Abstract: In a method for NMR excitation of a sample, an Rf pulse is applied to an irradiation coil (6) proximate the sample, in the presence of an external DC magnetic field and an adiabatic passage is performed wherein the Rf pulse is controlled such that:B.sub.1 =V A sin 2.pi..nu.t and .DELTA.H=A(cos 2.pi..nu.t+s),orB.sub.1 =v A cos 2.pi..nu.t and .DELTA.H=A(sin 2.pi..nu.t+s),where s=S/A, where S is the frequency offset of a nucleus from the center of the spectrum, and where v allows for variation of B.sub.1 throughout the sample, .DELTA.H is the resonance offset of the nuclear spins, and B.sub.1 is the rf field of a spin-lock pulse.

Abstract: A method of obtaining a localized nuclear magnetic reasonance signal from a sample using a radiofrequency irradiation coil which provides an inhomogeneous radiofrequency field, comprisesapplying to the sample a plurality of radiofrequency pulse sequences, each pulse sequence including an excitation pulse, and at least two other pulses, the pulse sequences differing only in the phase of one or more of the said other pulses, and the phases of at least two of the said other pulses being shifted by 180.degree. in selected sequences of the said plurality, the number of sequences in the said plurality being such that a sequence exists for each possible combination of the said phase shifts for each of the said other pulses, and there being no sequences in the said plurality in which the phases of the said at least two of the said other pulses is shifted by 90.degree.,acquiring an N.M.R. signal after each pulse sequence,and combining the N.M.R. signals obtained to produce a localized N.M.R.

Abstract: In a method of operating a nuclear magnetic resonance (NMR) spectrometer in relation to a sample comprising two types of nuclei, a sequence of radiofrequency pulses and delay periods is applied using two different radiofrequency coils, one for each type of nucleus, each coil providing an inhomogeneous radiofrequency field, so that the two coils generate separate but overlapping sensitive volumes for each of the two types of nuclear species, whereby signal intensity is substantially limited to the overlap volume.

Abstract: A liquid sample comprising a system made up of two types of heteronuclei is pulsed in a particular manner in a nuclear magnetic resonance (NMR) experiment so that the resulting NMR signal from the one type of heteronucleus depends on the scalar-coupled interaction with the other type of heteronucleus. The sequence of radiofrequency pulses is such that the two types of heteronuclei interact via the phenomenon of polarization transfer and by the phenomenon of the correlated motion of the two types of heteronuclei in the transverse plane of the doubly rotating reference frame. The combination of these two phenomena in the one pulse sequence provides NMR signals which are easily made less dependent on the exact magnitude of the heteronuclear scalar coupling constant. The coupled NMR signals for polarization transfer from a system of multiple spin-half nuclei have multiplet components in the normal ratio. Consequently the pulse sequence provides an improved method for obtaining chemical structural information.