WURST sequence

As in HMQC, a delay time A governs both the initial defocusing of the C-bonded H vectors and the final refocusing of these vectors and is, likewise, selected in a compromise manner. Carbon decoupling also can be performed with the GARP or WURST sequences as... 

Wurst http //www.zbh.uni-hamburg.de/wurst Sequence to structure alignment... 

Siegel et al. showed that enhancement of the CT can also be obtained using hyperbolic secant (HS) pulses to invert selectively the STs [74], Unlike the DFS waveform, whose frequency sweep is generated by a constant rf-pulse phase while modulating the amplitude, the HS pulse utilizes both amplitude and phase modulation, yielding an enhancement exceeding that obtained by DFS or RAPT [61, 74, 75]. Most recently, the pulse sequence called wideband uniform-rate smooth truncation (WURST) [76] was introduced to achieve selective adiabatic inversion using a lower power of the rf-field than that required for the HS pulses [77,78]. One of its applications involved more efficient detection of insensitive nuclei, such as 33S [79]. 

Shaped pulses are created from text files that have a line-by-line description of the amplitude and phase of each of the component rectangular pulses. These files are created by software that calculates from a mathematical shape and a frequency shift (to create the phase ramp). There are hundreds of shapes available, with names like Wurst , Sneeze , Iburp , and so on, specialized for all sorts of applications (inversion, excitation, broadband, selective, decoupling, peak suppression, band selective, etc.). The software sets the maximum RF power level of the shape at the top of the curve, so that the area under the curve will correspond to the approximately correct pulse rotation desired (90°, 180°, etc.). When an experiment is started, this list is loaded into the memory of the waveform generator (Varian) or amplitude setting unit (Bruker), and when a shaped pulse is called for in the pulse sequence, the amplitudes and phases are set in real time as the individual rectangular pulses are executed. 

WURST Wideband, uniform rate and smooth truncation (broadband decoupling sequence) 9.2... 

The WURST decoupling sequence was implemented with the Pbox in Varian s VNMR software, using a constant adiabaticity modulated frequency, a 0.92 ms pulsewidth, and a 1.2 adiabaticity frictor (Q). The constant radiofiequency level yBaCrms) was 4.3 kHz. In order to compensate for residual imperfections in spin inversion, the five-step phase cycle (0 , 60°, 150°, 60°, 0°) of Tycko et al (3) was used. 

Multinuclear solid-state NMR experiments have been performed on cis-platin and four related square-planar compounds by Lucier et WURST-CPMG pulse sequence was utilized in NMR experiments to acquire i95pt, 35 1 uitra-wideline NMR spectra of high quality. From these... 

Very recently, the WURST-QCPMG sequence was developed to achieve uniform excitation of quadrupolar nuclei across very wide bandwidth using frequency-sweep chirped pulses [86]. The WURST (wideband uniform-rate smooth truncation) pulses provide broadband excitation. Integrating the WURST pulses with QCPMG results in the WURST-QCPMG method, which has proven to be a highly efficient approach for acquiring ultra-wideHne NMR spectra [74]. 

QCPMG and related sequences (e.g. CP- and WURST-QCPMG), and (3) the availability of first-principle calculations of NMR parameters for solids. The examples provided in this chapter clearly illustrate that Zn SSNMR spectroscopy is indeed a powerfijl tool for characterizing a wide range of zinc-containing materials from semiconducting nanoparticles to biological systems. 

Static Zr SSNMR spectra were acquired at 21.1 T in 7 h using the WURST-QCPMG pulse sequence. The Zr SSNMR powder pattern (Fig. 18 A) reflected a high degree of local ordering and yielded EFG param-... 

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