Sum rule consideration on valence orbital ionization energies in methyl amines

Abstract

A sum rule treatment using Hall's equivalent orbitals has been applied to the valence orbital ionization energies of mono-, di- and trimethylamine up to about 40 eV assuming Koopman's theorem. Excellent agreement is obtained between theory and experiment in partial and total energy sums. A similar treatment using p-type localized orbitals previously proposed by the authors is also applied to ionization energies below about 18 eV for the methyl amines. In these sum rule treatments we use both the vertical ionization energies obtained from He (I) photoelectron spectra measured here and the higher ionization energies deduced from the He (II) photoelectron spectra published by Potts et al. The complete sets of valence orbital ionization energies of the methyl amines have thus been identified by sum rule considerations in photoelectron spectroscopy. We show that the character of the corresponding MO's may be inferred from the sum rule. The orbital orderings and characters of the methyl amines have also been st...