Slowing Heavy, Ground-State Molecules using an Alternating Gradient Decelerator

We have decelerated a supersonic beam of ${}^{174}\mathrm{YbF}$ molecules using a switched sequence of electrostatic field gradients. These molecules are 7 times heavier than any previously decelerated. An alternating gradient structure allows us to decelerate and focus the molecules in their ground state. We show that the decelerator exhibits the axial and transverse stability required to bring the molecules to rest. Our work significantly extends the range of molecules amenable to this powerful method of cooling and trapping.

Figure 1

(a) The beam line. (b) Left: end view of one decelerator stage. Graph: Stark shift of ground state YbF within the stage versus $x$ and $y$ for electrode voltages of $\pm 10\mathrm{kV}$. (c) Same Stark shift versus $z$, plotted for one stage.

Figure 2

Time-of-flight profiles for $298\mathrm{m}/\mathrm{s}$ YbF beams with decelerator off (dotted lines) and on (solid lines). The time origin is defined by the Nd:YAG pulse. (a) Experiment using the whole pulse of molecules. (b) Simulation for (a). (c) Experiment using a velocity-selected pulse of molecules. (d) Simulation for (c). The vertical axes of the simulations are scaled to account for transverse focusing, which is not otherwise included.

Figure 3

Deceleration of YbF beams from various initial speeds. Dotted (solid) lines show time-of-flight profile with decelerator off (on). The $y$ axes indicate the fluorescence rates in the detector. (a) YbF in Ar. $v_i=586.3\pm 1.0\mathrm{m}/\mathrm{s}$, $\Delta v=5.1\pm 0.9\mathrm{m}/\mathrm{s}$, $\Delta E=48.1\pm 8.7{\mathrm{cm}}^{-1}$. (b) YbF in Kr. $v_i=421.8\pm 0.7\mathrm{m}/\mathrm{s}$, $\Delta v=6.9\pm 0.7\mathrm{m}/\mathrm{s}$, $\Delta E=46.8\pm 4.8{\mathrm{cm}}^{-1}$. (c) YbF in Xe. $v_i=335.1\pm 0.5\mathrm{m}/\mathrm{s}$, $\Delta v=9.3\pm 0.5\mathrm{m}/\mathrm{s}$, $\Delta E=50.0\pm 2.4{\mathrm{cm}}^{-1}$. (d) YbF in Xe cooled to 198 K. $v_i=286.5\pm 0.5\mathrm{m}/\mathrm{s}$, $\Delta v=10.2\pm 0.4\mathrm{m}/\mathrm{s}$, $\Delta E=46.6\pm 2.1{\mathrm{cm}}^{-1}$.

Figure 4

Change in speed of molecules versus decelerator phase angle for a beam of initial speed $335\mathrm{m}/\mathrm{s}$. Points: Measured data. Solid line: Simple theory for synchronous molecule. Crosses: Numerical simulation.

Figure 5

Normalized decelerator transmission versus (a) effective lens length at a voltage of $\pm 10\mathrm{kV}$, and (b) electrode voltage for a fixed lens length of 10 mm. Dotted lines: calculation using matrix approach.