Electron-transfer–mediated and direct surface photochemistry:CH3Cl on Ni(111)

Direct photolysis and electron-induced fragmentation of ${\mathrm{CH}}_3$Cl on a Ni(111) surface was observed in time-of-flight studies using 193-nm radiation. With 248-nm radiation, only electron-induced fragmentation was observed. With 351-nm radiation no fragments were observed. The electron-induced process was surface specific, occurring within a limited adsorbate thickness determined by the penetration depth of the excited substrate electrons into the adsorbate. Cross sections are reported as a function of coverage.