Probing van der Waals interactions and detecting polar molecules by Förster resonance energy transfer with Rydberg atoms at temperatures below 100 mK

Abstract

Electric-field-controlled Förster resonance energy transfer (FRET) between Rydberg helium (He) atoms and ground-state ammonia (NH${}_3$) molecules has been studied at translational temperatures below 100 mK. The experiments were performed in an intrabeam collision apparatus with pulsed supersonic beams of NH${}_3$ seeded in He. A range of Förster resonances, between triplet Rydberg states in He with principal quantum numbers of 38, 39 and 40, and the inversion intervals in NH${}_3$ were investigated. Resonance widths as low as $100\pm 20$ MHz were observed for Rydberg-Rydberg transitions with electric dipole transition moments of 3270 D. These widths result from binary collisions at a mean center-of-mass speed of $19.3\pm 2.6$ m/s. For transitions in which the initially prepared Rydberg states were strongly polarized, with large induced static electric dipole moments, van der Waals interactions between the collision partners increased the resonance widths to $\sim 750$ MHz. From measurements of the rate of FRET for the narrowest resonances observed, a density of NH${}_3$ of $(9.4\pm 0.3)\times 10^9$ cm${}^{-3}$ in the upper ground-state inversion sublevel in the interaction region of the apparatus was determined non-destructively.

6 pages, 4 figures

References in corpus (4)

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• Rydberg-State-Resolved Resonant Energy Transfer in Cold Electric-Field-Controlled Intrabeam Collisions of NH${}_3$ with Rydberg He Atoms
• Probing resonant energy transfer in collisions of ammonia with Rydberg helium atoms by microwave spectroscopy
• Mean-field energy-level shifts and dielectric properties of strongly polarized Rydberg gases