Local-field approximation of homonuclear dipolar interactions in 7Li-NMR: Density-matrix calculations and random-walk simulations tested by echo experiments on borate glasses

Quadrupolar transients, cosine correlation functions, and two-dimensional exchange spectra of non-selectively excited spin-3/2 nuclei: A 7 Li NMR study of the superionic conductor lithium indium phosphate

“…the solid black curve in Fig. 1 of [23]) that due to a mixing of the population states T 10 , T 20 , and T 30 a pedestal emerges in the detection period that reflects dipolar correlations which would hamper the acquisition of the desired S 2,Q signal. However, it was also found that for short evolution times dipolar correlations can be kept small very efficiently [23].…”

“…1 of [23]) that due to a mixing of the population states T 10 , T 20 , and T 30 a pedestal emerges in the detection period that reflects dipolar correlations which would hamper the acquisition of the desired S 2,Q signal. However, it was also found that for short evolution times dipolar correlations can be kept small very efficiently [23]. For the C 2,Q signals that we will derive below the situation is more involved and we will present suitable means that rely on appropriately set flip angles as well as on spectrally resolved evaluations to extract pure sin-sin and cos-cos correlation functions.…”

“…(1), by an additional term, D 10 T  . If we assume, like in [23], that for each frequency ω D also a frequency -ω D exists, i.e., that the dipolar broadening is symmetric about zero mean, the signal of Eq. (8) becomes [46]         , ,, S t t t .…”

“…In general, relatively narrow ---# e-mail: michael.storek@tu-dortmund.de quadrupolar satellite spectra emerge only if the charge distribution near the nuclear site deviates not too strongly from cubic symmetry [13]. Interesting, yet somewhat exceptional cases for which such a situation is encountered have been reported, e.g., from 11 B [14], 23 Na [15], and 27 Al [16] NMR studies. A host of NMR techniques is available that allows one to study dynamical processes over wide intervals of time and temperature.…”

“…The processing of such spectra in general requires that a hyper-complex data set comprising sin-sin and cos-cos signals is available [21]. Although the possibility of recording cos-cos correlation functions using spin-3/2 nuclei was raised long ago [22], this issue is still lacking a dedicated theoretical treatment [23], so that up to now 7 Li cos-cos functions were not explored experimentally. The difficulty encountered in exploiting the cos-cos echo stems from the occurrence of quadrupolar transients.…”