page_title: Gamma ray
section_title: Decay schemes
hierarchical_section_title: Gamma ray / Sources / Radioactive decay (gamma decay) / Decay schemes
caption_attribution_description: Gamma spectrum of 60Co, observed with a germanium detector. x-axis gauged to energy, designation in German.
context_page_description: A gamma ray, or gamma radiation, is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves and so imparts the highest photon energy. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation gamma rays based on their relatively strong penetration of matter; in 1900 he had already named two less penetrating types of decay radiation alpha rays and beta rays in ascending order of penetrating power.
  Gamma rays from radioactive decay are in the energy range from a few kiloelectronvolts to approximately 8 megaelectronvolts, corresponding to the typical energy levels in nuclei with reasonably long lifetimes. The energy spectrum of gamma rays can be used to identify the decaying radionuclides using gamma spectroscopy. Very-high-energy gamma rays in the 100–1000 teraelectronvolt range have been observed from sources such as the Cygnus X-3 microquasar.
context_section_description: One example of gamma ray production due to radionuclide decay is the decay scheme for cobalt-60, as illustrated in the accompanying diagram. First, ⁶⁰
  Co
   decays to excited ⁶⁰
  Ni
   by beta decay emission of an electron of 0.31 MeV. Then the excited ⁶⁰
  Ni
   decays to the ground state (see nuclear shell model) by emitting gamma rays in succession of 1.17 MeV followed by 1.33 MeV. This path is followed 99.88% of the time:
  Another example is the alpha decay of ²⁴¹
  Am
   to form ²³⁷
  Np
  ; which is followed by gamma emission. In some cases, the gamma emission spectrum of the daughter nucleus is quite simple, (e.g. ⁶⁰
  Co
  /⁶⁰
  Ni
  ) while in other cases, such as with (²⁴¹
  Am
  /²³⁷
  Np
   and ¹⁹²
  Ir
  /¹⁹²
  Pt
  ), the gamma emission spectrum is complex, revealing that a series of nuclear energy levels exist.
caption: Gamma emission spectrum of cobalt-60
exif: {}