Theory of profiles of hydrogen stretching infrared bands of hydrogen-bonded solide. Multi-Fermi resonance effects and strong coupling between the high-frequency hydrogen stretching vibration and low-frequency phonons

摘要

A theory is developed to describe the profiles of hydrogen strelching infrared bands of hydrogen-bonded solids taking into account the anharmonic coupling between the high-frequency stretching vibration, v(XH), and low-frequency lattice phonons, #OMEGA#_i, as well as multi-Fermi resonances between states involving the v(XH) stretching and overtones or combinations of some internal modes. The theory has been constructed in the framework of the extended molecular exciton Davydov approach. Model calculations show that the strong couplings between the high frequency v(XH) and low-lattice vibration frequencies #OMEGA#_i, generate the broadness of the v(XH) band but the multi-Fermi resonances between the v(XH) state and overtones or combinations of internal modes generate the complicated substructure band which is observed experimentally.