Effect of tension on R lines in ruby crystals shocked along crystal c axis

An experimental method has been developed to measure the wavelength shift of R lines in ruby samples subjected to well-defined, large tensile stresses. Plate impact experiments, conducted at 77 K, were used to produce uniaxial strain tension along the crystal c axis. Longitudinal stresses ranged from 105 kbar in tension to 110 kbar in compression. Both R lines remained sharp and showed a reversible, nonlinear blueshift in tension; the R1-R2 splitting increases with increasing tension. The observed data are in excellent agreement with predictions using crystal field theory [Sharma and Gupta, Phys. Rev. B 43, 879 (1991)]. The present results also permit an examination of the tensile response of sapphire at these large stresses.