“…1,2 The discovery of ammonia in the 25 interstellar medium dates back to 1968, 3 when emissions were observed at a frequency corresponding to the inversion transitions of the rotational levels j k = 1 1 and 2 2 in the vibrational ground state of NH 3 . Since then, ammonia has been observed in various environments, such as comets, 4 the Galactic centre, 5 the T dwarf 30 class of brown dwarf stars, 6 and in diffuse and translucent molecular clouds. 7 Ammonia is also present in the Earth's troposphere, 8 and has been identified in the atmospheres of extrasolar planets.…”