Chemistry Guest Seminar

"The Role of Low-Energy Electron in High Energy Radiolysis"

Prof. Chris R. Arumainayagam Homepage

Studies of low-energy electron-induced processes in nanoscale thin films serve to elucidate the pivotal role that secondary electrons play in high-energy radiation-induced chemical reactions in condensed matter. While electron-stimulated desorption (ESD) experiments conducted during irradiation have yielded vital information relevant to primary or initial electron-induced processes, analyzing the products following low-energy electron irradiation can provide new insights into radiation chemistry. We have used post-irradiation temperature-programmed desorption to identify labile radiolysis products as demonstrated by the first identification of methoxymethanol as a reaction product of methanol (CH₃OH) radiolysis. Although low-energy electron-induced oligomerization reactions have been previously reported for molecules such as thiophene and cyclopropane, our electron-induced studies of CCl₄ represent the first study to specifically identify the products of such reactions, demonstrating the utility of post-irradiation temperature programmed desorption experiments to study the radiation chemistry of condensed matter. Results of post-irradiation studies have been used not only to determine the identity of radiolysis products, but also to determine the dynamics of electron-induced reactions. By comparing our post-irradiation results to previous electron stimulated desorption studies of anion production during irradiation of condensed CF₂Cl₂ and CF₃I, we have examined the relationship between desorbed anions and retained radicals during dissociative electron attachment in the condensed phase. Relative yields of radiolysis products quantified by post-irradiation surface analysis, at low and high incident electron energy, may be used to ascertain whether the formation and decay of temporary negative ion resonances is the dominant mechanism for secondary electron-induced damage associated with radiolysis.