Dipolar-dephasing experiments interaction

DQ coherence between C (,-) and C m and then let the DQ coherence evolve under the influence of the heteronuclear I3C-15N dipole-dipole interaction [181, 182]. The virtue of this design is that it can be easily combined with other resolution enhancement technique such as INADEQUATE [183]. Alternatively, the magnetization of C (,) dephased under the 13C-15N dipolar coupling can be transferred to C (j) for another period of 13C-15N dipolar dephasing [183]. This idea can be combined with the NCOCA experiment so that the superior resolution provided by the C (,-)-N(j+i) correlation could be exploited. The overall efficiency, however, is relatively low due to the use of two polarization-transfer steps, viz. 15N —> 13C and 13C —> 13C [183]. In comparison with the techniques, the advan-... 

To this end, the dipolar dephasing behaviour of a wide range of organic compounds has been established (9-12). Various types of carbons experience a wide range of 13C-1H interactions. Carbons weakly coupled to protons, e.g. quarternary carbons follow a single exponential law given by... 

The view that the Si(OH)2 protons experience the strongest H- H dipolar interactions (and presumably the most extensive hydrogen bonding) is further supported by a Si CP-MAS experiment in which a H dephasing period (2t) is inserted between the initial H tt/2 pulse and the CP contact period (Fig. 27) [60]. Results for an untreated silica gel sample are shown in Fig. 28 for four different CP contact times, each with spectra obtained with H dipolar-dephasing times of 2 p,s and 1 ms (corresponding to two rotor periods). The data for small CP contact periods of 100 xs and even 300 (xs show conclusively that the Si... 

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