Locking of Intrinsic Angular Momenta in the Capture of Quadrupole Diatoms by Ions

Juergen Troe (1) , Evgueni E. Nikitin (2) , E. I. Dashevskaya (2) , I. Litvin (2)

1 Institut für Physikalische Chemie [Göttingen]
2 Technion - Israel Institute of Technology [Haifa]

The capture dynamics of rotationally polarized homonuclear diatoms in lowenergy collisions with ions is studied theoretically. The interaction potential includes charge-quadrupole and charge-induced dipole terms. The former, taken in the perturbed rotor approximation, exhibits an R−3 anisotropic dependence and causes an only gradual locking of the intrinsic angular momentum of the diatom to the collision axis. As a result, the capture occurs in a regime of incomplete locking, and the passage over centrifugal barriers is accompanied by considerable gyroscopic effects. The j-specific capture cross sections for rotationally-aligned diatoms show a marked dependence on the polarization state which is not described by the conventional adiabatic channel model. The latter, however, provides a fair approximation for the cross sections of unpolarized diatoms. These features are due to a considerable angle of rotation of the collision axis before the barrier is reached and to a small angle of rotation during the passage across the barrier. The numerically determined, scaled, capture cross sections are represented by an approximate analytical expression that interpolates between two limiting cases, very small (adiabatic channel model) and very large (fly wheel model) gyroscopic effects of the rotating diatom.

Mots clés: Physical Sciences

Juergen Troe, Evgueni E. Nikitin, E. I. Dashevskaya, I. Litvin. Locking of Intrinsic Angular Momenta in the Capture of Quadrupole Diatoms by Ions. Molecular Physics, 2010, 108 (07-09), pp.873-882. ⟨10.1080/00268970903501717⟩. ⟨hal-00596271⟩