Effect of Electrical Fields and Density in the Radiolysis of Ethane

Abstract

The gamma-ray radiolysis of C2H6–C2D6–NO and CH3CD3−NO mixtures has been investigated as a function of applied electrical field. In the saturation current region, a number of products resulting from the decomposition of neutral excited molecules increase about fivefold before the onset of secondary ionization while several other products, which can be ascribed to ion molecule reactions, remain essentially unchanged. The modes of decomposition of the excited ethane molecules formed by electron impact, as derived from the applied field experiments, are the same as those observed in the vacuum ultraviolet photolysis at 1470 and at 1236 Å. From the isotopic composition of the products it could be deduced that the average energy transferred to ethane by electron impact is greater than 10 eV. A value of 0.5 was derived for the number of neutral excited molecule decompositions per ion pair. A change in density has a pronounced effect on the product distribution, both in the photolysis at 1236 Å and the radiolysis. In the radiolysis, several of the changes can be ascribed to the diminishing fragmentation of the parent ion with an increase in density. However, products resulting from the fragmentation of the neutral excited ethane molecules formed in the radiolysis also show a strong dependence on density because of collisional stabilization of the primary fragments and of the products formed in secondary reactions. For instance, the propane which could be entirely ascribed to the insertion reaction CH2+C2H6+M→C3H8+M increases with an increase in density in the photolysis as well as in the radiolysis.