AB INITIO CALCULATION OF THE VIBRATIONAL STRUCTURE OF PHOTOELECTRON SPECTRA FOR FREE RADICALS

Abstract

Ab initio calculations, mostly by means of the CEPA-1 $method,^{1}$ were carried out for radicals and cation of type $CX_{n} Y_{3-n}$ with $X,Y = F, $Cl. Most emphasis is given to the vibrational structure of the first band of the photoelectron (PE) spectra. Due to strong mode coupling these are rather complex. Already the low-temperature PE spectrum of $CCl_{3}$, which may be well described as a two-mode problem, shows more than 100 lines with more than 1% relative intensity in the range $0--10000 cm^{-1}$. Several of the vibrational frequencies of the cations may be compared with experimental data from matrix-isolation IR spectroscopy;$^{2}$ throughout the agreement is very good.