Absorption spectra of thin films of the solid solutions Rb 2 ( Cd 1 − x Zn x ) I 4

The excitonic absorption spectra of thin films of the solid solutions Rb 2 ( Cd 1 − x Zn x ) I 4 have been studied for the first time. It is determined that the spectra of the solid solutions are stable and consist of two bands which genetically originate from the initial bands of the compounds Rb 2 Cd I 4 and Rb 2 Zn I 4 . It is shown on the basis of the structure of the crystal lattices of the compounds that the concentration dependence of the spectral position of the excitonic bands A I and A II is related with the transfer of excitons between Cd I 4 and Zn I 4 tetrahedra along the b axis of the solid solutions. The experimental result is in good agreement with the calculation of the energies E A I ( x ) and E A II ( x ) on the basis of a theory similar to the theory of Davydov splitting of excitonic bands in molecular crystals.