Effect of Anisotropic Hyperfine Interactions on Paramagnetic Relaxation in Liquids

Abstract

A simple ``microcrystalline model'' is developed to discuss the effect of molecular motion in the liquid state on the paramagnetic relaxation of ions or molecules with spin S = ½. This theory relates the paramagnetic relaxation times T1 and T2′ to the anisotropy in g, Δg = gII — g⊥, to the anisotropy in the nuclear hyperfine interaction, A–B, and to the correlation time τc which describes the Brownian tumbling motion of the microcrystal in the liquid state. The contribution of the anisotropic hyperfine interaction to the paramagnetic relaxation turns out to depend on the nuclear spin quantum number Iz, so that different hyperfine multiplets in a paramagnetic resonance spectrum can show different line widths.