Diffusion and nuclear magnetic relaxation ofH2in rare-gas liquids

Abstract

Pulsed NMR has been used to study ${\mathrm{H}}_2$ as a dilute impurity in the rare-gas liquids neon, argon, and krypton. ${\mathrm{H}}_2$ diffusion was measured and is compared to the somewhat smaller self-diffusion of the hosts. The temperature dependences of the impurity and host diffusions are the same (and nearly Arrhenius) in the cold liquids. At temperatures approaching the critical temperature, the impurity diffusion is a more rapidly increasing function of temperature than is the host diffusion. The ${\mathrm{H}}_2$ impurity diffusion is compared with predictions of molecular dynamics. Proton relaxation times $T_1$ and $T_2$ also were measured and are compared with proton relaxation measurements in gaseous dilute ${\mathrm{H}}_2$-rare-gas mixtures, and in dilute ortho-${\mathrm{H}}_2$-para-${\mathrm{H}}_2$ fluid mixtures. The relaxation results are compared with some predictions of the theory of Bloom and Oppenheim.