Electric field fluctuation

Nicodemus and Tokmakoff [60] have measured the IR line shape in the OT stretch region of dilute HOT in H20. The peak is at 2121 cm 1, and the width is 127 cm 1. They are particularly interested in the scaling as one goes from OH to OD to OT, in terms of the peak frequencies and line widths, and its implications for the appropriateness of using electric field fluctuations to describe line broadening. 

The electrical field fluctuation is related to that which is due to the source according to the equation... 

Restricting solutions of f(z) = Ae z + Be / z only to those electric-field fluctuations affected by the location of the boundary surfaces, we must have A = 0 for region R and B = 0 for region L. In the absence of any additional charge on the interfaces, the potentials

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Besides the well-confined and rigid framework of zeolites, cation species also plays an important role in manipulating photochemical reaction occurring in the cavity. The free volume in zeolile cavity relies on the number and sort of cations located in the cavity. Differing from isotropic media, in which the direction and magnitude of electric field fluctuate around a solvated molecule, cations in zeoUte cavity generate a stronger, anisotropic and more stable electric field. Such an electric field can polarize the included... 

Besides this, eaeh of the moleeules feels electric field fluctuations coming from motion of the electrons in the partner and adjusts to that motion. This leads to the dispersion interaetion (Chapter 13). 

In the above expression, s" co) is the imaginary part of the dielectric response function and cos"(co) measures the spontaneous electric field fluctuations in a body, as well as a substance s ability to dissipate applied electrical energy (12). 

Intermolecular quadrupolar 2 Fluctuation of the electric field gradient, moving multipoles Common for />1 In free Ions In solution [la... 

This perturbation method is claimed to be more efficient than the fluctuating dipole method, at least for certain water models [Alper and Levy 1989], but it is important to ensure that the polarisation (P) is linear in the electric field strength to avoid problems with dielectric saturation. 

The electric field of a molecule however is not static but fluctuates rapidly Although on average the centers of positive and negative charge of an alkane nearly coincide at any instant they may not and molecule A can be considered to have a temporary dipole moment... 

The electric fields of both A and B fluctuate but always m a way that results m a weak attraction between them... 

Static and alternating (radio frequency) electric potentials are applied to opposite pairs of rods to give a resultant fluctuating electric field. 

The polarlsablllty of a molecule will vary during vibrations which change the Internuclear separations. Thus the vibrations of a molecule sitting In an electrical field will be coupled to the field via the polarlsablllty. This should be particularly noticeable for a molecule adsorbed on an electrode surface where the field strength Is typically In the range 10 -10 V cm, The dipole, perpendicular to the surface, Induced In the molecule by the static electric field will fluctuate In step with the normal mode vibrations of the molecule. 

In the stochastic theory of lineshape developed by Blume [31], the spectral lines are calculated under the influence of a time-dependent Hamiltonian. The method has been successfully applied to a variety of dynamic effects in Mossbauer spectra. We consider here an adaptation due to Blume and Tjon [32, 33] for a Hamiltonian fluctuating between two states with axially symmetric electric field gradients (efg s), the orientation of which is parallel or perpendicular to each other. The present formulation is applicable for states with the same... 

The mobility of ions in melts (ionic liquids) has not been clearly elucidated. A very strong, constant electric field results in the ionic motion being affected primarily by short-range forces between ions. It would seem that the ionic motion is affected most strongly either by fluctuations in the liquid density (on a molecular level) as a result of the thermal motion of ions or directly by the formation of cavities in the liquid. Both of these possibilities would allow ion transport in a melt. 

If a small amount of gramicidin A is dissolved in a BLM (this substance is completely insoluble in water) and the conductivity of the membrane is measured by a sensitive, fast instrument, the dependence depicted in Fig. 6.15 is obtained. The conductivity exhibits step-like fluctuations, with a roughly identical height of individual steps. Each step apparently corresponds to one channel in the BLM, open for only a short time interval (the opening and closing mechanism is not known) and permits transport of many ions across the membrane under the influence of the electric field in the case of the experiment shown in Fig. 6.15 it is about 107 Na+ per second at 0.1 V imposed on the BLM. Analysis of the power spectrum of these... 

The total electric field, E, is composed of the external electric field from the permanent charges E° and the contribution from other induced dipoles. This is the basis of most polarizable force fields currently being developed for biomolecular simulations. In the present chapter an overview of the formalisms most commonly used for MM force fields will be presented. It should be emphasized that this chapter is not meant to provide a broad overview of the field but rather focuses on the formalisms of the induced dipole, classical Drude oscillator and fluctuating charge models and their development in the context of providing a practical polarization model for molecular simulations of biological macromolecules [12-21], While references to works in which the different methods have been developed and applied are included throughout the text, the major discussion of the implementation of these models focuses... 

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