Spectroscopy of the Double Minimum $3\,^3 \Pi_{\Omega}$ Electronic State of $^{39}$K$^{85}$Rb

TL;DR

This paper reports the experimental observation and analysis of the double-minimum $3^3\Pi_{\Omega}$ electronic state of ultracold $^{39}$K$^{85}$Rb molecules, comparing experimental vibrational levels with theoretical predictions based on ab initio potentials.

Contribution

The study provides the first detailed experimental characterization of the $3^3\Pi_{\Omega}$ state in ultracold KRb, including vibrational assignments and comparison with theoretical models.

Findings

Vibrational levels $v'=2-11$ for $3^3\Pi_{1,2}$ and $v'=2-12$ for $3^3\Pi_{0^{+/-}}$ were assigned.

Experimental observations generally agree with theoretical potential predictions.

The work advances understanding of excited electronic states in ultracold diatomic molecules.

Abstract

We report the observation and analysis of the $3\,^3\Pi_{\Omega}$ double-minimum electronic excited state of $^{39}$K$^{85}$Rb. The spin-orbit components ($0^{+}, 0^{-}, 1$ and 2) of this state are investigated based on potentials developed from the available \emph{ab initio} potential curves. We have assigned the vibrational levels $v'=2-11$ of the $3\,^3\Pi_{1,2}$ potentials and $v'=2-12$ of the $3\,^3\Pi_{0^{+/-}}$ potential. We compare our experimental observations of the $3\,^3\Pi_{\Omega}$ state with predictions based on theoretical potentials. The observations are based on resonance enhanced multiphoton ionization (REMPI) of ultracold KRb in vibrational levels $v"=14-25$ of the $a\,^3\Sigma^+$ state. These \emph{a}-state ultracold molecules are formed by photoassociation of ultracold $^{39}$K and $^{85}$Rb atoms to the 5(1) state of KRb followed by spontaneous emission to the \emph{a} state.