ON THE ROTATIONAL ANGULAR-MOMENTUM POLARIZATION IN N2(+)-HE - CLASSICAL TRAJECTORY AND HARD-ELLIPSOID MODEL-CALCULATIONS

Classical trajectory and hard-ellipsoid methods are used to investigate collision-induced rotational alignment effects in N2+-He. Classical total, m(f)-resolved, and tensor cross sections for collision-induced rotational transitions are presented. Comparison of classical trajectory and quantum closed-coupled results show that total rotational inelastic cross sections are in good agreement, while m(f)-resolved and tensor cross sections agree only semiquantitatively. Velocity-averaged alignment parameters for N2+ ions drifting in a helium buffer gas are computed using a hard-ellipsoid model and a semiempirical two-dimensional velocity distribution. The alignment parameters are found to be smaller than the experimental values but lie in the range of the parameters obtained from a former quantum closed-coupled analysis.