XENON ADSORPTION ON NIAL(110)

Adsorption of Xe on NiAl(110) at 50 K has been studied by UPS, TDS and LEED. At low coverage (θ{symbol} ≤ 0.3 ML) first order kinetics is observed with an activation energy of desorption of 22 kJ mol-1. Above θ{symbol} = 0.5 ML a zeroth-order desorption kinetics is observed. This is suggestive of desorption from 2D solid Xe islands, in agreement with a first-order phase transition during population of the first monolayer. Together with the appearance of the zeroth-order desorption kinetics a Xe-induced LEED pattern suggests the formation of Xe islands of hexagonal structure and a Xe-Xe interatomic distance of 4.48 Å. The Xe 5p1/2 and 5p3/2 photoemission peaks grow at 6.05 and 7.27 eV binding energy, independent of coverage. The 5p3/2 signal exhibits a resolved mi-splitting only at coverages which correlate with the occurrence of the zeroth-order desorption kinetics and the appearance of the Xe induced LEED pattern, i.e. the formation of 2D Xe islands, leading to the conclusion that the 5p3/2 splitting observed is due to lateral interactions between the adsorbed Xe atoms rather than crystal-field effects. © 1990 Pergamon Press plc.