a) X-ray luminescence spectra of single crystals of composition 0.9 Zr0,-0.1 Y20, and 0.9 Zr0,-0.09 Y20,-0.01 Ln,O, (Ln = Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb) are obtained at room temperature. A wide structureless band of luminescence with a maximum a t about 500nm is found. Thermostimulated luminescence is investigated on the same samples. Irradiation of the crystals by X-rays is carried o u t at room temperature. The glow curves contain two or three peaks each depending on the doping component. The nature of the main peaks is discussed.

YAlO, crystals have been prepared with small percentages of different rare earths substituted for yttrium. The absorption and luminescence spectra of the samples activated with Dy, Ho, Er, Tm, and Yb have been measured a t 77 K. An analysis of these spectra gave the positions of many of the crystalline Stark levels. Stimulated emission has been observed from Ho3+, Er3+, and Tm3+ ions in crystals of YAlO,. Es wurden YAl0,-Kristalle mit geringen Dotierungen Seltener Erden, deren Einbau auf Yttrium-Plltze erfolgte, gezuchtet, Die Absorptions-und Lumineszenz-Spektren der mit Dy, Ho, Er, Tm und Yb dotierten Proben wurden bei 77 K gemessen. Die Analyse dieser Spektren ergab die Lage einer Vielzahl der Stark-Niveaus. Es werden Angaben zur stimulierten Emission von Ho3+, Er3+ und Tm3+ in YAIO, gemacht.

Absorption spectra of LiNbO3 crystals containing ions of the iron group and grown by the Czochralski method have been studied. Observed transitions are compared with transitions between the levels of d2, d3, d4, d5, d6, d7 configurations in the field of cubic symmetry. The magnitudes of the parameters of Coulomb interaction B and C and the parameter of the internal crystal field, Dq, are given, which lead to the best agreement between experimental and theoretical values.

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