DEUTERIUM CROSS-POLARIZATION MAGIC-ANGLE-SPINNING

In this publication a theoretical model is presented that describes cr oss-polarization magic-angle spinning (CPMAS) NMR experiments on a spi n system S(1)I-N, consisting of a set of N abundant homonuclear spins with I = 1/2 coupled to a single rare spin with S = 1. The spin evolut ion during this magic-angle spinning experiment is described using Flo quet theory. The model is an extension of the formalism that was recen tly introduced to describe CPMAS of S(1/2)I-N spin systems. First, exp erimental results of H-2 CPMAS experiments on partially deuterated dim ethyl sulfone and malonic acid are shown. The rotational-echo intensit ies of the H-2 free-induction-decay signals were monitored and plotted as a function of the difference between the intensities of the RF fie lds applied on the deuterons and the protons during the mixing rime. T hen the Floquet description of a spin system with S = 1 is presented i n order to enable the introduction of the Floquet model for CPMAS NMR. The Floquet Hamiltonian of the rotating quadrupolar spin is defined a nd the difference between spin locking in the rotating frame and in Fl oquet space is discussed, This is followed by a description of the spi n evolution of the S(1)I-N system during CPMAS experiments. The modifi ed Hartmann-Hahn conditions for these experiments are derived and a me thodology for calculating the cross-polarization S-spin signal intensi ties is demonstrated, The discussion is restricted to spin-1 nuclei wi th relatively small quadrupole interactions and is directed toward H-2 CPMAS. S-spin signal intensities as a function of mismatched Hartmann -Hahn conditions are evaluated for powder samples with quadrupolar fre quencies of 40 and 120 kHz. (C) 1996 Academic Press, Inc.