The optical reflectance spectra of alkali halide crystals KI and RbI were measured over the energy range of 4.14 to 6.91 eV. Both single crystal and poly-crystal samples were used to accomplish this task. The phase
was computed using the Kramers-Kronig relation between the real and imaginary parts of the complex function,
. Subsequently, the optical constants n
were determined from the Fresnel reflectivity equation. The real and imaginary parts of dielectric constants
were then calculated using n
. The optical absorption spectra of the crystal have also been measured in these spectral regions. The spectra agree reasonably well with the current theory concerning exciton peaks. In addition, a shoulder was found in the spectra similar to those previously seen and associated with the band-to-band transition in the alkali iodides.
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