A E Martínez

Theoretical Calculation of Electronic Stopping Power of Water Vapor by Proton Impact

The energy loss of proton beams in water vapor is analyzed with a full quantum-mechanical treatment, the distorted-wave model. This model takes into account distortion effects due to the long-range Coulomb potential. Projectile energies from 10 keV up to 1 MeV are considered. Mean stopping power and equilibrium charge-state fractions are calculated and compared with experimental data. The validity of Braggs additivity rule is investigated.

K-Shell vacancy production in asymmetric collisions

Abstract The Continuum Distorted Wave-Eikonal Initial State approximation is introduced to describe electron capture in ion-atom collisions. The model had been previously studied to represent electron ionization. Theoretical total cross sections for both processes are compared with experimental data for impact of light bare ions on heavier targets.

CDW-EIS model for single-electron capture in ion-atom collisions involving multielectronic targets

A generalization of the continuum distorted wave eikonal initial state (CDW-EIS) approximation, for the description of single-electron capture in ion–atom collisions involving multielectronic targets is presented. This approximation is developed within the framework of the independent electron model taking particular care of the representation of the bound and continuum target states. Total cross sections for single-electron capture from the K-shell of He, Ne and Ar noble gases by impact of bare ions are calculated. Present results are compared to previous CDW-EIS ones and to experimental data.

Double electron capture by fast bare ions in helium atoms: production of singly and doubly excited states

Double electron capture by fast bare ions in helium is studied in the framework of the Four-Body Continuum Distorted Wave theory. It is shown that experimental data is well reproduced when the theoretical total cross-section include both contributions from the ground state and from the first singly excited states. In addition, cross-sections for the production of the first doubly excited states are also calculated. Present results call for additional experimental data at higher impact energies than presently available.

Single electron capture differential cross section in H+ + He collisions at intermediate and high collision energies

The generalized continuum distorted wave-eikonal initial state (CDW-EIS II) approximation is employed to study differential cross sections (DCS) for single electron capture in H+ + He collisions at intermediate and high energies. Present results are compared with theoretical calculations obtained using the previous CDW-EIS formulation in order to show the importance of the description of the bound and continuum target states in the entrance and exit channels, respectively. Both DCS are also shown together with other theoretical results and with experimental data.

The continuum distorted wave eikonal initial state model for transfer ionization in H+, He2+ + He collisions

We employ the independent-event model to study the transfer-ionization (TI) process in H+, He2+ + He collisions. We consider both the ionization-capture and capture-ionization paths. The single-particle probabilities for all channels are calculated with the continuum distorted wave eikonal initial state model. With the probabilities for TI we calculate doubly differential and total cross sections which are compared with the available experimental data. Our present results are in better agreement with the experiments than present calculations using the independent-electron model and previous calculations using the independent-event model, but with single-particle probabilities calculated with the continuum distorted-wave model.

Single electron capture from He targets

Single electron capture by impact of bare heavy ions on He targets is studied for intermediate and high collision energies. We focus our analysis on the use of distorted wave models within the impact parameter approximation. For proton impact, total cross sections for capture to selective final states are presented. Results corresponding to capture to any final state are also shown for several projectiles with charge . Theoretical total cross sections calculated in the present work using the continuum distorted wave - eikonal initial state and the continumm distorted wave - eikonal final state approximations are compared with continuum distorted wave results and available experimental data. A criterion to determine which, among the distorted wave approximations analysed in the present work, is the most appropriate to describe a given collision system is discussed.

Distorted-wave models for electron capture in asymmetric collisions. II. Differential cross sections and the double scattering region

For pt. I see Phys. Scr., vol. 51, p. 190 (1994). We study the single-electron capture process by impact of protons on hydrogen atoms, at intermediate and high collision energies. The emphasis is on differential cross sections for capture to specific nlm final states. The calculations use three distorted-wave models, a symmetric one (continuum distorted-wave approximation) and two asymmetric ones (continuum distorted-wave-eikonal initial state and eikonal final-state approximations). The various sets of differential cross sections are presented and compared to available experimental data. Distinguishing features appear most notably in the double scattering region revealing the different physical content of the approximations. An analysis of the post-prior discrepancy in the asymmetric models is sketched and the validity of a previously introduced criterion to select the appropriate distorted-wave model in a specific collision is also discussed.

THe continuum distorted wave-eikonal initial state model for single electron capture in ion-atom collisions

Close analytical transition matrix elements are obtained for single electron capture from an arbitrary initial state of an atomic target to an arbitrary final state of a bare projectile by using the continuum distorted wave-eikonal initial state approximation. As an application, theoretical total cross sections for capture into 2s and 2p states of the projectile for impact of protons on H and He targets are computed. These results are compared with existing experimental data as well as with other theoretical calculations.

CDW and CDW-EIS investigations in an independent electron approximation for the resonant double electron capture by swift He2+ in helium

The CDW and CDW-EIS approximations are used to study the resonant double electron capture by He2+ in helium at intermediate and high impact velocities. Calculations of the total cross sections as a function of the impact energy are performed in an Independent Electron Approximation. A very good agreement with recent experimental data for capture into all states of the projectile is found although neither angular nor dynamical electron correlations are included in the calculations.