Isotopes of krypton

There are 33 known isotopes of krypton (₃₆Kr) with atomic mass numbers from 69 through 101.[3] Naturally occurring krypton is made of five stable isotopes and one (⁷⁸
Kr
) which is slightly radioactive with an extremely long half-life, plus traces of radioisotopes that are produced by cosmic rays in the atmosphere.

Main isotopes of krypton (₃₆Kr)

Iso­tope Decay abun­dance half-life (t1/2) mode pro­duct ^78Kr 0.36% 9.2×10^21 y[1] εε ^78Se ^79Kr syn 35 h ε ^79Br β^+ ^79Br γ – ^80Kr 2.29% stable ^81Kr trace 2.3×10^5 y ε ^81Br γ – ^82Kr 11.59% stable ^83Kr 11.50% stable ^84Kr 56.99% stable ^85Kr syn 11 y β^− ^85Rb ^86Kr 17.28% stable
Standard atomic weight Ar, standard(Kr)	83.798(2)[2]

List of isotopes

Nuclide [n 1]	Z	N	Isotopic mass (Da) [n 2][n 3]	Half-life [n 4][n 5]	Decay mode [n 6]	Daughter isotope [n 7][n 8]	Spin and parity [n 9][n 5]	Natural abundance (mole fraction)
	Excitation energy							Normal proportion	Range of variation
^69Kr	36	33	68.96518(43)#	32(10) ms	β^+	^69Br	5/2−#
^70Kr	36	34	69.95526(41)#	52(17) ms	β^+	^70Br	0+
^71Kr	36	35	70.94963(70)	100(3) ms	β^+ (94.8%)	^71Br	(5/2)−
					β^+, p (5.2%)	^70Se
^72Kr	36	36	71.942092(9)	17.16(18) s	β^+	^72Br	0+
^73Kr	36	37	72.939289(7)	28.6(6) s	β^+ (99.32%)	^73Br	3/2−
					β^+, p (.68%)	^72Se
^73mKr	433.66(12) keV			107(10) ns			(9/2+)
^74Kr	36	38	73.9330844(22)	11.50(11) min	β^+	^74Br	0+
^75Kr	36	39	74.930946(9)	4.29(17) min	β^+	^75Br	5/2+
^76Kr	36	40	75.925910(4)	14.8(1) h	β^+	^76Br	0+
^77Kr	36	41	76.9246700(21)	74.4(6) min	β^+	^77Br	5/2+
^78Kr[n 10]	36	42	77.9203648(12)	9.2 ^+5.5 −2.6 ±1.3×10^21 y[1]	Double EC	^78Se	0+	0.00355(3)
^79Kr	36	43	78.920082(4)	35.04(10) h	β^+	^79Br	1/2−
^79mKr	129.77(5) keV			50(3) s			7/2+
^80Kr	36	44	79.9163790(16)	Stable			0+	0.02286(10)
^81Kr[n 11]	36	45	80.9165920(21)	2.29(11)×10^5 y	EC	^81Br	7/2+	trace
^81mKr	190.62(4) keV			13.10(3) s	IT (99.975%)	^81Kr	1/2−
					EC (.025%)	^81Br
^82Kr	36	46	81.9134836(19)	Stable			0+	0.11593(31)
^83Kr[n 12]	36	47	82.914136(3)	Stable			9/2+	0.11500(19)
^83m1Kr	9.4053(8) keV			154.4(11) ns			7/2+
^83m2Kr	41.5569(10) keV			1.83(2) h	IT	^83Kr	1/2−
^84Kr[n 12]	36	48	83.911507(3)	Stable			0+	0.56987(15)
^84mKr	3236.02(18) keV			1.89(4) µs			8+
^85Kr[n 12]	36	49	84.9125273(21)	10.776(3) y	β^−	^85Rb	9/2+	trace
^85m1Kr	304.871(20) keV			4.480(8) h	β^− (78.6%)	^85Rb	1/2−
					IT (21.4%)	^85Kr
^85m2Kr	1991.8(13) keV			1.6(7) µs [1.2(+10-4) µs]			(17/2+)
^86Kr[n 13][n 12]	36	50	85.91061073(11)	Observationally Stable[n 14]			0+	0.17279(41)
^87Kr	36	51	86.91335486(29)	76.3(5) min	β^−	^87Rb	5/2+
^88Kr	36	52	87.914447(14)	2.84(3) h	β^−	^88Rb	0+
^89Kr	36	53	88.91763(6)	3.15(4) min	β^−	^89Rb	3/2(+#)
^90Kr	36	54	89.919517(20)	32.32(9) s	β^−	^90mRb	0+
^91Kr	36	55	90.92345(6)	8.57(4) s	β^−	^91Rb	5/2(+)
^92Kr	36	56	91.926156(13)	1.840(8) s	β^− (99.96%)	^92Rb	0+
					β^−, n (.033%)	^91Rb
^93Kr	36	57	92.93127(11)	1.286(10) s	β^− (98.05%)	^93Rb	1/2+
					β^−, n (1.95%)	^92Rb
^94Kr	36	58	93.93436(32)#	210(4) ms	β^− (94.3%)	^94Rb	0+
					β^−, n (5.7%)	^93Rb
^95Kr	36	59	94.93984(43)#	114(3) ms	β^−	^95Rb	1/2(+)
^96Kr	36	60	95.942998(62)[4]	80(7) ms	β^−	^96Rb	0+
^97Kr	36	61	96.94856(54)#	63(4) ms	β^−	^97Rb	3/2+#
					β^−, n	^96Rb
^98Kr	36	62	97.95191(64)#	46(8) ms			0+
^99Kr	36	63	98.95760(64)#	40(11) ms			(3/2+)#
^100Kr	36	64	99.96114(54)#	10# ms [>300 ns]			0+
^101Kr	36	65	unknown	>635 ns	β^−, 2n	^99Rb	unknown
					β^−, n	^100Rb
					β^−	^101Rb

1. ^mKr – Excited nuclear isomer.
2. ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
3. # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
4. Bold half-life – nearly stable, half-life longer than age of universe.
5. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
6. Modes of decay:

   n:	Neutron emission

7. Bold italics symbol as daughter – Daughter product is nearly stable.
8. Bold symbol as daughter – Daughter product is stable.
9. ( ) spin value – Indicates spin with weak assignment arguments.
10. Primordial radionuclide
11. Used to date groundwater
12. Fission product
13. Formerly used to define the meter
14. Believed to decay by β⁻β⁻ to ⁸⁶Sr

• The isotopic composition refers to that in air.

Notable isotopes

Krypton-81

Radioactive krypton-81 is the product of reactions with cosmic rays that strike the atmosphere, along with the six stable or nearly stable krypton isotopes.[5] Krypton-81 has a half-life of about 229,000 years.

Krypton-81 has been used for dating old (50,000- to 800,000-year-old) groundwater.[6]

Krypton-81m

Radiopharmaceutical.

Krypton-85

Krypton-85 is a radioisotope of krypton that has a half-life of about 10.75 years. This isotope is produced by the nuclear fission of uranium and plutonium in nuclear weapons testing and in nuclear reactors, as well as by cosmic rays. An important goal of the Limited Nuclear Test Ban Treaty of 1963 was to eliminate the release of such radioisotopes into the atmosphere, and since 1963 much of that krypton-85 has had time to decay. However, it is inevitable that krypton-85 is released during the reprocessing of fuel rods from nuclear reactors.

Atmospheric concentration

The atmospheric concentration of krypton-85 around the North Pole is about 30 percent higher than that at the Amundsen–Scott South Pole Station because nearly all of the world's nuclear reactors and all of its major nuclear reprocessing plants are located in the northern hemisphere, and also well-north of the equator.[7] To be more specific, those nuclear reprocessing plants with significant capacities are located in the United States, the United Kingdom, the French Republic, the Russian Federation, Mainland China (PRC), Japan, India, and Pakistan.

Krypton-86

Krypton-86 was formerly used to define the meter from 1960 until 1983, when the definition of the meter was based on the wavelength of the 606 nm (orange) spectral line of a krypton-86 atom.[8]

Others

All other radioisotopes of krypton have half-lives of less than one day, except for krypton-79, a positron emitter with a half-life of about 35.0 hours.

References

1. Patrignani, C.; et al. (Particle Data Group) (2016). "Review of Particle Physics". Chinese Physics C. 40 (10): 100001. Bibcode:2016ChPhC..40j0001P. doi:10.1088/1674-1137/40/10/100001. See p. 768
2. Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
3. "Chart of Nuclides". Brookhaven National Laboratory.
5. Leya, I.; Gilabert, E.; Lavielle, B.; Wiechert, U.; Wieler, W. (2004). "Production rates for cosmogenic krypton and argon isotopes in H-chondrites with known ³⁶Cl-³⁶Ar ages" (PDF). Antarctic Meteorite Research. 17: 185–199. Bibcode:2004AMR....17..185L.
6. N. Thonnard; L. D. MeKay; T. C. Labotka (2001). "Development of Laser-Based Resonance Ionization Techniques for 81-Kr and 85-Kr Measurements in the Geosciences" (PDF). University of Tennessee, Institute for Rare Isotope Measurements: 4–7. doi:10.2172/809813. Cite journal requires |journal= (help)
7. "Resources on Isotopes". U.S. Geological Survey. Archived from the original on 2001-09-24. Retrieved 2007-03-20.
8. Baird, K. M.; Howlett, L. E. (1963). "The International Length Standard". Applied Optics. 2 (5): 455–463. doi:10.1364/AO.2.000455.

• Isotope masses from:
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
• Isotopic compositions and standard atomic masses from:
  • de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
  • Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051. Lay summary.
• Half-life, spin, and isomer data selected from the following sources.
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
  • National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
  • Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.

External links

• Brookhaven National Laboratory: Krypton-101 information