Resonant slice

Figure 7.10 Single spin detection by MRFM. The result is from Rugar et al. (2004). The two plots correspond to different values of the external field. Changing the external field modifies the resonant slice, which in turn causes a shift in the peak. The average distance between spins in the sample is 300 A. Adapted with permission from [19].

The best position in the stray field is actually not where the gradient is maximum, because at this position the resonant slice is not planar since the magnetic field off-axis is not uniform. The optimum position is where the slice is planar. This occurs where the lines of equipotential lines are orthogonal to the Z axis. Nearer the centre of the magnet the equipotential lines are curved one way, but further from the centre they curve another way. Exactly at the optimum position a flat disc extends someway off-axis, typically about 1cm for superconducting magnets with bores of 8.9 cm. 

Resonant slice moves with central field... 

As before, we note that the resonance frequency of a nucleus at position r is directly proportional to the combined applied static and gradient fields at that location. In a gradient G=G u, orthogonal to the slice selection gradient, the nuclei precess (in the usual frame rotating at coq) at a frequency ciD=y The observed signal therefore contains a component at this frequency witli an amplitude proportional to the local spin density. The total signal is of the fomi... 

The darkest regions in the slices indicate the greatest electron density. The meta form of nitrated chlorobenzene and the para form of nitrated nitrobenzene retain the resonance structure to a much greater degree throughout the extent of the electron density. In contrast, the density in the less-favored conformations becomes more localized on the substituent as one moves outward from the plane of the carbon atoms. 

Fig. 7. The probability density of the reactive resonance at Ec = 0.52 kcal/mol. In (a) the F-H-D collinear subspace is shown using the Jacobi coordinates (R,r). In (b), the probability density is sliced r = 2 Bohr and is shown in the (R, 7) coordinates. The plot clearly shows a state with 3 nodes along the asymmetric stretch and 0 nodes in the...

The SQ method extracts resonance states for the J = 25 dynamics by using the centrifugally-shifted Hamiltonian. In Fig. 20, the SQ wavefunc-tion for a trapped state at Ec = 1.2 eV is shown. The wavefunction has been sliced perpendicular to the minimum energy path and is plotted in the symmetric stretch and bend normal mode coordinates. As anticipated, the wavefunction shows a combination of one quanta of symmetric stretch excitation and two quanta of bend excitation. The extracted state is barrier state (or quantum bottleneck state) and not a Feshbach resonance. 

Figure 8 F2 Slices through a series of 1,1-ADEQUATE spectra of retrorsine (2) at the F2 shift of the H17 resonance.51 The optimization is shown above the individual spectral segments. The correlation shown in the individual traces is that from the 07 sp2 resonance to the 05 sp2 resonance. The absence of this response in the 60 Hz optimized spectrum (see Figure 7) prompted the acquisition of the series of spectra shown.

The 5 Hz optimized l,n-ADEQUATE spectrum of strychnine (1) is shown in Figure 9.70 The high resolution 600 MHz proton spectrum is shown in Figure 10A and compared to slices extracted at the Fi frequency of the C15 methylene resonance in the 5 Hz optimized l,n-ADEQUATE spectrum (B) and the 60 Hz optimized 1,1-ADEQUATE spectrum (C). The adjacent carbons (via Vcc) show correlations in the 5 Hz optimized INADEQUATE spectrum that are unsuppressed but all possible three-bond... 

B) Slice taken through the 5 Hz optimized INADEQUATE spectrum of 1 at the F1 shift of the C15 methylene resonance. (C) Comparison slice taken through the 60 Hz optimized 1,1-ADEQUATE spectrum of 1 at the Fn shift of the C15 methylene resonance. 

Figure 3 2D 27Al-29Si RAPT-CP-CPMG HETCOR data for zeolite ZSM-4 recorded at 14.1 T with 10 kHz MAS. The 2D spectrum was acquired in 30 rows of hypercomplex data, with 64K scans per row, h increments of 100 ps, and acquisition time of 38 hours. In the right, ID slices taken through the centers of Ah and Al2 resonances are compared with ID 29Si MAS spectrum.

Evans, S.D., Brambilla, A., Lane, D.M., Torreggiani, D., and Hall, L.D. 2002. Magnetic resonance imaging of strawberry (Fragaria vesca) slices during osmotic dehydration and air drying. Lebensmittel-Wissenschaft Technol. 35, 177-184. 

Magnetic Resonance Imaging on whole body units provides visualization of tissue inside slices with a thickness of several millimetres. The spatial resolution in the plain is often better than one millimetre so that even relatively small structures can be well depicted. However, the spatial resolution is not sufficient to resolve the microscopic structures mentioned in Section 2. Only the cross-sections of single muscles and septa from fatty tissue or cormective tissue can be visualized in MR images recorded from humans in vivo. 

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