| Co-Investigator(Kenkyū-buntansha) |
OKAMOTO Hiroshi THE UNIVERSITY OF TOKYO, ADVANCED MATERIALS SCIENCE, ASSOCIATE PROFESSOR, 大学院・工学研究科, 助教授 (40201991)
SUEMOTO Toru THE UNIVERSITY OF TOKYO, THE INSTITUE FOR SOLID STATE PHYSICS, PROFESSOR, 物性研究所, 教授 (50134052)
TAKEDA Jun YOKOHAMA NATINAL UNIVERSITY, FACULTY OF ENGNEERING, ASSOCIATE PROFESSOR, 大学院・工学研究院, 助教授 (60202165)
|
|---|
| Research Abstract |
The temporal evolution of photo-excited state in quasi-one-dimensional halogen-bridged platinum complexes [Pt(en)_2][Pt(en)_2X_2][(ClO_4)_4 (abbreviated as Pt-X, X=Cl, Br or I), has been comprehensively studied by femtosecond time-resolved luminescence spectroscopy. In Pt-Br, we have observed a wave-packet oscillation of a period of about 300fs in an adiabatic potential well associated with a self-trapped exciton (STE). The STE's have a lifetime of about 5.5 ps. In Pt-Cl, short-lived hot luminescence is found in the low energy side of a STE luminescence band. The overall behavior of luminescence is explained by the vibrational relaxation within 2 ps and the lifetime of the STE with 30 ps. These behaviors of luminescence are reproduced by a model calculation based on wavepacket propagation on an interaction mode composed of frequency-dispersed bulk phonons. In Pt-I, the STE luminescence decays much faster (0.65 ps) than those in Pt-Cl and Pt-Br. From the observed dependence of STE lifetime, it is supposed that the barrier becomes lower with decrease of the CT gap energy, and the charged-soliton pairs are efficiently produced by photoexcitation in narrow CT gap. In Pt-I, especially, the system seems to go toward the soliton pair before the thermalization as STE.
New quasi-one-dimensional halogen-bridged platinum binuclear compound, R_4[Pt_2(pop)_4l](R=C_3H_7)_2NH_2) is found to show both the pressure- and photo-induced phase transitions at room temperature.
We have developed the optical Kerr gate fluorescence spectroscopy with a subpicosecond time resolution as a new spectroscopic tool to investigate ultrafast relaxation processes. The typical Kerr efficiency and instrumental response function of the system are 〜5% and 〜250fs. This system is applied to measure the decay of electron-hole plasma state in ZnO.
|
