Measurement of Holmium Rydberg series through MOT depletion spectroscopy

TL;DR

This study precisely measures the Rydberg series of Holmium atoms using MOT depletion spectroscopy, providing accurate ionization potential data and revealing perturbations in the series, advancing quantum information applications.

Contribution

First detailed Rydberg spectroscopy of Holmium atoms, achieving high-precision ionization potential measurement and identifying series perturbations.

Findings

Measured 162 Rydberg levels with high accuracy.

Determined ionization potential with three orders of magnitude improvement.

Identified perturbation in the $ns$ series around n=51.

Abstract

We report measurements of the absolute excitation frequencies of $^{165}$Ho $4f^{11}6sns$ and $4f^{11}6snd$ odd-parity Rydberg series. The states are detected through depletion of a magneto-optical trap via a two-photon excitation scheme. Measurements of 162 Rydberg levels in the range $n=40-101$ yield quantum defects well described by the Rydberg-Ritz formula. We observe a strong perturbation in the $ns$ series around $n=51$ due to an unidentified interloper at 48515.47(4) cm$^{-1}$. From the series convergence, we determine the first ionization potential $E_\mathrm{IP}=48565.939(4)$ cm$^{-1}$, which is three orders of magnitude more accurate than previous work. This work represents the first time such spectroscopy has been done in Holmium and is an important step towards using Ho atoms for collective encoding of a quantum register.