Isotopes of aluminium

Aluminium or aluminum (₁₃Al) has 22 known isotopes from ²²Al to ⁴³Al and 4 known isomers. Only ²⁷Al (stable isotope) and ²⁶Al (radioactive isotope, t_1/2 = 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.

Main isotopes of aluminium (₁₃Al)

Iso­tope Decay abun­dance half-life (t1/2) mode pro­duct ^26Al trace 7.17×10^5 y β^+ (85%) ^26Mg ε (15%) ^26Mg γ – ^27Al 100% stable
Standard atomic weight Ar, standard(Al)	26.9815385(7)[1]

List of isotopes

Nuclide[2] [n 1]	Z	N	Isotopic mass (Da)[3] [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)×10^5 years	β^+ (85%)	^26Mg	5+	Trace[n 9]
					ε (15%) [4]
^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)#	10# ms [>260 ns]	β^−	^40Si
^41Al	13	28	41.03588(54)#	2# ms [>260 ns]	β^−	^41Si	5/2+#
^42Al	13	29	42.04305(64)#	1# ms [>170 ns]	β^−	^42Si
^43Al	13	30	43.05048(86)#	1# ms [>170 ns]	β^−	^42Si

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. # – 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

Main article: Aluminium-26

The decay level scheme for ²⁶Al and ^26mAl to ²⁶Mg.[4][5]

Cosmogenic aluminium-26 was first applied 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.[6]

See also

References

1. 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.
2. 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.
3. 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.
4. "Physics 6805 Topics in Nuclear Physics". Ohio State University. Retrieved 12 June 2019.
5. 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.
6. R. T. Dodd (1986). Thunderstones and Shooting Stars. pp. 89–90. ISBN 978-0-674-89137-1.

External links

• Aluminum isotopes data from The Berkeley Laboratory Isotopes Project's