The Contribution of the Atomic Excitation and Recollision Effect during Tunneling Ionization on the Transition Rate
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The Contribution of the Atomic Excitation and Recollision Effect during Tunneling Ionization on the Transition Rate1 K. Isakovića,*, V. Petrovića, and H. Delibašića aFaculty
of Science, University of Kragujevac, Kragujevac, Serbia *e-mail: [email protected]
Received April 24, 2018; revised April 24, 2018; accepted May 30, 2018
Abstract—We used the Dykhne formalism to develop an analytical model for correlated simultaneous ionization excitation process of two-electron helium-like atoms in a strong laser field, and then analyzed the contribution of recollision effect on transition rate in a linearly polarized laser field. Also, we briefly discussed recollision effect in a circularly and linearly polarized laser field. We were interested to examine how atomic excitation and recollision affect the transition rate because observations indicated the significance of both processes on the tunneling ionization of atoms in a linearly polarized laser radiation. We showed that, under the conditions considered here, the aforementioned effects play an important role and, therefore, must be taken into account in the case of a linear polarization, while the recollision effect do not affect the rate in a circular polarization. DOI: 10.1134/S1063776119010138
1. INTRODUCTION The ionization is one of the most fundamental and important problem in atomic (molecular) physics which provides insight into the physics of the interaction of an intense laser field with an atom or molecule, and extends our knowledge of the laser-matter interaction. It was found [1, 2] that for a linearly polarized light the yields of doubly and multiply charged ions exceeded those predicted for independent successive removals of two or more electrons by many orders of magnitude. It was postulated that some form of electron correlation caused the mentioned rate’s enhancement. Because of that, a tremendous amount of both theoretical and experimental studies has been dedicated to the understanding of the correlated multielectron dynamics driven by the strong laser field. As a result, two possible theories were developed. The first one was developed by Fittinghof et al. [3] and introduced a “shake-off” mechanism. The first electron leaves the atom so rapidly that the remaining electron goes to the excited state, and both electrons leave the atom simultaneously. The second says that rate’s enhancement is caused by a recollision effect which predicts that an electron that tunnels from the atom is then driven back by the oscillating field, interacts with its parent ion, and knocks out one or more electrons [4, 5]. The secondary electrons can be ionized through two different processes. Firstly, directly through the 1 The article is published in the original.
recollision in the process of ionization, and secondly, electron can be excited through the recollision and then ionized with subsequent laser field [6]. Both [3, 4] obtained results in excellent agreement with the measurements of ion yields for helium. Theoretical approaches for a
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