Metastable helium atom scattering from Ni(1 1 0) surface

The survival probability (SP) of metastable helium atoms (He ) during scattering from the clean, alkalated and oxygenadsorbed Ni(1 1 0) surfaces has been examined in the kinetic energy range of 50±400 meV. The measurements were carried out using a time-of-¯ight technique and a pulsed-discharge type metastable helium atom source. The SP is nearly constant for a kinetic energy (Ekin) of 50±100 meV and decreases exponentially with the increase in Ekin at 100±400 meV. It has been shown that the SP at Ekin ˆ 100ÿ400 meV depends on the repulsive part of the He -surface interaction potential. # 2001 Elsevier Science B.V. All rights reserved.