What knowledge about lattice oscillators can we obtain from the optical band shape of a recombination center?

The electron lattice interaction is visible in electron-hole recombination emission as a series of emission lines shifted downwards from the zero phonon energy E₀ by a succession interval hv_ph. It is usually assumed that the band shape is Pekarian, i.e. the replica intensities I_n are Poisson distributed I_n= e^-SCⁿ/n!. Here S is the Pekar-Huang-Rhys factor, quantifying the lattice ion displacement resulting from the electronic charge distribution change inherent in the recombination.

We argue (1) that the standard assumption of a Poisson distribution is, in fact, an over-simplification, and (2) that the observation of a non-Poissonian series of replicas should most naturally be accounted for by a change of lattice ion coupling constants, due to the electronic transition. This would seem to lead to physically interesting information about local lattice dynamics and about the local electric charge distribution. The theses (1) and (2) are also related to experimental results.