Saturated absorption spectroscopy of buffer-gas-cooled Barium monofluoride molecules

Abstract

We report an experimental investigation on the Doppler-free saturated absorption spectroscopy of buffer-gas-cooled Barium monofluoride (BaF) molecules in a 4 K cryogenic cell. The obtained spectra with a resolution of 19 MHz, much smaller than previously observed in absorption spectroscopy, clearly resolve the hyperfine transitions. Moreover, we use these high-resolution spectra to fit the hyperfine splittings of excited A(v = 0) state and find the hyperfine splitting of the laser-cooling-relevant A²Π_1/2(v = 0, J = 1/2,+) state is about 18 MHz, much higher than the previous theoretically predicted value. This provides important missing information for laser cooling of BaF molecules.

Graphical abstract

Keywords

cold molecule / saturated spectroscopy / buffer gas cooling / BaF

References

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Acknowledgements

We thank Prof. Eric Hessels for useful discussions, and acknowledge the support from the National Key Research and Development Program of China under Grant No. 2018YFA0307200, the National Natural Science Foundation of China under Grant Nos. U21A20437 and 12074337, the Natural Science Foundation of Zhejiang Province under Grant No. LR21A040002, Zhejiang Province Plan for Science and technology No. 2020C01019, and the Fundamental Research Funds for the Central Universities under No.2021FZZX001-02.

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