Advanced switching schemes in a Stark decelerator

We revisit the operation of the Stark decelerator and present a new, optimized operation scheme, which substantially improves the efficiency of the decelerator at both low and high final velocities, relevant for trapping experiments and collision experiments, respectively. Both experimental and simulation results show that this new mode of operation outperforms the schemes which have hitherto been in use. This new mode of operation could potentially be extended to other deceleration techniques

A Stark decelerator on a chip

A microstructured array of 1254 electrodes on a substrate has been configured to generate an array of local minima of electric field strength with a periodicity of 120 $\mu$m about 25 $\mu$m above the substrate. By applying sinusoidally varying potentials to the electrodes, these minima can be made to move smoothly along the array. Polar molecules in low-field seeking quantum states can be trapped in these traveling potential wells. Recently, we experimentally demonstrated this by transporting metastable CO molecules at constant velocities above the substrate [Phys. Rev. Lett. 100 (2008) 153003]. Here, we outline and experimentally demonstrate how this microstructured array can be used to decelerate polar molecules directly from a molecular beam. For this, the sinusoidally varying potentials need to be switched on when the molecules arrive above the chip, their frequency needs to be chirped down in time, and they need to be switched off before the molecules leave the chip again. Deceleration of metastable CO molecules from an initial velocity of 360 m/s to a final velocity as low as 240 m/s is demonstrated in the 15-35 mK deep potential wells above the 5 cm long array of electrodes. This corresponds to a deceleration of almost $10^5$ $g$, and about 85 cm$^{-1}$ of kinetic energy is removed from the metastable CO molecules in this process.Comment: 17 pages, 6 figure

Nonadiabatic transitions in electrostatically trapped ammonia molecules

Nonadiabatic transitions are known to be major loss channels for atoms in magnetic traps, but have thus far not been experimentally reported upon for trapped molecules. We have observed and quantified losses due to nonadiabatic transitions for three isotopologues of ammonia in electrostatic traps, by comparing the trapping times in traps with a zero and a non-zero electric field at the center. Nonadiabatic transitions are seen to dominate the overall loss rate even for samples at relatively high temperatures of 10-50 mK

Alternating-Gradient Focusing of the Benzonitrile-Argon Van der Waals Complex

We report on the focusing and guiding of the van der Waals complex formed between benzonitrile molecules (C$_6$H$_5$CN) and argon atoms in a cold molecular beam using an ac electric quadrupole guide. The distribution of quantum states in the guided beam is non-thermal, because the transmission efficiency depends on the state-dependent effective dipole moment in the applied electric fields. At a specific ac frequency, however, the excitation spectrum can be described by a thermal distribution at a rotational temperature of 0.8 K. From the observed transmission characteristics and a combination of trajectory and Stark-energy calculations we conclude that the permanent electric dipole moment of benzonitrile remains unchanged upon the attachment of the argon atom to within \pm5%. By exploiting the different dipole-moment-to-mass (\mu/m) ratios of the complex and the benzonitrile monomer, transmission can be selectively suppressed for or, in the limit of 0 K rotational temperature, restricted to the complex.Comment: to be published in JC

Die skoolorde van Genève 1559: ’n Basis vir ’n gereformeerde skoolorde

The school order of Genève 1559: A basis for a reformed school order. Calvin and education are synonymous. Apart from his written legacy, which speaks of his intense love for education, he endeavoured to put schools in place where young people could be educated in the ways of the Lord. This was not only in the curriculum, but also in the way it was presented and the teachers who presented those lessons received special attention from Calvin. The light of God’s Word is shed over everything. This article shows how, given his own historical background and the tools available to him, he tried to develop a school system in the city of Geneva where children could be educated in accordance with the promise of their parents at their baptism. The school order of Geneva (1559) in conjunction with the Genevan Church order (1561) gives us insight in the doings and thoughts of Calvin on education. I hope to indicate some lines that could be of use in the present dialogue on educational matters. Sadly, the way Calvin set up a system for education is no longer evident in schools. Isn’t there an urgent need for a well-defined and fundamental school order amongst all the school policies and rules? This question will receive attention in the article

Emerging beam resonances in atom diffraction from a reflection grating

We report on the observation of emerging beam resonances, well known as Rayleigh-Wood anomalies and threshold resonances in photon and electron diffraction, respectively, in an atom-optical diffraction experiment. Diffraction of He atom beams reflected from a blazed ruled grating at grazing incidence has been investigated. The total reflectivity of the grating as well as the intensities of the diffracted beams reveal anomalies at the Rayleigh angles of incidence, i.e., when another diffracted beam merges parallel to the grating surface. The observed anomalies are discussed in terms of the classical wave-optical model of Rayleigh and Fano.Comment: 4 pages, 3 figure

Phase Space Manipulation of Cold Free Radical OH Molecules

We report bunching, slowing, and acceleration of a supersonically cooled beam of diatomic hydroxyl radicals (OH). \textit{In situ} observation of laser-induced fluorescence along the beam propagation path allows for detailed characterization of longitudinal phase-space manipulation of OH molecules through the Stark effect by precisely sequenced inhomogeneous electric fields.Comment: 5 pages, 4 color figure

Deceleration of neutral molecules in macroscopic traveling traps

A new type of decelerator is presented where polar neutral molecules are guided and decelerated using the principle of traveling electric potential wells, such that molecules are confined in stable three-dimensional traps throughout. This new decelerator is superior to the best currently operational decelerator (Scharfenberg et al., Phys.Rev.A 79, 023410(2009)), providing a substantially larger acceptance even at higher accelerations. The mode of operation is described and experimentally demonstrated by guiding and decelerating CO molecules.Comment: 10 pages, 3 figure