Rami Arieli: "The Laser Adventure" Chapter 6, Molecular Gas Lasers, page 1
III. Molecular Gas Lasers

All the lasers described so far are based on electronic transitions between different main energy levels.

In a molecule, the main energy levels are subdivided into vibrational energy levels. Each vibrational energy level can be subdivided into rotational energy levels:

  1. Vibrational energy levels - energy levels associated with the oscillation of the atoms in the molecule.
  2. Rotational energy levels - energy levels associated with the rotation of the molecule.
Since these energy levels are subdivisions of the main energy levels, the difference between the two vibrational energy levels in which lasing occurs, is much smaller than the difference between main electronic energy levels. Thus, the wavelengths associated with the energy transitions among these levels is longer, and is usually in the Infra-Red (IR) spectrum.

Among the molecular lasers, the most common laser is the Carbon-Dioxide (CO2) laser. Some of its applications are described in chapter 9.