Outer valence electronic structure of pyrrole studied by electron momentum spectroscopy

The electronic structure of the pyrrole (C4H5N) molecule has been studied using electron momentum spectroscopy at an impact energy of 800 eV plus binding energy. Binding energy spectra have been measured at selected electron momenta. An attempt to clarify the band assignments, which have been in controversy, is made with the aid of theoretical electron momentum profiles calculated using the 6-31++G** basis set. A set of assignments which reproduces the observations is proposed, and it is concluded that electron correlation effects are significant in the innermost π electron ionization.