LuminescenceR-line spectrum of ruby crystals shocked to 125 kbar along the crystalcaxis

The ruby luminescence R-line spectrum has been measured under shock wave, uniaxial strain compression along the crystal c axis. Because the compression is elastic for the stress range reported here, changes in the R-line spectrum are reversible upon unloading. The magnitude of the wavelength shift for the R lines under shock loading is comparable to that observed in hydrostatic loading, but there are measurable differences: the present data show a nonlinear change with density compression; the R₁-R₂ splitting decreases with increasing compression. The shock data, despite the strongly nonhydrostatic state of stress in the ruby, show no broadening of the R lines. A discussion of the observed behavior, under uniaxial strain, in terms of the point-charge ligand-field model is presented.