RUBY SPECTRAL BAND-PROFILE ANALYSIS FOR TEMPERATURE SENSING

The spectral band profiles of the EBAR --> 4A2g and 2ABAR --> 4A2g tra nsitions of CR3t in Al2O3, i.e., the commonly known ruby 6943 angstrom (R1) and 6929 angstrom (R2) emission lines, in the temperature range 10-300 K were recorded and deconvoluted numerically with excellent acc uracy into a Lorentzian (homogeneous) component and a Gaussian compone nt. The Gaussian width was taken as arising from sample inhomogeneity and spectrometer slit function, and as expected was found to be indepe ndent of temperature. The Lorentzian width was found to vary with temp erature in accordance with the two-phonon relaxation processes reporte d previously, plus a thermal broadening process. While the former proc esses were quenched completely as temperature was lowered to about 90 K, the latter process, describable with the Debye-Waller factor, still caused a Lorentzian width of about 0.2 cm-1 (for both R1 and R2 lines ) which then leveled out quickly to about 0.1 cm-1 as the temperature was lowered further. For temperature above 100 K, the positions of the R1 and R2 lines were found to have the same temperature dependence as that reported previously. The use of the temperature dependencies of Lorentzian width and line position for temperature sensing was discuss ed; such an instrument could indeed be made portable because of the si mple optical and electronic systems used in our experiments.