Molar fraction distributions of water molecule clusters of different number of intermolecular hydrogen bonds of thin film water have been studied by using a near-infrared high-brightness LED spectrometric system. Spectral assignment in the 970 nm region, attributing to five components of different number of hydrogen bonds of hexagonal fundamental water cluster structure, revealed a considerable molar fraction distribution change to each component. (C) 2002 Elsevier Science B.V. All rights reserved.