Valence shell orbital imaging in adamantane by electron momentum spectroscopy

Abstract

Measurements of electron binding energy spectra and electron momentum profiles (electron momentum distributions) for the valence orbitals of the cage molecule adamantane (C 10H 16) using electron momentum spectroscopy are reported. Theoretical momentum profiles are calculated using the plane-wave impulse approximation (PWIA) within the target Hartree–Fock and also the target Kohn–Sham approximations (density functional theory, DFT) with the 4-31G and 6-311++G** basis sets and compared with the experimental results. The Hartree–Fock and the DFT calculations using the 6-311++G** basis set are in good quantitative agreement with the experimental momentum profiles. The experimental and the calculated orbital momentum distributions confirm the tentative orbital assignments made in the earlier published studies of adamantane by photoelectron spectroscopy. Small effects at low momenta, with the measured cross-section being above the PWIA calculations for molecular orbitals of e and t 1 symmetry, are attributed to distorted-wave effects.