THEORY OF PROFILES OF HYDROGEN STRETCHING INFRARED BANDS OF HYDROGEN-BONDED SOLIDS - MODEL OF STRONG-COUPLING BETWEEN THE HIGH-FREQUENCY HYDROGEN STRETCHING VIBRATION AND LOW-FREQUENCY PHONONS

A theory is developed to describe a broad IR absorption which appears in the range of a high-frequency stretching vibration of the X-H group involved in the hydrogen bond in solids. The theory is based on the a nharmonic coupling mechanism between the high-frequency hydrogen stret ching vibration. nu(XH), and low-frequency lattice phonons. The theory was constructed in the framework of the molecular exciton Davydov app roach. Model calculations show that the strong anharmonic couplings be tween the high-frequency nu(XH) and low lattice vibration frequencies generate the broadness of the nu(XH) band.