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 82.3 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 repulsive dipole interaction between adsorbed K atoms. At theta(k) < 1 ML, H-atoms are adsorbed and bound to the K adatoms on MgO(100), forming the H-K-O species. On multilayer K-covered surfaces, two hydrogen desorption peaks, alpha and alpha', were observed due to the thermal decomposition of two possible bulk hydrides formed beneath the surface. The beta peak in hydrogen desorption is probably related to the surface-adsorbed hydrogen species. In addition, hydrogen diffusion into the bulk during H-atom adsorption or thermal annealing has been observed. (C) 1997 Elsevier Science B.V.