Ee. Ylinen et al., DOUBLE-QUANTUM COHERENCE OF QUADRUPOLAR I=1 NUCLEI - N-14 IN NH4CLO4, Solid state nuclear magnetic resonance, 10(1-2), 1997, pp. 25-31
We have calculated optimal conditions for observing the double quantum
coherence of quadrupolar nuclei I = 1 in single crystals and powders
after the two and three pulse sequences (theta(1))(x)-tau(1)-(theta(2)
)(alpha)-tau(2) [-(theta(3))(beta)-tau(3)]. Here alpha and beta the ph
ase-cycling angles, which were incremented properly to select the desi
red coherence transfer pathways. Experiments for double quantum excita
tion and detection were performed on the single crystal and powder sam
ples of NH4ClO4. Because of a fast decay of the signal from the powder
after the two-pulse sequence, we employed the third pulse to produce
an echo related to the double quantum coherence. (C) 1997 Elsevier Sci
ence B.V.