Rq. Fu et al., NMR OF RESIDUAL PROTONS IN PARTLY DEUTERATED ANISOTROPIC MATERIALS WITH PHASE-ALTERNATED DECOUPLING OF DEUTERIUM SPINS, Solid state nuclear magnetic resonance, 5(4), 1996, pp. 273-291
A new method is presented for decoupling spins with S = 1 like deuteri
um in anisotropic media while observing other spins such as residual p
rotons in partly deuterated samples. The carrier frequency of a weak r
adiofrequency (RF) field is applied near the center of the doublet ari
sing from the quadrupolar interaction of the S = 1 spins. The phase of
the RF field is periodically reversed with intervals matching the rec
iprocal of the magnitude of the quadrupolar splitting. It is shown by
theory and experiment that, even when the irradiating field is quite w
eak, the efficiency of this phase-alternated decoupling scheme is much
better than for simple continuous-wave irradiation at the center of t
he doublet, an established technique which is usually referred to as d
ouble quantum decoupling. The phase-alternated experiment makes it pos
sible to decouple large quadrupolar interactions with a weak RF field.
A theoretical analysis and numerical simulations are presented to dem
onstrate the decoupling performance. Proton spectra of partly deuterat
ed dibromobutane in a liquid crystalline solvent have been recorded to
illustrate the efficiency of phase-alternated deuterium decoupling.