15min:

STEVEN HOEKSTRA, JOOP J. GILIJAMSE, SEBASTIAAN Y. T. VAN DE MEERAKKER AND GERARD MEIJER, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany.

We report on the Stark-deceleration and electrostatic trapping of metastable NH molecules. Furthermore the progress towards higher densities of cold neutral molecules by accumulation of multiple Stark-decelerated packets of NH molecules in a magnetic trap will be presented.

NH molecules in the long-lived metastable a¹ (v=0, J=2) state are ideally suited for Stark deceleration experiments because of their relatively large Stark shift and low mass. The metastable molecules ( > 2.7 s) are produced in a supersonic expansion with a velocity of 450 m/s, and are decelerated to a standstill by a 108-stage decelerator. Subsequently the metastable molecules are trapped electrostatically, with a temperature of about 50 - 100 mK, a density of 10⁶ cm^-3 and a 1/e trapping lifetime of 1.4 s.

Following the deceleration and trapping, the metastable NH molecules are detected by the excitation of a spin-forbidden transition, resulting in spontaneous decay to the electronic ground state (X^{3 -}). The electronic ground state has a negligible Stark shift, but can be trapped magnetically. The first experiments on the accumulation of ground state NH molecules in a magnetic trap will be presented.

[1] S.~Hoekstra et al. , Electrostatic trapping of metastable NH molecules, Phys.~Rev.~A. \textbf76 063408 (2007)