PHOTON-STIMULATED ION DESORPTION FROM CONDENSED SICL4 BY RESONANT EXCITATION AT THE K-EDGES

Photon-stimulated desorption of fragment and molecular ions from conde nsed SiCl4 following the Si 1s and Cl 1s excitations has been investig ated using synchrotron radiation, The Si+, Cl+, SiCl+ and SiCl3+ ions were observed almost in comparable intensity at the Sits excitation. T he presence of atomic Si+ ions is interpreted by the formation of SiCl 4n+ (n greater than or equal to 3) ions through KLL and successive LVV Anger decay. On the other hand, more than 80% of the desorbed species were Cl+ ions by the Cl 1s excitation, which suggests that the multip le charges produced by the Auger decay localize on the chlorine atom. The photon-energy dependence of the Cl+ yield revealed that the Cl+ yi eld at the Cl 1s --> sigma(8a(1)) resonance excitation is higher than that at the Cl 1s --> sigma(9t(2)) resonance excitation. It was also found that the excitation at the energy higher than Cl 1s --> sigma resonance scarcely induces the Cl+ desorption. The high desorption yie ld at the Cl 1s --> sigma(8a(1)) resonance is interpreted by the fact that the ga, orbital into which the Cl 1s electron is excited is most ly composed of the Cl 3p antibonding state, which reduces the binding energy of the Si-Cl bond.