X-ray initiated molecular photochemistry of Cl-containing adsorbates on a Si(1 0 0) surface using synchrotron radiation

X-ray initiated molecular photochemistry for SiCl4 and CCl4 adsorbed on Si(1 0 0) at ∼90 K following Cl 2p core-level excitation is investigated by photon stimulated ion desorption and ion kinetic energy distribution measurements. The Cl 2 p → 8 a 1 ∗ excitation of solid SiCl4 induces the significant enhancement (∼900%) of the Cl+ yield, while the Cl 2 p → 7 a 1 ∗ excitation of condensed CCl4 leads to a moderate enhancement (∼500%) of the Cl+ yield. The enhancement of Cl+ yield at the specific core-excited states is strongly correlated to the ion escaped energy. Upon X-ray exposure for CCl4 adsorbed on Si(1 0 0) (20-L exposure), the Cl+ yields at 7 a 1 ∗ resonances decrease and new structures at higher photon energies are observed. Cl+ yields at these new resonances are significantly enhanced compared to those at other resonances. These changes are the results of desorption and surface reaction of the CCl4–Si surface complex due to X-ray irradiation. We have demonstrated that state-specific enhancement of ion desorption can be successfully applied to characterize the reaction dynamics of adsorbates adsorbed on surfaces by X-ray irradiation.