Reservoir spectroscopy of 5s5p $^3$P$_2$ - 5s$n$d $^3$D$_{1,2,3}$ transitions in strontium

TL;DR

This paper introduces a novel reservoir-based spectroscopy method for strontium that significantly improves measurement precision of optical transitions, isotope shifts, and hyperfine structure parameters, with implications for atomic physics applications.

Contribution

The authors develop a new reservoir spectroscopy scheme that enhances precision by two orders of magnitude for strontium transitions, enabling detailed hyperfine and isotope shift measurements.

Findings

Transition frequencies measured with 2 MHz accuracy

Isotope shifts determined within 200 kHz

Hyperfine structure parameters calculated at MHz-level

Abstract

We perform spectroscopy on the optical dipole transitions 5s5p $^3$P$_2$ - 5s$n$d $^3$D$_{1,2,3}$, $n \in (5,6)$, for all stable isotopes of atomic strontium. We develop a new spectroscopy scheme, in which atoms in the metastable $^3$P$_2$ state are stored in a reservoir before being probed. The method presented here increases the attained precision and accuracy by two orders of magnitude compared to similar experiments performed in a magneto-optical trap or discharge. We show how the state distribution and velocity spread of atoms in the reservoir can be tailored to increase the spectroscopy performance. The absolute transition frequencies are measured with an accuracy of 2 MHz. The isotope shifts are given to within 200 kHz. We calculate the $A$ and $Q$ parameters for the hyperfine structure of the fermionic isotope at the MHz-level. Furthermore, we investigate the branching ratios of the $^3$D$_{J}$ states into the $^3$P$_{J}$ states and discuss immediate implications on schemes of optical pumping and fluorescence detection.