Rate constants for the reaction of hydronium ions with hydrated electrons up to 350°C

Stanisky, Christopher M.; Bartels, David M.; Takahashi, Kenji

doi:10.1016/j.radphyschem.2009.08.032

Cited by 10 publications

(7 citation statements)

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“…To this end, the Debye correction (eqn (11)) was used to compute the temperature and density dependent rate constant in the diffusion limit. Experimental rate constants for this reaction have been obtained by pulse radiolysis from Bartels and coworkers for temperatures up to 350 1C and were described by the polynomial expression 88 log(k/L mol À1 s À1 ) = 39.127 À 3.888 Â 10 4 (T/K) À1 + 2.054 Â 10 7 (T/K) À2 À 4.899 Â 10 9 (T/K) À3 + 4.376 Â 10 11 (T/K) À4…”

Section: Comparison With Independent Pairs Simulationsmentioning

confidence: 99%

Independent pairs and Monte-Carlo simulations of the geminate recombination of solvated electrons in liquid-to-supercritical water

Torres-Alacan

Kratz

Vöhringer

2011

Phys. Chem. Chem. Phys.

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Independent pairs (IP) and Monte Carlo (MC) simulations are employed to model experimental femtosecond time-resolved pump-probe spectroscopic data on the geminate recombination dynamics of solvated electrons in liquid-to-supercritical water. The hydrated electron was created by two-photon ionization of the neat fluid with a total ionization energy of 9.3 eV. In both numerical approaches, the ejection length, , (i.e. the distance from the ionization core, at which the electron is thermally and spatially localized) is used as the primary adjustable fitting parameter that can bring both model simulations into quantitative agreement with the ultrafast kinetic experiment. The influence of the thermodynamic conditions on the ejection length and on the recombination mechanism is discussed. Whereas in the compressed liquid associated with a high dielectric constant (ε ≥ 20), the electron recombines predominantly with the OH radical, the dissociative recombination via charge neutralization with the hydronium cation takes over at small dielectric constants (ε < 20). The importance of charge-dipole interactions for Monte-Carlo simulations of the recombination reactions of the hydrated electrons in the low-permittivity region is stressed.

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Section: Comparison With Independent Pairs Simulationsmentioning

confidence: 99%

Independent pairs and Monte-Carlo simulations of the geminate recombination of solvated electrons in liquid-to-supercritical water

Torres-Alacan

Kratz

Vöhringer

2011

Phys. Chem. Chem. Phys.

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“…In fact, the rate constant for this reaction is known only up to 350 8C; 24 at 25 8C, it is 2.1 Â 10 10 (mol/L) -1 s -1 while it reaches the value of *2 Â 10 12 (mol/L) -1 s -1 at 350 8C. 16,24,53 However, the recent measurements of Muroya et al 35 have suggested that reaction R6 at 400 8C is even faster than that at 350 8C. In view of these results, we have examined the sensitivity of our simulated radiolytic yields on variations in the value of the rate constant for this reaction.…”

Section: Yieldmentioning

confidence: 98%

Radiolysis of supercritical water at 400 °C and liquid-like densities near 0.5 g/cm³ — A Monte Carlo calculation

2010

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Monte Carlo simulations are used to calculate the primary radical yields gðe aq À Þ, g( OH), the sum [gðe aq À Þ + g( OH) + g(H )], and the ratio g(H )/gðe aq À Þ in the low linear energy transfer (LET) radiolysis of supercritical water (SCW) at 400 8C in the high-density, liquid-like region near *0.5 g/cm 3 . Using all the currently available information on the reactivities and diffusion coefficients of the radiation-induced species under these conditions, and assuming the aqueous medium to be a ''continuum'', a good accord is found between our calculations and the available experimental data. In particular, our computed e aq À yields at 60 ps and 1 ns compare very well with recently reported direct time-dependent e aq À yield measurements in SCW (D 2 O) at 400 8C and 0.570 g/cm 3 using picosecond pulse radiolysis experiments.

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“…The most important basic mechanisms of water radiolysis have been established for over half a century [8][9][10][11] , but measurements of transients have been made at the ca. 250-350 o C operating temperatures of pressurized water reactors only within the last two decades [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] . The most important starting input for kinetics simulation is the yield or G value, characterizing the number of radical or molecular products formed per unit of radiation energy 8 in the overall radiolysis process:…”

Section: Introductionmentioning

confidence: 99%

Low LET radiolysis escape yields for reducing radicals and H2 in pressurized high temperature water

Sterniczuk

Yakabuskie

Wren

et al. 2016

Radiation Physics and Chemistry

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Low Linear Energy Transfer (LET) radiolysis escape yields (G values) are reported for the sum (G(H) + G(e-) aq) and for G(H 2) in subcritical water up to 350 o C. The scavenger system 1-10 mM acetate/0.001M hydroxide/0.00048M N 2 O was used with simultaneous mass spectroscopic detection of H 2 and N 2 product. Temperature-dependent measurements were carried out with 2.5MeV electrons from a van de Graaff accelerator, while room temperature calibration measurements were done with a 60 Co gamma source. The concentrations and dose range were carefully chosen so that initial spur chemistry is not perturbed and the N 2 product yield corresponds to those reducing radicals that escape recombination in pure water. In comparison with a recent review recommendation of Elliot and Bartels (AECL report 153-127160-450-001, 2009), the measured reducing radical yield is seven percent smaller at room temperature but in fairly good agreement above 150 o C. The H 2 escape yield is in good agreement throughout the temperature range with several previous studies that used much larger radical scavenging rates. Previous analysis of earlier high temperature measurements of G esc (OH) is shown to be flawed, although the actual G values may be nearly correct. The methodology used in the present report greatly reduces the range of possible error and puts the high temperature escape yields for low-LET radiation on a much firmer quantitative foundation than was previously available.

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Rate constants for the reaction of hydronium ions with hydrated electrons up to 350°C

Cited by 10 publications

References 5 publications

Independent pairs and Monte-Carlo simulations of the geminate recombination of solvated electrons in liquid-to-supercritical water

Independent pairs and Monte-Carlo simulations of the geminate recombination of solvated electrons in liquid-to-supercritical water

Radiolysis of supercritical water at 400 °C and liquid-like densities near 0.5 g/cm³ — A Monte Carlo calculation

Low LET radiolysis escape yields for reducing radicals and H2 in pressurized high temperature water

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Rate constants for the reaction of hydronium ions with hydrated electrons up to 350°C

Cited by 10 publications

References 5 publications

Independent pairs and Monte-Carlo simulations of the geminate recombination of solvated electrons in liquid-to-supercritical water

Independent pairs and Monte-Carlo simulations of the geminate recombination of solvated electrons in liquid-to-supercritical water

Radiolysis of supercritical water at 400 °C and liquid-like densities near 0.5 g/cm3 — A Monte Carlo calculation

Low LET radiolysis escape yields for reducing radicals and H2 in pressurized high temperature water

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Radiolysis of supercritical water at 400 °C and liquid-like densities near 0.5 g/cm³ — A Monte Carlo calculation