Vibrational states electrical properties

For the HF molecule, we have rigorously evaluated the vibrational-electronic state electrical properties. For about a dozen bond length choices, electrical properties for HF were calculated. An ACCD potential energy curve, accurate enough to predict the r = 0 -mj = 1 field-free transition... 

The state of polarization, and hence the electrical properties, responds to changes in temperature in several ways. Within the Bom-Oppenheimer approximation, the motion of electrons and atoms can be decoupled, and the atomic motions in the crystalline solid treated as thermally activated vibrations. These atomic vibrations give rise to the thermal expansion of the lattice itself, which can be measured independendy. The electronic motions are assumed to be rapidly equilibrated in the state defined by the temperature and electric field. At lower temperatures, the quantization of vibrational states can be significant, as manifested in such properties as thermal expansion and heat capacity. In polymer crystals quantum mechanical effects can be important even at room temperature. For example, the magnitude of the negative axial thermal expansion coefficient in polyethylene is a direct result of the quantum mechanical nature of the heat capacity at room temperature." At still higher temperatures, near a phase transition, e.g., the assumption of stricdy vibrational dynamics of atoms is no... 

In the present study, the y values of the compounds were determined by measuring the Cp values at very low temperatures. Also, the y values obtained were compared with the DOS calculated by the DV-Xa molecular orbital method [4], In addition, the Debye temperature, the standard entropy of formation, the electric resistivity p and the thermal conductivity k were further determined for each compounds. The physico-chemical properties of the compounds were discussed from both views of the electronic and lattice vibration states. 

The fundamental requirement for the existence of molecular dissymmetry is that the molecule cannot possess any improper axes of rofation, the minimal interpretation of which implies additional interaction with light whose electric vectors are circularly polarized. This property manifests itself in an apparent rotation of the plane of linearly polarized light (polarimetry and optical rotatory dispersion) [1-5], or in a preferential absorption of either left- or right-circularly polarized light (circular dichroism) that can be observed in spectroscopy associated with either transitions among electronic [3-7] or vibrational states [6-8]. Optical activity has also been studied in the excited state of chiral compounds [9,10]. An overview of the instrumentation associated with these various chiroptical techniques is available [11]. 

The vibrational excursions of a molecule may cause it to have sharply changing electrical properties from state to state. This, of course, is essential for mechanisms of absorption and emission of radiation. How sharp these changes may be is illustrated for HF in Figure 3. The curves show the axial elements of a. A, and P in the vicinity of the equilibrium bond length as a function of the H-F distance. The types of changes that may be found in a polyatomic molecule are illustrated by Figures 4 and 5. They show contours of the dipole polarizability and hyperpolarizability elements over the two stretching coordinates of HCN. Both and P yy have zero contours... 

As Werner and Meyer [91] and Adamowicz and Bartlett [70] have clearly explained, molecular electrical properties have another contribution from vibrational motion. Recall that each electrical property is strictly defined as a derivative of the molecular state energy with respect to elements of V. 

In this analysis and in that of the next section, the vibrational motion effects presume a field source that is rotating with the molecule, such as when the electrical perturbation is due to a weakly complexed partner molecule. A freely rotating molecule in a laboratory-fixed field source, however, is different, and then evaluations of electrical properties should account for rotational state dependence as well [114, 115]. 

An important property of molecules is the behavioiu of the electric dipole moment function near the equilibrium configuration, and the changes which oc cur on vibrational excitation. Electric resonance studies of the HCl molecule in its electronic ground state, carried out by Kaiser [90] are important in this respect, and also in showing, through the Cl quadrupole interaction, how the electric field gradient changes on vibrational excitation. 

Local electronic and vibrational states, created by impurities and defects near the surface, are essentially different from those in the bulk of a sample. It will be shown below that in nanomaterials (i.e. in the materials consisting of nanoparticles) all the properties (magnetic, electric, conducting etc.) are essentially different from those in ordinary bulk samples. We emphasize once more, that the physical properties, which are spatially homogeneous in bulk samples, become essentially inhomogeneous in nanomaterials due to surface influence. 

When the hydrophobic and electrical properties do not favor enolization and ionization of Ce=0 then an orientation effect should be considered. Indeed, another possible interpretation is based on the short-range effects 2 of fhe SERS enhancement factors and on specific orientations of the guanine derivates at the silver surface. As the electromagnetic model predicts, a very rapid decrease of SERS effects with distance on the A scale would limit the enhancement factors to bond vibrations in the immediate vicinity of the silver surface. The dispari-tion of the carbonyl stretching vibrations in SERS spectra of 3-Me-Gua and 9-Me-Gua would thus suggest that the C6=0 bond lies far away from the surface. The hypothesis of an "inactive" SERS carbonyl vibration would consider orientations for both methylted guanines in the adsorbed state different from the other derivatives. In 1-Me-Gua and 7-Me-Gua the Ce O... 

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