THE ORTHO–PARA CONVERSION OF HYDROGEN AND DEUTERIUM ON INHOMOGENEOUS PARAMAGNETIC SURFACES

Abstract

The kinetics of the magnetic ortho–para conversion of hydrogen and deuterium on neodymium oxalate and hemin crystals has been determined over a wide temperature range in a static system. In these cases a similar type of rate curve is obtained: at high and at low temperatures the rate decreases with temperature, while in the intermediate region the rate increases with temperature. The behavior is explained in terms of an energetic surface heterogeneity. In case of neodymium oxalate two distinctly different groups of sites appear to be active having energy barriers to migration of the adsorbed hydrogen at considerably different height. The conversion mechanism of the "trapped" gas is assumed to be similar to the mechanism in liquids where repeated collisions are also assumed to occur.