Abstract
This chapter discusses homo- and heteronuclear experiments and includes multiple resonance work. Several programs have been made available for multiple resonance experiments, including one for the calculation of internuclear double resonance (INDOR) spectra, which can assist in the interpretation of double-resonance experiments aimed at giving the relative signs of coupling constants. The spin-Hamiltonian approach has also been used in the calculation of the two-dimensional spectra given by some representative spin systems. Most of the earlier theoretical work on multiple resonance used either the Bloch equations or the spin-Hamiltonian. Meakin and Jesson used the Bloch equations in part of their work on the computer simulation of multiple-pulse experiments. They found that this approach was efficient for the effect upon the magnetization vector of any sequence of pulses and delays in weakly coupled spin systems. However, relaxation processes and tightly coupled spin systems cannot be dealt with in this way and require the use of the density matrix. Major applications have included the calculation of the complete double resonance spectrum from an AX spin system, which gives 12 transitions in all; an extremely detailed study of the relaxation behavior of the AX systems, provided by 1,1,2-trichloroethane and 2,2-dichloroethanol; the effects of gating and of selective and nonselective pulses on AB and AX spin systems and the importance of the time evolution of the off-diagonal elements of the density matrix in repetitively pulsed Fourier-Transform (FT) NMR and spin-echo work; the use of double resonance to sort out relaxation mechanisms and transient responses ; the calculation of general multiple resonance spectra; and triple resonance studies of relaxation in AB and AX spin systems.
Published Version
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