Antiresonances in the fundamental spectra of CdI2-4H and CdBr2-6R crystals

On the basis of the low temperature spectra measured for CdI2 (4H-polytype) and CdBr2 (6R-polytype) crystals in the region of UV radiation in the exciton resonance vicinity the distinct antiresonance are discovered. The exciton interaction with the continuous spectrum corresponding to interband transitions is determined to cause a self-ionization and a band widening. That is the Fano effect manifestation. The exciton dynamical instability in the cadmium dihalide crystals is shown to be caused by energy and structure pecularities. According to the analysis of the absorption curve profiles and antiresonances parameters and types at T = 77 K the matrix element values of the exciton state hybridization with the continuous spectrum states are obtained. A significant dispersion of the antiresonance parameter being caused by the complex structure of the valence bands in cadmium dihalide is discovered. (author)