Temperature dependence of fluorescence spectra from x-ray-excited single-crystal CaF2:Mn(x) (x=0.1, 1.0, 3.0 at. %)


Fluorescence spectra of x-ray-excited single-crystal CaF2:Mn were methodically measured with a silicon-diode array at intervals over the temperature range of 13670 K for samples with 0.1-, 1.0-, and 3.0-at. % Mn concentration. All spectra exhibited a non-Gaussian broadband emission skewed to the high-wavelength side and centered near 500 nm. The full width at half maximum increased with temperature from approximately 0.18 to 0.31 eV, with slight variation between the three samples. A fit of these data to the well-known expression for the full width of an emission band as a function of temperature, W(T)=W(0)[coth(Latin small letter h with stroke/2kBT)] 1/2, yielded values of approximately 0.20 eV for W(0), and 7.4×1013 sec-1 for the excited-state vibrational frequency. However, this functional form does not adequately describe these data over an extended temperature range. The centroid of the distribution for all concentrations shifted 3.9 6.4 nm toward shorter wavelengths as the temperature increased from 13 to 375 K, then shifted 0.9 2.1 nm toward longer wavelengths as the temperature rose to 670 K. From 13 to approximately 325 K, the area of the spectral distribution increased by a factor of 2 4. With further temperature increase the area quenched to less than 5% of its maximum value. From the data for each concentration an activation energy for thermal quenching was extracted. These values were found to be 1.27, 0.91, and 0.91 eV for samples with 0.1-, 1.0-, and 3.0-at. % Mn concentration. Spectral analyses showed that a decrease of Mn concentration was accompanied by an increase in skewness and a decrease in centroid wavelength. © 1985 The American Physical Society.

Publication Title

Physical Review B