[en] Studies of collisional alignment in molecular beams can yield information about the anisotropic part of the scattering cross section. Here the authors report on measurements of the degree of alignment in Na₂ beams arising from scattering by noble gases. Use is made of the technique of laser-induced fluorescence. (Auth.)

[en] Quantitative results have been obtained for the alignment, due to optical pumping, in a beam of Na₂ molecules. This laser-induced alignment offers the possibility of experiments with strongly aligned beams of diatomic molecules in specific internal states. (Auth.)

[en] The magnetic field effect on the viscosity has been measured for several polyatomic gases with the emphasis on symmetric top molecules with strong electric dipoles. Theoretical expressions are given for the field dependent viscosity coefficients for various types of angular momentum polarizations, both for linear and symmetric top molecules. For CO₂, OCS, N₂O, SF₆, CH₃F, CHF₃, PF₃ and NF₃ a decrease of the viscosity in a magnetic field was observed, which can be well described on the basis of a single angular momentum tensor polarization of the type JJ. For NH₃ and ND₃, however, an increase in the viscosity was observed. In this case, a single polarization of the type WWJ is involved. For HCl, DCl, AsH₃ and PH₃ no effects could be observed (mod(Δeta/eta)<=2x10^-5). No simple correlation is found between the magnitude of the effect and the strength of the molecular electric dipole moment. The experimental results are expressed in terms of effective cross sections. (Auth.)