Theoritical study on an anomalous isotopic effect on the position and integrated intensity of the ir stretching vibration band for medium-strong and strong hydrogen bonds

Abstract

Anomalous isotopic effects on the position and the integrated intensity of the v(XH) stretching vibration band of hydrogen-bonded systems have been studied by applying standard methods of non-equilibrium statistical mechanics. It has been shown that the calculations of the two first spectral moments reduce to that of analysing a one-dimensional quantum mechanical model of the X-H vibrator in an average force field in the condensed phase. Extensive numerical calculations have been carried out taking into account mechanical and electrical anharmonicity, respectively. It has been shown that observed anomalous isotopic effects can be explained on the basis of anharmonicity of the X-H vibrator engaged in the hydrogen bond. Finally, general relations for the temperature dependence of the first two spectral moments have been obtained and discussed.