In the Optical Bloch Equations (https://en.wikipedia.org/wiki/Maxwell%E2%80%93Bloch_equations) it is imposed that the populations decay at a rate γ, and that the coherences decay at γ2.
I can see why the populations should decay at γ (i.e. via Wigner-Weiskoppf theory) but how do we arrive at γ2 for the coherences?
My motivation in asking this question is in trying to extend the OBE's to a three-level Vee system, where is is not obvious what decay rate to assign to the excited state coherence terms (i.e. ρe1e2).
This post imported from StackExchange Physics at 2016-11-24 08:30 (UTC), posted by SE-user user2640461