Knowledge Bank

Ab initio calculations, mostly by means of the CEPA-1 $method,1$ were carried out for radicals and cation of type $CXnY3-n$ 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 $CCl3$, which may be well described as a two-mode problem, shows more than 100 lines with more than 1% relative intensity in the range $0--10000cm-1$. Several of the vibrational frequencies of the cations may be compared with experimental data from matrix-isolation IR spectroscopy;$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ throughout the agreement is very good.