Resonance Raman excitation and electronic structure of the single bonded dimers (C-60(-))(2) and (C59N)(2)

Raman spectra are presented for the single bonded dimeric fullerene (C-60(- ))(2) and compared to optical spectra and Raman spectra of the isostructura l and isoelectronic heterofullerene (C59N)(2). The spectra of both material s exhibit strong correlations with respect to splitting, line position, and line intensity. This holds for non resonant excitation with blue and green lasers as well as for the strong resonances observed with red lasers. The latter observation is consistent with a downshift for the electronic transi tion energies as compared to C-60. The absorption edge of thin films of (C5 9N)(2) was found at 1.4 eV. The three intercage modes were observed at 82, 103, and 111, and at 88, 98, and 106 cm(-1) for (C59N)(2) and (C-60(-))(2), respectively. A surprising-difference was found for the position of the pe ntagonal pinch modes in the two materials as they were observed at 1461 and at 1451 cm(-1), for (C59N)(2) and (C-60(-))(2), respectively. This is inte rpreted as a consequence of some characteristic differences in the electron ic Structure of the two compounds.