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Causality and quantum interference in time-delayed laser-induced nonsequential double ionization

Shaaran, Tahir and Figueira de Morisson Faria, C. and Schomerus, Henning (2012) Causality and quantum interference in time-delayed laser-induced nonsequential double ionization. Physical Review A, 85 (2). ISSN 1050-2947

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    Abstract

    We perform a detailed analysis of the importance of causality within the strong-field approximation and the steepest-descent framework for the recollision-excitation with subsequent tunneling ionization (RESI) pathway in laser-induced nonsequential double ionization (NSDI). In this time-delayed pathway, an electron returns to its parent ion and, by recolliding with the core, gives part of its kinetic energy to excite a second electron at a time t′. The second electron then reaches the continuum at a later time t by tunneling ionization. We show that, if t′ and t are complex, the condition that recollision of the first electron occurs before tunnel ionization of the second electron translates into boundary conditions for the steepest-descent contours and thus puts constraints on the saddles to be taken when computing the RESI transition amplitudes. We also show that this generalized causality condition has a dramatic effect on the shapes of the RESI electron momentum distributions for few-cycle laser pulses. Physically, causality determines how the dominant sets of orbits of an electron returning to its parent ion can be combined with the dominant orbits of a second electron tunneling from an excited state. All features encountered are analyzed in terms of such orbits and their quantum interference.

    Item Type: Article
    Journal or Publication Title: Physical Review A
    Additional Information: ©2012 American Physical Society
    Subjects: Q Science > QC Physics
    Departments: Faculty of Science and Technology > Physics
    ID Code: 52796
    Deposited By: ep_importer_pure
    Deposited On: 13 Mar 2012 09:05
    Refereed?: Yes
    Published?: Published
    Last Modified: 09 Apr 2014 23:08
    Identification Number:
    URI: http://eprints.lancs.ac.uk/id/eprint/52796

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