1992 Fiscal Year Final Research Report Summary
Study of ultrafast relaxation dynamics of localized center in solids by femtosecond Raman spectroscopy
| Project/Area Number |
03452037
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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 |
固体物性
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| Research Institution | Nagoya University |
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Principal Investigator |
NAKAMURA Arao Faculty of Engineering Professor, 工学部, 教授 (50159068)
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| Co-Investigator(Kenkyū-buntansha) |
TOKIZAKI Takashi Nagoya University Faculty of Engineering Assistant Professor, 工学部, 助手 (20207541)
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| Project Period (FY) |
1991 – 1992
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| Keywords | electron-phonon interaction / relaxation process / F center / self-trapped hole / self-trapped exciton / coherent Raman spectroscopy / 自己捕獲正孔 |
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| Research Abstract |
1)Installation of a femtosecond laser system.
We installed a high power femtosecond laser system which provided pumping pulses with wavelengths of 600 and 300 nm,probe pulses with a white continuum in the spectral range of 400 to 950 nm and a pulse duration of 100 fs.
2) Femtosecond nonlinear spectroscopy in alkali halides:
a) We found that the relaxation process on the adiabatic potential energy surface (APES) of F center in KBr is dynamical and occurs within 100 fs. b) In the formation processes of F center in KBr, an F center is formed before the self-trapping of a hole and the F center relaxation occurs from the on-center type self-trapped exciton (STE). c) We observed for the first time the oscillation of the STE as a wavepaquet between two minima on the lowest APES in KI. d) In alkali iodides (KI and RbT) a free hole is first converted to a one-center self-trapped hole and subsequently a two-center self-trapped hole (V_k center) is formed. Furthermore, the initial stage of self-trapping of a exciton does not consist of a V_k-like center and a free electron but a one-center self-trapped hole correlated with an electron is one of the precursor states for the STE formation. These are the first experimental finding of the initial processes of the self-trapping.
3) Femtosecond nonlinear spectroscopy in ZnTe:O: We observed the relaxation processes of bound excitons with the intermediate coupling with phonons. The exciton-lattice relaxation with emission of LO phononsoccurs with a period of the LO phonon.
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