Düsseldorf 2007 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 27: Kalte Moleküle II (gemeinsam mit MO)
Q 27.6: Vortrag
Dienstag, 20. März 2007, 15:30–15:45, 6B
Supersonic Beams at High Stagnation Pressures: Thermodynamics and Translational Cooling — •Wolfgang Christen, Tim Krause, Sibylle Rabeus, and Klaus Rademann — Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin, Germany
Pulsed, supersonic beams of rare gases at high stagnation pressures (10<p0<120 bar) have been investigated by time-of-flight measurements as a function of gas temperature T0. The numerical evaluation of the arrival time distribution f(t)dt permits an accurate determination of the velocity distribution, characterized by the flow velocity v0 and the velocity spread Δ v∥ of the expanded beam. We compare the experimental results v0(p0, T0) with values calculated for a supersonic expansion of an ideal gas. Because the translational cooling of a supersonic jet is usually characterized by the speed ratio S=v0/Δ v∥, we discuss the applicability of this approach at high pressure conditions. The effect of condensation on cooling is investigated by retarding field measurements, determining the cluster size distribution in the beam.
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