Femtosecond time-resolved spectroscopy of self-trapping processes of holes and electron-hole pairs in alkali bromide crystals.
Femtosecond time-resolved spectroscopy of self-trapping processes of holes and electron-hole pairs in alkali bromide crystals.
复制标题
碱金属溴化物晶体中空穴和电子空穴对自捕获过程的飞秒时间分辨光谱。
DOI：
10.1103/physrevb.54.15109
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Tanimura
中科院分区：
文献类型：
--
作者：
Sugiyama;Fujiwara;Suzuki;Tanimura
在飞秒时间范围内，在6 - 300 K的温度范围内，研究了碱金属溴化物晶体中由带隙激发产生的空穴和电子-空穴（e-h）对的晶格弛豫动力学。在溴化钾包括电子捕获杂质，在那里发生的空穴弛豫没有与电子相互作用，它被发现的自陷空穴的形式的卤素分子离子，的V K中心，是通过一个短暂的局部空穴中心作为前体产生。该瞬态空穴中心在可见光区显示出宽的光吸收带，在273 K下的寿命约为3 ps。结果发现，在纯KBr和RbBr中，（e-h）对的弛豫过程有两个不同的阶段。在第一阶段，激发后6 ps内终止，瞬态空穴中心产生的掺杂试样中，和它们与电子的相互作用的结果在快速形成的Frenkel对组成的F中心，卤素空位捕获电子，和H中心，间隙卤素原子。此外，在第一阶段中形成中间态，并且根据其光谱特征将该状态归因于具有中心配置的自陷激子（STE）。弛豫的第二阶段，在低温下持续超过100 ps，包括在第一阶段中形成的中心STE的偏离中心弛豫成Frenkel对和具有偏离中心配置的STE。弛豫路径和特性，包括温度依赖性进行了讨论，根据实验结果和分析的速率方程模型。
The dynamics of the lattice relaxation of holes and electron-hole (e− h) pairs generated by the band-gap excitation in alkali bromide crystals has been studied in femtosecond time regime at temperature range from 6 to 300 K. In KBr including electron-trapping impurities, where relaxation of holes takes place without interaction with electrons, it is found that the self-trapped hole in the form of a halogen-molecular ion, the V K center, is generated via a transient localized-hole center as a precursor. This transient hole center shows broad optical absorption bands in the visible region and has a lifetime of about 3 ps at 273 K. It is found that in pure KBr and RbBr, the relaxation processes of (e− h) pairs have two distinct stages. In the first stage, which terminates within 6 ps after excitation, the transient hole centers are generated as in doped specimens, and their interaction with electrons results in the fast formation of a Frenkel pair consisting of an F center, a halogen vacancy trapping an electron, and an H center, an interstitial halogen atom. Also, an intermediate state is formed in the first stage, and the state is ascribed to the self-trapped exciton (STE) with the on-center configuration on the basis of its spectroscopic features. The second stage of the relaxation, which lasts over 100 ps at low temperatures, comprises the off-center relaxation of the on-center STE formed in the first stage into Frenkel pairs and STE's with the off-center configuration. Relaxation pathways and characteristics including temperature dependence are discussed based on the experimental results and their analysis in terms of a rate-equation model.