Chimica, Biologia e Biotecnologie, 06123 Perugia, Italy
| | - Vincenzo Aquilanti
- Università di Perugia, Dipartimento di Chimica, Biologia e Biotecnologie, 06123 Perugia, Italy
- Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, 00016 Rome, Italy
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12
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Pin JM, Mija A, Sbirrazzuoli N. Stereodynamic control of star-epoxy/anhydride crosslinking actuated by liquid-crystalline phase transitions. SOFT MATTER 2017; 13:1956-1965. [PMID: 28170018 DOI: 10.1039/c6sm02624a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The epoxy/anhydride copolymerization kinetics of an original star-epoxy monomer (TriaEP) was explored in dynamic heating mode using a series of isoconversional methods. Negative values of the apparent activation energy (Eα) related to an anti-Arrhenius behavior were observed. The transition from Arrhenius to anti-Arrhenius behavior and vice versa depending on the Eα of polymerization was correlated with the dynamics of mesophasic fall-in/fall-out events, physically induced transition (PIT) and chemically induced transition (CIT). This self-assembly phenomenon induces the generation of an anisotropic crosslinked architecture exhibiting both nematic discotic (ND) and nematic columnar (NC) organization. Particular emphasis was placed on evaluating the juxtaposition/contribution of the liquid-crystalline transitions to crosslinking, considering both the reaction dynamics and the macromolecular vision.
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Affiliation(s)
- Jean-Mathieu Pin
- Université Côte d'Azur, Institut de Chimie de Nice, UMR CNRS 7272, 06108 Nice cedex 02, France.
| | - Alice Mija
- Université Côte d'Azur, Institut de Chimie de Nice, UMR CNRS 7272, 06108 Nice cedex 02, France.
| | - Nicolas Sbirrazzuoli
- Université Côte d'Azur, Institut de Chimie de Nice, UMR CNRS 7272, 06108 Nice cedex 02, France.
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13
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Tsai PY. On the state selection of linear triatomic molecules by electrostatic hexapole fields. J Chem Phys 2016; 145:104311. [PMID: 27634264 DOI: 10.1063/1.4962359] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Electrostatic hexapole state-selector is a versatile tool in experimental stereodynamics. The requirement of appropriate models to correctly predict the behavior of molecules in the hexapole motivated us to realize a treatment that predicts the Stark effect of linear triatomic molecules with rotational doublet states. Various perturbative approximations are conventionally adopted to obtain analytic Stark energy derivatives of a truncated Hamiltonian matrix, without utilizing numerical diagonalization of the full Hamiltonian matrix. By including both the low and high field effects, which were alternatively ignored in the analytical formulae of such approximate approaches, herein we demonstrate that the performance of hexapole state selector to linear triatomic molecules can be appropriately predicted via Van Vleck transformation. This method can provide analytic Stark energy derivatives that are acceptably in consistent with the ones obtained via numerical diagonalization of the full Hamiltonian matrix. Particularly, this work is suitable for v2 = 1 level of linear triatomic molecules, due to the following reasons: (1) the Stark energy derivative and the molecular orientation as a function of the electric field are expressed in analytical formulae, hence it is suitable for implementation without involving numerical diagonalization of the full Hamiltonian matrix; (2) a better prediction of the focusing curves with respect to conventional analytical treatments is provided, allowing a reliable determination of the selected state compositions and molecular orientation.
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Affiliation(s)
- Po-Yu Tsai
- Department of Chemistry, National Chung Hsing University, Taichung 402, Taiwan
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14
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Nakamura M, Yang SJ, Tsai PY, Kasai T, Lin KC, Che DC, Lombardi A, Palazzetti F, Aquilanti V. Hexapole-Oriented Asymmetric-Top Molecules and Their Stereodirectional Photodissociation Dynamics. J Phys Chem A 2016; 120:5389-98. [PMID: 27139246 DOI: 10.1021/acs.jpca.6b02410] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Molecular orientation is a fundamental requisite in the study of stereodirected dynamics of collisional and photoinitiated processes. In this past decade, variable hexapolar electric filters have been developed and employed for the rotational-state selection and the alignment of molecules of increasing complexity, for which the main difficulties are their mass, their low symmetry, and the very dense rotational manifold. In this work, for the first time, a complex molecule such as 2-bromobutane, an asymmetric top containing a heavy atom (the bromine), was successfully oriented by a weak homogeneous field placed downstream from the hexapolar filter. Efficiency of the orientation was characterized experimentally, by combining time-of-flight measurements and a slice-ion-imaging detection technique. The application is described to the photodissociation dynamics of the oriented 2-bromobutane, which was carried out at a laser wavelength of 234 nm, corresponding to the breaking of the C-Br bond. The Br photofragment is produced in both the ground Br ((2)P3/2) and the excited Br ((2)P1/2) electronic states, and both channels are studied by the slice imaging technique, revealing new features in the velocity and angular distributions with respect to previous investigations on nonoriented molecules.
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Affiliation(s)
- Masaaki Nakamura
- Department of Chemistry, National Taiwan University , Taipei, Taiwan
| | - Shiun-Jr Yang
- Department of Chemistry, National Taiwan University , Taipei, Taiwan
| | - Po-Yu Tsai
- Department of Chemistry, National Taiwan University , Taipei, Taiwan.,Department of Chemistry, National Chung-Hsing University , Taichung, Taiwan
| | - Toshio Kasai
- Department of Chemistry, National Taiwan University , Taipei, Taiwan
| | - King-Chuen Lin
- Department of Chemistry, National Taiwan University , Taipei, Taiwan.,Institute of Atomic and Molecular Sciences, Academia Sinica , Taipei, Taiwan
| | - Dock-Chil Che
- Graduate School of Science, Department of Chemistry, Osaka University , Osaka, Japan
| | - Andrea Lombardi
- Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia , Perugia, Italy
| | - Federico Palazzetti
- Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia , Perugia, Italy.,Scuola Normale Superiore , Pisa, Italy
| | - Vincenzo Aquilanti
- Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia , Perugia, Italy.,Consiglio Nazionale delle Ricerche, Istituto di Struttura della Materia , 00016 Roma, Italy.,Insituto de Fìsica, Universidade Federal da Bahia , Salvador, Brazil
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15
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Coutinho ND, Aquilanti V, Silva VHC, Camargo AJ, Mundim KC, de Oliveira HCB. Stereodirectional Origin of anti-Arrhenius Kinetics for a Tetraatomic Hydrogen Exchange Reaction: Born-Oppenheimer Molecular Dynamics for OH + HBr. J Phys Chem A 2016; 120:5408-17. [PMID: 27205872 DOI: 10.1021/acs.jpca.6b03958] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Among four-atom processes, the reaction OH + HBr → H2O + Br is one of the most studied experimentally: its kinetics has manifested an unusual anti-Arrhenius behavior, namely, a marked decrease of the rate constant as the temperature increases, which has intrigued theoreticians for a long time. Recently, salient features of the potential energy surface have been characterized and most kinetic aspects can be considered as satisfactorily reproduced by classical trajectory simulations. Motivation of the work reported in this paper is the investigation of the stereodirectional dynamics of this reaction as the prominent reason for the peculiar kinetics: we started in a previous Letter ( J. Phys. Chem. Lett. 2015 , 6 , 1553 - 1558 ) a first-principles Born-Oppenheimer "canonical" molecular dynamics approach. Trajectories are step-by-step generated on a potential energy surface quantum mechanically calculated on-the-fly and are thermostatically equilibrated to correspond to a specific temperature. Here, refinements of the method permitted a major increase of the number of trajectories and the consideration of four temperatures -50, +200, +350, and +500 K, for which the sampling of initial conditions allowed us to characterize the stereodynamical effect. The role is documented of the adjustment of the reactants' mutual orientation to encounter the entrance into the "cone of acceptance" for reactivity. The aperture angle of this cone is dictated by a range of directions of approach compatible with the formation of the specific HOH angle of the product water molecule; and consistently the adjustment is progressively less effective the higher the kinetic energy. Qualitatively, this emerging picture corroborates experiments on this reaction, involving collisions of aligned and oriented molecular beams, and covering a range of energies higher than the thermal ones. The extraction of thermal rate constants from this molecular dynamics approach is discussed and the systematic sampling of the canonical ensemble is indicated as needed for quantitative comparison with the kinetic experiments.
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Affiliation(s)
- Nayara D Coutinho
- Instituto de Química, Universidade de Brasília , 4478, 70904-970 Brasília, Brazil
| | - Vincenzo Aquilanti
- Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia , Via Elce di Sotto 8, 06123, Perugia, Italy.,Instituto de Física, Universidade Federal da Bahia , 40210 Salvador, Brazil.,Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche , 00016 Rome, Italy
| | - Valter H C Silva
- Grupo de Química Teórica e Estrutural de Anápolis, Ciências Exatas e Tecnológicas, Universidade Estadual de Goiás , 0459, 75001-970 Anápolis, GO Brazil
| | - Ademir J Camargo
- Grupo de Química Teórica e Estrutural de Anápolis, Ciências Exatas e Tecnológicas, Universidade Estadual de Goiás , 0459, 75001-970 Anápolis, GO Brazil
| | - Kleber C Mundim
- Instituto de Química, Universidade de Brasília , 4478, 70904-970 Brasília, Brazil
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16
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Lombardi A, Palazzetti F, Aquilanti V, Li HK, Tsai PY, Kasai T, Lin KC. Rovibrationally Excited Molecules on the Verge of a Triple Breakdown: Molecular and Roaming Mechanisms in the Photodecomposition of Methyl Formate. J Phys Chem A 2016; 120:5155-62. [DOI: 10.1021/acs.jpca.6b00723] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Andrea Lombardi
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce
di Sotto 8, 06123 Perugia, Italy
| | - Federico Palazzetti
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce
di Sotto 8, 06123 Perugia, Italy
| | - Vincenzo Aquilanti
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce
di Sotto 8, 06123 Perugia, Italy
- Istituto
di Struttura della Materia, Consiglio Nazionale delle Ricerche, Rome, Italy
- Instituto
de Fisica, Universidade Federal da Bahia, Salvador, Brazil
| | - Hou-Kuan Li
- Department
of Chemistry, National Taiwan University, Taipei 106, Taiwan
| | - Po-Yu Tsai
- Department
of Chemistry, National Taiwan University, Taipei 106, Taiwan
| | - Toshio Kasai
- Department
of Chemistry, National Taiwan University, Taipei 106, Taiwan
| | - King-Chuen Lin
- Department
of Chemistry, National Taiwan University, Taipei 106, Taiwan
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17
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Nakamura M, Tsai PY, Kasai T, Lin KC, Palazzetti F, Lombardi A, Aquilanti V. Dynamical, spectroscopic and computational imaging of bond breaking in photodissociation: roaming and role of conical intersections. Faraday Discuss 2015; 177:77-98. [PMID: 25625792 DOI: 10.1039/c4fd00174e] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Recent experimental and theoretical advances in the study of the dissociation of excited molecules are revealing unexpected mechanisms, when their outcomes are tackled by combining (i) space-time ion imaging of translational features, with (ii) spectroscopic probing of rotational and vibrational distributions; crucial is the assistance of (iii) the quantum chemistry of structural investigations of rearrangements of chemical bonds, and of (iv) the simulations of molecular dynamics to follow the evolution of selective bond stretching and breaking. Here we present results of such an integrated approach to methyl formate, HCOOCH3, the simplest of esters; the main focus is on the rotovibrationally excited CO (v=1) product and in general on the energy distribution in the fragments. Previous laser studies of dissociation into CO and CH3OH at a sequence of various wavelengths discovered signatures of a roaming mechanism by the late arrival of CO (v=0) products in time-of-flight ion imaging. Subsequent detailed investigations as a function of excitation energy provided the assessment of the threshold, which opens for triple breakdown into CO and further fragments H and CH3O, as spectroscopically characterized by ion imaging and FTIR respectively. Accompanying quantum mechanical electronic structure calculations and classical molecular dynamics simulations clarify the origin of these fragments through "roaming" pathways involving incipient radical intermediates at energies below the triple fragmentation threshold: a specific role is played by nonadiabatic transitions at a conical intersection between ground and excited states; alternative pathways focalize our attention to regions of the potential energy surfaces other than those in the neighbourhoods of saddle points along minimum energy paths: eventually this leads us to look for avenues in reaction kinetics beyond those of venerable transition state theories.
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Affiliation(s)
- Masaaki Nakamura
- Department of Chemistry, National Taiwan University, Taipei 106, Taiwan.
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18
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Coutinho ND, Silva VHC, de Oliveira HCB, Camargo AJ, Mundim KC, Aquilanti V. Stereodynamical Origin of Anti-Arrhenius Kinetics: Negative Activation Energy and Roaming for a Four-Atom Reaction. J Phys Chem Lett 2015; 6:1553-8. [PMID: 26263312 DOI: 10.1021/acs.jpclett.5b00384] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The OH + HBr → H2O + Br reaction, prototypical of halogen-atom liberating processes relevant to mechanisms for atmospheric ozone destruction, attracted frequent attention of experimental chemical kinetics: the nature of the unusual reactivity drop from low to high temperatures eluded a variety of theoretical efforts, ranking this one among the most studied four-atom reactions. Here, inspired by oriented molecular-beams experiments, we develop a first-principles stereodynamical approach. Thermalized sets of trajectories, evolving on a multidimensional potential energy surface quantum mechanically generated on-the-fly, provide a map of most visited regions at each temperature. Visualizations of rearrangements of bonds along trajectories and of the role of specific angles of reactants' mutual approach elucidate the mechanistic change from the low kinetic energy regime (where incident reactants reorient to find the propitious alignment leading to reaction) to high temperature (where speed hinders adjustment of directionality and roaming delays reactivity).
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Affiliation(s)
- Nayara D Coutinho
- †Unidade Universitária de Ciências Exatas e Tecnológicas, 75001-970, Anápolis, and Unidade de Ipameri, Ipameri, Universidade Estadual de Goiás, 75780-000 Goiás, Brazil
- ‡Instituto de Química, Universidade de Brasília, Caixa Postal 4478, 70904-970 Brasília, Brazil
| | - Valter H C Silva
- †Unidade Universitária de Ciências Exatas e Tecnológicas, 75001-970, Anápolis, and Unidade de Ipameri, Ipameri, Universidade Estadual de Goiás, 75780-000 Goiás, Brazil
| | - Heibbe C B de Oliveira
- ‡Instituto de Química, Universidade de Brasília, Caixa Postal 4478, 70904-970 Brasília, Brazil
| | - Ademir J Camargo
- †Unidade Universitária de Ciências Exatas e Tecnológicas, 75001-970, Anápolis, and Unidade de Ipameri, Ipameri, Universidade Estadual de Goiás, 75780-000 Goiás, Brazil
| | - Kleber C Mundim
- ‡Instituto de Química, Universidade de Brasília, Caixa Postal 4478, 70904-970 Brasília, Brazil
| | - Vincenzo Aquilanti
- §Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy
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