Home »
Mobile Tools Trends »
Which Molecules Are Raman Active?
Which Molecules Are Raman Active?
James H. Sterling••6 min read
Raman spectroscopy occurs as a result of a molecular vibration
molecular vibration
A molecular vibration is a periodic motion of the atoms of a molecule relative to each other, such that the center of mass of the molecule remains unchanged. ... A fundamental vibration is evoked when one such quantum of energy is absorbed by the molecule in its ground state.
causing a "change in polarizability" of the molecule. In contrast, for a molecule to be infrared active, the vibration must cause a change in the permanent dipole moment. A simple case of a Raman Active molecule would be a species such as CS2.
How do you know if a molecule is IR or Raman active?
To be IR active (allowed), the vibration must change the dipole moment of the molecule. To be Raman active (allowed), the vibration must change the polarizability of the molecule.
Is H2 Raman active?
For this reason, homonuclear and thus nonpolar molecules such as H2 or N2 are Raman-active. ... This motion is, however, Raman-active, since the polarisability changes periodically as a result of the stretching vibration.
