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ELEMENTARY RELAXATION PROCESSES IN PHOTO-EXCITED STATES IN THE WEAK ELECTRON-LATTICE COUPLING SYSTEM

弱电子晶格耦合系统中光激发态的基本弛豫过程

基本信息

批准号：
06452047
负责人：
NAKAMURA Kaizo
金额：
$ 4.93万
依托单位：
OKAYAMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06452047/
关键词：
EXCITON POLARITON RELAXATION PROCESSES ZINC DIPHOSPHIDE ELECTRON-LATTICE INTERACTION WEAK COUPLING SYSTEM RESONASNCE RAMAN INTER-SYSTEM CROSSING MAGNETIC FIELD EFFECTS 共鳴ラマン散乱

项目摘要

We have investigated the resonant secondary emission from the monoclinic zinc diphosphide beta-ZnP2 crystal in order to clarify the internal structure of exciton polariton and also the dynamics of the relaxation processes in the photo-excited states. The crystal beta-ZnP_2 is proved to be the model system of the weakest electron-lattice coupling as far as we are aware of. In the course of this project, we have obtained following results ;1) In the relaxation from the higher exciton states as n=2,3,4 etc., the resonant 2LO Raman process is also important as is the ordinary 1LO scattering process. 2) In the excitation spectrum of the triplet exciton luminescence, we found very sharp Hydrogen-like series up to n=9. On the other hand, conversion from the triplet state to the singlet exciton polariton luminescence occurs only from the new sharp exciton series for n<greater than or equal>3, which is different from s-like series, but associated with d-like ones derived from the s-d mixing. Th … More is result poses a new problem upon the internal structure of the exciton. 3) Under the magnetic field, those peaks in the excitation spectra shows sharp fine characteristic Zeeman splitting. Fine dichroic Zeeman patterns are also observed in the triplet exciton luminescence spectra. These results were presented at the International Conference on Luminescence in Prague. A graduate course student obtained D.Sc.on the basis of there results. 4) Decay time of triplet exciton luminescence has been observed to be of the order of nanosecond, too short to be explained by using the very small oscillator strength of 10^<-6>. From the detailed analysis, it is found that the triplet excitons easily form exciton molecules. There is a possibility that triplet excitons are transferred into the singlet state by absorbing acoustic phonons which was suggested by the experiment of anti-Stokes excitation spectra. This is the new relaxation process so far not found in the intermediate and strong electron-lattice coupling systems. Together with the dispersion curve of triplet exciton polariton determined by the hyper-Raman experiment by Prof.Froehlich in Dortmund, numerical analysis of relaxation rate seems to become possible. 5) In another polymorph alpha-ZnP_2, two-phonon assisted indirect exciton luminescence is clearly confirmed through the temperature change of luminescence. This result was presented at the international conference of exciton in Germany and also published in JPSJ.Collaboration is still in progress in ISSP Univ.Tokyo on the temperature change experiment of the luminescence in beta-ZnP_2 , also in Kyoto on the time domain experiments and in Dortmund Univ.on the nonlinear spectroscopy. Less

我们研究了单斜二磷化锌β - znp2晶体的共振二次发射，以澄清激子极化子的内部结构和光激发态弛豫过程的动力学。证明β - znp_2晶体是目前所知的电子-晶格耦合最弱的模型体系。在这个项目的过程中，我们获得了以下结果：1)在n=2、3、4等高激子态的弛豫中，共振的2LO拉曼过程与普通的1LO散射过程一样重要。2)在三重态激子发光的激发光谱中，在n=9处发现了非常尖锐的类氢序列。另一方面，从三重态到单重态激子极化发光的转换只发生在n< >或等于>3的新尖锐激子系列中，这与类s激子系列不同，但与s-d混合产生的类d激子相关。这一结果对激子的内部结构提出了一个新的问题。3)在磁场作用下，激发谱峰表现出明显的精细塞曼分裂特征。在三重态激子发光光谱中也观察到细小的二向色塞曼模式。这些结果在布拉格举行的国际发光会议上发表。一名研究生在此基础上获得了博士学位。4)三重态激子发光的衰减时间已被观察到在纳秒量级，太短了，不能用非常小的振荡器强度10^<-6>来解释。从详细的分析中发现，三重激子很容易形成激子分子。反斯托克斯激发谱实验表明，三重态激子有可能通过吸收声子而转移到单重态。这是迄今为止在中强电子-晶格耦合体系中未发现的新的弛豫过程。结合多特蒙德大学froehlich教授的超拉曼实验确定的三重态激子极化子色散曲线，弛豫速率的数值分析似乎成为可能。5)在另一种晶型α - znp_2中，双声子辅助的间接激子发光通过发光的温度变化得到了明确的证实。这一结果在德国举行的激子国际会议上发表，并在JPSJ上发表。目前，东京ISSP大学正在进行β - znp_2发光的温度变化实验，京都大学在进行时域实验，多特蒙德大学在进行非线性光谱学实验。少