摘要
实验研究了从体材料到纳米晶(NCs)系统中涉及大能隙(5 800 cm-1)的多声子弛豫(MR)。在MR非线性理论框架下,用单频近似声子谱分析了β-Na Gd F4∶Tb3+NCs中Tb3+:5D3→5D4的MR速率与温度的关系。在12~312 K范围内,实验数据与理论曲线符合得很好。结果表明,MR的产生主要是能量较大的光学声子起作用。在Rayleigh极限下,假设Tb3+发射体位于一个纳米球的中心,使用Green张量方法计算了自发衰减速率Гrad。在纳米球内没有发现局域态密度(LDOS)的明显改变。然而,当R<35 nm时,在Chew理论的基础上获得在球外LDOS的一个新的高斯分布。
This paper reports the experimental study of multiphonon relaxation( MR) involving a large energy gap( 5 800 cm-1) crossover from bulk to nanocrystal( NC) system. The temperature dependence of MR rate for5D3→5D4of Tb3 +in β-Na Gd F4∶ Tb3 +NCs was analyzed in a singlefrequency approximation of phonon spectrum in the framework of the nonlinear theory of MR. The experimental data well agree with the theoretical curves within the range of 12 K to 312 K. It is shown that MR occurs predominantly via high-energy optical phonons. In Rayleigh limit,assuming that the Tb3 +emitter was located at the center of a nanosphere,the spontaneous decay rate Γradwas calculated using Green tensor approach. No significant variation in the local density of states( LDOS) was found inside the nanospheres. However,for R < 35 nm,a new Gaussian distribution of LDOS was obtained based on Chew's theory outside the nanospheres.
出处
《发光学报》
EI
CAS
CSCD
北大核心
2014年第12期1443-1448,共6页
Chinese Journal of Luminescence
基金
国家自然科学基金(61077025)资助项目
