Optical properties of the chalcopyrite semiconductors ZnGe${\mathrm{P}}_2$, ZnGe${\mathrm{As}}_2$, CuGa${\mathrm{S}}_2$, CuAl${\mathrm{S}}_2$, CuIn${\mathrm{Se}}_2$, and AgIn${\mathrm{Se}}_2$

The reflectivities at 80 K of the chalcopyrite semiconductors CuGa${\mathrm{S}}_2$, CuAl${\mathrm{S}}_2$, CuIn${\mathrm{Se}}_2$, AgIn${\mathrm{Se}}_2$, ZnGe${\mathrm{P}}_2$, and ZnGe${\mathrm{As}}_2$ were measured in the energy range from 2 to 26 eV using sychrotron radiation. Occupied and unoccupied electronic states are described with the aid of the sharp reflectivity features from $d$ levels and of the electronic spectrum from an ESCA spectrometer.