Electron loss from the four DNA nucleobases, namely, adenine, cytosine, thymine, and guanine as well as from RNA uracil base produced by high-energy impact of multiply charged bare ions are here theoretically investigated via a simple model combining two classical approximations-the classical trajectory Monte Carlo and the classical overbarrier-previously used with success to describe the ionization of water molecules by ions. We give in the present work an estimation of the single-electron ionization and single-electron capture cross sections for different incident projectiles, namely, H + , He 2+ , and C 6+ ions with impact energies ranging from 10 keV/amu to 10 MeV/amu. The obtained results are compared to the rare theoretical predictions available in the literature and therefore highlight binding effects whose existence has been already demonstrated in the case of atomic collisions but not for ͑so͒ large molecular systems.
A classical trajectory model has been used to predict total cross sections of single and double ionizing processes (including capture processes) for several ion-biological molecule collisional systems in the intermediate and high energy range. In this work, the systems studied are water, adenine or cytosine targets ionized by protons and alpha-particles with kinetic energies ranging from 25 keV amu(-1) to 3000 keV amu(-1). In our approach, we have combined several features of two classical methods namely the classical trajectory Monte Carlo (CTMC) and the classical over-barrier (COB) models. For the water target, our results are compared, for high kinetic energies of incident particles, to the available experimental and theoretical results, and reasonable agreement are generally observed especially for the single ionization (liberated electron moves freely after the collision) and the single capture (liberated electron captured by the projectile), both processes representing ionizing processes. Considering the double ionizing processes which have been largely less studied, the unique comparison concerns the double capture process for alpha+H(2)O collision for which we reproduce the experiment reasonably well. Finally, we present total cross sections of single and double ionizing processes for biological targets such as adenine and cytosine where no experimental results exist till now.
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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