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A superconducting Fabry–Perot microwave cavity for a molecular trap was designed, constructed and characterized. The cavity was designed to create intense microwave fields that are sufficient to trap cold polar molecules by the AC Stark force. By coating the mirror surfaces with a superconducting material, an unloaded quality factor of up to 1.1 × 106 at 24.087 GHz was achieved at a temperature of 2.24 K. The field strength of 1.06 MV m−1 obtained for a TEM02 transverse mode with an input power of 10 W is sufficiently intense to trap ammonia molecules at a temperature of 85 mK, which is achievable by a conventional Stark molecular decelerator. We have also implemented an ion optics assembly for sensitive detection of molecules inside the microwave cavity by resonance enhanced multi-photon ionization.

We present a comparison of two technically distinct methods for the generation of rotationally cold, pulsed supersonic beams of methyl radicals (CH3): a plate discharge source operating in the glow regime and a dielectric barrier discharge source. The results imply that the efficiency of both sources is comparable and that molecular beams with similar translational and rotational temperatures are formed. Methane (CH4) proved to be the most suitable radical precursor species. (c) 2018 Author(s).

We have demonstrated that a supersonic beam of methyl radicals (CH$_3$) in the ground rotational state of both $para$ and $ortho$ species has been slowed down to standstill with a magnetic molecular decelerator, and successfully captured spatially in an anti-Helmholtz magnetic trap for $>$ 1 s. The trapped CH$_3$ radicals have a mean translational temperature of about 200 mK with an estimated density of $>5.0\times10^7$ cm$^{-3}$. The methyl radical is an ideal system for the study of cold molecules not only because of its high reactivities at low temperatures, but also because further cooling below 1 mK is plausible via sympathetic cooling with ultracold atoms. The demonstrated trapping capability of methyl radicals opens up various possibilities for realizing ultracold ensembles of molecules towards Bose-Einstein condensation of polyatomic molecules and investigations of reactions governed by quantum statistics.