NMR lineshapes

Figure Bl.12.5. Zr static NMR lineshapes from ZrO polymorphs using frequency-stepped spin echoes.

Figure Bl.12.8. MAS NMR lineshapes from the central transition lineshape for non-integer quadnipole lineshapes with various (A = / /+l) - 3/4 ...

A theoretical investigation of the use of NMR lineshape second moments in determining elastomer chain configurations has been undertaken. Monte Carlo chains have been generated by computer using a modified rotational isomeric state (RIS) theory in which parameters have been included which simulate bulk uniaxial deformation. The behavior of the model for a hypothetical poly(methylene) system and for a real poly(p-fluorostyrene) system has been examined. Excluded volume effects are described. Initial experimental approaches are discussed. 

In molecularly rigid systems, the direct (through-space) dipole-dipole interaction between nuclear spins I = fe is normally the dominant source of broadening of the NMR lineshape. For a pair of similar nuclear spins i and j in a magnetic field Hq the dipolar splitting in their spectrum is given by... 

Fig. 2 Mechanically oriented bilayer samples as a membrane model for ssNMR. (a) Illustration of the hydrated lipid bilayers with MAPs embedded, the glass supports, and the insulating wrapping, (b) A real sample consists of 15 stacked glass slides, (c) Schematic solid-state 19F-NMR lineshapes from an oriented CF3-labelled peptide (red), and the corresponding powder lineshape from a non-oriented sample (grey), (d) Illustration of typical orientational defects in real samples - the sources of powder contribution in the spectra...

T. The 170 NMR signals that are due to acid sites in supercages and sodalite cages can be resolved in the two-dimensional plot, and their MAS NMR lineshapes for fitting are obtained by extracting two slices at the corresponding chemical shifts of the proton NMR dimension. 

Fig. 6. NMR lineshape for glow discharge deposited a-Si H film grown at 25°C. The top curve is the experimental data and the middle and bottom curves are the deconvolution of the data into broad and narrow components (Reprinted with permission from Reimer et al., 1981a, Pergamon Press, pic).

In a very broad line, then, the size of the spin echo is proportional to the number of nuclear moments near go. If we change Hq, we change h by the same amount and thus sample nuclear moments at a different local field. By measuring the size of the spin echo as a function of Hq, we obtain the NMR lineshape, i.e., in this case, the distribution of the local field among the nuclear spins in the sample. 

Figure 5. Pt NMR lineshapes for six untreated samples. Reproduced with permission from Ref. 1. Copyright 1982, The American Physical Society.

NMR lineshape analysis, 39 376-378 Butyronitrile, hydrogenation over Raney-type nickel catalysts, 36 370... 

Fig. 13. Representative H NMR lineshapes and lineshape changes as a function of pressure in gel states of d62-DPPC at (a) 7°C, (b) 34°C, (c) 41 °C, and (d) 75°C. Pressure conditions are noted for each spectrum.

The ethylene bromonium and 1-bromoethyl cations and their neutral and anionic counterparts have been the subject of a tandem mass spectrometric study of dissociation and gas-phase redox reactions. IR and Raman studies of the bioactive bromonium cation (19), as its hydrogensulfate salt, agree with the results of an X-ray structure determination, and theoretical calculations are also in agreement, except for the details of the NO2 groups. The azaallenium ion (22) is an intermediate in the photolysis of (20) (21) and (22) could both be seen. Flash photolysis of (23) leads to (24), (25), and (26), all of which could be trapped by nucleophiles (27) was not an intermediate. NMR lineshape analysis of the spectmm of (28) leads to reaction rate constants of formation for both the intimate ion pair (29) and the solvent-separated ion pair (30). ... 

Fig. 2. Experimental NMR lineshapes for the two N-methyl signals in 3-Dimethylamino-7-methyl-l,2,4-benzotriazine. We are grateful to C.J.L. Lock and T. Fauconnier for a gift of...

Fig. 3. Simulation of the lineshape of the aldehyde proton in furfural in the intermediate exchange region, and its constituents (lower lines). The lineshape consists of two components, each normal NMR lineshapes but distorted in position, phase, intensity by the dynamics.

The quantities U Ix)j and UFx)j in (13) are projections of the eigenvector j along lx- From the above equations, we can interpret these as follows. The term UFx)j is the amount that the transition j received from the total X magnetization, created from the equilibrium state, and (U Ix)j is how much that transition contributes to the observed signal. These two terms may not be equal, as we see in exchanging systems. This general approach forms the basis of the description of dynamic NMR lineshapes. 

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