Raman Scattering: How is it Possible for an IR Inactive Molecule?

[Niles]

Hi

How is it possible for a homogeneous molecule (i.e. one not having a permanent dipole moment and hence not IR active) to be Raman active? What my confusion is that since we cannot excite any states in the molecule (since it is IR inactive), then how can any scattering process even occur?


Niles.

 

[Rap]

Somewhere I remember that Raman scattering is nonlinear. Perhaps it is the quadrupole moment that matters?

 

[basharatwant]

Hi

How is it possible for a homogeneous molecule (i.e. one not having a permanent dipole moment and hence not IR active) to be Raman active? What my confusion is that since we cannot excite any states in the molecule (since it is IR inactive), then how can any scattering process even occur?


Niles.

Well I think it is the polarizability that is important in Raman scattering. If the molecular polarizabilty changes by interaction of the incident e.m.waves with the internal motions of a molecule , the light will be scattered.