RAMAN-SCATTERING IN IMPURE ANHARMONIC DIELECTRIC CRYSTALS

A model impurity induced anharmonic dielectric crystal has been taken to study the fluctuations in the electronic polarizability. Raman scat tering tensor has been developed adopting the method of double time te mperature dependent Green's functions. The effect of mass change, forc e constant change, anharmonicity and impurity and anharmonicity intera ction on Raman tensor has been studied phenomenologically. The impurit y-anharmonicity cross term contribution to the Raman tensor plays a ve ry important role and has not been reported earlier. The inferences on local, gap and resonant modes have been incorporated as concluding re marks.