Band splitting

BF3 complexes 1260-1125 (s) 1030-800 (s) Band splitting may be added to isotopic splittings. 

The band structure of four concentric armchair tubules with 10, 20, 30, and 40 carbon atoms around their circumferences (external diameter 27.12 A) was calculated, where the tubules were positioned to minimize the energj for all bilayered pairs 17). In this case, the four-layered tubule remains metallic, similar to the behavior of two double-layered armchair nanotubes, except that tiny band splittings form. 

The IR spectra of several enaminoketones have been reported, and a study of these spectra has shown strong coupling between the C=0 and C=C stretching vibrations and band splitting due to rotational isomerism (7SciJJb). 

The band at 1994 cm observed at low CO coverage, was assigned to a monocarbonyl Rh(CO) species. The nature of the species observed at 2117cm has been elucidated using mixtures of different CO isotopes. As shown in Fig. 4, the band splits into three bands after adsorption of CO/ CO mixtures proving the presence of a dicarbonyl species... 

When the direct damping of the fast mode is strong, with that of the bending mode being weak, the lineshape (c) shows a broad shape involving a window that is due to the band splitting. 

In the opposite situation (y5 yG), lineshape (f), the band splitting vanishes such as the lineshape become close to the spectrum of an isolated fast mode (unique band, centered on the frequency oo0). 

These structural data demonstrate that 12 is a rather less distorted molecule than [2.2]paracyclophane. However, a dramatic effect of the strong cr(Si—Si)—w interaction was observed in UV spectra as shown in Fig. 5. In the UV spectrum of phenylpentamethyldisilane, an intramolecular crfSi—Si)—7T charge-transfer band appears around 231 nm (11a, 12). Octamethyltetrasila[2.2]ortho- (15) and metacyclophane (16) show similar absorptions, but the band splits into two bands at 223 nm (e = 19,100) and 263 nm (e = 22,500) in 12. This type of red shift in the UV spectra occurs only in 12 among other polysilapara-cyclophanes such as 13 and 14. 

The ex model has been elaborated in a number of ways. An electrostatic perturbation was added (33) to account for band splittings in the d-d spectra of tetragonal copper(II) ammine complexes where the simple AOM predicted accidental degeneracy the merits of this refinement will be discussed in 2.5.1. Another development has been the introduction of d—s and d—p mixing, which is apparently necessary to account for the d-d spectra of chlorocuprates(II) (34). This requires the additional parameters e, edpa and edpv. 

Background electrolyte, 122, 161, 188 Band splitting, 98 Band spreading, 167... 

Fig. 11. A plot of the Au5

Our XPS results on AU55 can also be examined to decide whether metallic shielding is present. The presence of a finite density of states at the Fermi level in AU55 was clearly detected in our XPS valence band spectrum, as indicated by the arrow in Fig. 10. This presence can be considered as an indication of metallic character in a cluster, even though this view has been questioned [74, 152,157]. In addition, the near full bulk value of the valence band splitting of AU55 is also... 

The dithionite reduction of the micelle encapsulated aqua (hydroxo) ferric hemes at pH 10 (in inert atmosphere) gives an iron (II) porphyrin complex whose optical spectrum [21] shows two well-defined visible bands at 524 and 567 nm and a Soret band split into four bands (Fig. 10). Such spectral features are typical of four-coordinate iron (II) porphyrins. The magnetic moment (p = 3.8 + 0.2 Pb) of this sample in the micellar solution is also typical of intermediate spin iron(II) system and is similar to that reported for four-coordinate S = 1 iron(II) porphyrins and phthalocyanine [54-56]. The large orbital-contribution (ps.o. = 2.83 p for S = 1) observed in this iron(II) porphyrin... 

ASOa-perovskites of Table 6 extends from Dza through Can to Ci. Distinct band-splittings are not observed, however, 13) (Fig. 2). As is demonstrated for the YCra Ali-a 03-system, the Oo-transition is situated at 13600 to 13700 cm i independent of the Cr3+ concentration (Fig. 2) leading to a B55 of 705 cm (Table 3), which is more than 5% lower than for the corundum and spinel compounds discussed. This is in agreement with the possibility of relatively strong Ji-bonds in the perovskite structure, which could be inferred from spectroscopic and crystallographic results 3) as well as from NMR-data and MO-calculations 33) for Ni2+,... 

We consider first (Fig. 14 a) what happens at very large distances. The Hamiltonian (11) (without the correction (35)) would then give rise to a very narrow band (a level). With the correction (35), the band splits into two separate sub-bands (two energy levels) Eo and Eq + Uh (see Fig. 14 a). These two sub-bands containing each M (and not 2M) states, represent, respectively, a state in which each core holds one spin and a state in which half of the cores hold two antiparallel spins, and the others empty (polar states). The two sub-bands are separated by a gap which is exactly Uh- Without excitation to the highest sub-band, in this conditions the lower sub-band is fully occupied. It represents the insulator s state in which all electrons are sitting in the cores, i.e. all electrons are fully localized. 

When the cores are approached, the sub-bands split, acquiring a bandwidth, and decreasing the gap between them (Fig. 14 a). At a definite inter-core distance, the subbands cross and merge into the non-polarized narrow band. At this critical distance a, the narrow band has a metallic behaviour. At the system transits from insulator to metallic (Mott-Hubbard transition). Since some electrons may acquire the energies of the higher sub-band, in the solid there will be excessively filled cores containing two antiparallel spins and excessively depleted cores without any spins (polar states). 

We may therefore assume that the 5 f non-spin-polarized band splits into two subbands because of spin-polarization. Approximation of the two sub-bands, according to Friedel s model, by two rectangular ones, having densities of state N+(E) = N (E) = 7/ Wf, and occupation numbers n+ and n, leads to the following expression for the total Pspd pressure ... 

If spin-orbit coupling is introduced the 1 = 3 band is replaced by the j = 7/2 and j = 5/2 bands. If spin-orbit coupling is large compared to the bandwidth these bands split, the j = 5/2 band filhng first. The parabolic trend in atomic volume is then replaced by a double parabola and minima are expected (for f electrons) at Uf = 3 and nf = 10 with maxima at nf = 6 and 14. In fact spin-orbit coupling is not large enough to completely... 

La2Cu04. The metallic compounds (a) are hypothetical materials without disproportionation or magnetic interactions which cause band splitting (b) when the o band is half filled. Both p-type (c) and n-type (d) conductors are shown. 

Interaction of two chromophores exhibiting allowed (strong) n-n absorption bands splits the excited state into two energy levels with the energy gap 2VSj (Davydov splitting), Figure 12. 

Crystallinity In crystallization of polymers, the polymer forms crystalline and amorphous regions [2,4,25]. The formation of crystalline regions is accompanied by an increase in new vibrational modes caused by their crystal lattice interactions [2]. The IR spectrum of a given polymer differs by various absorption bands, depending on whether it is in the amorphous or crystalline state [2]. The IR spectrum exhibits regularity bands, splitting, and frequency shifts. Other absorption bands are not affected by crystallization and remain the same in both cases. Crystalline and amorphous bands can be used in the determination of the degree of crystallinity independent bands are useful for the determination of sample thickness [2],... 

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