Laporte Selection Rule

Laporte selection rule was given by Otto Laporte. He was a famous German born American physics scientist. He made great contributions in the field of science like in spectroscopy, fluid dynamics, quantum mechanics and electromagnetic wave propagation theory. In Spectroscopy, his name is given to selection rule as Laporte rule.

Definition of Laporte Selection Rule

According to Laporte Rule ” In a  molecule which has a  center of symmetry, the transition between two symmetrical and unsymmetrical states are forbidden.

Laporte Selection Rule
Laporte Selection Rule

Where we can apply Laporte Rule ?

This Laporte Rule is applied only to centrosymmetric molecules (those molecules which have an inversion center) and atoms.

Why g —> g and u —> u electronic transitions are forbidden in Laporte rule ?

According to this rule, If electronic transition do not change parity. Means electronic transition may be either symmetry (g —> g) or anti-symmetry (u —> u) with respect to an inversion center, then electronic transitions are forbidden. So, g —> g and u —> u electronic transitions are forbidden.

When electronic transitions are allowed as per Laporte rule ?

Electronic transitions are allowed only, if electronic transition change parity. Means g —> u and u —> g electronic transitions are allowed.

What is the meaning of g and u in Laporte selection rule ?

g taken from German word ‘gerade’ means even, while u taken from German word ‘ungerade’ means odd.

What is Spectroscopy?

Spectroscopy:-  It deals with the study of interaction of electromagnetic radiations with matter. Spectroscopy is the study of interaction of electromagnetic radiations with chemical species, As a result of these interaction, the energy of electromagnetic radiations get absorbed or emitted by the matter in discrete amounts (photons or quanta) and a spectrum is produced. There are two principal classes of spectrum  i.e. Absorption spectrum and Emission spectrum….. Learn More

You read post, Now I have question for you. Answer in below comment section.

Name any two centrosymmetric molecules ?

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