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arXiv:1906.08798 · Physical Review A

Buffer-gas cooling, high-resolution spectroscopy, and optical cycling of barium monofluoride molecules

Ralf Albrecht, Michael Scharwaechter, Tobias Sixt, Lucas R. Hofer, Tim Langen

Published Jan 10, 2020• 55 citations
arXivHTMLPDF

Abstract

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.

DOI
10.1103/physreva.101.013413

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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 190m/s190\phantom{\rule{0.16em}{0ex}}\mathrm{m}/\mathrm{s}190m/s. For a well-collimated beam of 138Ba19F^{138}\mathrm{Ba}\phantom{\rule{0.16em}{0ex}}^{19}\mathrm{F}138Ba19F we observe a flux of >1010>{10}^{10}>1010 molecules sr\ensuremath−1pulse\ensuremath−1{\mathrm{sr}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{pulse}}^{\ensuremath{-}1}sr\ensuremath−1pulse\ensuremath−1 in the X2\ensuremathΣX{\phantom{\rule{0.16em}{0ex}}}^{2}\mathrm{\ensuremath{\Sigma}}X2\ensuremathΣ, N=1N=1N=1 state in our downstream detection region. Studying the absorption line strength of the intermediate A\ensuremath′\ensuremathΔ{A}^{\ensuremath{'}}\mathrm{\ensuremath{\Delta}}A\ensuremath′\ensuremathΔ state we infer a lifetime of \ensuremathτ\ensuremathΔ=790\ifmmode±\else\textpm\fi346ns{\ensuremath{\tau}}_{\mathrm{\ensuremath{\Delta}}}=790\ifmmode\pm\else\textpm\fi{}346\phantom{\rule{0.16em}{0ex}}\mathrm{ns}\ensuremathτ\ensuremathΔ​=790\ifmmode±\else\textpm\fi346ns, 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 138Ba19F^{138}\mathrm{Ba}\phantom{\rule{0.16em}{0ex}}^{19}\mathrm{F}138Ba19F that is suitable for future laser cooling of this heavy diatomic molecule.
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