Non-sequential double ionization of Ar: from the single- to the many-cycle regime

M Kübel,B Bergues,K J Betsch,R Moshammer,M F Kling,J Ullrich,A S Alnaser,U Kleineberg,Y Deng,G G Paulus,T Pfeifer,Nora G Kling,J Schmidt,I Ben-Itzhak

doi:10.1088/1367-2630/16/3/033008

Abstract

The transition from the near-single to the multi-cycle regime in non-sequential double ionization of argon is investigated experimentally. Argon atoms are exposed to intense laser pulses with a center wavelength around 790 nm and the momenta of electrons and ions generated in the double ionization process are measured in coincidence using a reaction microscope. The duration of the near transform-limited pulses is varied from 4 to 30 fs. We observe an abrupt collapse of the cross-shaped two-electron momentum distribution [] in the few-cycle regime. The transition to longer pulses is further accompanied by a strong increase in the fraction of anti-correlated to correlated electrons.

Highlights

A deeper insight into the Non-sequential double ionization (NSDI) process was provided by kinematically complete experiments where the correlated two-electron momentum distributions were measured
Correlated electron emission, in which the two electrons are ejected in the same direction, is usually attributed to direct electron impact ionization [10]
Anticorrelated electron emission, where the two electrons are ejected in opposite directions, is ascribed to recollisional excitation and subsequent ionization [9]

Summary

Introduction

A deeper insight into the NSDI process was provided by kinematically complete experiments where the correlated two-electron momentum distributions (briefly, two-electron spectrum) were measured. Owing to the great advances in ultra-fast laser technology [14, 15], two-electron spectra could recently be measured using few-cycle [16] and near-single-cycle [17] pulses with known carrier-envelope phase (CEP). The goal of the present study is to investigate the transition from single- to multi-cycle NSDI by recording correlated two-electron momentum distributions for laser-pulse durations ranging from 4 to 30 fs.

Objectives

Results

Conclusion