Atomic emission spectrum analysis is based on atomic emission spectrum to determine the chemical composition of the material. Different matter consists of different elements atoms, and the atom contains a structure closely nucleus，there are constant motion electrons around the nucleus outside. Each electron at a certain level, have a certain energy. In normal circumstances, the atoms in a stable state, its energy is the lowest, this state is called the ground state. But when atoms receive energy (such as heat, electricity, etc) effect, atoms with high speed movement gas particles and electrons collide with each other then get the energy, make the electrons of the atoms in the outer transition from the ground state to higher level, in this state it is called atomic excited state. The energy for the electron transition from the ground state to the excited state was known as the excitation potential, when additional energy is large enough, the electrons in the atoms are out of the binding force of nucleus, make atomic to be ions, this process is called ionization. The needed energy of atom loses an electron to become ion is referred to as the primary ionization potential. The outer electrons of ions can also been aroused, the energy it needs is the excitation potential of corresponding ion. In the excited state’s atoms is very unstable, in a very short period of time will transition to the ground or other lower level.
When atoms in the process of higher energy level transition to ground state or other lower level , will release the excess energy, this energy radiate out in the form of the electromagnetic wave of a certain wavelength. The each emitted wavelength of the spectrum, depends on the difference between the two energy levels transition.