A study of the molecular motion in glucose/water mixtures using deuterium nuclear magnetic resonance Different "average" nuclear magnetic resonance relaxation times for correlation with fluid-flow permeability and irreducible water saturation in water-saturated sandstones

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In ultralow magnetic fields, liquid state nuclear magnetic resonance (NMR) spectra of homonuclear spin systems exhibit line widths dominated by their natural lifetime. Chemical shifts become negligible, and heteronuclear NMR spectra show predominantly the electron-mediated field-independent J-coupling. However, weak polarization and Larmor frequencies down to a few hertz require special detectors, such as Superconducting Quantum Interference Devices (SQUID), that also enable the simultaneous detection of broad band spectra of heteronuclear spin systems. We acquired spectra of 2,2,2-trifluoroethanol and trimethyl phosphate at detection fields varying from 444 nT to 3.34 muT after prepolarizing the sample in a field of 250 muT. Down to a 1H Larmor frequency of 40 Hz, the spectra of trifluoroethanol exhibited four clearly resolvable peaks. The numerical simulation agreed well with the measured spectra. Trimethyl phosphate exhibited two major groups of nonresolved proton lines. At 1H Larmor frequencies below 150 Hz, the separation of the two groups decreased, reflecting the transition from weakly to strongly coupled spin systems. Direct determination of 3J(H,P) from the peak separation is possible only at Larmor frequencies above 150 Hz. The experimental setup allowed an easy adjustment of the detection field over several octaves. This enabled us to adapt the detection field to the best-suited measurement window providing the maximum spectral information. Low-field NMR may open new applications, such as monitoring heteronuclear reactions, low-field imaging, simultaneous NMR/magnetoencephalography measurements, or quantum computing.

A system of magnetic nanoparticles (MNPs) and modified latex spheres was used serving as a model for studying binding reactions. The binding of MNPs on latex is estimated by the change of the magnetic relaxation properties of the MNP measured by a SQUID-based magnetorelaxometry measurement system. By fitting of subsequently recorded relaxation curves, the kinetics of the binding reactions, i.e. the evolution of the fraction of bound MNPs, was extracted. The signal of bound MNPs scales linearly with the concentration of latex beads. For low latex concentrations the kinetics are described by a simple aggregation model, providing information about the density and probability of bindings to the target surface.

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Residual dipolar couplings between quadrupolar nuclei in solid state nuclear magnetic resonance at arbitrary fields Evaluation of radio frequency microcoils as nuclear magnetic resonance detectors in low-homogeneity high-field superconducting magnets Rev.

We modified two SQUID measurement systems, originally developed and optimized for biomagnetic applications, with the aim to employ them for observing the precession of nuclear magnetism in low fields of a microtesla or less. To this end, coil systems for the polarization and for the observation of the nuclear magnetization were added to the set-up. In addition, SQUID readout electronics had to be fast enough to allow for short dead times after switching off the polarizing field. One system was a single channel gradiometer that is routinely used for measuring the relaxing magnetism of magnetic nanoparticles. The second system was a 304 SQUID system that was designed for multichannel vector-magnetocardiography and vector-magneto-encephalography. Both systems had in common that they operated in a magnetically shielded environment provided by multi-layer mu-metal walk-in rooms. With the single channel system we determined the natural proton NMR line width of benzene in the fast motional limit to be (112 3) mHz. The accuracy of this value was improved by excluding experimentally the presence of line broadening by the inhomogeneity of the residual environmental field in the magnetically shielded room. To this end, the transversal relaxation of hyperpolarized 129 Xe gas was measured demonstrating that the spectrometer has a spectral resolution of about 6 mHz for 1 H. By using a 304 SQUID vector magnetometer system the precession of 1 H in multiple distilled water samples was recorded. From the spatially resolved data of the multi-SQUID system, positions and moments of the multiple samples were estimated.

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