Isotopes of helium

Main isotopes of Chemistry:helium (2He) | Iso­tope | Decay

|

| abun­dance | half-life (t1/2) | mode | pro­duct
3He | 0.0002%  | stable
4He | 99.9998%  | stable
Standard atomic weight Ar, standard(He)|

* 4.002602(2)[1]

view * talk * edit

Helium (2He) has nine known isotopes, but only helium-3 (3He) and helium-4 (4He) are stable. All radioisotopes are short-lived; the only particle-bound ones are 6He and 8He with half-lives 806.9 and 119.5 milliseconds.

In Earth's atmosphere, the ratio of 3He to 4He is 1.37×10−6.[2] However, the isotopic abundance of helium varies greatly depending on its origin, though helium-4 is always in great preponderance. In the Local Interstellar Cloud, the proportion of 3He to 4He is 1.62(29)×10−4,[3] which is about 120 times higher than in Earth's atmosphere. Rocks from Earth's crust have isotope ratios varying by as much as a factor of ten; this is used in geology to investigate the origin of rocks and the composition of the Earth's mantle.[4] The different formation processes of the two stable isotopes of helium produce the differing isotope abundances.

Equal mixtures of liquid 3He and 4He below 0.8 K separate into two immiscible phases due to differences in quantum statistics: 4He atoms are bosons while 3He atoms are fermions.[5] Dilution refrigerators take advantage of the immiscibility of these two isotopes to achieve temperatures as low as a few millikelvin.

A mix of the two isotopes spontaneously separates into 3He-rich and 4He-rich regions.[6] Phase separation also exists in ultracold gas systems.[7] It has been shown experimentally in a two-component ultracold Fermi gas case.[8][9] The phase separation can compete with other phenomena as vortex lattice formation or an exotic Fulde–Ferrell–Larkin–Ovchinnikov phase.[10]

## Contents

* 1 List of isotopes
* 2 Helium-2 (diproton)
* 3 Helium-3
* 4 Helium-4
* 5 Helium-5
* 6 Helium-6 and helium-8
* 7 See also
* 8 References

## List of isotopes

Nuclide
| Z | N | Isotopic mass (u)
[n 1] | Half-life

[resonance width]  | Decay
mode
[n 2] | Daughter
isotope
[n 3] | Spin and
parity
[n 4][n 5] | Physics:Natural abundance (mole fraction)

|
|
|
|
|
|
|
|

Normal proportion  | Range of variation
2He[n 6] | 2  | 0  | 2.015894(2) | 1936 |  | p (> 99.99%)  | 1H | 0+#  |  |
β+ (< 0.01%)  | 2H
3He[n 6][n 7][n 8] | 2  | 1  | 3.016029321967(60) | 1934 | Stable | 1/2+  | 0.000002(2)[2] | [4.6×10−10, 0.000041][11]
4He[n 7][n 9] | 2  | 2  | 4.002603254130(158) | 1908 | Stable | 0+  | 0.999998(2)[2] | [0.999959, 1.000000][11]
5He  | 2  | 3  | 5.012057(21) | 1937 | 6.02(22)×10−22 s
[758(28) keV]  | n | 4He | 3/2−  |  |
6He[n 10] | 2  | 4  | 6.018885889(57) | 1936 | 806.92(24) ms | β− (99.999722(18)%)  | 6Li | 0+  |  |
β−d[n 11] (0.000278(18)%)  | 4He
7He  | 2  | 5  | 7.027991(8) | 1967 | 2.51(7)×10−21 s
[182(5) keV]  | n  | 6He  | (3/2)−  |  |
8He[n 12] | 2  | 6  | 8.033934388(95) | 1965 | 119.5(1.5) ms | β− (83.1(1.0)%)  | 8Li  | 0+  |  |
β−n (16(1)%)  | 7Li
β−t[n 13] (0.9(1)%)  | 5He
9He  | 2  | 7  | 9.043946(50) | 1987 | 2.5(2.3)×10−21 s | n  | The element Chemistry:Helium does not exist. | 1/2(+)  |  |
10He  | 2  | 8  | 10.05281531(10) | 1994 | 2.60(40)×10−22 s
[1.76(27) MeV]  | 2n  | 8He  | 0+  |  |

1. ↑ ( ) - Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
2. ↑ Modes of decay:  n: | Neutron emission

|

p: | Proton emission
3. ↑ Bold symbol as daughter - Daughter product is stable.
4. ↑ ( ) spin value - Indicates spin with weak assignment arguments.
5. ↑ # - Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
6. ↑ 6.0 6.1 Intermediate in the proton–proton chain
7. ↑ 7.0 7.1 Produced in Big Bang nucleosynthesis
8. ↑ This and 1H are the only stable nuclei with more protons than neutrons
9. ↑ Produced in alpha decay
10. ↑ Has 2 halo neutrons
11. ↑ d: Deuteron emission
12. ↑ Has 4 halo neutrons
13. ↑ t: Triton emission

## Helium-2 (diproton)

"Helium 2" redirects here. It is not to be confused with Helium II or Helium dimer.

Helium-2, 2He, is unbound. The only bound atom with a mass number of 2 is deuterium.[12][13] The nucleus of 2He, a diproton, consists of two protons with no neutrons. Its instability is due to spin–spin interactions in the nuclear force and the Pauli exclusion principle, which states that within a given quantum system two or more identical particles with the same half-integer spins (fermions) cannot simultaneously occupy the same quantum state; so 2He's two protons have opposite-aligned spins and the diproton itself has negative binding energy.[14]

A rare form of radioactivity is diproton emission, where a nucleus emits two protons in a quasi-bound 1S0 configuration, which then separate.[15] In 2000, Oak Ridge National Laboratory detected two-proton emission from 1810Ne, produced by a 179F ion beam onto a proton-rich target. But the experiment didn't have the sensitivity to distinguish if the emission was a decay by two separate protons, or by a diproton.[16][17] In 2008, the Istituto Nazionale di Fisica Nucleare confirmed 18Ne decayed to a diproton with a 31% branching ratio.[18][19] Several experiments have since detected diproton emission from other isotopes.[15]

The lack of a bound diproton has been used to argue for fine-tuning for the development of life due to its effect on Big Bang nucleosynthesis and stellar evolution.[20][21] Hypothetical models suggest that if the strong force was 2% greater, then diprotons would be bound (but still β+ decay to deuterium).[22] Recent studies have found that a universe with bound diprotons doesn’t preclude the development of stars and life.[22][21][13]

One impact of a hypothetical bound diproton is a change to the early steps of the proton-proton chain. In our universe, the first step of the proton-proton chain proceeds via the weak force,[23][24]

p \+ p → 21D \+ Positron + electron neutrino \+ 0.42 MeV

In the hypothetical, instead a diproton could form without the weak force,[13][22]

p \+ p → 22He

The diproton would then beta-plus decay into deuterium:

22He → 21D \+ Positron + electron neutrino.

With the overall formula,

p \+ p → 21D \+ Positron + electron neutrino.

Under the influence of electromagnetic interactions, the Jaffe-Low primitives[25] may leave the unitary cut, creating narrow two-nucleon resonances, like a diproton resonance with a mass of 2000 MeV and a width of a few hundred keV.[26] To search for this resonance, a beam of protons with kinetic energy 250 MeV and an energy spread below 100 keV is required, which is feasible considering the electron cooling of the beam.

## Helium-3

Main article: Physics:Helium-3

3He is the only stable isotope other than 1H with more protons than neutrons. There are many such unstable isotopes, such as 7Be and 8B. There is only a trace (~2ppm)[2] of 3He on Earth, mainly present since the formation of the Earth, although some falls to Earth trapped in cosmic dust.[4] Trace amounts are also produced by the beta decay of tritium.[27] In stars, however, 3He is more abundant, a product of nuclear fusion. Extraplanetary material, such as lunar and asteroid regolith, has traces of 3He from solar wind bombardment.

To become superfluid, 3He must be cooled to 2.5 millikelvin, ~900 times lower than 4He (2.17 K). This difference is explained by quantum statistics: 3He atoms are fermions, while 4He atoms are bosons, which condense to a superfluid more easily.

## Helium-4

Main article: Physics:Helium-4

The most common isotope, 4He, is produced on Earth by alpha decay of heavier elements; the alpha particles that emerge are fully ionized 4He nuclei. 4He is an unusually stable nucleus because it is doubly magic. It was formed in enormous quantities in Big Bang nucleosynthesis.

Terrestrial helium consists almost exclusively (all but ~2ppm)[2] of 4He. 4He's boiling point of 4.2 K is the lowest of all known substances except 3He. When cooled further to 2.17 K, it becomes a unique superfluid with zero viscosity. It solidifies only at pressures above 25 atmospheres, where it melts at 0.95 K.

## Helium-5

A 1987 Soviet stamp celebrating the T-15 tokamak depicts the helium-5 nucleus during deuterium–tritium fusion Fusion cross sections of major reactions. Without the resonance in helium-5, the DT reaction would be similar to the DD reaction.

Helium-5 is extremely unstable, decaying to helium-4 with a half-life of 602 yoctoseconds. It is briefly produced in the favorable fusion reaction:

2H+3H⟶5He*⟶4He+n+17.6 MeV

The reaction is greatly enhanced by the existence of a resonance. Helium-5, which has a natural spin state of -3/2 at the 0 MeV ground state, has a +3/2 excited spin state at 16.84 MeV. Because the reaction creates helium-5 nuclei with an energy level close to this state, it happens more frequently. This was discovered by Egon Bretscher, who was investigating weaponization of fusion reactions for the Manhattan Project.

The DT reaction specifically is 100 times more likely than the DD reaction at relevant energies, but would be similar without the resonance. The 2H-3He reaction benefits from a similar resonance in lithium-5, but is Coulomb-suppressed i.e. the +2 helium nucleus charge increases the electrostatic repulsion for fusing nuclei.[28]

## Helium-6 and helium-8

These are the long-lived radioactive isotope of helium; helium-6 beta decays with a half-life of 806.9 milliseconds, and helium-8 with a half-life of 119.5 milliseconds, though additional particle emission is possible and significant for the latter. 6He and 8He are thought to consist of a normal 4He nucleus surrounded by a neutron "halo" (of two neutrons in 6He and four neutrons in 8He). The unusual structures of halo nuclei may offer insights into the isolated properties of neutrons and physics beyond the Standard Model.[29][30]

## See also

Daughter products other than helium

* Isotopes of lithium
* Isotopes of hydrogen

## References

1. ↑ Meija, Juris; Coplen, Tyler B.; Berglund, Michael; Brand, Willi A.; De Bièvre, Paul; Gröning, Manfred; Holden, Norman E.; Irrgeher, Johanna 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.
2. ↑ 2.0 2.1 2.2 2.3 2.4 Cite error: Invalid `<ref>` tag; no text was provided for refs named `CIAAWhelium`
3. ↑ Busemann, H.; Bühler, F.; Grimberg, A.; Heber, V. S.; Agafonov, Y. N.; Baur, H.; Bochsler, P.; Eismont, N. A. et al. (2006-03-01). "Interstellar Helium Trapped with the COLLISA Experiment on the MiR Space Station—Improved Isotope Analysis by In Vacuo Etching" (in en). The Astrophysical Journal 639 (1): 246. doi:10.1086/499223. ISSN 0004-637X. Bibcode: 2006ApJ...639..246B.
4. ↑ 4.0 4.1 "Helium Fundamentals". http://www.mantleplumes.org/HeliumFundamentals.html.
5. ↑ The Encyclopedia of the Chemical Elements. p. 264.
6. ↑ Pobell, Frank (2007). Matter and methods at low temperatures (3rd rev. and expanded ed.). Berlin: Springer. ISBN 978-3-540-46356-6. OCLC 122268227.
7. ↑ Carlson, J.; Reddy, Sanjay (2005-08-02). "Asymmetric Two-Component Fermion Systems in Strong Coupling". Physical Review Letters 95 (6). doi:10.1103/PhysRevLett.95.060401. PMID 16090928. Bibcode: 2005PhRvL..95f0401C.
8. ↑ Shin, Y.; Zwierlein, M. W.; Schunck, C. H.; Schirotzek, A.; Ketterle, W. (2006-07-18). "Observation of Phase Separation in a Strongly Interacting Imbalanced Fermi Gas". Physical Review Letters 97 (3). doi:10.1103/PhysRevLett.97.030401. PMID 16907486. Bibcode: 2006PhRvL..97c0401S.
9. ↑ Zwierlein, Martin W.; Schirotzek, André; Schunck, Christian H.; Ketterle, Wolfgang (2006-01-27). "Fermionic Superfluidity with Imbalanced Spin Populations" (in en). Science 311 (5760): 492–496. doi:10.1126/science.1122318. ISSN 0036-8075. PMID 16373535. Bibcode: 2006Sci...311..492Z.
10. ↑ Kopyciński, Jakub; Pudelko, Wojciech R.; Wlazłowski, Gabriel (2021-11-23). "Vortex lattice in spin-imbalanced unitary Fermi gas". Physical Review A 104 (5). doi:10.1103/PhysRevA.104.053322. Bibcode: 2021PhRvA.104e3322K.
11. ↑ 11.0 11.1 Meija, Juris; Coplen, Tyler B.; Berglund, Michael; Brand, Willi A.; Bièvre, Paul De; Gröning, Manfred; Holden, Norman E.; Irrgeher, Johanna et al. (2016-03-01). "Isotopic compositions of the elements 2013 (IUPAC Technical Report)" (in en). Pure and Applied Chemistry 88 (3): 293–306. doi:10.1515/pac-2015-0503. ISSN 1365-3075.
12. ↑ Loveland, Walter D. (2017) (in en). Modern Nuclear Chemistry. New York Academy of Sciences Series (1st ed.). Newark: John Wiley & Sons, Incorporated. ISBN 978-1-119-32838-4.
13. ↑ 13.0 13.1 13.2 Adams, Fred C.; Howe, Alex R.; Grohs, Evan; Fuller, George M. (2021-07-01). "Effects of bound diprotons and enhanced nuclear reaction rates on stellar evolution". Astroparticle Physics 130. doi:10.1016/j.astropartphys.2021.102584. ISSN 0927-6505. Bibcode: 2021APh...13002584A. https://www.sciencedirect.com/science/article/pii/S0927650521000281.
14. ↑ Nuclear Physics in a Nutshell, C. A. Bertulani, Princeton University Press, Princeton, NJ, 2007, Chapter 1, ISBN 978-0-691-12505-3.
15. ↑ 15.0 15.1 Zhou, Long; Wang, Si-Min; Fang, De-Qing; Ma, Yu-Gang (2022-08-22). "Recent progress in two-proton radioactivity" (in en). Nuclear Science and Techniques 33 (8). doi:10.1007/s41365-022-01091-1. ISSN 1001-8042. Bibcode: 2022NuScT..33..105Z. https://link.springer.com/10.1007/s41365-022-01091-1.
16. ↑ J. Gómez del Campo et al. (2001). "Decay of a Resonance in 18Ne by the Simultaneous Emission of Two Protons". Physical Review Letters 86 (2001): 43–46. doi:10.1103/PhysRevLett.86.43. PMID 11136089. Bibcode: 2001PhRvL..86...43G.
17. ↑ Physicists discover new kind of radioactivity , in physicsworld.com Oct 24, 2000.
18. ↑ Schewe, Phil (2008-05-29). "New Form of Artificial Radioactivity". Physics News Update (865 #2). http://www.aip.org/pnu/2008/split/865-2.html.
19. ↑ Raciti, G.; Cardella, G.; De Napoli, M.; Rapisarda, E.; Amorini, F.; Sfienti, C. (2008). "Experimental Evidence of 2He Decay from 18Ne Excited States". Phys. Rev. Lett. 100 (19): 192503–192506. doi:10.1103/PhysRevLett.100.192503. PMID 18518446. Bibcode: 2008PhRvL.100s2503R.
20. ↑ Adams, Fred C. (2019-05-15). "The degree of fine-tuning in our universe — and others". Physics Reports 807: 1–111. doi:10.1016/j.physrep.2019.02.001. ISSN 0370-1573. Bibcode: 2019PhR...807....1A. https://www.sciencedirect.com/science/article/pii/S0370157319300511.
21. ↑ 21.0 21.1 MacDonald, J.; Mullan, D.J. (2009). "Big Bang Nucleosynthesis: The strong nuclear force meets the weak anthropic principle". Physical Review D 80 (4). doi:10.1103/PhysRevD.80.043507. Bibcode: 2009PhRvD..80d3507M.
22. ↑ 22.0 22.1 22.2 Bradford, R. A. W. (27 August 2009). "The effect of hypothetical diproton stability on the universe". Journal of Astrophysics and Astronomy 30 (2): 119–131. doi:10.1007/s12036-009-0005-x. Bibcode: 2009JApA...30..119B. http://rickbradford.co.uk/Diprotons.pdf.
23. ↑ Iliadis, Christian (2015). Nuclear Physics of Stars. New York Academy of Sciences Series (2nd ed.). Newark: John Wiley & Sons, Incorporated. ISBN 978-3-527-33648-7.
24. ↑ Dunlap, Richard A. (2023). An Introduction to the Physics of Nuclei and Particles. IOP Ebooks Series (2nd ed.). Bristol: Institute of Physics Publishing. ISBN 978-0-7503-6096-8.
25. ↑ Jaffe, R. L.; Low, F. E. (1979). "Connection between quark-model eigenstates and low-energy scattering". Physical Review D 19 (7): 2105–2118. doi:10.1103/PhysRevD.19.2105. Bibcode: 1979PhRvD..19.2105J. https://journals.aps.org/prd/abstract/10.1103/PhysRevD.19.2105.
26. ↑ Krivoruchenko, M. I. (2011). "Possibility of narrow resonances in nucleon-nucleon channels". Physical Review C 84 (1). doi:10.1103/PhysRevC.84.015206. Bibcode: 2011PhRvC..84a5206K. https://journals.aps.org/prc/abstract/10.1103/PhysRevC.84.015206.
27. ↑ K. L. Barbalace. "Periodic Table of Elements: Li—Lithium". EnvironmentalChemistry.com. http://environmentalchemistry.com/yogi/periodic/Li-pg2.html.
28. ↑ Chadwick, Mark B.; Paris, Mark W.; Haines, Brian M. (2023). "DT fusion through the 5He 3/2+ "Bretscher state" accounts for ≥25% of our existence via nucleosynthesis and for the possibility of fusion energy". arXiv:2305.00647 [physics.hist-ph].
29. ↑ "Helium-8 study gives insight into nuclear theory, neutron stars" (in en). Argonne National Laboratory. 2008-01-25. https://www.anl.gov/article/helium8-study-gives-insight-into-nuclear-theory-neutron-stars.
30. ↑ "Radioactive beams drive physics forward" (in en-GB). 1999-11-29. https://cerncourier.com/a/radioactive-beams-drive-physics-forward/.

* v
* t
* e

Isotopes of the chemical elements

| Group | 1 | 2 | 3 |  | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18

|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|

Period | Alkali metals  | Alkaline earth metals  |  |  |  |  |  |  |  |  |  |  |  |  |  | Pnicto­gens  | Chal­co­gens  | Halo­gens  | Noble gases
1 |

Iso's * List

1  |  |

Iso's * List

2 |

Iso's * List

3  |

Iso's * List

4  |  |

Iso's * List

5  |

Iso's * List

6  |

Iso's * List

7  |

Iso's * List

8  |

Iso's * List

9  |

Iso's * List

3 |

Iso's * List

11  |

Iso's * List

12  |  |

Iso's * List

13  |

Iso's * List

14  |

Iso's * List

15  |

Iso's * List

16  |

Iso's * List

17  |

Iso's * List

4 |

Iso's * List

19  |

Iso's * List

20  |

Iso's * List

21  |  |

Iso's * List

22  |

Iso's * List

23  |

Iso's * List

24  |

Iso's * List

25  |

Iso's * List

26  |

Iso's * List

27  |

Iso's * List

28  |

Iso's * List

29  |

Iso's * List

30  |

Iso's * List

31  |

Iso's * List

32  |

Iso's * List

33  |

Iso's * List

34  |

Iso's * List

35  |

Iso's * List

5 |

Iso's * List

37  |

Iso's * List

38  |

Iso's * List

39  |  |

Iso's * List

40  |

Iso's * List

41  |

Iso's * List

42  |

Iso's * List

43  |

Iso's * List

44  |

Iso's * List

45  |

Iso's * List

46  |

Iso's * List

47  |

Iso's * List

48  |

Iso's * List

49  |

Iso's * List

50  |

Iso's * List

51  |

Iso's * List

52  |

Iso's * List

53  |

Iso's * List

6 |

Iso's * List

55  |

Iso's * List

56  |

Iso's * List

57  |  |

Iso's * List

72  |

Iso's * List

73  |

Iso's * List

74  |

Iso's * List

75  |

Iso's * List

76  |

Iso's * List

77  |

Iso's * List

78  |

Iso's * List

79  |

Iso's * List

80  |

Iso's * List

81  |

Iso's * List

82  |

Iso's * List

83  |

Iso's * List

84  |

Iso's * List

85  |

Iso's * List

7 |

Iso's * List

87  |

Iso's * List

88  |

Iso's * List

89  |  |

Iso's * List

104  |

Iso's * List

105  |

Iso's * List

106  |

Iso's * List

107  |

Iso's * List

108  |

Iso's * List

109  |

Iso's * List

110  |

Iso's * List

111  |

Iso's * List

112  |

Iso's * List

113  |

Iso's * List

114  |

Iso's * List

115  |

Iso's * List

116  |

Iso's * List

117  |

Iso's * List

118
|  |  |  |  |

Iso's * List

58  |

Iso's * List

59  |

Iso's * List

60  |

Iso's * List

61  |

Iso's * List

62  |

Iso's * List

63  |

Iso's * List

64  |

Iso's * List

65  |

Iso's * List

66  |

Iso's * List

67  |

Iso's * List

68  |

Iso's * List

69  |

Iso's * List

70  |

Iso's * List

71  |
|  |

Iso's * List

90  |

Iso's * List

91  |

Iso's * List

92  |

Iso's * List

93  |

Iso's * List

94  |

Iso's * List

95  |

Iso's * List

96  |

Iso's * List

97  |

Iso's * List

98  |

Iso's * List

99  |

Iso's * List

100  |

Iso's * List

101  |

Iso's * List

102  |

Iso's * List

103

* Table of nuclides
* Categories: Isotopes
* Tables of nuclides
* Metastable isotopes
* Isotopes by element

0.00

(0 votes)

Original source: https://en.wikipedia.org/wiki/Isotopes of helium. Read more

|

Retrieved from "https://handwiki.org/wiki/index.php?title=Physics:Isotopes_of_helium&oldid=4369315"
*[v]: View this template
*[t]: Discuss this template
*[e]: Edit this template