Non-adiabatic Strong Field Ionization of Atomic Hydrogen

TL;DR

This study investigates non-adiabatic strong field ionization of atomic hydrogen using femtosecond laser pulses, revealing experimental results that align with numerical solutions and challenge standard Coulomb-based predictions.

Contribution

It provides the first experimental data on non-adiabatic ionization of hydrogen and introduces a model accounting for non-adiabatic corrections to explain observed electron emission angles.

Findings

Observation of four ATI peaks in electron spectra.

Most probable emission angle increases with energy, contrary to standard models.

Model including non-adiabatic corrections explains the angle trend.

Abstract

We present experimental data on the non-adiabatic strong field ionization of atomic hydrogen using elliptically polarized femtosecond laser pulses at a central wavelength of 390 nm. Our measured results are in very good agreement with a numerical solution of the time-dependent Schr\"odinger equation (TDSE). Experiment and TDSE show four above-threshold ionization (ATI) peaks in the electron's energy spectrum. The most probable emission angle (also known as 'attoclock-offset angle' or 'streaking angle') is found to increase with energy, a trend that is opposite to standard predictions based on Coulomb interaction with the ion. We show that this increase of deflection-angle can be explained by a model that includes non-adiabatic corrections of the initial momentum distribution at the tunnel exit and non-adiabatic corrections of the tunnel exit position itself.