The presence of an inverted population of H↓ with very high electronic and nuclear spin polarization is confirmed with a new barometric-NMR method and by free-induction decay. With this new technique, the temperature dependence for the ratio of the two state-dependent recombination rate constants is measured. The rate of spin relaxation in the gas agrees with the latest theory, but relaxation on the surface is much faster than predicted, and there is an important surface one-body relaxation process.

• Received 21 October 1982

DOI:https://doi.org/10.1103/PhysRevLett.50.1137