Spin-Echo Memory Device

A proton-rich sample placed in a strong inhomogeneous magnetic field of mean strength H0 was subjected to a pattern of relatively weak radio-frequency pulses at the Larmor frequency of the protons in the field H0. The pattern was then recalled by applying a strong rf pulse at a later time as in the spin-echo technique. It is shown both mathematically and experimentally that such a series of pulses, varying in amplitude can be ``memorized'' by the spin system of protons for times as long as one second and then repeated, preserving both shape and relative amplitude.