DISSOCIATIVE ATTACHMENT FROM MONOCHLORINATED HYDROCARBONS IN THE GAS-PHASE

Gas phase measurements of the dissociative attachment (DA) process pro vide fundamental data useful for the interpretation of studies incorpo rating molecules on surfaces and in films. In this report, we review r ecent DA studies in a series of monochlorohydrocarbons to examine the role of the hydrocarbon framework, or ''substrate'', to which the Cl i s attached. We find that the peak cross section decreases roughly expo nentially as the vertical attachment energy to form the temporary nega tive ion increases. We consider also the problem of measuring the smal l cross section of methyl chloride and show that observation of the te mperature dependence of the process provides information about the cro ss section. We discuss briefly the recent theoretical studies of this process in methyl chloride. Finally, we examine the effect of placing a region of unsaturation, i.e., a double bond, in a location remote fr om the C-CI bond and show that this enhances the DA cross section, pro viding evidence for intramolecular transfer of the electron.