H-1 CRAMPS BASED ON TREV

Line-narrowing effects of the 1H TREV-8 pulse sequence applied to solids rotating at the magic angle have been examined. Polycrystalline samples of adipic, malonic, and fumaric acids, adamantane, a barley seed, and a pyridine-saturated coal sample were examined. The TREV-based 1H CRAMPS technique is seen to provide reasonably effective line narrowing for both "soft" solids (adamantane) and rigid solids (carboxylic acids), enabling 1H chemical-shift fine structure to be observed. For adamantane, the 1H linewidth is reduced from about 13 kHz (static) to 40 Hz (CRAMPS) at a 840 Hz MAS rate and a pulse spacing (τ) of 7.8 μs. The line-narrowing efficiency increases for larger τ values, but does not approach the efficiency of BR-24. However, unlike the case for BR-24 or other multiple-pulse line-narrowing sequences based on the formation of solid echoes, the line-narrowing efficiency of TREV-8 is sustained for large offsets; this feature, along with a relatively large bandwidth, may be an important factor when the sequence is implemented in 19F CRAMPS and in solid-sample imaging studies. TREV-CRAMPS may also be useful for samples in which the somewhat inferior line-narrowing behavior may be masked by line-broadening effects not based on homonuclear dipolar interactions. © 1993 by Academic Press, Inc.