Zero-Field Nuclear Magnetic Resonance

Abstract

In polycrystalline samples, NMR "powder spectra" are broad and much structural informa ion is ost as a result of the orientational disorder In th' Lett F n zs er Fourier-transform R m zero magnetic field is described. With no f d d no pre erre irection in space, all direct in ter crystallites contribute equivalently and resolved d 1 1'tt' ve zpo ar sp ettings can be interpreted irect y in terms of internuclear distances. This open th 'bl'-f s e posse ray-o molecular strucure etermination without the need for single crystals or oriented samples

High-Resolution Zero-Field NMR J-Spectroscopy of Aromatic Compounds

“…The basic qualitative structures of these spectra are consistent with previous work, with peaks at nonzero frequency arising due to J-couplings in molecules containing spins with at least two different gyromagnetic ratios. The simplest examples include 13 . We refer to these systems as XA, XA 2 , and XA 3 , respectively, where X is 13 C and A n represents a set of equivalent protons.…”

Scalar operators in solid-state NMR

“…Time-domain zero field NMR and NQR spectroscopy has provided a new method for obtaining high resolution spectra of a. polycrystalline or amorphous sample and therefore allows us to measure the dipolar coupling or quadrupolar coupling constants without the spectral resolution problem [8]- [12]. However, we can observe neither In order to increase the sensitivity of the zero field experiments, a spin-locking technique has been employed [9] for the high field observation.…”

“…Time-domain zero field NMR has proven powerful for obtaining high-resolution spectra of polycrystalline or amorphous samples in solids [8]- [18]. The convenience is obvious in the assignment of the sites, local symmetry, and even the exchange between sites from these spectra.…”

“…This severe sensitivity problem may be overcome by using either SQUID techniques [31,32,33] or bY,the field cycling method proposed by Pound [7], used first in pure NQR spectroscopy. The most recent application of the field cycling technique is in time-domain zero field NMR and NQR spectroscopy [8]- [12]. In this experiment, the solid sample is transferred pneumatically from the high magnetic field One would like to advance time-domain zero field NMR and NQR by finding zero field analogs to multi-pulse and multi-dimensional methods originating from high field NMR[1l]- [18] to simplify the identification of sites, obtain more structural in-2 formation of molecules, study the motions in molecules, and measure exchange rate between orders.…”

Isotropic proton-detected local-field nuclear magnetic resonance in solids

“…Since the anisotropy of the dipolar frequencies in a powdered sample is due to the presence of a large Zeeman field, many methods have been developed which either evolve the system in zero-field 7,8 or make the system appear to have evolved in zero-field through the application of some multiple-pulse sequence [9][10][11][12] . The zero-field dipolar Hamiltonian is given by where A IS 2,m (θ IS , φ IS ) and T IS 2,m are second rank spatial and spin tensors respectively, and (θ IS , φ IS ) are polar angles relating the spin quantization axis to r IS .…”