A study of spin and symmetry forbidden transitions in CS2 by high resolution energy-loss spectroscopy

Energy-loss spectra of CS2 are presented in the energy-loss range 6-17 eV. Measurements of the variation of the intensity of spectral features with electron energy, and scattering angle were used to identify spin and symmetry forbidden transitions and where possible assignments have been suggested. A new Rydberg series, consisting of electric quadrupole transitions and converging to the lowest ionisation potential has been analysed, and assigned as an ns series. Three Rydberg series converging to the third ionisation limit were detected for the first time, and the assignment of these together with the optically-observed series are discussed. No new series were detected converging to the fourth ionisation potential, but the change in shape of members of two previously observed series, from dips to peaks as the electron energy is reduced was noted. In addition to the forbidden Rydberg series, two new triplet valence states at 6.9-7.4 eV and 12.4-12.7 eV have been detected, and the excitation energies of a number of unassigned, forbidden transitions have been measured. (orig.)