Aggregate centers in reactor irradiated single crystal a-,41,0, are investigated using the thermochemical and photochemical methods. Isochronal and isothermal annealing5 of the bands at 302, 356, 450, and 570 nm are performed in detail to study the thermal stability and to obtain the activation energy ( E ) for the decay of their corresponding centers. After X-ray irradiation at room temperature, a new band at 384 n m appears in the crystal irradiated previously by reactor radiation. From the thermochemical and photochemical properties as well ns from correlations of these several bands, i t is proposed tentatively that the 450 and 570 nm bands are attributed to the Fi type center, and the 302 nm band to the F, center.Mittels thermochemischer und photochemischer Methoden werden Aggregatzentren in Reaktorbestrahlten cc-Al,O,-Einkristallen untersucht. Isochrone und isotherme Temperungen der Banden bei 302, 356,450 und 570 nm werden durchgefiihrt, um die thermische Stabilitat zu untersuchen und die Aktivierungsenergie ( E ) fur den Zerfall ihrer entsprechenden Zentren zu erhnlten. Xach Rontgenbestrahlung bei Zimmertemperatur tritt eine neue Bande bei 384 nm in den vorher im Reaktor bestrahlten Kristallen auf. Aus den thermochemischen und photochemischen Eigenschaften sowie aus den Korrelationen dieser verschiedenen Canden wird vorlaufig angenommen, daB die 450 und 570 nm-Randen dem FS-Zentrum und die 302 nm-Bande dem F,-Zentrum zugeordnet sind.

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The production of point defects by neutron irradiation and thermal decay in sintered AIN polycrystal are investigated. The absorption band at 370 nm is observed after reactor neutron irradiation to a dose of 1016 n/cm2 (E>0.1 MeV). The defect corresponding to the band is tentatively assigned as an F-type center from the optical absorption and electron spin resonance.

Abstract-We investigated thermoluminescence of silicates that are of interest in the interstellar and circumstellar medium after irradiation by y-rays and fast neutrons. The silicates are forsterite, orthoenstatite, olivine, quartz, and crystalline silicon. The irradiated enstatite shows weak and broad peaks at 545 and 760 nm. In contrast, irradiated bulk and powder samples offorsterite show strong and broad peaks at 640-660 nm. Although thermoluminescence of bulk forsterite is very similar to the extended red emission (ERE) of the Red Rectangle nebula, irradiated powdered forsterite did not reveal any sharp emission features over the broad band. Further, we investigated the possibility of thermoluminescence of crystalline silicon and found that luminescence scarcely appears. It is emphasized that the prominent carrier of ERE is forsterite and fused quartz.

Neutron-Irradiated AlN was investigated using electron paramagnetic resonance. The broad spectrum arising from the electrons trapped in N3- vacancies can be explained by the hyperfine interaction with the surrounding 27Al nuclei. The obtained parameters, the g-value and the hyperfine constant are g=2.007±0.001 and A=(10.9±0.5)×10-4 cm-1, respectively.