Inversion profile

The anti-symmetrized PIP8(0°, 0°-144°-0°, 50 ps, 1.3213 kHz, 10) (Fig. 8) is taken into account first. Figure 10 shows the inversion profile of the PIP8as and Table 6 lists the scaling factors, RF field strengths, phases, and polarizations for n= — 2 to 2. For the PIP8as, the UPS= —72° for all bands is compensated and a phase inversion occurs if n is odd (Table 6), in agreement with the previous conclusions. Another phase inversion appears for X < 0 (n = — 2 and — 1) as discussed in Section 2.2. 

Fig. 10. The inversion profile (n = —2 to 2) created by an anti-symmetrized PIP8(0°, 0C-144° 0°, 50 is, 1.3214 kHz, 11). Due to the RF interference, all the peaks are shifted slightly and the shifted amounts can be calculated with the NNA as shown in Table 7. Reprinted from Ref. 33 with permission from the American Institute of Physics publications.

Similar compensation effects were also found for a pulse strength of fi = 11.11 kHz and In Aft = 2jt (m = 2). The inversion profile of the pulse is shown in Fig. 13b, together with the inversion profile by a single PIP (a). The null region of the 13C is broadened significantly by the simultaneous PIPs in addition to the compensation of the BSPS. 

Due to the BSOS discussed in Section 4.3, the inversion profiles are shifted by 1.38 kHz to the left and right side, respectively (Fig. 13b). The amount of the shift compared to the bandwidth of the inversion profile is significant. To have a right position of inversion, the effect of the BSOS needs to be taken... 

As shown in Fig. 21a, the simulated broadband inversion profile by the three PIPs resembles the profile by the composite pulse 90°180°90° except for a different excitation region. The inversion profile is severely distorted (Fig. 21b) if the three initial phases, phase relationship in the rotating frame is the wrong one in the Eigenframe. The phase coherence in PIPs needs to be considered even for PIPs with the same frequency shift, A/ = 50 kHz in this case. 

There are many tricks to get around the problem, such as sandwich 180° pulses (e.g., 90 -180 -90 ) and broadband shaped pulses. Figure 8.4 (top) shows the inversion profile for a simple 180° pulse at the highest available power (fp = 28.4 p,s, yB l2it — 17.6 kHz). The profile is obtained using an inversion-recovery sequence (180°x — r — 90° ) with recovery time r = 0. The final 90° pulse frequency and the 13C peak (13CH3l) are both at the center of the spectral window, but the frequency of the 180° pulse is moved in 10 ppm (1500 Hz)... 

The 180° inversion and refocusing pulses are particularly critical. When applied as simple rectangular pulses, these fail to cover the complete range of 13C frequencies even at lower field instruments. Smoothened chirp pulses show much better inversion profiles (Figure 6 A) and have been implemented into the ADEQUATE pulse sequence.28 These pulses are not suitable as refocusing pulses... 

Figure 9.14. Simulated excitation profiles of selected shaped pulses (of 10 ms duration) see Table 9.3. The inversion profiles (lower trace) were simulated with a 180(soft)-90(hard) sequence.

As apparent from the previous section, a binomial sequence has a suitably tailored profile for the element S, and the series 3a-9a-19a-19a-9a-3a (Fig. 9.28a, with 26a =180° and a delay t between pulses, here termed W3 [71]) has a desirable off-resonance inversion profile for this purpose. The WATERGATE excitation profile for this is shown in Fig. 9.29a. Once again characteristic nulls also occur at offsets of n/x Hz, but between these the excitation is quite uniform and does not suffer the phase inversion of the unaccompanied 90° binomials. More recently, extended binomial sequences have been shown to provide a narrower notch at the transmit-... 

The excitation profile depends only on the inversion profile of S, not its phase properties. 

Figure 10.10. The simulated inversion profiles of (a) 20% smoothed CHIRP, (b) WURST-20 and (c) 25-ps haid 180° pulse. For both (a) and (b), a 60 kHz sweep was employed over 0.5 ms pulse with 7Bi(max/...

Figure 10.13. The simulated inversion profiles of (a) the 100-ps BIP-720-50-20 and (b) 25-ps hard 180° pulse. Both pulses use 751 = 20 kHz. The profiles were generated with a 180°. j -90°(hajd)j sequence over two transients to reveal the inverted component.

Current and historical meteorological monitoring-network data confirm that under night-time conditions, cold air from the mountains typically flows downward into the canyons and arroyos and fans onto the flat terrain. These cold-air-drainage winds can be very shallow, with depths occasionally less than 50 or 100 m (164 to 328 ft). In add rtion, nocturnal cooling complicates the area s temperature-inversion profile. 

Fig. 19.2 Cyclohexene ring inversion profile calculated by MP2/6-31G(d,p) method using intrinsic reaction coordinate...

Thus, ring inversion profile in cyclohexene strongly differs from classical form due to its top-flattened shape. It is possible to suggest that this difference is caused by correlation between changes of geometrical parameters of ring during... 

It is quite clear that unusual character of ring inversion profile in cyclohexene is determined by subtle balance of intramolecular interactions. Therefore replacement of one methylene group by exocyclic double bond should lead to some changes of these interactions accompanied by change of equilibrium conformation as well as ring inversion pathway. 

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