EIT spectroscopy of high-lying Rydberg states in $^{39}K$

TL;DR

This study uses EIT spectroscopy to precisely measure high-lying Rydberg states in potassium-39, enabling potential applications in sensitive microwave photon detection for dark matter axion searches.

Contribution

First detailed EIT-based spectroscopy of high-lying Rydberg states in potassium-39, providing accurate energy levels for future quantum sensing applications.

Findings

Observed 80 Rydberg transitions with n~50-90

Achieved sub-GHz precision in energy level measurements

Established a foundation for Rydberg-based dark matter detection

Abstract

We present a study of the Rydberg spectrum in $^{39}K$ for $nS$ and $nD_{3/2}$ series connected to $5^2P_{1/2}$ using two-photon spectroscopy based on EIT in a heated vapor cell. We observed some 80 transitions from $5P_{1/2}$ to Rydberg states with principal quantum numbers $n\sim50-90$, and determined their transition frequencies and state energies with sub-GHz precision. Our spectroscopy results lay the groundwork for using Rydberg atoms as sensitive microwave photon detectors in searches for dark matter axions in the $\sim40-200$ $\mu$eV mass range, which is a prime range for future axion searches suggested by theory studies.