Aggregation effects in proton collisions with water dimers

Abstract

Abstract. Charge transfer cross sections in proton collisions with water dimers are calculated using an ab initio method based on molecular orbitals of the system. Results are compared with their counterpart in proton-water collisions to gauge the importance of intermolecular interactions in the cross sections. IntroductionIon collisions with water molecules are basic processes in hadron therapy since they give rise to ionization and fragmentation processes that produce electrons, ions and radicals, which lead to cellular damage by interaction with DNA. Detailed knowledge of ionizing reactions in ion-water collisions is also required for the simulation of the ion motion in the cell medium, where the simulation of the cell conditions requires to consider the interaction of ion projectiles with liquid water. However, previous theoretical and experimental work has focused on ion collisions with gas-phase water.In order to gauge the importance of the interaction between water molecules on the relevant cross sections, we have considered proton collisions with the water dimer. To our knowledge, no other work has studied ion collisions with this species, and only Bouchiha et al [1] carried out calculations for electron-water dimer collisions. A different approach has been applied by Champion [2], who has employed the so-called Polarizable Continuum Model [3] to simulate the interaction of the water molecule involved in electron collisions with the liquid environment. In the present work, we have evaluated total cross sections for charge transfer (CT),