Physics
Ionized Gas
Ionized gas refers to a state of matter in which gas particles have lost or gained electrons, resulting in the formation of positively or negatively charged ions. This process occurs at high temperatures or through exposure to strong electromagnetic fields. Ionized gases are important in various fields, including astrophysics, plasma physics, and industrial applications such as plasma cutting and welding.
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eBook - ePubFundamentals of Ionized Gases
Basic Topics in Plasma Physics
- Boris M. Smirnov(Author)
- 2012(Publication Date)
- Wiley-VCH(Publisher)
Chapter 1 General Concepts in Physics of Excited and Ionized Gases 1.1 Ideal Plasma 1.1.1 Plasma as a State of MatterThe word “plasma” was introduced into science by the Czech physiologist J.E. Purkinje in the middle of the nineteenth century to denote the uniform blood fluid that is released from particles and corpuscles. This term was suggested for a uniform Ionized Gas of the positive column of a gas discharge by Langmuir [1–3] and now this term denotes any system with electrons and ions where charged particles determine the properties of this system. The most widespread form of plasma is an Ionized Gas which consists of atoms or molecules with an admixture of charged particles, electrons and ions. Such a plasma is the subject of this book.To understand the conditions required for the existence of such a plasma under equilibrium conditions, we compare it with an identical chemical system. Let us consider, for example, atmospheric air consisting basically of nitrogen and oxygen molecules. At high temperatures, along with the nitrogen and oxygen, nitrogen oxides can be formed. The following chemical equilibrium is maintained in air:(1.1)Here and below, the sign ↔ means that the process can proceed either in the forward direction or in the reverse direction. According to the Le Chatelier principle [4, 5], an increase in the temperature of the air leads to an increase in the concentration of the NO molecules.A similar situation exists in the case of formation of charged particles in a gas, but this process requires a higher temperature. For example, the ionization equilibrium for nitrogen molecules has the form(1.2)Thus, the chemical and ionization equilibria are analogous, but ionization of atoms or molecules proceeds at higher temperatures than chemical transformations. To illustrate this, Table 1.1
eBook - PDF- Boris M. Smirnov, Howard Reiss(Authors)
- 2008(Publication Date)
- Wiley-VCH(Publisher)
The pressure of the gas is 1 atm. Thus, a weakly Ionized Gas, which we shall call a plasma, has an analogy with a chemically active gas. Therefore, though a plasma has charac- teristic properties which we shall describe, it is not really a new form or state of matter as is often asserted. In most actual cases a plasma is a weakly Ionized Gas with a small degree of ionization. Table 1.2 gives some examples of real plasmas and their parameters-the number densities of electrons ( N , ) and of atoms (Na), the temperature (or the average energy) of electrons (Tc), and the gas tempera- ture (TI. In addition, some types of plasma systems are given in Figs. 1.1 and 1.2. It is seen that generation of an equilibrium plasma requires strong heating of a gas. One can create a conducting gas by heating the charged particles only. This takes place in gaseous discharges when an Ionized Gas is placed in an external electric field. Moving in this field, electrons acquire energy from the field and transfer it to the gas. As a result, the mean electron energy may exceed the thermal energy of neutral particles of the gas, and the electrons can produce the ionization which is necessary for maintaining an electric current in the system. Thus, a gaseous discharge is an example of a plasma which is maintained by an external electric field. If the temperatures of electrons and neutral particles are identical, the plasma is called an equi- librium plasma; in the opposite case we have a nonequilibrium plasma. Figure 1.3 gives some examples of equilibrium and nonequilibrium plasmas. TABLE 1.2. Parameters of Some Plasmas' Type of Plasma N,, ~ r n -~ N , T,, K T , K Sun's photosphere 1013 1017 6000 6000 E-layer of ionosphere 105 10 13 250 250 He-Ne laser 3 x 10 2 x 1016 3 x 104 400 Argon laser 1013 10'4 10s 103 aNe,N are the number densities of electrons and neutral atomic particles respectively, and T,, T are their temperatures.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- College Publishing House(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 4 High-Energy States of Matter 1. Plasma (physics) Plasma lamp, illustrating some of the more complex phenomena of a plasma, including filamentation . The colors are a result of relaxation of electrons in excited states to lower energy states after they have recombined with ions. These processes emit light in a spectrum characteristic of the gas being excited. In physics and chemistry, plasma is a substance similar to gas in which a certain portion of the particles are ionized. The basic premise is that heating a gas dissociates its molecular bonds, rendering it into its constituent atoms. Further heating leads to ________________________ WORLD TECHNOLOGIES ________________________ ionization (a loss of electrons), turning it into a plasma: containing charged particles, positive ions and negative electrons. The presence of a non-negligible number of charge carriers makes the plasma electrically conductive so that it responds strongly to electromagnetic fields. Plasma, therefore, has properties quite unlike those of solids, liquids, or gases and is considered to be a distinct state of matter. Like gas, plasma does not have a definite shape or a definite volume unless enclosed in a container; unlike gas, under the influence of a magnetic field, it may form structures such as filaments, beams and double layers. Some common plasmas are stars and neon signs. Plasma was first identified in a Crookes tube, and so described by Sir William Crookes in 1879 (he called it radiant matter). The nature of the Crookes tube cathode ray matter was subsequently identified by British physicist Sir J.J. Thomson in 1897, and dubbed plasma by Irving Langmuir in 1928, perhaps because it reminded him of a blood plasma.
No longer available |Learn moreGas Physics
Concepts, Models and Applications
- (Author)
- 2014(Publication Date)
- Learning Press(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 1 Introduction to Gas Gas phase particles (atoms, molecules, or ions) move around freely in the absence of an applied electric field. Gas is one of the three classical states of matter (the others being liquid and solid). Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point, boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons are so energized that they leave their parent atoms from within the gas. A pure gas may be made up of individual atoms (e.g. a noble gas or atomic gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or compound molecules made from a variety of atoms (e.g. carbon dioxide). A gas mixture would contain a variety of pure gases much like the air. What distinguishes a gas from liquids and solids is the vast separation of the individual gas particles. This separation usually makes a colorless gas invisible to the human observer. The interaction of gas particles in the presence of electric and gravitational fields are considered negligible as indicated by the constant velocity vectors in the image. The gaseous state of matter is found between the liquid and plasma states, the latter of which provides the upper temperature boundary for gases. Bounding the lower end of the temperature scale lie degenerative quantum gases which are gaining increased attention these days. High-density atomic gases super cooled to incredibly low temperatures are classified by their statistical behavior as either a Bose gas or a Fermi gas. ________________________ WORLD TECHNOLOGIES ________________________ Etymology The word gas is a neologism first used by the early 17th century Flemish chemist J.B.
- G. J. Tallents(Author)
- 2018(Publication Date)
- Cambridge University Press(Publisher)
1 Plasma and Atomic Physics A plasma is created by adding energy to a gas so that electrons are removed from atoms, producing free electrons and ions. Electric and magnetic fields interact strongly with the charged electrons and ions in plasmas (unlike solids, liquids and gases) and, consequently, plasmas behave differently to imposed electric and mag- netic fields and modify electromagnetic waves in different ways to solids, liquids and gases. The different behaviour of plasmas has caused them to be regarded as a fourth fundamental state of matter in addition to solids, liquids and gases. More than 99% of the observable universe is plasma. For example, the Sun is a plasma and has mass comprising 99.85% of the solar system, so the frac- tion of plasma in the solar system is slightly higher once interplanetary plasma is included. Present understanding of the universe has been enabled by the detection of electromagnetic radiation emitted by or passing through plasma material. To understand the universe, we need to understand plasmas, and, in particular, we need to understand the processes of light emission and propagation in plasmas. 1 Plasmas have many realised and potential applications. The fusion of isotopes of hydrogen in plasmas confined using magnetic fields or confined by inertia before a dense plasma can expand should provide a new source of energy production to replace the burning of fossil fuels, though the exact physics and many technical issues are not yet resolved [35]. The fuel for a fusion reactor (the deuterium isotope of hydrogen) is abundant in seawater (at concentration 33 mg/litre). Large-scale experiments are under way to make fusion reactors because of the enormous poten- tial impact of the development of a fusion power plant [79, 67]. Plasmas are used in many technological applications, including semiconduc- tor etching and thin-film coating [15].
eBook - PDF- Jörg Florian Friedrich, Jürgen Meichsner(Authors)
- 2022(Publication Date)
- Wiley-Scrivener(Publisher)
17 Jörg Florian Friedrich and Jürgen Meichsner. Nonthermal Plasmas for Materials Processing, (17–118) © 2022 Scrivener Publishing LLC 2 Basic Principles of the Plasma State of Matter 2.1 Characteristics and Physical Properties of Plasmas 2.1.1 Ionization Degree, Energy Content and Classification The physical plasma represents a many particle system, consisting of a sufficiently high con- centration of free positive (q + ) and negative (q - ) charged species, e.g., positive ions, negative ions and electrons, with net charge zero (quasi-neutrality). This system may additionally contain neutral atoms, molecules, radicals and excited species. The ionisation degree χ gives information about the content of charged particles in rela- tion to the total species concentration. In the simplest case, considering the plasma of single charged positive ions, electrons and neutrals, the ionization degree χ ( . is defined as n n n e e n χ = + (2.1) n e , n n : species concentration of electrons and neutrals. The ionization degree in plasmas observed in nature and the laboratory varies over a wide order of magnitude between 10 -8 and 1. From that point of view two important types of plasmas are distinguished: (i) partially or weakly ionized plasmas with χ << 1, and (ii) completely or strongly ionized plasmas with χ ≤ 1 The considered non-thermal plasmas are exclusively associated with partially or weakly ionized plasmas (n e <
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