X-ray excitation fluorescence spectra of the Eu2+-stabilized VK center in alkaline-earth fluoride mixed-crystal systems

被引:23
作者
Kawano, K [1 ]
Ohya, T [1 ]
Tsurumi, T [1 ]
Katoh, K [1 ]
Nakata, R [1 ]
机构
[1] Univ Electrocommun, Dept Elect Engn, Tokyo 1828585, Japan
关键词
D O I
10.1103/PhysRevB.60.11984
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
X-ray excitation fluorescence spectra were investigated for MF2:Eu (M = Ca, Sr, and Ba) and their mixedcrystal systems, Ca1-xSrxF2 and Sr1-xBaxF2 with the same fluorite structure. The UV recombination fluorescence band of the V-K center associated with blue emission due to the S-d transition of Eu2+ ions was observed with changing mixture ratios x at room temperature. Two sets of weak spectra due to f-f transitions of Eu3+ ions also appeared in the 500-600-nm wavelength region. The peak wavelengths and the integrated intensities of the observed fluorescence were investigated as a function of the Eu concentration as well as the mixture ratio. For the blue emission of Eu2+, pulsed x-ray excitation resulted in shorter lifetimes (500-800 ns) than optical excitation, suggesting energy transfers between the excited states of V-K centers and Eu2+. A kinemati cal fluorescence mechanism was proposed, taking into account the formation of a close pair of a hopping V-K center and an immobile Eu2+ ion followed by an energy transfer from the former to the latter. Based on the calculated fluorescence decay curves best fitted to the response curves by x-ray pulse excitation, the energy transfer rates from V-K centers to Eu2+ were estimated. [S0163-1829(99)10941-X].
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页码:11984 / 11992
页数:9
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