Photoelectron spectra and electronic structure of lithium halide monomers and dimers

Abstract

The He(I) photoelectron spectra of the monomers and dimers of the chloride, bromide and iodide of lithium have been recorded in the vapour phase by the use of a molecular beam technique. The spectra were interpreted with the aid of ab initio SCF calculations and consideration of spin–orbit coupling. The agreement between prediction and observation is good and the valence electronic structure of both the monomers and dimers can be understood in terms of spectral features expected from calculations. A point charge model was also used to predict experimental i.p.s. Although i.p.s. were predicted accurately for the monomers, the deviation between experiment and calculation was more marked for the dimers. This was attributed to a possibly increased covalent bonding contribution for the dimers which limits the applicability of the ionic model in this case.