Spectroscopy is the use of the absorption, emission, or scattering of electromagnetic radiation by atoms or molecules (or atomic or molecular ions) to qualitatively or quantitatively study the atoms or molecules, or to study physical processes. The interaction of radiation with matter can cause redirection of the radiation and/or transitions between the energy levels of the atoms or molecules. Molecular symmetry can be seen as the most basic and important concept in physics. On a given physical system, the eigenstate properties and the degeneracy of eigenvalues are governed by symmetry...