Bulletin of the American Physical Society
49th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 63, Number 5
Monday–Friday, May 28–June 1 2018; Ft. Lauderdale, Florida
Session C03: Focus Session: Direct Cooling of Molecules |
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Chair: Martin Zwierlein, MIT Room: Grand B |
Tuesday, May 29, 2018 10:30AM - 11:00AM |
C03.00001: Laser Cooling and Optical Trapping of CaF Molecules Invited Speaker: Lawrence Cheuk In the past decades, advances in control of atoms have led to their use in many diverse areas, ranging from precision measurement and optical clocks to quantum information and quantum simulation of strongly correlated systems. With their rich internal structure, molecules promise to offer much more. Nevertheless, control of molecules is much more challenging precisely because of the many new internal degrees of freedom. In this talk, I will report on recent progress in direct cooling and trapping of CaF molecules. Starting from a buffer gas source, we have created cold, dense samples of CaF in a 3D magneto-optical trap. Further cooling using a gray molasses scheme brings these molecules well below the Doppler limit, allowing us to directly load molecules into an optical dipole trap - an ideal starting point for future experiments. [Preview Abstract] |
Tuesday, May 29, 2018 11:00AM - 11:30AM |
C03.00002: Experiments with ultracold CaF and YbF molecules Invited Speaker: Michael Tarbutt Ultracold molecules can be used to test fundamental physics, study collisions, simulate many-body quantum systems, and process quantum information. We produce a beam of CaF using a cryogenic buffer gas source, decelerate the beam using counter-propagating frequency-chirped laser light, then capture $2\times 10^4$ molecules in a MOT. Here, they cool to a few mK, far above the Doppler limit, due to a competition between Doppler cooling and a Sisyphus mechanism which heats the molecules in the red-detuned light of the MOT. By switching to a blue-detuned optical molasses, we cool the molecules to 50 $\mu$K, well below the Doppler limit. We optically pump these molecules into a single state and load them into a magnetic trap. We demonstrate coherent control of the rotational and hyperfine states, in free space and in the magnetic trap. We also demonstrate 1D transverse laser cooling of YbF to a temperature below 100 $\mu$K. YbF is more difficult to cool because of its higher mass and less favourable vibrational branching ratios, but is of special interest for measuring the electron EDM. We plan to study ultracold collisions between molecules and atoms, study the behaviour of small arrays of interacting molecules, and make an EDM measurement using an ultracold molecular beam. [Preview Abstract] |
Tuesday, May 29, 2018 11:30AM - 11:42AM |
C03.00003: Chemistry of Laser-Coolable Polyatomic Molecules Jacek Klos, Ming Li, Alexander Petrov, Svetlana Kotochigova Gasses of cooled molecules containing heavy atoms might have practical benefits for precision measurements and controlled chemical reactions. Cold and thus slow molecules lead to longer interrogation times, while novel quantum reaction pathways might be explored to control product molecules. Recently, J.~Doyle's group at Harvard University successfully demonstrated \footnote{I. Kozyrev et al. Phys. Rev. Lett. {\bf 118}, 173201 (2017)} laser cooling of polyatomic SrOH molecules, in which the Sr atom acts as a photon cycling site. Here, we report on a quantum mechanical study of the electronic structure of the SrOH molecule using a combination of the ab-initio coupled-cluster method with single, double, and perturbative triple excitations (CCSD(T)) and the configuration-interaction (MRCI) method. These calculations reveal the presence of multiple Conical Intersections (CIs) between potential surfaces and the richness of the SrOH electronic structure. We have located the CIs and determined their non-adiabatic couplings. [Preview Abstract] |
Tuesday, May 29, 2018 11:42AM - 11:54AM |
C03.00004: Coherent Bichromatic Force Deflection of SrOH Ivan Kozyryev, Louis Baum, Leland Aldridge, Phelan Yu, Edward Eyler, John Doyle While beam deceleration employing the spontaneous radiation pressure force has been a standard for atomic experiments, it is not as effective in slowing molecular beams. The myriad of internal molecular states inhibits photon cycling, lowering the scattering rate. An alternative approach is to employ coherent optical processes to enable rapid momentum exchange between the light field and molecules before spontaneous emission occurs. With the stimulated bichromatic force (BCF), we demonstrate deflection of polyatomic molecules using a cryogenic buffer-gas beam of the polar free radical strontium monohydroxide (SrOH) [1]. Dual-frequency high-power standing light waves are used to achieve significant force enhancement compared to radiative deflection. The coherent nature of the directional momentum transfer allows multiple $\hbar k$ of momentum change per single spontaneous emission cycle. We perform theoretical calculations of BCF in complex multilevel systems and compare to our data. Our results open the door to coherent manipulation of molecular motion, including efficient optical deceleration of diatomic and polyatomic molecules with complex level structures. [1] Kozyryev et al., arXiv:1710.08525 (2017). [Preview Abstract] |
Tuesday, May 29, 2018 11:54AM - 12:06PM |
C03.00005: Benchmarking a stimulated force for molecular beams with Rb atoms Xueping Long, Andrew Jayich, Scarlett Yu, Wesley C. Campbell The rich internal structures of molecules make ultracold molecules attractive candidates for sensitive probe of fundamental physics, but for the same reason they are hard to decelerate, cool and trap, as the many possible spontaneous emission paths limit the ability to optically decelerate molecules to trappable speed. We demonstrate a stimulated force solution to this problem using pulses generated from a mode-locked laser. A molecular beam can be first excited by a counter-propagating ``pump'' pulse, then driven back to the initial ground state by a co-propagating ``dump'' pulse via stimulated emission. The delay between the pump and dump pulse is set to be shorter than the excited state lifetimes in order to limit decays to dark states. We report results of our benchmarking this stimulated force by accelerating a cold sample of neutral Rb atoms. [Preview Abstract] |
Tuesday, May 29, 2018 12:06PM - 12:18PM |
C03.00006: Magnetically-trapped molecules efficiently loaded from a molecular MOT Matthew Steinecker, Daniel McCarron, Yuqi Zhu, David DeMille Due to the rich level structures of diatomic molecules, ultracold molecular gases will enable a wide range of experiments in ultracold chemistry, precision measurement, and quantum simulation. However, this same structure poses challenges in laser cooling and trapping of molecules [1,2]. We demonstrate the efficient transfer of molecules from a magneto-optical trap (MOT) into a conservative magnetic quadrupole trap [3]. Our scheme begins with a blue-detuned optical molasses to cool SrF molecules to $\sim 50$ $\mu$K. Next, we optically pump the molecules into a strongly-trapped sublevel. This two-step process reliably transfers 64\% of the molecules initially trapped in the MOT into the magnetic trap, comparable to similar atomic experiments. Once loaded, the magnetic trap is compressed by increasing the magnetic field gradient. We observe a magnetic trap lifetime of over 1~s. This opens a promising new path to study ultracold molecular collisions, and potentially to produce quantum-degenerate molecular gases. [1] J. F. Barry \textit{et al.}, \textit{Nature} \textbf{512}, 286--289 (2014). [2] E. B. Norrgard \textit{et al.}, \textit{Phys. Rev. Lett.} \textbf{116}, 063004 (2016). [3] D. J. McCarron \textit{et al.}, \textit{arXiv:}1712.01462. [Preview Abstract] |
Tuesday, May 29, 2018 12:18PM - 12:30PM |
C03.00007: YO laser cooling and trapping with an improved repumping scheme Yewei Wu, Alejandra Collopy, Shiqian Ding, Ian Finneran, Loic Anderegg, Benjamin Augenbraun, John Doyle, Jun Ye Using a new repumping scheme for laser cooling of yttrium II oxide (YO), we have increased the photon scattering rate by 60{\%} on the cooling transition. With this improved cycling scheme, we have improved the number of slowed molecules (with velocity \textless 10 m/s) by 20 fold from a beam of YO from a single-stage cryogenic buffer gas cell. These molecules can be readily loaded into a radio frequency (5 MHz) magneto-optical trap. We will report the characterization of the MOT. [Preview Abstract] |
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