gammaquanta

Gammaquanta, or gamma quanta, are quanta of the gamma-ray portion of the electromagnetic spectrum. In quantum terms, a gamma quantum is a photon with energy in the gamma range, typically from tens of keV up to several MeV, though observations of extreme astrophysical events can involve higher energies. Like all photons, gammaquanta have zero rest mass and travel at the speed of light in vacuum; they exhibit wave–particle duality and can be polarized.

Interactions with matter depend on energy. At lower gamma energies, the photoelectric effect dominates; at intermediate energies, Compton scattering is most important; and above about 1.022 MeV, pair production becomes possible near atomic nuclei. The penetrating power of gammaquanta makes shielding require dense materials such as lead or tungsten, and their attenuation is described by energy-dependent cross sections and absorption lengths.

Production mechanisms include nuclear transitions within radioactive decay (gamma emission following beta decay or isomeric transitions) and more energetic processes in astrophysical sources such as pulsars, supernova remnants, and gamma-ray bursts. Laboratory production occurs for medical, industrial, and research applications.

Detection and spectroscopy rely on converting gammaquanta into measurable signals. Common detectors include scintillators (for example NaI(Tl) or CsI(Tl)) and semiconductor detectors (such as germanium), enabling energy measurements, timing, and imaging. In medicine, 511 keV gamma quanta from positron annihilation underpin PET imaging.

Gammaquanta are central to nuclear spectroscopy, medical imaging, and high-energy astrophysics, offering detailed isotopic information and insights into extreme physical processes, while requiring careful safety measures due to their ionizing nature.