The possibilities for the extension of spectroscopy to two dimensions are discussed. Applications to nuclear magnetic resonance are described. The basic theory of two‐dimensional spectroscopy is developed. Numerous possible applications are mentioned and some of them treated in detail, including the elucidation of energy level diagrams, the observation of multiple quantum transitions, and the recording of high‐resolution spectra in inhomogenous magnetic fields. Experimental results are presented for some simple spin systems.

Two‐dimensional spectroscopy. Application to nuclear magnetic resonance

Copper Homeostasis and Neurodegenerative Disorders (Alzheimer's, Prion, and Parkinson's Diseases and Amyotrophic Lateral Sclerosis)

https://spin.niddk.nih.gov/bax/lit/508/32.pdf

Correlation of proton and nitrogen-15 chemical shifts by multiple quantum NMR☆

https://spin.niddk.nih.gov/bax/lit/508/16.pdf

Investigation of complex networks of spin-spin coupling by two-dimensional NMR

Computer-optimized decoupling scheme for wideband applications and low-level operation

When a nuclear spin system is subjected to a repetitive sequence of strong radiofrequency pulses, a steady state is established where there is a dynamic balance between the effect of the pulses and spin relaxation. Under certain readily satisfied pulse conditions, the deviation of the intensity of the free induction signal from its thermal equilibrium value is an exponential function of the pulse interval with time constant equal to the spin–lattice relaxation time. The determination is unaffected by spin–spin relaxation provided that the interval between pulses is long enough to permit all transverse components of magnetization to be eliminated, and provided precautions are taken to inhibit spin‐echo formation. Through Fourier transformation of the transient response, high resolution spectra with many component resonances may be studied, and the spin–lattice relaxation times of the individual lines determined. The technique lends itself particularly well to repeated accumulation of the transient signal for the purpose of improving sensitivity. It has been applied to the problem of determining the spin–lattice relaxation rates of the eight different carbon‐13 resonances in 3,5‐dimethylcyclohex‐2‐ene‐1‐one. The results span a range from 2.6 to 39 sec, and are in good agreement with those obtained by applying 180°–t–90° sequences to the same sample.

Fourier Transform Study of NMR Spin-Lattice Relaxation by "Progressive Saturation"

Proton-decoupled NMR. Spectra of carbon-13 With the nuclear overhauser effect suppressed

Phase and intensity anomalies in fourier transform NMR

A method is described for exciting a nuclear magnetic resonance spectrum with a radio frequency source having any desired frequency spectrum. The frequency spectrum of the source is first specified and then Fourier synthesized to define a function which is used to modulate a radio frequency carrier. The NMR spectrum is obtained by Fourier transforming the response of the spin system to this excitation. The technique is applied to the problem of suppressing a strong solvent line while simultaneously observing all other resonance lines in a spectrum and to homonuclear decoupling while observing a complete spectrum.

Fourier synthesized excitation of nuclear magnetic resonance with application to homonuclear decoupling and solvent line suppression

Dipole‐dipole interactions between protons in a glucopyranose derivative have been studied by means of the nuclear Overhauser effect and by spin‐lattice relaxation experiments. The Overhauser enhancement measurements utilize a new pulse technique which permits the saturating field to have any specified spectral density function so that finite frequency bands in the NMR spectrum can be irradiated. By this method, the dipolar interactions between the various pairs of protons are evaluated. In contrast, the dipolar relaxation of a chosen proton by all other protons in the sample has been determined by comparing the inversion‐recovery rates after selective and nonselective 180° pulses. The relaxation measurements indicate that the relaxation in this molecule is purely dipolar in origin. The Overhauser enhancement measurements of one proton are used to determine the contribution to its relaxation from two neighboring protons and, from these results, information about the geometry of the pyranose ring is evaluated.

Howard D. W. Hill

Papers

Fourier Transform Study of NMR Spin-Lattice Relaxation by "Progressive Saturation"

Proton-decoupled NMR. Spectra of carbon-13 With the nuclear overhauser effect suppressed

Phase and intensity anomalies in fourier transform NMR

Fourier synthesized excitation of nuclear magnetic resonance with application to homonuclear decoupling and solvent line suppression

Dipolar contribution to NMR spin‐lattice relaxation of protons