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Ultracold molecules have been proposed as a candidate platform for quantum science and precision measurement because of their rich internal structures and interactions. Direct laser-cooling promises to be a rapid and efficient way to bring molecules to ultracold temperatures. However, for trapped molecules, laser-cooling to the quantum motional ground state remains an outstanding challenge. A technique capable of reaching the motional ground state is Raman sideband cooling, first demonstrated in trapped ions and atoms. Here we demonstrate Raman sideband cooling of CaF molecules trapped in an optical tweezer array. Our protocol does not rely on high magnetic fields and preserves the purity of molecular internal states. We measure a high ground-state fraction and achieve low motional entropy per particle. The low temperatures we obtain could enable longer coherence times and higher-fidelity molecular qubit gates, desirable for quantum information processing and quantum simulation. With further improvements, Raman sideband cooling will also provide a route to quantum degeneracy of large molecular samples, which could be extendable to polyatomic molecular species.
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Molecular spectroscopy as a laboratory experiment: Measurement of important parameters of sodium diatomic molecules
We present an inexpensive sodium molecular spectroscopy experiment for use in an advanced undergraduate laboratory course in physics or chemistry. The molecules were excited predominantly from the ground X1Σg+(v″ = 15) state to the B1Πu(v′ = 6) state using a commercially available 532-nm broadband diode laser. The laser-induced molecular fluorescence was measured using a miniature fiber-coupled spectrometer at a resolution of 0.5 nm. The spectral peak assignments were done by comparing the observed spectrum with the calculated Franck–Condon values. Important molecular constants such as fundamental frequency, anharmonicity, bond strength, and dissociation energy of the ground electronic state were determined by using the Birge–Sponer extrapolation method. The presence of highly visible blue glowing molecules along the green laser beam creates an engaging laboratory experience. Emphasis is placed on students developing their understanding of the molecular structure, practicing molecular spectroscopic techniques, and applying knowledge of light–matter interactions to a physical system.
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- Award ID(s):
- 2309340
- PAR ID:
- 10514918
- Publisher / Repository:
- AIP Publishing
- Date Published:
- Journal Name:
- American Journal of Physics
- Volume:
- 91
- Issue:
- 12
- ISSN:
- 0002-9505
- Page Range / eLocation ID:
- 1015 to 1022
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1119/5.0123126
