Structure near overlap

In a. p. and s.o. ZV(a) and ZV(i) samples, no ESR signals were detected. In a.p. ZV(acac), a weak ESR signal of vanadyl species was detected (5% of total V), absent after the s.o. treatment. The spectra of samples reduced with CO at 400 to 623 K consisted of a signal showing a resolved hyperfine structure (Vh), overlapping a broad (AHnp = 300 Gauss) and nearly-isotropic band (Vb, giso = 1 -97) (Fig. 3). When recorded at 77 K, both Vh and Vb maintained the same shape as at RT, and their Intensity as a function of temperature followed the Curie law. 

Fig. 4 Differential conductance dl/dV versus applied voltage V at 100 K. The differential conductance manifests a clear peak structure. Good reproducibility can be seen from the six nearly overlapping curves. Peak structures were observed in four samples measured at low temperatures although details were different from sample to sample. Subsequent sets of I-V measurements can show a sudden change, possibly due to conformational changes of the DNA. The inset shows an example of two typical I-V curves that were measured before and after such an abrupt change. Switching between stable and reproducible shapes can occur upon an abrupt switch of the voltage or by high current (from [14], with permission Copyright 2000 by Nature Macmillan Publishers Ltd)...

The electronic structure near the Fermi surface is crudely estimated in the tight binding approximation, where only the nearest neighbor overlap between the tt-orbitals is taken into account [125], The parameters (i.e. the tt-it overlap integral 7o 2.7 eV, and the lattice constant ao = 0.246 nm), are obtained from corresponding graphene calculations. For a graphene sheet [137],... 

The two main limitations of the current implementation of the nuclear-ensemble approach are clear in the simulations for furan First, the lack of vibrational resolution while the experimental results show a vibrational structure near the maximum, the simulations predict only the envelope of the band (the apparent oscillations are numerical noise). Second, the wrong band width for long-lived states long-lived states give rise to very thin peaks in the spectrum, which are not correctly described in the simulations. Both limitations are caused by the overlap-function approximation (Eq. 15), which neglects the excited-state wave packet evolution (see discussion in Sect. 2.6). 

Except for the Is orbital, the basis AOs are seen to have practically no resemblance to physical s-t3fpe orbitals. Most conspicuous is the absence of any internal nodal structure near the nucleus, corresponding to unphysical overlap (nonorthogonality) between core and valence functions. Within the ESS computer program, proper... 

With regard to the molecular structure of CCHn, both cyclohexyl rings having a chair conformation are substituted in the equatorial positions and the alkyl chain is completely extended in the all-trans conformation. The cyclohexyl rings are nearly coplanar. The crystal structures of the investigated CCHn show that various types of molecular overlapping are present in the crystal. The molecular packing in the crystalline state is quite different in all three compounds. 

A further comparison of structures 41 and 42 shows that the main difference between the structures occurs near this same reactive bond. Structure 42 represents the most stable conformation expected of Dalanyl-Dalanine, where the amide is trans substituted and the nitrogen is oriented so that its lone pair of electrons may overlap with the tt orbitals of the carbonyl group. In... 

H). As shown, a disordered structural model was obtained for the guest. The model comprises two mirror-related guest molecules. The oxygen atom and the proximal methyl C-atom are practically overlapping the same atomic positions in both orientations. However, the sulphur atomic positions do not average in the X-ray data and show a nearly 50/50 occupancy. As indicated by the comparison of the respective bond distances and intra-associate contact distances of the DMSO molecule (Table 17), the effect of disorder is serious (e.g. the S=0 distances appear abnormally short in the 20 DMSO instance). This precludes the possibility of assessing interaction between the O atom of the carboxyl and a methyl of dimethyl sulfoxide. 

An extended Hiickel MO calculation supports the assumptions made in the above analysis in that the three t2g orbitals are indeed close together in energy and remain nearly nonbonding metal-based d-orbitals. The detailed agreement is less satisfactory the SOMO is predicted to be primarily dx2 y2 with a small dxz admixture (hybrid 6 of Table 4.13), a result that can be ruled out from our analysis of the ESR results. The EHMO overlap matrix based on the X-ray structure suggests that the molecule is much closer to C2 symmetry than to Cs. If we accept that conclusion, then dxzjdxy hybridization is less likely than dyjdxy, as we tacitly assumed above. 

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