The concentration of negative ions in the air is closely related to the ionization and excitation of air molecules. Ionization is the process of forming positively or negatively charged particles in the atmosphere. The so-called excitation is the process that an atom absorbs a certain amount of energy from the outside and makes its valence electrons jump to a higher energy level. Electrons get some kinetic energy from the outside and collide with air atoms, which is an important condition for the excitation and ionization of air atoms. There are two kinds of negative oxygen ions in the air: natural and artificial.

I. Ways of generating negative oxygen ions under natural conditions:

(1) Negative ions are generated from natural phenomena.

The atmosphere is ionized by ultraviolet rays, cosmic rays, radioactive substances, thunderstorms, storms, soil and air radiation, releasing electrons. Electrons are absorbed by the earth and released, and quickly combine with neutral molecules in the air to become negative ions, or anions.

The negative ions in nature (that is, negative ions that play a good role in the body and are reduced) have great antioxidant and reducing power. The reason why the air will be particularly fresh after rain is that lightning will ionize the air, thus producing a large number of ecological negative oxygen ions.

(2) Negative ions are generated in high-speed flow.

In natural processes such as waterfall impact, small waves pushing and heavy rain falling. Water flows at a high speed under the action of gravity, causing water droplets to break, water molecules to break and lose electrons to become positive ions, and oxygen molecules in the surrounding air capture these electrons to become negative ions with smaller particle size.

This is also the reason why the concentration of negative oxygen ions around waterfalls, coasts and fountains is particularly high.

(3) Plant growth produces negative ions.

The "tip discharge" effect of coniferous plants will ionize the surrounding air and produce a large number of negative oxygen ions.

Trees in the forest can also ionize the air and produce negative ions.

In addition, terpenes and aromatic substances secreted by some trees and flowers can promote air ionization to produce rich negative oxygen ions.

(d) Negative ions are generated in crustal rocks.

Some crustal rocks can release some negative ions. For example, a natural fiber gypsum mine with well-developed crystals can be made into a pure natural air purifier-crystal gypsum lamp by hand.

2. Method of artificially generating negative oxygen ions

(1) ultraviolet irradiation method

The ultraviolet rays generated by the mercury lamp can ionize the air, and its electrons are generated on nearby metal or dust particles through photoelectric effect, and negative ions are generated through attachment. This ultraviolet light also produces ozone.

(2) thermionic emission method

Some materials, such as metals, will emit electrons when heated to a certain temperature, and the quantity of emitted electrons is determined by thermionic emission characteristics and temperature. These emitted electrons generate ions by attaching to oxygen and small dust particles. Most of the negative ions produced by this method are large charged ions, and only a small part are small ions that can activate human physiology.

(3) Radioactive material radiation method

Radioactive substances can be used to generate negative air ions. Among them, the radioisotope emitting alpha particles is the most effective ion generator, such as an alpha particle of polonium 2 10, which can generate about 150000 ion pairs and can exclude electrons of nitrogen and oxygen. Among the ions obtained, negative oxygen ions are absolutely dominant.

(4) Corona discharge method

It means that a high potential difference is applied between two electrodes, one of which is a needle with a small diameter, and the high electric field around the needle electrode will produce a large number of positive ions and negative ions. If the needle electrode is negative, positive ions will be absorbed quickly, and negative ions will be repelled to the opposite electrode, resulting in air negative ions of corona discharge. At present, most of the popular negative ion generators on the market use corona method to generate negative ions. The electrodes are bipolar. Usually, the negative electrode is needle-tip shaped and the positive electrode is round. On the basis of early research, this technology has few innovations, low negative ion concentration, poor expansion performance and high ozone concentration.

(5) hydropower separation method

Using the jet action of high-pressure water, a tiny stream of water is injected into the air from the nozzle, and air negative ions are formed when it splits. China has successfully developed a powerful negative ion fountain. With the high-pressure water jet injection device, more than 100 trillion negative ions can be ejected from a nozzle with a diameter of 2mm, forming a negative climate environment on tens of thousands of square meters of ground. This kind of equipment is usually installed in city squares, parks, hotels, sanatoriums, fountains of pavilions, and pools of modern music fountains, forming negative ion convalescence areas, which are not suitable for family use.