IONIZATION AND DECAY PROCESSES

Ionization:

• The process of liberating an electron from a gas molecule with a simultaneous production of a positive ion is called ionization.
• The various physical conditions of gases namely pressure, temperature, electrode field configuration, nature of electrode surface sand the availability of initial conducting particles are known to govern the ionization processes.

Collision process

• Collision process is mainly gas processes which occur due to the collision between the charged particles and gas atoms or molecules.

Types of collision

• Elastic collision
• Inelastic collision

Elastic collisions

• They are collisions which when occur, no change takes place in the internal energy of the particles but only their kinetic energy gets redistributed.

Inelastic collisions

They are those in which internal changes in energy takes place within an atom or a molecule at the expense of the total kinetic energy of the colliding particle.

The collision often results in a change in the structure of the atom.

Examples of inelastic collisions

Ionization
Attachment
excitation
Recombination

Diffusion

When particles possessing energy, which is exhibited as a random motion are distributed unevenly throughout a space, then they tend to redistribute themselves uniformly throughout the space.
This process is known as diffusion.

Collision cross-section

It is defined as the area of contact between two particles during a collision. In other words the total area of impact

Theory for breakdown under different conditions

• Townsend theory
• Streamer theory

Townsend’s first ionization coefficient

Townsend’s first ionization coefficient is the average number of ionizing collisions made by an electron per centimeter travel in the direction of the field.

Townsend’s secondary ionization coefficient

The Townsend’s secondary ionization coefficient is defined as the net number of secondary electrons produced per incident positive ion, photon, excited particle or meta stable particle.

Electronegative gas

An electronegative gas is one in which the electrons get attached to form negative ion.

Attachment coefficient

An attachment co-efficient is defined as the number of attaching collusions made by one electron drifting one centimeter in the direction of the field.