Physics:Isotopes of nitrogen

Short description: Isotopes of the element nitrogen

Main isotopes of Chemistry:nitrogen (₇N)

Iso­tope Decay abun­dance half-life (t1/2) mode pro­duct 13N syn 9.965 min β+ 13C 14N 99.6% stable 15N 0.4% stable
Standard atomic weight Ar, standard(N)	[14.00643, 14.00728] Conventional: 14.007

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(4) min. 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(36) yoctoseconds, though the half-life of nitrogen-9 has not been measured exactly.

List of isotopes

Nuclide	Z	N	Isotopic mass (u)	Half-life [resonance width]	Decay mode	Daughter isotope	Spin and parity	Physics:Natural abundance (mole fraction)
	Excitation energy							Normal proportion	Range of variation
9N	7	2		<1 as	5p	4He
10N	7	3	10.04165(43)	143(36) ys	p ?	9C ?	1−, 2−
11N	7	4	11.026158(5)	585(7) ys [780.0(9.3) keV]	p	10C	1/2+
11mN	740(60) keV			690(80) ys	p		1/2−
12N	7	5	12.0186132(11)	11.000(16) ms	β+ (98.07(4)%)	12C	1+
					β+α (1.93(4)%)	8Be
13N	7	6	13.00573861(29)	9.965(4) min	β+	13C	1/2−
14N	7	7	14.003074004251(241)	Stable			1+	[0.99578, 0.99663]
14mN	2312.590(10) keV				IT	14N	0+
15N	7	8	15.000108898266(625)	Stable			1/2−	[0.00337, 0.00422]
16N	7	9	16.0061019(25)	7.13(2) s	β− (99.99846(5)%)	16O	2−
					β−α (0.00154(5)%)	12C
16mN	120.42(12) keV			5.25(6) μs	IT (99.999611(25)%)	16N	0−
					β− (0.000389(25)%)	16O
17N	7	10	17.008449(16)	4.173(4) s	β−n (95.1(7)%)	16O	1/2−
					β− (4.9(7)%)	17O
					β−α (0.0025(4)%)	13C
18N	7	11	18.014078(20)	619.2(1.9) ms	β− (80.8(1.6)%)	18O	1−
					β−α (12.2(6)%)	14C
					β−n (7.0(1.5)%)	17O
					β−2n ?	16O ?
19N	7	12	19.017022(18)	336(3) ms	β− (58.2(9)%)	19O	1/2−
					β−n (41.8(9)%)	18O
20N	7	13	20.023370(80)	136(3) ms	β− (57.1(1.4)%)	20O	(2−)
					β−n (42.9(1.4)%)	19O
					β−2n ?	18O ?
21N	7	14	21.02709(14)	85(5) ms	β−n (87(3)%)	20O	(1/2−)
					β− (13(3)%)	21O
					β−2n ?	19O ?
22N	7	15	22.03410(22)	23(3) ms	β− (54.0(4.2)%)	22O	0−#
					β−n (34(3)%)	21O
					β−2n (12(3)%)	20O
23N	7	16	23.03942(45)	13.9(1.4) ms	β− (> 46.6(7.2)%)	23O	1/2−#
					β−n (42(6)%)	22O
					β−2n (8(4)%)	21O
					β−3n (< 3.4%)	20O
24N?	7	17	24.05039(43)#	< 52 ns	n ?	23N ?
25N?	7	18	25.06010(54)#	< 260 ns	n ?	24N ?	1/2−#
					2n ?	23N ?
					β− ?	25O ?

Nitrogen-13

Nitrogen-13 and oxygen-15 are produced in the atmosphere when gamma rays (for example from lightning) knock neutrons out of nitrogen-14 and oxygen-16:

¹⁴N + γ → ¹³N + n

¹⁶O + γ → ¹⁵O + n

The nitrogen-13 produced as a result decays with a half-life of 9.965(4) min to carbon-13, emitting a positron. The positron quickly annihilates with an electron, producing two gamma rays of about 511 keV. After a lightning bolt, this gamma radiation dies down with a half-life of ten minutes, but these low-energy gamma rays go only about 90 metres through the air on average, so they may only be detected for a minute or so as the "cloud" of ¹³N and ¹⁵O floats by, carried by the wind.

Nitrogen-14

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.

Like all elements heavier than lithium, 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(30) years.

Nitrogen-15

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.

Nitrogen-16

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, but its decay back to ¹⁶O produces high-energy gamma radiation (5 to 7 MeV). 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.