Photochemistry of acetylene at 1849 A

It is pointed out that the photochemistry of acetylene in the 1500-2000 A region at low pressure, particularly the quantum yield of C2H production and the reactions of C2H with H2 and hydrocarbons, is important in understanding the photochemistry of Jovian and Titan atmospheres. The present investigation was initiated to obtain information on these issues. The 1849 A light source used in the study was a sealed quartz tube containing a drop of Hg and 2 torr of Ar excited by a microwave generator. The lamp was attached to a Pyrex reaction cell. The amount of diacetylene produced was measured on the basis of absorption near 1650 A. Reaction mixtures of acetylene with N2, He, C2H6, or C3H8 were prepared. Attention is given to the absorption cross section, the photolysis of acetylene, and the photolysis of acetylene in the presence of other gases. It is found that the photochemical process of acetylene at 1849 A may represent that of acetylene in the Titan atmosphere.