On the rotational angular momentum polarization in N+2–He. Classical trajectory and hard-ellipsoid model calculations

Abstract

Classical trajectory and hard‐ellipsoid methods are used to investigate collision‐induced rotational alignment effects in N⁺₂–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 N⁺₂ 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.