arXiv:2201.04750 · Physical Review A

Doppler cooling of buffer-gas-cooled barium monofluoride molecules

Yuhe Zhang, Zixuan Zeng, Qian Liang, Wenhao Bu, Bo Yan

Published Mar 14, 2022• 28 citations

Abstract

We demonstrate one-dimensional Doppler cooling of a beam of buffer-gas-cooled barium monofluoride (BaF) molecules. This represents a key step towards further cooling and trapping of BaF molecules. The dependencies of the cooling efficiency on the detuning of laser, the intensity of the laser, and the bias field are systematically studied. Furthermore, the numerical simulations with a Monte Carlo method agree quite well with our data.

DOI: 10.1103/physreva.105.033307

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arXiv:2201.04750 · Physical Review A

Doppler cooling of buffer-gas-cooled barium monofluoride molecules

Yuhe Zhang, Zixuan Zeng, Qian Liang, Wenhao Bu, Bo Yan

Published Mar 14, 2022• 28 citations

arXiv HTML PDF

Abstract

DOI: 10.1103/physreva.105.033307

Related papers

Cold collision and high-resolution spectroscopy of buffer-gas-cooled BaF molecules

Wenhao Bu, Tao Chen, Guitao Lv +1 more

We reported a detailed experimental study of the cold collision of barium monofluoride (BaF) with buffer gas and the high-resolution spectroscopy relevant with direct laser cooling. BaF molecules are efficiently produced with laser ablation and buffer-gas cooled in a cryogenic apparatus. The laser cooling relevant transition $|X\phantom{\rule{0.16em}{0ex}}^{2}\mathrm{\ensuremath{\Sigma}},v=0,N=1\ensuremath{\rangle}$ to $|A\phantom{\rule{0.16em}{0ex}}^{2}\mathrm{\ensuremath{\Pi}},{v}^{\ensuremath{'}}=0,{J}^{\ensuremath{'}}=1/2\ensuremath{\rangle}$ is identified. The collision cross section with buffer gas is measured to be $1.4(7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}\phantom{\rule{4.pt}{0ex}}{\text{cm}}^{\ensuremath{-}2}$, which is very suitable for buffer-gas cooling. Both rotational and vibrational temperatures are effectively cooled, and a large amount of molecules are quenched into the desired states. Our study provides an important benchmark for further laser cooling of the BaF molecule.We reported a detailed experimental study of the cold collision of barium monofluoride (BaF) with buffer gas and the high-resolution spectroscopy relevant with direct laser cooling. BaF molecules are efficiently produced with laser ablation and buffer-gas cooled in a cryogenic apparatus. The laser cooling relevant transition $|X\phantom{\rule{0.16em}{0ex}}^{2}\mathrm{\ensuremath{\Sigma}},v=0,N=1\ensuremath{\rangle}$ to $|A\phantom{\rule{0.16em}{0ex}}^{2}\mathrm{\ensuremath{\Pi}},{v}^{\ensuremath{'}}=0,{J}^{\ensuremath{'}}=1/2\ensuremath{\rangle}$ is identified. The collision cross section with buffer gas is measured to be $1.4(7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}\phantom{\rule{4.pt}{0ex}}{\text{cm}}^{\ensuremath{-}2}$, which is very suitable for buffer-gas cooling. Both rotational and vibrational temperatures are effectively cooled, and a large amount of molecules are quenched into the desired states. Our study provides an important benchmark for further laser cooling of the BaF molecule.

arXiv:1612.07449Physical Review AMar 15, 201738 citations

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

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We demonstrate buffer-gas cooling, high-resolution spectroscopy, and cycling fluorescence of cold barium monofluoride (BaF) molecules. Our source produces an intense and internally cold molecular beam containing the different BaF isotopologues with a mean forward velocity of $190\phantom{\rule{0.16em}{0ex}}\mathrm{m}/\mathrm{s}$ . For a well-collimated beam of $^{138}\mathrm{Ba}\phantom{\rule{0.16em}{0ex}}^{19}\mathrm{F}$ we observe a flux of $>{10}^{10}$ molecules ${\mathrm{sr}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{pulse}}^{\ensuremath{-}1}$ in the $X{\phantom{\rule{0.16em}{0ex}}}^{2}\mathrm{\ensuremath{\Sigma}}$, $N=1$ state in our downstream detection region. Studying the absorption line strength of the intermediate ${A}^{\ensuremath{'}}\mathrm{\ensuremath{\Delta}}$ state we infer a lifetime of ${\ensuremath{\tau}}_{\mathrm{\ensuremath{\Delta}}}=790\ifmmode\pm\else\textpm\fi{}346\phantom{\rule{0.16em}{0ex}}\mathrm{ns}$, significantly longer than previously estimated. Finally, highly diagonal Franck-Condon factors and magnetic remixing of dark states allow us to realize a quasicycling transition in $^{138}\mathrm{Ba}\phantom{\rule{0.16em}{0ex}}^{19}\mathrm{F}$ that is suitable for future laser cooling of this heavy diatomic molecule.We demonstrate buffer-gas cooling, high-resolution spectroscopy, and cycling fluorescence of cold barium monofluoride (BaF) molecules. Our source produces an intense and internally cold molecular beam containing the different BaF isotopologues with a mean forward velocity of $190\phantom{\rule{0.16em}{0ex}}\mathrm{m}/\mathrm{s}$. For a well-collimated beam of $^{138}\mathrm{Ba}\phantom{\rule{0.16em}{0ex}}^{19}\mathrm{F}$ we observe a flux of $>{10}^{10}$ molecules ${\mathrm{sr}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{pulse}}^{\ensuremath{-}1}$ in the $X{\phantom{\rule{0.16em}{0ex}}}^{2}\mathrm{\ensuremath{\Sigma}}$, $N=1$ state in our downstream detection region. Studying the absorption line strength of the intermediate ${A}^{\ensuremath{'}}\mathrm{\ensuremath{\Delta}}$ state we infer a lifetime of ${\ensuremath{\tau}}_{\mathrm{\ensuremath{\Delta}}}=790\ifmmode\pm\else\textpm\fi{}346\phantom{\rule{0.16em}{0ex}}\mathrm{ns}$, significantly longer than previously estimated. Finally, highly diagonal Franck-Condon factors and magnetic remixing of dark states allow us to realize a quasicycling transition in $^{138}\mathrm{Ba}\phantom{\rule{0.16em}{0ex}}^{19}\mathrm{F}$ that is suitable for future laser cooling of this heavy diatomic molecule.

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A. Marsman, Marko Horbatsch, Eric A. Hessels

A full density-matrix simulation is performed for optical deflection of a barium monofluoride ( $^{138}\mathrm{Ba}^{19}\mathrm{F}$ ) beam using the bichromatic force, which employs pairs of counterpropagating laser beams that are offset in frequency. We show that the force is sufficient to separate BaF molecules from the other products generated in a helium-buffer-gas-cooled ablation source. For our simulations, the density-matrix and force equations are numerically integrated during the entire time that the molecules pass through a laser beam to ensure that effects of the evolution of the Doppler shift and of the optical intensity and phase at the position of the molecule are properly included. The results of this paper are compared to those of a deflection scheme [A. Marsman, D. Heinrich, M. Horbatsch, and E. A. Hessels, Phys. Rev. A 107, 032811 (2023)] which uses $\ensuremath{\pi}$ pulses to drive frequency-resolved transitions. This paper is part of an effort by the ${\mathrm{EDM}}^{3}$ collaboration to measure the electric dipole moment of the electron using BaF molecules embedded in a cryogenic argon solid. Separation of BaF molecules will aid in producing a sufficiently pure solid.A full density-matrix simulation is performed for optical deflection of a barium monofluoride ($^{138}\mathrm{Ba}^{19}\mathrm{F}$) beam using the bichromatic force, which employs pairs of counterpropagating laser beams that are offset in frequency. We show that the force is sufficient to separate BaF molecules from the other products generated in a helium-buffer-gas-cooled ablation source. For our simulations, the density-matrix and force equations are numerically integrated during the entire time that the molecules pass through a laser beam to ensure that effects of the evolution of the Doppler shift and of the optical intensity and phase at the position of the molecule are properly included. The results of this paper are compared to those of a deflection scheme [A. Marsman, D. Heinrich, M. Horbatsch, and E. A. Hessels, Phys. Rev. A 107, 032811 (2023)] which uses $\ensuremath{\pi}$ pulses to drive frequency-resolved transitions. This paper is part of an effort by the ${\mathrm{EDM}}^{3}$ collaboration to measure the electric dipole moment of the electron using BaF molecules embedded in a cryogenic argon solid. Separation of BaF molecules will aid in producing a sufficiently pure solid.

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2D transverse laser cooling of a hexapole focused beam of cold BaF molecules

Joost W. F. van Hofslot, I. E. Thompson, Anno Touwen +21 more

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arXiv:2506.19069Communications PhysicsJan 12, 20263 citations

Laser cooling of barium monofluoride molecules using synthesized optical spectra

Marian Rockenhäuser, Felix Kogel, Tatsam Garg +2 more

We demonstrate laser cooling of barium monofluoride ( BaF 138 ) molecules. We use serrodynes to synthesize time-sequenced optical spectra that can be precisely tailored to the hyperfine structure of this heaviest nonradioactive alkaline earth monofluoride. By optimizing these optical spectra, we realize strong Sisyphus cooling forces that efficiently collimate a molecular beam. Our technique is an important step toward using intense beams of barium monofluoride for precision measurement applications, and will be useful for cooling other molecular species with complex level structure. Published by the American Physical Society 2024We demonstrate laser cooling of barium monofluoride ( BaF 138 ) molecules. We use serrodynes to synthesize time-sequenced optical spectra that can be precisely tailored to the hyperfine structure of this heaviest nonradioactive alkaline earth monofluoride. By optimizing these optical spectra, we realize strong Sisyphus cooling forces that efficiently collimate a molecular beam. Our technique is an important step toward using intense beams of barium monofluoride for precision measurement applications, and will be useful for cooling other molecular species with complex level structure. Published by the American Physical Society 2024

arXiv:2405.09427Physical Review ResearchNov 18, 202413 citations

190\phantom{\rule{0.16em}{0ex}}\mathrm{m}/\mathrm{s}

. For a well-collimated beam of

^{138}\mathrm{Ba}\phantom{\rule{0.16em}{0ex}}^{19}\mathrm{F}

we observe a flux of

>{10}^{10}

molecules ${\mathrm{sr}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{pulse}}^{\ensuremath{-}1}$ in the $X{\phantom{\rule{0.16em}{0ex}}}^{2}\mathrm{\ensuremath{\Sigma}}$,

N=1

state in our downstream detection region. Studying the absorption line strength of the intermediate ${A}^{\ensuremath{'}}\mathrm{\ensuremath{\Delta}}$ state we infer a lifetime of ${\ensuremath{\tau}}_{\mathrm{\ensuremath{\Delta}}}=790\ifmmode\pm\else\textpm\fi{}346\phantom{\rule{0.16em}{0ex}}\mathrm{ns}$, significantly longer than previously estimated. Finally, highly diagonal Franck-Condon factors and magnetic remixing of dark states allow us to realize a quasicycling transition in

^{138}\mathrm{Ba}\phantom{\rule{0.16em}{0ex}}^{19}\mathrm{F}

that is suitable for future laser cooling of this heavy diatomic molecule.

A full density-matrix simulation is performed for optical deflection of a barium monofluoride (

^{138}\mathrm{Ba}^{19}\mathrm{F}

) beam using the bichromatic force, which employs pairs of counterpropagating laser beams that are offset in frequency. We show that the force is sufficient to separate BaF molecules from the other products generated in a helium-buffer-gas-cooled ablation source. For our simulations, the density-matrix and force equations are numerically integrated during the entire time that the molecules pass through a laser beam to ensure that effects of the evolution of the Doppler shift and of the optical intensity and phase at the position of the molecule are properly included. The results of this paper are compared to those of a deflection scheme [A. Marsman, D. Heinrich, M. Horbatsch, and E. A. Hessels, Phys. Rev. A 107, 032811 (2023)] which uses $\ensuremath{\pi}$ pulses to drive frequency-resolved transitions. This paper is part of an effort by the

{\mathrm{EDM}}^{3}

collaboration to measure the electric dipole moment of the electron using BaF molecules embedded in a cryogenic argon solid. Separation of BaF molecules will aid in producing a sufficiently pure solid.