Gamma Rays

[Rennhack]

Gamma rays are electromagnetic waves or photons emitted from the nucleus (center) of an atom.

[Rennhack]

High-energy electromagnetic radiation emitted by certain radionuclides when their nuclei transition from a higher to a lower energy state.  These rays have high energy and a short wave length.  All gamma rays emitted from a given isotope have the same energy, a characteristic that enables scientists to identify which gamma emitters are present in a sample.  Gamma rays are very similar to x-rays.

http://www.epa.gov/radiation/understand/gamma.htm