Role of multilevel Rydberg interactions in electric-field-tuned Förster resonances

Abstract

In this work, we investigate the dc electric-field dependence of two F\"orster resonant processes in ultracold $^{85}\mathrm{Rb}$, $37{D}_{5/2}+37{D}_{5/2}\ensuremath{\rightarrow}35L(L=O,Q)+39{P}_{3/2}$, as a function of the atomic density. At low densities, the $39{P}_{3/2}$ yield as a function of electric field exhibits resonances. With increasing density, the linewidths increase until the peaks merge. Even under these extreme conditions, where the F\"orster resonance processes show little electric-field dependence, the $39{P}_{3/2}$ population depends quadratically on the total Rydberg atom population, suggesting that a two-body interaction is the dominant process. In order to explain our results, we implement a theoretical model which takes into account the multilevel character of the interactions and Rydberg atom blockade process using only atom pair interactions. The comparison between the experimental data and the model is very good, suggesting that the F\"orster resonant processes are dominated by two-body interactions up to atomic densities of $3.0\ifmmode\times\else\texttimes\fi{}{10}^{12}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$.