Robust and efficient spin-locked symmetry-based double-quantum homonuclear dipolar recoupling for probing 1H–1H proximity in the solid-state

Double-quantum NMR spectroscopy of 31P species submitted to very large CSAs

“…4 in Ref. [39]). However, we have verified with the 'C and R symmetries' Mathematica package that the first-and second-order AHT scaling factors of ðR2 1 2 Þ p ðR2 À1 2 Þ p and ðR2 1 2 R2 À1 2 Þ p sequences are identical up to p = 4.…”

“…2, 5 and 7 in Ref. [39]). Furthermore, it is confirmed in the case of 31 P nuclei experiencing large CSA by the comparison of Fig.…”

“…1c, was recently introduced in order to recouple the 1 H-1 H dipolar couplings at high MAS frequency [39]. It is constructed from the R2 1 2 symmetry-based sequence employing a composite p pulse R ¼ h 0 p 0 h 180 as basic element.…”

“…The rf irradiation was applied in the middle of these two resonances, which are separated by a small difference in isotropic chemical shifts of Dd iso = 2 ppm. [39]. If the BABA sequence benefits from the shorter recoupling time, it is not able to manipulate efficiently spin species submitted to not negligible CSAs (Fig.…”

“…The symmetry-based sequences with lower rf field requirements are more promising for fast MAS solid-state NMR. Recently, we demonstrated that a sequence derived from the R2 1 2 symmetry achieved an efficient 1 H-1 H 2Q dipolar recoupling at high spinning speeds [39]. This sequence denoted SPIP (Sandwiched PI Pulse) was also shown to be robust to offset for 1 H spectra.…”