INTERMOLECULAR AND INTRAMOLECULAR ENERGY TRANSFER IN GAMMA-IRRADIATED ALKYLBENZENES AND RELATED MIXTURES.
From radiolysis studies of various hydrocarbon mixtures (principally cyclohexane-benzene), intermolecular energy transfer has been proposed to explain deviations of product yields from those expected on the basis of noninteraction of constituents of the mixtures (1, 2). Similarly, intramolecular energy transfer from alkyl group to phenyl group has been proposed to explain low radiolysis product yields from alkylbenzenes (3-5). In this study, hydrogen yields for a series of alkylbenzenes have been measured in an effort to determine the effect of side-chain length on intramolecular energy transfer. These data, in addition to hydrogen yields measured for related twocomponent hydrocarbon systems, provide a basis for comparison of intermolecular and intramolecular energy transfer.
THE RADIOLYSIS OF THE XYLENE ISOMERS AND ETHYLBENZENE
The G-values for the formation of H/sub 2/ and CH/sub 4/ in the Co/sup 60/ gamma radiolysis of the xylene isomers and ethylbenzene were compared. The presence of iodine does not affect G/sub H2/, but reduces G/sub CH4/ a limiting value. For p-xylene, G/sub G2/ and the unscavengeable CH/sub 4/ yield are independent of temperature from 20 to 110 deg C, whereas the total CH/sub 4/ yield increases six-fold over this range. The H/sub 2/ and CH/sub 4/ yields are greatiy reduced in the solid state, and in the liquids state benzene shows a protective effect on the yields of both gases. The formation of CH/sub 4/ and C/ sub 2/-hydrocarbons was compared with the C/sub 6-/ and C/sub 7-/products for p- xylene and ethylbenzene, and isomerization is shown to occur to a negligible extent. The production of high-molecular-weight products was measured for the xylenes, and is independent of dose rate and temperature for liquid p-xylene, but is decreased in the solid state. The results are qualitatively consistent with the reactions of radicals and excited molecules. (auth)
On luminescence decay times and their relation to mechanisms of energy transfer in radiation chemistry of liquids
Luminescence against time curves, obtained by a newly developed technique, are given. Decay times of luminescence processes in mixed cyclohexane + benzene scintillator systems (with air present) lie in the range around 2 x 10/ sup -9/ sec. Addition of benzene to a cyclohexane solution of p-terphenyl causes a sharp rise in the decay time to a maximum at low benzene concentrations. The decay time is attributed tentatively to the energy transfer process from the lowest excited state. The estimated fraction of such low excited states transferring excitation to the scintillator is only 0 04 to 0.08. On the other hand, the scintillator appears also to quench the excited solvent. With the preliminary data at hand, the luminescence decay times are used as a tool for interpretation of the mechanism of protection in radiolysis of mixed liquid systems. (auth)