9. Interaction of Electron with Matter Flashcards
is the removal of an electron from an atom
Ionization
occurs when an x-ray passes close to an orbital electron of an atom and transfers sufficient energy to the electron to remove it from the atom.
Ionization
In radiologic technologies, we use the definition of the removal of an electron form an atom because once the projectile electrons hit an atom you cannot expect that the atom will gain additional electron
Ionization
The orbital electron and the atom from which it was separated are called an
Ion pair
The ______ is a negative ion and the remaining atom is a _____ ion
electron,
positive
Outer shell electrons are simply raised to an excited, or higher, energy level then immediately drop back to their normal energy level with the emission of infrared radiation.
Excitation
is the number of ion pairs produced per unit track length
Specific Ionization
An exposure of 1 roentgen produces ______
ion pairs per cm^3
of air at standard temperature and pressure
(STP)
2.08 x 10^9
1 cm^3 of air at STP has a mass of
0.001293 g
is the amount of
exposure that will produce 2.58 x 10^-4 C (of ionization) per kg of air.
The official definition of the Roentgen
is a unit of electrical charge
coulomb
Since ionization produces charged particles (ions), the amount of ionization produced can be expressed in
coulombs
One coulomb of charge is produced by
6.24 x 10^18 ionizations
1 R = __ C/kg
2.58 x 10^-4 C/kg
1 C/kg = ____ R
3876 R
1 roentgen produces ______ per cm^3 of air at standard
2.08 x 10^9 ion pairs
It is a measure of the rate at which energy is transferred from ionizing radiation to soft tissue.
Linear Energy Transfer
It is the amount of energy released by a radioactive particle or wave over the length of its decay track.
Linear Energy Transfer
Linear Energy Transfer expressed in units of _______ of track length in soft tissue
kiloelectron volt per micrometer (keV/μm)
diagnostic x-rays has ___ keV/μm
3
ionizes water into H and OH radicals over a very short track.
High LET radiation (like alpha & beta particles)
LET
Linear Energy Transfer
also ionizes water molecules, but over a much longer track
Low LET radiation (like X- or gamma rays)
electrons travelling from cathode to anode
Projectile Electrons
is just a measure of the total number of electrons that travel from cathode to anode
mAs
mAs =
mC
1 C = _____ electrons
6.25 x 10^18 electrons
Unit of Energy
Kinetic Energy
1 Joule = _____ eV
6.24 x10^18
1 keV = ____ J
1.6 x10^-16
are emitted when an outer-shell electron fills an inner-shell void
Characteristic x-rays
Characteristic of the target material
Characteristic x-rays
Are produced when a projectile electron is slowed by the electric field of a target atom nucleus
Bremsstrahlung Radiation
“Slowed down radiation”
Bremsstrahlung Radiation
Bremsstrahlung Radiation is a ____ word
German
to brake
bremsen
radiation
Strahlung
braking radiation
Bremsstrahlung Radiation
deceleration radiation
Bremsstrahlung Radiation
Define as the pair of positive and negative particles produced during ionization
Ion pair
In a neutral atom, the number of electrons and protons are
equal
Electron binding energy decreases, as the electrons moves ______ from the nucleus
farther away
During electron interaction that produces ionization there’s great chance that the _______ electrons are the one being removed (they have lesser electron binding energy)
outer shell
Used in radiation therapy to burn cancer cells
High Linear Energy Transfer radiation
Radiation Therapy
High LET radiation
Used in general radiography (Diagnostic X-rays)
Low LET radiation
produce free
radicals which are elements in the body that
can produce cancers (carcinogenic)
High LET radiation
radiation breaks down water
Capable of radiolysis
Occur in accidental leakage of power plant
High LET radiation
not capable of radiolysis
Low LET radiation
strike the atom in the
target and ionize to produce x-rays
Projectile electrons
Velocity is speed of light, expressed in
m/s
Kinetic energy is expressed in
Joules
Mass is expressed in
Kg
