Spatially resolved NMR and NQR in solids

Abstract

Three methods are reported which combine NMR or NQR spectroscopy in solids with spatial information. First, an NMR method for imaging of spectral parameters of solid samples is presented. The detected signals are Jeener-Broekaert echoes. No read gradient is applied during the acquisition, so that wide-line spectral parameters can be evaluated and be transferred to image contrasts. The imaging principle is a pure phase-encoding Fourier transform technique. While switching the gradients off, the encoded information is conserved in the dipolar (or quadrupolar) order state. Second, an NQR imaging procedure is suggested in analogy to NMR rotating frame zeugmatography. No magnetic field gradients are used at all and the full spectroscopic information is accessible. The required gradients of the radio-frequency amplitude can be produced by surface coils. The procedure then provides depth resolution in a range of the order of the coil radius. The technique is particularly suitable for the indirect detection of gradients of physical parameters like stress or pressure and temperature. Third, a technique is reported permitting image-guided localized NMR spectroscopy in solid materials. The principle is the LOSY single-scan sequence using three slice-selective spin-lock pulses corresponding to the three space directions. The method is expected to be useful for the localized characterization of materials. As an example, the determination of the orientation of polymer fibers is demonstrated.