Band structure of lead sulphide

The band structure of lead sulphide has been investigated using angle-resolved photoemission, with synchrotron radiation in the photon energy range 25-95 eV as the excitation source. Many spectral features originate from direct transitions, while others are due to 'density of state' features, i.e. they arise from electrons scattered into the observation direction. Good agreement was found between the experimental spectra and transitions expected on the basis of the calculated linearized muffin-tin-orbital (LMTO) band structure and free electron final states. Partial yield spectra at the Pb O4,5 edge are also reported, from which it is concluded that the exciton energy in lead chalcogenides is not anomalously large, in contradiction to previous work.