Search

Mesure des parametres de transition supraconductrice de ceramiques et de monocristaux supraconducteurs a T c elevee durant et juste apres irradiation a 80 K par des sources de Co 60 de rayonnement γ de differentes intensites

Self-trapped hole (STH) and self-trapped exciton (STE) states which are formed in Y3Al5O12, Y2SiO5, and TR2Si2O7 crystals under γ-irradiation in the temperature interval of 77 to 200 K are investigated. The STH is shown to be molecular O, absorbing at 1.6 eV (for Y3Al5O12) and at 1.65 eV (for Y2SiO5) and causing the eleven-component EPR signal; the corresponding STE emits at 3.9 and 3.6 eV. In metal-doped crystals the exciton and hole delocalization lead to a decreasing of the emission energy, to a short-wave shift of the absorption band, and to the growth of the anneal temperature. At the self-localization temperature excitons are proved to migrate by jump diffusion and to transfer energy to the impurity ions exciting their emission. [Russian Text Ignore.]

On etudie les caracteristiques optiques de guides d'onde a fibres optiques (FOW) plastiques, a l'interface silica-polymere. On conclut que les changements des proprietes optiques interviennent dans la couche superficielle du FOW, sous charge mecanique et irradiation γ

The growth of LiYO2 and its structure are discussed. The absorption and luminescence spectra of Nd3+ in LiYO2 monocrystals are recorded at 4.2, 50, 77, and 300 K in the region from 250 to 2500 nm. The Nd3+ ion energy level diagram is constructed on the basis of the spectral data. Theoretical calculations of the intrinsic crystal field parameters (on the “Minsk-22” computer) make possible to draw some conclusions about the coordination and the symmetry of the activator center. The calculated Nd3+ ion energy levels are in good agreement with the experimental ones. The colour center formation under γ-irradiation is also investigated. Es werden das Wachstum von LiYO2 und seine Struktur diskutiert. Die Absorptions- und Lumineszenzspektren von Nd3+ in LiYO2-Einkristallen werden bei 4,2; 50; 77 und 300 K im Bereich von 250 bis 2500 nm aufgenommen. Auf der Grundlage der spektralen Daten wird das Energieniveaudiagramm des Nd3+-Ions aufgestellt. Theoretische Rechnungen der inneren Kristallfeldparameter (auf dem “Minsk-22”-Computer) ermoglichen Schlusfolgerungen uber die Koordination und Symmetrie der Aktivatorzentren. Die berechneten Energieniveaus der Nd3+-Ionen befinden sich in guter Ubereinstimmung mit experimentellen Werten. Es wird auch die Farbzentrenbildung bei γ-Strahlung untersucht.