Low-energy molecular collisions in a permanent magnetic trap

Cold, neutral hydroxyl radicals are Stark decelerated and confined within a magnetic trap consisting of two permanent ring magnets. The OH molecules are trapped in the ro-vibrational ground state at a density of $\sim10^{6}$ cm$^{-3}$ and temperature of 70 mK. Collisions between the trapped OH sample and supersonic beams of atomic He and molecular D$_{2}$ are observed and absolute collision cross sections measured. The He--OH and D$_{2}$--OH center-of-mass collision energies are tuned from 60 cm$^{-1}$ to 230 cm$^{-1}$ and 145 cm$^{-1}$ to 510 cm$^{-1}$, respectively, yielding evidence of reduced He--OH inelastic cross sections at energies below 84 cm$^{-1}$, the OH ground rotational level spacing.Comment: 4 pages, 4 figure

Cold heteromolecular dipolar collisions

We present the first experimental observation of cold collisions between two different species of neutral polar molecules, each prepared in a single internal quantum state. Combining for the first time the techniques of Stark deceleration, magnetic trapping, and cryogenic buffer gas cooling allows the enhancement of molecular interaction time by 10$^5$. This has enabled an absolute measurement of the total trap loss cross sections between OH and ND$_3$ at a mean collision energy of 3.6 cm$^{-1}$ (5 K). Due to the dipolar interaction, the total cross section increases upon application of an external polarizing electric field. Cross sections computed from \emph{ab initio} potential energy surfaces are in excellent agreement with the measured value at zero external electric field. The theory presented here represents the first such analysis of collisions between a $^2\Pi$ radical and a closed-shell polyatomic molecule.Comment: 7 pages, 5 figure

Magneto-Optical Trap for Polar Molecules

We propose a method for laser cooling and trapping a substantial class of polar molecules, and in particular titanium (II) oxide (TiO). This method uses pulsed electric fields to nonadiabatically remix the ground-state magnetic sublevels of the molecule, allowing us to build a magneto-optical trap (MOT) based on a quasi-cycling $J'=J"-1$ transition. Monte-Carlo simulations of this electrostatically remixed MOT (ER-MOT) demonstrate the feasibility of cooling TiO to a temperature of 10 $\mathrm{\mu}K$ and trapping it with a radiation-pumping-limited lifetime on the order of 80 ms.Comment: 4 pages, 4 figures, 1 table v2: updated to final published text and figure

Cold heteromolecular dipolar collisions

We present the first experimental observation of cold collisions between two different species of neutral polar molecules, each prepared in a single internal quantum state. Combining for the first time the techniques of Stark deceleration, magnetic trapping, and cryogenic buffer gas cooling allows the enhancement of molecular interaction time by 10$^5$. This has enabled an absolute measurement of the total trap loss cross sections between OH and ND$_3$ at a mean collision energy of 3.6 cm$^{-1}$ (5 K). Due to the dipolar interaction, the total cross section increases upon application of an external polarizing electric field. Cross sections computed from \emph{ab initio} potential energy surfaces are in excellent agreement with the measured value at zero external electric field. The theory presented here represents the first such analysis of collisions between a $^2\Pi$ radical and a closed-shell polyatomic molecule.Comment: 7 pages, 5 figure

The Bose-Einstein Condensate and Cold Atom Laboratory

Microgravity eases several constraints limiting experiments with ultracold andcondensed atoms on ground. It enables extended times of flight withoutsuspension and eliminates the gravitational sag for trapped atoms. Theseadvantages motivated numerous initiatives to adapt and operate experimentalsetups on microgravity platforms. We describe the design of the payload,motivations for design choices, and capabilities of the Bose-Einstein Condensateand Cold Atom Laboratory (BECCAL), a NASA-DLR collaboration. BECCALbuilds on the heritage of previous devices operated in microgravity, featuresrubidium and potassium, multiple options for magnetic and optical trapping,different methods for coherent manipulation, and will offer new perspectives forexperiments on quantum optics, atom optics, and atom interferometry in theunique microgravity environment on board the International Space Station