Pump probe spectroscopy as linear process away from equilibrium

by qu_bio
Tags: linear, probe, process, pump, spectroscopy
 P: 2 Greetings everyone, I have recently been trying to generate some theoretical pump probe spectroscopy data. The typical way to do this is via third order time dependent perturbation theory and applying phase matching approximations / Rotating wave approx etc etc. There is however, no reason one cannot simply consider the state of the system after interacting with the first (strong) pump pulse and then looking at linear absorption in the non-equilibrium system $\rho_{eq} \to \rho_{neq}(t)$. Naturally this has a few issues with the system actually evolving while the probe is interacting, but this pulse is considered short so it isn't a problem. I was wondering if anyone can suggest any papers / textbooks that work through this formalism for absorption spectroscopy?