Photon-stimulated desorption of neutralO2fromYBa2Cu3O7−xby core-level excitation

We report the first observations of synchrotron-radiation-induced, photon-stimulated desorption (PSD) of a neutral molecule (${\mathrm{O}}_2$) from a surface by core-level excitation. The PSD yield of ${\mathrm{O}}_2$ from $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-x}$ was monitored as a function of photon energy in the range 60-140 eV; thresholds were observed corresponding to excitation of $\mathrm{Cu}\mathrm{}\left(3p\right)\mathrm{}$ and $\mathrm{Ba}\mathrm{}\left(4d\right)\mathrm{}$ core levels. Production of ${\mathrm{O}}_2$ at the $\mathrm{Cu}\mathrm{}\left(3p\right)\mathrm{}$ edge involves excitation of shake-up or electron correlation states, while PSD at the $\mathrm{Ba}\mathrm{}\left(4d\right)\mathrm{}$ edge appears to involve excitation of localized ${\mathrm{Ba}}^{2+}$ states.