• Corpus ID: 174793958

An experimental toolbox for the generation of cold and ultracold polar molecules

@inproceedings{Bronin2016AnET,
  title={An experimental toolbox for the generation of cold and ultracold polar molecules},
  author={S. Ya. Bronin and Wan Peng-jun and Mumtaz Murat Arik and Romain Vexiau and Ian B. Whittingham},
  year={2016}
}

• S. Bronin, Wan Peng-jun, +2 authors I. Whittingham
• Published 2016
• Physics

Cold and ultracold molecules enable fascinating applications in quantum science. We present our toolbox of techniques to generate the required molecule ensembles, including buffergas cooling, centrifuge deceleration and optoelectrical Sisyphus cooling. We obtain excellent control over both the motional and internal molecular degrees of freedom, allowing us to aim at various applications. Molecules cooled to very low temperatures offer an exciting platform to investigate quantum phenomena. Thus, precision measurements on molecules allow the investigation of fundamental symmetries of nature [1]. Investigation of chemical reactions at low temperatures provides insight into chemical processes in interstellar space [2]. Moreover, the long-range dipole-dipole interactions between polar molecules and the variety of internal molecular states would be ideal for quantum information processing [3], and for investigation of many body physics in quantum degenerate gases [4]. In this summary, we present our multistep approach for generating internal state controlled molecular ensembles at cold (. 1K) and ultracold (. 1 mK) temperatures. First, an initial sample of cold molecules is generated via velocity filtering [5] or buffergas cooling [6]. Second, molecules are decelerated via a centrifuge decelerator [7]. Third, molecules are trapped in a microstructured electric trap [8]. Fourth, cooling to sub-millikelvin temperatures is achieved via optoelectrical Sisyphus cooling [9, 10, 11]. Control of the internal molecular state is achieved either by buffergas cooling [6, 12], or by optical pumping via a vibrational transition [13]. For all our experiments, we make use of the strong interaction between polar molecules and static electric fields. For laboratory fields of up to 100 kV/cm, interaction energies on the order of 1K×kB are possible, allowing for guiding and trapping of low-field-seeking states. As a first application, filtering of the low-velocity tail of the Maxwell-Boltzmann velocity distribution emerging from an effusive molecule source using a quadrupole electric guide provides a robust high-flux source of cold polar molecules [5]. Alternatively, pre-cooling via a Helium buffergas at ∼ 5K in a buffergas cell is possible [6]. For velocity filtering or buffergas cooling, the slowest molecules are reduced or eliminated, respectively, due to collisions with faster molecules and/or Helium atoms at the source [14]. To provide a large flux of slow molecules, we have developed a centrifuge decelerator for molecules [7], allowing for deceleration of continuous beams of molecules. Molecules in a labfixed quadrupole guide are injected into a quadrupole guide at the periphery of a rotating disk. A MPLP-2016 IOP Publishing IOP Conf. Series: Journal of Physics: Conf. Series 793 (2017) 012035 doi:10.1088/1742-6596/793/1/012035 International Conference on Recent Trends in Physics 2016 (ICRTP2016) IOP Publishing Journal of Physics: Conference Series 755 (2016) 011001 doi:10.1088/1742-6596/755/1/011001 Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by IOP Publishing Ltd 1 Figure 1. Centrifuge decelerator for polar molecules. Molecules enter the centrifuge in the lower left and exit along the axis in the center. quadrupole guide on the rotating disk guides the molecule to the center of the disk where they are transferred back to a lab-fixed guide along the axis of rotation. Due to the centrifugal potential in the rotating frame, molecules are thereby decelerated. Molecules with initial velocities > 150 m/s can be decelerated almost to a standstill. A clever design of the transition from the lab-fixed quadrupole guide to the rotating quadrupole guide allows for deceleration of continuous rather than pulsed molecular beams [7]. Molecules with a kinetic energy below roughly 1 K×kB can be loaded into an electrostatic trap. In our experiments, we make use of a unique trap design, with molecules trapped between a pair of microstructured capacitor plates, with an additional perimeter electrode for transverse confinement [8, 9]. In addition to providing record trap lifetimes of up to a minute [11], this trap design provides homogeneous electric fields in a large fraction of the trap volume. This is ideal for spectroscopic applications and to selectively address individual molecular rotational states via microwave and infrared radiation. Figure 2. Operation principle of optoelectrical Sisyphus cooling, as explained in the text. Most applications of cold molecules require temperatures substantially below the ∼ 1K achievable with the previously mentioned techniques. For this purpose, we have developed MPLP-2016 IOP Publishing IOP Conf. Series: Journal of Physics: Conf. Series 793 (2017) 012035 doi:10.1088/1742-6596/793/1/012035