Electron bombardment enhancement of the reactivity of graphite with atomic hydrogen: Thresholdhyphen;like effects

摘要

The chemical reactivity of graphite surfaces exposed to atomic hydrogen is enhanced under electron bombardment by an enhancement factor egr;prime; which depends on the incident electron energy. A sharp thresholdhyphen;like increase in egr;prime; is observed for crystalline graphite at an energyEthwhich depends on the angle of incidence thgr; of the electron beam with respect to the basalhyphen;plane surface normal. Measurements of the dependence ofEthon thgr; are reported here. Model calculations indicate that the effect is due either to a direct excitation of the electronic transition responsible for the enhancement or to plasmon production which subsequently drives the transition. Further experiments are suggested to distinguish between these mechanisms.