Molecular Transfer of Nonequilibrium Nuclear Spin Magnetization

A new magnetic resonance technique has been developed to measure the rates of fast molecular processes. The method involves the experimental introduction of a nonequilibrium nuclear magnetization in one system A, and the subsequent measurement of the rate at which rapid molecular processes transfer this nonequilibrium magnetization to a second system B. Systems A and B may correspond to different chemical sites in a molecule that give rise to a chemical shift, or to sites that are distinct because of electron coupled spin-spin interaction. This technique has been applied to determinations of the rate of proton exchange between ammonium ions in aqueous solution.