Fourier transform studies of nuclear spin relaxation
The transient response to a radiotrequency impulse is known to be the Fourier transform of the slow-passage nmr spectrum. In high resolution nmr spectroscopy the Fourier transform method represents a considerable acceleration of the rate of acquiring data from samples with many component lines, and when coupled with time-averaging techniques, it provides a significant enhancement in spectrometer sensitivity. The improved time resolution of this technique can be exploited to monitor dynamic nmr phenomena such as chemical exchange or spin relaxation effects. Spin—lattice relaxation times of the individual lines of a high resolution spectrum have been studied by the inversion-recovery method and by the Fourier transform analogue of progressive saturation. Spin—spin relaxation measurements utilize the spin-echo pulse sequence of Can and Purcell or the forced transitory precession technique of Solomon. In each case the experiment is done under complete computer control and the results are presented in the form of a 'three-dimensional' diagram of intensities as a function of frequency and elapsed time.