We demonstrate a single stage optical Stark decelerator for neutral molecules which reduced the velocity of benzene molecules in a molecular beam by 25 m/s corresponding to a kinetic energy reduction of 15 %.
We demonstrate a single stage optical Stark decelerator for neutral molecules which is capable of reducing the translational energy of benzene molecules within a molecular beam by 15% in a single pulsed Gaussian optical field of 15 ns duration. The change in velocity induced by the optical potential is measured by the change in the time of flight of benzene molecules ionized by a second optical field after the slowing field is turned off. A maximum reduction in the velocity of 25 m/s was measured using a single Gaussian beam with a peak intensity of 1.6 x 10(12) W/cm(2) corresponding to a maximum well depth of 253 K.
The deceleration of molecules from cold molecular beams using electric and magnetic fields has become an important means for producing stationary, cold dipolar or paramagnetic molecular gases that can be trapped and potentially cooled to ultra-cold temperatures in the μK range. We report on a general scheme for the creation of cold molecules of essentially any type by deceleration of a cold molecular beam using intense optical fields. Deceleration of benzene molecules to zero velocity is achieved by utilizing a single half oscillation of the center-of-mass motion of the molecules within a moving optical lattice. The lattice traveling at half the speed of the molecular beam is created by the interference of two near-counter-propagating fields at different frequencies. We show that by rapidly switching on the optical lattice for approximately the time required for a half oscillation, a bunch of approximately 10 5 benzene molecules can be rapidly decelerated and brought to rest in the laboratory frame.
We produce SO2 molecules with a centre of mass velocity near zero using a Stark decelerator. Since the initial kinetic energy of the supersonic SO2 molecular beam is high, and the removed kinetic energy per stage is small, 326 deceleration stages are necessary to bring SO2 to a complete standstill, significantly more than in other experiments. We show that in such a decelerator possible loss due to coupling between the motional degrees of freedom must be considered. Experimental results are compared with 3D Monte-Carlo simulations and the quantum state selectivity of the Stark decelerator is demonstrated.
We describe the deceleration of nitric oxide, benzene and xenon atoms in a molecular beam using one-dimensional pulsed optical lattices created by fields with intensities in the 1012 W cm−2 range. We show that for the same pulse duration and lattice intensity the velocity of the molecules can be controlled by tailoring the lattice velocity. By utilizing the time-dependent oscillatory motion of the molecules within the lattice, we demonstrate the deceleration of nitric oxide from an initial velocity of 400 m s−1 to a final velocity of 290 m s−1 in a single 5.8 ns pulse. Using higher intensities, we measure the deceleration of benzene molecules from 380 m s−1 to 191 m s−1, representing a 75% reduction in the kinetic energy within the lattice over the same duration.
In the last two decades, enormous progress has been made in the manipulation of molecular beams. In particular, molecular decelerators have been developed with which advanced control over neutral molecules in a beam can be achieved. By using arrays of inhomogeneous and time-varying electric (or magnetic) fields, bunches of molecules can be produced with a tunable velocity, narrow velocity spreads, and almost perfect quantum-state purity. These monochromatic or "tamed" molecular beams are ideally suited to be used in crossed-molecular-beam scattering experiments. Here, we review the first generation of these "cold and controlled" scattering experiments that have been conducted in the last decade and discuss the prospects for this emerging field of research in the years to come.
With a Stark decelerator, beams of neutral polar molecules can be accelerated, guided at a constant velocity, or decelerated. The effectiveness of this process is determined by the six-dimensional (6D) volume in phase space from which molecules are accepted by the Stark decelerator. Couplings between the longitudinal and transverse motion of the molecules in the decelerator can reduce this acceptance. These couplings are nearly absent when the decelerator operates such that only every third electric-field stage is used for deceleration, while extra transverse focusing is provided by the intermediate stages. For many applications, the acceptance of a Stark decelerator in this so-called s=3 mode significantly exceeds that of a decelerator in the conventionally used (s=1) mode. This has been experimentally verified by passing a beam of OH radicals through a $2.6\text{\ensuremath{-}}\mathrm{m}$-long Stark decelerator. The experiments are in quantitative agreement with the results of trajectory calculations, and can qualitatively be explained with a simple model for the 6D acceptance. These results imply that the 6D acceptance of a Stark decelerator in the s=3 mode of operation approaches the optimum value, i.e., the value that is obtained when any couplings are neglected.