SUBSTRATE MEDIATED AUTOIONIZATION OF BENZENE ON GRAPHITE

Benzene adsorbed on graphite is found to increase the photoelectric yi eld even below the ionization energy of benzene. A two step model for this substrate mediated autoionization channel is proposed. After intr amolecular pi-->pi excitation an Auger deexcitation process may pump the electron from the pi level into the vacuum. An adsorbate induced resonance 5.4 eV above the Fermi level is found to promote the yield e nhancement. Implications for soot particle characterization are discus sed.