Photoelectron spectra of bromo- and iodo-thiophens

The photoelectron spectra of bromo- and iodo-thiophens with the halogen(s) in the 2-,3-. 2,5-, 3,4-, 2,3,5-, and 2,3,4,5-positions, have been recorded with HeI radiation, and the ionisation energies have been assigned down to 13 eV. The spectra were analysed on the basis of qualitative molecular orbital description, by mutual comparison and comparison with the spectra of bromo- and iodo-benzenes. Interactions between halogen Ione-pair electrons are discussed.