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Isotopes of the element nitrogen

Natural nitrogen (7N) consists of two stable isotopes: the vast majority (99.6%) of naturally occurring nitrogen is nitrogen 14, with the remainder being nitrogen 15. Thirteen radioisotopes are also known, with atomic masses ranging from 9 to 23, along with three nuclear isomers. All of these radioisotopes are short lived, the longest lived being nitrogen 13 with a half life of 9.965. All of the others have half lives below 7.15 seconds, with most of these being below 620 milliseconds. Most of the isotopes with atomic mass numbers below 14 decay to isotopes of carbon, while most of the isotopes with masses above 15 decay to isotopes of oxygen. The shortest lived known isotope is nitrogen 10, with a half life of 143, though the half life of nitrogen 9 has not been measured exactly.

Nitrogen 14 is one of two stable (non radioactive) isotopes of the chemical element nitrogen, which makes about 99.636% of natural nitrogen. Nitrogen 14 is one of the very few stable nuclides with both an odd number of protons and of neutrons (seven each) and is the only one to make up a majority of its element. Each proton or neutron contributes a nuclear spin of plus or minus spin 1/2, giving the nucleus a total magnetic spin of one. The original source of nitrogen 14 and nitrogen 15 in the Universe is believed to be stellar nucleosynthesis, where they are produced as part of the CNO cycle. Nitrogen 14 is the source of naturally occurring, radioactive, carbon 14. Some kinds of cosmic radiation cause a nuclear reaction with nitrogen 14 in the upper atmosphere of the Earth, creating carbon 14, which decays back to nitrogen 14 with a half life of 5700.

Nitrogen 15 is a rare stable isotope of nitrogen. Two sources of nitrogen 15 are the positron emission of oxygen 15 and the beta decay of carbon 15. Nitrogen 15 presents one of the lowest thermal neutron capture cross sections of all isotopes. Nitrogen 15 is frequently used in NMR (Nitrogen 15 NMR spectroscopy). Unlike the more abundant nitrogen 14, which has an integer nuclear spin and thus a quadrupole moment, 15N has a fractional nuclear spin of one half, which offers advantages for NMR such as narrower line width. Nitrogen 15 tracing is a technique used to study the nitrogen cycle.

The radioisotope 16N is the dominant radionuclide in the coolant of pressurised water reactors or boiling water reactors during normal operation. It is produced from 16O (in water) via an (n,p) reaction, in which the 16O atom captures a neutron and expels a proton. It has a short half life of about 7.1 s, Because of this, access to the primary coolant piping in a pressurised water reactor must be restricted during reactor power operation. It is a sensitive and immediate indicator of leaks from the primary coolant system to the secondary steam cycle and is the primary means of detection for such leaks.