Angular dependence of the Wigner time delay upon tunnel ionization of H2

D Trabert,R Dörner,S Grundmann,A Geyer,M S Schöffler,M Kunitski,S Eckart,L Ph H Schmidt,N Anders,T Jahnke,K Fehre,S Brennecke

doi:10.1038/s41467-021-21845-6

D Trabert, R Dörner + Show 10 more

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https://doi.org/10.1038/s41467-021-21845-6

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Abstract

When a very strong light field is applied to a molecule an electron can be ejected by tunneling. In order to quantify the time-resolved dynamics of this ionization process, the concept of the Wigner time delay can be used. The properties of this process can depend on the tunneling direction relative to the molecular axis. Here, we show experimental and theoretical data on the Wigner time delay for tunnel ionization of H2 molecules and demonstrate its dependence on the emission direction of the electron with respect to the molecular axis. We find, that the observed changes in the Wigner time delay can be quantitatively explained by elongated/shortened travel paths of the emitted electrons, which occur due to spatial shifts of the electrons’ birth positions after tunneling. Our work provides therefore an intuitive perspective towards the Wigner time delay in strong-field ionization.

Highlights

When a very strong light field is applied to a molecule an electron can be ejected by tunneling
Let us start by considering possible, intuitive reasons for the occurrence of a Wigner time delay contribution, ΔτW,M(E,β), that depends on the molecular frame emission direction of the electron
We have measured the angular dependence of the Wigner time delay ΔτW,M in strong-field ionization of the H2 molecule

Summary

Introduction

When a very strong light field is applied to a molecule an electron can be ejected by tunneling. In order to quantify the time-resolved dynamics of this ionization process, the concept of the Wigner time delay can be used The properties of this process can depend on the tunneling direction relative to the molecular axis. The Wigner time delay, τWigner, was introduced to describe scattering processes[9] and it is defined as the derivative of the phase of the electron’s wave function ψ with respect to the electron’s energy E5,10–13:. The scope of this paper is to investigate ΔτW,M(E,β), which quantifies the changes of the Wigner time delay as a function of the relative emission direction of the electron with respect to the molecular axis for strong-field ionization by circularly polarized light

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