Collision-energy-resolved Penning ionization electron spectroscopy of thiazole and benzothiazole: study of ionic states and anisotropic interactions between a metastable He(23S) atom and hetero cyclic compounds.
Collision-energy-resolved Penning ionization electron spectroscopy of thiazole and benzothiazole: study of ionic states and anisotropic interactions between a metastable He(23S) atom and hetero cyclic compounds.
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DOI：
10.1021/jp061573m
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发表时间：
2006-05
期刊：
影响因子：
--
通讯作者：
M. Yamazaki;N. Kishimoto;K. Ohno
中科院分区：
文献类型：
--
作者：
M. Yamazaki;N. Kishimoto;K. Ohno
采用碰撞能/电子能分辨二维Penning电离电子能谱结合从头算分子轨道计算，研究了亚稳He（2(3)S）原子与芳香杂环化合物（噻唑和苯并噻唑）之间的各向异性相互作用及其电子结构。在不同的离子状态下，部分电离截面（CEDPICS）的碰撞能量依赖取决于被移除电子的分子轨道的各向异性程度。研究发现，噻唑和苯并噻唑在氮孤对轨道延伸的区域周围最强烈地吸引He（2(3)S）原子。对于另一种杂原子硫，这种相互作用相对较弱，但在垂直于分子平面的方向上发现了一定的吸引相互作用。苯并噻唑在面外方向广泛吸引He（2(3)S）原子，因为苯部分比五元环表现出更深的势阱。从观察到的CEDPICS和从头算分子轨道计算中讨论了包括振荡态在内的离子态的分配。特别地，对于卫星波段，一个构型相互作用计算很好地支持了波段强度的负碰撞能量依赖，该计算将卫星波段指定为伴随pi-pi或n-pi激发的pi轨道的电离。
Anisotropic interactions between a metastable He(2(3)S) atom and aromatic heterocyclic compounds (thiazole and benzothiazole) as well as their electronic structures were studied by means of collision-energy/electron-energy resolved two-dimensional Penning ionization electron spectroscopy combined with ab initio molecular orbital calculations. Different collision-energy dependence of partial ionization cross sections (CEDPICS) were clearly observed for different ionic states depending on anisotropic extents of molecular orbitals from which an electron is removed. It was found that thiazole and benzothiazole most strongly attract a He(2(3)S) atom around the region where the nitrogen lone pair orbital extends. For another heteroatom, sulfur, it is relatively weak, but a certain attractive interaction was found for the directions perpendicular to the molecular plane. Benzothiazole was shown to widely attract a He(2(3)S) atom in the out-of-plane directions, since the benzene moiety showed a deeper potential well than the five-membered ring. Assignments of the ionic states including shake-up states were also discussed from observed CEDPICS and ab initio molecular orbital calculations. In particular, for the satellite bands, a negative collision energy dependence of the band intensity was well supported by a configuration-interaction calculation that assigns the satellite bands to be the ionization from pi orbitals accompanying pi-pi or n-pi excitations.