Evidence for an Optical Transition at a Noncentrosymmetric Point of the Brillouin Zone in Ki

Abstract

The two-photon absorption spectrum of KI has been measured to 7.5 eV. The region studied spans the spectral range in which all the prominent one-photon absorption peaks reside. Our two-photon data exhibit two noticeable peaks at 7.21 and 7.375 eV. Based on the parity argument and polarization dependence, we tentatively assign the peak at 7.21 eV to a ${\Delta }_6\to {\Delta }_6$ transition.