Dynamics of hot-electron transfer in oriented methyl halides on GaAs(110)

Abstract

The ordered molecular orientation of CH3X (X = Cl, Br and I) on GaAs(110) has been studied by angle-resolved time-of-flght (TOF) spectra of methyl fragments ejected by dissociation due to photoinduced electron transfer processes. A hot electron, produced in the substrate by UV irradiation, induces scission of CX bond in a manner similar to gas phase dissociation electron attachment (DEA). The methyl fragments ejected from a 1 ML layer have a unique angular distribution peaked about −45° ± 5° in the [01] direction defined by the GaAs(110) surface. The dynamics of electron transfer reactions in these systems, including the wavelength (193, 248 and 351 nm) dependence of the DEA reaction and the dependence of the dissociation cross section on the different methyl-halide molecules are discussed. The molecular orientation has been probed by near-edge X-ray adsorption fine structure (NEXAFS) experiments which indicate that the tilted orientation of absorbed molecules accounts for the angular distribution of methyl fragments ejected from hot-electron transfer reactions in these systems.