Track Effects in Radiation Chemistry: Production of HO2(.) within the Track Core in the Heavy-Particle Radiolysis of Water

Article abstract of DOI:10.1021/j100405a037

The radiation chemical yields of HO2(.) radicals produced by (1)H, (4)He, (7)Li, (9)Be, (11)B, (12)C, and (20)Ne ions having energies up to 35 MeV have been determined.At energies above 10 MeV the yield with protons approaches the value of 0.020 molecules/100 eV observed with fast electrons.The yield increases with increasing mass and decreasing energy of the irradiating particle and exceeds 0.2 molecules/100 eV for low-energy (9)Be, (11)B, (12)C, and (20)Ne ions.Extrapolation indicates an upper limit of 0.37 molecules/100 eV for more massive ions.We conclude that HO2(.) is produced mainly in the track core, so that HO2(.) production is a good probe of the dependence of core processes on particle characteristics.Comparison of the differencial yields observed for different particles having the same linear energy transfer (LET) shows that these yields are not strongly dependent on the irradiating particle.After correction for energy lost to ? rays, the LET dependence of the yield pertinent to the core is common to all of the particles studied, indicating that in this case the track has expanded to some extent before reaction occurs.