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MO: Molekülphysik

MO 36: Experimental Techniques

MO 36.1: Vortrag

Montag, 7. März 2005, 16:30–16:45, HU 2097

Hot reactive collisions as source for cold molecules — •Ning-Ning Liu and Hansjürgen Loesch — Fakultät für Physik, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld

A prerequisite for studying molecular physics at low energies is the generation and trapping of cold molecules. We have developed a novel source that creates cold metal-halide salt molecules which are, due to the low vapor pressures and high melting temperatures of these species, not in the reach of the presently available cooling techniques. Here, the cold salt molecules MX are formed in a reactive collision process of the type M+HX→MX+H (M and X denote metal and halogen atoms). Crucial for the present purpose is the extreme mass ratio of the products because in this case momentum conservation implies that the MX molecules nearly rest in the centre-of-mass frame. Using counter-propagating reagent beams with properly adjusted speeds the laboratory velocity of the centre-of-mass is set to (nearly) zero and hence the MX molecules nearly rest in the laboratory. As the molecules can be created at the potential energy minimum of the conservative electrostatic traps continuous loading is possible and may lead to high number densities. We report first time-of-flight distributions of cold KBr beams formed in the process K+HBr→KBr+H. They indicate peak velocities of <50m/s and still significant intensities below 30 m/s. In addition, the results of our experiments on guiding and trapping the salt molecules are presente