Photon Interactions

Question 0

Coherent scattering (Rayleigh/Thompson)

Answer 0

High atomic # materials and low E beams < 10 MeV
Photon bundle passes orbiting e- and sets it into motion
No e- absorbed by atom, just redirected

Question 1

Photodisintegration

Answer 1

E > 10 MeV have greatest probability
High E photons interact with nucleus
Emission of 1+ nucleons/neutrons

Question 2

Photoelectric effect

Answer 2

Higher E, greater probability
Photon ejects one of the orbiting electrons
Entire energy of photon is absorbed by atom and transferred to e-
Happens in innermost shells
Ejected e- called photo electron
Vacancy: e- drops to fill shell and E emitted is characteristic X-rays/auger e-

Question 3

Compton effect

Answer 3

Effect is independent of atomic # of material
Higher e, lower probability
Happens in outer shells
Photon interacts with an e- as though it was a free e-

Question 4

Pair production

Answer 4

Photon E > 1.02 MeV
Photon interacts with electromagnetic field of nucleus and gives up all E in creating pair of particles (electron and positron)
Probability increases with atomic # (energy increases with mass)