Compton effect

Probability of Compton effect

1. directly proportional to

• number of outer shell electrons (i.e., the electron density)
• physical density of the material

2. inversely proportional to

• photon energy

3. does not depend on

• atomic number (unlike photoelectric and pair production)

In other words, the Compton effect's probability is determined by the number of electrons per gram in the absorbing material, which is roughly the same for most elements (approximately 3 x 1023). With the exception of hydrogen, which has no neutrons in its nucleus and thus has an electron density twice that of all other elements (approximately 6 x 1023 ), therefore the Compton effect is independent of the absorber's atomic number (Z). When human tissues are irradiated in the 30 keV to 30 MeV energy range, which is the diagnostic and therapeutic radiation range, the Compton effect becomes the dominant process.