interactions of xrays with matter (phtoelectric absorption )

Question 1

what is photoelectric absorption

Answer 1

this is an important interaction that takes place in photon energies ranging from 40-80kvp which is the energy commonly used in diagnostic radiography

this process is inelstic meaning that energy is lost and in order for this process to take plae the energy of the incoming photons must be greater than or equal to the binding energy of the orbiting electrons oif the atoms in the medium

Question 2

explain the process of photoelectric absorption

Answer 2

an incoming xray photon which has more energy than the binding energy of the orbiting electron of the medium ejects the orbiting inner shell electron

any energy that the xray photon possessed that is higher than the binding energy is donated to the ejected electron as kinetic energy.

this ejected electron is reffered to as a photoelectron and it is then invoved in other interactions until it has used up all its kinetic energy and is captured by a nearby atom

the rest of the enrgy possessed by the photon that was not donated has been fully absorbed by the medium

however, there is now a vacancy in the atom of the medium which is filled by electrons from further shells jumping down to fill the vacancy and after each jump energy is released as electromagnetic radiation in the infared

this sequence of quantum jumps occurs till all vacancies are filled

Question 3

how is an auger electron formed

Answer 3

after the process of photoelectric absorption,m another interaction may occur usually in materials with high atomic numbers.

after the vacancy in the proximal shell has been filled by an electron from a further shell. the energy lost from that quantum jump may be enough to eject an electron from a shell further away from that one and that ejected electron is called an auger electron

Question 4

factors affecting photoelectric absorption

Answer 4

medium density
medium thickness
atomic number
beam energy