What are the basic particles contained in the plasma of the plasma equipment:
As we all know, the plasma generated by plasma equipment is in a weak ionization state, so in the process of low-temperature plasma discharge, six kinds of elementary particles are usually produced: photons, electrons, ground state atoms (or molecules), excited atoms (or molecules), positive Ions and negative ions.
In plasma equipment, photons and electrons have no internal structure, and the energy of photons depends on their frequency v. In a plasma device, the energy of free electrons depends on its moving speed v. From the analysis of the internal structure of atoms, according to the principles of quantum mechanics, free electrons can be in many different energy states, which can be arranged according to the magnitude of energy. Energy level diagram.

The energy level diagram of the atom in the plasma equipment is determined by all the particles inside the atom. Atoms and molecules that are not disturbed are generally at a stable ground state energy level, but what we are interested in is only the electrons in the outer layer of the atom, that is, the energy of the valence electrons. , Because the gas discharge process is mainly participated by these electrons. When the valence electron gets extra energy from the outer layer, it jumps to a higher energy level where the atom is in an excited state. An electron stays at the excitation level (about 10-8s) for a short time, then transitions back to the ground state or another lower excitation level, and radiates excitation energy in the form of photons to obtain additional energy.
There are also some energy levels (metastable states) that exist for a long time. If the atoms in these excited states do not collide with other particles or the cavity wall, it is impossible to return to the lower energy level in the form of radiated photons, which is called Excited state. In the metastable state, the lifetime of an atom can be 10ms to several seconds or even days. If the energy gained by the electron exceeds the ionization energy, it will be completely separated from the atom and become a free electron, and then the atom will become a positive ion.
Molecules in plasma equipment are generally composed of several atoms. Due to the interaction of these atoms, molecular energy levels are more complex than atomic energy levels, and the excitation and ionization of gas molecules is also different from the excitation and ionization of gas atoms. In addition to electronic energy, the internal energy of molecules also includes vibrational energy and rotational energy. These energies are also separated, and the energy level diagram is very complicated.
The energy state of positive ions in plasma cleaning and plasma equipment can also be represented by energy level diagrams. The ionization energy of the primary ionization atoms of positive ions corresponds to the energy required to produce secondary ionization; negative ions are attached by electrons It is formed on certain atoms or molecules, especially those whose outer electron shell is almost full. The energy of negative ions is equal to the ground state energy of atoms or molecules plus the affinity energy of electrons.
The neutral particles generated during gas discharge in the plasma equipment are atoms or molecules. Atoms may be noble gas atoms or metal vapor atoms; molecules may be single-atom or polyatomic complex molecules. The air pressure ranges from a few tenths of a pascal to hundreds of thousands of Pascals, and the variation range of the corresponding particle density reaches 108 orders of magnitude.
In general, the particles discharged by the gas in the plasma equipment are electrons and various ions, and the electron density is generally between 10^16~10^20/m3. Positive and negative ions are generated by gas discharge, which are different from neutral particles. For example, a large number of ions generated by atmospheric plasma discharge, such as N+, N, O+, O2, NO-, NO2, O2 and O3, etc... Each ion affects the electrical characteristics of the gas discharge