Determination of the effective surface Debye temperature of Ni(110) using inverse photoemission spectroscopy

We have used k -resolved inverse photoemission spectroscopy to measure the temperature-dependent intensity of radiative transitions into unoccupied electronic states of Ni(110) along its Γ Y ¯ high-symmetry line in the surface Brillouin zone. Our measurements yield a strong temperature dependence of a transition into an unoccupied crystal-derived surface state. This temperature dependence weakens as the position of the state moves away from the Y ¯ high-symmetry point. We use a Debye–Waller model to interpret the intensity attenuation of the direct transitions with increasing temperature. From our results of a transition into the sp -derived bulk state observed at ∼ 1 eV above the Fermi level, we estimate the effective surface Debye temperature of Ni(110) to be 240 ± 20 K.