Molekularstrahlmessungen von Stoßquerschnitten für Übergänge zwischen definierten Rotationszuständen zwei-atomiger Moleküle

Abstract

Inelastic collision cross sections for transitions between specified rotational states designated by (J, M) have been measured in a molecular beam apparatus. With an electrostatic four pole field molecules in a specified rotational state are separated out of a molecular beam and focussed into a gas filled scattering chamber. Molecules which have been scattered by less than 1/2° are then collected in a second four pole field, located directly behind the scattering chamber, and are analyzed for their rotational state. From a comparison of the measured pressure dependence with calculated curves a determination of inelastic collision cross sections for specified quantum jumps is possible. Measured inelastic scattering cross sections for the transitions (2,0→3,0) are reported for the gases He, Ne, Ar, Kr, CH₄, SF₆, H₂, O₂, Air, N₂O, H₂O, CF₂Cl₂. The values range between about 5 and 100 Ų in the order indicated. The scattering gases NH₃ und ND₃ yielded larger cross sections of about 600 Ų and, in addition, the transitions (3,0)→(2,0),(1,0)→(2,0), (2,0)→(1,0) and (3,0)→(1,0) were observed. Total cross sections for the same gases were also measured with the apparatus.