Formation of anionic excitations in the rare-gas solids and their coupling to dissociative states of adsorbed molecules.

Abstract

It is experimentally demonstrated that (electron plus exciton) core-excited resonances are formed by low-energy electron scattering in the Ar, Kr, and Xe rare-gas solids at 11.6\ifmmode\pm\else\textpm\fi{}0.2, 9.7\ifmmode\pm\else\textpm\fi{}0.2, and 7.7\ifmmode\pm\else\textpm\fi{}0.2 eV, respectively. These resonance states can be efficiently coupled with dissociative Rydberg anion states of adsorbed ${\mathrm{H}}_{2}$O, ${\mathrm{C}}_{2}$${\mathrm{D}}_{6}$, and ${\mathrm{C}}_{6}$${\mathrm{D}}_{6}$, but not with valence-dissociative states of adsorbed ${\mathrm{O}}_{2}$ or ${\mathrm{C}}_{6}$${\mathrm{D}}_{6}$. These resonances are revealed as narrow (full width at half maximum \ensuremath{\Delta}E=0.2--0.4 eV) enhancements in the dissociative attachment yields of the adsorbed molecular species, at incident electron energies just below that of exciton formation in the condensed rare gases. Above the exciton energies, in contrast, the dissociative attachment mechanism in the adsorbed molecules can be attenuated, or completely quenched. All observations are characterized as ``quasi-two-electron-jump'' processes due to sizable overlaps between the associated Rydberg orbitals.