The photoelectron spectra of some molecules containing the C≡N group

The photoelectron spectra of a number of molecules containing the C$\equiv $N group have been measured over the range 6 to 21 eV. For cyanogen chloride, cyanogen bromide and cyanogen iodide, ionization potentials have been determined and assigned to particular molecular orbitals on the basis of the vibrations coupled with the ionization processes, and of the splitting due to spin-orbit coupling. Differences in these features among the three compounds have been discussed in terms of the delocalization of electrons in these molecules. From the spectra of methyl, ethyl, vinyl and allyl cyanides, potentials have been determined for ionization from the C==C $\pi $, C$\equiv \pi $ and nitrogen lone pair orbitals, and other higher ionization potentials have been determined but not assigned explicitly. A number of ionization potentials have been determined for mono-, di-, and tri-chloro-methyl cyanides, but absence of accompanying vibrational structure and the additional complexity caused by the levels derived from 3p electrons in the chlorine atoms make specific assignments impossible.