Ultra-High-Resolution Spectroscopy of Solid Hydrogen

固体仲氢是一种很有前途的高分辨光谱介质。由于分子间的弱相互作用，氢分子和嵌入固体中的分子的转动和振动激发态都是量子化的。此外，由于内部运动和晶体声子之间的能量失配，激发态的寿命变得非常长，使得光谱线宽变得窄至1 MHz。本研究的目的是发展一种以固体仲氢为介质的凝聚相超高分辨光谱新技术，以便更详细地阐明凝聚相中分子的旋转运动以及分子间的多体相互作用。在课题研究期间，我们取得了以下新成果。(1)利用高分辨红外光谱研究了仲氢晶体中仲氢分子和杂质邻位氢对的纯振动跃迁，定量地获得了激子跳跃和分子间相互作用的信息。(2)我们发现掺杂在仲氢晶体中的分子也表现出量子化的转动-振动态。高分辨的红外光谱使我们能够发展分析凝聚相分子振转运动的新理论。(3)红外光谱首次观察到了几个纯隧穿化学反应。(4)我们已经开发了一种在固体中产生分子离子的技术，这使我们能够在高分辨率下研究化学感兴趣的类氢离子。

Solid parahydrogen is a promising medium for high resolution spectroscopy. The rotational and vibrational excited states of hydrogen molecules and molecules embedded in the solid are well quantized on account of the weak intermolecular interaction. Moreover, due to the energy mismatch between the internal motion and the crystal phonon, the lifetime of the excited states becomes enormously long so that the spectral linewidth becomes as narrow as 1MHz. The purpose of the present research is to develop a new technique of ultra-high-resolution spectroscopy of condensed phase using solid parahydrogen as a medium in order to clarify rovibarional motion of molecules as well as intermolecular many-body interactions in condensed phase in great detail. We obtained the following new results during the period of the research project.(1) High-resolution infrared spectroscopy of pure vibrational transitions of parahydrogen molecules and impurity ortho-hydrogen pairs in parahydrogen crystals was performed to obtain information on exciton hopping and intermolecular interaction quantitatively.(2) We found that molecules doped in parahydrogen crystal also show quantizedrotation-vibration states. The well-resolved infrared spectrum allows us to develop new theory for the analysis of rovibrational motion of molecules in condensed phase.(3) Several pure tunneling chemical reactions were observed for the first time by infrared spectroscopy.(4) We have developed a technique toproduce molecular ions in the solid which allows us to study hydrogenic ions of chemical interests under high-resolution.