Dipolar couplings splittings

The proton NMR signal observed for spin-spin dipolar coupling splits into two components for any anisotropic distribution of that dipolar interaction. In the fast motion limit the splitting is given by ... 

The basic RFDR element consists of two 7i-pulses each centered in the middle of each rotor period in two consecutive rotor periods leading to a cyclic rf field. In the toggling frame of ideal (i.e., infinitely strong) 7i-pulses, the Hamiltonian of the chemical shift terms and the homonuclear dipolar coupling interaction is split up into three commuting parts ... 

Orienting systems of quasi-ternary mixtures composed of cetylpyridinium chloride/hexa-nol/NaCl [26] and cetylpyridinium bromide/hexanol/NaBr [27] have been reported to form lamellar liquid crystalline phases that allow a large temperature range over which dipolar couplings can be measured. The optimum condition for protein alignment consists of a 1 1.33 (w/w) ratio of cetylpyridinium bromide/hexanol. The residual 2H quad-rupolar splitting of the HOD resonance increases from 5 Hz to 20 Hz as the concentration of the mixture is varied from 30 to 65 mg/mL. These quasi-ternary mixtures are positively charged. 

Fig. 35. Part of the spectrum recorded at 3.0 T from TA (shown in Fig. 33b) demonstrating the line splitting caused by dipolar coupling. Triplet structure of Cr3 is resolved, Tau/TMA lead to 4 signal components. The frequency difference between the two Ct2 signals centred at 3.95 ppm is smaller compared to 1.5 T, but these signals are of higher amplitude than in Cr3.

Dipolar coupling (vectorial coupling) only occurs between spatially close nuclei and acts through space. Generally, however, signal splitting does not occur in solution because... 

The conformations of flexible chain molecules incorporated in a nematic environment are investigated. Proton-proton and carbon-carbon dipolar coupling constant measurements are attempted for 1,2-dimethoxyethane and 1,2-diphenoxyethane, in addition to 2H NMR observations of quadrupolar splittings. These conformation-dependent properties are analyzed according to the RIS scheme. Studies are further extended to a mixture of 1,2-diphenoxyethane with a nematic liquid crystal, 4,4 -azoxyanisole. 

By measuring zero-field splitting (zfs) from electron-electron dipolar coupling in triplet radical pairs and proton hyperfine splitting (hfs), Segmuller developed a detailed picture of the motions of these radicals. The sequence of... 

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