Erratum: Radiolysis of liquid water: An attempt to reconcile Monte-Carlo calculations with new experimental hydrated electron yield data at early times

2002 ◽  
Vol 80 (12) ◽  
pp. 1716
Author(s):  
Yusa Muroya ◽  
Jintana Meesungnoen ◽  
Jean-Paul Jay-Gerin ◽  
Abdelali Filali-Mouhim ◽  
Thomas Goulet ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Liquid Water ◽  
Hydrated Electron ◽  
Yield Data ◽  
Monte Carlo Calculations ◽  
Electron Yield

Radiolysis of liquid water: An attempt to reconcile Monte-Carlo calculations with new experimental hydrated electron yield data at early times

2002 ◽  
Vol 80 (10) ◽  
pp. 1367-1374 ◽  
Author(s):  
Yusa Muroya ◽  
Jintana Meesungnoen ◽  
Jean-Paul Jay-Gerin ◽  
Abdelali Filali-Mouhim ◽  
Thomas Goulet ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Liquid Water ◽  
Hydrated Electron ◽  
Time Dependent ◽  
Water Radiolysis ◽  
Deterministic Models ◽  
Yield Data ◽  
Simulation Code ◽  
Time Zero ◽  
Electron Yield

A re-examination of our Monte-Carlo modeling of the radiolysis of liquid water by low linear-energy-transfer (LET ~ 0.3 keV µm–1) radiation is undertaken herein in an attempt to reconcile the results of our simulation code with recently revised experimental hydrated electron (e–aq) yield data at early times. The thermalization distance of subexcitation electrons, the recombination cross section of the electrons with their water parent cations prior to thermalization, and the branching ratios of the different competing mechanisms in the dissociative decay of vibrationally excited states of water molecules were taken as adjustable parameters in our simulations. Using a global-fit procedure, we have been unable to find a set of values for those parameters to simultaneously reproduce (i) the revised e–aq yield of 4.0 ± 0.2 molecules per 100 eV at "time zero" (that is, a reduction of ~20% over the hitherto accepted value of 4.8 molecules per 100 eV), (ii) the newly measured e–aq decay kinetic profile from 100 ps to 10 ns, and (iii) the time-dependent yields of the other radiolytic species H•, •OH, H2, and H2O2 (up to ~1 µs). The lowest possible limiting "time-zero" yield of e–aq that we could in fact obtain, while ensuring an acceptable agreement between all computed and experimental yields, was ~4.4 to 4.5 molecules per 100 eV. Under these conditions, the mean values of the electron thermalization distance and of the geminate electron–cation recombination probability, averaged over the subexcitation electron "entry spectrum," are found to be equal to ~139 Å and ~18%, respectively. These values are to be compared with those obtained in our previous simulations of liquid water radiolysis, namely ~88 Å and ~5.5%, respectively. Our average electron thermalization distance is also to be compared with the typical size (~64–80 Å) of the initial hydrated electron distributions estimated in current deterministic models of "spur" chemistry. Finally, our average probability for geminate electron–cation recombination agrees well with an estimated value of ~15% recently reported in the literature. In conclusion, this work shows that an adaptation of our calculations to a lower hydrated electron yield at early times is possible, but also suggests that the topic is not closed. Further measurements of the e–aq yields at very short times are needed. Key words: liquid water, radiolysis, electron–cation geminate recombination, electron thermalization distance, hydrated electron (e–aq), e–aq decay kinetics, time-dependent molecular and radical yields, Monte-Carlo simulations.

Monte Carlo Modelling of Secondary Electron Yield from Rough Surfaces

1990 ◽  
Vol 48 (1) ◽  
pp. 422-423
Author(s):  
John C. Russ
Keyword(s):  
Monte Carlo ◽  
Energy Loss ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Analytical Calculation ◽  
Mean Free Path ◽  
Single Scattering ◽  
High Energy ◽  
Secondary Electron Yield ◽  
Electron Yield

Monte-Carlo programs are well recognized for their ability to model electron beam interactions with samples, and to incorporate boundary conditions such as compositional or surface variations which are difficult to handle analytically. This success has been especially powerful for modelling X-ray emission and the backscattering of high energy electrons. Secondary electron emission has proven to be somewhat more difficult, since the diffusion of the generated secondaries to the surface is strongly geometry dependent, and requires analytical calculations as well as material parameters. Modelling of secondary electron yield within a Monte-Carlo framework has been done using multiple scattering programs, but is not readily adapted to the moderately complex geometries associated with samples such as microelectronic devices, etc.This paper reports results using a different approach in which simplifying assumptions are made to permit direct and easy estimation of the secondary electron signal from samples of arbitrary complexity. The single-scattering program which performs the basic Monte-Carlo simulation (and is also used for backscattered electron and EBIC simulation) allows multiple regions to be defined within the sample, each with boundaries formed by a polygon of any number of sides. Each region may be given any elemental composition in atomic percent. In addition to the regions comprising the primary structure of the sample, a series of thin regions are defined along the surface(s) in which the total energy loss of the primary electrons is summed. This energy loss is assumed to be proportional to the generated secondary electron signal which would be emitted from the sample. The only adjustable variable is the thickness of the region, which plays the same role as the mean free path of the secondary electrons in an analytical calculation. This is treated as an empirical factor, similar in many respects to the λ and ε parameters in the Joy model.

Monte Carlo calculations of neutron spectrum parameters at the JRTR NAA channels

2021 ◽  
Vol 134 ◽  
pp. 103688
Author(s):  
Ihsan Farouki ◽  
Rashdan Malkawi ◽  
Sayel Marashdeh
Keyword(s):  
Monte Carlo ◽  
Neutron Spectrum ◽  
Monte Carlo Calculations
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