Electron attachment to CF3Cl and CH3Cl on the surface and in the bulk of solid Kr

The formation of stable anions induced by the impact of 0-1.6 eV electrons on CF3Cl and CH3Cl condensed at the surface, and embedded within the bulk o f solid Kr is investigated by measuring charging of the doped Kr films. Eff ects of the Pt substrate and under- and over-layer coverage of these molecu les on the dissociative electron attachment and stable anion formation (SAF ) are studied in detail by varying the film thickness and the position of t he molecules within the film. Due to recent advances, we provide new and mo re reliable values of the absolute cross sections, sigma (SAF), for SAF. si gma (SAF) reaches a maximum of 2.1 x 10(-16) cm(2) at 0.6 eV for CF3Cl embe dded in solid Kr; for CH3Cl, this maximum is similar to 10(-16) cm(2) at 0. 2 eV. These values correspond to an enhancement of factors of 5 and 10, res pectively, relative to sigma (SAF) measured at the surface. The electron en ergy dependence of sigma (SAF) is also evaluated theoretically from calcula tions performed with the R-matrix formalism extended to include the influen ce of condensed-matter environments. By incorporating into the theory the b and structure of the solid and different values of the polarization induced into the medium by electron capture, we study the effect of these paramete rs on sigma (SAF). Comparison between experimental and theoretical sigma (S AF)'s allows us to analyze the gas-phase parameters that must be modified t o generate condensed-phase cross sections from gas-phase data and to discus s the effect of phenomena which are absent in the gas-phase (e.g., caging). (C) 2001 American Institute of Physics.