Pulse-transient adapted C-symmetry pulse sequences
- 作者：Johannes Weber ; Marten Seemann ; Jö ; rn Schmedt auf der Gü ; nne ; gunnej@cup.uni-muenchen.de
- 关键词：NMR ; Solid-state ; Pulse transients ; C-sequences
- 刊名：Solid State Nuclear Magnetic Resonance
- 出版年：2012
- 期刊代码：83_09262040
- 类别：ce
- 出版时间：May-June, 2012
- 卷：43-44
- 期：Complete
- 页码：42-50
- 文件大小：1238 K
摘要
In solid-state NMR, pulse sequences make often use of pulses which are short compared to the recovery time of the probe head. Especially, rotorsynchronized dipolar recoupling experiments under magic-angle-spinning conditions can profit from the use of very high pulse amplitudes which in turn will reduce the length of the individual pulses. In this contribution we show that C-symmetry based pulse sequences used for double-quantum filtering experiments can strongly be influenced by pulse transients. We analyze the origin of pulse transients and show that the quadrature component can be minimized by cable-length variation which causes a mutual cancellation of probe-external and internal contributions. We implement and test a model to investigate the influence of pulse-transients by numerically exact calculations of the spin-density matrix allowing for composite pulses consisting of slices which are short compared to the circuit recovery time-constant. Moreover we introduce a phase-tuned C-element, which can be applied to experiments from the C-symmetry class, to reconstitute an almost ideal performance of the sequence. We have validated the modified transient-adapted pulse sequences theoretically on the basis of numerically exact calculations of the spin-dynamics. While comparably easy to apply the scheme proved also robust in practical application to 15N, 13C and 31P double-quantum filtered experiments and leads to a significantly increased conversion efficiency.