He*(23S) Penning ionization electron spectra (PIES) as well as He I ultraviolet photoelectron spectra have been measured for CH2BrCl, CHBrCl2, and CH2BrCN. For the lower ionization-potential bands, spin-orbit split states are assigned in the spectra for CH2BrCl and CH2BrCN, whereas valence-orbital, ionic states are assigned for CHBrCl2. These assignments are based on the fact that the intramolecular orbital interactions in CHBrCl2 are much stronger than those in the other molecules, whereas the spin-orbit coupling effects predominate for the other two molecules. Collision energy dependence of partial Penning ionization cross sections and the PIES indicate that the magnitudes of the attractive interactions in the electron distribution regions of the lone pair orbitals (n) of the Cl and Br atoms and the N atom in the CN group and πCN orbitals are in a sequence of nN ≫ nBr ∼ πCN > nCl.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry