Atomic, molecular, and optical physics and chemical physics. Both subfields are primarily concerned with electronic structure and the dynamical processes by which these arrangements change. Generally this work involves using quantum mechanics. For molecular physics, this approach is known as quantum chemistry. One important aspect of molecular physics is that the essential atomic orbital theory in the field of atomic physics expands to the molecular orbital theory. Molecular physics is concerned with atomic processes in molecules, but it is additionally concerned with effects due to the molecular structure. Additionally to the electronic excitation states which are known from atoms, molecules are able to rotate and
Molecules in stars don't allow atoms to form molecules. Stars have very high temperatures, primarily in their interior, and therefore there are few molecules formed in stars. For this reason, a chemist (who studies atoms and molecules) would not have much to study in a star, so stars are better explained by physicists. However, low abundance of molecules in stars is not equated with no molecules at all. Although the Sun is a star, its photosphere has a low enough temperature of 6,000 kelvins, and therefore molecules can form. Water has been found on the Sun, and there is evidence of H in