Photon energy dependence of valence band photoemission and resonant photoemission of polystyrene

The photon energy dependence of valence band photoemission from polystyrene thin films has been investigated using synchrotron radiation in the range 150-450 eV, covering the carbon K edge. Six Valence peaks were found which show an energy dependence that can be qualitatively explained by the relative contributions of 2s and 2p atomic orbitals to the molecular orbital photoemission cross-section. The experimental results are generally in agreement with valence effective Hamiltonian (VEH) calculations in the literature. In the vicinity of the carbon Is absorption edge, there is a strong enhancement of the valence band emission because of resonant photoemission, reported here in organic polymers for the first time. The relative contribution of spectator and participator decay channels varies among the valence orbitals, in a way that can be associated with the spatial distribution of the benzene-derived molecular orbitals involved in the resonance transition.