Yield of the Fricke dosimeter irradiated with the recoil α and Li ions of the 10B(n,α)7Li nuclear reaction: effects of multiple ionization and temperature

Monte Carlo track chemistry simulations were used to investigate the effects of multiple ionization (MI) of water on the yields (<i>G</i>-values) of the ferrous sulfate (Fricke) dosimeter which was irradiated with low-energy α and lithium ion recoils from the ¹⁰B(<i>n</i>,α)⁷Li nuclear reaction as a function of temperature from 25 to 350 °C. Calculations were performed individually for 1.47 MeV α-particles and 0.84 MeV lithium nuclei with dose-average linear energy transfer (LET) values of ~196 and 225 keV/μm at 25 °C, respectively. The total yields were obtained by summing the <i>G</i>-values for each recoil α and Li ion weighted with its fraction of the total energy absorbed. At room temperature, our <i>G</i>(Fe³⁺) values calculated under aerated and deaerated conditions only agreed well with the experimental results, provided the multiple ionization of water was incorporated in the simulations. This strongly supports the importance of the role of MI of water molecules in the high-LET radiolysis of water. We also simulated the effects of MI of water on <i>G</i>-values for the primary species of the radiolysis of deaerated 0.4 M H₂SO₄ aqueous solutions by ¹⁰B(<i>n</i>,α)⁷Li recoils. As with the Fricke dosimeter, the best agreement between experiment and simulation was found at 25 °C when the MI of water was included in the simulations. It was also shown that <i>G</i>(Fe³⁺) decreases slightly as a function of temperature over the range of 25–350 °C. However, at elevated temperatures, no experimental data were available with which to compare our results.

Ionization of Water as an Effect of Quantum Delocalization at Aqueous Electrode Interfaces

<div><div><div><p>The enhanced probability of water dissociation at the aqueous electrode interfaces is predicted by path-integral ab initio molecular dynamics. The ionization process is observed at the aqueous platinum interface when nuclear quantum effects are introduced in the statistical sampling, while minor effects have been observed at the gold interface. We characterize the dissociation mechanism and the dynamics of the formed water ions. In spite of the fact that the concentration and lifetime of the ions might be challenging to be experimentally detectable, they may serve as a guide to future experiments. Our observation might have a significant impact on the understanding of electrochemical processes occurring at the metal electrode surface.</p></div></div></div>

Ionization of Water as an Effect of Quantum Delocalization at Aqueous Electrode Interfaces

<div><div><div><p>The enhanced probability of water dissociation at the aqueous electrode interfaces is predicted by path-integral ab initio molecular dynamics. The ionization process is observed at the aqueous platinum interface when nuclear quantum effects are introduced in the statistical sampling, while minor effects have been observed at the gold interface. We characterize the dissociation mechanism and the dynamics of the formed water ions. In spite of the fact that the concentration and lifetime of the ions might be challenging to be experimentally detectable, they may serve as a guide to future experiments. Our observation might have a significant impact on the understanding of electrochemical processes occurring at the metal electrode surface.</p></div></div></div>