钡钇氟化物中Eu^(2+)离子的激发光谱和发射光谱

EXCITATION AND EMISSION SPECTRA OF Eu^(2+) IN BARIUM YTTRIUM FLUORIDE

在298和77K下分别研究BaYF_5(BaF_2·YF_3)中Eu^(2+)的激发和发射光谱。Eu^(2+)的发射光谱中,除了一个属5d—4f跃迁的宽发射带外,还有一组~6P_J→~8S_(7/2)的4f—4f跃迁窄谱线发射。它们的发射强度与Eu^(2+)的浓度和温度有关。由於Eu^(2+)从4f^7基态跃迁到4f^65d^1态产生两个宽的激发带,4f^65d(eS)和4f^65d(t_(2g))。实验证实,Eu^(2+)的~6P_J→~8S_(7/2)的窄谱线发射主要来自高能级的t_(2g)激发能弛豫的结果。

Divalent europium ions shew strong absorption bands in the visible and near ultraviolet spectral ragions. Since Hoffman and Hewes observed in some fluorides sharp lines corresponding to 4f-4f transitions of Eu2+ ions, great attention has been paid to the study of its spectral properties . In contrast to where only the broad 5d-4f emission band was observed in BaYF5:Eu2 + , we report in this paper both the broad band and the narrow lines from Eu2+ in BaYF5. Moreover, their excitation and emission spectra have been investigated at 298K and 77K.Fig. 1a,1b and 1c show the emission spectra as a function of Eu2+ concentration under 260nm UV excitation at 298K and 77K. The emission spectra consist of a broad band corresponding to the 5d-4f transition and narrow line associated with the 6P7-8S7/2 (4f-4f) transition of the Eu2+ ion. The intensities of both the transitions depend on the Eu2+ concentration and temperature. There are two bread bands. 4f65d(eg) and 4f65d(t2g)in excitation spectra. The activators, Eu2+, are excited by UV from 4f7 ground state to 4f65d state then luminesce.The radiationless relaxation cf the higher 5d state (t2g) gives rise to the 6Pj-8S7/2 narrow line emission.