X-ray absorption study of potential barrier effect in group 14 tetrachlorides (GeCl 4, SnCl 4) and group 15 trichlorides (PCl 3, AsCl 3)

Abstract

Inner-shell excitation spectra of GeCl 4, SnCl 4, PCl 3 and AsCl 3 were obtained in gas phase at room temperature with a total ion-yield technique at the LURE Super ACO and DCI storage rings in Orsay. The inner-shell excitation spectra include Ge 2p, Sn 2p, P 1s, As 2p, and Cl 1s in GeCl 4, SnCl 4, PCl 3 and AsCl 3, respectively, and are interpreted in the framework of the potential barrier concept, according to electric dipole selection rules. The well-resolved below-edge features in the metal 2p excitation spectra of GeCl 4 and SnCl 4 show a similar shape. Moreover, complementary experimental results of ETS with the support of MS-X α calculations are reported and correlated with the C 1s, Si 2p, Ge 2p and Sn 2p term values of the lowest vacant orbitals for CCl 4, SiCl 4, GeCl 4 and SnCl 4, respectively, in order to study the trend of the stabilization energy of the various empty orbitals in the neutral and in the core ionized molecules. The P 1s spectrum of PCl 3 has been assigned and the As 2p spectrum of AsCl 3 compared with the published P 2p spectrum of PCl 3. The 1s excitation spectra of the chlorine ligand in the tetrachloride (GeCl 4, SnCl 4 and trichloride (PCl 3, AsCl 3) series are very sensitive to the change of symmetry and bonding. A linear correlation between (MCl) bond lenght (with M  Ge, Sn, P, As) and the energy of the Cl 1 s → σ ∗ (MCl) shape resonance observed above the Cl is ionization threshold has been obtained.