EXPRESS: Two-dimensional Correlation Spectroscopy Studies of Infrared, Raman, and Near-infrared Spectra of Water

This review is concerned with our recent four papers on vibrational spectroscopy studies of water. The four papers had dual purposes. One was to deepen the understanding of IR, Raman and NIR spectra of water including the low-frequency regions of IR (far-infrared; FIR) and Raman spectra, and another was to explore the structure of water and water hydrogen-bonding networks. In this review we put emphasis on the former. Particularly, the importance of 2D-COS in the spectral analysis was explained in detail. In the studies of low-frequency region of IR spectra, 2D-COS revealed that there are two or three bands assignable to libration L2 modes of tetrahedron structure (THS) and pseudo-tetrahedron structure (PTHS). Bast on these observations we concluded that there are two or three water hydrogen bonding networks with THS or PTHS species. In the NIR study of water 2D-COS was used to construct the relations between PTHS and THS bands in the NIR spectra an those in the IR spectra. 2D-COS was also useful to determine the sequence order of the events occurring during temperature increase.