Isotope and temperature effects on the hyperfine interaction of atomic hydrogen in liquid water and in ice

The Fermi contact hyperfine interaction of hydrogen isotopes in liquid and solid water is below the vacuum value, shows a mass dependence, and has a negative temperature coefficient in the liquid. Furthermore, it shows a pronounced solvent isotope effect in H2O/D2O mixtures. This behavior is analyzed in terms of Dalgarno–Lewis perturbation theory for the atom in a spherical parabolic solvent potential and with a phenomenological model for spin delocalization onto solvent molecules. The results support previous suggestions that hydrogen atoms induce clathrate-like cages in liquid water. These may resemble the static structures of noble gas clathrates except that they are of transient dynamic nature in liquid water.