ATOMIC IONIZATION BY SUDDEN MOMENTUM TRASFER

D. G. ARBÓ, K. TőKÉSI, AND J. E. MIRAGLIA

Cluj-Napoca, Rumania

Conferencia; 4th Conference on Elementary Processes in Atomic Systems; 2008

The Coulomb-Volkov approximation (CVA) is a time-dependent distorted-wave theory [1-4] which allows us to include the effect of the remaining core into the final state at the same approximation level as it can be performed for the case of the external field. In this work we present a theoretical study of the electron distributions ejected from hydrogen atoms as a result of the ionization by a sudden momentum transfer. We apply the CVA and the classical trajectory Monte Carlo (CTMC) [5] method to determine the doubly-differential electron momentum distribution and the final angular momentum. We show that the CVA reproduces the exact solution of the time dependent Schrödinger equation in the limit of zero pulse duration but with finite momentum transfer. Results are also compared with the values obtained by the strong-field approximation (SFA). It is noted that quantum and classical dynamics of the atomic electron suffering a kick are identical; nevertheless pronounced differences arise from the subsequent electron-nucleus interaction for small momentum transfers. These increased when the momentum transfer decreases, where the classical total ionization probabilities are smaller than the quantum one. As an example, the 2D momentum distributions of the electron yield ionized by a kick with strength Δp = 2.5 is shown in Fig. 1. Quantum mechanics brings in one lobe in the forward direction [Fig. 1a] which can be very accurately reproduced by CTMC [Fig. 1b]. Comparing these results to the SFA ones [Fig. 1c] two essentially effects due to the effect of the attractive Coulomb field can be noticed: (i) the center of the full quantum and classical distributions are slightly shifted towards the origin with respect to the SFA (the center is situated exactly at kz = Δp, and (ii) the full quantum and classical momentum distributions are weakly distorted near the origin (k=0).