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Title: Molecular elimination in photolysis of o- and p-fluorotoluene at 193 nm: Internal energy of HF determined with time-resolved Fourier transform spectroscopy

Abstract

Following the photodissociation of o-fluorotoluene [o-C{sub 6}H{sub 4}(CH{sub 3})F] at 193 nm, rotationally resolved emission spectra of HF(1{<=}v{<=}4) in the spectral region of 2800-4000 cm{sup -1} are detected with a step-scan Fourier transform spectrometer. HF(v{<=}4) shows nearly Boltzmann-type rotational distributions corresponding to a temperature {approx}1080 K; a short extrapolation from data in the period of 0.5-4.5 {mu}s leads to a nascent rotational temperature of 1130{+-}100 K with an average rotational energy of 9{+-}2 kJ mol{sup -1}. The observed vibrational distribution of (v=1):(v=2):(v=3)=67.6: 23.2: 9.2 corresponds to a vibrational temperature of 5330{+-}270 K. An average vibrational energy of 25{+-}{sub 3}{sup 12} kJ mol{sup -1} is derived based on the observed population of HF(1{<=}v{<=}3) and estimates of the population of HF (v=0 and 4) by extrapolation. Experiments performed on p-fluorotoluene [p-C{sub 6}H{sub 4}(CH{sub 3})F] yielded similar results with an average rotational energy of 9{+-}2 kJ mol{sup -1} and vibrational energy of 26{+-}{sub 3}{sup 12} kJ mol{sup -1} for HF. The observed distributions of internal energy of HF in both cases are consistent with that expected for four-center elimination. A modified impulse model taking into account geometries and displacement vectors of transition states during bond breaking predicts satisfactorily the rotational excitation of HF.more » An observed vibrational energy of HF produced from fluorotoluene slightly smaller than that from fluorobenzene might indicate the involvement of seven-membered-ring isomers upon photolysis.« less

Authors:
; ; ;  [1];  [2];  [2]
  1. Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan (China)
  2. (China)
Publication Date:
OSTI Identifier:
20723267
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 123; Journal Issue: 22; Other Information: DOI: 10.1063/1.2131072; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CHEMICAL BONDS; EMISSION SPECTRA; EXTRAPOLATION; FOURIER TRANSFORM SPECTROMETERS; FOURIER TRANSFORMATION; HYDROFLUORIC ACID; ISOMERS; LUMINESCENCE; ORGANIC FLUORINE COMPOUNDS; PHOTOLYSIS; PHOTON-MOLECULE COLLISIONS; ROTATIONAL STATES; TIME RESOLUTION; VIBRATIONAL STATES

Citation Formats

Yang, S.-K., Liu, S.-Y., Chen, H.-F., Lee, Y.-P., Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan, and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan. Molecular elimination in photolysis of o- and p-fluorotoluene at 193 nm: Internal energy of HF determined with time-resolved Fourier transform spectroscopy. United States: N. p., 2005. Web. doi:10.1063/1.2131072.
Yang, S.-K., Liu, S.-Y., Chen, H.-F., Lee, Y.-P., Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan, & Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan. Molecular elimination in photolysis of o- and p-fluorotoluene at 193 nm: Internal energy of HF determined with time-resolved Fourier transform spectroscopy. United States. doi:10.1063/1.2131072.
Yang, S.-K., Liu, S.-Y., Chen, H.-F., Lee, Y.-P., Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan, and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan. Thu . "Molecular elimination in photolysis of o- and p-fluorotoluene at 193 nm: Internal energy of HF determined with time-resolved Fourier transform spectroscopy". United States. doi:10.1063/1.2131072.
@article{osti_20723267,
title = {Molecular elimination in photolysis of o- and p-fluorotoluene at 193 nm: Internal energy of HF determined with time-resolved Fourier transform spectroscopy},
author = {Yang, S.-K. and Liu, S.-Y. and Chen, H.-F. and Lee, Y.-P. and Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan},
abstractNote = {Following the photodissociation of o-fluorotoluene [o-C{sub 6}H{sub 4}(CH{sub 3})F] at 193 nm, rotationally resolved emission spectra of HF(1{<=}v{<=}4) in the spectral region of 2800-4000 cm{sup -1} are detected with a step-scan Fourier transform spectrometer. HF(v{<=}4) shows nearly Boltzmann-type rotational distributions corresponding to a temperature {approx}1080 K; a short extrapolation from data in the period of 0.5-4.5 {mu}s leads to a nascent rotational temperature of 1130{+-}100 K with an average rotational energy of 9{+-}2 kJ mol{sup -1}. The observed vibrational distribution of (v=1):(v=2):(v=3)=67.6: 23.2: 9.2 corresponds to a vibrational temperature of 5330{+-}270 K. An average vibrational energy of 25{+-}{sub 3}{sup 12} kJ mol{sup -1} is derived based on the observed population of HF(1{<=}v{<=}3) and estimates of the population of HF (v=0 and 4) by extrapolation. Experiments performed on p-fluorotoluene [p-C{sub 6}H{sub 4}(CH{sub 3})F] yielded similar results with an average rotational energy of 9{+-}2 kJ mol{sup -1} and vibrational energy of 26{+-}{sub 3}{sup 12} kJ mol{sup -1} for HF. The observed distributions of internal energy of HF in both cases are consistent with that expected for four-center elimination. A modified impulse model taking into account geometries and displacement vectors of transition states during bond breaking predicts satisfactorily the rotational excitation of HF. An observed vibrational energy of HF produced from fluorotoluene slightly smaller than that from fluorobenzene might indicate the involvement of seven-membered-ring isomers upon photolysis.},
doi = {10.1063/1.2131072},
journal = {Journal of Chemical Physics},
number = 22,
volume = 123,
place = {United States},
year = {Thu Dec 08 00:00:00 EST 2005},
month = {Thu Dec 08 00:00:00 EST 2005}
}