MASS SPECTROMETER An instrument for separation and measurement of isotopes by their mass.
NET COUNTING RATE Sample counting rate minus background counting rate.
NEUTRONS Elementary particles in the nucleus having no electric charge and the mass of one atomic mass unit.
NUCLIDE A species of atom characterized by the constitution of its nucleus.
ORIGINAL (strontium, lead, etc.) Common strontium, lead, etc., taken into a system at the time of its formation.
PALEONTOLOGY The study of fossil remains.
PARENT The radioactive element from which a daughter nuclide is produced by radioactive decay.
PLUMBOLOGY The study of the uranium and thorium-lead decay systems. The name is derived from the Latin name for lead, plumbum.
PRIMORDIAL Present at the time of the formation of the earth.
PROPORTIONAL COUNTER An instrument for detecting radiation by producing pulses of electrical charge that are proportional to the energy of the radiation being measured. The design permits use of radiation of a desired energy level (within limits), and discrimination against other radiation, especially background radiation.