Residual zero frequency line

At this point it has been established that there are at least two basic mechanisms which contribute to the broad lines that are observed for the crystalline polymers. The residual zero frequency line broadening component can be analyzed in more detail. Specific attention can be given to factors which are a consequence of the chain-like character of the molecules. The local field at a given nucleus is the sum of the individual fields contributed by the neighboring magnetic nuclei. Segmental motions will induce a time dependence to the variables so that the individual contributions can be described by the equation (46)... 

Figure 4.16 Left-hand side R(7) of the fundamental acetylenic C—H stretch rovibrational spectra of (CHjljCC CH (above) and (CHjljSiC CH (below). Right-hand side R(5) of the overtone acetylenic C—H stretch rovibrational spectra of (CH3)3CC H (above) and (CH3)3SiC CH (below). In all four cases the measured rotational line and a nonlinear least-squares fit to a single Lorentzian are shown in the upper traces, while residual of the Lorentzian fit and the zero line are shown in the lower traces. (For the sake of clarity upper and lower traces are staggered.) The residuals indicate a true Lorentzian line shape for the carbon compound as expected for the statistical regime of IVR. For the silicon compound the fit to a single Lorentzian is not as exact. The small residuals at the low-frequency side for Si compound (below) in both the fundamental and the overtone are likely due to two isotopes of Si with 4.67% and 3.1 % natural abundance or to a hot-band transition (Kerstel et al., 1991).

II.5 " H NMR background Fast, anisotropic reorientations of a C-D bond lead to a quadrupolar interaction which is no longer averaged to zero. ° When motions are uniaxial around a macroscopic symmetry axis, such a residual interaction splits the liquid-like NMR line into a doublet whose spacing is in frequency units ... 

The INADEQUATE and APT spectra for the major product are shown in Figure 7. In an INADEQUATE spectrum, the pairs of adjacent carbons, and hence the connectivity, can be mapped out similarly to a COSY spectrum. The major difference here is that the original spectrum is not on the diagonal in an INADEQUATE spectrum (as in a COSY spectrum), but is in the x-axis direction (= normal C frequencies) along the line = 0 (residual single quantum signals). The y-axis is the frequency v, the double quantum frequency that is the sum of the frequencies of the two coupled nuclei referenced to a transmitter frequency at zero. The peaks arising from two coupled nuclei (here adjacent carbons) with shifts and Vj, have coordinates of (( a + ) where X is the frequency of the carbon... 

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