Broadening of resonance lines

It is important to note that the alignment induced by most orienting systems is due to the existence of very weak interactions between the macromolecule and the media itself. Because of the weak character of these interactions, the rotational tumbling of the molecule is not impaired or restricted, and therefore there is no additional broadening of resonance lines due to relaxation phenomena [37]. 

At same time the low-temperature broadening of resonance line at T < 15 K is reproduced completely in powder case. For single crystal this broadening was related to the short-range magnetic order when temperature is approached to Neel point. 

It is found that chemical shifts are very small, and in order to observe such effects one must study the material under suitable conditions. In solids, where intermole-cular motion is highly restricted, internuclear interactions cause such a great broadening of resonance lines that chemical shift differences are masked (as we discuss in detail in Chapters 2 and 7). In liquids, on the other hand, rapid molecular tumbling causes these interactions to average to zero, and sharp lines are observed. Thus, in the early days of NMR studies, there came to be a distinction... 

The slow rotational diffusion of the particles leads to a certain broadening of resonance lines and side bands (Fig. 10), finally resulting in a total loss of the MAS effect when the correlation time r reaches the same order of magnitude as the reciprocal spinning velocity 1/cUr (Fig. 10, bottom). The sideband integrals follow a pattern which is predicted by the method of Herzfeld and Berger." ... 

The temperature dependences of the linewidths for both lines are presented on Fig. 7.7. The considerable broadening of resonance lines with the lowering of temperature below 100 K is observed. 

The importance of Doppler broadening of resonance lines in the calculation of resonance neutron absorption was first pointed out by J. A. Wheeler. 

Lopez del Amo et al. have shown that high magnetic fields allow to overcome the broadening of resonance lines often experienced at liquid nitrogen temperatures. For a fibril sample of the Alzheimer s disease p-amyloid peptide, the authors found similar line widths at low temperature and at room temperature. The presented results are shown to open new perspectives for structural investigations in the solid-state. ... 

In poly(A/l-Np(x)) (see Scheme 2) with varying 1-Np contents, a marked broadening of resonance lines occurs at a 1-Np content between 28 and 41... 

VIII. Study of the Broadening Effect of Resonance Lines. 203... 

Ben-Reuven A. Resonance broadening of spectral lines. Phys. Rev. A4, 2115-20 (1971). 

Recent research has largely focused on spin-wave excitations in perfect nanostructures [151-156]. In addition, real-structure effects have been considered [5, 153], In macroscopic systems, the superposition of individual lines leads to a line broadening due to real-structure inhomogenities and field gradients. In nanostructures, the superposition of resonance lines is a... 

The above-mentioned transitions are accompanied by only slight modifications of the coupling constant however, drastic changes occur above the transition temperature when strong molecular motions take place with nearly complete reorientation of the molecules the quadrupole resonance is no longer observable, while a rapid change in the resonance frequency and a broadening of the line are seen just before the transition. 

Maddock AG (1985) Mossbaner spectroscopy in mineral chemistry. In FJ Berry, DJ Vaughan (eds) Chemical Bonding and Spectroscopy in Mineral Chemistry. Chapman and Hall, London, p 141-208 Margnlies S, Ehrman JR (1961) Transmission and line broadening of resonance radiation incident on a resonance absorber. Nncl Instr Meth 12 131-137... 

Obviously, the magic angle spinning techniques described briefly above rely on coherent averaging out of resonance line-broadening interactions. An alternative approach is to cause solids to assume the incoherent motion of molecules in the liquid phase. Essentially, two such methods exist. The first is the so-called ultra-fine particle NMR (UFPNMR) method which was proposed originally by Yesinowski [21 ] and developed further by Kimura [22,23]. The second is the sonically induced narrowing of the NMR spectra of solids (SINNMR) that was demonstrated recently by Homer et al. [24,25]. 

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