Emission spectra of CF3 radicals. V. Photodissociation of CF3H, CF3Cl, and CF3Br by vacuum ultraviolet

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Abstract
The absorption cross sections of CF3H, CF3Cl, and CF3Br and the fluorescence cross sections for their photofragments are measured in the 106–155 nm region using synchrotron radiation as a light source. The threshold wavelengths for producing the CF3 UV fluorescence from photodissociation of CF3X (X=H, Cl, and Br) are 113.0, 122.2, and 132.4 nm, respectively. The threshold energy is nearly equal to the calculated sum of the CF*3 excited state energy and the dissociation energy for each molecule. The excitation spectra for the UV and visible fluorescence are different, and the threshold wavelength for the CF3 visible fluorescence is slightly longer than that for the UV fluorescence. These results strongly support previous conclusions that the upper states of the CF3 UV and visible fluorescence are different, and that the upper state energy of the UV fluorescence is higher than that of the visible one. The processes for photodissociation of CF3X into various fragments are discussed.