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arXiv:2510.17166

Perturbation-assisted Observation of the Lowest Vibrational Level of the $\mathrm{b}^{3}Π_{0}$ State of Ultracold LiK Molecules

Anbang Yang, Xiaoyu Nie, Hao Yu, Y. Liu, Avalos, Victor, Canming He, Jacek A. Kłos, Svetlana Kotochigova, Kai Dieckmann

Published Oct 20, 2025• 0 citations
arXivHTMLPDF

Abstract

The narrow transition from the lowest rovibrational level of the $\mathrm{X}^{1}Σ^{+}$ electronic ground state to the lowest vibrational level of the $\mathrm{b}^{3}Π_{0}$ potential provides opportunities for achieving magic-wavelength trapping of ultracold bialkali molecules for enhancing their rotational coherence times. Guided by existing spectroscopic data of several perturbed and deeply-bound rovibrational states of the $\mathrm{A}^{1}Σ^{+}$ potential [Grochola et al., Chem. Phys. Lett., 2012, 535, 17-20], we conducted a targeted spectroscopic search and report the first observation of the lowest vibrational level of the $\mathrm{b}^{3}Π_{0}$ state in $^{6}\mathrm{Li}^{40}\mathrm{K}$. The transition frequency from $|\mathrm{X}^{1}Σ^{+},\,v=0,\,J=0>$ to $|\mathrm{b}^{3}Π_{0},\,v'=0,\,J'=1>$ is determined to be 314,230.5(5)GHz. Assisted by microwave spectroscopy, we resolved the rotational structure of $|\mathrm{b}^{3}Π_{0},\,v'=0>$ and extracted a rotational constant of $h\times8.576(44)$ GHz for the $\mathrm{b}^{3}Π_{0}$ state. From this, we deducted an energy separation between $|\mathrm{b}^{3}Π_{0},v'=0,J'=0>$ and $|\mathrm{X}^{1}Σ^{+},v=0,J=0>$ of $hc\times$10,481.03(2) $\mathrm{cm}^{-1}$. Our work provides timely and precise information on the deeply-bound region of the $\mathrm{b}^{3}Π_{0}$ triplet excited potential of LiK, and benefits future applications of ultracold LiK isotopologues in quantum simulation and quantum computation that demand long coherence times.

DOI
10.48550/arxiv.2510.17166

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