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Kranabetter L, Kristensen HH, Ghazaryan A, Schouder CA, Chatterley AS, Janssen P, Jensen F, Zillich RE, Lemeshko M, Stapelfeldt H. Nonadiabatic Laser-Induced Alignment Dynamics of Molecules on a Surface. PHYSICAL REVIEW LETTERS 2023; 131:053201. [PMID: 37595218 DOI: 10.1103/physrevlett.131.053201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Accepted: 07/08/2023] [Indexed: 08/20/2023]
Abstract
We demonstrate that a sodium dimer, Na_{2}(1^{3}Σ_{u}^{+}), residing on the surface of a helium nanodroplet, can be set into rotation by a nonresonant 1.0 ps infrared laser pulse. The time-dependent degree of alignment measured, exhibits a periodic, gradually decreasing structure that deviates qualitatively from that expected for gas-phase dimers. Comparison to alignment dynamics calculated from the time-dependent rotational Schrödinger equation shows that the deviation is due to the alignment dependent interaction between the dimer and the droplet surface. This interaction confines the dimer to the tangential plane of the droplet surface at the point where it resides and is the reason that the observed alignment dynamics is also well described by a 2D quantum rotor model.
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Affiliation(s)
- Lorenz Kranabetter
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Henrik H Kristensen
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
| | - Areg Ghazaryan
- Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria
| | - Constant A Schouder
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
- Université Paris-Saclay, CEA, CNRS, LIDYL, 91191 Gif-sur-Yvette, France
| | - Adam S Chatterley
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
| | - Paul Janssen
- Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
| | - Frank Jensen
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Robert E Zillich
- Institute for Theoretical Physics, Johannes Kepler Universität Linz, Altenbergerstraße 69, A-4040 Linz, Austria
| | - Mikhail Lemeshko
- Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria
| | - Henrik Stapelfeldt
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
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2
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Karachi SS, Eskandari K. Bonding in the high spin lithium clusters: Non-nuclear attractors play a crucial role. J Comput Chem 2023; 44:962-968. [PMID: 36573786 DOI: 10.1002/jcc.27056] [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: 09/07/2022] [Revised: 11/29/2022] [Accepted: 12/01/2022] [Indexed: 12/28/2022]
Abstract
The bonding in lithium high-spin clusters contradicts the usual chemical bonding concept since there are no electron pairs between the atoms, and they are bound with parallel spin electrons. Quantum theory of atoms in molecules and interacting quantum atom analysis (IQA) were used to investigate the nature of bonding in the high-spin Li n n + 1 n = 2 - 5 clusters. Our findings demonstrate that the non-nuclear attractors (NNAs) are an essential component of the high-spin lithium clusters and play a key role in keeping them stable. Based on IQA energy terms, an electrostatic destabilizing interaction between the lithium atoms works against the cluster formation. On the other hand, the interactions between lithium atoms and NNA basins are stabilizing and outweigh the lithium-lithium destabilizing effects. In fact, NNAs tend to draw lithium atoms together and stabilize the resulting cluster. The high-spin clusters of lithium can be regarded as electrostatically driven compounds since the electrostatic components are primarily responsible for the stabilizing interactions between NNAs and Li atoms. The only exception is 3 Li2 , which lacks NNA and has a non-repellent lithium-lithium interaction. Indeed, in the 3 Li2 , the interatomic electrostatic component is negligibly small, and the exchange-correlation term leads to a weak bonding interaction.
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Affiliation(s)
- Sara Sadat Karachi
- Department of Chemistry, Isfahan University of Technology, Isfahan, Iran
| | - Kiamars Eskandari
- Department of Chemistry, Isfahan University of Technology, Isfahan, Iran
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3
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Kristensen HH, Kranabetter L, Schouder CA, Stapper C, Arlt J, Mudrich M, Stapelfeldt H. Quantum-State-Sensitive Detection of Alkali Dimers on Helium Nanodroplets by Laser-Induced Coulomb Explosion. PHYSICAL REVIEW LETTERS 2022; 128:093201. [PMID: 35302820 DOI: 10.1103/physrevlett.128.093201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 01/21/2022] [Accepted: 02/10/2022] [Indexed: 06/14/2023]
Abstract
Rubidium dimers residing on the surface of He nanodroplets are doubly ionized by an intense femtosecond laser pulse leading to fragmentation into a pair of Rb^{+} ions. We show that the kinetic energy of the Rb^{+} fragment ions can be used to identify dimers formed in either the X ^{1}Σ_{g}^{+} ground state or in the lowest-lying triplet state, a ^{3}Σ_{u}^{+}. From the experiment, we estimate the abundance ratio of dimers in the a and X states as a function of the mean droplet size and find values between 4∶1 and 5∶1. Our technique applies generally to dimers and trimers of alkali atoms, here also demonstrated for Li_{2}, Na_{2}, and K_{2}, and will enable femtosecond time-resolved measurements of their rotational and vibrational dynamics, possibly with atomic structural resolution.
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Affiliation(s)
- Henrik H Kristensen
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
| | - Lorenz Kranabetter
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Constant A Schouder
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Christoph Stapper
- Faculty of Chemistry and Pharmacy, University of Würzburg, Am Hubland, Campus Süd, D-97074 Würzburg, Germany
| | - Jacqueline Arlt
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Marcel Mudrich
- Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
| | - Henrik Stapelfeldt
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
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4
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A Path Integral Molecular Dynamics Simulation of a Harpoon-Type Redox Reaction in a Helium Nanodroplet. Molecules 2021; 26:molecules26195783. [PMID: 34641327 PMCID: PMC8510490 DOI: 10.3390/molecules26195783] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 09/14/2021] [Accepted: 09/21/2021] [Indexed: 11/17/2022] Open
Abstract
We present path integral molecular dynamics (PIMD) calculations of an electron transfer from a heliophobic Cs2 dimer in its (3Σu) state, located on the surface of a He droplet, to a heliophilic, fully immersed C60 molecule. Supported by electron ionization mass spectroscopy measurements (Renzler et al., J. Chem. Phys.2016, 145, 181101), this spatially quenched reaction was characterized as a harpoon-type or long-range electron transfer in a previous high-level ab initio study (de Lara-Castells et al., J. Phys. Chem. Lett.2017, 8, 4284). To go beyond the static approach, classical and quantum PIMD simulations are performed at 2 K, slightly below the critical temperature for helium superfluidity (2.172 K). Calculations are executed in the NVT ensemble as well as the NVE ensemble to provide insights into real-time dynamics. A droplet size of 2090 atoms is assumed to study the impact of spatial hindrance on reactivity. By changing the number of beads in the PIMD simulations, the impact of quantization can be studied in greater detail and without an implicit assumption of superfluidity. We find that the reaction probability increases with higher levels of quantization. Our findings confirm earlier, static predictions of a rotational motion of the Cs2 dimer upon reacting with the fullerene, involving a substantial displacement of helium. However, it also raises the new question of whether the interacting species are driven out-of-equilibrium after impurity uptake, since reactivity is strongly quenched if a full thermal equilibration is assumed. More generally, our work points towards a novel mechanism for long-range electron transfer through an interplay between nuclear quantum delocalization within the confining medium and delocalized electronic dispersion forces acting on the two reactants.
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5
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Lackner F, Ernst WE. Photoinduced Molecule Formation of Spatially Separated Atoms on Helium Nanodroplets. J Phys Chem Lett 2018; 9:3561-3566. [PMID: 29893573 DOI: 10.1021/acs.jpclett.8b01530] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Besides the use as cold matrix for spectroscopic studies, superfluid helium droplets have served as a cold environment for the synthesis of molecules and clusters. Since vibrational frequencies of molecules in helium droplets exhibit almost no shift compared to the free molecule values, one could assume the solvated particles move frictionless and undergo a reaction as soon as their paths cross. There have been a few unexplained observations that seemed to indicate cases of two species on one droplet not forming bonds but remaining isolated. In this work, we performed a systematic study of helium droplets doped with one rubidium and one strontium atom showing that besides a reaction to RbSr, there is a probability of finding separated Rb and Sr atoms on one droplet that only react after electronic excitation. Our results further indicate that ground-state Sr atoms can reside at the surface as well as inside the droplet.
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Affiliation(s)
- Florian Lackner
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria, European Union
| | - Wolfgang E Ernst
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria, European Union
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6
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Abstract
As we approach the Lewis model centennial, it may be timely to discuss novel bonding motifs. Accordingly, this review discusses no-pair ferromagnetic (NPFM) bonds that hold together monovalent metallic atoms using exclusively parallel spins. Thus, without any traditional electron-pair bonds, the bonding energy per atom in these clusters can reach 20 kcal mol(-1). This review describes the origins of NPFM bonding using a valence bond (VB) analysis, which shows that this bonding motif arises from bound triplet electron pairs that are delocalized over all the close neighbors of a given atom in the cluster. The VB model accounts for the tendency of NPFM clusters to assume polyhedral shapes with rather high symmetry and for the very steep rise of the bonding energy per atom. The advent of NPFM clusters offers new horizons in chemistry of highly magnetic species sensitive to magnetic and electric fields.
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Affiliation(s)
- David Danovich
- Institute of Chemistry, The Hebrew University, 91904 Jerusalem, Israel; ,
| | - Sason Shaik
- Institute of Chemistry, The Hebrew University, 91904 Jerusalem, Israel; ,
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7
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Rodríguez-Cantano R, González-Lezana T, Villarreal P. Path integral Monte Carlo investigations on doped helium clusters. INT REV PHYS CHEM 2016. [DOI: 10.1080/0144235x.2015.1132595] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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8
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Rodríguez-Cantano R, González-Lezana T, Prosmiti R, Delgado-Barrio G, Villarreal P, Jellinek J. Reactive scattering calculations for (87)Rb+(87)RbHe→Rb2((3)Σ(u)(+),v)+He from ultralow to intermediate energies. J Chem Phys 2015; 142:164304. [PMID: 25933761 DOI: 10.1063/1.4919062] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigate atom-diatom reactive collisions, as a preliminary step,in order to assess the possibility of forming Rb(2) molecules in their lowest triplet electronic state by cold collisions of rubidium atoms on the surface of helium nanodroplets [corrected]. A simple model related to the well-known Rosen treatment of linear triatomic molecules [N. Rosen, J. Chem. Phys. 1, 319 (1933)] in relative coordinates is used, allowing to estimate reactive probabilities for different values of the total angular momentum. The best available full dimensional potential energy surface [Guillon et al., J. Chem. Phys. 136, 174307 (2012)] is employed through the calculations. Noticeable values of the probabilities in the ultracold regime, which numerically fulfill the Wigner threshold law, support the feasibility of the process. The rubidium dimer is mainly produced at high vibrational states, and the reactivity is more efficient for a bosonic helium partner than when the fermion species is considered.
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Affiliation(s)
| | | | - Rita Prosmiti
- Instituto de Física Fundamental, IFF-CSIC, Serrano 123, 28006 Madrid, Spain
| | | | - Pablo Villarreal
- Instituto de Física Fundamental, IFF-CSIC, Serrano 123, 28006 Madrid, Spain
| | - Julius Jellinek
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
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9
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Viel A, Launay JM. Low-temperature rate coefficients for vibrational relaxation of (3)Σ(u)(+)Rb2 molecules by (3)He and (4)He atoms. J Phys Chem A 2014; 118:6529-35. [PMID: 24839871 DOI: 10.1021/jp503086b] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We present quantum-scattering calculations of (4)He and (3)He colliding with (87)Rb2. For both helium isotopes, the elastic and inelastic rate coefficients are strongly influenced by the J = 1 partial wave. For the lighter isotope, a strong resonance feature of the J = 1 partial wave is responsible for an extremely efficient vibrational relaxation process. We also perform bound-state calculations of the Rb2He complex for even Rb permutation symmetry and nonzero total angular momentum. The global Rb2He (3)Σu(+) potential-energy surface used supports four bound states for (4)He and a single one for (3)He. We propose an analysis of the (87)Rb2(4)He spectrum separating the contributions of Rb2 rotation and helium motion.
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Affiliation(s)
- Alexandra Viel
- Institut de Physique de Rennes , UMR 6251 CNRS & Université de Rennes 1, 263 av. du Général Leclerc, F-35042 Rennes, France
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10
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Danovich D, Shaik S. Bonding with parallel spins: high-spin clusters of monovalent metal atoms. Acc Chem Res 2014; 47:417-26. [PMID: 23941238 DOI: 10.1021/ar4001422] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Bonding is a glue of chemical matter and is also a useful concept for designing new molecules. Despite the fact that electron pairing remains the bonding mechanism in the great majority of molecules, in the past few decades scientists have had a growing interest in discovering novel bonding motifs. As this Account shows, monovalent metallic atoms having exclusively parallel spins, such as (11)Li10, (11)Au10, and (11)Cu10, can nevertheless form strongly bound clusters, without having even one traditional bond due to electron pairing. These clusters, which also can be made chiral, have high magnetic moments. We refer to this type as no-pair ferromagnetic (NPFM) bonding, which characterizes the (n+1)Mn clusters, which were all predicted by theoretical computations. The small NPFM alkali clusters that have been "synthesized" to date, using cold-atom techniques, support the computational predictions. In this Account, we describe the origins of NPFM bonding using a valence bond (VB) analysis, which shows that this bonding motif arises from bound triplet electron pairs that spread over all the close neighbors of a given atom in the cluster. The bound triplet pair owes its stabilization to the resonance energy provided by the mixing of the local ionic configurations, [(3)M(↑↑)(-)]M(+) and M(+)[(3)M(↑↑)(-)], and the various excited covalent configurations (involving pz and dz(2) atomic orbitals) into the repulsive covalent structure (3)(M↑↑M) with the s(1)s(1) electronic configuration. The NPFM bond of the bound triplet is described by a resonating wave function with "in-out" and "out-in" pointing hybrids. The VB model accounts for the tendency of NPFM clusters to assume polyhedral shapes with rather high symmetry. In addition, this model explains the very steep rise of the bonding energy per atom (De/n), which starts out small in the (3)M2 dimer (<1 kcal/mol) and reaches 12-19 kcal/mol for clusters with 10 atoms. The model further predicts that usage of heteroatomic clusters should increase the bonding energy of an NPFM cluster. These NPFM clusters are excited state species. We suggest here stabilizing these states and making them accessible, for example, by using magnetic fields, or a combination of magnetic and electric fields. The advent of NPFM clusters offers new horizons in chemistry and enriches the scope of chemical bonding. These prospects form a strong incentive to investigate the origins of the bound triplet pairs and further chart the territory of NPFM clusters, for example, in clusters of Be, Mg, or Zn, possibly in clusters of their monosubstituted species, and the group III metalloids, such as B, Al, as well as in transition metals such as Sc.
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Affiliation(s)
- David Danovich
- Institute of Chemistry and the Lise-Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Sason Shaik
- Institute of Chemistry and the Lise-Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
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11
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Krois G, Pototschnig JV, Lackner F, Ernst WE. Spectroscopy of cold LiCa molecules formed on helium nanodroplets. J Phys Chem A 2013; 117:13719-31. [PMID: 24028555 PMCID: PMC3871282 DOI: 10.1021/jp407818k] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 09/11/2013] [Indexed: 11/30/2022]
Abstract
We report on the formation of mixed alkali-alkaline earth molecules (LiCa) on helium nanodroplets and present a comprehensive experimental and theoretical study of the ground and excited states of LiCa. Resonance enhanced multiphoton ionization time-of-flight (REMPI-TOF) spectroscopy and laser induced fluorescence (LIF) spectroscopy were used for the experimental investigation of LiCa from 15000 to 25500 cm(-1). The 4(2)Σ(+) and 3(2)Π states show a vibrational structure accompanied by distinct phonon wings, which allows us to determine molecular parameters as well as to study the interaction of the molecule with the helium droplet. Higher excited states (4(2)Π, 5(2)Σ(+), 5(2)Π, and 6(2)Σ(+)) are not vibrationally resolved and vibronic transitions start to overlap. The experimental spectrum is well reproduced by high-level ab initio calculations. By using a multireference configuration interaction (MRCI) approach, we calculated the 19 lowest lying potential energy curves (PECs) of the LiCa molecule. On the basis of these calculations, we could identify previously unobserved transitions. Our results demonstrate that the helium droplet isolation approach is a powerful method for the characterization of tailor-made alkali-alkaline earth molecules. In this way, important contributions can be made to the search for optimal pathways toward the creation of ultracold alkali-alkaline earth ground state molecules from the corresponding atomic species. Furthermore, a test for PECs calculated by ab initio methods is provided.
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Affiliation(s)
- Günter Krois
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Johann V. Pototschnig
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Florian Lackner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Wolfgang E. Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
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12
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Lackner F, Poms J, Krois G, Pototschnig JV, Ernst WE. Spectroscopy of lithium atoms and molecules on helium nanodroplets. J Phys Chem A 2013; 117:11866-73. [PMID: 23895106 PMCID: PMC3839407 DOI: 10.1021/jp4030238] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
We
report on the spectroscopic investigation of lithium atoms and
lithium dimers in their triplet manifold on the surface of helium
nanodroplets (HeN). We present the excitation spectrum
of the 3p ← 2s and 3d ← 2s two-photon transitions for
single Li atoms on HeN. The atoms are excited from the
2S(Σ) ground state into Δ, Π, and Σ pseudodiatomic
molecular substates. Excitation spectra are recorded by resonance
enhanced multiphoton ionization time-of-flight (REMPI-TOF) mass spectroscopy,
which allows an investigation of the exciplex (Li*–Hem, m = 1–3) formation process
in the Li–HeN system. Electronic states are shifted
and broadened with respect to free atom states, which is explained
within the pseudodiatomic model. The assignment is assisted by theoretical
calculations, which are based on the Orsay–Trento density functional
where the interaction between the helium droplet and the lithium atom
is introduced by a pairwise additive approach. When a droplet is doped
with more than one alkali atom, the fragility of the alkali–HeN systems leads preferably to the formation of high-spin molecules
on the droplets. We use this property of helium nanodroplets for the
preparation of Li dimers in their triplet ground state (13Σu+).
The excitation spectrum of the 23Πg(ν′
= 0–11) ← 13Σu+(ν″ = 0) transition is presented.
The interaction between the molecule and the droplet manifests in
a broadening of the transitions with a characteristic asymmetric form.
The broadening extends to the blue side of each vibronic level, which
is caused by the simultaneous excitation of the molecule and vibrations
of the droplet (phonons). The two isotopes of Li form 6Li2 and 7Li2 as well as isotope
mixed 6Li7Li molecules on the droplet surface.
By using REMPI-TOF mass spectroscopy, isotope-dependent effects could
be studied.
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Affiliation(s)
- Florian Lackner
- Institute of Experimental Physics, Graz University of Technology , Petersgasse 16, A-8010 Graz, Austria/EU
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13
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Guillon G, Viel A, Launay JM. Full dimension Rb2He ground triplet potential energy surface and quantum scattering calculations. J Chem Phys 2012; 136:174307. [DOI: 10.1063/1.4709433] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
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14
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Verdicchio M, Evangelisti S, Leininger T, Monari A. On the triplet ground state of tetrahedral X4 clusters (X = Li, Na, K, Cu). J Chem Phys 2012; 136:094301. [DOI: 10.1063/1.3687907] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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15
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Giese C, Stienkemeier F, Mudrich M, Hauser AW, Ernst WE. Homo- and heteronuclear alkali metal trimers formed on helium nanodroplets. Part II. Femtosecond spectroscopy and spectra assignments. Phys Chem Chem Phys 2011; 13:18769-80. [PMID: 21869967 DOI: 10.1039/c1cp21191a] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Homo- and heteronuclear alkali quartet trimers of type K(3-n)Rb(n) (n = 0,1,2,3) formed on helium nanodroplets are probed by one-color femtosecond (fs) photoionization (PI) spectroscopy. The obtained frequencies are assigned to vibrations in different electronic states in comparison to high level ab initio calculations of the involved potentials including pronounced Jahn-Teller and spin-orbit couplings. Despite the fact that the resulting complex vibronic structure of the heavy alkali molecules complicates the comparison of experiment and theory we find good agreement for many of the observed lines for all species.
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Affiliation(s)
- Christian Giese
- Physikalisches Institut, Universität Freiburg, 79104 Freiburg, Germany.
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16
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Guillon G, Zanchet A, Leino M, Viel A, Zillich RE. Theoretical Study of Rb2 in HeN: Potential Energy Surface and Monte Carlo Simulations. J Phys Chem A 2011; 115:6918-26. [DOI: 10.1021/jp112053b] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Grégroire Guillon
- Institut de Physique de Rennes, UMR 6251, CNRS & Université de Rennes I, F-35042 Rennes, France
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18
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Danovich D, Shaik S. Bound Triplet Pairs in the Highest Spin States of Coinage Metal Clusters. J Chem Theory Comput 2010; 6:1479-89. [DOI: 10.1021/ct100088u] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- David Danovich
- The Institute of Chemistry and The Lise-Meitner Minerva Center for Computational Quantum Chemistry, The Hebrew University, Jerusalem 91904, Israel
| | - Sason Shaik
- The Institute of Chemistry and The Lise-Meitner Minerva Center for Computational Quantum Chemistry, The Hebrew University, Jerusalem 91904, Israel
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Auböck G, Aymar M, Dulieu O, Ernst WE. Reinvestigation of the Rb2 (2)Π3g−a Σ3u+ band on helium nanodroplets. J Chem Phys 2010; 132:054304. [DOI: 10.1063/1.3308493] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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20
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Affiliation(s)
- David Danovich
- The Lise-Meitner Minerva Center for Computational Quantum Chemistry, The Hebrew University, Jerusalem 91904, Israel
| | - Michael Filatov
- Theoretical Chemistry, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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Nagl J, Auböck G, Hauser AW, Allard O, Callegari C, Ernst WE. High-spin alkali trimers on helium nanodroplets: Spectral separation and analysis. J Chem Phys 2008; 128:154320. [DOI: 10.1063/1.2906120] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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22
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Nagl J, Auböck G, Hauser AW, Allard O, Callegari C, Ernst WE. Heteronuclear and homonuclear high-spin alkali trimers on helium nanodroplets. PHYSICAL REVIEW LETTERS 2008; 100:063001. [PMID: 18352466 DOI: 10.1103/physrevlett.100.063001] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2007] [Indexed: 05/26/2023]
Abstract
The electronic excitation spectra of all possible homo- and heteronuclear high-spin (quartet) trimers of K and Rb (KxRb(3-x), x=0...3) assembled on the surface of superfluid helium droplets, are measured in the spectral range from 10,600 to 17,400 cm(-1). A regular series of corresponding bands is observed, reflecting the similar electronic structure of all these trimers. For the assignment and separation of overlapping bands, we determine x directly, with mass-selected beam depletion, and indirectly with a V-type double-resonance scheme. The assignment is confirmed by high-level ab initio calculations of the electronic structure of the bare trimers. The level structure is rationalized in terms of harmonic-oscillator states of the three valence electrons in a quantum-dot-like confining potential. We predict that three should be a magic number for high-spin alkali clusters.
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Affiliation(s)
- Johann Nagl
- Institute of Experimental Physics, TU Graz, Petersgasse 16, A-8010 Graz, Austria, EU
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Auböck G, Nagl J, Callegari C, Ernst WE. Triplet State Excitation of Alkali Molecules on Helium Droplets: Experiments and Theory. J Phys Chem A 2007; 111:7404-10. [PMID: 17552501 DOI: 10.1021/jp070891y] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this paper, we discuss the electronic structure of alkali dimer molecules in 3Pig states on the surface of a helium droplet. The perturbation due to the droplet will in general not satisfy rotational symmetry around the internuclear axis of the diatom and thus, in addition to a broadening and blue shift, will cause a splitting of electronic levels that are degenerate in the free molecules. We propose a model based on general symmetry arguments and on a small number of physically reasonable parameters. We demonstrate that such a model accounts for the essential features of laser-induced fluorescence (LIF) and magnetic circular dichroism (MCD) spectra of the (1)3Pig-a3Sigma+ transition of Rb2 and K2. Furthermore the MCD spectra, analyzed according to the approach of Langford and Williamson [J. Phys. Chem. A 1998, 102, 2415], allow a determination of the populations of Zeeman sublevels in the ground state and thus a measurement of the surface temperature of the droplet. The latter agrees with the accepted temperature, 0.37 K, measured in the interior of a droplet.
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Affiliation(s)
- Gerald Auböck
- Institute of Experimental Physics, TU Graz, Petersgasse 16, 8010 Graz, Austria, EU
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de Visser SP, Kumar D, Danovich M, Nevo N, Danovich D, Sharma PK, Wu W, Shaik S. Ferromagnetic Bonding: High Spin Copper Clusters (n+1Cun; n = 2−14) Devoid of Electron Pairs but Possessing Strong Bonding. J Phys Chem A 2006; 110:8510-8. [PMID: 16821835 DOI: 10.1021/jp055125a] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Density functional theoretic studies are performed for the high-spin copper clusters (n)(+1)Cu(n) (n = 2-14), which are devoid of electron pairs shared between atoms, hence no-pair clusters (J. Phys. Chem. 1988, 92, 1352; Isr. J. Chem. 1993, 33, 455; J. Am. Chem. Soc. 1999, 121, 3165). Despite the lack of electron pairing, it is found that the bond dissociation energy per atom (BDE/n) is significant and converges (to within 1 kcal mol(-1)), around a cluster size (11)Cu(10), to a value of BDE/n = 19 kcal mol(-1). This is a very large bonding energy, much larger than has previously been obtained for no-pair clusters of lithium, BDE/n = 12 kcal mol(-1), or sodium clusters, BDE/n = 3 kcal mol(-1). This bonding, so-called ferromagnetic bonding (FM-bonding) is analyzed using a valence bond (VB) model (J. Phys. Chem. A 2002, 106, 4961; Phys. Chem. Chem. Phys. 2003, 5, 158). As such, FM-bonding in no-pair clusters is described as an ionic fluctuation, of the triplet pair, that spreads over all the close neighbors of a given atom in the clusters. Thus, if we refer to each triplet pair and its ionic fluctuations as a local FM-bond, we can regard the electronic structure of a given (n)(+1)M(n) cluster as a resonance hybrid of all the local FM-bonds between close neighbors. The model shows how a weak interaction in the diatomic triplet molecule can become a remarkably strong binding force that binds together mono-valent atoms without even a single electron pair. This is achieved because the growing number of VB structures exerts a cumulative effect of stabilization that is maximized when the cluster has a compact structure with an optimal coordination number for the atoms.
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Affiliation(s)
- Sam P de Visser
- The Manchester Interdisciplinary Biocenter, School of Chemical Engineering and Analytical Science, The University of Manchester, Sackville Street, PO Box 88, Manchester M60 1QD, UK
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Alikhani ME, Shaik S. A Topological Study of the Ferromagnetic “No-Pair Bonding” in Maximum-Spin Lithium clusters: n+1Li n (n=2–6). Theor Chem Acc 2006. [DOI: 10.1007/s00214-006-0081-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Ernst WE, Huber R, Jiang S, Beuc R, Movre M, Pichler G. Cesium dimer spectroscopy on helium droplets. J Chem Phys 2006; 124:024313. [PMID: 16422589 DOI: 10.1063/1.2155431] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Visible absorption spectra of cesium-doped helium nanodroplets between 14,500 and 17,600 cm(-1) were probed by laser-induced fluorescence. A strong absorption band peaking around 16,700 cm(-1) is identified as Cs2 1(a) 3Sigmau+-3 3Sigmag+ transition. A broad unstructured band near 17,520 cm(-1) is assigned as the Cs2 1(X) 1Sigmag+-2 1Sigmau+ transition. Explanations of the observations are discussed on the basis of ab initio potential curves calculated by Spies and Meyer [(unpublished)]. All spectra have been modeled using narrow Frank-Condon windows around the equilibrium internuclear distance of the lowest singlet and triplet states. Many observed absorption peaks of smaller intensities could be identified, some of which may be due to transitions of cesium trimers formed on the droplets.
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Affiliation(s)
- W E Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
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Dulieu O, Pillet P. Playing With a Pair of Ultracold Atoms and Lasers: Towards a Novel Ultracold Photochemistry? Isr J Chem 2004. [DOI: 10.1560/rhhr-c4m6-pffn-8a8j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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