Photoionization of Propylene at 1236 Å. Reactions of C3D6+ with Added Alkanes

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Abstract
C3H6–C3D6–O2 mixtures have been irradiated at 1236 Å (10 eV) in the presence and absence of an applied electrical field with the purpose of obtaining information about the ion—molecule reaction mechanism. On the basis of a number of observations, it was concluded that the product, propane, can be ascribed to the reaction C3mH6m++C3H6→C3mH6m−2++C3H8 (m≥2). When alkanes (RH2) whose ionization energy is larger than 10 eV are added to C3D6—O2 mixtures, the following H2−‐transfer reaction occurs: C3D6++RH2→CD3CDHCD2H+R+ . Relative rates of the reaction of C3D6+ with various alkanes have been determined and compare favorably with values obtained in a recent radiolytic study in which cyclopentane‐d10 was used as a source of C3D6+ ions. The optimum experimental conditions, under which meaningful saturation ion currents can be obtained in the photoionization apparatus, are discribed. On the basis of measurements of the saturation ion current in NO and propylene at 1236 Å, values of 0.197 and 0.208 were obtained for the photoionization efficiencies of C3H6 and C3D6, respectively. The latter measurements made it possible to express the products in the number of molecules formed per ion pair as well as in the number of molecules formed per quantum absorbed.