Disalignment transitions in cold collisions of3Patoms with structureless targets in a magnetic field

A method for quantum-mechanical calculations of cross sections for the Zeeman transitions in collisions of {sup 3}P atoms with structureless targets in a magnetic field is presented and applied to the study of magnetic and electronic relaxation in oxygen-helium and carbon-helium collisions at cold and ultracold temperatures. The rate constants for collisionally induced transitions between Zeeman levels in ground-state oxygen have large magnitudes in a 1 T field. It is shown that magnetic fields induce the forbidden {sup 3}P{sub 1} {yields} {sup 3}P{sub 0} transition in ultracold collisions of carbon with helium. The cross section vanishes at zero energy for field-free collisions, but becomes infinitely large in a finite magnetic field, varying with velocity v and magnetic field B as B{sup 2}/v.