SUBSTRATE DEPENDENCE OF ELECTRON-STIMULATED O- YIELDS FROM DISSOCIATIVE ELECTRON-ATTACHMENT TO PHYSISORBED O-2

被引:78
作者
HUELS, MA
PARENTEAU, L
SANCHE, L
机构
[1] Medical Research Council Group in the Radiation Sciences, Faculté de Médecine, Université de Sherbrooke, Sherbrooke
关键词
D O I
10.1063/1.466329
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
We present measurements of O- electron stimulated desorption yields obtained under identical experimental conditions from 0.15 monolayers (ML) of O-2 deposited onto disordered substrates consisting of 4 ML of either Kr, Xe, C2H6, C2H4, N2O, CH3Cl, or H2O, all condensed on Pt (polycrystalline). The resulting O- yield functions, for incident electron energies below 20 eV, are compared to that obtained from the O-2/Kr solid; this allows us to assess the order of magnitude effects of the local substrate environment on dissociative electron attachment (DEA) via the (2) Pi(u), and gas phase forbidden (2) Sigma(g,u)(+) resonances of O-2(-). We note that, in addition to electron energy losses in the substrate prior to DEA to O-2 and past-dissociation interactions of the O- with the substrate molecules, charge or energy transfer from the O-2(-) transient anion to a substrate molecule, and capture of the incident electron into a dissociative anion resonance of the substrate molecule may contribute to a reduced O- yield from the physisorbed O-2. In the case of O-2 deposited on amorphous ice, we find that the O- signal from DEA to O-2 is completely absent for electron energies below 14 eV; we attribute this to a complete quenching of the dissociative O-2(-)((2) Pi(u), (2) Sigma(+)) resonances by the adjacent water molecules.
引用
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页码:3940 / 3956
页数:17
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