UV angle-resolved photoelectron spectra of mixed methylene dihalides using synchrotron radiation

Photoelectron spectra for the dihalomethanes CH₂BrCl, CH₂ClI and CH₂Br₂ have been recorded with photons in the energy range 19–115 eV using Daresbury Laboratory Synchroton Radiation Source. Ionization energies have been measured for all valence falling within this energy including Br 3d and I 4d orbitals. Asymmetry parameters have been measured for all intense ionization processes and characteristic Cooper minima observed for halogen lone pair orbitals. For CH₂ClI lone pair orbital β spectra show strong evidence of mixed halogen character although a similar situation is not observed for CH₂BrCl. Partial photoionization cross sections are tabulated for the observed ionization processes. Detailed spectra are presented for the molecule CH₂ClI since this appears to be the first photoelectron study of this molecule.