Study of ultrafast relaxation dynamics of localized center in solids by femtosecond Raman spectroscopy

飞秒拉曼光谱研究固体局域中心超快弛豫动力学

• 批准号: 03452037
• 负责人: NAKAMURA Arao
• 金额: $ 4.48万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1991
• 资助国家: 日本
• 起止时间: 1991 至 1992
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-03452037/
• 关键词: electron-phonon interaction; relaxation process; F center; self-trapped hole; self-trapped exciton; coherent Raman spectroscopy; 自己捕獲正孔; 緩和励起子; フェムト秒ポンプ・プロ-ブ分光; 超心速緩和過程; アルカリハライド; 束縛励起子

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.

1)安装飞秒激光系统。我们安装了一个高功率飞秒激光系统，该系统提供波长为600和300 nm的泵浦脉冲，光谱范围为400至950 nm的白色连续体探测脉冲，脉冲持续时间为100 fs。2)碱卤化物的飞秒非线性光谱：a)我们发现KBr中F中心绝热势能面（APES）的弛豫过程是动态的，发生在100 fs内。b)在KBr中F中心的形成过程中，F中心是在空穴自俘获之前形成的，F中心的弛豫来自于on-center型自俘获激子（STE）。c)我们首次观测到在KI最低的ape上，STE以两个极小值之间的波串的形式振荡。d)在碱碘化物（KI和RbT）中，自由空穴首先转化为单中心自困空穴，随后形成双中心自困空穴（V_k中心）。此外，激子自俘获的初始阶段不是由一个类v_k中心和一个自由电子组成，而是一个与电子相关的单中心自俘获空穴是STE形成的前驱态之一。这是自俘获初始过程的第一个实验发现。3) ZnTe:O的飞秒非线性光谱：我们观察了束缚激子与声子的中间耦合弛豫过程。LO声子的激子-晶格弛豫伴随着LO声子的发射而发生。

项目成果

4) S. Iwai, T. Tokizaki, a. Nakamura, T. Shibata, K. Tanimura and N. Itoh: "Femtosecond spectroscopy of self-trapping processes of holes and exitons in alkali halides." J. Luminescence. (1993)

4）S. Iwai，T. Tokizaki，a。

T.Tokizaki: "Ultrafast Formation Processes of Self-Trapped Excitons in Alkali Crystals under Band-to-Band Excitation" Ultrast Phenomena VIII. (1992)

T.Tokizaki：“带间激发下碱晶体中自陷激子的超快形成过程”Ultrast Phenomena VIII。

A.Nakamuram,T.Tokizaki: "Ultrafast optical nonlinearity of semiconducting microcrystallites in glass matrices" Proceedings of Toyota conference on nonlinear optical materials. (1992)

A.Nakamuram，T.Tokizaki：“玻璃基体中半导体微晶的超快光学非线性”丰田非线性光学材料会议记录。

T.Tokizaki: "Femtosecond Cascade-Excitation Spectroscopy for Nonradiative Deexcitation and Lattice Relaxation of the Self-Trapped Exciton in NaCl" Physical Review Letters. 67. 2701-2704 (1991)

T.Tokizaki：“用于氯化钠中自陷激子的非辐射去激发和晶格弛豫的飞秒级联激发光谱”物理评论快报。

2)T. Tokizaki, S. Iwai, T. Shibata, A. Nakamura, T. Tanimura and N. Itoh: "Ultrafast formation processes of self-trapped excitons in alkali iodide crystals under band-to-band excitation." Ultrafast Phenomena VIII. (1993)

2）T。