Radiative and non‐radiative transitions of electrons in local centers involving hot phonons

A theory of multi‐quantum radiative and non‐radiative (NRT) transitions in local centers under a high power laser radiation is presented. A model of local center having local phonons (LP) is used. When the interaction between the LP and the thermostat (crystal vibrations) is weak, the quantum transitions of electrons involving hot phonons result in a heating of the LP to an effective temperature T_v well above the equilibrium one. An explicit expression for T_v based on the method of nonequilibrium statistical operator is derived. The latter is determined self‐consistently in terms of quantum correlation functions, which contain standard multiphonon structures. This allows the shape function of absorption and NRT involving hot phonons to be found. In particular one displays the LP heating by means of a sharp asymmetry (flattening) of the absorption band and an essential activation of NRT.