Element-specific desorption from molecular adsorbates by core-to-valence resonant photoexcitation

Photon stimulated ion-desorption induced by deep-core excitation has been investigated for adsorbed PCl3 and S2Cl2 using synchrotron radiation. A pronounced element-specificity was observed at the g-edge photoexcitations of the two different absorption edges concerning the desorbed species. On the basis of the X-ray absorption and Auger decay spectra, it was found that the desorption of specific fragment-ions happens only at the 1s-->sigma* resonant excitation where the main decay channel is the KL2,3L2,3 spectator Anger transition. This process results in the final electronic configuration of v(-4)sigma(*1) where v denotes one of the valence levels. While the excitation at higher-energy region, where the main decay channel is the KL2,3L2,3 normal Auger transition resulting in the v(-4) configuration, induces scarcely any ion desorption. The observed element-specific desorption at the 1s-->sigma* resonance is interpreted by the bond-breaking due to the existence of a spectator electron in a highly antibonding sigma* orbital.