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

基本信息

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

项目摘要

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）飞秒激光系统的安装。我们安装了高功率飞秒激光系统，提供波长为600和300 nm的泵浦脉冲，光谱范围为400至950 nm的白色连续谱的探测脉冲，脉冲持续时间为100 fs.2) 碱金属卤化物中的飞秒非线性光谱：a) 我们发现绝热势能面上的弛豫过程KBr 中 F 中心的 (APES) 是动态的，发生在 100 fs 内。 b)在KBr中F中心的形成过程中，F中心在空穴自俘获之前形成，并且F中心弛豫由在中心型自俘获激子(STE)发生。 c) 我们首次观察到 STE 的振荡作为 KI 中最低 APES 上两个最小值之间的波包。 d) 在碱金属碘化物（KI 和 RbT）中，自由空穴首先转化为一中心自捕获空穴，随后形成二中心自捕获空穴（V_k 中心）。此外，激子自捕获的初始阶段并不由类V_k中心和自由电子组成，而是与电子相关的一中心自捕获空穴是STE形成的前驱态之一。这是自捕获初始过程的第一个实验发现。3）ZnTe：O中的飞秒非线性光谱：我们观察到了与声子中间耦合的束缚激子的弛豫过程。 LO 声子发射引起的激子晶格弛豫伴随着 LO 声子的周期而发生。