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Title: Velocity map imaging study of BrCl photodissociation at 467 nm: Determination of all odd-rank (K=1 and 3) anisotropy parameters for the Cl({sup 2}P{sub 3/2}{sup 0}) photofragments

Abstract

Resonance-enhanced multiphoton ionization and velocity map imaging of the Cl({sup 2}P{sub 3/2}{sup 0}) fragments of BrCl photolysis at 467.16 nm have been used to obtain a complete set of orientation parameters (with ranks K=1 and 3) describing the polarization of the electronic angular momentum. The experiments employ two geometries distinguished only by the circular or linear polarization of the photolysis laser beam. Normalized difference images constructed from the data accumulated using a right or left circularly polarized probe-laser beam, counterpropagating with the photolysis laser, were fitted to basis images corresponding to contributions from various odd-rank anisotropy parameters. Expressions are given for the difference images in terms of the K=1 and 3 anisotropy parameters, which describe coherent and incoherent parallel and perpendicular excitation and dissociation mechanisms. The nonzero values of the anisotropy parameters are indicative of nonadiabatic dissociation dynamics, with likely contributions from flux on the A {sup 3}{pi}(1),B {sup 3}{pi}(0{sup +}),C {sup 1}{pi}(1), and X {sup 1}{sigma}{sup +}(0{sup +}) states as well as one further {omega}=1 state, all of which correlate adiabatically to Cl({sup 2}P{sub 3/}0)+Br({sup 2}P{sub 3/2}{sup 0}) photofragments. The magnitudes of the parameters depend both on the amplitudes of dissociative flux in these states, and also on themore » phases accumulated by the nuclear wave functions for different dissociation pathways.« less

Authors:
; ; ; ; ;  [1];  [2]
  1. Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021 Saint Petersburg (Russian Federation)
  2. (United Kingdom)
Publication Date:
OSTI Identifier:
20783240
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 124; Journal Issue: 9; Other Information: DOI: 10.1063/1.2168149; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ANGULAR MOMENTUM; ANISOTROPY; BROMINE CHLORIDES; DISSOCIATION; LASERS; MULTI-PHOTON PROCESSES; PHOTOIONIZATION; PHOTOLYSIS; PHOTON-MOLECULE COLLISIONS; POLARIZATION; REACTION KINETICS; WAVE FUNCTIONS

Citation Formats

Smolin, Andrey G., Vasyutinskii, Oleg S., Vieuxmaire, Olivier P. J., Ashfold, Michael N.R., Balint-Kurti, Gabriel G., Orr-Ewing, Andrew J., and School of Chemistry, University of Bristol, Bristol BS8 1TS. Velocity map imaging study of BrCl photodissociation at 467 nm: Determination of all odd-rank (K=1 and 3) anisotropy parameters for the Cl({sup 2}P{sub 3/2}{sup 0}) photofragments. United States: N. p., 2006. Web. doi:10.1063/1.2168149.
Smolin, Andrey G., Vasyutinskii, Oleg S., Vieuxmaire, Olivier P. J., Ashfold, Michael N.R., Balint-Kurti, Gabriel G., Orr-Ewing, Andrew J., & School of Chemistry, University of Bristol, Bristol BS8 1TS. Velocity map imaging study of BrCl photodissociation at 467 nm: Determination of all odd-rank (K=1 and 3) anisotropy parameters for the Cl({sup 2}P{sub 3/2}{sup 0}) photofragments. United States. doi:10.1063/1.2168149.
Smolin, Andrey G., Vasyutinskii, Oleg S., Vieuxmaire, Olivier P. J., Ashfold, Michael N.R., Balint-Kurti, Gabriel G., Orr-Ewing, Andrew J., and School of Chemistry, University of Bristol, Bristol BS8 1TS. Tue . "Velocity map imaging study of BrCl photodissociation at 467 nm: Determination of all odd-rank (K=1 and 3) anisotropy parameters for the Cl({sup 2}P{sub 3/2}{sup 0}) photofragments". United States. doi:10.1063/1.2168149.
@article{osti_20783240,
title = {Velocity map imaging study of BrCl photodissociation at 467 nm: Determination of all odd-rank (K=1 and 3) anisotropy parameters for the Cl({sup 2}P{sub 3/2}{sup 0}) photofragments},
author = {Smolin, Andrey G. and Vasyutinskii, Oleg S. and Vieuxmaire, Olivier P. J. and Ashfold, Michael N.R. and Balint-Kurti, Gabriel G. and Orr-Ewing, Andrew J. and School of Chemistry, University of Bristol, Bristol BS8 1TS},
abstractNote = {Resonance-enhanced multiphoton ionization and velocity map imaging of the Cl({sup 2}P{sub 3/2}{sup 0}) fragments of BrCl photolysis at 467.16 nm have been used to obtain a complete set of orientation parameters (with ranks K=1 and 3) describing the polarization of the electronic angular momentum. The experiments employ two geometries distinguished only by the circular or linear polarization of the photolysis laser beam. Normalized difference images constructed from the data accumulated using a right or left circularly polarized probe-laser beam, counterpropagating with the photolysis laser, were fitted to basis images corresponding to contributions from various odd-rank anisotropy parameters. Expressions are given for the difference images in terms of the K=1 and 3 anisotropy parameters, which describe coherent and incoherent parallel and perpendicular excitation and dissociation mechanisms. The nonzero values of the anisotropy parameters are indicative of nonadiabatic dissociation dynamics, with likely contributions from flux on the A {sup 3}{pi}(1),B {sup 3}{pi}(0{sup +}),C {sup 1}{pi}(1), and X {sup 1}{sigma}{sup +}(0{sup +}) states as well as one further {omega}=1 state, all of which correlate adiabatically to Cl({sup 2}P{sub 3/}0)+Br({sup 2}P{sub 3/2}{sup 0}) photofragments. The magnitudes of the parameters depend both on the amplitudes of dissociative flux in these states, and also on the phases accumulated by the nuclear wave functions for different dissociation pathways.},
doi = {10.1063/1.2168149},
journal = {Journal of Chemical Physics},
number = 9,
volume = 124,
place = {United States},
year = {Tue Mar 07 00:00:00 EST 2006},
month = {Tue Mar 07 00:00:00 EST 2006}
}
  • Various electronic states of Ba, from ground state up to 2.24 eV ({sup 1}S{sub 0}, {sup 3}D{sub J}, {sup 1}D{sub 2}, {sup 3}P{sub 1}, and {sup 1}P{sub 1}) together with Ba{sup +}({sup 2}P{sub 3/2}), were produced by 1064 nm high-irradiance pulsed nanosecond laser ablation of Ba in vacuum. The velocity distribution for every species was obtained from time-of-flight measurements, using pulsed laser induced fluorescence or time-resolved optical emission spectroscopy, as applicable to each species. The distributions are bimodal, Maxwell-Boltzmann functions for {sup 1}S{sub 0}, {sup 3}D{sub J}, and {sup 1}D{sub 2} and shifted Maxwell-Boltzmann for the rest of the states,more » with different peak velocities and average, hyperthermal translational temperatures. Possible mechanisms for the production of these velocity distributions are discussed.« less
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  • These imaging experiments study the formation of the methylsulfonyl radical, CH{sub 3}SO{sub 2}, from the photodissociation of CH{sub 3}SO{sub 2}Cl at 193 nm and determine the energetic barrier for the radical's subsequent dissociation to CH{sub 3}+SO{sub 2}. We first state-selectively detect the angular and recoil velocity distributions of the Cl({sup 2}P{sub 3/2}) and Cl({sup 2}P{sub 1/2}) atoms to further refine the distribution of internal energy partitioned to the momentum-matched CH{sub 3}SO{sub 2} radicals. The internal energy distribution of the radicals is bimodal, indicating that CH{sub 3}SO{sub 2} is formed in both the ground state and low-lying excited electronic states. Allmore » electronically excited CH{sub 3}SO{sub 2} radicals dissociate, while those formed in the ground electronic state have an internal energy distribution which spans the dissociation barrier to CH{sub 3}+SO{sub 2}. We detect the recoil velocities of the energetically stable methylsulfonyl radicals with 118 nm photoionization. Comparison of the total recoil translational energy distribution for all radicals to the distribution obtained from the detection of stable radicals yields an onset for dissociation at a translational energy of 70{+-}2 kcal/mol. This onset allows us to derive a CH{sub 3}SO{sub 2}{yields}CH{sub 3}+SO{sub 2} barrier height of 14{+-}2 kcal/mol; this determination relies on the S-Cl bond dissociation energy, taken here as the CCSD(T) predicted energy of 65.6 kcal/mol. With 118 nm photoionization, we also detect the velocity distribution of the CH{sub 3} radicals produced in this experiment. Using the velocity distributions of the SO{sub 2} products from the dissociation of CH{sub 3}SO{sub 2} to CH{sub 3}+SO{sub 2} presented in the following paper, we show that our fastest detected methyl radicals are not from these radical dissociation channels, but rather from a primary S-CH{sub 3} bond photofission channel in CH{sub 3}SO{sub 2}Cl. We also present critical points on the ground state potential energy surface of CH{sub 3}SO{sub 2} at the //CCSD(T)/aug-cc-pV(Q+d)ZCCSD(T)/6-311++G(2df,p) level. We include harmonic zero-point vibrational corrections as well as core-valence and scalar-relativistic corrections. The CCSD(T) predicted barrier of 14.6 kcal/mol for CH{sub 3}SO{sub 2}{yields}CH{sub 3}+SO{sub 2} agrees well with our experimental measurement. These results allow us to predict the unimolecular dissociation kinetics of CH{sub 3}SO{sub 2} radicals and critique the analysis of prior time-resolved photoionization studies on this system.« less