Radiation chemistry of D2O Time dependence of the yields of the radicals at ambient temperature and rate constants for the reactions OD+OD and D+OD up to 200°C

Abstract

6QB The yields of and have been measured in at ambient temperature as a function of e aq~, e aq~]~O D e aq~] D~]~OD D 2 O scavenger concentration. At scavenging powers O107 s~1 is 10% larger than its value in but for scavenging powers G(e aq~) H 2 O, P3 ] 108 s~1 the yields of and are the same in both solvents, indicating that scavenging in e aq~, e aq~]~O D e aq~] D~]~OD the spurs suppresses the reactions leading to the di †erent primary yields. The absorption spectrum of is found to be verỹOD similar to that of comprising a weak band rising into the UV between 320 and 220 nm with m2 mol~1 atOH, e 250 \ 50^2 20 ¡C. The shape of the band is the same at 200 ¡C. Rate constants for the reactions and have beeñOD ]~OD D~]~OD measured up to 200 ¡C, on the assumption that for is independent of temperature. As with the corresponding reactions e 250~O D in they show non-linear Arrhenius behaviour, being close to the di †usion-controlled value at ambient temperature, but an H 2 O, order of magnitude less than this value at 200 ¡C. The values of the rate constants are very similar in both solvents.

Spur Decay of the Solvated Electron in Picosecond Radiolysis Measured with Time-Correlated Absorption Spectroscopy

“…(Nevertheless very similar results have been found for the longest spur decay component using lower dose 2 ns electron pulses at the Notre Dame Radiation Laboratory , The very low scavenging power data of Buxton et al shown in Figure could be matched by exchanging the constant 1 in eq 9 for an additional exponential decay with time constant of about 13 μs. Our time-resolved experiment is insensitive to such a slow component of track chemistry.…”

“…We consider the work of Elliot et al using both nitrate and methyl viologen scavengers, as perhaps the most reliable in the literature. Recent work of Buxton et al has shown good agreement for both N 2 O and tetranitromethane scavengers. The precise methyl chloride measurement of Schmidt et al, which was based entirely on conductivity including a T-jump for dosimetry, is also in superb agreement with the predicted curve.…”

“…24 ) Some recent studies have called into question the utility of the G inf idealization for low dose rate and low scavenger concentrations. 15,25 The very low scavenging power data of Buxton et al 15 shown in Figure 5 could be matched by exchanging the constant 1 in eq 9 for an additional exponential decay with time constant of about 13 µs. Our time-resolved experiment is insensitive to such a slow component of track chemistry.…”

“…Using this form for G °( t ) allows easy prediction of product yield in hydrated electron scavenger experiments by integration of eq 8 over time. In Figure we plot this prediction as a function of k s [S] together with product yield data for methyl chloride, , glycylglycine, N 2 O, − tetranitromethane (TNM), nitrate, , and methyl viologen 17 scavengers. Taking G inf = 2.5, we obtain G ( k s [S]) = 2.7 for a scavenging power of 1 × 10 7 s -1 , a result which the most precise scavenger studies have converged upon, with scatter of only 2−3% .…”

Spur Decay Kinetics of the Solvated Electron in Heavy Water Radiolysis

“…Elliot and co-workers measure 3.0−3.2 electrons/100 eV. Buxton and co-workers obtain 3.1 electrons /100 eV . Fielden and Hart measured 3.0 for this quantity, also at a scavenging power of 10 7 s -1 .…”