THEORY OF ORTHO-PARA HYDROGEN CONVERSION CATALYZED BY D-ELECTRONS

A new ortho-para conversion mechanism is suggested as a substitute for Wigner's which yields theoretical rates often more than two orders of magnitude smaller than the experimental ones. This mechanism is illustrated for catalysts composed of transition metal magnetic impurities dispersed on a diamagnetic surface. It relies on the hyperfine contact between surface electrons and adsorbed H2 protons. As the catalyst and molecule electron clouds overlap appreciably, even in the molecular physisorbed states, the surface electrons share both "s" and "d" characters allowing a stronger contact with the H2 protons. © 1990.