Pulse adiabatic

Adiabatic pulse A type of pulse employing a frequency sweep during the pulse. This type of pulse is particularly efficient for broadband decoupling over large sweep widths. 

The idea of using the linear phase increments to achieve frequency-shifted excitation can be adopted almost to any pulses, such as hard (amplitude fixed) pulses, shaped pulses, and even adiabatic inversion pulses. Unlike any other pulses, the adiabatic pulses have already used non-linear phase increments for tilting the effective RF field slowly compared with the Larmor frequency of the spins in the rotating frame in order to fulfill the adiabatic condition. 

Adiabatic pulses are usually composed of a number of back-to-back pulses of equal width Ar. The amplitude adopts a certain shape that is normally... 

There are two limitations for using the off-resonance approach. RF pulse strength is one of these, as it defines the frequency range which can be covered with reasonable uniformity. This becomes a more difficult issue when other than H spectra are concerned, such as the case of C-HoMQC [16, 24, 25]. The applicable pulse power is limited by the hardware, especially by the probe. In such cases application of adiabatic pulses may provide a promising alternative to cover large frequency windows. 

Figure 6 Typical pulse sequence used in experiments with a signal-enhancement scheme (which can involve DFS, RAPT or application of adiabatic pulses) placed before the CT excitation and detection, with formation of a spin-echo.

There are several parameters which need to be optimised for the achievement of fhe highest possible CT enhancement with minimal line-shape distortion. With optimal settings, HS and other adiabatic pulses usually give the highest enhancements (close to the theoretical limits of 21 for perfecf ST inversion), when compared to other methods such as DFS and Even without detailed optimisation, it is usually found... 

L. A. O Dell, K. Klimm, J. C. C. Freitas, S. C. Kohn and M. E. Smith, S MAS NMR of a disordered sulfur-doped silicate signal enhancement via RAPT, QCPMG and adiabatic pulses. Appl. Magn. Reson., 2008, 35, 247-259. 

A. J. Pell, G. Kervem, L. Emsley, M. Deschamps, D. Massiot, P. J. Grandinetti and G. Pintacuda, Broadband inversion for MAS NMR with single-sideband-selective adiabatic pulses. /. Chem. Phys., 2011,134, 024117. 

E. Kupce and J. Freeman, Adiabatic pulses for wideband inversion and broadband decoupling. J. Magn. Reson. A, 1995,115, 273-276. 

As expected, increased magnetic field substantially improves MRS of the heart, as demonstrated in two recent reports. ° Bottomley and co-workers extended their previous quantitative cardiac P MRS methods to 3T by incorporating adiabatic pulses of increased bandwidth to reduce SAR and a dual TR method to measure They report P TiS at 3T for PCr and ATP in both heart muscle and skeletal muscle. 

P. A. Bottomley and R. Ouwerkerk, The dual-angle method for fast, sensitive T-1 measurement in-vivo with low-angle adiabatic pulses. /. Magn. Reson. B, 1994, 104, 159-167. 

A.-M. El-Sharkawy, M. Schar, R. Ouwerkerk, R. G. Weiss and P. A. Bottomley, Quantitative cardiac P spectroscopy at 3 Tesla using adiabatic pulses. Magn. Reson. Med., 2009, 61, 785-795. 

Robitaille, P.M., Merkle, H., Sublet , E., Hendrich, K., Lew, B., Path, G., From, A.H.L., Bache, R.J., Garwood, M., Ugurbil, K. (1989). Spectroscopic imaging and spatial localization using adiabatic pulses and applications to detect transmural metabolite distribution in the canine heart. Magn. Reson. Med. 10,14-37. 

The combined use of adiabatic inversion and composite adiabatic pulses can have a dramatic effect on the sensitivity of 1,1-ADEQUATE on a 600-MHz NMR spectrometer as illustrated on spectra of cholesteryl acetate in Figure 7 28... 

In an alternative approach, the coherence transfers may be achieved using adiabatic pulse sequences under MAS conditions as featured, in particular, by Meier and coworkers in the context of H —> as well as N and C —>... 

E. H. Hardy, A. Detken and B. H. Meier, Fast-NMR total through-bond correlation spectroscopy using adiabatic pulses. J. Magn. Reson., 2003, 165. 208-218. 

Adiabatic pulses and isotropic mixing Use of adiabatic pulses for C,C and H,H TOCSY transfer, HCCH-TOCSY... 

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