PHOTON ENERGY-DEPENDENCE OF VALENCE-BAND PHOTOEMISSION AND RESONANT PHOTOEMISSION OF POLYSTYRENE

The photon energy dependence of valence band photoemission from polyst yrene thin films has been investigated using synchrotron radiation in the range 150-450 eV, covering the carbon K edge. Six Valence peaks we re found which show an energy dependence that can be qualitatively exp lained by the relative contributions of 2s and 2p atomic orbitals to t he molecular orbital photoemission cross-section. The experimental res ults are generally in agreement with valence effective Hamiltonian (VE H) calculations in the literature. In the vicinity of the carbon Is ab sorption edge, there is a strong enhancement of the valence band emiss ion because of resonant photoemission, reported here in organic polyme rs for the first time. The relative contribution of spectator and part icipator decay channels varies among the valence orbitals, in a way th at can be associated with the spatial distribution of the benzene-deri ved molecular orbitals involved in the resonance transition.