The pressure dependence of the ${}_{}{}^4{}_{}{}^{}$${\mathit{A}}_2$${\to }^4$${\mathit{T}}_2$ and ${}_{}{}^4{}_{}{}^{}$${\mathit{A}}_2$${\to }^4$${\mathit{T}}_1$ absorption bands of ruby have been studied to 35 GPa using a luminescence excitation technique developed for use at high pressure in the diamond anvil cell. The quasihydrostatic (Ar medium) pressure dependence of the zero-phonon lines, the crystal-field splitting parameter (Δ), and the Racah parameters B and C are determined. A significantly smaller variation of Δ is found for nonhydrostatic stress conditions for a ruby powder compact, and the implications of this on the pressure calibrations, lifetime measurements, and excitation of the R lines at high pressure are discussed.

• Received 6 September 1989

DOI:https://doi.org/10.1103/PhysRevB.41.5372