Indium adsorption sites at Pd(100) surfaces studied by PAC spectroscopy

Abstract

Perturbed gamma gamma -angular correlation (PAC) experiments have been performed to study the occupation of different surface sites by 111In probe atoms at vicinal Pd surfaces with (100) terrace orientation. Within an isochronal annealing sequence In probes are observed to dwell in adatomic and substitutional step and terrace sites, in agreement with earlier experiments on Cu, Ag and Ni surfaces. The temperature dependence of the electric field gradient for 111In atoms occupying substitutional terrace sites deviates from the behaviour detected on Cu(100), Ag(100) and Ni(100) surfaces. The observed deviation in the low-temperature regime is attributed to the adsorption of hydrogen.