Confirmation of Kramers-Henneberger Atoms

TL;DR

This paper confirms the existence of Kramers-Henneberger atoms by showing that including their binding energy in calculations aligns theoretical predictions with experimental measurements of atom acceleration in strong laser fields.

Contribution

The study introduces the consideration of the KH atom's binding energy in velocity calculations, resolving discrepancies between theory and experiment.

Findings

Including KH binding energy improves velocity prediction accuracy.

The KH term accounts for the systematic velocity discrepancy.

Experimental velocities match theoretical predictions when KH effects are considered.

Abstract

In a remarkable experiment, Eichmann et al. attained unprecedented acceleration of neutral atoms by strong short-pulse IR laser fields. The driving mechanism was identified as the ponderomotive force on excited electrons bound in Rydberg orbits that survive long enough to enable the atoms to reach the detector. However, the observed velocities lie somewhat above the theoretical prediction. The systematic discrepancy was attributed to "absolute laser intensity uncertainties or a slightly non-Gaussian intensity distribution". Here, we examine the process by transforming to the Kramers-Henneberger (KH) reference frame. We find that in addition to the ponderomotive potential there exists a smaller but significant term that comes from the binding energy of the KH atom. Including this KH term brings the calculated maximum velocities to a close match with experimental results over the full range of laser pulse durations.