Pulse sequence diagrams for

Figure 7. Pulse sequence diagram for an HXY triple resonance 3D-NMR, open rectangles represent 180°pulses and solid rectangles represent 90°...

Figure 18. Pulse sequence diagrams for 3D H(CA)P-CC-TOCSY (a) and HCCH (b) experiments. (Reproducedfrom reference 19. Copyright 2001 American Chemical Society.)...

Figure 6. Pulse sequence diagram for the F C PFG-HSQC experiment. Solid and open pulses are 90° and 180° respectively. Phase cycling is that used by the standard HSQC sequence provided by Varian.

Figure 7.16 Pulse sequence diagram for Tj CPMG experiment. The dashed line on the echoes shows the rate at which spins lose coherence among themselves. Spin states are reported at specific times (a) net magnetisation flipped onto the transverse plane for signal detection (b) spins dephasing from the y direction (c) P gQ pulse which reverse spins instantaneous phase angles (d) spins rephasing towards the y direction. Panels (e) and (f) show spins in-phase states (signal echoes).

Figure 7.17 Pulse sequence diagram for T, IR experiment. The thick dashed line shows the T recovery rate of the longitudinal magnetisation with B,j. Spin states are reported at specific times (a) the magnetisation is reversed (b) partial T recovery of spins in alignment with the Bg magnetic field (c) spins that have partially or fully recovered are flipped onto the transverse plane for signal detection (d) partial loss of coherence among spins and (e) total loss of rotational coherence among spins.

Figure 7.19 Pulse sequence diagram for solid-echo experiment. The detected signal (red line) is composed of an exponential decay part and a Gaussian part. (Adapted from Valori et al. 2013.)...

We usually ignore relaxation during short delays (e.g., 1/(2J) is usually milliseconds or tens of milliseconds) and consider it only when relaxation is essential to the experiment (e.g., inversion-recovery or nuclear Overhauser effect (NOE) experiments, typically hundreds of milliseconds or seconds for small molecules). Pulses are very short (tens of microseconds), so we do not usually worry about either evolution or relaxation during pulses. Although pulses may look fat in pulse sequence diagrams, they are really much shorter than most delays and their duration is not important in terms of evolution. Pulses lead to rotation of the net magnetization vector around the B axis, always in the counterclockwise direction. 

Coherence Order. The coherence order, p, is zero for z magnetization and zero-quantum coherence, 1 or -1 for single-quantum coherence, and 2 or -2 for doublequantum coherence. The coherence order is useful for diagraming the coherence pathway in a pulse sequence and for predicting the effect of gradient pulses on the sample magnetization. 

Figure Bl.15.12. ESEEM spectroscopy. (A) Top energy level diagram and the corresponding stick spectrum for the two allowed (a) and two forbidden (f) transitions. Bottom time behaviour of the magnetization of an allowed (a) spin packet and a forbidden (f) spin packet during a two-pulse ESE sequence (see figure Bl.15.11 (A)). (B) The HYSCORE pulse sequence.

The DDIF experiment consists of a stimulated echo pulse sequence [50] and a reference scan to measure and separate the effect of spin-lattice relaxation. The pulse diagrams for these two are shown in Figure 3.7.2. Details of the experiments have been discussed in Ref. [51] and a brief description will be presented here. 

Figure 9 Timing diagram of the BIRD-HMBC pulse sequence for the detection of nJch correlations, including an additional two-step low-pass J filter. Thin and thick bars represent 90° and 180° pulses, respectively. 13C180° pulses are replaced by 90°y — 180°x — 90°y composite pulses. <5 is set to 0.5/(Vch) and A is set to 0.5/("JCH). Phases are cycled as follows fa = y, y, —y, —y 4>j = x, —x fa — 8(x), 8(—x) fa = 4(x), 4(— x) ( rec = 2 (x, — x), 4(—x, x), 2(x, —x). Phases not shown are along the x-axis. Gradient pulses are represented by filled half-ellipses denoted by Gi-G3. They should be applied in the ratio 50 30 40.1.

Figure 20 Timing diagram of the suggested 2y,3y-HMBC experiment, including a LPJF3 for efficient 1JCH suppression. The sequence is virtually identical to the CIGAR-HMBC pulse sequence. The STAR operator is also a constant-time variable element. In this fashion, scalable F, modulation can be specifically introduced for 2JCH cross-peaks into the spectrum independently of the digitization employed in the second frequency domain.

Fig. 5 Symmetry-based dipolar recoupling illustrated in terms of pulse sequences for the CN (a) and RNvn (b) pulse sequences, a spin-space selection diagram for the Cl symmetry (c) (reproduced from [118] with permission). Application of POST-CVj [31] as an element in a H- H double-quantum vs 13C chemical shift correlation experiment (d) used as elements (B panel) in a study of water binding to polycrystalline proteins (reproduced from [119] with permission)...

Fig. 4 The top diagram represents the pulse sequence for the cross-polarizatior experiment the bottom diagram describes the behavior of the H and l3C spin magnetizations during the sequence. The steps in the two diagrams correspond to each other anc are fully explained in the text. (From Ref. 15.)...

Fig. 8 Schematic diagrams for the following pulse sequences (A) single pulse excitation/magic-angle spinning, (B) total suppression of sidebands, and (C) delayed decoupling, or dipolar dephasing.

Figure 1. Schematic diagram of the solid-state NMR pulse sequences for (a) quantitative single pulse 13C observe with gated decoupling and (b) Ti and (c) 13C Ti determinations via cross polarization.

Fig. 1. Basic pulse sequence and CP diagram for gradient-based spin-locked ID exf>eriments. A 1 (— 1) 2 gradient ratio selects N-type data (solid lines) while 1 (— 1) (—2) selects P-type data (dashed lines). When SL stands for a -filtered DIPSI-2 pulse train, a ge-lD TOeSY is performed. On the other hand, when SL stands for a T-ROESY pulse train, a GROESY experiment is performed. S stands for the gradient length.

Figure 2 Pulse sequences and coherence pathway diagrams for the phase-modulated split-t) (A) STMAS and (B) triple-quantum MAS NMR, showing the generic sequences with the specific values for Mg being r=24/31, r —O, r"=7/31 and s=12/31, s =0, s"— 9/3 and (C) numerical simulations of the relative sensitivity of the ST and MQ experiments as a function of the ratio between the RF field strength and the quadrupolar coupling...

Fig. 1. Feynman diagrams for the interaction of a three-pulse sequence with a two-level system.

Below the pulse sequence we can show the desired coherence level, p, at each stage of the pulse sequence. This diagram defines the coherence pathway that is desired for a particular NMR experiment. Coherence order is mixed for Cartesian product operators... 

For a series of pulses (a pulse sequence), we can select the change in coherence order Ap resulting from each of the pulses if we phase cycle all of the pulses and then calculate the effect of the desired coherence pathway on the final phase. If we diagram the coherence pathway, we can note the change in coherence order Ap caused by each pulse and then calculate the receiver phase change necessary to make the desired combination of Ap s add together at the receiver while all other pathways cancel ... 

---