1987 Fiscal Year Final Research Report Summary
Dynamics of Lattice Relaxation and Non-radiative Transition in Stongly Coupled Electron-Lattice System Excited Optaically
| Project/Area Number |
61460038
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
物性一般（含極低温･固体物性に対する理論）
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| Research Institution | Osaka City University |
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Principal Investigator |
OHKURA Hiroshi Fac. Eng., Osaka City University, Professor, 工学部, 教授 (50046801)
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| Co-Investigator(Kenkyū-buntansha) |
KAYANUMA Yosuke Fac. Science, Tohoku University, Research Assistant, 理学部, 助手 (80124569)
MORI Yuzo Fac. Eng., Osaka City University, Associate Professor, 工学部, 助教授 (30047279)
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| Project Period (FY) |
1986 – 1987
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| Keywords | Resonant Secondary Emission / Dynamics of Lattice Relaxation / Non-radiative Transition / Hot Luminescence / F Center / EL 2 in GaAs / Spin-Mixing / スピン混合パラメータ |
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| Research Abstract |
The dynamics of lattice relaxation of optically excited states of crystalline deep defects in solids have been investigated by means of the resonant secondary emission (RSE). The RSE occurs successively the resonant Raman scattering (RRS), hot luminescence (HL), and ordinary luminescence (OL). Crystalline defects tested are the F center in alkali halides, Cr^<3+> ions in emeralds, and EL2 in GaAs. Results are as follows: 1. The RSE and its linear polarization of F centers were measured over the whole Stokes range. The F-absorption band and RSE spectrum are described on the basis of a classical damping A_<1g> oscillator model in an anharmaonic adiabatic-potential with lattice relaxation time of 2.4 x 10^<-13> sec. Immediately after the resonant excitation, the linear coupling with the T2g-mode disappears because of a quadratic electron-lattice interaction which is induced by orbital expansion of F wavefunction. A fraction of transition at 2s-2p level crossing is estimated as 0.6. Anomaly of the OL observed at its lower energy side can be related to the turning point of a classical damping oscillator. The spin-mixing parameters in the Franck-Condon state have been calculated on a model scheme in which the spin-orbit and electron-lattice interactions with A_<1g>, E_g, and T_<2g>-modes are included. The photon=energy dependence of observed spin-mixing parameters are well explained. 2. The OL of Cr^<3+> ions observed in artificially grown and naturally grown emeralds showed specific difference. This is explained by the effect of the impurity Fe^<3+> ions being naturally present in the latter emeralds. 3. The RRS spectrum of EL2 in GaAs, which was excited by 1.34<micrn>m Nd:YAG laser, is observed at the anti-Stokes side. It shows a Lorentzian line peaked at 8,100 cm^<-1> with T_2= 6x10^<-15> sec. Its temperature dependence shows drastic change. This must be one of future problems to be solved.
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