Collisional excitation transfer in high magnetic fields. I. Theory

Abstract

The effects of strong magnetic fields on thermal collisions in a vapor are reviewed. Semiclassical and quantum-mechanical symmetry properties of the relaxation matrix are established for resonant collisions between identical atoms and nonresonant collisions with a structureless partner. The variations with field strength of the transfer rates between Zeeman sublevels for ${R}^{\ensuremath{-}3}$ dipole-dipole interaction and ${R}^{\ensuremath{-}6}$ Van der Waals interaction are obtained with an exact semiclassical computation of the collision matrix. These are then compared with those predicted with an approximate formulation by means of the symmetrical correlation function for the potential.