DECELERATION, TRAPPING AND ACCUMULATION OF NH MOLECULES

Abstract

Author Institution: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, GermanyWe 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 $a^{1}\Delta (v=0, J=2)$ state are ideally suited for Stark deceleration experiments because of their relatively large Stark shift and low mass. The metastable molecules $(\tau > 2.7 s)$ are produced in a supersonic expansion with a velocity of $\sim 450$ 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 $\sim 10^{6}$ 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 ($X^{3}\Sigma^{-}$). 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 \emph{et al.}, Electrostatic trapping of metastable NH molecules, Phys.~Rev.~A. \textbf{76} 063408 (2007