Knowledge Bank

A study of the low-temperature infrared spectra of varyingly deuterated mulls of lithium sulfate monohydrate has afforded information as to the nature of vibrations of water molecules causing infrared absorptions. Using intra- and intermolecular force constants, obtained from the data of doublet spectra, spectra of intermolecularly coupled species were predicted and compared with experiment. The agreement between calculated and observed spectra, is good, but not perfect. This indicates that non-neighbor interactions are weak but significant in determining the nature of the stretching modes involving water molecules in $Li2SO4\cdot H2O$. Furthermore, it is shown that the intermolecular interactions involving water molecules are mostly dipolar in origin.