Raman active

• Wikipedia:
  Raman spectroscopy


• Raman active vibration modes of a graphene monolayer
  Raman spectrum provides a vibrational fingerprint allowing to distinguish different bonding morphologies.
  Andrea C. Ferrari and Denis M. Basko, 'Raman spectroscopy as a versatile tool for studying the properties of graphene', Nature Nanotechnology 8, 235 (2013).
  
  Schematic of important Raman-active modes of a graphene monolayer (courtesy of Andrea C. Ferrari)