Gas effusion spectra of HgBa2CuO4+delta

Gas effusion spectra have been obtained in the temperature range 30-1000 degrees C for underdoped, optimized, and overdoped HgBa2CuO4+delta samples. We observe a large oxygen multipeak structure at high temperatures and a wide low-intensity oxygen ''tail'' at lower temperatures. The two lowest-temperature oxygen peaks are believed to originate from bonding sites for excess oxygen. The delta values derived from these two peaks are consistent with delta values derived from neutron powder diffraction (NPD) The wide low-temperature oxygen tail im the effusion spectra suggests the existence of loosely bound disordered oxygen in overdoped samples and accounts for the discrepancy between delta values determined by NPD and thermogravimetry analysis. Our results provide further evidence that each doping oxygen atom contributes, on average only about one carrier to the CuO2 plane in HgBa2CuO4+delta.