There are lasers in which the required conditions for lasing are achieved in exotic ways.

As an example, we shall examine a family of lasers in which the radiation is emitted from a molecule which only exists for a very short time.
This molecule is composed of an atom of noble gas: Argon, Krypton or Xenon, and an atom of halogen: Fluorine, Chlorine, Bromine or Iodine.

An Excimer is a molecule which has a bound state (existence) only in an excited state.

In the ground state this molecule does not exist, and the atoms are separated.

The excited state exists for a very short time, less than 10 nanoseconds.

The name Excimer comes from the combination of the two words: exited dimer, which means that the molecule is composed of two atoms, and exists only in an excited state.

(Some scientists consider this molecule to be a complex, and they call the laser "Exiplex").