Presentation Transcript
Gamma () Decay :Gamma () Decay
Gamma () Decay :Gamma () Decay If a nucleus only needs to rid itself of excess energy, it will emit a photon.
Photons emitted from unstable nuclei are referred to as Gamma () Rays
Properties of Photon (x and ) Radiation: :Properties of Photon (x and ) Radiation: No mass
No electric charge
Low SI and low LET
More penetrating than α or β
Slide 4:Gamma photons are packets of pure energy, like visible light, just higher in energy and more penetrating.
Photon radiation is also referred to as Electromagnetic Radiation
Slide 5:The Electromagnetic Energy Spectrum Visible IR Microwaves RF UV X-rays -rays Cosmic Low E Long Low f High E Short High f Symbols: = wavelength f = frequency E = energy
Metastable :Metastable Nuclei which are in an excited energy state may be designated by an asterisk (*) or by the letter “m” in the A - number.
The “m” designates a metastable (i.e, almost stable) state.
Slide 7:General Gamma Decay Equation: X A Z * X A Z + 0 0 parent daughter gamma Example: Ba 137m Ba 137 + 0 0
Slide 8:Radionuclides That Emit Gamma Radiation Radionuclide Decay Mode Gamma Energy 131I , 364 keV 137Cs 662 keV 60Co 1.17 MeV, 1.33 MeV
Facts About Gamma Emitters :Facts About Gamma Emitters Gamma emitters are monoenergetic.
The penetrating power of gamma radiation depends upon its energy.
The best shielding material against gamma radiation: sufficiently thick lead (or other high Z material).
Facts to Remember :Facts to Remember Photon radiation (i.e., gammas and x-rays) have neither mass nor carry electric charge.
Therefore photons cannot interact electrically with matter through which they pass.
In order to produce ionization events in matter, photons must interact directly with shell electrons or the atomic nucleus.
Slide 11:Comparison of Relative Specific Ionizations of Various Types of Radiation
Remember: :Remember: Always recall the basic ways to protect yourself from any form of radiation
Minimize time spent near radiation sources.
Increase your distance from radiation sources.
Use appropriate shielding when available and when practical. ALARA