Selection rules for IR and Raman

 

 

 

What is the basic requirement that a vibration is either Raman - or IR - active?

 

Ifda/dQ for Q = 0 <> horizontal --> Raman - active

 

If dµ/dQ for Q = 0 <> horizontal --> IR - active

 

Please note:

 

By coupling with other vibration modes an inactive vibration may become active

if higher orders are <> 0 !