Browsing by Author "Yuan, H. B."

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    Dependence of fluorescence lifetimes of Y2O3 : Eu3+ nanoparticles on the surrounding medium
    Meltzer, R. S.; Feofilov, S. P.; Tissue, B.; Yuan, H. B. (American Physical Society, 1999-11)
    The radiative lifetime, tau(R), of the D-5(0) metastable excited state of Eu3+ ions in nanocrystalline monoclinic Y2O3 samples is about four times longer than that in the micron size powder of the same material. The Eu3+ radiative lifetime was measured in nanocrystals surrounded with air as well as those immersed in different liquids. It is shown that the radiative lifetime changes with the index of refraction of the immersion medium and provides a unique test of the standard formula relating tau(R) and the oscillator strength. The magnitude of the effect is determined by the "filling factor" (the fraction of the sample volume occupied by nanocrystals) which can therefore be determined. [S0163-1829(99)51144-2].
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    Evidence for long-range interactions between rare-earth impurity ions in nanocrystals embedded in amorphous matrices with the two-level systems of the matrix
    Meltzer, R. S.; Yen, W. M.; Zheng, H. R.; Feofilov, S. P.; Dejneka, M. J.; Tissue, B. M.; Yuan, H. B. (American Physical Society, 2001-09)
    The low-temperature homogeneous broadening of the electronic transitions of Eu3+ and Pr3+ rare-earth impurity ions in Y2O3 and LaF3 nanocrystals embedded into amorphous materials (polymer and oxyfluoride glass ceramics) was studied with hole-burning and fluorescence line narrowing techniques. It is-shown that the homogeneous linewidth is determined by the interaction of the impurity ions contained in the nanocrystals with the two-level systems (TLS's) of the surrounding glass matrix. A comparison of the experiments with a calculation provides direct evidence for the long-range nature of the interaction with the TLS's.