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arXiv:1811.10404 · Physical Review A

Type-II Zeeman slowing: Characterization and comparison to conventional radiative beam-slowing schemes

M. Petzold, P. Kaebert, Philipp Gersema, T. Poll, N. Reinhardt, M. Siercke, Silke Ospelkaus

Published Dec 7, 2018• 8 citations
arXivHTMLPDF

Abstract

We describe a Zeeman slowing method reported in [New J. Phys. 20, 042001 (2018)] and compare it to conventional radiative beam-slowing schemes. The scheme is designed to work on a type-II level structure, making it particularly attractive for radiative beam slowing of molecules. Working on the ${D}_{1}$ line of atomic $^{39}\mathrm{K}$, we demonstrate efficient slowing of an atomic beam from $400\phantom{\rule{4pt}{0ex}}\mathrm{m}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$ down to $35\phantom{\rule{4pt}{0ex}}\mathrm{m}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$ with a final flux of $3.3\ifmmode\times\else\texttimes\fi{}{10}^{9}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. We give experimental details and compare our results to other established radiative slowing schemes in atomic and molecular physics. We find type-II Zeeman slowing to outperform white-light slowing commonly used in molecular beam slowing and to be comparably as efficient as traditional type-I Zeeman slowing being the standard beam-slowing technique in atomic physics.

DOI
10.1103/physreva.98.063408

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Abstract The Fast Track Communication by Petzold et al (2018 New J. Phys. 20 042001) demonstrates the first Zeeman slowing scheme for species with type-II optical cycling transitions. This new approach is directly applicable to those 2 Σ molecules that have recently been captured and cooled in molecular magneto-optical traps (MOTs) and has the potential to efficiently and continuously load these traps for the first time. This advance could produce molecular MOTs with populations comparable to their atomic counterparts and realize an ideal platform for a wide range of studies using large, dense samples of ultracold molecules.

New Journal of Physics•May 1, 2018•2 citations
We describe a Zeeman slowing method reported in [New J. Phys. 20, 042001 (2018)] and compare it to conventional radiative beam-slowing schemes. The scheme is designed to work on a type-II level structure, making it particularly attractive for radiative beam slowing of molecules. Working on the D1{D}_{1}D1​ line of atomic 39K^{39}\mathrm{K}39K, we demonstrate efficient slowing of an atomic beam from 400ms\ensuremath−1400\phantom{\rule{4pt}{0ex}}\mathrm{m}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}400ms\ensuremath−1 down to 35ms\ensuremath−135\phantom{\rule{4pt}{0ex}}\mathrm{m}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}35ms\ensuremath−1 with a final flux of 3.3\ifmmode×\else\texttimes\fi109cm\ensuremath−2s\ensuremath−13.3\ifmmode\times\else\texttimes\fi{}{10}^{9}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}3.3\ifmmode×\else\texttimes\fi109cm\ensuremath−2s\ensuremath−1. We give experimental details and compare our results to other established radiative slowing schemes in atomic and molecular physics. We find type-II Zeeman slowing to outperform white-light slowing commonly used in molecular beam slowing and to be comparably as efficient as traditional type-I Zeeman slowing being the standard beam-slowing technique in atomic physics.
We present a novel slowing scheme for beams of laser-coolable diatomic molecules reminiscent of Zeeman slowing of atomic beams. The scheme results in efficient compression of the one-dimensional velocity distribution to velocities trappable by magnetic or magneto-optical traps. We experimentally demonstrate our method in an atomic testbed and show an enhancement of flux below v = 35 m s-1 by a factor of ≈20 compared to white light slowing. 3D Monte Carlo simulations performed to model the experiment show excellent agreement. We apply the same simulations to the prototype molecule 88Sr19F and expect 15% of the initial flux to be continuously compressed in a narrow velocity window at around 10 m s-1. This is the first experimentally shown continuous and dissipative slowing technique in molecule-like level structures, promising to provide the missing link for the preparation of large ultracold molecular ensembles. © 2018 The Author(s). Published by IOP Publishing Ltd on behalf of Deutsche Physikalische Gesellschaft.
We present a novel slowing scheme for beams of laser-coolable diatomic molecules reminiscent of Zeeman slowing of atomic beams. The scheme results in efficient compression of the one-dimensional velocity distribution to velocities trappable by magnetic or magneto-optical traps. We experimentally demonstrate our method in an atomic testbed and show an enhancement of flux below v = 35 m s −1 by a factor of ≈20 compared to white light slowing. 3D Monte Carlo simulations performed to model the experiment show excellent agreement. We apply the same simulations to the prototype molecule 88 Sr 19 F and expect 15% of the initial flux to be continuously compressed in a narrow velocity window at around 10 m s −1 . This is the first experimentally shown continuous and dissipative slowing technique in molecule-like level structures, promising to provide the missing link for the preparation of large ultracold molecular ensembles.
Cold molecules are an invaluable tool for modern physics. Cold atoms have already revolutionized precision metrology, allowed for spectacular findings in quantum physics and opened the door for the creation and observation of novel states of matter. Cold molecules bring with them additional degrees of freedom which give rise to unique properties that enable new kinds of experiments. For these experiments it is of vital importance to start with a sufficiently large number of cold molecules. There are multiple paths for the slowing and cooling of atoms and most of the slowing techniques utilizing lasers for direct cooling have been transferred to the molecular case with its specific requirements. The Zeeman slowing technique is advantageous for loading a trap with cold particles but had not yet been transferred from atoms to the molecular case. In this thesis I will show the first realization of the Zeeman slowing technique for diatomic molecules. This thesis will discuss several preparatory steps: Our group has had some ideas to collimate the molecular beam with a conical nozzle outlet at the buffer gas cell which I investigated on potassium atoms generated by the ablation of 39K35Cl inside the buffer gas cell. I also realized a fluorescence spectroscopy of the |XΣ1/2, N = 1, v = 0⟩ → |AΠ1/2, N = 0, v = 0⟩ transition in magnetic fields up to 300 G and confirmed simulations regarding our two laser cycling scheme in the Paschen-Back regime by measuring the scattering rate of light on one molecule. Finally, I created pre-cooled 40Ca19F with a forward velocity of around 150 m s−1 from a 40Ca19F2 target with laser ablation inside a cryogenic buffer gas cell. With the Zeeman slowing technique I slowed the molecules down to 25 m s−1, a velocity where trapping can be possible. I have also shown the characteristic compression into specific velocity classes for not yet trappable velocities. Together these two findings demonstrate that molecular Zeeman slowing is possible and a real promising tool for future experiments.
We use a multistage Zeeman decelerator to generate slow beams ($v\ensuremath{\simeq}100\phantom{\rule{0.16em}{0ex}}\mathrm{m}/\mathrm{s}$) of translationally cold, spin-polarized metastable $a\phantom{\rule{0.16em}{0ex}}^{3}\mathrm{\ensuremath{\Sigma}}_{u}^{+}\phantom{\rule{4pt}{0ex}}{\mathrm{He}}_{2}$ molecules and perform a precision measurement of their spin-rotation fine structure. The spin polarization results from the elimination of the high-field-seeking J=NJ=NJ=N spin-rotational component of each rotational level (rotational quantum number NNN) by the Zeeman deceleration process. By repopulating the J=NJ=NJ=N component from the $J=N\ifmmode\pm\else\textpm\fi{}1$ low-field-seeking components using radio-frequency radiation, we measured the spin-rotation fine structure of 13 rovibrational levels with v=0v=0v=0, 1 and N=1–21N=1\text{--}21N=1–21. The low beam velocity and the resulting long interaction times with the radio-frequency radiation were exploited to determine the transition frequencies with a precision of 300 Hz.
We propose a general Zeeman slower scheme applicable to the majority of the laser-coolable molecules. Different from previous schemes, we apply a careful modulation on the repump laser and guarantee the velocity selectivity through the polarization selection rules. Only atoms or molecules with the right velocity will be laser slowed. Such a scheme is more feasible for molecules with complex energy structures. We apply this scheme for molecules with a large Land\'e ggg factor of the excited states, i.e., ge>0.1{g}_{e}>0.1ge​>0.1, and polyatomic molecules with one-dimensional numerical simulations. The results show a better slowing efficiency with about 62% of the BaF molecules and 99% of the SrOH molecules being successfully slowed down to a velocity below 15m/s15\phantom{\rule{0.28em}{0ex}}\mathrm{m}/\mathrm{s}15m/s without the consideration of transverse divergence.
Abstract The Fast Track Communication by Petzold et al (2018 New J. Phys. 20 042001) demonstrates the first Zeeman slowing scheme for species with type-II optical cycling transitions. This new approach is directly applicable to those 2 Σ molecules that have recently been captured and cooled in molecular magneto-optical traps (MOTs) and has the potential to efficiently and continuously load these traps for the first time. This advance could produce molecular MOTs with populations comparable to their atomic counterparts and realize an ideal platform for a wide range of studies using large, dense samples of ultracold molecules.