Oscillation geometry

The sin 0 factor shows that the field produced by the oscillator is maximum in the xy plane, zero along the z axis, and symmetrical with respect to the z axis. This geometry is consistent with the vertical polarization of the field which is driving the dipole and producing the field described by Eq. (10.19). 

In the lowest approximation the molecular vibrations may be described as those of a harmonic oscillator. These can be derived by expanding the energy as a function of the nuclear coordinates in a Taylor series around the equilibrium geometry. For a diatomic molecule this is the intemuclear distance R. 

Torklep and 0ye measured the viscosity of NaCl by this method, which has been adopted as the standard (see Section 1.2). The accuracy of the working equation is better than 0.1% for the cylinder geometry, hquid densities, and liquid viscosities used by these authors. They claim that the remarkable theoretical analysis of oscillating-body viscometers given by Kestin and Newell supersedes all former, less accurate theories. All the results were once suspect owing to possible solid impurities in the liquid. 

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