Optical formation of ultracold NaK$_2$ ground state molecules

TL;DR

This study explores pathways to create ultracold NaK₂ molecules in their ground state by analyzing rovibronic transitions and potential energy surfaces, suggesting photoassociation as a feasible method.

Contribution

It provides ab initio calculations of potential energy and transition dipole surfaces for NaK₂, identifying pathways for ultracold molecule formation not previously detailed.

Findings

Double-well potential energy surfaces identified for relevant states

Transition strengths between rovibrational levels calculated

Ultracold ground-state molecules can be formed via photoassociation from excited states

Abstract

We study the rovibronic transitions in NaK$_2$ between its electronic ground state $1^2A'$ and its second excited state $3^2A'$, to identify possible pathways for the creation of ultracold ground-state triatomic molecules. Our methodology relies on the computation of potential energy surfaces and transition dipole moment surfaces for the relevant electronic states using ab initio methods. Rovibrational energy levels and wave functions are determined using the discrete variable representation approach. A double-well structure of the potential energy surface is identified for both states, and the related transition strengths between the rovibrational levels are derived. Our calculations show that the formation of ultracold ground-state NaK$_2$ molecules is expected when starting from an excited electronic state of NaK$_2$, which can be created by photoassociation of NaK and K observed by optical means by Cao et al. (Phys. Rev. Lett. 2024, 132, 093403).