title: Sign-sensitive determination of heteronuclear dipolar coupling to spin-1 by selective decoupling.
abstract: This paper presents a theoretical and experimental study of nuclear magnetic resonance technique for sign-sensitive determination of the dipolar couplings of rare spins-1/2 to spin-1 with a strong quadrupolar interaction. The technique is based on low-power transition-selective single-quantum decoupling of spin-1 in the presence of high-power decoupling of abundant (proton) spins. Single-transition operator formalism is employed to calculate the time evolution of the density matrix in the presence of low-power irradiation of spin-1. Generally, the sign of dipolar coupling is unavailable from intrinsically symmetric shapes of dipolar-coupled spectra. Asymmetric dipolar multiplets, resulted from selective decoupling, reveal both the signs and magnitudes of the heteronuclear dipolar couplings. The approach is used to develop the experimental strategy for sign-sensitive measurements of short- and long-range heteronuclear dipolar couplings in highly ordered anisotropic samples. The technique is demonstrated for (13)C-(2)H and (13)C-(14)N spin pairs and for (13)C-(2)H(2) three-spin system in liquid crystals.
authors.affiliation: Department of Chemistry, Royal Institute of Technology KTH, Teknikringen 36, SE-10044 Stockholm, Sweden.
authors.forename: B B
authors.initials: BB
authors.lastname: Kharkov
authors.forename: V I
authors.initials: VI
authors.lastname: Chizhik
authors.forename: S V
authors.initials: SV
authors.lastname: Dvinskikh