Isotopes of aluminium (13Al)
Main isotopes[1] Decay
abun­dance half-life (t1/2) mode pro­duct
26Al trace 7.17×105 y β+84% 26Mg
ε[2]16% 26Mg
γ –
27Al 100% stable
Standard atomic weight Ar°(Al)
  • 26.9815384±0.0000003
  • 26.982±0.001 (abridged)[3][4]

Aluminium or aluminum (13Al) has 22 known isotopes from 22Al to 43Al and 4 known isomers. Only 27Al (stable isotope) and 26Al (radioactive isotope, t1/2 = 7.2×105 y) occur naturally, however 27Al comprises nearly all natural aluminium. Other than 26Al, all radioisotopes have half-lives under 7 minutes, most under a second. The standard atomic weight is 26.9815385(7). 26Al is produced from argon in the atmosphere by spallation caused by cosmic-ray protons. Aluminium isotopes have found practical application in dating marine sediments, manganese nodules, glacial ice, quartz in rock exposures, and meteorites. The ratio of 26Al to 10Be has been used to study the role of sediment transport, deposition, and storage, as well as burial times, and erosion, on 105 to 106 year time scales. 26Al has also played a significant role in the study of meteorites.

List of isotopes

Nuclide[5]
[n 1]		 Z N Isotopic mass (Da)[6]
[n 2][n 3]		 Half-life
 Decay
mode
[n 4]		 Daughter
isotope
[n 5]		 Spin and
parity
[n 6][n 7]		 Natural abundance (mole fraction)
Excitation energy[n 7] Normal proportion Range of variation
22Al 13 9 22.01954(43)# 91.1(5) ms β+, p (55%) 21Na (4)+
β+ (43.862%) 22Mg
β+, 2p (1.1%) 20Ne
β+, α (0.038%) 18Ne
23Al 13 10 23.0072444(4) 470(30) ms β+ (99.54%) 23Mg 5/2+
β+, p (0.46%) 22Na
24Al 13 11 23.99994754(25) 2.053(4) s β+ (99.9634%) 24Mg 4+
β+, α (.035%) 20Ne
β+, p (.0016%) 23Na
24mAl 425.8(1) keV 130(3) ms IT (82.5%) 24Al 1+
β+ (17.5%) 24Mg
β+, α (.028%) 20Ne
25Al 13 12 24.99042831(7) 7.183(12) s β+ 25Mg 5/2+
26Al[n 8] 13 13 25.98689186(7) 7.17(24)×105 y β+ (85%) 26Mg 5+ Trace[n 9]
ε (15%)[7]
26mAl 228.306(13) keV 6.3460(8) s β+ 26Mg 0+
27Al 13 14 26.98153841(5) Stable 5/2+ 1.0000
28Al 13 15 27.98191009(8) 2.245(5) min β− 28Si 3+
29Al 13 16 28.9804532(4) 6.56(6) min β− 29Si 5/2+
30Al 13 17 29.982968(3) 3.62(6) s β− 30Si 3+
31Al 13 18 30.9839498(24) 644(25) ms β− (98.4%) 31Si 5/2(+)
β−, n (1.6%) 30Si
32Al 13 19 31.988084(8) 33.0(2) ms β− (99.3%) 32Si 1+
β−, n (.7%) 31Si
32mAl 955.7(4) keV 200(20) ns IT 32Al (4+)
33Al 13 20 32.990878(8) 41.7(2) ms β− (91.5%) 33Si 5/2+
β−, n (8.5%) 32Si
34Al 13 21 33.996779(3) 56.3(5) ms β− (74%) 34Si (4−)
β−, n (26%) 33Si
34mAl 550(100)# keV 26(1) ms β− (70%) 34Si (1+)
β−, n (30%) 33Si
35Al 13 22 34.999760(8) 37.2(8) ms β− (62%) 35Si 5/2+#
β−, n (38%) 34Si
36Al 13 23 36.00639(16) 90(40) ms β− (70%) 36Si
β−, n (30%) 35Si
37Al 13 24 37.01053(19) 11.5(4) ms β− (71%) 37Si 5/2+#
β−, n (29%) 36Si
38Al 13 25 38.0174(4) 9.0(7) ms β− 38Si
39Al 13 26 39.02217(43)# 7.6(16) ms β−, n (90%) 38Si 5/2+#
β− (10%) 39Si
40Al 13 27 40.02962(43)# 5.7(3 (stat), 2 (sys)) ms[8] β−, n (64%) 39Si
β−, 2n (20%) 38Si
β− (16%) 40Si
41Al 13 28 41.03588(54)# 3.5(8 (stat), 4 (sys)) ms[8] β−, n (86%) 40Si 5/2+#
β−, 2n (11%) 39Si
β− (3%) 41Si
42Al 13 29 42.04305(64)# 1# ms [>170 ns] β− 42Si
43Al 13 30 43.05048(86)# 1# ms [>170 ns] β− 43Si
This table header & footer:
  1. ↑ mAl – 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. ↑ Modes of decay:
    IT:Isomeric transition
  5. ↑ Bold symbol as daughter – Daughter product is stable.
  6. ↑ ( ) spin value – Indicates spin with weak assignment arguments.
  7. 1 2 # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  8. ↑ Used in radiodating events early in the Solar System's history and meteorites
  9. ↑ cosmogenic

Aluminium-26

The decay level scheme for 26Al and 26mAl to 26Mg.[7][9]

Cosmogenic aluminium-26 was first described in studies of the Moon and meteorites. Meteorite fragments, after departure from their parent bodies, are exposed to intense cosmic-ray bombardment during their travel through space, causing substantial 26Al production. After falling to Earth, atmospheric shielding protects the meteorite fragments from further 26Al production, and its decay can then be used to determine the meteorite's terrestrial age. Meteorite research has also shown that 26Al was relatively abundant at the time of formation of our planetary system. Most meteoriticists believe that the energy released by the decay of 26Al was responsible for the melting and differentiation of some asteroids after their formation 4.55 billion years ago.[10]

References

  1. ↑ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  2. ↑ Mougeot, X. (2019). "Towards high-precision calculation of electron capture decays". Applied Radiation and Isotopes. 154 (108884). doi:10.1016/j.apradiso.2019.108884.
  3. ↑ "Standard Atomic Weights: Aluminium". CIAAW. 2017.
  4. ↑ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; et al. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  5. ↑ Half-life, decay mode, nuclear spin, and isotopic composition is sourced in:
    Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
  6. ↑ Wang, M.; Audi, G.; Kondev, F. G.; Huang, W. J.; Naimi, S.; Xu, X. (2017). "The AME2016 atomic mass evaluation (II). Tables, graphs, and references" (PDF). Chinese Physics C. 41 (3): 030003-1–030003-442. doi:10.1088/1674-1137/41/3/030003.
  7. 1 2 "Physics 6805 Topics in Nuclear Physics". Ohio State University. Retrieved 12 June 2019.
  8. 1 2 Crawford, H. L.; Tripathi, V.; Allmond, J. M.; et al. (2022). "Crossing N = 28 toward the neutron drip line: first measurement of half-lives at FRIB". Physical Review Letters. 129 (212501): 212501. Bibcode:2022PhRvL.129u2501C. doi:10.1103/PhysRevLett.129.212501. PMID 36461950. S2CID 253600995.
  9. ↑ Diehl, R (13 Dec 2005). "26Al in the inner Galaxy" (PDF). Astronomy & Astrophysics. 449 (3): 1025–1031. doi:10.1051/0004-6361:20054301. Retrieved 12 June 2019.
  10. ↑ R. T. Dodd (1986). Thunderstones and Shooting Stars. Harvard University Press. pp. 89–90. ISBN 978-0-674-89137-1.
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