# Electrically tuned F\"orster resonances in collisions of NH$_3$ with Rydberg He atoms

## TL;DR

This study demonstrates how weak electric fields can precisely tune F"orster resonances in NH$_3$-Rydberg He atom collisions, enabling controlled energy transfer with experimental results aligning well with theoretical calculations.

## Contribution

It provides the first detailed experimental and theoretical investigation of electric-field-controlled F"orster resonances in NH$_3$ and Rydberg He atom collisions for high principal quantum numbers.

## Key findings

- Electric fields can tune F"orster resonances in NH$_3$-Rydberg He collisions.
- Experimental data agrees with dipole-dipole interaction calculations.
- Resonant energy transfer is controllable via electric field adjustments.

## Abstract

Effects of weak electric fields on resonant energy transfer between NH$_3$ in the X $^1$A$_1$ ground electronic state, and Rydberg He atoms in triplet states with principal quantum numbers $n = 36$-$41$ have been studied in a crossed beam apparatus. For these values of $n$, electric-dipole transitions between the Rydberg states that evolve adiabatically to the $|ns\rangle$ and $|np\rangle$ states in zero electric field can be tuned into resonance with the ground-state inversion transitions in NH$_3$ using electric fields, with energy transfer occurring via F\"orster resonance. In the experiments the Rydberg He atoms, traveling in pulsed supersonic beams, were prepared by resonant two-photon excitation from the metastable $1s2s\,^3S_1$ level and crossed an effusive beam of NH$_3$ before being detected by state-selective pulsed-electric-field ionization. The resonant-energy-transfer process was identified by monitoring changes in the ionization signal from the $|ns\rangle$ and $|np\rangle$ Rydberg states for each value of $n$. The electric field dependence of the experimental data is in good agreement with the results of calculations in which the resonant dipole-dipole coupling between the collision partners was accounted for.