Water radiolysis studied by positron annihilation

Hirade, Tetsuya  ; Oka, Toshitaka   

Positronium(Ps) formation in insulating materials can be explained by spur reactions at the terminal spur of the positron track, so-called positron spur. Ps formation time is probably about 1ps and the yields of Ps formation give information of the reactions of the reactive species in the terminal spur, such as the free excess electrons. Ortho-Ps annihilation lifetime is about 1-5ns by the pick-off annihilation in condensed materials. Hence the o-Ps reactions with reactive species are quite possible. The most important reactions are, probably, ortho-Ps oxidation and spin conversion by reactive species, such as OH radical. We are introducing what we can study for water radiolysis by use of positron annihilation methods.