X-RAY-ABSORPTION STUDY OF POTENTIAL BARRIER EFFECT IN GROUP-14 TETRACHLORIDES (GECL4, SNCL4) AND GROUP-15 TRICHLORIDES (PCL3, ASCL3)

Inner-shell excitation spectra of GeCl4, SnCl4, PCl3, and AsCl3 were o btained in gas phase at room temperature with a total ion-yield techni que at the LURE Super ACO and DCI storage rings in Orsay. The inner-sh ell excitation spectra include Ge 2p, Sn 2p, P Is, As 2p, and Cl Is in GeCl4, SnCl4, PCl3 and AsCl3, respectively, and are interpreted in th e framework of the potential barrier concept, according to electric di pole selection rules. The well-resolved below-edge features in the met al 2p excitation spectra of GeCl4 and SnCl4 show a similar shape. More over, complementary experimental results of ETS with the support of MS -X alpha calculations are reported and correlated with the C Is, 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 t he stabilization energy of the various empty orbitals in the neutral a nd in the core ionized molecules. The P Is spectrum of PCl3 has been a ssigned and the As 2p spectrum of AsCl3 compared with the published P 2p spectrum of PCl3. The Is excitation spectra of the chlorine ligand in the tetrachloride (GeCl4, SnCl4) and trichloride (PCl3, AsCl3) seri es are very sensitive to the change of symmetry and bonding. A linear correlation between (M-Cl) bond length (with M = Ge, Sn, P, As) and th e energy of the Cl 1s --> sigma(M-Cl) shape resonance observed above the Cl 1s ionization threshold has been obtained. (C) 1997 Elsevier Sc ience B.V.