THRESHOLD PHOTOELECTRON-SPECTROSCOPY OF CF4 UP TO 60.5-EV

The threshold photoelectron spectrum of CF4 up to 60.5 eV has been recorded using synchrotron radiation and a penetrating-field electron spectrometer of high resolution. Our results confirm the broad spectral features of the (X) over tilde T-2(1), (A) over tilde T-2(2) and (B) over tilde (2)E state bands of CF4+ reported previously with He I PES. The influence of autoionizing super-excited state of CF4 has been observed as an extension of the high-energy tail of the (B) over tilde (2)E state, as a structured band in the energy region between the (B) over tilde (2)E and (C) over tilde T-2(2) states, and as additional Vibrational structure extending the (D) over tilde (2)A(1) state band. Improved spectra of the (C) over tilde T-2(2) and (D) over tilde (2)A(1) states have been obtained as a consequence of the high resolution of this study. The overall electronic state band profiles observed here up to about 26 eV agree with a recently published low-resolution threshold photoelectron spectrum of CF4 [Creasey et al., Chem. Phys., 174 (1993) 441]. Between 26 and 60.5 eV a continuum-like background was observed with some broad-band features superimposed on it. One broad peak, centered on 40.3 eV, is tentatively assigned to the formation of the (E) over tilde T-2(2) and (F) over tilde (2)A(1) states of CF4+, but the formation of the double-charged ion, CF42+, may also be involved.