Molecules play an important role in our world. All biological life and what was described by the ancient Greeks as the four elements, earth, water, air and fire, require knowledge on molecular properties. Therefore it is of vital interest to understand how these can be detected and identified.
Maybe you have studied atomic physics and know how one can extract a vast number of properties of an atomic species and its environment just by studying and interpreting its spectral signature. If you found that interesting, you will find great pleasure in continuing your studies for molecules, and really see how the theories developed and used in atomic physics are extended in molecular physics, making it possible to use spectral signatures for instance for species-specific detection.
Schematic view of the energy levels of a diatomic molecule. Both the molecular vibration and rotation are quantisized. This can be observed for instance in the blue-green light from a candle flame.