Abrupt Rise of the Longitudinal Recoil Ion Momentum Distribution for Ionizing Collisions

We report on the experimental observation of an abrupt rise in the longitudinal momentum distribution of recoil ions created in proton helium collision. The details of this structure can be related to electrons traveling with the velocity of the projectile [electron capture to the continuum (ECC)]. The longitudinal as well as the transverse distribution of the recoil ions can be explained as a continuation of the momentum distribution from ions resulting from electron capture illustrating the smooth transition from the capture to bound states of the projectile to the ECC.Fil: Weber, Th.. Institut für Kernphysik; AlemaniaFil: Khayyat, Kh.. Institut für Kernphysik; AlemaniaFil: Dörner, R.. Universität Freiburg; AlemaniaFil: Rodríguez Chariarse, Vladimir Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Mergel, V.. Institut für Kernphysik; AlemaniaFil: Jagutzk, O.. Institut für Kernphysik; AlemaniaFil: Schmidt, L.. Institut für Kernphysik,; AlemaniaFil: Müller, K. A.. Institut für Kernphysik; AlemaniaFil: Afaneh, F.. Institut für Kernphysik; AlemaniaFil: Gonzalez, A.. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Schmidt-Böcking, H.. Institut für Kernphysik; Alemani

Positronium ionization by short UV laser pulses: Splitting of the ATI peaks by Rabi oscillations

The interaction between positronium and a short laser pulse is studied in the case, where the photon energy is resonant with the 1s → 2p transition energy. Results from a full numerical solution of the time-dependent Schrödinger equation, and also from a variational approach based on the Coulomb-Volkov wave function to describe the final states are presented. For the initial state, a solution of the time-dependent Schrödinger equation involving the two resonantly bound states is used. This wave function exhibits Rabi oscillations as the laser amplitude increases. Using the rotating wave approximation the contribution from N-photon and (N - 1)-photon ionization from ground and excited state with split energy levels can be identified. The theory predicts each above threshold ionization primary peak split in two peaks separated by half an appropriate Rabi frequency. It is suggested that this phenomenon could be experimentally measured by the Aarhus group working on positronium in laser fields. © 2006 Elsevier B.V. All rights reserved.Fil: Rodríguez Chariarse, Vladimir Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin

CDW-EIS theoretical calculations of projectile deflection for single ionization in highly charged ion-atom collisions

We present continuum distorted wave-eikonal initial state (CDW-EIS) theoretical calculations for the projectile deflection in single ionization of helium by heavy-ion impact as a function of ionized electron energies. These calculations account for the helium passive electron shielding in the internuclear interaction improving standard CDW-EIS theory. The results are compared with recent experimental results by impact of 100 MeV/amu C6+ and 3.6 MeV/amu Au53+. For highly charged projectiles there is a poor quantitative agreement between theory and experiment. However, this refined calculation does share some qualitative features with the data. In particular the variation of the effective charge of the residual He+ ion from Zeff = 1 to Zeff = 2 when going from small to large projectile scattering angles is able to represent a shoulder observed in the double differential cross sections. Important qualitative differences are observed at the level of triple differential cross sections. © 2003 Published by Elsevier Science B.V.Fil: Rodríguez Chariarse, Vladimir Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin

Ionization by short uv laser pulses: Secondary above-threshold-ionization peaks of the electron spectrum investigated through a modified Coulomb-Volkov approach

Coulomb-Volkov approach was applied for investigating the interaction between an atom and a short laser pulse in case where both photon energies were smaller than the ionization potential. The secondary peaks show up in the above-threshold ionization (ATI) spectrum, as indicated by a full numerical solution of the time-dependent Schrödinger equation for a hydrogen atom initially in its ground state. A full numerical electron spectrum for smaller photon energies was obtained by introducing a coupling to intermediate bound states into the applied approach. The secondary peaks for the excitation of transient bound states followed by multiphoton absorption were easily traced with the help of the approach.Fil: Rodríguez Chariarse, Vladimir Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Cormier, E.. Centre Lasers Intenses Et Applications; Estados UnidosFil: Gayet, R.. Centre Lasers Intenses Et Applications; Estados Unido

Thomas mechanism in electron capture to the continuum

For the electron capture to the continuum (ECC) processes in ion-atom ionizing collisions, Thomas mechanism was theoretically shown to be present. A prominent peak structure, from the backward direction was observed near the kinematical threshold, by focusing on the recoil-ion momentum distribution. Recoil-ion critical angles corresponded to the Thomas double-scattering mechanism for electron capture.Fil: Rodríguez Chariarse, Vladimir Daniel. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Barrachina Tejada, Raul Oscar. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentin

Unitary model for atomic ionization by an intense laser pulse

A unitary model describing the electronic transitions in an atom interacting with a laser pulse is proposed. The model includes the initial state coupling with the continuum spectrum. Continuum-continuum transitions are neglected although transitions from the initial state to other discrete states within the first Born approximation are considered. The model leads to a single integro-differential equation for the initial state amplitude which is numerically solved. The results are compared with TDSE simulations for Hydrogen atoms.Fil: Bustamante Pilone, Manuel Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Rodríguez Chariarse, Vladimir Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin

Ionization of atomic hydrogen by an intense resonant laser pulse

The ionization of atomic hydrogen by an intense laser field resonant with the transition ls-Spo is studied. The intensity of the field is strong enough to make the Rabi oscillations important. The theoretical treatment of this work is based on a modified form of the Coulomb-Volkov approximation. The decay to the continuum is accounted by coupling the initial and the excited resonant states to the continuum part of the atomic spectrum. A system of integro-differential equations numerically solved is obtained. The results obtained in this work have been tested against the numerical solution of the time-dependent Schrodinger equation. Good agreement has been obtained. ATI peaks splitting related to the Autler-Townes effect is discussed.Fil: Bustamante Pilone, Manuel Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Rodríguez Chariarse, Vladimir Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin

Dynamic Stark effect and the Coulomb-Volkov approximation

A modified Coulomb-Volkov theory is used to study the interaction of intense laser pulses with atomic Hydrogen. Photon energy greater than the ionization potential and non-perturbative conditions are considered. The dynamical Stark effect is accounted by introducing the initial state coupling to the remaining discrete and continuum atomic spectrum. Both the Stark shift and the decay of the initial state are studied. The ionization spectra, the Stark shift and the total ionization probability are compared with results obtained from numerical solution of the time dependent Schrödinger equation. Both results agree well.Fil: Bustamante Pilone, Manuel Guillermo. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Rodríguez Chariarse, Vladimir Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin

Gauge independent theory applied to a model of atomic ionization by an intense laser pulse

An explicitly gauge invariant strong field theory is introduced and tested using a model laser-atom interaction. The theory relies on a power series in the target potential. Transitions amplitudes are obtained by using a corresponding series in the momentum space wave function. We demonstrate that this approach is explicitly gauge invariant to all orders. A well know 1D delta function potential model is used to test the convergence of the series in the evaluation of total ionization probabilities and ionization spectra. Actually, the convergence is verified when both, the perturbation as well as the order of the expansion, are increased. © 2011 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.Fil: Rodríguez Chariarse, Vladimir Daniel. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Barrachina Tejada, Raul Oscar. Universidad Nacional de Cuyo; Argentin

Theory of longitudinal recoil-ion momentum distribution in ion-atom ionization

The longitudinal recoil-ion momentum distributions of single ionization in collisions between fast heavy ions and atoms are analyzed by exploring the three-body kinematics and its relation to dynamic processes. It is found that there is a kinematic threshold for the longitudinal recoil-ion momentum distributions that can be ascribed to electron capture to the continuum (ECC). The finite cross section at threshold provides unambiguous evidence of the divergence of the ECC peak when the electron velocity is equal to the projectile velocity. Other aspects associated with the ionization process, such as soft-electron emission and binary-encounter collision, are also studied. Theoretical longitudinal recoil-ion momentum distributions are also compared to existing experiments. © 1995 The American Physical Society.Fil: Rodríguez Chariarse, Vladimir Daniel. Physics Department; Estados Unidos. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Wang, Y.D.. Physics Department; Estados UnidosFil: Lin, C.D.. Physics Department; Estados Unido