Detrimental adsorbate fields in experiments with cold Rydberg gases near surfaces

Abstract

We observe the shift of Rydberg levels of rubidium close to a copper surface when atomic clouds are repeatedly deposited on it. We measure transition frequencies of rubidium to $S$ and $D$ Rydberg states with principal quantum numbers $n$ between 31 and 48 using the technique of electromagnetically induced transparency. The spectroscopic measurement shows a strong increase of electric fields towards the surface that evolves with the deposition of atoms. Starting with a clean surface, we measure the evolution of electrostatic fields in the range between 30 and 300 $\ensuremath{\mu}$$\mathrm{m}$ from the surface. We find that after the deposition of a few hundred atomic clouds, each containing $\ensuremath{\sim}$${10}^{6}$ atoms, the field of adsorbates reaches 1 V/cm for a distance of 30 $\ensuremath{\mu}$m from the surface. This evolution of the electrostatic field sets serious limitations on cavity QED experiments proposed for Rydberg atoms on atom chips.