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 2p→8a1∗ excitation of solid SiCl4 induces the significant enhancement (∼900%) of the Cl+ yield, while the Cl 2p→7a1∗ 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 7a1∗ 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.