Two-dimensional penning ionization electron spectroscopy of CH₂ClI and CH₂ClCN

The electronic structures of CH₂ClI and CH₂ClCN and anisotropic interactions with the metastable He*(2³S) atoms are studied by two-dimensional (electron-energy and collision-energy-resolved) Penning ionization electron spectroscopy as well as He I ultraviolet photoelectron spectroscopy. A broad band with the high ionization potentials in the Penning ionization electron spectrum of CH₂ClI is proposed to be related to autoionizations of the Cl** or I** species produced through dissociations after the excitation transfer from the He* atom. The split bands having the characteristics of the Cl and I 1one pair electrons (n_Cl and n_l) are observed in the spectra, as being interpreted by the intramolecular orbital (n_Cl ↔ n_l and n_Cl ↔ π_CN) through-space/through-bond interactions rather than the spin-orbit coupling effects. The magnitude of intramolecular orbital n_Cl ↔ π_CN interactions is much stronger than that of the n_Cl ↔ n_l interactions. The collision energy dependence of partial Penning ionization cross sections is interpreted on the basis of the delocalized characteristics of the electron distributions for respective molecular orbitals and the model calculations of the interaction potential energies.