Variable angle spinning

It has also been shown that the technique referred to as multiple-quantum variable angle spinning (MQVAS) can be used for the purpose of separating the CSA and quadrupolar lineshapes [155]. In this experiment, a judicious choice of the rotor orientation is fjRL = 70.12°, which leads to cancelation of the fourth-rank term of the second-order interaction (Fig. 2). Thus, the refocusing ratio k for the quadrupolar interaction depends on the ratio of the second-rank terms... 

Among spatial reorientation techniques, one can find MAS, OMAS, variable angle spinning (VAS) and switched angle spinning (SAS) techniques. Mechanical spinning of LC materials, which has dated back to the early seventies,63,64 can control the averaging of anisotropic spin interactions... 

Figure 2.18. Variable angle spinning spectra for different angles as a function of different ti, from Ganapathy, Schramm and Oldfield (1982) with permission of the copyright owner.

Figure 18 O static, MAS, variable-angle spinning (at 79.19°), and one-dimensional...

As already mentioned, the most common technique for recovering anisotropic CS information is to spin the sample at rates much less than the span (in frequency units) " however, when one has multiple sites, spectral overlap may be unavoidable. Another technique that has been used to address this problem is variable-angle spinning (VAS). ... 

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