The helium-(I) photoelectron spectra of some halogens and diatomic interhalogens

Medium resolution helium(I) photoelectron spectra of the halogen molecules Cl 2 , Br 2 and I 2 , and of the diatomic interhalogens, ICl and IBr, are reported. Vibrational fine structure is discernible in the first photoionisation bands of Cl 2 , Br 2 and ICl, while multiplet splittings are evident in the photoelectron spectra of Br 2 , I 2 , ICl and IBr. The details of the spectra are consistent with established qualitative concepts of molecular orbital theory.