SYNCHROTRON X-RAY PHOTOEMISSION AND REFLECTANCE STUDY OF THE DIPOLE FORBIDDEN DIAMOND CORE EXCITON

The diamond 1s core level absorption spectra measured with x-ray reflectance and partial photoelectron yield are compared. A steep rise and a feature around 290 eV in the partial yield are absent in the reflectance. This anomaly in the partial yield is due to the predominance of the Auger yield over the core exciton decay. A binding energy of 1.25 eV for a dipole forbidden core exciton is determined from these spectra. The spectral assignments of absorption features are revised, and discrepancies in diamond core exciton models are resolved.