Low energy electron induced decomposition of phosgene on Ag(111)

The decomposition, induced by low energy electrons (0–23 eV), of adsorbed phosgene (Cl2CO) on Ag(111) has been studied using temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS). The electron induced decomposition (EID) products are surface Cl(a) and gas phase CO(g). There is no electron stimulated desorption (ESD) of molecular Cl2CO or atomic Cl. The evolution of CO during EID is readily monitored with a mass spectrometer. The electron kinetic energy threshold for the EID of Cl2CO is near zero eV. The EID cross section is in the range of 10−16–10−15 cm2 and increases with incident electron energy. The EID process is attributed to dissociative electron attachment (DEA) in which incident electrons attach themselves to adsorbed Cl2CO forming Cl2CO− ions as intermediates that dissociate. These results are compared with the photodissociation of Cl2CO on Ag(111).