Delayed double ionization as a signature of Hamiltonian chaos

TL;DR

This paper investigates how delayed double ionization in atoms under strong laser fields is a manifestation of Hamiltonian chaos, highlighting the role of unstable periodic orbits and predicting oscillations in ionization yields with laser intensity.

Contribution

It demonstrates the connection between delayed double ionization and Hamiltonian chaos using reduced models, emphasizing the importance of unstable manifolds and model dimensionality.

Findings

Delayed double ionization is linked to Hamiltonian chaos.

Oscillations in RESI to double ionization ratio are predicted.

Unstable manifolds of periodic orbits influence ionization delays.

Abstract

We analyze the dynamical processes behind delayed double ionization of atoms subjected to strong laser pulses. Using reduced models, we show that these processes are a signature of Hamiltonian chaos which results from the competition between the laser field and the Coulomb attraction to the nucleus. In particular, we exhibit the paramount role of the unstable manifold of selected periodic orbits which lead to a delay in these double ionizations. Among delayed double ionizations, we consider the case of "Recollision Excitation with Subsequent Ionization" (RESI) and, as a hallmark of this mechanism, we predict oscillations in the ratio of RESI to double ionization yields versus laser intensity. We discuss the significance of the dimensionality of the reduced models for the analysis of the dynamical processes behind delayed double ionization.