Angular and energy dependence of cross sections for ejection of electrons from water vapor. II. 15<i>–</i>150-keV proton impact

Bolorizadeh, Mohammad Agha; Rudd, M. E.

doi:10.1103/physreva.33.888

Cited by 107 publications

(74 citation statements)

References 18 publications

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“…Their atomic compositions and densities can be found in the ICRU Report 46 [31] and other sources, and a reasonable value of their mean binding energies can be estimated from the values of their molecular components, such as the water molecule, DNA bases and backbone, and amino acids [8,9,15]. We also show experimental data for water vapor [28,32,33], which nicely agree with our calculations above 100 keV, where the first Born approximation is applicable without further corrections. From our results, it seems that all the biological targets different from water have a larger ionization probability than water.…”

Section: Fig 2 (Color Online)mentioning

confidence: 82%

Semiempirical Model for the Ion Impact Ionization of Complex Biological Media

et al. 2013

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We present a semiempirical model for calculating the electron emission from any organic compound after ion impact. With only the input of the density and composition of the target we are able to evaluate its ionization cross sections using plausible approximations. Results for protons impacting in the most representative biological targets (such as water or DNA components) show a very good comparison with experimental data. Because of its simplicity and great predictive effectiveness, the method can be immediately extended to any combination of biological target and charged particle of interest in ion beam cancer therapy. DOI: 10.1103/PhysRevLett.110.148104 PACS numbers: 87.53.Àj, 79.20.Àm, 87.14.gk, 87.56.Àv Secondary electron emission is a key step in the mechanism of radiation damage to biomolecular systems induced by ion impact. As a matter of fact, ion beam cancer therapy exploits the particular properties of ion tracks, in which the ionization yield reaches a maximum near the end of their trajectories (the Bragg peak), allowing a precise and narrow energy deposition in deep-seated tumors, minimizing the radiation effects in healthy surrounding tissues [1]. These ejected electrons can produce further ionizations, initiating an avalanche effect, leading to the energy transfer to sensitive biomolecular targets, such as DNA or proteins. But not only is the number of emitted electrons relevant, but also their energy spectrum, since, although high energy electrons are those capable of producing further ionizations, it has been shown that low energy electrons (below ionization threshold) can also produce damage to biomolecules by dissociative electron attachment [2,3].In order to reach a deeper understanding of ion beam cancer therapy from a fundamental point of view, a great amount of data is needed regarding several and very diverse processes, since the whole mechanism implies steps in very different energy, space, and time scales. Therefore, the problem must be studied within a multiscale approach [4], a fact that motivates an interdisciplinary effort within the European COST Action Nano-IBCT (Nanoscale insights into ion beam cancer therapy) to build a comprehensive database [5]. In this context, ionization data for a wide variety of projectile and organic target combinations, covering a broad range of incident and ejected energies, is needed in order to get insight into micro-and nanometric aspects of radiation damage to biomolecular systems. The aim of this Letter is to present a simple theoretical method that provides the above mentioned required ionization data with the use of little input information, based on the dielectric formalism [6] and some physically motivated approximations. Results are here presented for proton impact, although the methodology can be immediately extended to heavier ions, electrons, and other charged particles.Although several simple theoretical and semiempirical methods already exist nowadays to calculate the energy spectra of secondary electrons [7] (and are currently in us...

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Section: Fig 2 (Color Online)mentioning

confidence: 82%

Semiempirical Model for the Ion Impact Ionization of Complex Biological Media

et al. 2013

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“…These figures confirm the need to consider the target anisotropy, given the strong relationship between the symmetry of the initial and final MOs and the projectile trajectory. For example, for t 2 and t 3 the transition with the highest probability is from 3a 1 of H 2 O to 1s of H, and for t 4 it is from 1b 2 of H 2 O to 1s of H. This figure also shows the impact parameters at which the function bP (b) peaks (b = 4a 0 for t 2 and t 4 , b = 2.5a 0 for t 3 ) and the magnitude of the peaks (2.05a 0 for t 2 , 1.75a 0 for t 3 , and 1.25a 0 for t 4 ) for these three trajectories. In the picture for t 4 trajectory, we can observe the low, but non-negligible, contribution of SEC transitions into H(2l) energy levels to the total capture probabilities and, consequently, to the SEC cross sections.…”

Section: E Anisotropy and Orientation-averaged Cross Sectionsmentioning

confidence: 94%

“…Collisions between ions and molecules are relevant processes in cold plasmas, which have motivated a large amount of experimental [1][2][3][4][5][6][7] and theoretical [8][9][10][11][12] works.…”

Section: Introductionmentioning

confidence: 99%

Ab initiotreatment of charge transfer in ion-molecule collisions based on one-electron wave functions

et al. 2012

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Two simple ab initio methods based on one-electron wave functions are employed to calculate the singleelectron capture and single ionization of H 2 O and CO molecules by ion impact. The anisotropy of the molecular targets is taken into account by using multicenter pseudopotentials to represent the interaction of the active electron with the ionic molecular core. These two methods are applied to the study of three collisional systems: H + + H 2 O, He 2+ + H 2 O, and C 2+ + CO. Comparison with experiments and other theoretical works is presented when available.

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“…We can at first mention the work of Dagnac et al [4] where total cross section measurements have been reported for SI and SC induced by protons with impact energies ranging from 2 to 60keV. Later on, Rudd et al [5] have published SI and SC total cross sections for 7-4000keV protons whereas Bolorizadeh and Rudd [6] reported doubly differential (differential in energy and angular transfers) and total SI cross sections for proton energies ranging from 15 to 150keV. More recently, Toburen [7] have reported total cross sections for electron capture by protons on water vapour.…”

Section: Introductionmentioning

confidence: 99%

Total cross sections for ionizing processes induced by proton impact on molecules of biological interest: A classical trajectory Monte Carlo approach

Lekadir

Abbas

Champion

et al. 2009

Nuclear Instruments and Methods in Physics Research Section B:

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In the current work, we present a study of ionizing interactions between protons and molecular targets of biological interest like water vapour and DNA bases. Total cross sections for single and multiple ionizing processes are calculated in the Independent Electron Model and compared to existing theoretical and experimental results for impact energies ranging from 10keV/amu to 10MeV/amu. The theoretical approach combines some characteristics of the Classical Trajectory Monte Carlo method with the Classical Over-Barrier framework. In this "mixed" approach, all the particles are described in a classical way by assuming that the target electrons are involved in the collision only when their binding energy is greater than the maximum of the potential energy of the system {projectile-target}. We test our theoretical approach on the water molecule and the obtained results are compared to a large set of data and a reasonable agreement is generally observed specially for impact energies greater than 100keV, excepted for the double ionization process for which large discrepancies are reported. Considering the DNA bases, the obtained results are given without any comparison since the literature is till now very poor in terms of cross section measurements.

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Angular and energy dependence of cross sections for ejection of electrons from water vapor. II. 15–150-keV proton impact

Cited by 107 publications

References 18 publications

Semiempirical Model for the Ion Impact Ionization of Complex Biological Media

Semiempirical Model for the Ion Impact Ionization of Complex Biological Media

Ab initiotreatment of charge transfer in ion-molecule collisions based on one-electron wave functions

Total cross sections for ionizing processes induced by proton impact on molecules of biological interest: A classical trajectory Monte Carlo approach

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