Photodissociation of CF3I AT 248 nm: Internal energy distribution of the CF3 fragments
1990; Elsevier BV; Volume: 143; Issue: 1 Linguagem: Inglês
10.1016/0301-0104(90)85014-n
ISSN1873-4421
Autores Tópico(s)Atmospheric Ozone and Climate
ResumoThe 248 nm photodissociation of trifluoromethyl iodide CF3I→CF3 + I(2P32, 2P12) has been studied by high-resolution photofragment translational spectroscopy. Time-of-flight (TOF) distributions of the CF3 and I photofragments were measured by means of an apparatus equipped with a rotatable pulsed molecular beam source. The dissociation energy D0 (CF3-I) ≤ 19300±350cm−1 (231 ± 4 kJ/mool) is obtained from the high-energy thresholds of the TOF spectra. The average internal energy of the CF3 fragments produced in coincidence with ground state I atoms is ≈ 4900 cm−1. In the case of the dominant reaction, which yields CF3 radicals and spin-orbit excited I (2P12) atoms, the average internal energy amounts to 3100 cm−1. Vibrational structure with a spacing of ≈ 700 cm−1 is resolved in some of the TOF spectra, indicating excitation of the ν2 “umbrella” mode of the CF3 fragment. The vibrational distribution has a width of ≈ 2400 cm−1 (fwhm) and is thus considerably narrower than reported in a previous TOF study. Our results support the mechanism assumed for CF3I photodissociation and provide information on the importance of translation-vibration coupling on the repulsive excited state potential energy surfaces.
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