Absorption spectra of thin film of Rb2(Cd1-xZnx)I4 solid solutions

The exciton absorption spectra in thin films of Rb2(Cd1-xZnx)I4 solid solutions were investigated for the first time. It is established, that the spectra of the solid solutions correspond to the spectra of persistence type, and consist of two bands genetically descending from the initial bands of Rb2CdI4 and Rb2ZnI4 compounds. With allowance made for the lattice structure of the compounds it is shown that the concentration dependence of spectral position of exciton bands AI and AII is connected with the transfer of excitons between CdI4 and ZnI4 tetrahedrons along the axis b in the solid solutions. The experimental result is well conformed with the calculation of energy EAI(x) and EAII(x) on the basis of the theory similar to the theory of Davydov splitting of exciton bands in molecular crystals.