Triatomic hydrogen or H is an unstable triatomic molecule containing only hydrogen. Since this molecule contains only three atoms of hydrogen it is the simplest triatomic molecule and it is relatively simple to numerically solve the quantum mechanics description of the particles. Being unstable the molecule breaks up in under a millionth of a second.  Its fleeting lifetime makes it rare, but it is quite commonly formed and destroyed in the universe thanks to the commonness of the trihydrogen cation. The infrared spectrum of H due to vibration and rotation is very similar to that of the ion, . In the early universe this ability to emit infrared light allowed the primordial hydrogen and helium gas to cool down so as to form stars.