Piezoreflectance spectra of 1s Z12 exciton in CuBr.

We have investigated the piezoreflectance spectra (deltaR/R) of the 1s Z12 exciton in single crystals of copper bromide CuBr at the temperature of 95 K with linearly polarized light. The spectra were successively studied with the pressure p along the [001] and [111] axis and the wave vector k of the incident light parallel to the [110] direction. The shear deformation potentials b and d of the 1s Z12 exciton were deduced from the stress-induced shift and splitting.