Assignment of the UV photoelectron spectra of the azoles by Ab initio multi-reference configuration interaction calculations

Abstract

Ab initio multi-reference CI calculations have been performed on pyrrole, pyrazole, imidazole, each of the triazoles and tetrazole. The tautomerism of these species is discussed, and the UV photoelectron spectra are reinterpreted in the light of the CI data. Many shake-up states are evident above ≈ 14 eV; these can cause difficulties in the positioning of LP N states by CI methods.