In-phase doublet

Figure Bl.13.8. Schematic illustration of (a) an antiphase doublet, (b) an in-phase doublet and (c) a differentially broadened doublet. The splitting between the two lines is in each case equal to J, the indirect spin-spin coupling constant.

Figure 3 Creation of the longitudinal order by cross-correlation as a function of the mixing time fm which follows the inversion of a carbon-13 doublet (due to a./-coupling with a bonded proton). The read-pulse transforms the longitudinal polarization into an in-phase doublet and the longitudinal order into an antiphase doublet. The superposition of these two doublets leads to the observation of an asymmetric doublet.

When measuring J couplings, one should keep in mind that the simple distance between peak maxima for a doublet is not always an accurate measure of the J coupling, especially if the peak width is similar to the J coupling. In-phase doublets creep together as peak... 

Figure 13 Pulse sequences of -detected IPAP DEPT-INADEQUATE.The insert is used when in-phase doublets are acquired. The filled and open rectangles represent 90° and 180° rectangular pulses, respectively, applied from the x-axis unless stated otherwise. The dashed rectangles of the DEPT pulse sequence represent rectangular pulses with flip angle 6 = 90° or 45°. The 180° BIBOP pulses are indicated as wide rectangles with a sine wave. The 13C adiabatic inversion pulses are designated by an inclined arrow. The following delays were used t = 0.5/Vch> At = 0.25/VCo A2 = 0.25/ycc. For other parameters see Ref. 31. Reproduced by permission of Elsevier.

This is a very nice result in F2 there will be an in-phase doublet centred at the offset of spin 1 (proton) and these two peaks will have an F1 co-ordinate simply determined by the offset of spin 2 (carbon-13) the peaks will be in absorption. A schematic spectrum is shown opposite. 

The first term on the right evolves during period C into in-phase magnetization (the evolution of offsets is refocused). So the final observable term is cos Q.2tx Ilx. The resulting spectrum is therefore an in-phase doublet in F2, centred at the offset of spin 1, and these peaks will both have the same frequency in Fv namely the offset of spin 2. The spectrum looks just like the HMQC spectrum. 

The calculation predicts that two two-dimensional multiplets appear in the spectrum. Both have the same structure in Fx, namely an in-phase doublet, split by (JX2 + J23) and centred at (Qx + 23) this is analogous to a normal multiplet. In F2 one two-dimensional multiplet is centred at the offset of spins 1, Qx, and one at the offset of spin 3, Q, both multiplets are anti-phase with respect to the coupling JX3. Finally, the overall amplitude, Bl3, depends on the delay A and all the couplings in the system. The schematic spectrum is shown opposite. Similar multiplet structures are seen for the double-quantum between spins 1 2 and spins 2 3. 

The DEPT experiment (Doddrell elal, 1982) involves a similar polarization transfer as the INEPT experiment, except it has the advantage that all the C signals are in phase at the start of acquisition so there is no need for an extra refocusing delay as in the refocused INEPT experiment. Coupled DEPT spectra, if recorded, would therefore retain the familiar phasing and multiplet structures (1 1 for doublets, 1 2 1 for triplets, etc.). Moreover, DEPT experiments do not require as accurate a setting of delays between pulses as do INEPT experiments. 

Fig. 21. Schematic illustration of MP-HNCA-TROSY antiphase (a) and in-phase (b) spectra with long acquisition time in q. The corresponding subspectra are shown after addition of the antiphase and in-phase data sets (c) and after subtraction of the antiphase and in-phase data sets (d). Due to very small Vcc > the intraresidual cross peaks are almost entirely cancelled out from the antiphase spectrum (a). In the subspectra, the intraresidual cross peaks are shown as doublets, separated by 53 Hz splitting in Fi-dimension, whereas sequential cross peaks are shown as singlets, and they exhibit 53 Hz offset for the upheld and downfield components between the subspectra.

Traces through the spectrum along co2 are shown in Fig. 7.10 together with the fitting of the coupled to the decoupled spectrum after convolution by an in-phase stick doublet. The fit delivers the coupling constant with high precision. The sensitivity of this experiment is practically identical to that of the HSQC experiment since the splitting is normally smaller or in the order of the line widths. 

Fig. 8.5 Downfield (a) and upfield (b) compo-nents of 15N doublets of a I PAP-[ H-15N]-HSQC for the protein saposin in Pfl viruses, a results from the subtraction and b from the addition of the spectra containing the in-phase and antiphase components, respectively. The sum of the...

Fig. 2.42 DSC desorption temperature from Table 2.17 versus powder particle size (BCD) of synthesized MgHj powders, (a) Onset temperature (T ) and (b) low-temperature (LT) and high-temperature (HT) peaks in a doublet. Numbers beside data points indicate the grain size of the MgH phases [63]...

Fig. 7. Spin states of a doublet (a) after a (Jt/2)j pulse (b) some time t later and its decomposition into an in-phase and an antiphase doublets.

The band resulting from the methylene rocking vibration (p CH2), in which all of the methylene groups rock in phase, appears near 720 cm-1 for straight-chain alkanes of seven or more carbon atoms. This band may appear as a doublet in the spectra of solid samples. In the lower members of the w-alkane series, the band appears at somewhat higher frequencies. 

Fourier transform infrared spectroscopy (FTIR) was also used to study the anisotropic structure of polyimide films. This work was based on the fact that there are characteristic absorptions associated with in-plane and out-of-plane vibrations of some functional groups, such as the carbonyl doublet absorption bands at 1700-1800 cm . The origin of this doublet has been attributed to the in-phase (symmetrical stretching) and out-of-phase (asymmetrical stretching) coupled... 

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