Excitation spectra of the 4.44-eV intrinsic luminescence in a single crystal of Ca${\mathrm{F}}_2$ at liquid-nitrogen temperature was measured using synchrotron radiation in the x-ray region. The intrinsic luminescence at 4.44 eV is due to self-trapped exciton recombination. The intensity of the emitted uv light was measured as a function of the x-ray photon energy from below the calcium $K$ edge to 200 eV above the edge. Dips were observed in the luminescence excitation spectrum corresponding to peaks in the absorption coefficient both in the core excitation region near the edge and in the region of excitation to the continuum far above the edge. The effect is correlated with modulation of the radiative recombination probability of the core hole. The close relationship between the inverse of the luminescence yield and the extended x-ray absorption fine structure (EXAFS) after background subtraction shows that excitation spectra of uv luminescence can be used to measure EXAFS in thick single crystals and biological samples with suitable luminescence centers.

• Received 26 July 1977

DOI:https://doi.org/10.1103/PhysRevB.17.2021