RFDR experiment

The RFDR experiment (Fig. 2b), here serving to illustrate the incorporation of finite rf pulse effects into the design or refinement process, was first introduced by Griffin,... 

We note that DRAMA has also formed the basis for refined variants such as the chemical-shift-compensated MELODRAMA [85], windowless DRAWS [29], and the DRAMA-XY4 [86] experiments, finding important applications for example for measurement of 13C-13C distances involving carbonyl spins. We should also note the existence of many other important pulsed homonuclear recoupling experiments such as the widely used Radio Frequency Driven Dipolar Recoupling (RFDR) [24] and Back-to-Back (BaBa) [87] experiments. 

Fig. 2 (a) DRAMA pulse sequence (using % = t/2 = rr/4 in the text) and a representative calculated dipolar recoupled frequency domain spectrum (reproduced from [23] with permission), (b) RFDR pulse sequence inserted as mixing block in a 2D 13C-13C chemical shift correlation experiment, along with an experimental spectrum of 13C-labeled alanine (reproduced from [24] with permission), (c) Rotational resonance inversion sequence along with an n = 3 rotational resonance differential dephasing curve for 13C-labeled alanine (reproduced from [21] with permission), (d) Double-quantum HORROR experiment along with a 2D HORROR nutation spectrum of 13C2-2,3-L-alanine (reproduced from [26] with permission)... 

Fig. 11.6 Pulse sequence for two-dimensional homonuclear chemical-shift correlation experiments. The gray box indicates the mixing sequence, with some examples shown in more detail a RFDR, b RIL, c C7, d DRAWS, e DREAM.

One-dimensional - P NMR is only able to probe the the local structure of phosphate glasses. To gain information about the manner in which the different Q" units or domains in phosphate glasses are connected, two-dimensional MAS exchange experiments have been used in which radio-frequency dipolar recoupling (RFDR) techniques allow the reintroduction of the through-space dipolar-dipolar interaction even... 

NMR exchange experiments for the study of surface dissolution species in solution-aged metaphosphate glass has been reported. It has been demonstrated that use of CP allows the resonances of phosphate tetrahedral species within the hydrated dissolution surface to be selectively and cleanly edited from the bulk unaged phosphate species. Incorporating the CP-editing into a 2D RFDR exchange experiment also has allowed the local spatial connectivity between these surface dissolution phosphate species to be directly addressed. 

Bennett et al. have given a thorough discussion of SEDRA/RFDR-type experiments in ref. 104, where they covered influences from finite pulses, insufficient proton decoupling, and multi-spin interactions, and introduced a modified version of the basic RFDR sequence with delays of duration kr incorporated between sets of four tt pulses (see Fig. 2Id). This modification recouples weak dipolar coupling interactions only at the conditions n/kyjJt, which avoids the conditions (o A =znu>r) if n/k is not an... 

Meth. DR LA LM MB MW RA method of measurement applied to obtain the reported value double resonance experiments (microwave-optical double resonance MODR or radiofrequency-optical double resonance RFDR) Doppler free laser spectrosefipy laser magnetic resonance molecular beam electric resonance or molecular beam resonance with laser detection method microwave spectroscopy radio astronomy... 

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