Multiplet patterns due to co-existing intermolecular dipolar and intramolecular scalar couplings in liquid nuclear magnetic resonance

摘要

When both intermolecula dipolar couplins (D couplins)and intramolecular scalar Couplings(J couplings) exist in a highly poarized multiple-spin liquid, some forbidden nuclear magnetic resonance signals originating from intermolecula multipe-quanrum coherences may becom observale. Moreover, their multiplet patterns are quite different from what are observed in a multiple-spin system with J couplings only.In this paper, these forbidden resonance peaks and unique multiplet patterns are sutdied theoretically and experimentally. For comparison and verification,an I2S3+X spin system is chosen as an example to present five types of signal patterns from the interactions of D and J couplins with either selective or non-selective radio-frequency pulse sequences for double-quantum coherences.The multiplet pattern rules for a more general IpSq+Xk(p1q1k=1,2,3,...)spin system are derived as well. It is demonstrated tha some unusual multiplet amplitude patterns such as(1:0:-1) may "magnify" J splittings, allowing more accurate measurement of J coupling in the case of small J coupling constants and /or inhomogeneous fields.It is shown that the theoretical predictions, computer simulations, and experimental observations are all in agreement with one another very well.