Valence orbital electron momentum distributions for dimethylsulfide: comparison of EMS measurements with near Hartree–Fock limit and density functional theory calculations

Abstract

The binding energy spectra and orbital electron momentum density distributions of the complete valence shell of (CH 3) 2S have been measured by electron momentum spectroscopy at a total energy of 1200 eV+binding energy. Binding energies for the three inner valence (6a 1, 3b 2 and 5a 1) orbitals which have not been well characterized by photoelectron spectroscopy have been assigned in the present work. The extensive structure observed in the high energy region from 30 to 55 eV is attributed to satellite peaks from the inner valence orbitals. Measured electron momentum profiles for each of the valence orbitals are compared with calculations using the target Hartree–Fock approximation and SCF wavefunctions with a range of basis sets up to the large, saturated and diffuse aug-cc-pV5Z basis set. The observed momentum profiles are also compared with DFT momentum profiles calculated using the target Kohn–Sham approximation with the B3LYP and B3PW91 gradient corrected functionals. Individual experimental and calculated momentum profiles are presented for the three outermost orbitals (3b 1, 8a 1 and 5b 2) while the summed experimental data and calculations are presented for the four closely-spaced 1a 2, 4b 2, 7a 1 and 2b 1 higher binding energy orbitals in the outer valence region. Experimental and theoretical momentum profiles for the three inner valence orbitals are also presented. In general, both the Hartree–Fock and DFT calculations with high-level basis sets give good descriptions of the experimental electron momentum profiles.