Proton resonance frequency

NMR instrumentation consists of three chief components a magnet, a spectrometer console, and a probe. While in the past much solid state NMR research was conducted on home-built equipment, the current trend is toward the acquisition of commercial systems. The magnets used for solid state NMR applications generally are superconducting solenoids with a cylindrical bore of 89-mm diameter. The most common field strengths available, 4.7, 7.0, 9.4, and 11.7 Tesla, correspond to proton resonance frequencies near 200, 300, 400, and 500 MHz, respectively. 

Fig. 1.24 Two examples of frequency-depen-dent relaxation times - 7"i is plotted as a function of the proton resonance frequency V = ou/2 JI, which was obtained from measurements at different magnetic fields strengths. Left polyisoprene (PI) melts and solutions of the same samples at 19wt-% concentration in cyclohexane. Numbers indicate the average molecular weight. The difference between the melt and solution increases towards lower magnetic fields strengths, the frequency dependence is more pronounced for melts.

Experimental NRM. Solid-state 13C NMR spectra were collected on a homebuilt spectrometer which operates at a proton resonance frequency of 127.00 MHz, corresponding to a carbon resonance frequency of 31.94 MHz, and employs a... 

The proton resonance frequency, not the field strength, is usually applied to classify the NMR machines. Thus, the NMR instrument should be at least 300 MHz or stronger (e.g. the field strength must be 70 kG or stronger) to achieve constructive anthocyanin spectra. Optimal spectral resolution depends on several factors, including the quality of the NMR tubes (Table FI. 4.2). 

Figure 7.3.2.1 shows the current experimental arrangement employed in Tubingen for capillary separations. A capillary HPLC pump is placed at a distance of about 2.5m from the 14T (proton resonance frequency, 600 MHz) cryomagnet,... 

The self-diffusion coefficients in supercritical ethylene were measured using the pulsed NMR spectrometer described elsewhere (9,10), automated for the measurement of diffusion coefficients by the Hahn spin echo method (11). The measurements were made at the proton resonance frequency of 60 MHz using a 1 1.2 kG electromagnet. 

Quantum chemical ab initio calculations are in agreement with the solution and solid-state experimental data presented above.173 174 The theoretical proton resonance frequency of an isolated HBC 22 (R = H) disk was calculated to be d = 9.3 ppm. Computation of a trimeric aggregate system also revealed three different high-field H NMR signals for the aromatic core, as experimentally found with solid-state NMR techniques.156 173 174... 

Calculate the magnetic fields that correspond to proton resonance frequencies of 60.00 MHz and 300.00 MHz. 

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