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

Abstract

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 of solid Kr is investigated by measuring charging of the doped Kr films. Effects of the Pt substrate and under- and over-layer coverage of these molecules on the dissociative electron attachment and stable anion formation (SAF) are studied in detail by varying the film thickness and the position of the molecules within the film. Due to recent advances, we provide new and more reliable values of the absolute cross sections, σSAF, for SAF. σSAF reaches a maximum of 2.1×10−16 cm2 at 0.6 eV for CF3Cl embedded in solid Kr; for CH3Cl, this maximum is ∼10−16 cm2 at 0.2 eV. These values correspond to an enhancement of factors of 5 and 10, respectively, relative to σSAF measured at the surface. The electron energy dependence of σSAF is also evaluated theoretically from calculations performed with the R-matrix formalism extended to include the influence of condensed-matter environments. By incorporating into the theory the band structure of the solid and different values of the polarization induced into the medium by electron capture, we study the effect of these parameters on σSAF. Comparison between experimental and theoretical σSAF’s allows us to analyze the gas-phase parameters that must be modified to generate condensed-phase cross sections from gas-phase data and to discuss the effect of phenomena which are absent in the gas-phase (e.g., caging).

Photoinduced Fragmentation of Multilayer CH3Br on Cu/Ru(001)

“…These values are more than two orders of magnitudes higher than the equivalent DEA cross section in the gas phase. 25 One may conclude that there is an interplay between stabilization effects and escape probability from a cage of the dissociated fragments that dictates the net probability for the DEA process of an embedded CH 3 Br molecule. Voids in the amorphous solid that reduce the perfect cage structure may also reduce the cage effect in favor of enhancing DEA.…”

“…2,6,25 These ions generate electric field around them and are attracted to their image charge inside the bulk metal underneath. To caracterize the dissociation products embedded inside the multilayer structure after irradiation and to probe the multilayer restructure during the diffusion of the Br -ions, a set of ∆ -TPD spectra were recorded under similar condition as for the ∆p-TPD.…”

Steric Effect in Electron−Molecule Interaction

“…Studies in this field have included inter-and intramolecular electron transfer, 6 transmission 7-9 conduction within and through molecules, 10,11 and dissociative electron attachment (DEA) processes. [12][13][14] Recent interest in molecular electronics has brought the basic science in this field closer to modern technology than ever before. [8][9][10][11] Here we present, for the first time, the phenomenon of molecular orientation dependent electron-molecule interaction.…”

Dissociative electron attachment to molecules in the gas phase and in rare gas solids

“…The conceptually simplest such environment may well be with target molecules embedded in a rare gas lattice. In two tour de force experiments, Nagesha and Sanche 1 and Fabrikant et al 2 reported absolute cross sections for production of stable negative ions in CF 3 Cl and CH 3 Cl, respectively, within a solid lattice of krypton. In more recent work, 3 these authors have reported new and more reliable values of the absolute cross sections for these two species both within and on the surface of the rare gas film.…”

“…In two tour de force experiments, Nagesha and Sanche 1 and Fabrikant et al 2 reported absolute cross sections for production of stable negative ions in CF 3 Cl and CH 3 Cl, respectively, within a solid lattice of krypton. In more recent work, 3 these authors have reported new and more reliable values of the absolute cross sections for these two species both within and on the surface of the rare gas film. The measurements were accompanied 2,3 by theoretical DEA cross sections obtained by using a semiempirical R-matrix method 4 extended to incorporate the effects of the condensed matter environment.…”