https://doi.org/10.1351/goldbook.M03991
A @[email protected] which makes use of electronic, vibrational or rotational energy levels in molecules. The molecules can be excited by an electric discharge, as in the case of the N2 or CO2 @[email protected], by chemical reactions, as in the HF or DF lasers, or by another @[email protected], as in the CH3F far IR @[email protected]