Trap loss in a metastable helium-rubidium magneto-optical trap

We present results of the study of a simultaneously confined metastable helium (He${}^{*}$) and rubidium magneto-optical trap (MOT). By monitoring the trap decay of the ${}^{87}\mathrm{Rb}$ MOT with and without a He${}^{*}$ MOT present, we find the light-assisted, two-body loss rate to be ${\beta }_{\mathrm{Rb}–{\mathrm{He}}^{*}}=(6\pm 2)\times {10}^{-10}\hspace{0.5em}{\mathrm{cm}}^3/\mathrm{s}$. Moreover, we find that it is possible to create a large, robust ${}^{87}\mathrm{Rb}$-He${}^{*}$ MOT, opening the possibility of creating a ${}^{87}\mathrm{Rb}$-He${}^{*}$ Bose-Einstein condensate. This would be the first dual-species condensate incorporating an alkali metal ground-state atom and an excited-state noble gas atom.

Figure 1

Simplified energy-level diagrams for He${}^{*}$ and ${}^{87}\mathrm{Rb}$ showing the laser transitions utilized.

Figure 2

Simplified MOT diagram with the beam layout. The patterned (blue) beams represent the ${}^{87}\mathrm{Rb}$ laser beams, whereas the solid (red) beams represent He${}^{*}$ laser beams.

Figure 3

Typical photodiode traces with the loading and decay of a ${}^{87}\mathrm{Rb}$ MOT, a He${}^{*}$ MOT, and ${}^{87}\mathrm{Rb}$ MOT with a He${}^{*}$ MOT present. Loss in the ${}^{87}\mathrm{Rb}$ MOT due to the He${}^{*}$ MOT can clearly be seen. The inset shows a saturated fluorescence measurement of the He${}^{*}$ number.

Figure 4

Averaged ${}^{87}\mathrm{Rb}$ MOT decay with and without a He${}^{*}$ MOT present; fitting to these curves yields $\alpha$, $\beta$, and ${\beta }_{\mathrm{Rb}–{\mathrm{He}}^{*}}$. Some points have been removed to improve clarity.