INFLUENCE OF CHARGE COMPENSATION ON UV-EXCITATION OF RARE-EARTH FLUORESCENCE
HARRY DIAMOND LABS ADELPHI MD
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Excitation spectra for the fluorescence transitions of Tb3, Eu3 , and Dy3 were obtained at room temperature on single crystals of the tungstates and molybdates of Ca, Sr, Pb, and Cd, having the Scheelite structure, and on terbium-doped crystals of CaF2 and SrF2. Rare-earth concentrations were nominally one atomic percent and charge compensation was provided by vacancy formation or interstitials, by substitution in cation-sites or by anionic substitutions. Strong UV-excitation bands were found for Tb- and Eu-doped crystals and weaker bands for Dy-doped matrices. The bands generally occur near the host-lattice absorption-edge but their intensities and energy positions are strongly influenced by the charge-compensating defects near the active ion. The long wavelength peaks of the bands occur at energies coinciding with 4f-level positions of the rare-earth ions, suggesting a strong perturbation of 4f-levels by charge transfer states. The short-wavelength regions of the excitation bands are ascribed to exchange transfer from UV-absorbing groups.
- Lasers and Masers
- Atomic and Molecular Physics and Spectroscopy
- Solid State Physics