From DNA Bases to Ultracold Atoms: Probing Ensembles Using Supersonic Beams

Stephen G. Benka

Erik Anciaux, Georgios Stratis, Mark G. Raizen

Abstract Well-collimated, high-intensity beams of neutral atoms have many applications ranging from atom microscopy to atom interferometry to ultracold atomic physics. We experimentally demonstrate a method for brightening a supersonic atomic beam and observe an increase in the phase space density by a factor of at least 20. Our scheme relies upon a permanent magnetic hexapole lens to focus a divergent beam of neutral atoms emitted from a supersonic nozzle and transverse laser cooling as the beam converges downstream from the lens so as to create a dense, narrow, Doppler-collimated atomic beam. In principle, this method can be repeated multiple times in series for further beam brightening.

Claude N. Cohen-Tannoudji

Yang Liu, Manish Vashishta, Pavle Djuricanin +5 more

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 >5.0×10^{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.

Jonas Grzesiak, Takamasa Momose, Frank Stienkemeier +2 more

We describe an experimental setup comprised of a discharge source for supersonic beams of metastable He atoms and a magneto-optical trap (MOT) for ultracold Li atoms that makes it possible to study Penning ionization and associative ionization processes at high ion count rates. The cationic reaction products are analyzed using a novel ion detection scheme which allows for mass selection, a high ion extraction efficiency, and a good collision-energy resolution. The influence of elastic He-Li collisions on the steady-state Li atom number in the MOT is described, and the collision data are used to estimate the excitation efficiency of the discharge source. We also show that Penning collisions can be directly used to probe the temperature of the Li cloud without the need for an additional time-resolved absorption or fluorescence detection system.

Claude N. Cohen-Tannoudji