Ionization of water molecules by proton impact: Two nonperturbative studies of the electron-emission spectra

Abstract

Two nonperturbative methods are applied to obtain total and singly differential (in the electron energy) cross sections of electron emission in proton collisions with H 2 O at impact energies in the range 10 keV E p 5 MeV. Both methods, one classical and one semiclassical, combine an independent particle treatment with a multicenter model potential description of the target. The excellent agreement obtained with experimental data supports the usefulness of the approximations involved and encourages the study of more complex systems.

Lattice description of electron loss in high-energy H++H2O collisions

“…In this respect, the aim of the present work is to gauge the usefulness of a method based on the numerical solution of the time-dependent Schrödinger equation (TDSE), comparing the results with those of ref. [13], which lead to electron-loss total cross sections in good agreement with the experimental data at collision energies above 25 keV/u [22,23,24].…”

“…The description of the initial wavefunctions in the lattice calculation has been checked by comparing the energies of the MOs, calculated with a Lanczos propagation scheme, with those obtained by solving the secular equation for h T in the the basis of Gaussian-Type-Orbitals (GTO) of reference [13] and the same model potential . In Table 1 we show this comparison for the three highest occupied MOs with two grid densities (G10: 10 points/a 0 on each direction; G25: 25 points/a 0 on each direction).…”

“…the results of the numerical calculations are shown and compared to those of Ref. [13] in section 3. A brief summary is presented in section 4.…”

“…Previous calculations on ionization in ion -H 2 O collisions generally employ the independent electron approximation that assumes that the active electron moves in the average field created by the nuclei and the other electrons. In particular, electron capture and ionization cross sections have been calculated by applying the first Born approximation [3], the continuumdistorted-wave method [4,5,6,7,8,9,10], the classical trajectory Monte Carlo (CTMC) [11,12,13,14] and the semiclassical treatment with pseudostates [15,16,17,18]. The one-electron probabilities yielded by these calculations are then combined (see [19,20]) to obtain the probabilities for the many-electron processes.…”

Calculation of Stark resonance parameters for valence orbitals of the water molecule

“…The study of water molecule vapour in strong fields has been an area of recent interest, particularly in the field of intermediate-energy ion-molecule collisions [1][2][3][4][5][6][7], where capture and direct ionization processes compete. Most of the theoretical studies are in the context of an independent-electron approximation which involves a molecular orbital (MO) representation.…”