Dispersive Relaxation Dynamics of Photoexcitations in a Polyfluorene Film Involving Energy Transfer:  Experiment and Monte Carlo Simulations

2001 ◽  
Vol 105 (38) ◽  
pp. 9139-9149 ◽  
Author(s):  
Stefan C. J. Meskers ◽  
Jens Hübner ◽  
Michael Oestreich ◽  
Heinz Bässler
Keyword(s):  
Monte Carlo ◽  
Energy Transfer ◽  
Monte Carlo Simulations ◽  
Relaxation Dynamics ◽  
Transfer Experiment

Low-linear energy transfer radiolysis of liquid water at elevated temperatures up to 350°C: Monte-Carlo simulations

2011 ◽  
Vol 508 (4-6) ◽  
pp. 224-230 ◽  
Author(s):  
S. Sanguanmith ◽  
Y. Muroya ◽  
J. Meesungnoen ◽  
M. Lin ◽  
Y. Katsumura ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Energy Transfer ◽  
Monte Carlo Simulations ◽  
Liquid Water ◽  
Linear Energy Transfer ◽  
Elevated Temperatures

Monte-Carlo calculation of the primary yields of H2O2 in the 1H+, 2H+, 4He2+, 7Li3+, and 12C6+ radiolysis of liquid water at 25 and 300°C

2002 ◽  
Vol 80 (1) ◽  
pp. 68-75 ◽  
Author(s):  
Jintana Meesungnoen ◽  
Jean-Paul Jay-Gerin ◽  
Abdelali Filali-Mouhim ◽  
Samlee Mankhetkorn
Keyword(s):  
Hydrogen Peroxide ◽  
Monte Carlo ◽  
Energy Transfer ◽  
Monte Carlo Simulations ◽  
Liquid Water ◽  
Linear Energy Transfer ◽  
Average Distance ◽  
Water Radiolysis ◽  
Model Calculations ◽  
Primary Yield

Monte-Carlo simulations are used to calculate the primary yield of hydrogen peroxide (GH2O2) of the radiolysis of pure, deaerated liquid water as a function of linear energy transfer (LET) of the incident radiation over the range ~0.3–100 keV µm–1, at 25 and 300°C. The radiations include 1H+, 2H+, 4He2+, 7Li3+, and 12C6+ ions with energies from 0.17 MeV to 3.6 GeV. At 25°C, it is found that our GH2O2 values, calculated with protons of different initial energies, show a monotonic increase as a function of LET, in agreement with the commonly assumed expectation of an increase in molecular yields with increasing LET. Our calculated H2O2 yields at 300°C increase significantly faster with LET than do their corresponding 25°C values, showing that the temperature dependence of GH2O2 at higher LET is less than for low-LET radiation. We also report our results on the temporal variations of the H2O2 yields, in the interval ~1 × 10–13 – 1 × 10–6 s, at 25 and 300°C and for the different types of radiation considered. Finally, we find that for incident ions of equal LET > 10 keV µm–1, GH2O2 decreases as the ion velocity increases, from protons (or deuterons) to carbon ions. These differences produced in GH2O2 by changing the type of radiation are explained by the greater mean energy of secondary electrons from the higher velocity ions, which penetrate to a greater average distance from the actual particle track, with a corresponding decrease in molecular yields. Our calculated GH2O2 values compare generally well with the experimental data available from the literature and are also in good accord with the predictions of deterministic diffusion-kinetic model calculations reported earlier.Key words: liquid water, radiolysis, primary yields, hydrogen peroxide (H2O2), linear energy transfer (LET), accelerated protons and heavy ions, temperature, Monte-Carlo simulations.

Monte Carlo simulation study of the effects of acidity and LET on the primary free-radical and molecular yields of water radiolysis — Application to the Fricke dosimeter

2007 ◽  
Vol 85 (3) ◽  
pp. 214-229 ◽  
Author(s):  
Narongchai Autsavapromporn ◽  
Jintana Meesungnoen ◽  
Ianik Plante ◽  
Jean-Paul Jay-Gerin
Keyword(s):  
Monte Carlo ◽  
Energy Transfer ◽  
Free Radicals ◽  
Sulfuric Acid ◽  
Free Radical ◽  
Monte Carlo Simulations ◽  
Linear Energy Transfer ◽  
Oh Radicals ◽  
Water Radiolysis ◽  
Monte Carlo Simulation Study

Monte Carlo simulations are used to investigate the effects of acidity (pH) on the primary yields of various chemical species produced in the radiolysis of de-aerated aqueous sulfuric acid solutions over the range from neutral solution to 0.4 mol/L H2SO4. The effects of the quality of radiation, measured in terms of linear energy transfer (LET), have also been studied for LET varying from ~0.3 to 15 keV/µm at ambient temperature. Our results show that an increase in acidity (1 < pH < 4) leads to an increase in the yield [Formula: see text] of the "reducing" free radicals (hydrated electron and H• atom) and a slight increase in G·OH and [Formula: see text], while there is a slight decrease in [Formula: see text] At pH < 1, •OH radicals react with HSO4- anions to form SO4·– radicals, resulting in a steep decrease in G.OH. By contrast, in the range of pH from ~4 to 7, the calculated yield values are independent of sulfuric acid concentration. In both neutral water and 0.4 mol/L H2SO4 (pH 0.46) solutions, the primary molecular yields increase upon increasing LET to ~15 keV/µm with a concomitant decrease in those of free radicals. As an exception, GH. at first increases with LET, reaching a maximum near 6.5 keV/µm before decreasing steeply at higher LET. The results obtained are generally in good agreement with available experimental data over the whole acidity and LET ranges studied. Finally, as an application, we have simulated the radiation-induced oxidation of ferrous sulfate solutions in aerated aq. 0.4 mol/L H2SO4 (Fricke dosimeter) as a function of time up to ~50 s and addressed the effects of LET on the resulting ferric ion yield at 25 °C. The production of Fe3+ ions is highly sensitive to free-radical yields, especially H• atoms (via formation of HO2•), resulting in a marked decline of G(Fe3+) with increasing LET. The general trend of the observed variation of G(Fe3+) with radiation quality is well reproduced by our computed Fe3+ ion yield values.Key words: liquid water, acidic (H2SO4) aqueous solutions, radiolysis, free-radical and molecular yields, linear energy transfer (LET), Fricke dosimeter, Monte Carlo simulations.

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