X-ray absorption study of potential barrier effect in group 14 tetrachlorides (GeCl4, SnCl4) and group 15 trichlorides (PCl3, AsCl3) Original Research Article

Inner-shell excitation spectra of GeCl4, SnCl4, PCl3 and AsCl3 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 GeCl4, SnCl4, PCl3 and AsCl3, 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 GeCl4 and SnCl4 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 CCl4, SiCl4, GeCl4 and SnCl4, 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 PCl3 has been assigned and the As 2p spectrum of AsCl3 compared with the published P 2p spectrum of PCl3. The 1s excitation spectra of the chlorine ligand in the tetrachloride (GeCl4, SnCl4 and trichloride (PCl3, AsCl3) 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 1s → σ∗ (MCl) shape resonance observed above the Cl is ionization threshold has been obtained.