Nonradiative DKR processes: revisiting the theory. I. Unimode model

We are revisiting the efficiency problem of DKR nonradiative transitions at local electronic centers in polarizable solids. Following a brief survey, we formulate the general rate equations thereby defining the microscopic parameters controlling the nonradiative deexcitation. We also reproduce the quantum mechanical expressions for the energy conserving "horizontal transfer rates" to compare with the "verical transition rates" at various vibronic energy levels.