Abstract
Starting from an ultracold sample of ground-state 23Na87Rb molecules, we investigate the lowest ro-vibrational level of the b 3Π state with high resolution laser spectroscopy. This electronic spin-forbidden X 1Σ+ ↔ b 3Π transition features a nearly diagonal Franck–Condon factor and has been proposed useful for probing and manipulating the ultracold molecular gas. We measure the transition strength directly by probing the ac Stark shift induced by near resonance light and determine the total excited-state spontaneous emission rate by observing the loss of molecules. From the extracted branching ratio and the theoretical modeling, we find that the leakage to the continuum of the a 3Σ+ state plays the dominant role in the total transition linewidth. Based on these results, we show that it is feasible to create optical trapping potentials for maximizing the rotational coherence with laser light tuned close to this transition.
Highlights
In recent years, the research direction of ultracold polar molecules (UPMs) has received an increasingly intensive attention [1]
The research direction of ultracold polar molecules (UPMs) has received an increasingly intensive attention [1]. Much of this interest stems from the permanent electric dipole moment of polar molecules which, in ultracold temperatures, can be harnessed for a broad range of applications in quantum simulation and quantum information processing [2,3,4,5]
For UPMs in the electronic ground state, vibrational levels have been used to control the two-body chemical reactivity [7], rotational levels can serve as building blocks of qubits with dipolar interactions when coupled by microwave [11,12,13], while nuclear spin levels have long coherence time and are nice candidate for quantum information storage [14]
Summary
The research direction of ultracold polar molecules (UPMs) has received an increasingly intensive attention [1]. UPMs are natural candidates for investigating chemical reactions at ultralow energies where quantum mechanical effects have been observed to play a dominated role [6,7,8,9,10] Another great asset of polar molecules is their rich internal structures, including various electronic, vibrational, rotational and nuclear spin states. This electronic spin-forbidden transition is made weakly allowed by the b3Π − A1Σ+ mixing in the excited state This transition has been investigated in several bi-alkali polar molecules. This transition is the focus of the current work This rotational selection rule has been used in direct laser cooling of molecules which is critical for increasing the number of scattered photons [30]
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