Cleaved natural orpiment (As₂S₃) by XPS

Orpiment (As₂S₃) is an arsenic ore mineral formed in low temperature hydrothermal veins and hotsprings, and commonly associated with other arsenic minerals such as realgar (AsS). It is of significance environmentally in areas affected by acid mine drainage where oxidation causes both the generation of acid and the release of arsenic in surface water and groundwater. The sample studied here is a natural crystal from Twin Creeks Mine, Nevada, which was fractured along the [010] cleavage plane under a dry nitrogen atmosphere before XPS analysis. General survey and high resolution spectra were collected using a Kratos Axis Ultra spectrometer under normal operating conditions. Adventitious carbon was used for energy referencing. Charge corrected binding energies for the photoelectrons emitted from orpiment (S 2s, S 2p, As 3p, As 3d, O 1s and C 1s) are reported. These binding energies are of use in experiments characterising the surface chemistry of orpiment providing insights into the reactivity of the mineral.