| Budget Amount *help |
¥6,500,000 (Direct Cost: ¥6,500,000)
Fiscal Year 1987: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1986: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1985: ¥4,500,000 (Direct Cost: ¥4,500,000)
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| Research Abstract |
The photo-luminescences of natural zircons are originated from three main luminescent centers. 1. Type I consists of line spectra originated from REE such as Dy^<3+>, Eu^<3+>, Tm^<3+>. 2. Type II consists of broad bands originating from radiation centers due to the <alpha>-decay effect of radioactive elements of U and Th. This was ascertained successfully in the case of Ca-doped zircons, in which <alpha>-decay was induced by the nuclear reaction of ^<40>Ca(n,<alpha>)^<37>Ar. The experiment was the first success of making artificially the type II. The centers consist of several radicals in the zircon, which were also detected by ESR. The transitions depend on the crystallographic direction. However, this artificial type II disappeared for several months if REE does not coexist. The intensity of the type II of natural zircons is proportional to the geologic age of the zircon, but it is not affected by the nuclear fission of U and <gamma>-ray irradiation. Also, the luminescence is easily diminished by heat treatment at temperatures higher than 700゜C, and can be restored after several days at room temperature. 39 The type III is vary rare in occurence, and consists of relatively simple bands. This is attributed to three types of activators. (1) U and P with electron-hole centers, (2) transition elements Mn, Ni and V with 3d electrons, and (3) Ca, Ba, Zn and Sc with electron-hole centers. These activators are strongly affected by the coexisting P sensitizer. The latter two types of activators in the type III could not be distinguished in natural zircons.
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