Partial photoionization cross sections of C60 and C70: A gas versus adsorbed phase comparison

We have performed high resolution measurements of the photoelectrons emitted from the valence shell of C-60 and C-70, in the gas phase and adsorbed phase on a metal surface, in order to derive branching ratios and the partial photoionization cross sections of the two highest occupied molecular orbitals. HOMO and HOMO-1. The comparison between the gas phase and the adsorbed phase shows an interesting and unexpected difference that can be attributed to a small orbital shift in solid Cm. Density Functional Theory calculations within the Local Density Approximation (LDA) show good agreement for both data sets and give a plausible explanation for the observed difference. (C) 2010 Elsevier B.V. All rights reserved.