Resonant processes and Coulomb interactions in (C59N)2

We have determined the on-site molecular Coulomb interaction energy U of a (C59N)(2) bulk film and find values ranging from 1.10 +/- 0.10 eV for the highest occupied molecular orbital to 1.35 +/- 0.10 eV for the deeper lying orbitals, comparable to values found in C-60. The on-site Coulomb interaction between a carbon core hole and valence electrons, U-c, is, however, substantially lower than in C-60 at 1.35 +/- 0.07 eV. Resonant photoemission (RESPES) results show a weakened participator decay channel, especially around the N 1s threshold, where resonance of the highest occupied molecular orbital shoulder is absent. Near-edge x-ray absorption fine structure and constant initial state measurements, taken in parallel with the RESPES data, indicate, however, that matrix element effects cannot be ruled out. (C) 2007 American Institute of Physics.