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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Anomalous Trapped Exciton and d?f Emission in Sr4Al14O_25:Eu~(2+)
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Anomalous Trapped Exciton and d?f Emission in Sr4Al14O_25:Eu~(2+)

机译：Sr4Al14O_25：Eu〜（2+）中的异常陷阱激子和d？f发射

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摘要

The photoluminescence and time-resolved emission for Eu~(2+) in Sr4Al14O_25 has been investigated in the temperature range 4 to 500 K. The Eu~(2+) emission changes in a peculiar way with temperature. At low temperature two emission bands are observed at 490 and 425 nm, which are attributed to emission from Eu~(2+) on the 7- and 10-coordinated sites. Upon raising the temperature, an unexpectedly large blue shift to 400 nm is observed for the 425 nm emission band. To explain these observations, the 400 and 425 nm emission bands are assigned to d?f and trapped exciton emission, for Eu~(2+) on the 10-coordinated site. The trapped exciton emission is characterized by a short (0.5 μs) decay time. The temperature dependence of the emission is explained by a configurational coordinate diagram in which the Eu~(2+) trapped exciton state is at a slightly lower energy than the lowest energy 4f~65d state. Upon raising the temperature, the 4f~65d state is thermally populated and emission from this state is observed, and because of the smaller lattice relaxation (smaller Stokes shift), a large blue shift from 425 to 400 nm is observed.
机译：研究了Sr4Al14O_25中Eu〜（2+）在4〜500 K温度范围内的光致发光和时间分辨发射。Eu〜（2+）的发射随温度的变化而变化。在低温下，在490和425 nm处观察到两个发射带，这归因于Eu〜（2+）在7和10位配位的位点上的发射。升高温度后，对于425 nm的发射带，观察到出乎意料的大蓝移到400 nm。为了解释这些观察结果，在10坐标位上，对于Eu〜（2+），将400和425 nm发射带分配给d？f和捕获的激子发射。捕获的激子发射的特点是衰减时间短（0.5μs）。发射的温度依赖性由结构坐标图解释，其中Eu〜（2+）俘获的激子态的能量略低于最低能量的4f〜65d态。升高温度时，会热填充4f〜65d状态，并且观察到从该状态发出的光，并且由于晶格弛豫较小（斯托克斯位移较小），因此观察到从425 nm到400 nm的大蓝移。

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