BaFCl:Sm晶体的光激励发光和热释发光

PHOTO- AND THERMO-STIMULATED LUMINESCENCE OF BaFCl:Sm

研究了在X射线辐照及光激励发光和热释发光过程中,BaFCl:Sm晶体中钐离子的价态变化和F色心的产生和湮灭过程。提出了如下的BaFCl:sm晶体的光激励发光和热释发光过程:在X射线辐照下,晶体中产生F色心,同时一部分Sm^(3+)俘获空穴形成Sm^(4+),还有少量的Sm^(3+)得到电子形成Sm^(2+)。在光激励发光和热释发光过程中,从F色心中电离出来的电子与Sm^(4+)复合转变成Sm^(3+)激发态,随后发出Sm^(3+)的特征光辐射。同时在热释发光中,Sm^(2+)还可以与空穴复合,转变成Sm^(3+)的激发态,也发出Sm^(3+)的光辐射。

The valence changes of doped samarium and the creation as well as the annihilation of F-centers in the processes of thermostimulated luminescence (TSL) and photostimulated luminescence (PSL) of BaFCl:Sm crystal have been studied.As being irradiated by X-ray; a large number of electron-hole pairs are created in the crystal. Most of the electrons may be trapped at the anion vacancies, producing F-centers. The doped samarium ions, which existed mostly intrivalent state (Sm^(3+)), may capture the holes and convert themselves to tetravalent state. So that part of the incident X-ray energy are stored in this nonequilibrium system. On optical and thermal stimulation the stored energy can be liberated as a characteristic emission of trivalent samarium ion. This emission originates from the recombination of the F-center electrons with tetravalent samarium ions, i.e. the F-center electrons may be excited to the conduction band by optical or thermal stimulation and then recombine with tetravalent samarium ions.This recombination makes the samarium ions to be in situ reduced to the excited state of Sm^(3+) and then gives rise to the characteristic emission of Sm^(3+).On the other hand, during X-irradiation a few electrons can be trapped at the sites of trivalent samarium ions and reduce them to divalent state. But the formation of divalent samarium on X-irradiation is very small as compared with that of F-centers and so their influence on the PSL and TL can be neglceted.