Decomposition of water Raman stretching band with a combination of optimization methods

Abstract

In this study, an investigation of the behaviour of stretching bands of CH and OH groups of water–ethanol solutions at alcohol concentrations ranging from 0 to 96% by volume has been performed. A new approach to decomposition of the wide structureless water Raman band into spectral components based on modern mathematical methods of solution of inverse multi-parameter problems–combination of Genetic Algorithm and the method of Generalized Reduced Gradient–has been demonstrated. Application of this approach to decomposition of Raman stretching bands of water–ethanol solutions allowed obtaining new interesting results practically without a priori information. The behaviour of resolved spectral components of Raman stretching OH band in binary mixture with rising ethanol concentration is in a good agreement with the concept of clathrate-like structure of water–ethanol solutions. The results presented in this paper confirm existence of essential structural rearrangement in water–ethanol solutions at ethanol concentrations 20–30% by volume.