The rich internal structure and long-range dipole-dipole interactions establish polar molecules as unique instruments for quantumcontrolled applications and fundamental investigations. Their potential fully unfolds at ultracold temperatures, where a plethora of effects is predicted in many-body physics [1,2], quantum information science [3,4], ultracold chemistry [5,6], and physics beyond the standard model [7,8]. These objectives have inspired the development of a wide range of methods to produce cold molecular ensembles [9][10][11][12][13][14]. However, cooling polyatomic molecules to ultracold temperatures has until now seemed intractable. Here we report on the experimental realization of opto-electrical cooling [15], a paradigm-changing cooling and accumulation method for polar molecules. Its key attribute is the removal of a large fraction of a molecule's kinetic energy in each step of the cooling cycle via a Sisyphus effect, allowing cooling with only few dissipative decay processes. We demonstrate its potential by reducing the temperature of about 10 6 trapped CH 3 F molecules by a factor of 13.5, with the phase-space density increased by a factor of 29 or a factor of 70 discounting trap losses. In contrast to other cooling mechanisms, our scheme proceeds in a trap, cools in all three dimensions, and works for a large variety of polar molecules. With no fundamental temperature limit anticipated down to the photon-recoil temperature in the nanokelvin range, our method eliminates the primary hurdle in producing ultracold polyatomic molecules. The low temperatures, large molecule numbers and long trapping times up to 27 s will allow an interaction-dominated regime to be attained, enabling collision studies and investigation of evaporative cooling toward a BEC of polyatomic molecules.The ability to prepare ultracold molecular ensembles has an application potential akin to that of ultracold atoms some decades ago. In fact, the association of KRb dimers [16] as well as the laser cooling of SrF [17] has brought fascinating physics within reach. However, both approaches are restricted to a highly specialized set of purely diatomic molecule species. In order to investigate fundamental physics based on relativistic effects near heavy nuclei or parity violation effects in chiral molecules, or to study molecules of astrophysical, biological, or chemical interest, a more general approach to preparing ultracold molecular ensemble is imperative. This holds in particular for the rich chemical variety of carbon-, nitrogen-, or oxygen-based molecules for which the constituent atoms have not even been laser cooled. Devising a dissipative process to cool such molecules into the ultracold regime has been an exceedingly challenging problem. The standard approach for atoms, laser cooling, is in general impossible for molecules due to the lack of suitable cycling transitions. Creating an artificial cycling transition via cavity cooling [18] has not been demonstrated despite substantial experimental [19] and theoretical [20][21][...

We present a method which delivers a continuous, high-density beam of slow and internally cold polar molecules. In our source, warm molecules are first cooled by collisions with a cryogenic helium buffer gas. Cold molecules are then extracted by means of an electrostatic quadrupole guide. For ND3 the source produces fluxes up to (7± 7 4 ) × 10 10 molecules/s with peak densities up to (1.0± 1.0 0.6 ) × 10 9 molecules/cm 3 . For H2CO the population of rovibrational states is monitored by depletion spectroscopy, resulting in single-state populations up to (82 ± 10)%.

The energy-resolved rate coefficient for the dissociative recombination (DR) of H(3)(+) with slow electrons has been measured by the storage-ring method using an ion beam produced from a radiofrequency multipole ion trap, employing buffer-gas cooling at 13 K. The electron energy spread of the merged-beams measurement is reduced to 500 microeV by using a cryogenic GaAs photocathode. This and a previous cold- measurement jointly confirm the capability of ion storage rings, with suitable ion sources, to store and investigate H(3)(+) in the two lowest, (J,G) = (1,1) and (1,0) rotational states prevailing also in cold interstellar matter. The use of para-H(2) in the ion source, expected to enhance para-H(3)(+) in the stored ion beam, is found to increase the DR rate coefficient at meV electron energies.

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We present a versatile electric trap for the exploration of a wide range of quantum phenomena in the interaction between polar molecules. The trap combines tunable fields, homogeneous over most of the trap volume, with steep gradient fields at the trap boundary. An initial sample of up to 10(8), CH(3)F molecules is trapped for as long as 60 s, with a 1/e storage time of 12 s. Adiabatic cooling down to 120 mK is achieved by slowly expanding the trap volume. The trap combines all ingredients for opto-electrical cooling, which, together with the extraordinarily long storage times, brings field-controlled quantum-mechanical collision and reaction experiments within reach.

We present an opto-electrical cooling scheme for polar molecules based on a Sisyphus-type cooling cycle in suitably tailored electric trapping fields. Dissipation is provided by spontaneous vibrational decay in a closed level scheme found in symmetric-top rotors comprising six low-field-seeking rovibrational states. A generic trap design is presented. Suitable molecules are identified with vibrational decay rates on the order of 100 Hz. A simulation of the cooling process shows that the molecular temperature can be reduced from 1 K to 1 mK in approximately 10 s. The molecules remain electrically trapped during this time, indicating that the ultracold regime can be reached in an experimentally feasible scheme.

A supersonic beam of metastable neon atoms has been decelerated by exploiting the interaction between the magnetic moment of the atoms and time-dependent inhomogeneous magnetic fields in a multistage Zeeman decelerator. Using 91 deceleration solenoids, the atoms were decelerated from an initial velocity of 580 m/s to final velocities as low as 105 m/s, corresponding to a removal of more than 95 % of their initial kinetic energy. The phase-space distribution of the cold, decelerated atoms was characterized by time-of-flight and imaging measurements, from which a temperature of 10 mK was obtained in the moving frame of the decelerated sample. In combination with particletrajectory simulations, these measurements allowed the phase-space acceptance of the decelerator to be quantified. The degree of isotope separation that can be achieved by multistage Zeeman deceleration was also studied by performing experiments with pulse sequences generated for 20 Ne and 22 Ne.

We describe the combination of buffer-gas cooling with electrostatic velocity filtering to produce a high-flux continuous guided beam of internally cold and slow polar molecules. In a previous paper (L.D. van Buuren et al., arXiv: 0806.2523v1) we presented results on density and state purity for guided beams of ammonia and formaldehyde using an optimized set-up. Here we describe in more detail the technical aspects of the cryogenic source, its operation, and the optimization experiments that we performed to obtain best performance. The versatility of the source is demonstrated by the production of guided beams of different molecular species.