An experimental and theoretical investigation of the valence shell photoelectron spectrum of cyanogen chloride

The valence shell photoelectron spectrum of cyanogen chloride has been stud ied using HeI and synchrotron radiation. In the outer valence region the mo lecular orbital model of ionization holds, and the main bands can be associ ated with single-hole states. However, in the inner valence region electron correlation effects become important, and these result in complex satellit e structure being observed. Vertical ionization energies and spectral inten sities have been computed using the Green's function approach, and the resu lts have facilitated an interpretation of the experimental spectra. Photoel ectron angular distributions and branching ratios have been measured and ha ve been used to assess the bonding characteristics of the outer valence mol ecular orbitals. The experimental data for the 8 sigma orbital display an e nergy dependence which suggests that photoionization from this orbital may be influenced by the chlorine 3p Cooper minimum. The extent to which the 8s orbital can be considered as a chlorine atom lone-pair is discussed. Vibra tional structure has been observed in the (X) over tilde (2)Pi, (A) over ti lde (2)Sigma (+) and (B) over tilde (2)Pi photoelectron bands recorded with HeI radiation, and has been assigned to progressions involving the nu (+)( 1) and nu (+)(3) modes.