Tellurite And Fluorotellurite Glasses For Active And Passive

6. Optical properties; MDO 173
negative charge from the dipole on one end of the molecule, and the negative sign of the
electromagnetic field [2].
A dipole moment, Pind, will be induced in a molecule placed in an electric field, E.
This is due to the attraction of the nuclei to the negative pole of the field, and the
electrons to the positive. Pind is given by equation (6.11) [2].
Pind = πionE (6.11)
where πion is know as the polarisability of the molecule, and is a constant for a given
atom or molecule and typically has units Å 3 (10 -10 m 3 ) [2].
The harmonic oscillator
A simple model for the vibration of a diatomic molecule can be formed by considering
Hooke’s law, which gives the restoring force, F, on a spring (i.e. a bond between two
nuclei). This is illustrated by equation (6.12) and fig. (6.2) [2].
F = −kq
(6.12)