Traveling-wave deceleration of heavy polar molecules in low-field-seeking states

We demonstrate the deceleration of heavy polar molecules in low-field-seeking states by combining a cryogenic source and a traveling-wave Stark decelerator. The cryogenic source provides a high-intensity beam with low speed and temperature, and the traveling-wave decelerator provides large deceleration forces and high phase-space acceptance. We prove these techniques using YbF molecules and find the experimental data to be in excellent agreement with numerical simulations. These methods extend the scope of Stark deceleration to a very wide range of molecules.

Figure 1

(a) Stark shifts of low-lying rotational states $(N,M_N)$ of YbF, and hyperfine components of $N=2$ (inset). (b) Schematic of the experiment, not to scale. (c) Contour plot of the potential energy of YbF $(N=2,M_N=0)$ molecules in a plane through the center of the ring decelerator. Contours are drawn at 50 mK intervals, and labeling is in mK. The traps move along the decelerator at a speed governed by the frequency of the applied sinusoidal voltages.

Figure 2

Time-of-flight distributions of YbF molecules in $N=2$, (a) measured and (b) simulated. Profiles are offset vertically for clarity. The decelerator is set to decelerate molecules from an initial speed of 300 m s${}^{-1}$. Decelerations and final speeds of the decelerated molecules are (i) 0 m s${}^{-2}$, 300 m s${}^{-1}$, (ii) 3710 m s${}^{-2}$, 294 m s${}^{-1}$, (iii) 7350 m s${}^{-2}$, 288 m s${}^{-1}$, (iv) 10 900 m s${}^{-2}$, 282 m s${}^{-1}$, and (v) 14 400 m s${}^{-2}$, 276 m s${}^{-1}$.

Figure 3

Light points: longitudinal positions and speeds of simulated molecules at the moment when the decelerator is turned on. Dark points: those molecules that produce the labeled peaks in Fig. 2. Bold lines: region that encloses the trapped molecules (the separatrix), calculated analytically.

Figure 4

Calculated phase-space acceptance of the decelerator vs deceleration for YbF in $(N,M_N)=(2,0)$.