Energy of Charge Distribution in Field

The effect of the induced dipole on the energy of a charge distribution in a uniform electrostatic field can be deduced, and it is (Hinchliffe and Munn, 1985) 

The Cartesian components of the permanent dipole and the polarizabihty can therefore be written equivalently 

Experimental determinations are far from straightforward, especially if the molecule has little or no symmetry. The mean value can be deduced from the refractive index of a gas, whilst Kerr effect experiments give some idea of the anisotropy. 

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