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arXiv · 2510.24660

Hyperfine-resolved optical spectroscopy of ultracold $^{87}$Rb$^{133}$Cs molecules: the $\mathrm{b}\,^3Π_0$ metastable state

Arpita Das·Albert Li Tao·Luke M. Fernley·Fritz von Gierke·Philip D. Gregory·Simon L. Cornish·Jeremy M. Hutson·Romain Vexiau·Olivier Dulieu
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Abstract

Using an ultracold gas of $^{87}$Rb$^{133}$Cs molecules, we perform hyperfine-resolved spectroscopy of transitions from the vibronic ground state to the lowest rovibrational states of the electronic state $\mathrm{b}\,^3Π_0$, as a function of magnetic field. These transitions are spin forbidden, resulting in narrow linewidths, and feature near-diagonal Franck-Condon factors. We develop a model of the hyperfine and Zeeman structure that includes coupling between the $0^+$ and $0^-$ components of $\mathrm{b}\,^3Π_0$. We fit the spectra to obtain rotational and hyperfine coupling constants. We measure transition dipole moments associated with specific transitions by directly observing Rabi oscillations as a function of a resonant laser pulse duration. Using resonant $π$ pulses, we prepare molecules in the electronically excited state and directly measure the spontaneous emission rate.

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Arpita Das, Albert Li Tao, Luke M. Fernley, Fritz von Gierke, Philip D. Gregory, Simon L. Cornish, Jeremy M. Hutson, Romain Vexiau, Olivier Dulieu. 2026-02-06. Hyperfine-resolved optical spectroscopy of ultracold $^{87}$Rb$^{133}$Cs molecules: the $\mathrm{b}\,^3Π_0$ metastable state. https://arxiv.org/abs/2510.24660

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