Multiplets, definition

Fig. 9.10 (A) Definition of the dihedral angle d between the spin-pairs ij and k,l. (B) Cross-correlated relaxation can be detected by differences in intensities of the multiplet components of double quantum coherences...

A complete decomposition of the ab initio computed CF matrix in irreducible tensor operators (ITOs) and in extended Stevens operators. The parameters of the multiplet-specific CF acting on the ground atomic multiplet of lanthanides, and the decomposition of the CASSCF/RASSI wave functions into functions with definite projections of the total angular momentum on the quantization axis are provided. 

With this definition, due to Child and Halonen (1984), local-mode molecules are near to the = 0 limit, normal mode molecules have —> 1. The correlation diagram for the spectrum is shown in Figure 4.3, for the multiplet P = va + vb = 4. It has become customary to denote the local basis not by the quantum numbers va, vh, but by the combinations... 

NMR. The 300 MHz iR-spectrum of V-2 in D2O is shown in figure 5a. The three multiplets between 1.4 and 2.05 ppm, the two double doublets between 3.4 and 3.7 ppm, and the multiplet between 3.6 and 3.8 ppm comply well with a hydroxylysine substituent at a ring nitrogen (fig. 5b, table 2). No definite conclusion as to the total number of protons can be drawn from the spectrum, since impurities seem to be present, for example singlets at 2.2, 2.05 and 1.95 ppm. The compound V-2 was purified further by ion exchange- and adsorption chromatography and a 500 MHz ID iH- (fig. 6b) and a 2D TOCSY-spectrum (in D2O) were run. Also here, the main spin system present is the hydroxylysine residue (fig. 5b). 

Although the 13C NMR provides quantitative information on the chlorination at the methyl site, it is less definitive for the backbone carbons. The multiplet centered at 44.3 ppm attributed to the methylene carbon in the main chain decreases at high chlorine contents as does the a-carbon peak. At the same time a close examination of the 13C NMR reveals the appearance of broad weak signals at about 54 and 68 ppm. These peaks may be due to chlorine substitution of the protons on the polymer main chain but this assignment is not definitive since the shift in peak position relative to the unchlorinated carbon is not as great as it would be expected for chlorine substitution. 

Protons are magnetically equivalent if they have the same chemical shift and are coupled equally to otiier equivalent nuclei in die molecule. This is similar to chemical equivalence but is a more rigorous definition of equivalence. For example, the methyl protons of isobutane are chemically and magnetically equivalent since they absorb at die same frequency and are all coupled equally to the methine proton (which should be split into a 10-line multiplet ). Likewise die two mediyl groups of /i-xylene are chemically and magnetically equivalent because they are coupled equally (J = 0) to the aromatic protons both ortho and meta to diem. 

The near IR spectra of the tetrakis(cumylphenoxy)phthalocyanines have not been reported before. The absorption in the Cu complex and one of the absorptions in the Co complex lie close to bands which have been tentatively assigned to trip-multiplet transitions in other phthalocyanines.(14) However, the other absorption bands shown in Table 1 have not been previously reported for phthalocyanines with no peripheral substitution. The small absorption cross sections of these bands in the cumylphenoxy phthalocyanines suggest that they are forbidden transitions. Possible assignments for these bands include a symmetry forbidden electronic transition (like the MLCT transitions in NiPc discussed above) becoming vibronically allowed, d-d transitions on the metal ion, or trip-multiplet transitions. Spectroscopic studies are in progress to provide a more definitive assignment of these absorptions. 

It should be noted that U differs from the usual definition of the Hubbard XJ, involving the lowest multiplet in each -configuration f/ n = E mn(n + 1) + Elmn(n — 1) — 2 mm(w). This second definition is inconvenient here, since it depends wildly on n. 

Although dianion [Rh fCOu,]2 " has never been isolated in the solid state owing to its lability, it can be considered a definite intermediate. In fact, it has a characteristic and reproducible lit spectrum, and at — 70°C it has a peculiar 13C magnetic resonance spectrum consisting of two doublets (191.7 and 208.3 ppm) and a multiplet (247 ppm) (74). 

An attractive alternative in which spectrometer line-listing routines are u.sed is as follows. After the spectral data have been Fourier transformed and saved, the proton FID is zero filled three to four times. If np = 32K, then Fn should be set to 256 or 512K. The resulting spectral lines should then have sufficient definition for peak picking. This expectation can easily be tested by examining a known multiplet, such as a triplet or quartet. The two- or three-line spacings are, of course, identical, and their equivalence must be reflected in the line listings displayed on the monitor. No matter what technique is used, J values between spin-coupled nuclei should always be reported as identical. 

Muscarine, the poisonous component of the death cap mushroom, has the structure below. We give the proton NMR spectrum. Can you see any definite evidence for the stereochemistry Couplings are in Hz, m stands for multiplet, and means that the proton exchanges with D2O. 

In atomic spectroscopy the term values depend primarily on electronic quantum numbers and the process of analysis consists of reducing a number of measurements to a term scheme. The confidence in an analysis increases as the system becomes more overdetermined, and the process becomes more definite as the accuracy of the measurements improves. Other information is also used to facilitate the assignments of the lines, e.g., relative intensities, the observation of certain lines in absorption, the splittings of lines by magnetic fields theoretical calculations of terms and multiplet splittings may sometimes be helpful. 

We note in passing that this definition of a strong field is not the one found in textbooks, which relates to the relative strengths of the Zeeman splitting and multiplet structure (the Paschen-Back effect). A field capable of inducing angular-momentum uncoupling can still be a weak field under the present definition.2... 

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