Development of a method for imaging molecular orbital pattern and foundation of momentum spectroscopy

各种分子性质，如反应性，是由一个特定价电子的分子轨道模式决定的。这个项目的目的是发展一种在动量空间中成像这种分子轨道图案的方法。为了实现这个项目，我们建造了一个装置，旨在以三重符合的方式探测两个出射电子和由电子康普顿散射产生的碎片离子，并测量三个带电粒子之间的矢量关联。该装置随后被用于H_2和O_2分子的离解电离过程。虽然实验结果存在相当大的统计不确定性，但它们被发现符合我们的预期。例如，在动量空间中观察到H_2分子的2_lt；Sδ_g&gt；电子轨道沿垂直于分子轴的方向伸长，这是众所周知的在位置空间中沿分子轴伸展的。这种观察完全归因于傅里叶变换的性质。另一方面，对于分子的2&lt；Pδ_u&gt；轨道，已经清楚地观察到了p型轨道的性质，即叶和节面分别位于平行和垂直于分子轴的方向。通过这种方式，我们首次成功地证明了以三维形式观察分子轨道是完全可能的。该项目的成果被高度评价为分子轨道成像的开创性工作，为详细研究分子的束缚电子波函数打开了大门。这项工作已被邀请参加广泛的国际和国内会议(40次特邀讲座)，并于2008年3月向首席调查员颁发了日本化学学会(CSJ)创造性工作奖。

Various kinds of molecular properties such as reactivity are governed by molecular orbital pattern of a specific valence electron. The purpose of this project is to develop a method for imaging such molecular orbital pattern in momentum space.In order to realize this project, we have constructed an apparatus that aims to detect in triple coincidence the two outgoing electrons and the fragment ion produced by electron Compton scattering and to measure vector correlations among the three charged particles. The apparatus has been subsequently employed for dissociative ionization processes of the H_2 and O_2 molecules. Although the experimental results suffer from rather large statistical uncertainties, they are found to fulfill our expectations. For instance, the 2_<Sδ_g> electron orbital of the H_2 molecule has been observed in momentum space as what is elongated in the direction perpendicular to the molecular axis, which is well known to be stretched along the molecular axis in position space. This observation is due entirely to nature of Fourier transform. On the other hand, for the 2_<Pδ_u> orbital of the molecule, the p-type orbital nature, which lobes and a nodal plane lie in the direction parallel and perpendicular to the molecular axis respectively, has been clearly observed. In this way, we have successfully demonstrated for the first time that looking at molecular orbitals in the three dimensional form is totally possible.The achievements of this project has been highly evaluated as pioneering work for molecular orbital imaging, opening the door for detailed studies on bound electronic wave functions of molecules. This work has been invited to a broad range of international and domestic conferences (40 invited talks) and The Chemical Society of Japan (CSJ) Award for Creative Work has been provided to the head investigator in 2008 March.