When two spin-polarized atoms in their ground state experience a spin-exchange collision, the total spin of the atoms is preserved yet the orientation of the individual spins may change.
are oppositely polarized, a spin-exchange collision reverses the spins:[2] In a typical vapor of alkali metal atoms, spin-exchange collisions are the dominant type of interaction between atoms.
Thus, spin-exchange collisions between alkali metal atoms can change the hyperfine state of the atoms while preserving total angular momentum of the colliding pair.
As a result, spin-exchange collisions cause decoherence in ensembles of polarized atoms precessing in the presence of a magnetic field.
The time between spin-exchange collisions for a vapor of alkali metal atoms is where the spin exchange cross section for alkali metals such as K, Rb, and Cs is[3] and where