Valence one-electron and shake-up ionization bands of polycyclic aromatic hydrocarbons. I. Benzene, naphthalene, anthracene, naphthacene, and pentacene

The valence ionization bands of benzene and of polyacenes ranging from naph thalene to pentacene have been entirely assigned by means of one-particle G reen's function calculations, performed using the third-order algebraic-dia grammatic construction [ADC(3)] scheme and series of basis sets of improvin g quality. For the sake of consistency, the computations are based on corre lated (DFT/B3LYP) rather than uncorrelated geometries. Ionization bands per taining to pi -orbitals are subject to a severe shake-up contamination at a lready quite low binding energies (e.g., down to 8.0 eV in the case of pent acene). In sharp contrast, the orbital picture of ionization holds to a muc h greater extent within the sigma -band system (e.g., for pentacene, up to binding energies of 14.6 eV). Despite the intricacy of ionization bands, an d, possibly, vibrational complications, ADC(3) spectra consistently match p hotoionization measurements up to the inner-valence region, where the orbit al picture completely breaks down. (C) 2001 American Institute of Physics.