FORMATION OF TRANSLATIONALLY HOT ETHENE BY DISSOCIATIVE ELECTRON-CAPTURE OF ADSORBED 1,2-DICHLOROETHANE

Irradiation of sub-monolayer and 4 layers of adsorbed 1,2-dichloroetha ne (DCE) on Cu(111) at 110 K with a pulsed 2 keV electron beam causes hot ethene desorption with translational temperatures of 2350 +/- 100 K (sub-monolayer), and 2540 +/- 200 K and 320 +/- 50 K (4 layers). DCE undergoes electron attachment from hot secondary electrons, dissociat ing to form a short-lived ClCH2CH2 radical which decomposes, generatin g the high temperature (2350 and 2540 K) ethene. The translational mot ion is thought to come from part of the heat liberated in the formatio n of the Cu-Cl bond. The 320 K peak is assumed to arise from radical d ecomposition at the surface of DCE crystallites.