The influence of Jahn-Teller interaction, vibronic coupling and spin-orbitsplitting on the HeI excited photoelectron spectra of the boron trihalides

HeI excited photoelectron spectra of the boron trihalides have been recorde d with improved resolution, and several new vibrational progressions have b een observed in the spectra of BCl3, BBr3 and BI3. The spectra illustrate, as would be expected, that spin-orbit coupling becomes important in the hea vier trihalides, and affects the photoelectron band structure strongly. Pro gressions involving excitation of the symmetric stretching vibrational mode are observed in all four molecules. Some of the new structure revealed in the photoelectron spectra of BCl3, BBr3 and BI3 is assigned, and the molecu lar orbital configurations in BBr3 and BI3 are discussed, taking into accou nt existing theoretical predictions and the present experimental results.