Posted by Ali on May 30, 2013, 5:47 pm, in reply to "The Optical mode and scattering"
If you drew the dispersion relation for light (omega=ck) on the dispersion relation of the diatomic chain, it's basically a vertical line which will intersect the optical branch at k~0, whereas the energy of the acoustic branch goes to zero for small k.
So by conservation of momentum, light can only excite states in the optical band with small k.
Message Thread
« Back to index