Interaction with matter Flashcards
An x‐ray beam that passes through a medium is likely to undergo
absorption, scatter, or penetration
the process of removing of
electrons from the orbital of an atom
IONIZATION
the process of temporary
removal of electrons from the orbital of an
atom or vibration of the electrons of the atom.
EXCITATION
radiation that during
its passage through an object has been
deviated in direction.
SCATTER RADIATION
radiation produced when an outer shell electron jumps into inner shell
CHARACTERISTIC RADIATION
radiation produced when high speed of
electrons are suddenly stopped or
decelerated.
BREMSSTRAHLUNG RADIATION
positively charged electron.
POSITRON
distance between two
succeeding wave crests
WAVELENGTH
- the incident photon interacts with a
target atom, causing it to become
excited - the incident photon wavelength(λ)
equals the excess energy photon
wavelength(λ’) - changes direction without a change in wavelength
- does not cause ionization, it only
cause excitation - the target atom releases the excess
energy as secondary or scatter
radiation - it causes film fog
- it occurs below 10 keV
CLASSICAL OR COHERENT SCATTERING
TYPES OF COHERENTS SCATTERING:
- THOMPSON SCATTERING
- RAYLEIGH SCATTERING
a single electron is involved in the
interaction.
THOMPSON SCATTERING
results from a cooperative interaction with all the electrons of an atom
RAYLEIGH SCATTERING
- an interaction of x-ray with outer-shell
electron that not only scatters the
photon but reduces its energy and
ionizes the atom as well - produces secondary or scatter
radiation - causes film fog
- occurs in moderate energy x-rays.
COMPTON EFFECT/INCOHERENT
SCATTERING
Compton effect yields three products:
- an ion pair
- a positive atom
- a negative electron(recoil electron)
- undergo ionizing interaction with inner
shell electron of the target atom, so
that the photon is not scattered but
totally absorbed - also called photon-absorption
interaction - can not occur unless the incident
photon has energy equal to or greater
then the electron binding energy of the
atom
PHOTOELECTRIC EFFECT
- it is the strength of attachment of
electron to the nucleus - the closer an electron is to the nucleus,
the more tightly it is bound - the greater the total no. of electrons in
an atom, the more tightly each is
bound - it takes more energy to ionize a large
atom than a small atom
ELECTRON BINDING ENERGY
Photoelectric effect yields three products:
- a characteristic radiation
- a negative ion(photoelectron)
- a positive ion(an atom deficient of
one electron)
- it occurs if an incident photon has
sufficient energy and may escape
interaction with the electron cloud and
come close enough to the nucleus of
the target atom to come under the
influence of the nuclear
force(electrostatic) field - the interaction between the incident
photon and the nuclear force field
causes the photon to disappear and in
its place appear two electrons, one
positively charged called positron and
one negatively charged(negatron) - the incident photon must have an
energy of at least 1.02 MeV
PAIR PRODUCTION
- it occurs with high-energy photons
which escape interaction with
electrons(electron cloud) and the
nuclear electrostatic field and be
absorbed directly by the nucleus - the nucleus is raised to an excited
state and instantaneously emits a
nucleon or other nuclear fragment - it occurs with energy above 10 MeV
PHOTODISINTEGRATION
used in positron emission tomography(PET) for nuclear imaging and therapy
Pair production
because of its extremely high energy is utilized in treating cancer tumors
Photodisintegration
