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Title: The cavity ringdown spectrum of the visible electronic system of thiophosgene: An estimation of the lifetime of the T[sub 1]([tilde a]; [sup 3]A[sub 2]) triplet state

Abstract

To obtain insights into the photophysical properties of collision-free T[sub 1]([tilde a] hthinsp;[sup 3]A[sub 2]) thiophosgene, Cl[sub 2]CS, the cavity ringdown (CRD) spectrum of the T[sub 1][l arrow]S[sub 0] absorption system was recorded under supersonic jet conditions and compared with the corresponding excitation spectrum of the total emission. It was found that none of the T[sub 1][l arrow]S[sub 0] bands in the CRD spectrum appears in the excitation spectrum, indicating that the T[sub 1] thiophosgene decays almost exclusively by the nonradiative T[sub 1][r arrow]S[sub 0] intersystem crossing (ISC). An estimation of the T[sub 1] nonradiative lifetime was made using the T[sub 1][endash]S[sub 0] spin-orbit coupling and the Franck[endash]Condon factors for the T[sub 1][r arrow]S[sub 0] ISC based on the [ital ab initio] equilibrium structures and vibrational frequencies for the T[sub 1] and S[sub 0] states, computed at the MP2/6-31G(d,p) and MP4/6-31G(d,p) level of theory. The nonradiative life, calculated as the 1/e of the survival probability, is approximately 20 ps for barrier heights of 770[endash]845 cm[sup [minus]1] and out-of-plane angles of 32.07[degree][endash]32.69[degree]. (The thiophosgene adopts a pyramidal conformation with the C[double bond]S bond bent from the ClCCl plane by about 32[degree].) The computed lifetime is comparable to the lower-limit lifetime ofmore » [approximately]50 ps obtained from the quantum yields [Phi][sub P][le]10[sup [minus]3][Phi][sub F] with [Phi][sub F][approx]1.0 and the measured S[sub 1] fluorescence lifetime of 4 [mu]s. The short T[sub 1] nonradiative lifetime of thiophosgene can be attributed to the large matrix elements of the T[sub 1][endash]S[sub 0] spin-orbit coupling (V=150 hthinsp;cm[sup [minus]1]) and the strong out-of-plane deformation of the T[sub 1] state relative to the planar S[sub 0] state, that provides the large Franck[endash]Condon factors for the T[sub 1][r arrow]S[sub 0] ISC. It is proposed that a similar pyramidal deformation is also responsible for the absence of phosphorescence from T[sub 1] thiocyclobutanone. Consistent with this supposition, T[sub 1] cyclopentanone, which is nearly planar at the thiocarbonyl carbon center, exhibits strong phosphorescence under similar experimental conditions. [copyright] [ital 1999 American Institute of Physics.]« less

Authors:
;  [1]; ;  [2]
  1. (Department of Chemistry, Brock University, St. Catharines, Ontario, L2S3A1 (Canada))
  2. (Knight Chemical Laboratory, University of Akron, Akron, Ohio 44325-3601 (United States))
Publication Date:
OSTI Identifier:
5903302
Alternate Identifier(s):
OSTI ID: 5903302
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 111:11; Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ABSORPTION SPECTRA; CONFORMATIONAL CHANGES; ELECTRONIC STRUCTURE; EXCITED STATES; FLUORESCENCE; FRANCK-CONDON PRINCIPLE; LIFETIME; ORGANIC COMPOUNDS; PHOSGENE; PHOSPHORESCENCE; SULFUR COMPOUNDS; VIBRATIONAL STATES; VISIBLE SPECTRA; CARBONIC ACID DERIVATIVES; ENERGY LEVELS; LUMINESCENCE; ORGANIC CHLORINE COMPOUNDS; ORGANIC HALOGEN COMPOUNDS; SPECTRA 664200* -- Spectra of Atoms & Molecules & their Interactions with Photons-- (1992-)

Citation Formats

Moule, D.C., Burling, I.R., Liu, H., and Lim, E.C. The cavity ringdown spectrum of the visible electronic system of thiophosgene: An estimation of the lifetime of the T[sub 1]([tilde a]; [sup 3]A[sub 2]) triplet state. United States: N. p., 1999. Web. doi:10.1063/1.479760.
Moule, D.C., Burling, I.R., Liu, H., & Lim, E.C. The cavity ringdown spectrum of the visible electronic system of thiophosgene: An estimation of the lifetime of the T[sub 1]([tilde a]; [sup 3]A[sub 2]) triplet state. United States. doi:10.1063/1.479760.
Moule, D.C., Burling, I.R., Liu, H., and Lim, E.C. Wed . "The cavity ringdown spectrum of the visible electronic system of thiophosgene: An estimation of the lifetime of the T[sub 1]([tilde a]; [sup 3]A[sub 2]) triplet state". United States. doi:10.1063/1.479760.
@article{osti_5903302,
title = {The cavity ringdown spectrum of the visible electronic system of thiophosgene: An estimation of the lifetime of the T[sub 1]([tilde a]; [sup 3]A[sub 2]) triplet state},
author = {Moule, D.C. and Burling, I.R. and Liu, H. and Lim, E.C.},
abstractNote = {To obtain insights into the photophysical properties of collision-free T[sub 1]([tilde a] hthinsp;[sup 3]A[sub 2]) thiophosgene, Cl[sub 2]CS, the cavity ringdown (CRD) spectrum of the T[sub 1][l arrow]S[sub 0] absorption system was recorded under supersonic jet conditions and compared with the corresponding excitation spectrum of the total emission. It was found that none of the T[sub 1][l arrow]S[sub 0] bands in the CRD spectrum appears in the excitation spectrum, indicating that the T[sub 1] thiophosgene decays almost exclusively by the nonradiative T[sub 1][r arrow]S[sub 0] intersystem crossing (ISC). An estimation of the T[sub 1] nonradiative lifetime was made using the T[sub 1][endash]S[sub 0] spin-orbit coupling and the Franck[endash]Condon factors for the T[sub 1][r arrow]S[sub 0] ISC based on the [ital ab initio] equilibrium structures and vibrational frequencies for the T[sub 1] and S[sub 0] states, computed at the MP2/6-31G(d,p) and MP4/6-31G(d,p) level of theory. The nonradiative life, calculated as the 1/e of the survival probability, is approximately 20 ps for barrier heights of 770[endash]845 cm[sup [minus]1] and out-of-plane angles of 32.07[degree][endash]32.69[degree]. (The thiophosgene adopts a pyramidal conformation with the C[double bond]S bond bent from the ClCCl plane by about 32[degree].) The computed lifetime is comparable to the lower-limit lifetime of [approximately]50 ps obtained from the quantum yields [Phi][sub P][le]10[sup [minus]3][Phi][sub F] with [Phi][sub F][approx]1.0 and the measured S[sub 1] fluorescence lifetime of 4 [mu]s. The short T[sub 1] nonradiative lifetime of thiophosgene can be attributed to the large matrix elements of the T[sub 1][endash]S[sub 0] spin-orbit coupling (V=150 hthinsp;cm[sup [minus]1]) and the strong out-of-plane deformation of the T[sub 1] state relative to the planar S[sub 0] state, that provides the large Franck[endash]Condon factors for the T[sub 1][r arrow]S[sub 0] ISC. It is proposed that a similar pyramidal deformation is also responsible for the absence of phosphorescence from T[sub 1] thiocyclobutanone. Consistent with this supposition, T[sub 1] cyclopentanone, which is nearly planar at the thiocarbonyl carbon center, exhibits strong phosphorescence under similar experimental conditions. [copyright] [ital 1999 American Institute of Physics.]},
doi = {10.1063/1.479760},
journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = ,
volume = 111:11,
place = {United States},
year = {1999},
month = {9}
}