Pulse-transient adapted C-symmetry pulse sequences

Compensating Pulse Imperfections in Solid‐State NMR Spectroscopy: A Key to Better Reproducibility and Performance

“…In reality,h owever,t he actual rf field experienced by the nuclear spins inside atuned coil deviates significantly from the intended profile [1,2] as shown in Figure 1B.Besides adelayed build-up and decay of the in-phase rf-field amplitude,a lso out-of-phase contributions are observed at the beginning and end of the pulse, referred to as pulse transients. [1,[3][4][5][6] These imperfections impact the performance of the pulse sequences,e specially if the spin interaction to be exploited in the experiment (e.g.the dipolar interactions) is small compared to potentially competing error terms.T herefore,areduced sensitivity to phase transients is indeed ad esign principle for robust pulse sequences. [6] While phase transients were experimentally minimized on spectrometers with tube amplifiers [7][8][9][10] by tuning and matching the amplifier,m odern NMR spectrometers provide no means to do so,with the exception of varying the cable length and probe tuning.…”

“…[6] While phase transients were experimentally minimized on spectrometers with tube amplifiers [7][8][9][10] by tuning and matching the amplifier,m odern NMR spectrometers provide no means to do so,with the exception of varying the cable length and probe tuning. [5,6] There have been different strategies employed to optimize NMR pulse sequences,e .g.,b yn umerical optimization of the pulse sequence on atarget spin system often in the form of optimum control. [11] Such an optimization can include the basic characteristics of the resonance circuit in the form of the transfer function [12,13] but this time-consuming approach needs to be repeated, ideally,f or each sample and temperature as changing the experimental conditions changes the transfer function.…”

“…[11] Such an optimization can include the basic characteristics of the resonance circuit in the form of the transfer function [12,13] but this time-consuming approach needs to be repeated, ideally,f or each sample and temperature as changing the experimental conditions changes the transfer function. [14,15] A related approach which has specifically been used to suppress effects of phase transients is the experimental optimization of pulse sequence parameters that can partially counteract them [5,16] using ag rid search. [14,15] A related approach which has specifically been used to suppress effects of phase transients is the experimental optimization of pulse sequence parameters that can partially counteract them [5,16] using ag rid search.…”

Broadband RF‐amplitude‐dependent flip angle pulses with linear phase slope

“…Switching of pulse amplitude and phase causes transient effects that result in distortions of the ideal input pulse on the time scale τ ≈2 Q / ω 0 . It can reach several microseconds for exotic low‐ γ nuclei, and compensation is required for cyclic solid‐state NMR sequences and especially for EPR experiments using microwave cavities with a very specific response . For currently typical high‐resolution NMR experiments conducted with Q ⩽1500 and resonance frequencies ω 0 /2 π ≈ 600 MHz, however, switching response times are well below the digitization of RADFA pulse shapes and therefore can be neglected.…”

Trace Determination and Pressure Estimation of Fluorine F2 Caused by Irradiation Damage in Minerals and Synthetic Fluorides

“…T 1 saturation recovery, spin‐echo 22 , CPMG, single‐pulse excitation, and double‐quantum NMR experiments on „Antozonite“ were conducted at a magnetic field of 11.7 T on a Bruker Avance III‐500 spectrometer equipped with a commercial 4 mm MAS probe working at the 1 H frequency of 500.13 MHz. We used a transient‐corrected double‐quantum experiment at a sample spinning frequency of 10 kHz, accumulating 128 transients/FID and the POST C‐element with equal excitation and reconversion times that added up to 1.6 ms. The phase cycles were chosen as to satisfy a normalization approach described elsewhere .…”