High-resolution photoemission study of the (Y)over-bar surface state on Ag(110)

We report a high-resolution study of the 'Shockley-type' occupied surface s tate residing in the projected L-2'-L-1 gap around the (Y) over bar point o f the surface Brillouin zone. Along <(Gamma Y)over bar> on Ag(110) this ban d shows a parabolic dispersion with kll, the surface wave vector. The effec tive mass is m*/m = 0.26 +/- 0.02 and the bottom of the parabola at (Y) ove r bar shows a linear dependence on sample temperature according to E-0 = -( 106 +/- 5) meV + (0.17 +/- 0.01 meV/K)T. In consequence, the surface band g ets empty above T = 624 +/- 37 K. These numbers give a quantitative interpr etation of strong temperature effects observed earlier by other authors in second-harmonic spectra from Ag(110), where the fundamental light couples t he occupied surface state to an unoccupied surface state within the same pr ojected gap. From our data we derive a more precise value of its bottom ene rgy E-f = 1.66 +/- 0.02 eV above E-F at (Y) over bar. (C) 1999 Elsevier Sci ence B.V. All rights reserved.