We briefly review the areas of luminescence line-broadening and energy transfer in amorphous solids, with particular emphasis on non-resonant phonon-assisted energy transfer between like ions. The laser-induced fluorescence line-narrowing technique is discussed, and the importance of resonant excitation-detection is emphasized. We illustrate the discussion with several examples from our recent work. A two-phonon Raman scattering propess is shown to be the dominant source of homogeneous thermal line-broadening of the 5D0→ 7F0 fluorescence line of Eu 3+ in a silicate glass, over the temperature range 200-350 K. We have further shown that the scattering efficiency is site-dependent, correlating with the static crystal field strength. Our results on spectral diffusion (energy transfer between like ions having different transition energies) indicate an electric dipole-dipole coupling mechanism between Eu3+ ions in a phosphate glass. The phonon involvement was determined to be an intersite two-phonon Raman process, with one-phonon action at each of the two coupled ion sites.
|