High-resolution NMR in inhomogeneous magnetic fields
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Dipolar-coupled spectra of mols. dissolved in liq. cryst. solvents were analyzed by applying pattern recognition procedures to 2-dimensional z-filtered correlation spectra (z-COSY). Transitions that share common common energy levels can be recognized as su ...
New NMR techniques are described for transferring transverse magnetization between scalar-coupled nuclei in the rotating frame. The methods involve simultaneous spin-locking of two selected spins A and X, using cosinusoidal modulation of the radio frequenc ...
A novel spin-echo expt. is proposed that uses semiselective Gaussian pulse cascades for refocusing in systems with homonuclear couplings. The expt. allows one to obtain evdience of differential T2 effects due to cross-correlation of proton chem. shift anis ...
Chirp pulses were used to excite transverse magnetization over bandwidths that are .apprx.50 times wider than the amplitude of the RF field. Exptl. profiles are shown of the amplitudes and phases as a function of offset. The efficiency of refocusing by chi ...
Procedures are described for automated anal. of two-dimensional NMR spectra correlating the chem. shifts of carbon-13 with the shifts of neighbor protons that are directly attached to the carbon-13 nuclei and with remote protons that have scalar couplings ...
In order to sep. overlapping diagonal multiplets in two- or three-dimensional NMR spectra, new sequences using selective pulses are described which allow one to "inject" magnetization at the beginning of the evolution period by transfer from a selected cou ...
In high-resoln. NMR, a network of scalar-coupled spins can be broken down into fragments which encode information about the chem. shifts and couplings that are relevant to a cross-peak multiplet in a two-dimensional correlation ("COSY") expt. Novel selec ...
Computer-supported anal. of two-dimensional correlation spectra encounters a no. of obstacles which are due, in the simplest case, to insufficient digital resoln., and, in more severe cases, to fundamental ambiguities in multiplet patterns. Various strateg ...
An anal. was made of the effects of nonexponential transverse relaxation during the free precession periods of 2-dimensional NMR expts. The presence of cross-correlation between various interactions that cause relaxation, such as chem. shift anisotropy and ...
Cross-correlation between proton chem. shift anisotropy and proton-proton dipolar interactions is shown to be an important relaxation mechanism. Cross-correlation leads to a partial conversion of Zeeman order into longitudinal two-spin order. The build-up ...
