An analytical technique that can be used to detect elements when present in a sample. In neutron activation analysis the sample is exposed to a flux of thermal neutrons in a nuclear reactor. Some of these neutrons are captured by nuclides in the sample to form nuclides of the same atomic number but a higher mass number. These newly formed nuclides emit gamma radiation, which can be used to identify the element present by means of a gamma-ray spectrometer. Activation analysis has also been employed using high-energy charged particles, such as protons or alpha particles.

http://archaeometry.missouri.edu/naa_overview.html An overview of neutron activation analysis from the Archaeometry Laboratory, Missouri Research Reactor