Experimental and Theoretical Study on the Ethane and Acetylene Formation from Electron Irradiation of Methane Ices

Abstract

In this work we present an experimental and theoretical study on the formation of ethane and acetylene from solid me thane condensed at 20 K and irradiated with a 500 - 3000 eV electron beam. The experiments were monitored with Thermal Desorption Spectroscopy. We observe that the electron irradiation induced a dehydrogenation of methane and a consequent formation of CH x (x = 1, 2, 3) fragments. Furthermore, in the solid during irradiation, a simple recombine tion reaction in the solid between two adjacent CH x molecules may form HC≡CH, H 2 C=CH 2 , and H 3 C-CH 3 with a triple, double, and single carbon-carbon bond, respectively. The formed amount of ethane and acetylene increases with irra diation time and reaches a saturation value.