Background dielectric constant

The background dielectric constant e for the metal arises from the polarizability of the ion cores and the contribution of interband transitions.11 For mercury and other simple metals, with a large band gap and relatively unpolarizable ion cores, one expects a background dielectric constant close to unity. With e = 1 and n°° = 8.17 x 1022 cm-3 (mercury), the capacitance per unit area is... 

The optical properties of organic conductors may be described by the simplest model, which assumes noninteracting electrons (one-electron model). In this approximation the infrared (IR) properties may be derived in the self-consistent field approximation. Assuming a frequency-independent relaxation rate, y, and a background dielectric constant arising from virtual high-frequency transitions, e0, the result takes the Drude form [12] ... 

Measurements of the polarized reflectance in the NIR have frequently been used to obtain estimates for the transfer integrals. The method consists in fitting a reflectance model based on the Drude expression [Eq. (1)] to the experimental data. The Drude expression should be considered as a tool in estimating the plasmon frequency, ftp the background dielectric constants, e0 plasma frequency, (op and so on. The validity of the Drude analysis is limited to the conducting organic materials, with the electrical conductivity not less than a few S cm-1. 

In Table III are listed the calculated stopping bandwidths and the bandwidths (FWHM) of the actual reflection spectra for the FDA urethane sidechain series of crystals studied here. Because the value of the background dielectric constant is... 

Holes. Compared to the situation for photoelectrons in the silver halides, the properties of holes are less well understood. In the effective mass approximation, the binding energy is moderated by the background dielectric constant. When a mobile carrier is close to a trapping center, it does not experience the full dielectric constant of the perfect lattice. If the effective mass is sufficiently large or the dielectric constant sufficiently small, the... 

We might call the quantity e , the background dielectric constant e , with respect to the resonance at the frequency Since e , / 1 the existence of the background dielectric constant alters the oscillator strength of the transition. This is especially significant for the spectral range of low-intensity molecular transitions (see Ch. 3). 

TABLE 1 Dehydration Free Energies (in kJ mol ) for Ions of Various Size and Polarity as Functions of Water s Hard-Core Radius, R, and Background Dielectric Constant,... 

Table 9.4 Materials parameters obtained from the optical reflection spectra of the (Fa)2PFg crystal (28). cop is the unshielded plasma frequency, r the mean scattering time, Coo the background dielectric constant, oq the optical conductivity for oi— O, m pf the effective mass of the charge carriers, vp the Fermi velocity, and Ep the Fermi energy.

Extending these studies to ion-dipole mixtures in which a background dielectric constant is replaced by fluctuating solvent point dipoles, leads to practical nonergodic-ity due to the formation of clusters and/or strings of particles [164]. 

Screened Plasma Frequency the plasma frequency normalized or screened by a background dielectric constant. The screened plasma frequency, Wp = fl /where /2p is the plasma frequency and is the background dielectric constant due to all excitations except the conduction electrons. 

Within this description different ionic species are distinguished by their valence number alone. Another reduction comes from the treatment of a solvent as a background dielectric constant e. Within this level of description a polarization density of a polar solvent responds linearly to an electrostatic field, P = yE, where E = -V vr is the local electrostatic field. The total dielectric constant becomes e = (, + y, where is the dielectric constant of vacuum, and the action of a solvent is to reduce the strength of electrostatic interactions. 

The dipolar PB equation was derived in Ref 7, using the field theory formaUsm, and was further explored in Ref 22. The motivation was to arrive at a more accurate representation of a water solvent, beyond a mere background dielectric constant, the way it is done within the standard PB modef The standard PB equation assumes... 

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