Sub-cycle time resolution of multi-photon momentum transfer in strong-field ionization

Benjamin Willenberg,Jochen Maurer,Ursula Keller,Benedikt W Mayer

doi:10.1038/s41467-019-13409-6

Benjamin Willenberg, Jochen Maurer + Show 2 more

Open Access

https://doi.org/10.1038/s41467-019-13409-6

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Journal: Nature Communications	Publication Date: Dec 1, 2019
Citations: 41	License type: open-access

Affiliation: ETH Zurich

Abstract

During multi-photon ionization of an atom it is well understood how the involved photons transfer their energy to the ion and the photoelectron. However, the transfer of the photon linear momentum is still not fully understood. Here, we present a time-resolved measurement of linear momentum transfer along the laser pulse propagation direction. We can show that the linear momentum transfer to the photoelectron depends on the ionization time within the laser cycle using the attoclock technique. We can mostly explain the measured linear momentum transfer within a classical model for a free electron in a laser field. However, corrections are required due to the parent-ion interaction and due to the initial momentum when the electron enters the continuum. The parent-ion interaction induces a negative attosecond time delay between the appearance in the continuum of the electron with minimal linear momentum transfer and the point in time with maximum ionization rate.

Highlights

During multi-photon ionization of an atom it is well understood how the involved photons transfer their energy to the ion and the photoelectron
Whereas the fundamental concepts of energy and momentum conservation forbid the complete absorption of the photon by the free electron[7], photons can be absorbed by a bound electron during photoionization
To the best of our knowledge, there has been no experimental study on the timedependent linear momentum transfer during photoionization – neither for single-photon nor for multi-photon ionization processes

Summary

Introduction

During multi-photon ionization of an atom it is well understood how the involved photons transfer their energy to the ion and the photoelectron. In our measurements we use the attoclock method to access the transferred linear momentum along the laser propagation direction as a function of the phase within a laser cycle at which the electron is released to the continuum.

Results

Conclusion