NMR relaxometry experiments

Field-cycling NMR relaxometry experiments can be favorably supplemented by ordinary high-field relaxation measurements employing the inversion-recovery or saturation-recovery variants. Comparative spin-lattice relaxation experiments in the rotating frame (Tip) are also of interest particularly in the presence of molecular order [22]. A detailed description of the diverse NMR methods referred to can be found in Ref. [2]. 

The conclusion from these findings is that the Rouse model is perfectly corroborated by NMR relaxometry experiments provided that entanglement effects are excluded or not effective on the time/frequency scale of the exper-... 

If possible, white cement binders are preferable for H-NMR relaxometry experiments. They provide a higher sensitivity and more accurate results. NMR on grey binders can still be carried out, however, with the knowledge that results have lower sensitivity and more noise. 

With the different H-NMR experiments described in this chapter, all the water within a cement paste can be identified and quantified. NMR relaxometry experiments at frequencies in the range of 5-20 MHz measure the following ... 

In what follows, we wish to describe the most important technical aspects of FFC NMR relaxometry, including both the required special hardware (magnet, power supply, etc.) and the measurement methodology (data acquisition sequences and, to some extent, the subsequent data evaluation). Naturally, the description is based primarily on our own experience which has not yet been described in detail elsewhere. 

Any NMR field-cycling (FC) relaxometry experiment presumes that the sample is subject to a magnetic field of various intensities for time intervals of varying durations. More specifically, between the various intervals of a relaxation-time measurement, the external magnetic field induction... 

Faster incoherent tunnelling processes can be studied by solid state NMR relaxometry [40, 41]. In these experiments the experimentally determined spin-lattice relaxation rates are converted into incoherent exchange rates. The latter are then evaluated, for example with the Bell tunnelling model described above. 

In many NMR experiments it was noticed that liquids confined in porous materials exhibit properties that are very different from those of the bulk fluid. The so-called longitudinal (Tl) and transverse (72) relaxation time of bulk water, e.g., are on the order of seconds, whereas for water in a porous material these times can be on the order of milliseconds. The measurement of T and 72 in an NMR experiment is often called NMR relaxometry. The transverse relaxation time is more sensitive to loeal magnetie field gradients inside the porous material than the longitudinal relaxation time. This sensitivity can be used to measure the self-diffusion eoeffieient of the liquid. The interpretation of the measured self-diffusion eoeffieient of a eonfined liquid is often called NMR diffiisometry. 

Hitchcock, I., Holt, E.M., Lowe, J.P., and Righy, S.P. 2011. Studies of freezing-melting hysteresis in cryo-porometry scanning loop experiments using NMR diffiisometry and relaxometry. Chem. Eng. Sci. 66 582-592. 

This review presents recent developments in the application of nuclear magnetic resonance (NMR) spectroscopy to study ionic liquids. In addition to routine structural characterization of synthesized ionic liquids, availability of multitude of advanced NMR techniques enables researchers to probe the structure and dynamics of these materials. Also most of the ionic liquids contain a host of NMR-active nuclei that are perfectly suitable for multinuclear NMR experiments. This review focuses on the application of NMR techniques, such as pulsed field gradient, relaxometry, nuclear Overhauser effect, electrophoretic NMR, and other novel experiments designed to investigate pure ionic liquids and the interaction of ionic liquids with various salts and solutes. 

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