Transition from non-sequential to sequential double ionisation in many-electron systems

TL;DR

This paper investigates the transition from non-sequential to sequential double ionisation in heavy atoms and molecules under mid-infrared laser fields, revealing the intensity threshold and potential for studying ultrafast molecular dynamics.

Contribution

It provides the first clear experimental identification of the ionisation transition in Xe and proposes using this process to explore molecular dynamics with femtosecond resolution.

Findings

Transition occurs below 10^{14} Wcm^{-2} in Xe

Ionisation from Xe 5s orbital is crucial at low intensities

Sequential double ionisation can probe molecular dynamics in molecules

Abstract

Obtaining a detailed understanding of strong-field double ionisation of many-electron systems (heavy atoms and molecules) remains a challenging task. By comparing experimental and theoretical results in the mid-IR regime, we have unambiguously identified the transition from non-sequential (e,2e) to sequential double ionisation in Xe and shown that it occurs at an intensity below $10^{14}$ Wcm$^{-2}$. In addition, our data demonstrate that ionisation from the Xe 5s orbital is decisive at low intensities. Moreover, using the acetylene molecule, we propose how sequential double ionisation in the mid-IR can be used to study molecular dynamics and fragmentation on unprecedented few-femtosecond timescales.