In situ generation of ultrafast transient "acid spikes" in the 10B(n,α)7Li radiolysis of water

Highlights: • Monte Carlo track chemistry simulations are used to model the ¹⁰B(n,α)⁷Li radiolysis of water. • The in situ formation of H₃O⁺ renders the "native" He and Li recoil track regions very acidic. • The transitory acid pH response, or "acid spike" effect, is quantified as a function of time. • The pH remains near 0 at times less than 100 ps after which it gradually returns to 7 at ∼0.1 ms. • Calculations are extended to a cellular environment where the proton mobility is lower than in free water. • The implications of these "acid spikes" in BNCT and in hadrontherapy, are discussed briefly. Monte Carlo track chemistry simulations of the ¹⁰B(n,α)⁷Li radiolysis of water show that the in situ formation of H₃O⁺ by the two He and Li recoiling ions renders the native track regions temporarily very acidic. For these irradiating ions, the pH remains near 0 at times less than ∼100 ps after which the system gradually returns to neutral pH at ∼0.1 ms. These 'acid spikes' have never been invoked in water or in a cellular environment exposed to densely ionizing radiations. The question of their implications in boron neutron capture therapy and, more generally, in hadrontherapy, is discussed briefly.