Ac-Stark shift and photoionization of Rydberg atoms in an optical dipole trap

Abstract

We have measured the ac-Stark shift of the 14D5/2 Rydberg state of rubidium 87 in an optical dipole trap formed by a focused CO2 laser. We found good quantitative agreement of the result with the model of a free electron experiencing a ponderomotive potential in the light field. In order to reproduce the observed spectra, we take into account the broadening of the Rydberg state due to photoionization. The extracted cross section is compatible with previous measurements on neighboring Rydberg states. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.