Nanosecond proton pulse radiolysis of aqueous solutions. Part 2.—Improved measurements and isotope effects

Abstract

The use of a signal sampling and averaging technique has improved the time resolution of the measurements of G(e_aq^–) following irradiation of aqueous solutions by 3 MeV protons in a pulse of ca. 1 ns. The maximum measured G(e_aq^–) for pure water and for water containing concentrated scavengers for H⁺ ions and OH radicals was in all cases significantly higher than previously reported. The maximum G(e_aq^–) for a solution of both 1 mol dm^–3 OH^– and 2 mol dm^–3 ethanol in H₂O was 6.3. Except for this case values of G(e_aq^–) for solutions in D₂O were slightly higher than, or the same as, values for H₂O solutions. Analysis of the effect of pulse shape and detection response shows that the maximum signal occurs 3.5 ns after the start of the pulse. Comparison with results of diffusion kinetic modelling shows the observation to diverge even further from the predictions than is the case for low LET radiation.