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Title: High-resolution slice imaging of quantum state-to-state photodissociation of methyl bromide

Abstract

The photodissociation of rotationally state-selected methyl bromide is studied in the wavelength region between 213 and 235 nm using slice imaging. A hexapole state selector is used to focus a single (JK=11) rotational quantum state of the parent molecule, and a high speed slice imaging detector measures directly the three-dimensional recoil distribution of the methyl fragment. Experiments were performed on both normal (CH{sub 3}Br) and deuterated (CD{sub 3}Br) parent molecules. The velocity distribution of the methyl fragment shows a rich structure, especially for the CD{sub 3} photofragment, assigned to the formation of vibrationally excited methyl fragments in the {nu}{sub 1} and {nu}{sub 4} vibrational modes. The CH{sub 3} fragment formed with ground state Br({sup 2}P{sub 3/2}) is observed to be rotationally more excited, by some 230-340 cm{sup -1}, compared to the methyl fragment formed with spin-orbit excited Br({sup 2}P{sub 1/2}). Branching ratios and angular distributions are obtained for various methyl product states and they are observed to vary with photodissociation energy. The nonadiabatic transition probability for the {sup 3}Q{sub 0+}{yields}{sup 1}Q{sub 1} transition is calculated from the images and differences between the isotopes are observed. Comparison with previous non-state-selected experiments indicates an enhanced nonadiabatic transition probability for state-selected K=1 methylmore » bromide parent molecules. From the state-to-state photodissociation experiments the dissociationenergy for both isotopes was determined, D{sub 0}(CH{sub 3}Br)=23 400{+-}133 cm{sup -1} and D{sub 0}(CD{sub 3}Br)=23 827{+-}94 cm{sup -1}.« less

Authors:
;  [1]
  1. Laser Centre, Vrije Universiteit, de Boelelaan 1083, 1081 HV Amsterdam (Netherlands) and Department of Chemistry, Vrije Universiteit, de Boelelaan 1083, 1081 HV Amsterdam (Netherlands)
Publication Date:
OSTI Identifier:
21024605
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 127; Journal Issue: 22; Other Information: DOI: 10.1063/1.2813350; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ANGULAR DISTRIBUTION; BRANCHING RATIO; DISSOCIATION; DISSOCIATION ENERGY; GROUND STATES; HEXAPOLES; ISOTOPE EFFECTS; ISOTOPES; L-S COUPLING; METHYL BROMIDE; PHOTOLYSIS; PHOTON-MOLECULE COLLISIONS; PROBABILITY; SPIN

Citation Formats

Lipciuc, M Laura, and Janssen, Maurice H. M.. High-resolution slice imaging of quantum state-to-state photodissociation of methyl bromide. United States: N. p., 2007. Web. doi:10.1063/1.2813350.
Lipciuc, M Laura, & Janssen, Maurice H. M.. High-resolution slice imaging of quantum state-to-state photodissociation of methyl bromide. United States. https://doi.org/10.1063/1.2813350
Lipciuc, M Laura, and Janssen, Maurice H. M.. Fri . "High-resolution slice imaging of quantum state-to-state photodissociation of methyl bromide". United States. https://doi.org/10.1063/1.2813350.
@article{osti_21024605,
title = {High-resolution slice imaging of quantum state-to-state photodissociation of methyl bromide},
author = {Lipciuc, M Laura and Janssen, Maurice H. M.},
abstractNote = {The photodissociation of rotationally state-selected methyl bromide is studied in the wavelength region between 213 and 235 nm using slice imaging. A hexapole state selector is used to focus a single (JK=11) rotational quantum state of the parent molecule, and a high speed slice imaging detector measures directly the three-dimensional recoil distribution of the methyl fragment. Experiments were performed on both normal (CH{sub 3}Br) and deuterated (CD{sub 3}Br) parent molecules. The velocity distribution of the methyl fragment shows a rich structure, especially for the CD{sub 3} photofragment, assigned to the formation of vibrationally excited methyl fragments in the {nu}{sub 1} and {nu}{sub 4} vibrational modes. The CH{sub 3} fragment formed with ground state Br({sup 2}P{sub 3/2}) is observed to be rotationally more excited, by some 230-340 cm{sup -1}, compared to the methyl fragment formed with spin-orbit excited Br({sup 2}P{sub 1/2}). Branching ratios and angular distributions are obtained for various methyl product states and they are observed to vary with photodissociation energy. The nonadiabatic transition probability for the {sup 3}Q{sub 0+}{yields}{sup 1}Q{sub 1} transition is calculated from the images and differences between the isotopes are observed. Comparison with previous non-state-selected experiments indicates an enhanced nonadiabatic transition probability for state-selected K=1 methyl bromide parent molecules. From the state-to-state photodissociation experiments the dissociationenergy for both isotopes was determined, D{sub 0}(CH{sub 3}Br)=23 400{+-}133 cm{sup -1} and D{sub 0}(CD{sub 3}Br)=23 827{+-}94 cm{sup -1}.},
doi = {10.1063/1.2813350},
url = {https://www.osti.gov/biblio/21024605}, journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = 22,
volume = 127,
place = {United States},
year = {2007},
month = {12}
}