ELECTRON-ENERGY LOSS INVESTIGATIONS ON LEAD PHTHALOCYANINE

Polycrystalline lead phthalocyanine films have been investigated by transmission electron energy loss spectroscopy using 50 keV electrons. The energy loss spectrum was measured in the range 1-37 eV. From the measured spectrum the energy-dependent energy loss function Im(-epsilon--1) is derived. The dielectric function, optical constants and n(eff)(E) are computed using Kramers-Kronig analysis and well-known formulae. The spectrum of valence electronic excitations is interpreted in terms of pi --> pi* and sigma --> sigma* transitions of the individual molecules and in terms of the collective oscillation of the valence electron ensemble (sigma + pi plasmon).