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Formation and decay of superexcited molecules as studied by synchrotron-radiation photon and electron collisions

通过同步辐射光子和电子碰撞研究超激发分子的形成和衰变

基本信息

批准号：
13440175
负责人：
NORIYUKI Kouchi
金额：
$ 4.8万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

1.Doubly excited molecules as studied by synchrotron-radiation photon collisionsWe have measured the absolute values of the cross sections for the emission of fluorescences in the ultraviolet and visible ranges from neutral fragments in the photoexcitation of methane, ammonia, water and ethylene as a function of incident photon energy in the range 10-40 eV. Interestingly, the oscillator strengths for Balmer fluorescences from doubly excited methane, ammonia and water in the inner valence range amount to the magnitudes comparable to those from nearby single-hole one-electron superexcited states of these molecules, which is a strong indication of the breakdown of the independent electron model. An important role of the doubly excited ethylene has been found in the cross section curves for Balmer fluorescences.2.Superexcited molecules as studied by the coincident electron-energy-loss spectroscopyThe coincident electron-energy-loss spectroscopy is an excellent means for investigating the s … More uperexcited molecules, which was developed by our group a few years ago. The electron energy-loss spectra are measured in coincidence with the emission of the vacuum-ultraviolet fluorescences from neutral fragments in electron collisions with molecules, in which the structures attributed to the superexcited states are shown up. We have measured the coincident electron-energy-loss spectra of molecular nitrogen, molecular oxygen, and methane in the valence range at several incident electron energies and scattering angles. Interestingly the optically-forbidden doubly excited states of nitrogen give larger contribution than the allowed doubly excited states. The time-resolved coincident electron-energy-loss spectra of oxygen have been measured to study the superexcited oxygen molecules in detail. The intense peaks attributed to the doubly excited methane have been found in the range above 25 eV. The second-generation system equipped with a position-sensitive detector for electrons has been developed to obtain the spectra much more efficiently Less

1.同步辐射光子碰撞研究的双激发分子我们测量了甲烷、氨、水和乙烯光激发中中性碎片在紫外和可见光范围内发射荧光的横截面的绝对值，作为10-40 eV范围内入射光子能量的函数。有趣的是，内价范围内的双激发甲烷、氨和水的巴尔默荧光的振荡器强度与这些分子附近的单孔单电子超激发态的振荡强度相当，这有力地表明了独立电子模型的崩溃。在巴尔默荧光截面曲线中发现了双激发乙烯的重要作用。2.重合电子能量损失谱研究超激发分子重合电子能量损失谱是研究超激发分子的极好手段，是我们课题组几年前开发的。电子能量损失光谱的测量与电子与分子碰撞中性碎片发射真空紫外荧光同时进行，其中显示了归因于超激发态的结构。我们测量了氮分子、氧分子和甲烷在价态范围内在几个入射电子能量和散射角下的重合电子能量损失谱。有趣的是，氮的光学禁止双激发态比允许的双激发态贡献更大。测量了氧的时间分辨重合电子能量损失谱，以详细研究超激发氧分子。在 25 eV 以上的范围内发现了归因于双激发甲烷的强烈峰。配备位置敏感电子探测器的第二代系统已经开发出来，可以更有效地获取光谱。