NUCLEAR-RELAXATION DURING THE FORMATION OF H-2 FROM SPIN-POLARIZED HYDROGEN

We report an NMR study of solid H-2 formed by the recombination of dou bly polarized atomic hydrogen at a temperature of approximately 0.3 K. The molecules are formed in a highly excited ortho state with M(I) = -1, thermalize through collisions with the He-4-coated walls of the co ntainment chamber, and form a solid. The solid is essentially pure ort ho H-2 in the fcc phase, as expected. However, the nuclear polarizatio n is close to zero, in contrast to the value of -1 if there was no rel axation, and +0.034 if the spin temperature was in equilibrium with th e surface of the cell. Possible mechanisms for depolarization are disc ussed, though no plausible explanation for the loss has yet been found .