Effect of an Electrostatic Field

Assuming an exact knowledge of the nature of the electronic transition or vibration associated with each absorption band, and assuming that the effect of the electrostatic field of a surface on these transitions can be calculated reliably, it should be possible, in principle at least, to deduce the orientation of the molecule on the surface from observation of the change in extinction coefficient with coverage. Unfortunately, our knowledge and understanding of optical transition and of the effects of an electrostatic field on these transitions is not sufficiently developed to permit such detailed conclusions. 

In Sect. 3.2.4 the internal energy was treated as a sum of the mechanical and heat energies. Here, in addition, we discuss the effect of an electrostatic field (p on the change of internal energy d Ug under the molar description. 

The first complication to be considered is the presence of an electrostatic field during the mass spectrometric study of the reaction. Only few quantitative studies have allowed for the possible contribution of hard collisions to cross-section (25), and the possibility that competitive reactions of the same ion may depend on ion energy is generally neglected in assigning ion-molecule reaction sequences. These effects, however, do not preclude qualitative application of mass spectrometric results to radiation chemistry. 

Evidently, Eq. (39) cannot be valid whenever the tip does not possess an exact hemispherical symmetry for instance, whenever traces of crystallographic planes are visible in the field-ion microscope, the value of the radius of curvature becomes nearer to infinity than to the r of Fig. 5. It is interesting to note also that the theory admits no direct effect of the electrostatic field on the value of ys. In liquids, the effect of E on y gave rise to a whole branch of science usually known as electro-capillarity. An attempt to inaugurate an electrocapillarity of solids is mentioned in Section III.9. 

There is also the possibility of having surface tension affected directly by the presence of an electrostatic field. To some extent this will be a matter of definition since the outward pressure due to a surface charge could be defined as an apparent effect on surface tension. Hurd, Schmid, and Snavely (H15) measured the surface tension of water and water solutions when fields up to 0.7 V/micron were applied across the air-solution interface. The results showed a reduction in surface tension of less than 1 %. These data must not be considered conclusive, however, because insufficient details are reported to permit assessment of the exact nature of the electrostatic field applied or of the validity of a number of corrections that had to be applied but were reported to be very large and difficult to apply. 

In all of the studies of thermodynamic equilibrium that have been presented in the previous chapters, we have neglected the effects of an external field on the equilibrium properties of a system. This has been justified because the field may be present only in specific cases, the effect of the field may be negligible, or the position of the system in the field may be unchanged. The conditions of equilibrium in the presence of a gravitational or centrifugal field, an electrostatic field, and a magnetic field are developed in this chapter. 

The effect of an electrical field on the absorption/emission of spectra of a probe such as fluorescein or a coumarin derivative. It is derived from the interaction of the induced dipole(s) in the probe interacting with the charged group. See Sitkoff, D., Lockhart, D.J., Sharp, K.A., and Honig, B., Calculation of electrostatic effects at the amino terminal of an helix, Biophys. J. 67,2251-2260,1994 Pierce, D.W. and Boxer, S.A., Stark effect spectroscopy of tryptophan, B/opfiyx. J. 68,1583-1591,1995 Klymchenko, A.S., Avilov, S.V., and Demchenko, A.P., Resolution of Cys and Lys labeling of a-crystalUn with site-sensitive fluorescent 3-hydroxyflavone dye. Anal. Biochem. 329, 43-57, 2004. 

The results of a newly proposed model for adsorption at the oxide/water interface are discussed. The modeling approach is similar to other surface complexation schemes, but mass-law equations are corrected for the effect of the electrostatic field. In this respect, this model bridges the gap between those models that emphasize physical interactions. The general applicability of the model is demonstrated with comparisons of calculations and experimental data for adsorption of metal ions, anions, and metal-ligand complexes. Intrinsic ionization and surface complexation constants can be determined with an improved double extrapolation technique. 

Since the intermolecular forces depend on the effect on one molecule of the electrical field produced by another molecule, we begin by looking at the effect of an electrical field on matter in bulk and then at the effect of a field on individual molecules. The basic equations of electrostatics that are required for this are developed in Appendix II... 

In the crystal-field-theory formulation of a metal complex, we consider the ligands as point charges or point dipoles. The crystal-field model is shown in Fig, 9-8. The point charges or point dipoles constitute an electrostatic field, which has the symmetry of the complex. The effect of this electrostatic field on the energies of the metal d orbitals is the subject of our interest, /... 

Recognition of the piezoelectric effect has been known since ancient times [6]. Theophrastus noted in 314 BC the attraction of small pieces of straw and wood to tourmaline after heating, but recognition of the presence of an electrostatic field causing the attraction had to wait for the nineteenth century, along with a name provided by Brewster in 1824 pyroelectricity. All pyroelectric materials are piezoelectric Jacques and Pierre Curie studied piezoelectric materials in the 1880 s and were able to describe many of the characteristics of the phenomena used in applications today. Once synthetic quartz and high-performance... 

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