On the Thermal Spectra of Ruby and Sapphire

Abstract

The temperature dependence of the thermal spectra (in the range from 0.4 to 8 μm) of ruby and sapphire single crystals heated by a 10.6-μm cw electric-discharge CO₂ laser has been experimentally and analytically investigated. The shape of the background of the spectral lines of impurity Cr³⁺ ions in ruby corresponds to the short-wavelength tail of sapphire thermal radiation. The Planck thermal spectrum of sapphire is interpreted in terms of the interaction between electrons and lattice ions in the conduction band.