TIME-RESOLVED SPECTROSCOPY ON ULTRAFAST NONRADIATIVE RELAXATION OF TRANSITION METAL IONS IN SOLIDS

固体中过渡金属离子超快非辐射弛豫的时间分辨光谱

基本信息

批准号：
02640247
负责人：
SUZUKI Yoshiro
金额：
$ 1.09万
依托单位：
TOHOKU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

Trivalent cerium impurities (Ce^<3+>) in YAG crystals were selected as a model system to investigate the de-excitation mechanism of d electrons in solids. The 4f electrons at the ground state were pumped to the second-lowest 5d state (5d_b) by UV laser pulses. Then, observed were the growths of the yellow-green (YG) emission from the lowest 5d state (5d_a) by a streak camera, as well as the growths of the excited state absorption (ESA) from the 5d_a to higher excited states by a pump & prove method.Each measurement gave consistent results. The growth times (tau) at temperatures below 80K were as long as 50ps. The tau decreased above 80K to be less than 5ps at 300K. The constant tau below 80K was interpreted from a tunneling process from 5d_b to 5d_a, while the decreasing tau above 80K was from a thermally-activated process. It follows that the nonradiative transition (NRT) between 5d states occurs not dynamically, but statically after completing a thermal equilibrium in the initial 5d state.The above results predict the existence of UV emission from the metastable 5d_b state to the 4f ground state. The UV emission was successfully detected at 350 to 400nm. Agreement of the decay time of the UV emission with the tau of the ESA and YG emission supports the static mechanism of the NRT for 5d electrons.To apply the time-resolved spectroscopy to a variety of d electron systems, extension of the pumping wavelengths and improvement of the pumping methods were required. As the former examination, F^+_ centers were shown to be available for an IR pulse source, while, as the latter, a method of time-delayed double excitation was demonstrated by making use of two pulse lasers.

选择YAG晶体中的三价石杂质（CE^<3+>）作为模型系统，以研究固体中D电子的去激发机理。紫外线激光脉冲将基态的4F电子泵送至第二高的5D状态（5D_B）。然后，观察到的是通过条纹摄像机从最低5D状态（5D_A）发射的黄绿（Yg）发射的生长，以及通过泵和Prove方法从5D_A到更高激发态的激发状态吸收（ESA）的生长。每个测量结果都得出了一致的结果。低于80K的温度下的生长时间（TAU）长达50ps。 tau在300k时降低了80k以上的5ps。从5D_B到5D_A的隧道过程解释了低于80k的常数TAU，而高于80K的降低的TAU来自热激活过程。因此，在最初的5D状态下完成热平衡后，5D状态之间的非放射性转变（NRT）不是动态的。在350至400nm时成功检测到紫外线排放。与ESA和YG发射的TAU的紫外线发射时间的衰减时间的一致性支持5D电子NRT的静态机理。将时间分辨的光谱应用于多种D电子系统，泵送波长的扩展以及泵送方法的改进。作为前检查时，f^+_中心被证明可用于IR脉冲源，而作为后者，通过使用两个脉冲激光器证明了一种时间延迟的双激发方法。