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JOURNAL OF CHEMICAL PHYSICS, vol.139, no.20, 2013 (SCI-Expanded)
The molecular structure and infrared spectrum of the atmospheric pollutant 1,1,1-trifluoro-2chloroethane (HCFC-133a; CF3CH2Cl) in the ground electronic state were characterized experimentally and theoretically. Excited state calculations (at the CASSCF, MR-CISD, and MR-CISD+Q levels) have also been performed in the range up to similar to 9.8 eV. The theoretical calculations show the existence of one (staggered) conformer, which has been identified spectroscopically for the monomeric compound isolated in cryogenic (similar to 10 K) argon and xenon matrices. The observed infrared spectra of the matrix-isolated HCFC-133a were interpreted with the aid of MP2/aug-cc-pVTZ calculations and normal coordinate analysis, which allowed a detailed assignment of the observed spectra to be carried out, including identification of bands due to different isotopologues (Cl-35 and Cl-37 containing molecules). The calculated energies of the several excited states along with the values of oscillator strengths and previous results obtained for CFCs and HCFCs suggest that the previously reported photolyses of the title compound at 147 and 123.6 nm [T. Ichimura, A. W. Kirk, and E. Tschuikow-Roux, J. Phys. Chem. 81, 1153 (1977)] are likely to be initiated in the n-4s and n-4p Rydberg states, respectively. (C) 2013 AIP Publishing LLC.