Electron affinity of phenanthrene and ion core structure of its anion clusters

We studied anion clusters of phenanthrene, Pn(n)(-) (n = 1-8), by mass distributions, photoelectron spectra, and theoretical calculations to determine the electron affinity of phenanthrene and the ion core structures of Pn(n)(-). The electron affinity of phenanthrene was determined to be 0.12 eV. The parallel-displaced structures with a fully delocalized excess electron over the entire phenanthrene moieties, which were obtained as stable geometries in the theoretical calculations, implied the presence of dimeric and trimeric ion cores in Pn(2)(-) and Pn(3)(-), respectively. For the tetramer and pentamer, photoelectron spectra with broad features and shoulders suggested the coexistence of ion cores. The magic number in the mass distributions and the unusual vertical detachment energy in the hexamer indicated the formation of a half-filled solvation shell.