Rydberg states and momentum bifurcation in tunnel ionization with elliptically polarized light

TL;DR

This paper introduces a new analytical method to understand how Rydberg state formation in tunnel ionization depends on laser ellipticity, challenging previous rescattering-based explanations and revealing a bifurcation in Rydberg generation.

Contribution

It provides a novel probability distribution model for Rydberg states that aligns with experimental data and shows the Rydberg yield dependence is not due to rescattering, including an analytic derivation with Coulomb force.

Findings

Rydberg yield decreases with increasing ellipticity.

Most Rydberg electrons do not return near the atom after ionization.

A bifurcation in Rydberg generation corresponds to a cut-off point.

Abstract

It is well-known from numerical and experimental results that the fraction of Rydberg states (excited neutral atoms) created by tunnel ionization declines dramatically with increasing ellipticity of laser light. We present a method to analyze this dependence on ellipticity, deriving a probability distribution of Rydberg states that agrees closely with recent experimental [1] and numerical results. In particular, contradicting the existing proposed mechanism [1] and general expectations, our results indicate that the dependence of Rydberg yield on laser ellipticity is not caused by a rescattering process. Rather, we show that most Rydberg electrons never come back to the vicinity of the exit point after ionization, and end up relatively far from the atom (compared to the exit point) after the laser pulse has passed. We also present experimental data revealing a bifurcation that corresponds to a cut-off in Rydberg generation, and present an analytic derivation with a perturbative inclusion of the Coloumb force. [1] T. Nubbemeyer, K. Gorling, A. Saenz, U. Eichmann, and W. Sandner, Phys. Rev. Lett. 101, 233001 (2008).