Low temperature photoemission study of La2CuO4+x single crystals

New angle-resolved photoemission results obtained using synchrotron radiation of 15–40 eV from cleaved La2CuO4+x single crystals at a temperature of about 30 K are presented. We have observed spectral enhancements at photon energies around 17 eV that are consistent with autoionization resonance excitations of the hybridized La 5p-O 2s states to O 2p empty states. The crystal surface was found to be unstable. A broad feature around 5 eV binding energy that could be caused by surface reconstruction was observed.