Relaxation of diatomic molecules by isotropic collisions: application to depolarizing collisions of CS by He atoms

摘要

An irreducible tensor formalism is applied to isotropic collisions of diatomic molecules with S-1 atoms. Explicit expressions of the generalized spectroscopic relaxation cross sections are given, including pressure broadening cross sections as well as collisional transfer and destruction cross sections of the k-component of the target density matrix. For applications in the high temperature limit, formulae within the infinite order sudden approximation (IOS) are given for (1)Sigma electronic state molecules and (2S+1)Sigma electronic state molecules in the Hund's case (b) limit. Application to collisions of CS by He atoms shows that a good agreement is found between close coupling and IOS results at moderate energies and that multipolar depolarizing rates within a j-level are of the same order of magnitude whatever the considered multipole order k whereas multipolar transfer rates are lower by an order of magnitude. Propensity rules in relation to the CS-He potential energy surface are given.