Vibrational and electronic excitations of (C59N)(2)

High-resolution electron energy loss spectroscopy (HREELS) has been used to investigate the vibrational and electronic excitations of the modified ful lerene C59N in the form of a multilayer film deposited on single crystal gr aphite C(0001). The vibrational modes show a strong relation to those of C- 60, except for two new modes resulting from the dimerisation: an intermolec ular mode around 17 meV and a dipole-active mode at 104 meV. The electronic excitation spectrum is - regarding the interband transitions - also simila r to that of C-60, despite a broadening due to the lower symmetry in (C59N) (2). However, the first excitonic excitations at 1.58 and 1.73 eV are dipol e-allowed in the heterofullerene, in stark contrast to the situation in C-6 0. (C) 2001 Elsevier Science Ltd. All rights reserved.