Electron Transport in Condensed Water

Zaider, Marco; Vrac̆ko, Marjan; Fung, A.; Fry, J. L.

doi:10.1093/oxfordjournals.rpd.a082177

Cited by 20 publications

(10 citation statements)

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“…Therefore, attempts have been made to combine ab initio techniques with approximate schemes for the momentum dependence. Examples of such heuristic approaches for water include the early work of Long et al (1989) on molecular clusters and those of Zaider et al (1990Zaider et al ( , 1994Zaider et al ( , 2000 on cubic ice. More recently, Sorini et al (2006 and reference therein) have applied similar techniques to various solids.…”

Section: The Low-energy Problem I: the Bethe Surfacementioning

confidence: 99%

Can Monte Carlo track structure codes reveal reaction mechanism in DNA damage and improve radiation therapy?

Nikjoo

Emfietzoglou

Watanabe

et al. 2008

Radiation Physics and Chemistry

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Section: The Low-energy Problem I: the Bethe Surfacementioning

confidence: 99%

Can Monte Carlo track structure codes reveal reaction mechanism in DNA damage and improve radiation therapy?

Nikjoo

Emfietzoglou

Watanabe

et al. 2008

Radiation Physics and Chemistry

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“…Due to the high degree of sophistication, such calculations are inherently complicated and for systems having more than 10-20 electrons it is still impossible to perform an exact numerical solution of the Schrödinger equation. Nevertheless, with the use of semi-empirical Hamiltonians (and other approximations) Zaider and others (18)(19)(20)(21)(22) have carried out first-principles calculations of the dielectric function of cubic ice and other biomaterials. More recently, promising results have been obtained in the context of time-dependent density functional theory over a restricted parameter space (23).…”

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confidence: 99%

Inelastic Cross Sections for Low-Energy Electrons in Liquid Water: Exchange and Correlation Effects

et al. 2013

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Low-energy electrons play a prominent role in radiation therapy and biology as they are the largest contributor to the absorbed dose. However, no tractable theory exists to describe the interaction of low-energy electrons with condensed media. This article presents a new approach to include exchange and correlation (XC) effects in inelastic electron scattering at low energies (below ∼10 keV) in the context of the dielectric theory. Specifically, an optical-data model of the dielectric response function of liquid water is developed that goes beyond the random phase approximation (RPA) by accounting for XC effects using the concept of the many-body local-field correction (LFC). It is shown that the experimental energy-loss-function of liquid water can be reproduced by including into the RPA dispersion relations XC effects (up to second order) calculated in the time-dependent local-density approximation with the addition of phonon-induced broadening in N. D. Mermin's relaxation-time approximation. Additional XC effects related to the incident and/or struck electrons are included by means of the vertex correction calculated by a modified Hubbard formula for the exchange-only LFC. Within the first Born approximation, the present XC corrections cause a significantly larger reduction (∼10-50%) to the inelastic cross section compared to the commonly used Mott and Ochkur approximations, while also yielding much better agreement with the recent experimental data for amorphous ice. The current work offers a manageable, yet rigorous, approach for including non-Born effects in the calculation of inelastic cross sections for low-energy electrons in liquid water, which due to its generality, can be easily extended to other condensed media.

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“…In the simulation, the particles are transported until their energy falls below a certain limit, generally given by the lower limit of the interaction cross section data, and are then assumed to deposit their remaining energy at the position of their last interaction. Detailed descriptions regarding the principle of track structure simulations can be found in Friedland et al (1998), Grosswendt (2002), Zaider et al (1994) as well as in Nikjoo et al (2006), where also a comprehensive overview of existing codes is provided.…”

Section: Interaction Cross Section Data In Ptra and Geant4-dnamentioning

confidence: 99%

Electron emission from amorphous solid water after proton impact: Benchmarking PTra and Geant4 track structure Monte Carlo simulations

Bug

Rabus

Rosenfeld

2012

Radiation Physics and Chemistry

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Track structure Monte Carlo simulations of ionising radiation in water are often used to estimate radiation damage to DNA. For this purpose, an accurate simulation of the transport of densely ionising low-energy secondary electrons is particularly important, but is impaired by a high uncertainty of the required physical interaction cross section data of liquid water.A possible tool for the verification of the secondary electron transport in a track structure simulation has been suggested by Toburen et al. (2010), who have measured the angle-dependent energy spectra of electrons, emitted from a thin layer of amorphous solid water (ASW) upon a passage of 6. MeV protons.In this work, simulations were performed for the setup of their experiment, using the PTB Track structure code (PTra) and Geant4-DNA. To enable electron transport below the ionisation threshold, additional excitation and dissociative attachment anion states were included in PTra and activated in Geant4. Additionally, a surface potential was considered in both simulations, such that the escape probability for an electron is dependent on its energy and impact angle at the ASW/vacuum interface.For vanishing surface potential, the simulated spectra are in good agreement with the measured spectra for energies above 50. eV. Below, the simulations overestimate the yield of electrons by a factor up to 4 (PTra) or 7 (Geant4-DNA), which is still a better agreement than obtained in previous simulations of this experimental situation. The agreement of the simulations with experimental data was significantly improved by using a steplike increase of the potential energy at the ASW surface. 2012 Elsevier Ltd. AbstractTrack structure Monte Carlo simulations of ionising radiation in water are often used to estimate radiation damage to DNA. For this purpose, an accurate simulation of the transport of densely ionising low-energy secondary electrons is particularly important, but is impaired by a high uncertainty of the required physical interaction cross section data of liquid water.A possible tool for the verification of the secondary electron transport in a track structure simulation has been suggested by Toburen et al. (2010), who have measured the angle-dependent energy spectra of electrons, emitted from a thin layer of amorphous solid water (ASW) upon a passage of 6 MeV protons.In this work, simulations were performed for the setup of their experiment, using the PTB Track structure code (PTra) and Geant4-DNA. To enable electron transport below the ionisation threshold, additional excitation and dissociative attachment anion states were included in PTra and activated in Geant4.Additionally, a surface potential was considered in both simulations, such that the escape probability for an electron is dependent on its energy and impact angle at the ASW/vacuum interface.For vanishing surface potential, the simulated spectra are in good agreement with the measured spectra for energies above 50 eV. Below, the simulations overestimate the yield of electrons by a ...

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Electron Transport in Condensed Water

Cited by 20 publications

References 0 publications

Can Monte Carlo track structure codes reveal reaction mechanism in DNA damage and improve radiation therapy?

Can Monte Carlo track structure codes reveal reaction mechanism in DNA damage and improve radiation therapy?

Inelastic Cross Sections for Low-Energy Electrons in Liquid Water: Exchange and Correlation Effects

Electron emission from amorphous solid water after proton impact: Benchmarking PTra and Geant4 track structure Monte Carlo simulations

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