Neutron capture is a process in which a neutron collides with a nucleus and becomes part of this nucleus caused by nuclear forces. It interacts without release of another heavy particle. A gamma ray photon is emitted as an immediate result of the neutron capture process. Through the neutron capture the nucleus becomes a heavier isotope of the same element. The kind of decay depends on the isotope and its stability.
This process is for example part of the neutron activation analysis, in which a sample is positioned in a neutron beam and also used in the 'boron neutron capture therapy'.

See also Thermal Neutrons, Epithermal Neutron, Neutron Activation Analysis, Nuclear Charge Number, Deuteron, Isomeric Transition, Isotones, N P Reaction.

The process of pair production is the creation of a particle and its antiparticle. If a photon with a minimum energy of the rest mass of an electron and a positron hits a nucleus an electron and a positron is emitted. The surplus energy appears as the kinetic energy of the two created particles. Conservation of energy and momentum makes pair production possible or not.

Quantum is a discrete and the smallest natural unit of energy and momentum. Planck makes the assumption that every energy transfer on a sub-atomic level consist of small units, called quanta. The view of electromagnetic energy as photons reflects this quantization.
E = h x v
E = energy
h = Planck quantum of action = 6.6261 x 10^-27 erg sec
v = frequency.

Transition is the nuclear change from one energy state to another, generally accompanied by the emission of particles or photons.

See Decay.

An x-ray film is a photographic film used to generate a visual x-ray image. X-ray films are rarely used as the only radiation detector. Commonly they are used in conjunction with intensifying screens placed in the film cassette, because high resolution films have a poor sensitivity to x-rays. At direct film exposure, only a small amount of x-ray photons will be absorbed and react with the film emulsion. An intensifying screen contains scintillating materials to convert x-ray radiation into light or lows electromagnetic energies.
X-ray films provide very good spatial resolution and contrast, but need long exposures times and chemical processing.

See also Conventional Radiography and Digital Radiography.