Preparation of Excited Electron System and Its Dynamics

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This research project consists of three studies. 1.Optical properties of PBI_2 microcrystals embedded in organic polymer.Absorption spectra of ultra thin PbI_2 microcrystals embedded into E-MAA copolymer have been measured at low temperatures. From these results it is concluded that the translational motion of the exciton is size quantized. From the luminescence measurements, it is suggested that the binding energy of the exciton becomes very large both for the size confinement effect and the dielectric confinement effect by the surrounding polymer. Moreover, we have measured the hydropressure dependence of the exciton energy and the resonant Raman scattering as a function of the layer number.these results clarify that the atomic bonding of the PbI_2 mono-,double-and triple-layer crystals changes to the ionic one. Recently, the exciton-surface and exciton phonon interactions are studied by the pump-probe experiments,and shrinkage of the exciton wave function by the magneto-optical meas … More urements. 2.Optical properties of CuCl fine particles embedded in NaCl crystal. Under the size selective excitation of the exciton band,the size dependence of the luminescence decay time has been measured. It is found that the exciton superradiance due to the giant oscillator strength effect is taken place in the fine particles. The temperature dependence of the luminescence band width suggests the exciton is scattered by acoustic phonons at low temperatures. 3.Electronic properties of PbI_2,HgI_2,BiI_3,Na,K,Rb Clusters in zeolite.Quantum size effects of the exciton energy and the oscillator strength have been observed in the absorption spectra of PbI_2,HgI_2,BiI_3,clusters loaded in zeolite. In highly loaded PbI_2 clusters,the extremely high reflectivity is observed for the ordering of the cluster. In the zeolite containing Na,K,Rb,there appear absorption bands due to electronic tgransition between two levels of the cluster and a band due to the surface plasmon like formation. Especially,ferromagnetic phase is observed at about 3K in the zeolite containing K clusters with medium concentration. Less