This work has been digitalized and published in 2013 by Verlag Zeitschrift für Naturforschung in cooperation with the Max Planck Society for the Advancement of Science under a Creative Commons Attribution 4.0 International License. Dieses Werk wurde im Jahr 2013 vom Verlag Zeitschrift für Naturforschung in Zusammenarbeit mit der Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. digitalisiert und unter folgender Lizenz veröffentlicht: Creative Commons Namensnennung 4.0 Lizenz. Quadrupole Nutation NMR in Solids * W. S. Veeman Nijmegen SON Research Center for Molecular Structure, Design and Synthesis, University of Nijmegen, Nijmegen, The Netherlands Z. Naturforsch. 47a, 353-360 (1992); received July 18, 1991 The nutation frequency of a quadrupolar spin I depends on the quadrupole interaction. From nutation spectra, therefore, one obtains information about the direct surrounding of the atom. The theory of the straightforward and of more complicated nutation NMR experiments is outlined. Two applications of nutation NMR, to 23 Na in zeolites and 27 A1 in alumina, are shown. In this way in CaO  6 A1 2 0 3 penta-coordinated aluminum has been detected. I. Introduction Nuclei with a nuclear spin quantum number / greater than 1/2 possess an electrical quadrupole moment that can interact with electric field gradients existing at the nucleus. This electric quadrupole inter- action can provide valuable information about the local structure in solid materials where the electric field gradients arise from the charges surrounding the nucleus. The determination of the parameters describ- ing the quadrupole interaction is traditionally the field of nuclear quadrupole resonance, NQR, and although NQR has many advantages, in many cases the one disadvantage is the low sensitivity of the experiment for nuclei with small quadrupole moments. Several techniques have been invented in the past to circumvent this problem, especially by combination with the NMR experiment in a high magnetic field. A recent example of this combination is the zero-field NMR experiment where the evolution of the spins after excitation is studied with the sample outside the magnet while the signal is detected in the magnet [1]. In a normal NMR experiment of a quadrupole spin the price one pays for the relatively high sensitivity is a broadening of the NMR line due to the anisotropy of the quadrupole interaction of a spin in a magnetic field. At this point we should distinguish the quadrupole line broadening of spins with integer spin quantum * Presented at the Xlth International Symposium on Nuclear Quadrupole Resonance Spectroscopy, London, United Kingdom, July 15-19, 1991. Reprint requests to Prof. W. S. Veeman, Physikalische Chemie, Universität-GH-Duisburg, Lotharstrasse 1, 4100 Duisburg, BRD. number I and half-integer /. When the quadrupole interaction is appreciably smaller than the interaction of the spin with the magnetic field (i.e. for strong fields or small quadrupole interactions), then for half-integer spins the Am = 1 transition between the Zeeman states m = 1/2 and m'= —1/2 is broadened by second-order quadrupole interaction only [2], while in all other cases, for integer and half-integer spins, all Am = 1 transitions are broadened in first order. In many prac- tical cases this means that it is relatively easy to mea- sure the 1/2 <-> — 1/2 transition of half-integer spins, but that at the same time the determination of the quadrupole parameters from this broadened line is difficult or inaccurate due to the presence of other line broadening interactions. Some of these interactions may be eliminated by magic angle spinning, but the width of the quadrupole 1/2-<-+ — 1/2 powder spec- trum is then also further reduced. Here we want to discuss a technique, nutation NMR, proposed by Samoson and Lippmaa [3], where in a two-dimensional NMR fashion the effect of the quadrupole interaction is separated from other line broadening interactions, thereby increasing the infor- mation content of the spectra. The theory will be dis- cussed for stationary samples, but later the effect of magic angle spinning will be considered. II. Theory The two-dimensional nutation NMR experiment is schematically indicated in Figure 1. During the evolu- tion period in the two-dimensional NMR experi- ment the spins are subjected to a resonant rf field of strength a> l = yB x and phase x. During this pulse in a frame rotating around the static external field the 0932-0784 / 92 / 0100-0353 $ 01.30/0. - Please order a reprint rather than making your own copy.