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% 9.2×1021 y[1] εε 78Se
79Kr syn 35 h ε 79Br
β+ 79Br
γ –
80Kr 2.29% stable
81Kr trace 2.3×105 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)

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 ±1.3×1021 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)×105 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
See also: Nuclear reprocessing

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.
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