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The oxidation processes of the radiation-generated, three-electron-bonded intermediates AcMet 2 [S∴S] + and AcMet [S∴Br] were investigated by pulse radiolysis via their reactions with tryptophan (TrpH). These intermediates were derived from N-acetyl-methionine amide ( N-AcMetNH 2) and N-acetyl-methionine methyl ester ( N-AcMetOMe). The bimolecular rate constant k of the reaction between each intermediate and l-tryptophan (TrpH) was measured. For N-AcMetNH 2, k for the reaction of AcMet 2 [S∴S] + with TrpH were 3.4 × 10 8 and 2.2 × 10 8 dm 3 mol −1 s −1 at pH = 1 and 4.5, respectively. For N-AcMetOMe, k for the reaction of AcMet 2 [S∴S] + with TrpH were 4.0 × 10 8 and 2.8 × 10 8 dm 3 mol −1 s −1 at pH 1 and 4.5, respectively. The rate constants for the intermolecular transformation of Met [S∴Br] into TrpH + or Trp were also estimated. For N-AcMetNH 2, k for the reaction of AcMet 2 [S∴Br] with TrpH were 2.6 × 10 8 and 3.3 × 10 8 dm 3 mol −1 s −1 at pH 1 and 4.5, respectively. Related mechanisms were discussed. [ABSTRACT FROM AUTHOR]

The absorption spectra of Br2•̵ and Br3̵ in aqueous solutions are investigated by pulse radiolysis techniques from room temperature to 380 and 350 °C, respectively. Br2•̵ can be observed even in supercritical conditions, showing that this species could be used as a probe in pulse radiolysis at high temperature and even under supercritical conditions. The weak temperature effect on the absorption spectra of Br2•̵ and Br3̵ is because, in these two systems, the transition occurs between two valence states; for example, for Br2̵ we have 2Σu→2Σg transition. These valence transitions involve no difiuse final state. However, the absorption band of Br̵ undergoes an important red shift to longer wavelengths. We performed classical dynamics of hydrated Br̵ system at 20 and 300 °C under pressure of 25 MPa. The radial distribution functions (rdfs) show that the strong temperature increase (from 20 to 300 °C) does not change the radius of the solvent first shell. On the other hand, it shifts dramatically (by 1 Å) the second maximum of the Br-- O rdf and introduces much disorder. This shows that the first water shell is strongly bound to the anion whatever the temperature. The first two water shells form a cavity of a roughly spherical shape around the anion. By TDDFT method, we calculated the absorption spectra of hydrated Br̵ at two temperatures and we compared the results with the experimental data. [ABSTRACT FROM AUTHOR]

Abstract: Measurements of primary g-values (at ∼10−7 s after the initial ionizing event) of , OH and H2O2 were extended to the very high linear energy transfer (LET) region (∼700eV/nm) near the Bragg peak. Heavy ions (4He2+, 12C6+, 20Ne10+, 28Si14+, 40Ar18+ and 56Fe26+) of energies up to 28GeV were provided by the Heavy Ion Medical Accelerator in Chiba (HIMAC) of the National Institute of Radiological Sciences (NIRS) in Chiba, Japan. Energies of the ions were decreased down to about 10MeV/u for 4He2+ using an energy absorber made of polymethylmethacrylate (PMMA) plates in order to vary the LET values. Beam was visualized after passing through the energy absorber using agarose gel of aqueous solution containing methyl viologen and sodium formate in order to determine how long ions can penetrate into water. Based on the information of the penetration depth of ions in samples, much attention was paid to dose correction and LET evaluation. The obtained data were plotted as a function of (Z eff/β)2 also instead of LET in order to discuss effects of physical track structures on product yields, resulted in better universality. [Copyright &y& Elsevier]

Abstract: Water radiolysis has been investigated with heavy ions having energies up to 28GeV provided from the Heavy Ion Medical Accelerator in Chiba (HIMAC) at the National Institute of Radiological Sciences (NIRS). Beams of 4He2+, 12C6+, 20Ne10+, 28Si14+, 40Ar18+ and 56Fe26+ with respective energies of 150, 400, 400, 490, 500 and 500MeV/u corresponding LET values of 2.2, 13, 30, 54, 92 and 183eV/nm, respectively, were taken for the irradiation. The LET changes in sample solutions can be neglected due to their high energies for the irradiation of 1-cm cells. Primary g values have been determined for three important products, hydrated electron (e− aq), hydroxyl radical (·OH), and hydrogen peroxide (H2O2) as track segment yields (differential yields) under the conditions of neutral pH. With increasing LET, the g values of e− aq and ·OH decrease from 2.4 and 2.6 in 4He2+ radiolysis to 0.9 and 1.1 (100eV)−1 in 56Fe26+ radiolysis, respectively. It was also found that the primary g value of e− aq is smaller than that of ·OH for any type of ion beam. For the 12C6+ beam, other energies such as 290, 220, 135MeV/u were taken for the irradiation to investigate the effects of type or atomic number of ions on the measured yields. Furthermore, effects of dissolved oxygen on enhancement of H2O2 production have also been investigated with aerated NaNO3 solutions. The presence of dissolved oxygen caused 15–35% enhancement in H2O2 yields for all beams. In addition, the results of the present work were compared with reported track segment yields. [Copyright &y& Elsevier]

Abstract: The absorption spectra of solvated electrons in 1-propanol and 2-propanol have been investigated from 22 to 270°C at a fixed pressure of 7MPa, by using both nanosecond pulse radiolysis and laser photolysis techniques. The results show that, even up to supercritical conditions, it is still possible to measure unambiguously the absorption spectra of solvated electron in these two propanols. The peak positions of the absorption spectra show a red-shift (shifts to longer wavelengths) as temperature increases, similar to water and other alcohols, but the temperature efficiency, dE max/dT, of 1-propanol is larger than that of 2-propanol. In addition, in clear contrast to that of pulse radiolysis, in laser photolysis experiments, an increase in the maximum absorbance of the absorption spectra of solvated electron with temperature up to ∼200°C is attributed to the increase of absorbance (CTTS absorption band) of I− anion at 248nm with increasing temperature. [Copyright &y& Elsevier]

Abstract: γ-Radiolysis and pulse radiolysis of phenol in aqueous solution up to supercritical condition have been carried out. G-values of phenol consumption and product formation have been determined. While dihydroxybenzenes were major products at room temperature, multi-ring compounds and benzene were formed above 300°C. This indicates reaction mechanism was changed above 300°C, where phenoxyl radical plays a predominant role. This is supported by the observation of phenoxyl radical in pulse radiolysis. In supercritical water, the G-values increased with decrease of density. [Copyright &y& Elsevier]

[Display omitted] • Radiolysis mechanism and radiolytic pathways of DAPhen were investigated. • Radiolysis of DAPhen is mainly through the cleavage of amide bonds and N C bonds. • HNO 3 enhanced the extraction and An/Ln separation performance of DAPhen after irradiation. • Radiolytic products of DAPhen were verified by DFT calculations to have extraction ability for U. The stability of organic extractant molecules against radiolysis is critical in the field of actinides and lanthanides (An/Ln) separations. In order to evaluate the radiolytic effects on the extraction performance, the solutions of N,N '-diethyl- N,N '-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen) in n -octanol were subjected to γ-irradiation in the presence and absence of 3 mol/L HNO 3 aqueous phase. Et-Tol-DAPhen diluted in n -octanol was almost completely decomposed after irradiation and exhibits decreased extraction ability at an absorbed dose of about 384 kGy, along with the appearance of various degradation products. Et-Tol-DAPhen, which was diluted in n -octanol, was completely decomposed upon irradiation in the presence of 3 mol/L HNO 3 aqueous phase. However, it exhibited higher D U and SF U/Eu values than before irradiation, as well as degradation products that were also generated. The structures of some isomers of radiolytic products were investigated by density functional theory (DFT) calculations, the radiolysis pathways and products of Et-Tol-DAPhen extractants were obtained, and the radiolysis pathways and products of Et-Tol-DAPhen extractants was proposed. The radiolytic products mainly originated from amide bond and N C bond cleavage of side group substituents, and some resulted from interaction with n -octanol radicals generated during radiolysis. The presence of HNO 3 can inhibit the radiolysis of Et-Tol-DAPhen to a certain extent and cause enhanced extraction ability. Moreover, the DFT calculations reveal that the radiolytic products produced in presence of 3 mol/L HNO 3 aqueous phase also have efficient extraction performance towards UO 2 2+. The understanding of the radiolysis pathways and products of extractants, based on radiation chemical effects is expected to be helpful for developing new strategies for extractants with long-term performance. [ABSTRACT FROM AUTHOR]