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Title: Photodissociating trimethylamine at 193 nm to probe dynamics at a conical intersection and to calibrate detection efficiency of radical products

Abstract

This paper reports crossed laser-molecular beam scattering experiments measuring the photofragment velocities and product branching in the photodissociation of trimethylamine (N(CH{sub 3}){sub 3}) at 193 nm. We have observed two primary N{endash}CH{sub 3} bond fission channels that ultimately produce different nitrogen-containing species, CH{sub 3}+N(CH{sub 3}){sub 2} ({tilde X} {sup 2}B{sub 1}); CH{sub 3}+N(CH{sub 3}){sub 2}{sup {asterisk}}{r_arrow}CH{sub 3}+CH{sub 2}NCH{sub 3}+H. The data also indicate that a third minor channel may contribute to the dissociation dynamics, CH{sub 3}+N(CH{sub 3}){sub 2}{sup {dagger}}{r_arrow}CH{sub 3}+NC{sub 2}H{sub 4}+H{sub 2}. The experiments show that ground state N(CH{sub 3}){sub 2} radicals are formed in the photodissociation, in sharp contrast to the exclusive production of NH{sub 2} ({tilde A} {sup 2}A{sub 1}) in a similar molecule, methylamine. We discuss how this results from the differing dynamics through the S{sub 1}{endash}S{sub 0} conical intersection in the exit channel in these two dissociating amines. We also use the photodissociation results to calibrate the mass spectrometric sensitivity at the m/e=15 daughter ion for methyl radicals vs N(CH{sub 3}){sub 2} and CH{sub 2}NCH{sub 3} products. This provides the only necessary calibration to determine an absolute branching ratio in any system producing a methyl radical in one reaction channel and N(CH{sub 3}){sub 2} ({tildemore » X} {sup 2}B{sub 1}) or CH{sub 2}NCH{sub 3} in other reaction channels. {copyright} {ital 1999 American Institute of Physics.}« less

Authors:
; ; ; ;  [1]
  1. The James Franck Institute and Department of Chemistry, The University of Chicago, Chicago, Illinois 60637 (United States)
Publication Date:
OSTI Identifier:
365976
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 111; Journal Issue: 10; Other Information: PBD: Sep 1999
Country of Publication:
United States
Language:
English
Subject:
40 CHEMISTRY; ORGANIC COMPOUNDS; PHOTOLYSIS; ULTRAVIOLET RADIATION; AMINES; LASER RADIATION; MOLECULAR BEAMS; METHYL RADICALS; BRANCHING RATIO; DISSOCIATION

Citation Formats

Forde, N.R., Morton, M.L., Curry, S.L., Wrenn, S.J., and Butler, L.J. Photodissociating trimethylamine at 193 nm to probe dynamics at a conical intersection and to calibrate detection efficiency of radical products. United States: N. p., 1999. Web. doi:10.1063/1.479217.
Forde, N.R., Morton, M.L., Curry, S.L., Wrenn, S.J., & Butler, L.J. Photodissociating trimethylamine at 193 nm to probe dynamics at a conical intersection and to calibrate detection efficiency of radical products. United States. doi:10.1063/1.479217.
Forde, N.R., Morton, M.L., Curry, S.L., Wrenn, S.J., and Butler, L.J. Wed . "Photodissociating trimethylamine at 193 nm to probe dynamics at a conical intersection and to calibrate detection efficiency of radical products". United States. doi:10.1063/1.479217.
@article{osti_365976,
title = {Photodissociating trimethylamine at 193 nm to probe dynamics at a conical intersection and to calibrate detection efficiency of radical products},
author = {Forde, N.R. and Morton, M.L. and Curry, S.L. and Wrenn, S.J. and Butler, L.J.},
abstractNote = {This paper reports crossed laser-molecular beam scattering experiments measuring the photofragment velocities and product branching in the photodissociation of trimethylamine (N(CH{sub 3}){sub 3}) at 193 nm. We have observed two primary N{endash}CH{sub 3} bond fission channels that ultimately produce different nitrogen-containing species, CH{sub 3}+N(CH{sub 3}){sub 2} ({tilde X} {sup 2}B{sub 1}); CH{sub 3}+N(CH{sub 3}){sub 2}{sup {asterisk}}{r_arrow}CH{sub 3}+CH{sub 2}NCH{sub 3}+H. The data also indicate that a third minor channel may contribute to the dissociation dynamics, CH{sub 3}+N(CH{sub 3}){sub 2}{sup {dagger}}{r_arrow}CH{sub 3}+NC{sub 2}H{sub 4}+H{sub 2}. The experiments show that ground state N(CH{sub 3}){sub 2} radicals are formed in the photodissociation, in sharp contrast to the exclusive production of NH{sub 2} ({tilde A} {sup 2}A{sub 1}) in a similar molecule, methylamine. We discuss how this results from the differing dynamics through the S{sub 1}{endash}S{sub 0} conical intersection in the exit channel in these two dissociating amines. We also use the photodissociation results to calibrate the mass spectrometric sensitivity at the m/e=15 daughter ion for methyl radicals vs N(CH{sub 3}){sub 2} and CH{sub 2}NCH{sub 3} products. This provides the only necessary calibration to determine an absolute branching ratio in any system producing a methyl radical in one reaction channel and N(CH{sub 3}){sub 2} ({tilde X} {sup 2}B{sub 1}) or CH{sub 2}NCH{sub 3} in other reaction channels. {copyright} {ital 1999 American Institute of Physics.}},
doi = {10.1063/1.479217},
journal = {Journal of Chemical Physics},
number = 10,
volume = 111,
place = {United States},
year = {1999},
month = {9}
}