Dependence of R fluorescence lines of rubies on Cr (super 3+) concentration at various temperatures, with implications for pressure calibrations in experimental apparatus

The R fluorescence lines of rubies that contain 0.022, 0.068, 0.211, 0.279, 0.556, 1.221, and 1.676 wt% of Cr (sub 2) O (sub 3) were measured at temperatures of 100-600 K and at atmospheric pressure. The R (sub 1) line wavenumbers of all of the ruby samples shifted linearly as the temperature increased from 298 to 600 K at atmospheric pressure, and the temperature dependence increased from -0.157 + or - 0.001 cm (super -1) /K to -0.149 + or - 1.001 cm (super -1) /K as the Cr (sub 2) O (sub 3) content in the rubies increased from 0.022 to 1.676 wt%, which suggests a significant dependence on Cr (super 3+) concentration. At room temperature and atmospheric pressure, the full-width at half maximum (FWHM) of the peak height of the R lines also appears to be linearly related to the Cr (super 3+) concentration. The relative intensity ratios of the R (sub 2) to R (sub 1) lines (I (sub 2) /I (sub 1) ) of ruby samples with different Cr (super 3+) concentrations show several non-linear variations with temperature from 100 to 600 K, and the maximum values, (I (sub 2) /I (sub 1) ) (sub max) , occur near room temperature. The effect of Cr (super 3+) doping on the temperature dependence of the R line wavenumbers should be considered when rubies are used to calibrate the pressure or temperature in high-pressure and high-temperature experiments.