Photolysis of Ethane at 11.6–11.8 eV

Abstract

The photolysis of ethane, carried out with an argon resonance lamp, has been reinvestigated with the related purposes of (1) measuring quantum yields of all fragments formed in the dissociation of excited ethane and (2) associating these fragments with the primary processes occurring in the photolysis of ethane. These and their relative abundances are C2H6*→C2H6+, 5% →CH4+CH2, 16% →C2H5+H, 41% →C2H4+H2, 26% →CH3+CH3, 15%. These results are compared with conclusions reached in earlier studies on the photolysis of ethane with xenon and krypton lamps in order to determine the effect of energy on the relative probabilities of the primary processes. It is found that direct bond scission increases in importance with increasing energy, while processes involving rearrangement decrease in importance. The radical and molecular fragments formed in the dissociation of excited ethane were determined by (a) analyzing the products formed in C2H6–C2D6–NO (1:1:0.1) mixtures and (b) C2D6in the presence of H2S, which scavenges free radicals to form isotopically unique hydrocarbon products, and (c) C2H6 in the presence of C3D6, which scavenges H atoms to form propyl radicals, which in turn react with radicals in the system to form characteristic products. Such experiments, as well as quantum yield determinations, were also carried out at the krypton and xenon lines.