Bulletin of the American Physical Society
50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 64, Number 4
Monday–Friday, May 27–31, 2019; Milwaukee, Wisconsin
Session V05: Direct Cooling of Molecules |
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Chair: John Doyle, Harvard University Room: Wisconsin Center 102C |
Friday, May 31, 2019 8:00AM - 8:12AM |
V05.00001: Deep Cooling of SrF Molecules Thomas Langin, Matthew Steinecker, Yuqi Zhu, Varun Jorapur, David DeMille A Bose-Einstein condensate (BEC) of polar molecules would allow for the creation of strongly correlated quantum states, such as dipolar crystals, which are not well understood and have not yet been studied in the lab. To create a BEC, molecular gases must be cooled further than has previously been achieved. We are currently pursuing two techniques for deeper cooling of SrF. First, we report on our progress in implementing gray-molasses cooling schemes, which simulations indicate should cool SrF to $\sim$1$\mu$K. We also report on progress towards co-trapping of SrF and Rb for the purpose of sympathetically cooling SrF using evaporatively-cooled Rb as a refrigerant. For this to be effective, elastic collisions must dominate over inelastic ones. Whether this is the case for SrF-Rb is currently unknown; sympathetic cooling will provide an opportunity to study atom-molecule collisions in a largely unexplored temperature regime. In addition, methods for both enhancing the elastic rate and suppressing the inelastic rate of molecule-molecule collisions in the quantum regime have been proposed in recent years, and we plan to test these ideas upon reaching sub $\mu$K temperatures. [Preview Abstract] |
Friday, May 31, 2019 8:12AM - 8:24AM |
V05.00002: Towards a narrow-line MOT of YO Yewei Wu, Shiqian Ding, Ian Finneran, Alejandra Collopy, Jun Ye We report a magneto-optical trap (MOT) of Yttrium monoxide (YO) molecules and our recent progress towards a second-stage narrow-line MOT. YO molecules are produced from a cryogenic buffer gas cell, slowed by a counter-propagating laser beam and then loaded into the RF MOT. Currently, the MOT holds \textasciitilde 1.5x10$^{\mathrm{4}}$ molecules at a temperature of 4.1(5) mK. Recently we performed high resolution spectroscopy for the narrow transition (\textasciitilde 6 kHz) in YO suitable for further cooling to the microkelvin regime. At these temperatures, molecules will be ready to be loaded into magnetic or optical dipole traps for studies of ultracold chemistry and quantum many-body physics. [Preview Abstract] |
Friday, May 31, 2019 8:24AM - 8:36AM |
V05.00003: Deep laser cooling and efficient magnetic compression of molecules L. Caldwell, J.A. Devlin, H.J. Williams, N.J. Fitch, E.A. Hinds, B.E. Sauer, M.R. Tarbutt We report on our efforts to lower the temperature of laser cooled molecules and present a scheme based on optical pumping into a robust dark state at zero velocity. Using multi-level optical Bloch equations to simulate this scheme, we show that it may be feasible to reach the recoil limit or below. We demonstrate and characterise the method experimentally, cooling CaF molecules to 5.8(5) $\mu$K. We measure the complete velocity distribution directly by rotating the phase-space distribution in a harmonic magnetic trap and then imaging the cloud. Using the same phase-space rotation method, we rapidly compress the cloud. By applying the cooling method a second time, we compress the position and velocity distribution. [Preview Abstract] |
Friday, May 31, 2019 8:36AM - 8:48AM |
V05.00004: Realizing a High Number of Trapped Hydroxyl Radicals Dave Reens, Alexander Aeppli, Hao Wu, Piotr Wcislo, Anna McAuliffe, Jun Ye Ultracold molecules provide a fascinating opportunity to study fundamental physical processes at low energy. We describe recent experimental progress in cooling and trapping hydroxyl radicals(OH). Our apparatus cools OH through supersonic expansion, slows the molecular beam with a Stark decelerator, and traps the cold molecules with a magnetic trap. Building upon our previous work of cooling our molecular beam skimmer, we have implemented a cryogenic hexapole to focus the beam of expanding molecules, dramatically increasing the density by reducing clogging due to the carrier gas. New operational configurations for our Stark decelerator expand its phase space acceptance, increasing the total number of trapped molecules by a significant factor. Finally, a new magnetic trap significantly extends trapping lifetimes. These experimental improvements allow us to more precisely study collisional channels and reach even lower temperatures. [Preview Abstract] |
Friday, May 31, 2019 8:48AM - 9:00AM |
V05.00005: Cooling polyatomic molecules with single and double optical cycling centers Jacek Klos, Svetlana Kotochigova Cooling polyatomic molecules is challenging in comparison to atoms. Nevertheless, laser cooling to $\mu$K temperature of SrOH molecule by Dr.~Doyle's group [1] was possible due to the existence of diagonal Frank-Condon factors (FCFs) between the vibrational modes of optical transitions. To elucidate the role of molecular complexity on the diagonal nature of electronic transitions, we study optical transitions in the family of molecules M-O-(CH$_2)_n$-CH$_3$, where $n=1-3$ and optical cycling center (OCC) M=Sr or Ca. We have performed geometry optimization of ground X and excited A and B states using time-dependent density functional theory and simulated excitation spectra from the X (0,0,0) state to vibrational states of the A and B potentials. This has shown that FCFs are close to one for all systems but decrease with complexity indicating that longer chains of ligands do change the coupling between M and O and make cooling less efficient. The B state is more favorable for cooling. It can be advantageous to attach two OCCs, thereby possibly doubling the photon scattering rate. We show that cycling rates can indeed be significantly increased for MO-(CH$_2)_n$-CH$_3$-OM with two optical centers. [1] I. Kozyrev et al., Phys. Rev. Lett. 118, 173201 (2017). [Preview Abstract] |
Friday, May 31, 2019 9:00AM - 9:12AM |
V05.00006: Improving cryogenic buffer-gas beam collimation with de Laval nozzles David Lancaster, Cameron Allen, Kylan Jersey, Thomas Lancaster, Gage Shaw, Mckenzie Taylor, Di Xiao, Nicholas Hutzler, Jonathan Weinstein Cryogenic buffer-gas beam sources produce extremely high fluxes of cold molecular radicals. By using a converging-diverging nozzle, we have observed improved collimation and higher fluxes per solid angle. The beam properties were tested with atomic titanium and ytterbium; progress towards producing guided beams of CH radicals will be discussed. [Preview Abstract] |
Friday, May 31, 2019 9:12AM - 9:24AM |
V05.00007: Laser-cooled molecules for quantum science and ultracold chemistry Daniel McCarron Molecular laser cooling and trapping offers a general technique to produce ultracold molecules and is applicable to a variety of species with different internal structures. This generality is well-suited to the growing list of proposed applications for ultracold molecules, from time-resolved quantum simulations to ultracold organic chemistry. However, current limitations prevent the detection and manipulation of the necessary molecule-molecule interactions in laser-cooled samples. The key barrier is inefficient trap loading, which limits the densities achieved in molecular magneto-optical traps. Here we describe two complementary experiments designed to remove this barrier and realize large, dense samples of ultracold molecules. The first targets polar molecules with closed electronic shells, such as AlCl, which have strong optical transitions ideal for trap loading and weak transitions for laser cooling towards 1 $\mu $K. The second targets light, chemically relevant species with blue optical transitions such as CH and CN. These species can give access to increased optical forces and short slowing distances thanks to their high recoil velocities. We will discuss the advantages and challenges associated with laser cooling these new species and present an update on experimental progress. [Preview Abstract] |
Friday, May 31, 2019 9:24AM - 9:36AM |
V05.00008: Investigation of electric trap dynamics and Sisyphus cooling of formaldehyde using an improved detection scheme Martin Ibr\"{u}gger, Maximilian L\"{o}w, Martin Zeppenfeld, Gerhard Rempe The unique properties of cold polar molecules make them ideal systems for a wide variety of applications in quantum physics. We demonstrated in the past that optoelectrical Sisyphus cooling is a very promising approach to produce a large number of electrically trapped molecules at sub-millikelvin temperatures~[1], providing an ideal starting point for these applications. The implementation of an improved detection scheme based on laser induced fluorescence increased our signal by almost an order of magnitude with further improvements expected. Moreover, the method provides us with state selectivity and can even resolve single rotational M-sublevels. We thereby gain new insight into the dynamics of molecules in our electric trap, including, e.g. the state dependence of the contribution of Majorana losses to the trap lifetime and the state-dependent loading and unloading rates. Further investigation of the optoelectrical cooling scheme is expected to result in higher molecule numbers as well as lower temperatures. This will enable collisional studies and improved high-precision spectroscopy of cold formaldehyde in the near future.\newline[1] A. Prehn {\sl et al.}, {\sl Phys. Rev. Lett.} {\bf 116}, 063005 (2016) [Preview Abstract] |
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