INVERSE-PHOTOEMISSION SPECTRA OF THE NB(111) SURFACE

The k-resolved inverse photoemission spectra of the single crystal Nb( lll) surface were measured with normally incident electrons in the ene rgy range 21-52 eV. Unoccupied electronic states were studied along th e Gamma-P-H symmetry direction in the Gamma HPN symmetry plane. The ex perimental results are in a reasonable agreement with the energy-band calculations made by the linear muffin-tin orbital method with the ato mic-sphere approximation (LMTO-ASA). Two characteristic features appea red in the spectra at the fixed emitted photon energy. First, we obtai ned an enhancement of the inverse photoemission intensity at the plasm a frequency energy of 19.7 eV, and second an enhanced emission at 31.0 eV corresponding to the fluorescence decay of the Nb 4p core holes. ( C) 1998 Elsevier Science B.V. All rights reserved.