Atomic emission is a process occurring when electromagnetic rays is emitted by excited atoms or ions. In atomic emission spectrometry the test is put through temperature ranges high enough to cause not only dissociation into atoms, but also to cause significant amounts of collisional excitation and ionisation of the test atoms to take place. Once the atoms and ions are in the ecstatic expresses, they can decay to lessen state governments through thermal or radiative (emission) energy transitions and electromagnetic radiation is emitted. An emission spectrum of an element includes several more lines than the matching absorption spectrum. FES (previously called fire photometry) is at principle just like emission spectroscopy, with flame as the source of excitation energy (fire atomiser).