Knowledge Bank

The spectroscopic study of clathrate hydrates of small polar molecules have been greatly simplified since the development of methods for their preparation based on the vacuum codeposition of water with guest molecules at cryogenic temperatures. However, these methods have not proved directly adaptable to nonpolar guest molecules, presumably because of much longer structural-relaxation times of such hydrates. The continued development of the cryogenic methods has revealed that nonpolar-guest hydrates will grow quite readily epitaxially to the clathrate hydrates of certain polar molecules. Spectra for epitaxially grown structure I and structure II clathrate hydrates of $CO2$ will be discussed and the dependence of the growth on the nature of the clathrate substrate will be examined in terms of the role that point-defect activities play in the formation of icy solids