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where μ is the electric dipole moment of the effectively polarized water molecule (2.35 D for the SPC/E model), μ 0 is the dipole moment of an isolated water molecule (1.85 D from experiment), and α i is an isotropic polarizability constant, with a value of 1.608 × 10 −40 F·m 2. Since the charges in the model are constant, this ...
An Ion of charge and a nonpolar molecule of polarizability . The Lifshitz theory can be expressed as an effective Hamaker constant in the van der Waals theory. Consider, for example, the interaction between an ion of charge Q {\textstyle Q} , and a nonpolar molecule with polarizability α 2 {\textstyle \alpha _{2}} at distance r {\textstyle r} .
Polarizability increases down on columns of the periodic table. [9] Likewise, larger molecules are generally more polarizable than smaller ones. Water is a very polar molecule, but alkanes and other hydrophobic molecules are more polarizable. Water with its permanent dipole is less likely to change shape due to an external electric field.
London dispersion forces are also known as 'dispersion forces', 'London forces', or 'instantaneous dipole–induced dipole forces'. The strength of London dispersion forces is proportional to the polarizability of the molecule, which in turn depends on the total number of electrons and the area over which they are spread.
Spatial dispersion means that light travelling in different directions (different wavevectors) sees a slightly different permittivity tensor. Natural optical rotation requires a special material, but it also relies on the fact that the wavevector of light is nonzero, and a nonzero wavevector bypasses the symmetry restrictions on the local (zero ...
For the case of infinitesimal wave amplitude, the terminology is linear frequency dispersion. The frequency dispersion characteristics of a Boussinesq-type of equation can be used to determine the range of wave lengths, for which it is a valid approximation. The linear frequency dispersion characteristics for the above set A of equations are: [5]
Dispersion of gravity waves on a fluid surface. Phase and group velocity divided by shallow-water phase velocity √ gh as a function of relative depth h / λ. Blue lines (A): phase velocity; Red lines (B): group velocity; Black dashed line (C): phase and group velocity √ gh valid in shallow water.
However, care is needed because some authors [6] take out the factor from (), so that = and hence () = /, which is convenient because then the (hyper-)polarizability may be accurately called the (nonlinear-)susceptibility per molecule, but at the same time inconvenient because of the inconsistency with the usual linear polarisability definition ...