Zeeman coherences relaxation in the ground state of alkali-metal atoms induced by spin-exchange collisions and collisions with buffer gas atoms

The evolution equation of the ground state density matrix elements (Zeeman ground state coherences) of alkali metal vapour due to spin-exchange collisions is given. Then the influence of spin-exchange collisions on transversal relaxation rates and Zeeman frequency shifts due to sudden collisions (collisions with buffer gas or coated walls of the cell) is considered. The evolution equation of Zeeman coherences in the case when both relaxation processes are active is solved for F=1. (author)