Laurens D. van Buuren

Sisyphus cooling of electrically trapped polyatomic molecules

Polar molecules have a rich internal structure and long-range dipole–dipole interactions, making them useful for quantum-controlled applications and fundamental investigations. Their potential fully unfolds at ultracold temperatures, where various effects are predicted in many-body physics, quantum information science, ultracold chemistry and physics beyond the standard model. Whereas a wide range of methods to produce cold molecular ensembles have been developed, the cooling of polyatomic molecules (that is, with three or more atoms) to ultracold temperatures has seemed intractable. Here we report the experimental realization of optoelectrical cooling, a recently proposed 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 cycle of the cooling sequence via a Sisyphus effect, allowing cooling with only a few repetitions of the dissipative decay process. We demonstrate the potential of optoelectrical cooling by reducing the temperature of about one million CH3F 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 should work for a large variety of polar molecules. With no fundamental temperature limit anticipated down to the photon-recoil temperature in the nanokelvin range, we expect our method to be able to produce ultracold polyatomic molecules. The low temperatures, large molecule numbers and long trapping times of up to 27 seconds should allow an interaction-dominated regime to be attained, enabling collision studies and investigation of evaporative cooling towards a Bose–Einstein condensate of polyatomic molecules.

Electrostatic Extraction of Cold Molecules from a Cryogenic Reservoir

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+/- 4(7)) x 10(10) molecules/s with peak densities up to (1.0+/- 0.6(1.0)) x 10(9) molecules/cm3. For H2CO the population of rovibrational states is monitored by depletion spectroscopy, resulting in single-state populations up to (82+/-10)%.

Continuous guided beams of slow and internally cold polar molecules.

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., Phys. Rev. Lett., 2009, 102, 033001) 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 the best performance. The versatility of the source is demonstrated by the production of guided beams of different molecular species.

Velocity-selected molecular pulses produced by an electric guide

Electrostatic velocity filtering is a technique for the production of continuous guided beams of slow polar molecules from a thermal gas. We extended this technique to produce pulses of slow molecules with a narrow velocity distribution around a tunable velocity. The pulses are generated by sequentially switching the voltages on adjacent segments of an electric quadrupole guide synchronously with the molecules propagating at the desired velocity. This technique is demonstrated for deuterated ammonia (ND

Cold guided beams of water isotopologs

{}_{3}

Collisional effects in the formation of cold guided beams of polar molecules

), delivering pulses with a velocity in the range of

Electrically guided continuous supersonic beams of polar molecules from a cryogenic buffer-gas source

20\ensuremath{-}100

The Charge Form Factor of the Neutron from (, e' n)p

m/s and a relative velocity spread of

The charge form factor of the neutron from H ? 2 ( e ? , e ' n ) p

(16\ifmmode\pm\else\textpm\fi{}2)%

The Charge Form Factor of the Neutron from the Reaction ²{rvec H}({rvec e},en)p

at full width at half maximum. At velocities around