Final-state interference effects in valence band photoemission of (C59N)2.

Oscillatory behavior of photoemission intensity with incident photon energy has been observed for several fullerenes and fullerene derivatives. However, until now it has been unclear if these effects arise from interference associated with the spatial distribution of the initial state within the molecule or are due to scattering of the outgoing photoelectron. In order to resolve this issue we performed synchrotron radiation excited valence band photoemission measurements on multilayer (C59N)2 films. The highest occupied molecular orbital (HOMO) of the (C59N)2 dimer is spatially localized, while each half of the dimer remains approximately spherical. Careful normalization and fitting of the measured spectra clearly show that the intensity of the HOMO also displays a periodic variation of intensity with photon energy indicating that scattering of the photoemitted electron and consequent interference effects lead to the observed intensity changes