Transient luminescence line shapes for Mn²⁺ ions in ZnS nanocrystals

Recent time-resolved luminescence spectra reported by Yu et al. from ZnS:Mn nanocrystals embedded in a polymer matrix showed the presence of two emission bands that merge into a single band as time passed following an intense laser excitation pulse. We have calculated the bandshapes as a function of time assuming a nonequilibrium initial distribution for the excited vibrational states. Our calculated bandshapes fit quite well to those observed experimentally and support the explanation given by Yu et al. This would seem to be an ideal system in which to study the approach to thermal equilibrium in nanocrystals.