Emission spectra of CF3 radicals. IV. Excitation spectra, quantum yields, and potential energy surfaces of the CF3 fluorescences

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Abstract
Cross sections, quantum yields, and threshold energies for the production of UV and visible emission bands of CF3 from photodissociation of CF3Br and CF3Cl were measured in the 115–130 nm region. The quantum yields for the production of UV and visible emission bands for 0.2–1.0 and 1%–5%, respectively, both for the photolysis of CF3Br and CF3Cl. Appearance energies of the UV and visible emission are (9.41±0.05) and (9.39±0.02) eV, respectively, in the photolysis of CF3Br and (10.10±0.08) and (10.08±0.07) eV, respectively, in the case of CF3Cl. These results show that the upper state energies of the UV and visible emissions are very close to 6.4 eV above the CF3 ground state. Potential energy surfaces of CF3 radicals were calculated by the ab initio CI method. Possible transitions suggested for the UV and visible emission bands are 2A′1 (Rydberg state)→1A″2 (ground state) and 1E′ and/or 2A″2 (both are Rydberg states)→1 A′1 (Rydberg state), respectively. These upper states 2A′1, 1E′, and 2A″2, are most stable in the D3h structure.