Hydrophobic solvation, quantum nature, and diffusion of atomic hydrogen in liquid water

The nature of atomic hydrogen in liquid water is discussed with respect to solvation and diffusion. The picture that emerges is that of a hydrophobic solute akin to molecular hydrogen, with a large negative entropy of solvation. The atoms populate cavities with a free diameter of the order of 0.5 nm, and with a dynamic, clathrate-like structure. The density of states of the atoms in these cages is sufficiently low to reveal their quantum nature in isotope effects on hyperfine couplings and on diffusion coefficients.