The method of the high-resolution pulse - nuclear resonance spectroscopy

摘要

In a method of high resolution pulsed NMR spectroscopy, the r.f. field is deliberately made inhomogeneous and a special pulse sequence is used to ensure that the received signals emanate predominantly from a selected region in a volume of the sample. Thus, the acquisition pulse (70) from which the FID signal (72) results, and which is applied in the presence of a main uniform static magnetic field, is preceded by a preparatory treatment involving at least one (typically 4-5) r.f. pulse(s) (66) being N pi pulses (N being integral) in respect of those nuclei of interest only in the selected region, each preferably followed by a d.c. pulse (68) giving rise to a magnetic field gradient superimposed on the main alignment field. The pulse 68 increases the amount of phase incoherence in unselected regions and is particularly useful when T2 is relatively large. Pulse 70 is typically a 30 DEG -90 DEG pulse. The static field may be non-uniform other than in the volume encompassing the selected region. The method may be used for 31P experiments. IMAGE