Dissociation-Recombination Dynamics of Iodine Molecule in Super Fluid State Helium

在本研究项目中，我们计划观察超流氦作为溶剂中的一些化学反应，并为此建立一个测量系统。为此所需要的实验装置是一个飞秒-皮秒激光系统与一个纳秒激光系统同步，该激光系统在泵浦探测实验之前激发。我们改进了之前搭建的实验系统来实现这种同步。已完成的改进如下：1)将重复频率为1kHz的雷根放大系统输出的激光脉冲，利用振流电机驱动的快门系统，压缩为可变重复的单脉冲。2)将泵浦探测实验中的探测波长提高到近红外区域。构建了一种新的多通道摄谱仪系统，实现了1100 ~ 1700nm范围内的测量。3)为了提高泵浦探测实验的精度，我们建立了一个新的系统，可以检测到探测光的小偏差小于10^<-7>。为了检验和提高这些实验系统的准确性，我们对光学克尔效应（OKE）进行了相干声子（CP）光谱和光学外差检测。在CP实验中，我们成功地清晰地探测了晶格振动的弛豫过程，并开发了一种利用离子辐照定量估计晶格缺陷数量的新方法。在OKE实验中，我们试图检测到非常小的信号来讨论分子取向弛豫与分子间相互作用之间的关系。这些新的实验结果是由于实验精度的显著提高而得到的。下一步，我们计划进入液氦实验。

In this research project we planned to observe some chemical reactions in the super-fluid helium as a solvent and to build up a measurement system for this purpose. The experimental setup needed for this purpose is a femtosecond-picosecond laser system synchronized with a nanosecond laser system which excites just before the pump-probe experiment. We improved the experimental system which we built previously to realize this synchronization. Completed improvements are follows ; 1)The laser pulses from Regen amplifier system of which repetition rate is 1kHz are reduced to a single pulse of variable repetition by using of a shutter system driven by galvano motors.2) To enhance the probe wavelength in pump-probe experiment to near-IR region. We built a new multi-channel spectrograph system and realize a measurement in 1100-1700nm area. 3) To improve the accuracy of the pump-probe experiment, we built up a new system to detect a small deviation of probing light less than about 10^<-7>. T check and to improve the accuracy of these experimental systems, we performed coherent phonon (CP) spectroscopy and optical heterodyne detection of optical Kerr effect (OKE). In CP experiment, we succeeded to probe the relaxation process of lattice vibrations clearly and developed a new method to estimate amount of lattice defects quantitatively by using of ion-irradiation. In OKE experiment, we attempted to detect very small signal to discuss the relationship between the molecular orientational relaxation and inter-molecular interactions. These new experimental result was obtained because of the remarkable improvement of the experimental accuracy. In the next step, we planned to enter the liquid helium experiment.