This paper, published by Lawrence Berkeley National Laboratory in December 1967, presents a new method for measuring spin relaxation in complex systems. The authors, R. L. Vold, J. S. Waugh, M. P. Klein, and D. E. Phelps, describe a technique that avoids the issues of a complicated initial state and perturbation by measurement. The method involves using a non-selective 180° pulse followed by a 90° pulse, with the entire free induction decay recorded and Fourier transformed to obtain the partly relaxed spectrum. This allows for the analysis of the relaxation behavior of each line in the NMR spectrum, providing valuable information about molecular dynamics. The technique is demonstrated using a 1.5 x 10^-3 M solution of FeCl_3 in a 1:1 acetone-water mixture, showing that water protons relax more rapidly than acetone protons. The method can also be applied to measure differential transverse relaxation times and diffusion coefficients, making it useful for analyzing equilibrium spectra with overlapping lines. The work was supported by the Joint Services Electronics Program and the National Science Foundation, and performed under the auspices of the U.S. Atomic Energy Commission.This paper, published by Lawrence Berkeley National Laboratory in December 1967, presents a new method for measuring spin relaxation in complex systems. The authors, R. L. Vold, J. S. Waugh, M. P. Klein, and D. E. Phelps, describe a technique that avoids the issues of a complicated initial state and perturbation by measurement. The method involves using a non-selective 180° pulse followed by a 90° pulse, with the entire free induction decay recorded and Fourier transformed to obtain the partly relaxed spectrum. This allows for the analysis of the relaxation behavior of each line in the NMR spectrum, providing valuable information about molecular dynamics. The technique is demonstrated using a 1.5 x 10^-3 M solution of FeCl_3 in a 1:1 acetone-water mixture, showing that water protons relax more rapidly than acetone protons. The method can also be applied to measure differential transverse relaxation times and diffusion coefficients, making it useful for analyzing equilibrium spectra with overlapping lines. The work was supported by the Joint Services Electronics Program and the National Science Foundation, and performed under the auspices of the U.S. Atomic Energy Commission.