NMR probe heads

Busse-Grawitz, M. E., Roeck, W., NMR Probe Head With Cryogenically Cooled Preamplifiers, in United States Patent 5,814,992. 

The exact course of the reaction of lg with 12 (Eq. 21) was studied by monitoring the NMR spectra (1H, 13C, and 29Si) of the reaction mixture at low temperatures.41 The reagents (lg and 12) were dissolved at liquid nitrogen temperature in CD2C12 and the solution was placed in a pre-cooled (200 K) NMR probe-head. The various NMR spectra were then measured at various temperatures. Equation (22) outlines the resulting reaction sequence. 

Hardware requirements are slightly different from those for traditional NMR measurements NMR probe heads must be absolutely free from fluorine, but such probes are now commercially available. It is usually necessary to have two high-frequency channels on the NMR spectrometer to allow fluorine measurements with proton decoupling, and good RF-filters must be used to separate the 19F and ll channels. 

H. J. Schneider and P. Dullenkopf, "Slotted tube resonator A new NMR probe head at high observing frequencies," Rev. Sci. Instrum. 48, 68-73 (1977). 

A most straightforward way of applying NMR to study molecular distributions during dynamic processes such as adsorption, counterdiffusion, or chemical reaction is based simply on the NMR signal intensity being directly proportional to the number of resonating nuclei within the sample coil of the NMR probe head. 

Figure 4-4 Hardware set up for NMR-controlled titrations NMR spectrometer, 2 PC, 3 burette, 4 glass electrode and potentiometer, 5 thermostat, 6 thermostated titration vessel, 7 stirrer, 8 pump, 9 NMR probe head.

Figure 3.51. Tuning and matching a NMR probe head. The dark Une represents the probe response seen for (a) a mis-tuned and (b) a correctly tuned probe head.

If continuous electrode potential control during acquisition of the NMR spectrum is desired, particular attentimi has to be paid to proper shielding and decoupling of the electrical wiring between potentiostat and NMR probe head. Results reported so far pertain in particular to C-NMR spectroscopy of adsorbed CO- and CN ions (Ml platinum [21, 23, 24]. Besides, information about surface diffusion and electronic adsorbate-surface interaction data on the effect of the strong electric field at the electrochemical interface (typically 10 V cm ) have... 

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