IAFE   05512
INSTITUTO DE ASTRONOMIA Y FISICA DEL ESPACIO
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
ANGULAR MOMENTUM IN ATOMIC IONIZATION BY SHORT LASER
Autor/es:
D. G. ARBÓ, K. I. DIMITRIOU, E. PERSSON, AND J. BURGDÖRFER
Lugar:
Cluj-Napoca, Rumania
Reunión:
Conferencia; 4th Conference on Elementary Processes in Atomic Physics; 2008
Resumen:
In atomic ionization by few-cycle laser pulses doubly-differential momentum distributions near threshold exhibit a radial nodal structure that results from peaked partial wave distribution near a particular angular momentum [1]. Recently, two different mechanisms were proposed to nderstand the populations of the different partial waves: (i) A biased random walk model assuming stochastic uncorrelated multi-photon processes [2], and (ii) a quasiclassical tunneling ionization process [1] calculated using classical-trajectory Monte-Carlo [3] simulations which incorporate tunneling through the potential barrier (CTMC-T). We compare these two models to results of momentum distribution of emitted electrons by solving the time dependent Schrödinger Equation (TDSE) and analyze near-threshold structures for different atomic species of the target. It can be observed in Fig. 1 that both random walk multiphoton and quasiclassical tunneling model can predict the first moment of the TDSE distribution. However, in a Poissonian random walk model a broad distribution is observed at variance with both the TDSE and the quasiclassical CTMC-T results. For Keldysh parameters below or close to one, the narrow angular momentum distribution near threshold is the result of a tunneling process at variance with a broad Poissonian distribution resulting from a multiphoton random walk. We also find that the dominant angular momentum near threshold depends strongly on the laser frequency and peak field but not on the atomic species. This relation is reminiscent of generalized Ramsauer-Townsend diffraction oscillations [1]. As in the case of electron-ion scattering theory [4], it results from the existence of interfering paths under the influence of two competing forces: the atomic Coulomb potential and the electric field of the laser.