Heteronuclear long-range Rydberg molecules

TL;DR

This paper reports the experimental creation and spectroscopic analysis of heteronuclear long-range Rydberg molecules involving cesium and potassium, highlighting discrepancies with current theoretical models and providing benchmarks for future improvements.

Contribution

It presents the first formation and detailed spectroscopy of heteronuclear long-range Rydberg molecules, revealing limitations in existing theoretical models.

Findings

Successful formation of heteronuclear CsK Rydberg molecules

Discrepancies between experimental data and theoretical predictions

Spectroscopic access to previously unobservable molecular states

Abstract

We present the formation of homonuclear Cs2, K2, and heteronuclear CsK long-range Rydberg molecules in a dual-species magneto-optical trap for 39K and 133Cs by one-photon UV photoassociation. The different ground-state-density dependence of homo- and heteronuclear photoassociation rates and the detection of stable molecular ions resulting from auto-ionization provide an unambiguous assignment. We perform bound-bound millimeter-wave spectroscopy of long-range Rydberg molecules to access molecular states not accessible by one-photon photoassociation. Calculations based on the most recent theoretical model and atomic parameters do not reproduce the full set of data from homo- and heteronuclear long-range Rydberg molecules consistently. This shows that photoassociation and millimeter-wave spectroscopy of heteronuclear long-range Rydberg molecules provide a benchmark for the development of theoretical models.