THE EFFECTS OF DIFFERENT SUBSTRATES ON THE ELECTRON-STIMULATED DESORPTION DYNAMICS OF O- FROM PHYSISORBED O-2

We report condensed phase measurements of kinetic energy (E-k) distrib utions of O-, produced by dissociative electron attachment (DEA) at 6 eV incident electron energy; they are obtained under identical experim ental conditions from submonolayer quantities of O-16(2) deposited on disordered multilayer substrates of O-18(2), Ar, Kr, Xe, CH4, and C2H6 , all condensed at 20 K on polycrystalline platinum (Pt). The results suggest that the desorption dynamics of O- DEA fragments is, in part, determined by large angle elastic scattering of O- prior to desorption , as well as the net image charge potential (E-p) induced in the conde nsed dielectric solid and the Pt metal, The measurements also indicate that, particularly at small Kr substrate thicknesses, the E-p may not necessarily be uniform across the surface, but may fluctuate due to s urface roughness. Thus, in addition to energy losses in the substrate prior to, and during, DEA, these effects may influence the dissociatio n dynamics of the O-2(-) resonance itself, as well as the desorption o f the DEA O- fragment. (C) 1997 American Institute of Physics.