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. 2022 May 10;122(10):9943–10018. doi: 10.1021/acs.chemrev.1c00918

Figure 7.

Figure 7

Sensitivity gains by detecting on 1H with respect to heteronuclei (X being 15N or 13C). Virtual RF irradiation schemes for measuring 2D 1H–X correlations with (a) heteronuclei detection and (b) proton detection. Excitation pulses are depicted as black rectangles; indirect chemical shift encoding is performed during the t1 evolution time, and transfer sequences are shown as orange blocks. (c) Sensitivity gain factors ξ are calculated with eq 12 with linewidths (W) measured on a fully protonated microcrystalline GB1 sample: WH = 220, 156, 120, 102, 95 Hz (at 40, 60, 80, 100, 111 kHz MAS, respectively), WC = 105 Hz, and WN = 55 Hz. Both WC and WN are supposed to be constant over the 20–111 kHz MAS frequency range.