1. Interaction of High Energy Radiation with Matter review Two basic types Excitation electrons move to a higher orbital shell temporarily ~70% of charged particle deposited energy leads to excitation lasers, high-intensity sources of ultraviolet light, microwave transmitters and other devices that produce high intensity radio-frequency radiation. Ionization electrons absorb enough energy to be removed from orbit Average energy deposited per ion pair produced ~34 eV

2. Ionizing Radiation classification Directly Ionizing Directly Ionizing  Non-penetrating  Charged  Energy is transferred through electric (Coulombic) force interactions with orbiting electrons Indirectly Ionizing Indirectly Ionizing  Penetrating  Uncharged  Energy is absorbed (transferred) through collision with orbiting electrons

3. Ionization classification Negatrons – Positrons + Conversion Electrons – Auger electrons – xβ Gamma rays and X-rays γ Beta particles Indirectly Ionizing radiation No electric charge Penetrating radiation Directly Ionizing radiation Electric charge Non-penetrating path range path

4. Ionization and production of delta rays (secondary ionizations) Further ionizations or excitations Ionizations (energy transfer) Coulombic forces Further ionizations or excitations + + Charged Particles – non-penetrating interaction via the coulomb forces of attraction

5. . Bremsstrahlung x-ray

6. Photoelectric effect uncharged x- and gamma-ray interaction via direct collision Lack of charge permits passage of photon through matter without electrical interaction Total energy is transferred to orbiting electrons through direct impact Photon colliding with an orbiting electron in the K-shell Knocking out an electron and creating a vacancy Or alternatively energy is transferred to an auger electron Vacancy filled by cascading electrons from higher orbits, creating Characteristic x-rays

7. Compton scattering  Partial energy transferred to orbiting electrons through direct impact by an x- or gamma-ray  x- or gamma-ray scatters and continues at a lower energy  Electron energy is the difference between the imparted x- or gamma-ray energy and the orbital binding energy