Charged Particles Interaction with Matter

Ionizing radiation

This refers to radiation with enough energy to knock an electron loose from an atom

Alpha particles, beta particles, gamma rays, and X-rays

forms of ionizing radiation

100 eV

The minimum energy required to knock electrons from an atom.

Collisions

are often used to describe the transfer of energy from particle to atom

decrease

Since mass remains constant, if kinetic energy decreases then velocity must also

Elastic collision

When the kinetic energy of the particle is cleanly transferred as kinetic energy to electron

Elastic Scattering

Occurs when two or more particles (such as electrons) collide without any loss of energy.

Inelastic collision

Include the conversion of the particle’s kinetic energy to some other form (electron moving to a higher energy shell)

Inelastic Scattering

Lose of a detectable amount of energy – meaning energy was transferred making it a significant energy.

Ionization

This takes place if the amount of energy transferred by the particle is greater than the electron’s binding energy, the electron is removed from the atom.

cation and a free electron (ion pair)

Ionization results in the formation of a

Primary Ionization

the creation of an ion pair by ionizing radiation

Secondary Ionization

formed by the freed (ionized) electron causing its own ionization due to its significant amount of kinetic energy

delta rays

The freed electron in secondary ionization is often called secondary electron or collectively known as

Excitation and ionization

the two very common results of the interaction of ionizing radiation with matter

Electron Excitations

Are roughly two times more common than ionizations in air

* Energy of charged particle
* Density of matter it is traveling through

Specific ionization is dependent on

* Number of ion pairs per unit path length (specific ionization)
* Average energy required to produce an ion in any medium

Linear Energy Transfer (LET) is dependent on

Range

It is defined as the average distance a charged particle will travel before being stopped

It will ionize a couple of electrons and form a helium-4 atom

What happens when an alpha particle stops

It will annihilate with an electron

What happens when a positron stops

increases, decreases

As density increases, the relative stopping power _____ and range ___________

Electron

Carries a negative charge and discovered by J.J. Thompson

Elastic Interaction

Interaction wherein the primary electron loses no energy or negligible amount of energy

Inelastic interaction

refers to any process that causes the primary electron to lose a detectable amount of energy

Characteristic x-rays

emitted when an electron from a higher energy level drops to fill the electron hole in a lower energy level

Auger emission

is ejection of an outer electron carrying away the transferred energy of the primary electron as kinetic energy, serving as an alternative to X-ray emission

Auger electrons

have low energies and are easily absorbed by specimen or any gaseous atoms in the vacuum

light elements

the probability of Auger electron emission increases for

Braking radiation

the main constituent of the continuous X-ray emission spectrum

crystal lattice

A phonon is the vibration of a

inner-atomic bonds

A phonon are wave-like stretching and deformation of