ABSTRACT
This chapter is concerned primarily with the laser emission spectra from a host of molecules and reviews some of the features that can be predicted by simple quantum mechanical models. It provides a list of over 2000 laser lines, selected from some of the well-known molecular lasers by grouping them into three types: electrical discharge lasers, chemical lasers and optically pumped lasers. The treatise is elementary and deals with simple molecular systems, in which the nuclei are assumed to be in their equilibrium positions relative to the motion of the associated electrons. The energy-level expression, derived for diatomic molecules, usually applies also to polyatomic molecules. The selection rules for infrared rotational transitions of linear polyatomic molecules can be obtained exactly the same way as that for diatomic molecules if the molecule has a permanent dipole moment. A spherical top molecule has at least two or more planes that interact the ellipsoid of moment inertia in a circle.
