Search results for "Polarizability"
showing 10 items of 240 documents
Gas-phase and solution basicities of some alkyl 2,6-dialkylphenyl ketones: A comparative analysis
2000
Abstract The gas-phase basicity of a number of alkyl 2,6-dialkylphenyl ketones (2,6-R2C6H3COR′) has been found to be almost insensitive to structural variations, as a result of a compensation of steric and electronic effects associated with the bulkiness and to the polarizability, respectively, of R and/or R′. On the contrary, the basicity in concentrated sulfuric acid undergoes, along the same series of compounds, a variation of nearly 8 pK units, as a consequence of steric inhibition of solvation of the protonated carbonyl as the main effect played by R and/or R′. The results in the condensed phase agree very nicely with recent findings relevant to some 4-substituted 2,6-dimethylacetophen…
ChemInform Abstract: Gas-Phase and Solution Basicities of Some Alkyl 2,6-Dialkylphenyl Ketones: A Comparative Analysis.
2000
Abstract The gas-phase basicity of a number of alkyl 2,6-dialkylphenyl ketones (2,6-R2C6H3COR′) has been found to be almost insensitive to structural variations, as a result of a compensation of steric and electronic effects associated with the bulkiness and to the polarizability, respectively, of R and/or R′. On the contrary, the basicity in concentrated sulfuric acid undergoes, along the same series of compounds, a variation of nearly 8 pK units, as a consequence of steric inhibition of solvation of the protonated carbonyl as the main effect played by R and/or R′. The results in the condensed phase agree very nicely with recent findings relevant to some 4-substituted 2,6-dimethylacetophen…
Resolving the forbidden band of SF6
2013
Sulfur hexafluoride is an important molecule for modeling thermophysical and polarizability properties. It is also a potent greenhouse gas of anthropogenic origin, whose concentration in the atmosphere, although very low is increasing rapidly; its global warming power is mostly conferred by its strong infrared absorption in the ν3 S-F stretching region near 948 cm(-1). This heavy species, however, features many hot bands at room temperature (at which only 31% of the molecules lie in the ground vibrational state), especially those originating from the lowest, v6 = 1 vibrational state. Unfortunately, the ν6 band itself (near 347 cm(-1)), in the first approximation, is both infrared- and Raman…
Effects of Crystal Field Splitting and Surface Faceting on the Electronic Shell Structure
1992
The shell structure of the valence electrons is clearly observed in all alkali and noble metal clusters containing up to hundreds of atoms[1 – 4]. It is seen in the abundances of the clusters, in the ionization potential and in the polarizability. The shell structure of the valence electrons is closely related to the shell model of nuclei, but is simpler owing to the negligibly small spin-orbit interaction. The ability to produce all sizes of metal clusters has made the metal clusters a test ground for the super-shell structure[5].
Theory of birefringence and spontaneous polarization in the tetragonal phase of PbTiO3 due to lattice deformation caused by the change of temperature
1995
The microscopic mechanism of birefringence in the tetragonal phase of PbTiO3 is discussed taking account of the dipole-dipole interaction (dipole-dipole effect) due to the ionic and electronic polarizations of the crystal and the spontaneous Kerr effect as a cause of the strong local field acting on the constituent ions, where the lattice deformation due to the change of temperature is also considered. For the spontaneous polarization we use only the first effect. It is found that the birefringence and the spontaneous polarization are in good agreement with the experimental data.
CF3: An Electron-Withdrawing Substituent for Aromatic Anion Acceptors? “Side-On” versus “On-Top” Binding of Halides
2016
The ability of multiple CF3 -substituted arenes to act as acceptors for anions is investigated. The results of quantum-chemical calculations show that a high degree of trifluoromethyl substitution at the aromatic ring results in a positive quadrupole moment. However, depending on the polarizability of the anion and on the substitution at the arene, three different modes of interaction, namely Meisenheimer complex, side-on hydrogen bonding, or anion-π interaction, can occur. Experimentally, the side-on as well as a η(2) -type π-complex are observed in the crystal, whereas in solution only side-on binding is found.
Preparation and nonlinear optics of monodisperse oligo(1,4-phenyleneethynylene)s
2001
Oligo(1,4-phenyleneethynylene)s 1a−e, with solubilizing propoxy side chains, were prepared by use of Hagihara−Sonogashira coupling reactions. The synthetic strategy was based on a building block system and on the use of trimethylsilyl and triisopropylsilyl protecting groups that could be cleaved selectively. The extension of the conjugation with an increasing number of repeat units provokes a bathochromic shift of the long wavelength absorption and a superlinear increase of the second hyperpolarizability |γ|. The corresponding third harmonic generation (THG) measurements were performed using polystyrene matrices and variable laser wavelengths. We conclude that the conjugation length is much…
Electronic structure and properties of MAu and MOH, where M = Tl and Nh: New data
2018
Abstract Properties of the MAu and MOH (M = Tl and element 113, Nh) molecules were calculated using the 2c-DFT method. The obtained data are needed for evaluation of reactivity of Nh studied by gas-phase chromatography experiments. Results show that Nh should be less reactive (or more volatile) than Tl, both with respect to gold and the hydroxyl group. The reason for that are strong relativistic effects on the valence 7s and 7p electron shells. In difference to the atoms, NhOH may be less volatile than TlOH due to its larger both dipole moment and anisotropic polarizability.
Low-Frequency Relaxation Phenomena in α-LiIO3: The Nature and Role of Defects
2002
The lithium iodate ionic conduction in the polar c-axis direction is studied between 35 and 470 K for crystals grown in various conditions. So far, to separate processes induced by the nature of electrodes, the impedance spectroscopy technique had been used at room temperature with both metallic and ideally polarizable insulating electrodes, so that a relaxation of space charges was clearly identified. Here, the temperature dependence of the hopping ionic conductivity exhibits quite different activation energies well related to the growth conditions. Following low-temperature Raman and thermodynamic experiments, a new approach based on a vacancy diffusion mechanism is proposed. Experimental…
Electronic spectroscopy of I2–Xe complexes in solid Krypton
2012
In the present work, we have studied ion-pair states of matrix-isolated I(2) with vacuum-UV absorption and UV-vis-NIR emission, where the matrix environment is systematically changed by mixing Kr with Xe, from pure Kr to a more polarizable Xe host. Particular emphasis is put on low doping levels of Xe that yield a binary complex I(2)-Xe, as verified by coherent anti-Stokes Raman scattering (CARS) measurements. Associated with interaction of I(2) with Xe we can observe strong new absorption in vacuum-UV, redshifted 2400 cm(-1) from the X → D transition of I(2). Observed redshift can be explained by symmetry breaking of ion-pair states within the I(2)-Xe complex. Systematic Xe doping of Kr ma…