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Kawamata H, Che DC, Nakamura M, Kasai T. Photodissociation Dynamics of CF 2ClCHFI Using Slice Imaging Combined with a Hexapole-Oriented Molecular Beam. J Phys Chem A 2022; 126:8844-8850. [DOI: 10.1021/acs.jpca.2c06494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- Hiroshi Kawamata
- Center for Higher Education and Global Admissions, Osaka University, Toyonaka, Osaka560-0043, Japan
| | - Dock-Chil Che
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka560-0043, Japan
| | - Masaaki Nakamura
- Department of Chemistry, School of Science, Tokyo Institute of Technology, Meguro, Tokyo152-8550, Japan
| | - Toshio Kasai
- Department of Chemistry, National Taiwan University, Taipei10617, Taiwan
- Department of Applied Physics, Osaka University, Suita, Osaka565-0871, Japan
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2
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Orientation of Chiral Molecules by External Electric Fields: Focus on Photodissociation Dynamics. Symmetry (Basel) 2022. [DOI: 10.3390/sym14102152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Molecular orientation is a fundamental requirement to study and control photoinitiated reactions. Experimental setups that make use of hexapolar electric filters combined with slice-ion imaging detectors were employed in these last years to investigate the photodissociation dynamics of chiral molecules. The final goal is the on-the-fly discrimination of oriented enantiomers, revealed by the different angular distributions in photofragment ion-imaging, as predicted from vector correlation studies. Here, we review experiments of photodissociation of oriented chiral molecules, with the aim of presenting limits emerging from these investigations and perspectives toward the achievement of the ultimate objective.
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3
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Che DC, Kawamata H, Nakamura M, Kasai T, Lin KC. A vector correlation study using a hexapole-oriented molecular beam: photodissociation dynamics of oriented isohaloethane. Phys Chem Chem Phys 2022; 24:5914-5920. [PMID: 35195628 DOI: 10.1039/d1cp05788j] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The photodissociation dynamics of isohaloethane (1-bromo-2-chloro-1,1,2-trifluoroethane) at 234 nm was studied by a sliced imaging technique combined with an oriented molecular beam. The speed and angular distributions of the competitive products of spin-orbit selected Br and Cl atoms were determined by analysis of the obtained images. The anisotropic parameter, β, was found to be 2.0 ± 0.2 for the excited state of Br(2P1/2) (Br*) and 1.2 ± 0.3 for the ground state of Br(2P3/2) (Br). The speed distributions for both Br and Br* exhibited Gaussian-like characteristics. These results indicate that Br atoms were generated by direct formation after excitation through the nσ*(C-Br) potential energy surfaces. In contrast, the angular distributions for the Cl fragments were almost isotropic, while the speed distributions displayed Boltzmann-like characteristics. This suggests that the Cl atoms may form through long-lived parent molecules after photoexcitation. The branching ratio for Br and Cl atom formation was found to be approximately 1.2, that is, Br atom formation occurred preferentially, in contrast to the case of halothane photodissociation reported in our previous work [Che et al., J. Phys. Chem. A, 2020, 124, 5288]. A vector correlation study between the laser polarization axis and the direction of the dipole moment revealed a similar tendency for all photofragments, suggesting that the fragments were formed through a common excited state of isohaloethane. The vector correlation was also studied theoretically for comparison with the experimental results. The angle between the transition dipole moment in photodissociation and the permanent dipole moment was found to be 42 ± 15°. The obtained results indicate that this vector correlation approach combined with an oriented molecular beam is a powerful tool for determining the transition dipole moments in photodissociation.
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Affiliation(s)
- Dock-Chil Che
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
| | - Hiroshi Kawamata
- Center for Higher Education and Global Admissions, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Masaaki Nakamura
- Department of Chemistry, School of Science, Tokyo Institute of Technology, Meguro, Tokyo 152-8550, Japan
| | - Toshio Kasai
- Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan.,Department of Applied Physics, Osaka University, Suita, Osaka 565-0871, Japan
| | - King-Chuen Lin
- Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan.,Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
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4
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Conformer Selection by Electrostatic Hexapoles: A Theoretical Study on 1-Chloroethanol and 2-Chloroethanol. Symmetry (Basel) 2022. [DOI: 10.3390/sym14020317] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/10/2022] Open
Abstract
The electrostatic hexapole is a versatile device that has been used for many years in gas-phase experiments. Its inhomogeneous electric field has been employed for many purposes such as the selection of rotational states, the selection of clusters, the focusing of molecular beams, and molecular alignment as a precursor for molecular orientation. In the last few years, the hexapolar electric field has been demonstrated to be able to control the conformer composition of molecular beams. The key point is that conformers, where the component of the permanent electric dipole moment with respect to the largest of the principal axes of inertia is close to zero, require more intense hexapolar electric fields to be focused with respect to the other conformers. Here, we simulated the focusing curves of the conformers of 1-chloroethanol and 2-chloroethanol under hypothetical beam conditions, identical for all conformers, in a hypothetical and realistic experimental setup with three different hexapole lengths: 0.5, 1, and 2 m. The objective was to characterize this selection process to set up collision experiments on conformer-selected beams that provide information on the van der Waals clusters formed in collision processes.
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5
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Che DC, Nakamura M, Chang HP, Lin KC, Kasai T, Aquilanti V, Palazzetti F. UV Photodissociation of Halothane in a Focused Molecular Beam: Space-Speed Slice Imaging of Competitive Bond Breaking into Spin-Orbit-Selected Chlorine and Bromine Atoms. J Phys Chem A 2020; 124:5288-5296. [PMID: 32498517 DOI: 10.1021/acs.jpca.0c02800] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A molecular beam of halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) is focused by a hexapolar electrostatic field and photolyzed by UV laser radiation at 234 nm. Angular and speed distributions of chlorine and bromine photofragments emitted from halothane are measured for both spin-orbit states independently. Although the dissociation energy of the C-Cl bond is larger than that of C-Br, the relative yield of Cl to Br was found to be approximately 2. Measured speed and angular distributions of atomic fragments show distinct kinetic energy release and scattering characteristics: for bromine, observed fast and aligned fragments exhibit a signature of a direct mode of dissociation for the C-Br bond, via the electronically excited potential energy surface denoted nσ*(C-Br), of repulsive nature; for chlorine, a variation in the features is observed for the dissociation pathway through nσ*(C-Cl), from a modality similar to the bromine case, leading to fragments with appreciable kinetic energy release and pronounced directionality, to a modality involving slow products, nearly isotopically distributed. The origin of this behavior can be attributed to nonadiabatic interaction operating between the nσ*(C-Br) and nσ*(C-Cl) surfaces. These results are not only relevant for a detailed understanding of adiabatic versus diabatic coupling mechanisms in the manifold of excited states populated by photon absorption, but they also point out the possibility of selectively inducing specific dissociation pathways, even when involving energetically unfavorable outcomes, such as, in this case, the prevailing rupture of the stronger C-Cl bond against that of the weaker C-Br bond.
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Affiliation(s)
- Dock-Chil Che
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - 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
| | - Vincenzo Aquilanti
- Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Perugia 06123, Italy.,Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Rome 00016, Italy
| | - Federico Palazzetti
- Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Perugia 06123, Italy
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6
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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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7
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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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8
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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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9
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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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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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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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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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13
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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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14
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Kasai T, Che DC, Okada M, Tsai PY, Lin KC, Palazzetti F, Aquilanti V. Directions of chemical change: experimental characterization of the stereodynamics of photodissociation and reactive processes. Phys Chem Chem Phys 2014; 16:9776-90. [DOI: 10.1039/c4cp00464g] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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