Updated model for dielectric response function of liquid water

Dingfelder, M.

doi:10.1016/j.apradiso.2013.01.016

Cited by 28 publications

(29 citation statements)

References 14 publications

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“…Thus, the only nontrivial parameter for calculating ionization and excitation cross sections (in the Born approximation) for liquid water is the dielectric function, ε(E,q), which accounts for the screening and polarization properties of the condensed phase. It is recognized 10,11 that there are three major models of the dielectric function of liquid water developed and refined through a series of studies: the Ritchie et al model, 12 the Dingfelder et al model, [13][14][15] and the Emfietzoglou et al model. [16][17][18][19][20] All these models are based on an analytic parameterization of the experimental data (those of Heller et al 21 or Hayashi et al 22 ) for the dielectric function of liquid water at the optical limit (q ≈ 0) using a linear superposition of Drude-like functions, and a set of dispersion relations to extend the dielectric function to q 0.…”

Section: A Dielectric Response Functionmentioning

confidence: 99%

Technical Note: Improvements in geant4 energy‐loss model and the effect on low‐energy electron transport in liquid water

2015

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Section: A Dielectric Response Functionmentioning

confidence: 99%

Technical Note: Improvements in geant4 energy‐loss model and the effect on low‐energy electron transport in liquid water

2015

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“…This may be attributed to their strong material dependence, along with the limited experimental data at k ≠ 0. On the other hand, for liquid water, the availability of experimental data for finite k has made possible the development of a consistent set of empirical dispersion relations for this material …”

Section: The ‘Standard’ Modelsmentioning

confidence: 99%

Inelastic mean free path of low‐energy electrons in condensed media: beyond the standard models

Emfietzoglou

Kyriakou

García-Molina

et al. 2015

Surface & Interface Analysis

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The most established approach for ‘practical’ calculations of the inelastic mean free path (IMFP) of low‐energy electrons (~10 eV to ~10 keV) is based on optical‐data models of the dielectric function. Despite nearly four decades of efforts, the IMFP of low‐energy electrons is often not known with the desired accuracy. A universal conclusion is that the predictions of the most popular models are in rather fair agreement above a few hundred electron volts but exhibit considerable differences at lower energies. However, this is the energy range where their two main approximations, namely, the random‐phase approximation (RPA) and the Born approximation, may be invalid. After a short overview of the most popular optical‐data models, we present an approach to include exchange and correlation (XC) effects in IMFP calculations, thus going beyond the RPA and Born approximation. The key element is the so‐called many‐body local‐field correction (LFC). XC effects among the screening electrons are included using a time‐dependent local‐density approximation for the LFC. Additional XC effects related to the incident and struck electrons are included through the vertex correction calculated using a screened‐Hubbard formula for the LFC. The results presented for liquid water reveal that XC may increase the IMFP by 15–45% from its Born–RPA value, yielding much better agreement with available experimental data. The present work provides a manageable, yet rigorous, approach to improve upon the standard models for IMFP calculations, through the inclusion of XC effects at both the level of screening and the level of interaction. Copyright © 2015 John Wiley & Sons, Ltd.

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“…This equation for the DIMP provides a theoretical basis for the models for low energy ( < ∼ 100 eV) electron inelastic scatter in water that are used in modern Monte Carlo radiation transport codes. 16,19,20 For liquid water, which best represents the soft condensed matter phase of biological tissue, the dielectric response function should take into account the excitation and ionization energy levels in that thermodynamic phase. Experimental data for scattering off a liquid water target are scarce and the available data that is used to validate Drude oscillator models for (ω, q) is in the optical limit, q → 0.…”

Section: Dielectric Response Approachmentioning

confidence: 99%

“…These same electron inelastic cross-section models are also implemented in PARTRAC. 20 In Geant4, the liquid-water cross-section models are available in the module known as Geant4-DNA. 28 …”

Section: Monte Carlo Radiation Transport Modelingmentioning

confidence: 99%

Advances in Computational Radiation Biophysics for Cancer Therapy: Simulating Nano-Scale Damage by Low-Energy Electrons

Kuncic

2015

Biophys. Rev. Lett.

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Computational radiation biophysics is a rapidly growing area that is contributing, alongside new hardware technologies, to ongoing developments in cancer imaging and therapy. Recent advances in theoretical and computational modeling have enabled the simulation of discrete, event-by-event interactions of very low energy ( 100 eV) electrons with water in its liquid thermodynamic phase. This represents a significant advance in our ability to investigate the initial stages of radiation induced biological damage at the molecular level. Such studies are important for the development of novel cancer treatment strategies, an example of which is given by microbeam radiation therapy (MRT). Here, new results are shown demonstrating that when excitations and ionizations are resolved down to nano-scales, their distribution extends well outside the primary microbeam path, into regions that are not directly irradiated. This suggests that radiation dose alone is insufficient to fully quantify biological damage. These results also suggest that the radiation cross-fire may be an important clue to understanding the different observed responses of healthy cells and tumor cells to MRT.

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Updated model for dielectric response function of liquid water

Cited by 28 publications

References 14 publications

Technical Note: Improvements in geant4 energy‐loss model and the effect on low‐energy electron transport in liquid water

Technical Note: Improvements in geant4 energy‐loss model and the effect on low‐energy electron transport in liquid water

Inelastic mean free path of low‐energy electrons in condensed media: beyond the standard models

Advances in Computational Radiation Biophysics for Cancer Therapy: Simulating Nano-Scale Damage by Low-Energy Electrons

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