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Studies on intramolecular processes of excited polyatomic molecules by means of Zeeman quantum beat spectroscopy

塞曼量子拍光谱研究激发多原子分子的分子内过程

基本信息

批准号：
61430004
负责人：
TSUCHIYA Soji
金额：
$ 7.04万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (A)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1987
项目状态：
已结题

项目摘要

This work aims to elucidate the level structure of the rovibronic state of an electronically excited polyatomic molecule by means of the quantum beat spectroscopy. When molecules are excited coherently to more than one electronically excited levels and the fluorescence transitions from these levels occur to a common electronic ground level, a beat phenomenon appears in the fluorescence. The spectrum of the beat frequencies reflects the level structure of the excited molecule. Since this observation is made in the time domain, its resolution reaches as high as 1 MHz. Thus, it is possible to discuss a level splitting caused very weak perturbation.The above spectroscopic method has been applied to observe the level structures of CS_2 (V^1B_2) and C_2H_2 (A^^< wave >^4A_u) in supersonic jets. When CS_2 is excited to selected rovibronic levels of the V^1B_2 state under a weak magnetic field by pulsed laser excitation, the quantum beats appear due to Zeeman splitting of the relevant levels. This observation implies that excited CS_2 has a magnetic moment which attributable to interaction of the singlet^1B_2 state with the triplet ^3A_2.Quite similarly, most of rovibronic levels split into several levels each of which has its specific radiative lifetime and exhibits quantum beats due to Zeeman splitting as well as level anticrossing. Based on these quantum beat spectral data, the details of the coupling mechanism have been discussed.

本文利用量子拍频技术研究了电子激发多原子分子振子态的能级结构。当分子被相干激发到一个以上的电子激发能级，并且从这些能级发生荧光跃迁到一个共同的电子基态时，在荧光中出现拍现象。拍频的频谱反映了受激分子的能级结构。由于这种观测是在时域进行的，其分辨率高达1 MHz。用这种光谱方法观察了CS_2（V^1B_2）和C_2H_2（A^< wave >^4A_u）在超音速喷流中的能级结构。当CS_2在弱磁场下被脉冲激光激发到V^1B_2态的特定振子能级时，由于相应能级的塞曼分裂而出现量子拍频。这一观测结果表明，激发态CS_2具有一个磁矩，该磁矩可归因于单重态^1B_2与三重态^3A_2的相互作用。非常相似的是，大多数旋振能级分裂成若干个能级，每个能级都有其特定的辐射寿命，并由于塞曼分裂和能级反交叉而表现出量子拍频。基于这些量子拍频光谱数据，详细讨论了耦合机制。