Effect of Self-diffusion on the Ortho-para Conversion in Oxiygen Contaminated Solid Hydrogen

Abstract

When self-diffusion takes places rapidly in solid hydrogen contaminated with oxygen, the ortho-para conversion rate is enhanced. The ortho-concentration follows the diffusion equation including the effect of the oxygen; by finding the steady state solution of this equation and using values of the relaxation time, τ, associated with the self-diffusion, which were measured recently by Rollin and Watson, we can conclude that below 4°K the effect of the self-diffusion is negligible and above 8°K the self-diffusion is so rapid that it smoothes out the ortho-concentration around each oxygen molecule. The rate of ortho-para conversion above 8°K is calculated assuming a uniform ortho-concentration throughout the crystal.