Substituent effect on the collision energy dependence of Penning ionization cross sections

Kohji Okamura, Hideo Yamakado, and Koichi Ohno
(Department of Chemistry, Graduate School of Science, Tohoku University)

In order to probe anisotropic interaction potentials between metastable He*(23S) atoms and target molecules, we have measured the collision energy dependence of partial Penning ionization cross sections upon collision with He*(23S). We have studied the difference of the collision energy dependence between some substituents. It was found that the interaction potentials between He*(23S) and molecules become more repulsive by existence of electron-withdrawing substituents and become more attractive by existence of electron-releasing substituents. These results were supported by ab initio molecular orbital calculations of interaction potentials.