MODELING OF LINEAR-ENERGY-TRANSFER EFFECTS ON TRACK CORE PROCESSES INTHE RADIOLYSIS OF WATER UP TO 300 DEGREES-C

Deterministic diffusion-kinetic modelling of the radiolysis of water b y low linear energy transfer (LET) radiation in terms of our recently formulated extended spur diffusion model (J. Phys. Chem., 1995, 99, 11 464) has been applied to high LET radiation for 20 eV nm(-1) < LET < 7 0 eV nm(-1) up to 300 degrees C for a cylindrical track. The calculati ons show that an increase in LET accelerates the decay of the radicals e(aq)(-) and (OH)-O-., and the formation of the molecular products H- 2 and H2O2 and increases the extents of the main track reactions. This results in changes in the chemical yields (g-values), i.e., a decreas e in g(e(aq)(-)) and g((OH)-O-.) and an increase in g(H-2) and g(H2O2) , with increasing LET over the whole temperature range. For a given hi gh LET an increase in temperature results in a marked increase in g((O H)-O-.) and g(H-2), a small increase in g(e(aq)(-)) and a slight rise and fall in g(H2O2). These changes are largely accounted for by the di fferent temperature dependences of the various radical-radical reactio ns. The temperature dependences of these g-values decrease with increa sing LET. Reasonable agreement between modelling and experiment allows estimates to be made of the g-values for fast neutron radiolysis of w ater.