Glossary

GLOSSARY

• Alpha decay
  Alpha decay is a process in which an unstable nucleus transforms into another nucleus by emitting an alpha particle. The mass number A of the nucleus decreases by four and the atomic number Z by two.
  
  
• Alpha particle
  The α particle is a nucleus of Helium-4, consisting of two protons and two neutrons.
  
  
• Antiparticle
  An antiparticle is a subatomic particle having the same mass as one of the particles of ordinary matter but opposite electric charge and magnetic moment.
  
  
• Beta minus decay
  Beta minus decay is a process in which a neutron transforms into a proton by emitting an electron and an antineutrino. The mass number A of the nucleus remains unchanged, and the atomic number Z increases by one. This process can happen spontaneously for both neutrons that are free and inside a nucleus.
  
  
• Beta plus decay
  Beta plus decay is a process in which a proton transforms into a neutron by emitting a positron and a neutrino. The mass number A of the nucleus remains unchanged, and the atomic number Z decreases by one. This process can happen spontaneously only for protons that are inside a nucleus.
  
  
• Electron capture
  Electron capture is a process in which a proton transforms into a neutron by capturing an atomic electron. A monoenergetic neutrino is emitted. The mass number A of the nucleus remains unchanged, and the atomic number Z decreases by one. This process can happen spontaneously only for protons that are inside a nucleus.
  
  
• Gamma decay
  Gamma decay is a process in which a nucleus in an excite state decays by emitting a gamma ray, which carries away the excitation energy of the nucleus. Gamma decay usually follows an alpha or a beta decay, since in many of these processes the nucleus is left in an excited state.
  
  
• Gamma-ray
  Gamma-rays are monoenergetic electromagnetic radiation (photons) emitted during the radioactive decay of atomic nuclei upon the de-excitation of atomic nuclei. Their energy ranges from few keV to few MeV.
  
  
• Neutrino and antineutrino
  A neutrino is an electrically neutral particle of extremely small mass (most likely lower than 1 eV). Neutrinos move at velocities close to the speed of light and interact very rarely with matter.
  The antineutrino is the antiparticle of the neutrino.
  
  
• Positron
  The positron is the antiparticle of the electron, having the same mass, but a positive charge +e.
  
  
• Q-value
  The Q-value of a process (either a decay or a nuclear reaction) is the amount of energy absorbed or released during the reaction. If a process has a positive Q-value, it can occur spontaneously. The Q-value is defined as the difference between the rest energies of the initial and final state or as the difference between the kinetic energies of the final and initial state.
  
  
• Rest energy
  The rest energy is a form of energy associated the mass of a particle. It is defined as: E= mc2, from the famous Einstein’s equation.