The intensity of the X ¹S + ® (C ls -1, p*)3II) transition of CO has been measured by electron energy loss spectroscopy using a range of scattering angles (0'-45') and impact energies (376 to 1806 eV) in order to investigate the momentum transfer dependence of a spin forbidden inner-shell excitation. A Franck-Condon factor analysis of the vibrational structure of the singlet and triplet (C ls -1,p*) states was used to quantify differences in the potential energy curves ofthese states. Ab initio self-consistent field configuration interaction (SCF-Cl) calculations were carried out to generate the potential curves of the 1II and 3II (C ls -1,p*) states. The electronic and vibrational energies and Franck-Condon factors are in good agreement with the experimental results. The calculations indicate that the difference in the 1II and 3II potential curves are related to differences in relaxation of both the (active)p * and other (passive) valence electrons.
Department of Chemistry, McMaster University, Hamilton, Ontario L8S 4M, Canada N. Kosugi Institute for Molecular Science, Myodaiji, Okazaki 444, Japan A. P. Hitchcock Department of Chemistry, McMaster University, Hamilton, Ontario L8S 4M1, Canada
Ó 1994 American Institute of Physics.