Measurement of the strontium triplet Rydberg series by depletion spectroscopy of ultracold atoms

TL;DR

This paper precisely measures the energies of strontium Rydberg states using depletion spectroscopy in ultracold atoms, significantly improving accuracy and providing detailed quantum defect data and ionization limit.

Contribution

It presents high-precision measurements of strontium Rydberg series energies, extending previous data by over two orders of magnitude and analyzing perturbations and quantum defects.

Findings

Accurate energy levels for $^{88}$Sr Rydberg series from n=13 to 50.

Determined quantum defects and ionization limit with high precision.

Improved accuracy by over two orders of magnitude compared to previous data.

Abstract

We report on the atom loss spectroscopy of strontium Rydberg atoms in a magneto-optical trap, using a two-photon excitation scheme through the intermediate state $5\mathrm{s}5\mathrm{p} \, ^3\mathrm{P}_1$. Energies of the $5\mathrm{s}n\mathrm{s} \, ^3\mathrm{S}_1$ and $5\mathrm{s}n\mathrm{d} \, ^3\mathrm{D}_{1,2}$ Rydberg series of $^{88}$Sr in the range $13 \leq n \leq 50$ are determined with an absolute accuracy of 10 MHz, including the perturbed region where the $5\mathrm{s}n\mathrm{d} \, ^3\mathrm{D}_{2}$ series couples to the $5\mathrm{s}n\mathrm{d} \, ^1\mathrm{D}_{2}$ series. This represents an improvement by more than two orders of magnitude compared to previously published data. The quantum defects for each series are determined using the extended Rydberg-Ritz formula in the range where there is no strong perturbation. A value of $1\,377\,012\,721(10) \,\mathrm{MHz}$ for the first ionization limit of $^{88}$Sr is extracted.