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

X-RAYS

are all forms of ionizing radiation

FRACTION

only a____ of the particle’s energy can be transferred to an electron in an atom or molecule

100

A minimum of ___ eV is necessary to knock these electrons

PARTICLE

ENERGY

As a _____ travels through matter, ____ is transferred from it until it has about the same energy as the surrounding matter.

SLOW DOWN

As particle transfers its energy, it ______.

KINETIC ENERGY

As particle transfers its energy, it slow down. Its energy is _____

KINETIC ENERGY

VELOCITY

MASS

As the ________ decreases, _____ must also decrease, since ____ remains constant

COLLISIONS

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

ELASTIC COLLISIONS

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

SAME

The total kinetic energy of the particle and the electron it hits remains the

INELASTIC COLLISIONS

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

CHARGED PARTICLE

ELECTRON

This is common between large _____ (proton, alpha particle) and ______

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

IONIZATION

It results in the formation of a cation and a free electron (ion pair)

PRIMARY IONIZATION

The creation of an ion pair by ionizing radiation is called _____.

SECONDARY IONIZATION

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

SECONDARY ELECTRON

DELTA RAYS

The freed electron is often called __________- or collectively known as ________-

EXCITATION

IONIZATIONS

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

ELECTRON EXCITATIONS

are roughly two times more common than ionizations in air

NUMBER OF ION PAIRS PER UNIT LENGTH

• As charged particles travels through matter, it creates ___________

SPECIFIC IONIZATION

known as ________ which is dependent on (a) energy of charged particle and density of matter it is traveling through

3 TO 7 MILLION

The specific ionization of alpha particles traveling through air varies from _________ ion pairs per meter (IP/m)

LINEAR ENERGY TRANSFER (LET)

Amount of energy deposited per unit path length is called the

LET

KINETIC ENERGY

___ of a charged particle is proportional to the square of the charge and inversely proportional to its ___________-

ALPHA PARTICLES

PROTONS

High LET radiations

ELECTRONS

GAMMA RAYS

X-RAYS

low LET radiations

HIGH LET RADIATIONS

LOW LET RADIATIONS

__________ are more damaging to tissue than __________

SPECIFIC IONIZATION

W-QUANTITY

LET is dependent on the ________ and

RANGE (R)

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

ALPHA PARTICLE

HEAVY CHARGED PARTICLES

For ______ and other ______, range can be calculated by dividing the energy of alpha particle (E) by its average linear energy transfer (LET)

IT LOSES ENERGY

as particle moves through matter

INCREASING

ION PAIRS

as it loses energy, it transfers _______ amount of energy and creates more _______ er centimeter traveled

BRAGG PEAK

It plots the energy loss of ionizing radiation during its travel through matter.

BRAGG PEAK

This represents the fact that charged particles deposit much of their energy after penetrating matter some distance

INCREASES

DECELERATE

The probability of interaction ______ as the particle continues to ______

WILLIAM HENRY BRAG

1903

Bragg peak was named after ________ and discovered in _____

CHARGED PARTICLE TRACKS

Electrons follow tortuous paths in matter as the result of multiple scattering events

SPARS

Ionization track is

LINEAR IONIZATION TRACK

Charged particle results in dense and usually _______.

PATH

is actual distance particle travels.

RANGE

is actual depth of penetration in matter

ALPHA PARTICLE INTERACTION

Their high kinetic energy, positive charge and large mass compared to an electron, allows them to cause a great many ionizations in a very short travel distance.

ATOMS

SHORT RANGE

Because alpha particles are charged and relatively heavy, they interact intensely with _____ in materials they encounter, giving up their energy over a very ______.

AIR

In ____, their travel distances are limited to no more than a few centimeters

SINGLE SHEET OF PAPER

Alpha particles are easily shielded against and can be stopped by a __________.

BETA PARTICLE

is much less massive and less charged than alpha particles and interact less intensely with atoms in the materials they pass through

BETA PARTICLE INTERACTION

Has a longer range than alpha particles

ENERGETIC BETA PARTICLES

will travel up to several meters in air or tens of mm into the skin

METAL, PLASTIC

Thin layers of ______ or _____ stop beta particles

LOW ENERGY BETA PARTICLES

are not capable of penetrating the dead layer of the skin

BETA EMITTERS

All _______, depending on the amount present, can pose a hazard if inhaled, ingested or absorbed into the body.

ENERGETIC BETA EMITTERS

are capable of presenting an external radiation hazard, especially to the skin.

POSITRON INTERACTION

The interaction between a positron and matter is in two phases, (a) ionization and (b) annihilation

IONIZATION

ANNIHILATION

2 phases of interaction between a positron and matter.

ELECTRICAL ATTRACTION

As the energetic positron passes through matter, it interacts with the atomic electrons by ______

IONIZATION

As the positron moves along, it pulls electrons out of the atoms and produces ________-.

ANNIHILATION PROCESS

occurs when the antimatter positron combines with the conventional-matter electron.

POSITRON INTERACTION

In this interaction, the masses of both particles are completely converted into energy

511 keV

The energy equivalent of one electron or positron mass is

PHOTONS

511 keV

The energy that results from the annihilation process is emitted from the interaction site in the form of _____, each with an energy of _____.

OPPOSITE DIRECTIONS

The pair of photons leave the site in _____.

NEUTRONS

are uncharged particles

NEUTRON INTERACTIONS

They do not interact with electrons

NEUTRON INTERACTIONS

Do not directly cause excitation or ionization

BILLIARD BALL

EXCITATION, IONIZATION

They do interact with atomic nuclei of light elements, sometimes liberating charged particles or nuclear fragments in a '“____” like collision, that can directly cause _____ or ______.

ATOMIC NUCLEI

Neutrons may also be captured by

NEUTRON INTERACTIONS

Retention of the neutron converts the atom to a different nuclide (stable or radioactive)

ELECTRON

Carries a negative charge

CATHODE RAYS

NEGATIVELY CHARGE

J.J. Thompson (Nobel Prize 1906) discovered that ________ are _______.

J.J THOMPSON

he discovered that cathode rays are negatively charge.

CORPUSCLES

HYDROGEN ATOM

Thompson termed it as “_________” and found out that it is 1,000 times smaller than a _____.

1/1836

PROTON

The mass of electron is approximately _______ of that of a _____.

ELASTIC AND INELASTIC INTERACTIONS

The electron-Matter Interactions are classified into two:

ELECTRON-MATTER INTERACTIONS

When an electron hits a material, different interactions can occur

ELASTIC INTERACTION

No energy is transferred from the electron to the sample; there is no loss of energy.

ELASTIC SCATTERING

BACKSCATTERED ELECTRON

An incoming electron rebounds back out as a ____________

INCIDENT ELECTRON

undergoes this interaction only when its energy is very small

ELASTIC SCATTERING

happens if the electron is deflected from its path by Coulomb interaction with the positive potential inside the electron cloud

ELASTIC INTERACTION

In ________ the primary electron loses no energy or negligible amount of energy

INELASTIC SCATTERING

is a general term which refers to any process that causes the primary electron to lose a detectable amount of energy

INELASTIC INTERACTION

The processes all involve an interaction between the primary beam electrons and orbital electrons of the atom in the sample or material

INELASTIC INTERACTION

There is always energy loss; The energy loss causes ionization

CHARACTERISTIC X-RAYS/AUGER EFFECT

1

The energy loss appears in the form of ________ or _______when energy is little less than __ MeV

CONTINUOUS X-RAYS

Increase in velocity -MeV (near speed of light) causes electron to interact with the nucleus leading to

HEAT

The inelastic interaction most of the exchanged energy lost as ______

ENERGY

is transferred from incident electron to the atom

SECONDARY ELECTRON

X-RAYS

AUGER ELECTRONS

Energy is transferred from incident electron to the atom and it produces:

INNER-SHELL IONIZATION

Incident electron travelling through the atom might transfer part of its energy to an electron located in the atom’s inner most shell

INNER-SHELL IONIZATION

In this situation, this electron is promoted to the lowest unoccupied electron level

IONIZED

If the transferred energy is sufficient, the atom is ______

ENERGETICALLY UNSTABLE

The energy transfer to an inner shell is important because the electronic state of the generated ion is ______

LOW ENERGY

An inner shell with ______ has an electron vacancy whereas the levels of higher energy are occupied

DROPS DOWN FROM HIGHER

To achieve favorable ground state again, an electron __________ energy level to fill the vacancy

CHARACTERISTIC X-RAY

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

CHARACTERISTIC X-RAY & AUGER ELECTRON

The process for getting rid of additional energy is the generation of either ________ or of an _______

INNER-SHELL IONIZATION

This process allows the atom to relax and give away the excess of energy

CHARACTERISTIC X-RAY

The difference energy is emitted as high energetic electromagnetic radiation in the form of

ELEMENT

Every ______ has a characteristic number of electrons localized in a well-defined energy states

MORE

MORE

The ______ electrons and thus energy levels an element has, the ____ transitions are possible