Microwave spectroscopy of low-l singlet strontium Rydberg states at intermediate n, 50≲n≲70

Abstract

Microwave spectroscopy is used to measure the relative energy separations between strontium n1S0, n1P1, n1D2, and n1F3 Rydberg levels for 50≲n≲70 with uncertainties, limited by possible stray electric fields, of a few tens of kilohertz. These microwave results are used to develop a revised set of Rydberg-Ritz quantum defect parameters that can be used to predict level separations between the singlet S, P, D, and F states over a broad range of n with much higher precision, typically ∼20 kHz, than is possible using earlier published parameter sets. The determination of accurate transition frequencies is central to the planning of quantum simulation experiments that involve microwave-coupled Rydberg levels, such as in the creation of Rydberg-atom synthetic dimensions.