An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

Allowed. → permitted line; → permitted transition.

Past participle of → permit.

An ordinary spectral line emitted by atoms undergoing energy transitions that are allowed by the selection rules of quantum mechanics. → forbidden lines.

→ permitted; → line.

A transition between two quantum mechanical states that does not violate the quantum mechanical selection rules.

→ permitted; → transition.