Sm, Eu, and La) are investigated in the orthorhombic (HTC) and tetragonal (non-HTC) phases using EPR method. For both phases EPR signals associated with G d ions are detected. In the tetragonal phase a strong temperature dependence of the intensities of this line is observed. These characteristics can be ascribed to the skin effect. A small polaron model is proposed to interpret the conduction mechanism of the tetragonal phase (semiconducting) of these samples.Mittel EPR werden die Materialien Gd,,,Re,,,Ba,Cu30,-, (Re = Y, Sm, En und La) in der rhombischen (HTC) und tetragonalen (Nicht-HTC)-Phase untersucht. Fur beide Phasen werden mit Gd-Ionen verbundene Signale nachgewiesen. In der tetragonalen Phase wird eine starke Temperaturabhangigkeit der Intensitat dieser Linie beobachtet. Diese Charakteristiken lassen sich dem Skin-Effekt zuschreiben. Ein Model1 kleiner Polaronen wird vorgeschlagen, um den Leitungsmechanismus der tetragonalen Phase (halbleitend) dieser Proben zu interpretieren.
The case of spontaneous radiation of channeled ultrarelativistic particles is considered when the dipolarity condition is not satisfied. The change of the particle longitudinal velocity affecting the maximum radiation frequency is included. The angular and frequency characteristics of the radiation for superhigh energies are studied for the first time. It is shown that there is an optimum energy at which the radiation density is maximum. The influence of the angle a t which electrons enter a crystal and of the beam divergence on the radiation is investigated. The problem of quasichanneled particle radiation and also the radiation in axis-plane transitions are considered. sacmq II ~a n y s e~n e n p~ iiepexonax ocb-mociiomb.
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