Does the standard TLS model fail to explain the experimental data on the long-lived stimulated photon echo in amorphous solids?

The formulae of dynamical spectral diffusion (SD) theory are used to treat the experimental data on the long-lived stimulated photon echo in amorphous solids. This theory is based on the standard two-level system model proposed by Anderson, Halperin, Varma and Phillips. Dynamical SD theory removes all the contradictions existing between the experimental data and stochastic SD theory for a long-lived stimulated photon echo.