MAPPING MOLECULAR-ORIENTATION IN SOLIDS BY ROTATING-FRAME NQR TECHNIQUES

A multi-dimensional NQR technique to image both the spatial distributi on of quadrupolar nuclei and the local orientation of the electric fie ld gradient tensor at the quadrupole sites in solids is reported. The encoding procedure is based on the irradiation of the sample by a puls e sequence composed of spatially homogeneous and inhomogeneous radiofr equency fields. A method that encodes the spatial and orientation info rmation in the amplitudes of the free-induction decay signals and a pr oper three-dimensional reconstruction procedure that yields the space- orientation-dependent NQR spectra are described. A two-dimensional var iant allows rapid measurement of the spatially dependent orientation d istribution of molecules, disregarding the spectroscopic information, (C) 1998 Academic Press.