INTERACTION OF ATOMIC-HYDROGEN WITH POTASSIUM ON MGO(100)

The adsorption of potassium and its interaction with hydrogen atoms on MgO(100) have been studied by thermal desorption spectroscopy (TDS). The desorption energy of adsorbed K atoms was found to decrease from 8 2.3 to 78.5 kJ mol(-1) with increasing potassium coverage in the range of theta(k) less than or equal to 1 ML, which is attributed to the re pulsive dipole interaction between adsorbed K atoms. At theta(k) < 1 M L, H-atoms are adsorbed and bound to the K adatoms on MgO(100), formin g the H-K-O species. On multilayer K-covered surfaces, two hydrogen de sorption peaks, alpha and alpha', were observed due to the thermal dec omposition of two possible bulk hydrides formed beneath the surface. T he beta peak in hydrogen desorption is probably related to the surface -adsorbed hydrogen species. In addition, hydrogen diffusion into the b ulk during H-atom adsorption or thermal annealing has been observed. ( C) 1997 Elsevier Science B.V.