High-Resolution Photoelectron Imaging of Cryogenically-Cooled C59N- and (C59N)22- Azafullerene Anions.

We report a photoelectron imaging study of cryogenically cooled C59N- and (C59N)22- anions produced from electrospray ionization. High-resolution photoelectron spectra are obtained for C59N- for the first time, allowing seven vibrational frequencies of the C59N azafullerene to be measured. The electron affinity of C59N is determined accurately to be 3.0150 ± 0.0007 eV. The observed vibrational features are understood on the basis of calculated frequencies and compared with those of C60 and C59HN. The photoelectron image of (C59N)22-, which has the same mass/charge ratio as C59N-, is also observed, allowing the second electron affinity of the (C59N)2 azafullerene dimer to be measured as 1.20 ± 0.05 eV. The intramolecular Coulomb repulsion of the (C59N)22- dianion is estimated to be 1.96 eV and is investigated theoretically using the electron density difference between (C59N)22- and (C59N)2.