DOUBLE-QUANTUM CROSS-POLARIZATION BETWEEN HALF-INTEGER QUADRUPOLAR SPIN SYSTEMS - B-11[--]NA-23 AND B-11 [--] AL-27

Cross-polarization/magic angle spinning (CPMAS) experiments are report ed in which both the source and recipient spin systems an based on hal f-integer nuclei with strong second-order quadrupolar interactions. Do uble-quantum (DQ) CP is particularly well suited for this purpose, as demonstrated with B-11{Na-23} CPMAS spectra of sodium diborate. Furthe rmore, a two-dimensional B-11{Al-27} heteronuclear correlation spectru m is obtained on a magnesium aluminoborate glass, demonstrating prefer ential connectivities among various distinct boron and aluminum sites. Novel spectral editing opportunities arise from semi-selective cohere nce transfer rates measured by exploiting off-resonance effects on spi n-locking efficiencies. (C) 1998 Elsevier Science B.V. All rights rese rved.