Excitation model, local

The dynamics of polysilane dendrimer excited states were also studied by Watanabe as mentioned above in a comparison with polysilynes,360,364 and suggested that a configuration coordinate model is applicable to the photophysics of branched silicon chains. Calculations showed a distorted geometry of the excited state localized at a branching point. 

Figure 12. Excitation of the singular mode Ns as a function of the external pump parameter (phonon flux

Raman spectra for the sample were conducted in a compression-decompression cycle. In this experiment, the crystalline diffraction began to disappear above 7-8 GPa during compression, and pressure-induced amorphization was indicated by the Raman spectra above 13 GPa (Fig. 14). The resultant HDA Si exhibits the Raman spectrum that differs from the spectrum of normal -Si (LDA Si). Rather, the characteristics of the spectrum for HDA Si resemble those of the (3-tin crystal, which indicates that HDA Si has a (locally) analogous structure to the (3-tin structure. The synthesis of the HDA form of Si by Deb et al. [263] has a strong resemblance to that of water (ice) by Mishima et al. [149, 196]. Whereas compression induced amorphization that was almost completed at 13-15 GPa, decompression induced an HDA-LDA transition below 10 GPa, which is clearly shown in the Raman spectra (Fig. 14). This is the first direct observation of an amorphous-amorphous transition in Si. The spectrum at 0 GPa after the pressure release exhibits the characteristic bands of tetrahedrally coordinated -Si (LDA Si). Based on their experimental findings Deb et al. [263] discussed the possible existence of liquid-liquid transition in Si by invoking a bond-excitation model [258, 259]. They have predicted a first-order transition between high-density liquid (HDL) and low-density liquid... 

It was extremely exciting to localize these features and build models for them. When I stepped back to see the arrangement, the unexpected observation about it was symmetric. There was a symmetry in the arrangement of the chlorophyll that nobody had anticipated. Nobody, to this day, completely... 

The state function of S2 becomes a complicated one in the MIM calculations(Table 3), in contrast with the single function VS-t i the PPP method. On the other hand, the state function of S- is expressed by a simple B2u function in the MIM method although it becomes very complicated in the PPP method. These features reflect the characteristic of the model adopted in each of the two methods MO is constructed by all the AO of the molecule in the PPP method and by the AO of each chromophore in the MIM method.(see Fig.l) From these discussion we can realize that S2 is a excited state spread all over the molecule( also see MO 6 and 7 in Table 2), and S- is a excited state localized in benzene ring and also realize the importance of the selection of the theoretical model in the comprehensive understanding of the experimental phenomena. 

A more direct evidence of the surface localized excitation mechanism has been obtained by a polarization dependence study. For K/Pt(lll) at 0.36 ML, it has been demonstrated that the coherent excitation of the K—Pt stretching mode occurs with p-polarized excitation and not with s-polarized exdtation. Since the s-polarization absorptance is about one fourth of that with p-polarization under the experimental conditions (2.19 eV photon energy, 70° angle of inddence), the coherent amplitude should be detectable with s-polarization if the substrate-mediated process operates. Therefore, the negligible oscillatory component with s-polarization is inconsistent with the substrate-mediated excitation model and it is indicated that some electronic transitions involving K-induced surface states are responsible for the coherent excitations. 

Energy migration among a number of chromophores with inhomogeneously broadened spectra can be modeled using a Pauli master equation approach [10, 27, 70, 71, 103-107] as long as the excitation is localized as it hops from... 

The electromagnetic enhancement mechanism features the major contribution to the overall enhancement of SERS. It is based on the generation of an electromagnetic field at the surface of nanostructured metal surfaces due to the interaction of an incident electromagnetic field and the excitation of localized surface plasmon polaritons. To explain this phenomenon in more detail, a simple model can be used. A simple metal nanosphere with a size smaller than the wavelength of the incident light is considered for this purpose. This metal nanosphere is surrounded by a medium or vacuum with a dielectric constant Eq, and all appearing processes are assumed to be quasi-static. The dielectric constant inside the metal nanosphere is independent of the size of the sphere and is described as follows ... 

It is interesting to see that for both dopants (pentacene and terrylene) in p-ter-phenyl optical dephasing seems to be induced by a librational mode. This model is strengthened by the observation of dilferent activation energies for the two chromo-phores which gives further evidence that the low frequency excitations are localized at the impurities. 

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