Measurement of the hyperfine coupling constant for $nS_{1/2}$ Rydberg states of $^{85}$Rb

TL;DR

This paper reports precise measurements of hyperfine splittings in $^{85}$Rb Rydberg states, significantly improving the accuracy of the hyperfine coupling constant and exploring systematic uncertainties and Rydberg pair interactions.

Contribution

The study provides the most accurate measurement to date of the hyperfine coupling constant for $^{85}$Rb Rydberg states and investigates systematic effects and pair state interactions.

Findings

Hyperfine coupling constant $A_{HFS}$ = 15.372(80) GHz.

Systematic uncertainties from electric/magnetic fields and interactions are well-characterized.

Initial evidence for hyperfine-mixed Rydberg pair states.

Abstract

We present measurements of the hyperfine structure splittings of $nS_{1/2}$ Rydberg states of $^{85}$Rb for $n$= 43, 44, 45 and 46. From the splittings, the hyperfine coupling constant, $A_{\mathrm{HFS}}$, is determined to be 15.372(80) GHz. This result is an order-of-magnitude improvement from previous measurements. We study and account for systematic uncertainty sources, such as unwanted electric and magnetic fields, dipolar Rydberg-Rydberg interactions, and AC shifts. Initial evidence for hyperfine-mixed Rydberg pair states is found.