Evidence for spur overlap in the pulse radiolysis of water. [15-MeV electrons]
The kinetics of the decay of hydrated electron absorbance in pure water has been studied as a function of time and radiation dose delivered by 20-ns pulses of 15-MeV electrons. In order to identify intraspur reactions of the hydrated electron, values of the function ((-d(e/sub aq//sup -/)/(e/sub aq//sup -/))/dt)/sub t/ (identical with Q/sub t/) were investigated as a function of pulse dose and time. Q/sub t/ represents the fraction of hydrated electrons disappearing at any given time, t, following the pulse. Whereas Q has the same functional form as a first-order rate constant, it is not a constant, but decreases with increasing time following the pulse. However, the functional form of Q/sub t/ vs. time remains the same at low pulse doses (37 - 380 rads) for relatively long periods of time (up to 1 ..mu..s). The dose independence of Q is interpreted as evidence for predominantly intraspur hydrated electron decay. A plot of Q/sub t/ vs. the function ((time)/sup 1/2/(dose)/sup 1/3)) yields a relatively sharp transition from dose independent hydrated electron decay (interpreted as arising predominantly from intraspur reactions) to dose dependent decay (both interspur and intraspur decay). This transition region is interpreted as the onset of significant spur overlap. In the range 0-8000 rads per 20-ns pulse, an empirical constant: (approximate time of detectable overlap)/sup 1/2/ (dose)/sup 1/3/ = 110 +- 10 ns/sup 1/2/ rads/sup 1/3/ is obtained which correlates the onset of experimentally observable spur overlap. Based upon these results, implications regarding spur sizes and spatial distributions of spurs and the need to include spur overlap considerations in modeling studies are developed.
- Research Organization:
- Univ. of Delaware, Newark
- OSTI ID:
- 7291807
- Journal Information:
- J. Phys. Chem.; (United States), Vol. 81:13
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
WATER
RADIOLYSIS
ELECTRON BEAMS
MEV RANGE 10-100
PULSED IRRADIATION
SOLVATED ELECTRONS
BEAMS
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
DECOMPOSITION
ELECTRONS
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
HYDROGEN COMPOUNDS
IRRADIATION
LEPTON BEAMS
LEPTONS
MEV RANGE
OXYGEN COMPOUNDS
PARTICLE BEAMS
RADIATION CHEMISTRY
RADIATION EFFECTS
400600* - Radiation Chemistry