S Matsui

An NQR imaging experiment on a disordered solid

This Communication reports the first NQR imaging experiment on quadrupolar nuclei in a powdered solid

Fast imaging of the second moment using magic echo trains.

Approaches are discussed to imaging of the second moment of proton NMR dipolar spectra. Two methods are proposed using the peak shapes of the magic echo trains for evaluation of the second moment. One is a quasi-multidimensional FT approach where the peak shapes of the magic echoes are spatially resolved, and the other is the fast version of the former approach, collecting the same data in a much shorter measurement time. Preliminary results of spatially 2D, as well as 1D, experiments are reported.

Spatially selective excitation in solid-state NMR by off-resonance spin tipping

Abstract A simple and efficient technique for spatially selective excitation of proton NMR in solids is described. The technique is based on selective saturation resulting from repeated off resonance RF tipping of protons under an applied field gradient, with a suitable dipolar dephasing interval inserted between the tippings. The tip angle about the effective field is adjusted to integral multiples of 2π at the magic angle in the rotating frame. This permits the selective preparation of longitudinal magnetization of those protons which satisfy the magic-angle condition, without significant loss of magnetization due to the dipolar couplings. Computer simulations illustrate the applicability of the technique. An experimental example of the excitation profile is presented by directly monitoring the selectively prepared longitudinal magnetization with the magic-sandwich-echo high-resolution imaging sequence.

Self-refocused slice selection by magic echo DANTE with 270° flipping Gaussian RF modulation

The method of slice selection proposed for solid-state MRI by combining DANTE selective excitation with magic echo (ME) line narrowing requires a rephasing period ca. 0.6 times the DANTE excitation period. The added rephasing period results in a significant loss of sensitivity due to transverse relaxation. To solve the sensitivity problem, we make use of the self-refocusing effect of the 270 degrees Gaussian-shaped soft pulse by introducing a 270 degrees flipping Gaussian modulation to the ME DANTE method. This eliminates the rephasing period. The utility of the improved method is demonstrated by experiments performed on test samples of adamantane and polycarbonate.