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Nonadiabatic ionization dynamics with circular polarization

Focus

It is well known that the presence of an external, static, field distorts the orbitals of atomic and molecular species, most often leading to ionization with some defined rate. In the framework of strong-field physics it is then obvious that laser sources have similar effects. Yet, the fast time profile of the laser electric field raises the question of the overall role of the dynamics in ionization. This question is often eluded by considering an adiabatic approximation, treating the system at each time with an instantaneous representation of the quantum mechanical system, as if the laser field is static. On the contrary, we show that non-adiabatic effects, mostly due to the laser frequency and resulting from the overall interaction with the laser, lead to ionization rates and yields departing up to more than one order of magnitude from the adiabatic, static-field like, configuration for circularly polarized fields. Following the principle that similar causes should produce similar consequences, it casts doubts on the applicability of the adiabatic approximation for all polarizations and beyond atomic species. Our results call for further and more careful analysis of laser–matter interaction, both from the theoretical and experimental points of view.

Associated publication

Electronic dynamics and frequency effects in circularly polarized strong-field physics

posted May 13, 2016, 10:51 PM by François Mauger   [ updated May 13, 2016, 11:19 PM ]

Abstract

We analyze, quantum mechanically, the dynamics of atomic ionization with a strong, circularly polarized, laser field. We show that the main source for non-adiabatic effects, defined as the deviations from the static-field configuration with corresponding instantaneous amplitude, is connected to an effective barrier lowering due to the laser frequency. Such non-adiabatic effects manifest themselves through ionization rates and yields that depart up to more than one order of magnitude from a static-field configuration which we take as a reference for comparison. As a rule of thumb, such non-adiabatic manifestations get stronger with increasing laser frequency. Beyond circular polarization and atomic targets, these results show the limits of standard instantaneous -- static-field like -- interpretation of laser-matter interaction and the great need for including time-dependent electronic dynamics.

Reference

F. Mauger, and A.D. Bandrauk - Electronic dynamics and frequency effects in circularly polarized strong-field physics - Journal of Physics B: Atomic, Molecular and Optical Physics 47, 191001 (2014)

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