Some correlations of aromatic decomposition G values

Abstract

A Ganguly-Magee diffusion model, with modifications, has been set up for the production of hydrogen in the radiolysis of benzene; the experimental and theoretical dependence of G(H2) on the L.E.T.2 of the radiation have been correlated. The mechanism proposed is the interaction of two excited molecules in competition with collisional deactivation. For a range of values of * Chemistry Division, A.

Diffusion−Kinetic Modeling of the γ-Radiolysis of Liquid Cycloalkanes

“…However, the nature of the model lets the spatial distributions relax in a nonprescribed manner; cf. the prescribed diffusion treatment frequently used to model spur kinetics. − At later times in the evolution of the spur, a non-Gaussian profile is possible for the spatial distribution of reactive species. Figure shows the temporal variation of the spatial distributions for cyclopentyl, cyclohexyl, and cyclooctyl radicals in their respective media.…”

“…Since these reactions are nearly diffusion limited, the appropriate value in each of the cycloalkanes was obtained by a viscosity scaling of the rate coefficients in water . The rate coefficient for the cross combination reactions of cycloalkyl radicals with H atoms was obtained from the relationship k (R+H) = 2[ k (R+R) k (H+H)] 1/2 . − Hydrogen atom reactions with the molecular medium are the only reactions in which there is considerable uncertainty in the rate coefficients. The coefficients for cyclopentane and cyclohexane were determined to be 3 × 10 7 M -1 s -1 using ESR techniques .…”

“…A considerable amount of knowledge of the radiation chemistry of hydrocarbons has been obtained from studies examining the end products formed , and the short time chemistry of the transient ions, excited states, and radicals − and stochastic Monte Carlo simulations − of the radiolysis of hydrocarbons have been made. These calculations have been hindered by uncertainties of the chemical processes and the lack of information about the physical aspects of the energy deposition by ionizing particles.…”

Role of the Low-Energy Excited States in the Radiolysis of Aromatic Liquids

“…The yield of H 2 in the radiolysis of liquid benzene and pyridine varies significantly with the type of radiation and on the linear energy transfer (LET = −d E /d x ). , In general, G (H 2 ) increases with LET due to the increased significance of the intratrack bimolecular processes. Burns has suggested that H 2 is produced in the radiolysis of benzene as a result of the reaction between two singlet excited state molecules. , The implied intermediate in this process is a high-energy singlet state that is more likely to decompose to H 2 than the S 1 excited state. A study of the fluorescence intensity dependence on LET in the heavy ion radiolysis of benzene has provided strong support for the role of the excited singlet state in H 2 production. , A logical assumption of this observation is that reaction between singlet excited states is facilitated in the radiolysis of all the aromatic compounds studied here because of the nonhomogeneous nature of energy deposition in radiolysis as compared to the homogeneous deposition of energy in photolysis.…”