Differentielle Streuquerschnitte bei der Wechselwirkung neutraler Moleküle Messungen der Kleinwinkelstreuung

A molecular beam apparatus of high angular resolution is described, and measurements of the angular intensity distribution of alkali beams scattered at small angles (15 seconds of arc to 1 degree) by crossed beams of various gases and vapours are presented. Formulas, connecting the measured intensity with the differential cross section in the center of mass system, are derived, considering the velocity distribution in the beams and the geometry of the experimental set-up. The measurements show, that the differential cross section can be calculated down to very low angles (order of magnitude 10 minutes of arc) by means of classical mechanics, taking only into account the long-range attractive van der Walls interaction. At smaller angles, deviations, predicted by quantum mechanics, can be observed. If the potential of the van der Waals forces is written in the formV(r)=?C/r ^s, a method is outlined to determine bothC ands from the measured angular intensity distribution.     

Verschiebung von Energietermen neutraler Moleküle bei thermischer Bewegung im elektrischen und magnetischen Feld

The effect of motional fields on the termenergies of neutral thermal molecules, as measured in a Rabi-type apparatus, has been calculated and measured. It is shown, in which cases this effect has to be considered.