Vacuum-UV fluorescence spectroscopy of CF 3X(X=F,H,Cl,Br) in the range 10–30 eV

Abstract

The vacuum-UV and visible spectroscopy of CF 3X(X=F,H,Cl,Br) using fluorescence excitation and dispersed emission techniques is reported. Fluorescence excitation spectra have been recorded following excitation using dispersed synchroton radiation in the energy range 10–30 eV at an average resolution of ∼0.06 eV. By comparison with vacuum-UV absorption and electron energy loss spectra, assignments have been made for all the peaks in the Rydberg spectra of the titled molecules that photodissociate to a fluorescing state of a fragment. Dispersed emission spectra have been recorded at the energies of all the peaks in the excitation spectra. Three distinct decay channels are observed: (a) CF 3 fluorescence for photon energies in the range 10.5 to 13.5 eV, (b) CF 2 fluorescence for photon energies in the range 14.7 to 15.7 eV, (c) for photon energies in the range 20–23 eV parent ion fluorescence in the case of CF 4 and CF 3H, predominantly CF emission in the case of CF 3Cl and CF 3Br. These assignments are confirmed by action spectra in which the energy of the vacuum-UV radiation is tuned for detection at a specific (dispersed) wavelength. These results confirm those reported in the previous paper from fluorescence coincidence experiments that parent-ion fluorescence is the major component of the emission for CF 4 and CF 3H excited in this latter energy range of 20–23 eV, whereas it represents only a minor component for CF 3Cl and a negligibly-small component for CF 3Br.