Investigators:Marek Haruza, Maitreyi Jayaseelan, and N.P. Bigelow (recent graduates)
We create ultracold NaCs (sodium cesium) molecules in the absolute rotational and vibrational ground state using a variety of methods. The molecules are created via photoassociation from two overlapped magneto-optical traps (MOTs), and are detected using a photoionization process.
Our deeply bound, absolute ground state NaCs molecules have been trapped using electrostatic fields created by the Thin WIre electroStatic Trap (TWIST). This configuration takes advantage of the 4.6 Debye electric dipole moment of NaCs, which is one of the largest for bi-alkali molecules. The TWIST enabled our molecular sample to be isolated from the sodium andcesium atomic clouds. For the first time, any atomic signal detected during photoionization had to be from photofragmented molecules. This phenomena is currently being studied in the lab. The TWIST also provided an environment to study atom-molecule collisions which become significant when studying sypmathetic cooling of the molecular sample.
We have demonstrated efficient cooling of the rotational degree of freedom of ultracold NaCs molecules through narrow line optical pumping. Molecules in v''=0, N''=2 and 4 are excited to the lowest vibrational level of the A-singlet-Σ+ − b-triplet-Π complex from which they decay to v''=0, N''=0. We achieve cooling of both rotational and vibrational degrees of freedom by applying this technique in conjunction with broadband optical pumping. This technique also allows transfer of population between any of the lowest vibrational states (v''=0-2) at kHz rates.
Our other main effort at the moment is spectroscopy. We have taken over 60 nm worth of Photoionization spectra to determine vibrational distribution in the ground state. We have also performed depletion spectrosocpy to determine rotational structure within a given vibrational state.
Lasers involved in the effort:
This work has been supported by The National Science Foundation (NSF), The Army Research Office (ARO) of the United States Army Research Laboratory (ARL), The Defense Advanced Research Projects Agency (DARPA) of The United States Department of Defense (DOD), and the NASA-JPL Physical Science Research Program Cold Atom Laboratory (CAL).