Orbital electron densities of ethane: Comparison of electron momentum spectroscopy measurements with near Hartree–Fock limit and density functional theory calculations

Abstract

The calculation of the static first and second susceptibilities of crystalline urea: A comparison of Hartree-Fock and density functional theory results obtained with the periodic coupled perturbed Hartree-Fock/Kohn-Sham scheme Investigation of orbital momentum profiles of methylpropane (isobutane) by binary (e,2e) spectroscopy Configuration interaction singles, time-dependent Hartree-Fock, and time-dependent density functional theory for the electronic excited states of extended systems Electron density distributions in momentum space of the valence orbitals of ethane (C 2 H 6 ) are measured by electron momentum spectroscopy ͑EMS͒ in a noncoplanar symmetric geometry. The impact energy was 1200 eV plus binding energy and energy resolution of the EMS spectrometer was 0.95 eV. The measured experimental momentum distributions of the valence orbitals are compared with Hartree-Fock and density functional theory ͑DFT͒ calculations. The shapes of the experimental momentum distributions are generally quite well described by both the Hartree-Fock and DFT calculations when large and diffuse basis sets are used. A strong ''turn up'' of the experimental cross section is observed for the HOMO 1e g orbital in the low momentum region, compared with the theoretical calculations. The pole strengths for the main ionization peaks in the inner-valence region are estimated.