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

Ionization of helium by fast and highly charged ions

We present 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 projectile-residual target ion interaction through a first order static potential and a second order polarization potential. The results are compared with recent experimental data by impact of 3.6 MeV/amu Au53+. A good agreement is found. © 2007 IOP Publishing Ltd

Selection rules for electron transfer to the continuum in ion-atom collision

We consider the process of electron transfer to the continuum in first order Born approximation. We analyse the expansion of the double-differential cross section in series of electron velocity and ejection angle. We found that the coefficients obey precise selection rules. We discuss the relation of these rules, which predict an asymmetric shape for the electron loss to the continuum cusp, with the interpretation of recent experimental results.Nous considérons le processus de transfert d'un électron à un état du continuum au premier ordre de l'approximation de Born. Nous étudions le développement de la section efficace doublement différentielle en puissances de la vitesse et de l'angle d'éjection de l'électron. Les coefficients de ce développement obéissent à des règles de sélection. Nous comparons ces règles de sélection, qui prédisent une forme asymétrique pour le pic de transfert électronique vers le continuum, aux résultats expérimentaux récents

Projectile focusing near the recoil-ion threshold

The post-collisional interactions in ion-atom ionization collisions are studied around the electron capture to the continuum (ECC) process. For this purpose, a suitable double differential cross section is introduced, involving the longitudinal recoil-ion momentum and the projectile transverse momentum transfer. Using the fact that the ECC process is closely related to the threshold in the longitudinal momentum distribution, we study this distribution as a function of the projectile scattering angle. Using the CDW-EIS approximation we theoretically find a focusing (defocusing) effect as we get closer to the distribution threshold for proton (antiproton) impact on He atoms. © 2007 IOP Publishing Ltd

Initial evolution of an homogeneous Maxwell gas

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lnterférences de type Young avec une source à un seul électron

International audienceDes interférences dues à la diffusion d'un électron unique sur deux protons, qui jouent le rôle de deux trous de Young, ont été mises en évidence expérimentalement pour la première fois. L'électron provient de l'auto-ionisation de l'hélium excité après capture des deux électrons de la molécule H2 par un projectile He2+. Ces interférences se manifestent par l'apparition d'oscillations d'intensité dans la distribution angulaire des électrons diffusés. La présence de ces oscillations prouve qu'un électron peut interférer avec lui-même. L'expérience présente est analogue à une expérience de pensée imaginée par Feynman en 1963

Physique/Physique subatomique. Interférences de type Young avec une source à un seul électron

RESUME : Des interférences dues à la diffusion d'un électron unique sur deux protons, qui jouent le rôle de deux trous d'Young, ont été mises en évidence expérimentalement pour la première fois. L'électron provient de l'autoionisation de l'hélium excité après capture des deux électrons de la molécule H2 par un projectile He2+. Ces interférences se manifestent par l'apparition d'oscillations dans la distribution angulaire des électrons diffusés. La présence de ces oscillations prouve qu'un électron peut interférer avec lui-même. Cette expérience est analogue à l'expérience de pensée imaginée par Feynman en 1963, dans laquelle il retrace le devenir d'un électron après traversée de deux fentes rapprochées. Pour citer cet article : F. Frémont et al., C. R. Physique 9 (2008). ABSTRACT : Young-type interference with a one electron source. In the present work we provide experimental evidence for Young-type interferences caused by one single electron acting on a given double-center scatterer which is analogous to an atomic-size doubleslit apparatus. The interfering electron is provided by autoionization of a doubly-excited helium atom following the capture of the two H2 target electrons by a He2+ incoming projectile ion. In the backward direction, the auto-ionized electron scatters on the two H+ centers of the fully ionized target molecule. Here, the auto-ionizing projectile plays the role of a single-electron source, independent of the interferometer provided by the residual two-center target. The present experiment resembles the famous “thought experiment” imagined by Feynman in 1963, in which the quantum nature of the electron is illustrated from a Younglike double-slit experiment. Similarly to the case of Young's experiment with light, the interference effect manifests itself in well defined oscillations in the angular distribution of the scattered electrons. To cite this article: F. Frémont et al., C. R. Physique 9 (2008)

Multiple-scattering phase distortion in the ionization of molecules

We theoretically analyze the multiple-scattering effects that might occur in the ionization of a molecule by the impact of photons or massive particles, by calculating the series to all orders within a muffin-tin description. We find a large sensitivity on the final state and a sizable momentum-dependent distortion of the phase-shift and frequency of the interference oscillations, that are not replicated by non-scattering or single-scattering approximations. Furthermore, our results do not validate the existence of any discernible harmonic oscillations. © Published under licence by IOP Publishing Ltd

Linewidth oscillations in a nanometer-size double-slit interference experiment with single electrons

International audienceIn this article we provide experimental evidence of an interference phenomenon that, to the best of our knowledge, has so far not been observed with either matter or light. In a nanometer-sized version of Feynman's famous two-slit “thought” experiment with single electrons, we managed to observe that the width of a quasimonochromatic line oscillates with the detection angle. Furthermore, we find that it occurs in counterphase with the line intensity. We discuss the underlying mechanism that produces this unexpected result