Electron-phonon interactions in insulating nanoparticles:: Eu2O3

The temperature and particle size dependencies of the linewidth of spectral holes burned in the F-7(0)-->D-5(0) transition of Eu3+ ions in Eu2O3 are calculated and compared with experiment. The power-low temperature behavior similar to T-7, well-known experimentally and theoretically for the bulk, is observed to be strongly weakened to similar to T-3 for the nanoparticles. A calculation is performed that assumes a two-phonon Raman-scattering mechanism involving the discrete phonon modes of a homogeneous nanoparticle with stress-free boundary conditions. The experimental results are successfully described assuming that the phonon modes broaden with frequency as similar to omega(2). A quantitative comparison of the calculations with experiment allows the determination of the linewidth of the phonon resonances of the nanoparticles. The calculations predict that the size dependence of the hole linewidth is similar to D-2.5, in close agreement with experiment.