Borodin Andriy, Yamazaki Masakazu, Kishimoto Naoki, Ohno Koichi
Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Sendai 980-8578, Japan.
J Phys Chem A. 2006 Feb 9;110(5):1783-90. doi: 10.1021/jp053469v.
Penning ionization of phenylacetylene and diphenylacetylene upon collision with metastable He*(2(3)S) atoms was studied by collision-energy-/electron-energy-resolved two-dimensional Penning ionization electron spectroscopy (2D-PIES). On the basis of the collision energy dependence of partial ionization cross-sections (CEDPICS) obtained from 2D-PIES as well as ab initio molecular orbital calculations for the approach of a metastable atom to the target molecule, anisotropy of interaction between the target molecule and He*(2(3)S) was investigated. For the calculations of interaction potential, a Li(2(2)S) atom was used in place of He*(2(3)S) metastable atom because of its well-known interaction behavior with various targets. The results indicate that attractive potentials localize in the pi regions of the phenyl groups as well as in the pi-conjugated regions of the acetylene group. Although similar attractive interactions were also found by the observation of CEDPICS for ionization of all pi MOs localized at the C[triple bond]C bond, the in-plane regions have repulsive potentials. Rotation of the phenyl groups about the C[triple bond]C bond can be observed for diphenylacetylene because of a low torsion barrier. So the examination of measured PIES was performed taking into consideration the change of ionization energies for conjugated molecular orbitals.
通过碰撞能量/电子能量分辨二维彭宁电离电子能谱（2D-PIES）研究了苯乙炔和二苯乙炔与亚稳态He*(2(3)S)原子碰撞时的彭宁电离。基于从2D-PIES获得的部分电离截面的碰撞能量依赖性（CEDPICS）以及亚稳态原子接近目标分子的从头算分子轨道计算，研究了目标分子与He*(2(3)S)之间相互作用的各向异性。为了计算相互作用势，由于Li(2(2)S)原子与各种目标的相互作用行为已知，因此用它代替He*(2(3)S)亚稳态原子。结果表明，吸引势位于苯基的π区域以及乙炔基的π共轭区域。尽管通过观察位于C≡C键处所有π分子轨道电离的CEDPICS也发现了类似的吸引相互作用，但面内区域具有排斥势。由于扭转势垒较低，对于二苯乙炔可以观察到苯基围绕C≡C键的旋转。因此，在考虑共轭分子轨道电离能变化的情况下对测量的PIES进行了检查。
