Vibrational spectrum of solid picene (C22H14)

Recently, Mitsuhashi et al observed superconductivity with a transition temperature up to
18 K in potassium doped picene (C22H14), a polycyclic aromatic hydrocarbon compound
(Mitsuhashi et al 2010 Nature 464 76). Theoretical analysis indicates the importance of
electron–phonon coupling in the superconducting mechanisms of these systems, with different
emphasis on inter- and intra-molecular vibrations, depending on the approximations used.
Here we present a combined experimental and ab initio study of the Raman and infrared
spectrum of undoped solid picene, which allows us to unambiguously assign the vibrational
modes. This combined study enables the identification of the modes which couple strongly to
electrons and hence can play an important role in the superconducting properties of the doped
samples.