Single- and multiple-electron processes in water molecules colliding with proton beams

Abstract

Single- and multiple-electron removal processes (ionization, capture and transfer-ionization) from water molecules by the impact of protons have been studied. A prior version of the three-body continuum distorted wave-eikonal initial state (3B-CDW-EIS) approximation within the independent electron approximation is used to calculate transition probabilities as a function of the impact parameter and consequently pure and net absolute cross sections for the collisions under consideration. A unitarization procedure is employed to avoid possible overestimation of the 3B-CDW-EIS single-particle impact parameter probabilities at intermediate collision energies. Multiple-electron transitions are determined using a statistical multinomial distribution. A critical analysis of the validity of this type of distribution for describing pure single-electron processes is presented. The results are compared with other theoretical calculations and available experimental data at impact energies from 50 keV to 5 MeV. New physical insights into the reactions studied are introduced.

Multi-charged ion-water molecule collisions in a classical-trajectory time-dependent mean-field theory

“…Regarding the direct study of basic ion-molecule electronic processes, we find a variety of works dedicated to proton collisions in the literature, both experimentally [17][18][19][20][21][22][23] and theoretically [24][25][26][27][28]. This is due to the fact that hadron therapy has been applied mostly with proton beams; however, it is being investigated if the use of other species which could have better physical and radiobiological properties, such as helium (alpha particles), bare carbon or oxygen ions [29], will provide other options.…”

Independent atom model description of multiple ionization of water, methane, and ammonia molecules by proton impact

“…Other theoretical approaches for collisions with water molecules with attempts to describe charge-state correlated cross sections include quantum treatments using Continuum Distorted Wave (CDW) approaches [21][22][23], as well as classical-trajectory calculations with model potentials [24]. These approaches have also been used to describe the ionized electron differential cross sections, but we have not found comparisons with the q-fold electron removal data of Werner et al [16] which were derived in Ref.…”

Classical-trajectory model for ionizing proton-ammonia molecule collisions: the role of multiple ionization

“…A number of approaches has been used for the water vapour target given its significance for radiotherapy. Among the quantummechanical methods from stationary scattering theory are the Born approximation [1,2], as well as versions of the continuum distorted wave (CDW) theory [3][4][5][6][7][8][9]. Within the semiclassical approximation to the nuclear motion there were attempts to solve the time-dependent Schrödinger equation (TDSE) within a mean-field approximation, or density functional theory [10][11][12].…”