Optical Absorption and Photoluminescence of Cu‐Doped Alkali Halide Crystals

Absorption, excitation, and and emission spectra of KCl, KBr, and KI single crystals doped with Cu, are investigated in the spectral range from 200 to 1200 nm at temperatures from 77 to 700 °K. The absorption and excitation spectra of KBr:Cu at 77 °K show three bands centred at 210, 235, and 265 nm. Since the ratio of the intensities of the 210 and 235 nm bands to that of 265 nm band is remarkably constant for different Cu concentrations, the three hands be attributed to transitions occurring within a single centre. Optical excitation in each of these three absorption bands yields an emission spectrum showing only one band, centred at 392 nm (for KBr:Cu at 77 °K). The oscillator strength f for the 265 nm band is computed for 77 and 290 °K and found to be of the order of 6 × 10 −2 . Configurational curves for the emitter centre in KCl, KBr, and KI are obtained from the experimental data.