A series of compounds were discovered which have the generalized formula R22+R4+R25+Og.Examination of single crystals of Pb~ZrP209 showed it to have hexagonal symmetry with aH ~ 10.08fl~ and CH ~ 23.29A. Five of the seven compounds studied (Ba2ZrP,209, Sr2ZrP209, Pb2TiP209, Ba2ZrAs2Og, and PbuZrAs2Og) were isostructural with PbuZrP2Og, and the seventh, Sr2ZrAs2Og, had optical properties closely related to the group. With the exception of Pb2TiP2Og, all of the compounds exhibited a broad band blue fluorescence, with an intensity maximum near 4800A, when excited by 25377~ radiation. By contrast, Pb2TiP.209 showed a weak orange fluorescence, more easily excited by 3650A radiation. Emission, absorption, and excitation data are presented.
A great variety of compounds occur in nature or have been synthesized in the laboratory that crystallize with the apatite structure. We have investigated a number of the apatites and found them to be excellent laser hosts for neodymium and holmium. The apatites described in this paper were grown using the Czochralski method, have low optical losses in the pump and emission spectral regions for neodymium and holmium, and the hosts have been developed to readily accept large concentrations of doping ions. This paper describes the crystal growth, physical properties, spectroscopy, and laser performance of this family of new laser materials.
The optical properties of powders are determined for the case of particles, large compared with the wave-length of light. The solution for the diffusion of light in a quasi-infinitely thick powder is applied to relate certain measurements obtained on powders with the corresponding properties of the bulk material.
In Part I, the diffuse reflectance R of a powder is first derived in general form in terms of the parameters of the individual particle, taking into account both internal and external scattering. Parameters are then obtained for a model for randomly shaped particles, and used to relate the diffuse reflectance to the optical absorption coefficient, the index of refraction, and the particle diameter. The relationship is compared with measurements on materials of different refractive indices.
Part II deals with applications to luminescent powders, the calculation of the characteristics of emission in the presence of optical absorption, and the calculation of cascade transfer yields.
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