Rotational Excitation of Symmetric-Top Molecules by Low-Energy Ion Impact

Theory of collisions between ions and symmetric-top molecules is formulated. This work is to investigate the adiabatic nature of low energy ion-polar molecule collisions. When the angular momentum quantum number projected on the symmetry axis of symmetric-top molecules is not zero, the elastic collision is significantly different from that where the molecule is linear, but not so much for the inelastic collision. Some discussions about the scaling law obtained by Takayanagi and about the modified Born approximation are given.