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.
Gases produced during gamma irradiation of the monobutylbenzenes.
The four isomeric monobutylbenzenes have been γ-irradiated and the gases produced have been analyzed by gas chromatography. The most abundant gaseous product is hydrogen. The relative yields of hydrogen indicate a relationship to the number of benzylic hydrogens in the starting butylbenzene. The most abundant gaseous hydrocarbon products are ${\rm C}_{3}\text{'}{\rm s}$ for n-butylbenzene, C1 and ${\rm C}_{2}\text{'}{\rm s}$ for sec-butylbenzene, ${\rm C}_{3}\text{'}{\rm s}$ and C1 for iso-butylbenzene, and C1 for tert-butylbenzene. The gaseous products indicate that reactions forming benzylic intermediates predominate.
Scintillating Solutions Containing Heavy Elements
The use of heavy metals in scintillators (excited by high energy) is limited by two factors: 1) Such materials are very often not sufficiently soluble in solvents exhibiting considerable energy transfer, and 2) they generally quench the excitation energy of the solution and thereby decrease the fluorescent output. The latter effect was found to be due mostly to a quenching of the excited molecules of the solvent which are responsible for transferring energy, and to a lesser extent to the quenching of the fluorescent molecule, although this process also occurs. To circumvent the first difficulty one uses solvents with better solubilities for the metal compounds, but the choice is limited because of poor energy transfer characteristics of many of them. One of the best solvents found up to now is p-dioxane, which exhibits considerable energy transfer and shows better solubility properties than most of the other energy transferring solvents. Another means of overcoming difficulties of solubility is to use organic solvents favorable from the standpoint of solubility, but not so favorable from that of energy transfer. One can effectively induce considerable energy transfer in many of these solutions and thus produce high energy excited fluorescence by adding a relatively small amount, of the order of 10 per cent, of an effective liquid solvent (one which shows energy transfer).