Energetic Quanta: Gamma-Rays

Gamma rays…

  • Are emitted from the nucleus to trim excess energy.
  • Tend to carry higher energies than X-rays, but this does not have to be the case

For example, after a larger energy decay particle (e.g. a beta particle) is emitted, the nucleus may still be slightly unstable (i.e., the atom remains in an isomeric or excited state).  Emission of a gamma ray provides a means to lose a smaller amount of excess energy.

Important examples of gamma emitters: potassium-40, cobalt-60, cesium-137, and technetium-99m

Simplified electromagnetic spectrum with relative wavelength scale. Photons in the spectrum of visible light are energized at 2 to 3 eV. Contrast this with the energies carried by X-rays and gamma rays – ranging from thousands to millions of electron-volts.

Energetic Quanta: X-rays & Gamma-Rays

Gamma rays and X-rays are types of photons…

  • That represent pure electromagnetic energy
  • That progress at the speed of light
  • That may pass through all human tissues unimpeded and unchanged
  • Having no mass or charge, are neither attracted to nor repulsed by charged particles
  • Gamma-rays originate from the nucleus
  • X-rays originate from electron clouds

Energetic Quanta: Beta Particles

Beta Particles…

  • Are smaller (1/2000 the size of proton) and less energetic than alpha particles
  • Have negative charge
  • Are created when a neutron transmutates into a proton
  • Are emitted during decay of iodine-131, phosphorus-32, carbon-14, and strontium-90

Energetic Quanta: Neutrons

Neutrons…

  • Are uncharged particles
  • May carry significant kinetic energy (”Fast Neutrons”)
  • May collide with a nuclear proton, causing its ejection (”Recoil Protons”)
  • Produce biologically-important ionizations and excitations via such energetic recoil protons
  • Are often produced as part of fission reactions

Energetic Quanta: Alpha Particles

Alpha particles…

  • Are large and positively charged
  • Tend to cause ionizations and lose energy over a very short distance
  • Are composed of two protons and two neutrons (i.e. a naked helium nucleus)
  • Large size + relatively high charge prevent deep penetration of matter (blocked by dead skin or paper)
  • Chronic exposure to inhaled alpha particles is a lung cancer risk
  • Are important in the uranium decay series, of which radon is a product

Özel Arama
Åžubat 2010
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