The paper "Measurement of Spin Relaxation in Complex Systems" by R. L. Vold, J. S. Waugh, M. P. Klein, and D. E. Phelps, published on December 15, 1967, describes a new method for measuring spin relaxation in complex systems. The method avoids two major problems in previous experiments: a complicated initial state and perturbation from measurement. The initial state is established using a non-selective 180° pulse, followed by a non-selective 90° pulse and recording the free induction decay. The Fourier transform of this decay provides the partly relaxed spectrum, which reveals the full unperturbed relaxation behavior. The method is applied to a 1.5 × 10⁻³ M solution of FeCl₃ in equal volumes of acetone and water, showing that water protons relax more rapidly than acetone protons. The method is also useful for analyzing equilibrium spectra with overlapping lines. The procedure can be used to measure differential transverse relaxation times and differential diffusion coefficients. A Carr-Purcell pulse sequence produces spin echoes, which can be Fourier transformed to reveal partially relaxed spectra. The method of determining diffusion coefficients using pulsed field gradients can be combined with the Fourier transform method to measure diffusion coefficients of chemically shifted species. 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. The paper references several previous studies and includes a figure showing the longitudinal proton relaxation surface for the FeCl₃ solution. The report was prepared as an account of government-sponsored work and includes a disclaimer regarding the accuracy and completeness of the information.The paper "Measurement of Spin Relaxation in Complex Systems" by R. L. Vold, J. S. Waugh, M. P. Klein, and D. E. Phelps, published on December 15, 1967, describes a new method for measuring spin relaxation in complex systems. The method avoids two major problems in previous experiments: a complicated initial state and perturbation from measurement. The initial state is established using a non-selective 180° pulse, followed by a non-selective 90° pulse and recording the free induction decay. The Fourier transform of this decay provides the partly relaxed spectrum, which reveals the full unperturbed relaxation behavior. The method is applied to a 1.5 × 10⁻³ M solution of FeCl₃ in equal volumes of acetone and water, showing that water protons relax more rapidly than acetone protons. The method is also useful for analyzing equilibrium spectra with overlapping lines. The procedure can be used to measure differential transverse relaxation times and differential diffusion coefficients. A Carr-Purcell pulse sequence produces spin echoes, which can be Fourier transformed to reveal partially relaxed spectra. The method of determining diffusion coefficients using pulsed field gradients can be combined with the Fourier transform method to measure diffusion coefficients of chemically shifted species. 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. The paper references several previous studies and includes a figure showing the longitudinal proton relaxation surface for the FeCl₃ solution. The report was prepared as an account of government-sponsored work and includes a disclaimer regarding the accuracy and completeness of the information.