Simulation studies of instrumental artifacts on spin I=1 double quantum filtered NMR spectroscopy

Abstract

We report on the results of a simulation based study of the effect of various experimental artifacts for spin I=1 double quantum filtered NMR. The simulation captures the effects of static field inhomogeneity, finite pulse widths, phase errors, transients and radio frequency inhomogeneity. We simulated the spectral distortions introduced under these errors for four, eight and sixteen step phase cycles that are well known in the NMR community. The dominating pulse errors are radio frequency field inhomogeneity and antisymmetric pulse transients. These errors result in the reduction of signal intensity as well as an introduction of distortions in the detected double quantum filtered spectrum. Using the simulation tool we studied the improvement one obtains when implementing a sixteen step phase cycle over a four step phase cycle. The results indicate that implementing a sixteen step phase cycle over an eight or four step phase cycle does not result in a significant reduction in the DQF intensity loss, or reduction in spectral distortions for antisymmetric transients.

Effects of Instrumental Artifacts on Double-Quantum-Filtered NMR Buildup Curves for Spin $$I=1$$ I = 1

“…5 that as the ratio of S 450 /S 90 decreases, the overall amplitude of the buildup curve decreases. This is consistent with our previous finding that the signal intensity drops with increasing the degree of the RF pulse inhomogeneity [16]. Regarding Table 3, the best-fitting parameters for T a and T b are both found to be almost independent of the ratio of S 450 /S 90 , since the variation in T a is only about 1 % and the difference in T b is less than 3 %.…”

“…[15], the signal loss due to static field inhomogeneity is also well known to the community and implementing a p pulse in the conventional DQF pulse sequence is commonly used [10], the effects of RF artifacts on spin I ¼ 1 were examined theoretically and experimentally [16,17], and more recently various phase cycling schemes were also applied to counter the static field inhomogeneity in multiple-quantum-filtered NMR [18,19]. We have previously simulated the DQF spectra under various artifacts and have found that the most significant artifacts were finite pulse widths, RF inhomogeneity and pulse transients [16]. In this paper, these artifacts are further studied to probe their effects on the whole DQF buildup curves, which is a more practical aspect of deuterium DQF experiments for the determination of the anisotropic motions of water in biological tissues.…”

“…Note also that the total pulse length of the transients and the mean pulse remained the same (i.e., s p ), which is slightly different from the model used in our previous work [16] wherein the length of the mean pulse were fixed. In this work we simulated both symmetric and antisymmetric transients with e ¼ 0, 0.1 and 0.2.…”

Investigation of the effect of a variety of pulse errors on spin I=1 quadrupolar alignment echo spectroscopy

“…In a previous work [13], we adopted a model after A. J. Vega [14], where any RF pulse of our pulse sequence includes a transient effect. The model consists of an orthogonal RF field that is applied to the spin system before and after the main pulse.…”

“…where τ c is cycle time of the multiple pulse sequence and the modulation induced by the RF transient in a stroboscopic measurement is given by [13]…”