Nuclear magnetic resonance transient measurement

There are macroscopic (uptake measurements, liquid chromatography, isotopic-transient experiments, and frequency response techniques), and microscopic techniques (nuclear magnetic resonance, NMR and quasielastic neutron spectrometry, QENS) to measure the gas diffusivities through zeolites. The macroscopic methods are characterized by the fact that diffusion occurs as the result of an applied concentration gradient on the other hand, the microscopic methods render self-diffusion of gases in the absence of a concentration gradient [67]. 

Since the first TR EPR experiment in 1968 by Atkins et al3 and Smaller et this experimental technique has developed into a powerful tool for studying transient paramagnetic species in the nanosecond and microsecond time range. Modern pulsed EPR instrumentations " has resulted in improved sensitivity and time resolution, and measurements similar to pulsed nuclear magnetic resonance can be performed. 

Early on in the development of new organometallic (catalytic) reactions, the isolation and characterization of metal complexes participating in the reaction is often key, as screening and optimization implicitly rely on structure-property relationships. While catalyst precursors are by necessity stable and thus relatively easy to characterize with a variety of spectroscopic (most commonly perhaps infrared (IR), nuclear magnetic resonance (NMR), and ultraviolet/visible (UV-Vis)) and (X-ray) diffraction techniques, the catalytically active/relevant intermediates may only be transient. Nevertheless, careful kinetic measurements to determine the relationships between the concentrations of individual reagents... 

In this section we have described in considerable detail just one aspect of the spectroscopy of OH, namely, the measurement of zl-doubling frequencies and their nuclear hyperfine structure. This has led us to develop the theory of the fine and hyperfine levels in zero field as well as a brief discussion of the Stark effect. We should note at this point, however, that OH was the first transient gas phase free radical to be studied by pure microwave spectroscopy [121], We will describe these experiments in chapter 10. We note also that magnetic resonance investigations using microwave or far-infrared laser frequencies have also provided much of the most important and accurate information these studies are described in chapter 9, where we are also able to compare OH with the equally important radical, CH, a species which, until very recently, had not been detected and studied by either electric resonance techniques or pure microwave spectroscopy. 

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