Valence shell orbital imaging in adamantane by electron momentum spectroscopy

Measurements of electron binding energy spectra and electron momentum profi les (electron momentum distributions) for the valence orbitals of the cage molecule adamantane (C10H16) using electron momentum spectroscopy are repor ted. Theoretical momentum profiles are calculated using the plane-wave impu lse approximation (PWIA) within the target Hartree-Fock and also the target Kohn-Sham approximations (density functional theory, DFT) with the 4-31G a nd 6-311++G** basis sets and compared with the experimental results. The Ha rtree-Fock and the DFT calculations using the 6-311++G** basis set are in g ood quantitative agreement with the experimental momentum profiles. The exp erimental and the calculated orbital momentum distributions confirm the ten tative orbital assignments made in the earlier published studies of adamant ane by photoelectron spectroscopy. Small effects at low momenta, with the m easured cross-section being above the PWIA calculations for molecular orbit als of e and t(1) symmetry, are attributed to distorted-wave effects. (C) 2 000 Elsevier Science B.V. All rights reserved.