Piezoreflectivity Studies on the Reflectivity Structures at about 8.6 eV in KBr

Piezoreflectivity spectra of KBr were measured by using uniaxial stresses in the photon energy region where a reflection band made up of three structures at 8.2, 8.6 and 8.9 eV is observed. From the dichroism observed under trigonal distortions, it is concluded that the structures at 8.2 and 8.9 eV are the transitions at the L point. The conclusion is different from those of Onodera et al. who have assigned the structures to the transitions at the X point. The trigonal deformation potentials of these structures at 8.2 and 8.9 eV are determined to be 0.32±0.12 eV and 0.58±0.06 eV, respectively, and tentative assignments of the initial and final states of the transitions are proposed.