An adaptive scheme for measuring NMR spin-lattice relaxation times

Abstract A method is proposed for reducing the time required to determine spin-lattice relaxation times of individual lines in a high resolution NMR spectrum. The steady-state response of the spins to a repetitive sequence of 90° pulses is measured at two different pulse repetition rates, and the relaxation times derived from the ratio of the intensities of a given line in the two Fourier transformed spectra. The technique has been made the basis of an automatic program which adapts the pulse rate parameter in order to optimize the determination of the relaxation times. Applied to the carbon-13 spectrum of cortisone acetate the proposed method gives results in good agreement with those obtained by the widely used inversion-recovery technique. The spin-lattice relaxation times found for the methyl, methylene, methine and quaternary carbon atoms of cortisone acetate are found to fall into four quite distinct ranges.