Resonant processes and Coulomb interactions in (C59N)2

Abstract

We have determined the on-site molecular Coulomb interaction energy U of a ͑C 59 N͒ 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 ͑RESPES͒ 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.

A comparative theoretical study on core-hole excitation spectra of azafullerene and its derivatives

“…We present the LUMOs of the molecules C 59 N (β-spin) and (C 59 N) + in Figs. 1(e) and 1(g), which were calculated at B3LYP/6-311+G* level in the ground state. Unlike the (C 59 N) 2 molecule whose LUMO has strong carbon character, 7,8,13,15 the LUMOs of the C 59 N and (C 59 N) + molecules given here also have obvious distribution around the nitrogen atom. As such, a strong or moderate peak A could be observed in their NEXAFS spectra.…”

“…7,8,13,15 This gives a very different picture from that of a single C 60 or C 59 N molecule. 7,8 The problem of the C 59 N monomer is its unpaired electron which makes itself a rather reactive radical, 15 such that it was until recently synthesized by doping into the crystalline C 60 , 16,17 in which the C 59 N molecules exist either in the form of heterodimers C 59 N-C 60 or dissociated monomers.…”

“…Although the NEXAFS and XPS shake-up satellites of the aza[60]fullerene dimer (C 59 N) 2 and the NEXAFS spectrum of the monomer C 59 N (on the silicon surface) have been reported, 8,[12][13][14]23 we are unaware of such a study on other C 59 N family members, especially a detailed theoretical study. As such, our current study could provide valuable results to assist further experimental measurements on these heterofullerenes and derivatives.…”

“…5 Therefore, understanding their electronic and chemical properties is paramount for their further studies and applications. Many efforts have been devoted to obtaining such knowledge as addressed in the aforementioned studies, in which one may notice the role of different x-ray spectra as valuable experimental techniques to probe the electronic structures of the aza [60]fullerene dimer (C 59 N) 2 , 8,[12][13][14] and even the monomer C 59 N on the silicon surface. 23 The near-edge x-ray absorption spectroscopy (NEX-AFS) is a well-known spectroscopic approach to detect the local structures of molecules, and the information of unoccupied molecular orbitals.…”

“…1,2 Among different heterofullerenes, the aza[60]fullerene dimer (C 59 N) 2 is probably the most known one and with macroscopic synthetic methods developed independently by the group of Wudl 3 and the group of Hirsch. 4 As such, (C 59 N) 2 as well as its functional derivatives have been extensively examined by both theoreticians and experimentalists, 5 for instance, its electron energy loss spectroscopy (EELS), [6][7][8] vibrational and Raman spectra, 7,9 electron spin resonance (ESR), 10 nuclear magnetic resonance (NMR), 11 and x-ray absorption and x-ray photoelectron spectroscopy (XAS and XPS), 8,[12][13][14] have all been investigated and used to reveal its stability, electronic, and chemical properties.…”