Rydberg-Stark states in oscillating electric fields

TL;DR

This study investigates how weak radio-frequency electric fields influence Rydberg-Stark states with large electric dipole moments, combining high-resolution spectroscopy and Floquet calculations to understand energy level shifts and couplings.

Contribution

It provides experimental data and theoretical validation for Floquet methods in modeling Rydberg-Stark states under oscillating electric fields, especially in weak field regimes.

Findings

Spectra agree with Floquet calculations in weak fields

Floquet methods accurately predict Stark energy levels in low fields

Limitations of calculations identified in stronger fields due to n-mixing

Abstract

Experimental and theoretical studies of the effects of weak radio-frequency electric fields on Rydberg-Stark states with electric dipole moments as large as 10000 D are reported. High-resolution laser spectroscopic studies of Rydberg states with principal quantum number $n=52$ and $53$ were performed in pulsed supersonic beams of metastable helium with the excited atoms detected by pulsed electric field ionisation. Experiments were carried out in the presence of sinusoidally oscillating electric fields with frequencies of 20~MHz, amplitudes of up to 120~mV/cm, and dc offsets of up to 4.4~V/cm. In weak fields the experimentally recorded spectra are in excellent agreement with the results of calculations carried out using Floquet methods to account for electric dipole couplings in the oscillating fields. This highlights the validity of these techniques for the accurate calculation of the Stark energy level structure in such fields, and the limitations of the calculations in stronger fields where $n-$mixing and higher-order contributions become important.