INVESTIGATION OF UNOCCUPIED ELECTRON-STATES AND DETERMINATION OF THE ELECTRON-AFFINITY OF PBS (100) BY INVERSE-PHOTOEMISSION SPECTROSCOPY

Isochromatic spectra of inverse photoemission from PbS (100) were dete rmined at photon energies 3.1, 3.9, and 4.9 eV and for exciting-electr on energies from zero to 10 eV. The dominant contribution to the inver se photoemission spectra of lead sulfide was made by indirect transiti ons and the spectra manifested the effects of the integral density of unoccupied states. Isochromatic inverse photoemission spectroscopy was used to find the electron affinity of PbS (100): e(chi)=3.5+/-0.2 eV.