We investigate the electron population dynamics in an ensemble of nearly isolated insulating nanoparticles, each nanoparticle modeled as an electronic two-level system coupled to a single vibrational mode. We find that at short times the ensemble-averaged excited-state population oscillates but has a decaying envelope. At long times, the oscillations become purely sinusoidal about a “plateau” population, with a frequency determined by the electron-phonon interaction strength and with an envelope that decays algebraically as $t^{-1/2}.$ We use this theory to predict electron-phonon dynamics in an ensemble of ${\mathrm{Y}}_2{\mathrm{O}}_3:{\mathrm{Eu}}^{3+}$ nanoparticles.

• Received 18 January 2001

DOI:https://doi.org/10.1103/PhysRevB.64.115412