IMAGE-POTENTIAL STATES ON NI(111) MEASURED BY INVERSE-PHOTOEMISSION SPECTROSCOPY

Angle-resolved inverse-photoemission (IPE) spectroscopy has been used to examine the unoccupied electronic states of the Ni(111) surface. The dispersion with parallel momentum of all observed features is more rapid than reported in an earlier IPE study. Bulk related features agree well with direct transitions predicted by a combined interpolation calculation of the Ni band structure. The dispersion of the n = 1 image-potential state is free-electron-like with an effective mass of (1.05 +/- 0.05)m(e). This is in good agreement with recent two-photon photoemission results as well as theoretical calculations using a phase-analysis model, but differs considerably with the earlier angle-resolved IPE measurements.