Penning ionization of C6H5X (X = F, Cl, Br, I) upon collision with metastable He*(23S) atoms was studied by two-dimensional (collision-energy/electron-energy-resolved) Penning ionization electron spectroscopy. Partial ionization cross sections are found to be larger for ionization from orbitals having n and π characters. Interaction potentials between the target molecule and the He* atom were found to be highly anisotropic. Attractive interaction was dominated around the collinear access of He*(23S) to C - F axis in C6H5F. On the other hand, attractive interaction was localized around the out-of-plane perpendicular approach of He* atom to C - X bond (X = Cl, Br, I). Attractive interaction for these compounds increases on going from C6H5Cl to C6H5I. Furthermore, the electronic factor due to the size of the halogen p orbitals and the conjugation between the benzene ring and the halogen atoms and also the steric factor due to the shielding effect were found to be important.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry