Selective inversion DANTE

Fig. 2. (a) 400 MHz partial H spectrum of a trisaccharide in CDClj. (b)-(e) ID TOCSY difference spectra with selective inversion of Hj// by a DANTE pulse train, and mixing times of 30, 60, 120 and 180 ms, respectively. IOtz values (of 16 scans each) were used for the 2-filter. (Reproduced with permission from Wessel et al. [26a]. Copyright 1991 Verlag... 

Aspects of the experimental implementation of the technique have been studied in detail [41] and it has been shown that double sideband modulation and pulse shaping can be combined to improve the performance of selective pulses in solid state 2H NMR. Applications of the selective inversion-recovery experiment using a DANTE sequence to study ultraslow motions have been demonstrated [42,43]. 

Figure 20 Saturation transfer experiment using (a) Selective inversion by a shaped pulse or (b) a DANTE pulse sequence. Do not use the DANTE-Z sequence, Section 3.3, in saturation transfer experiments...

The excitation sculpting method was expended to the selective inversion of z-magnetisation. The method utilises DANTE train of hard pulses combined with gradient suppression of transverse magnetisation. Application of the selective inversion to z-magnetisation reduces relaxation loses and extends selective methods to larger molecule. Use of shaped pulses in DANTE train produces band-selective inversion. The proposed inversion method can be... 

To generate an exchange curve, one of the two resonances involved must be inverted selectively. By whichever technique a selective inversion is carried out, it is important that the other resonances not be perturbed. The most frequently used inversion techniques in RR experiments are a long, soft pulse or an asynchronous DANTE (delays alternating with nutation for tailored excitation) sequence. 

When implementing this sequence it may be necessary to add attenuation to the transmitter to increase the duration of each pulse so that the shorter elements do not demand very short (< 1 xs) pulses (note the similarity with the requirements for the DANTE hard-pulse selective excitation described above). The binomial sequences can be adjusted to provide an arbitrary overall tip angle by suitable adjustment of the tip angles for each element. For example, inversion of all off-resonance signals can be achieved by doubling all elements relative to the net 90 condition. Exactly this approach has been exploited in the gradient-echo methods described below. 

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