Isotopes of aluminium

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Aluminium (Al) has multiple isotopes. Only ²⁷Al (stable isotope) and ²⁶Al (radioactive isotope, t_1/2 = 7.2 × 10⁵ y) occur naturally, however ²⁷Al has a natural abundance of 99.9+ %. Standard atomic mass is 26.9815386(8) u. 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 transport, deposition, sediment storage, burial times, and erosion on 10⁵ to 10⁶ year time scales.^{[citation needed]}

Cosmogenic ²⁶Al 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.^[1]

1 Table
- 1.1 Notes
2 References
3 External links

[edit] Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
nuclide symbol	excitation energy			half-life	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
²¹Al	13	8	21.02804(32)#	<35 ns	1/2+#
²²Al	13	9	22.01952(10)#	59(3) ms	(3)+
²³Al	13	10	23.007267(20)	470(30) ms	5/2+#
^23mAl				~0.35 s	#79
²⁴Al	13	11	23.9999389(30)	2.053(4) s	4+
^24mAl	425.8(1) keV			131.3(25) ms	1+
²⁵Al	13	12	24.9904281(5)	7.183(12) s	5/2+
²⁶Al	13	13	25.98689169(6)	7.17(24)E+5 a	5+
^26mAl	228.305(13) keV			6.3452(19) s	0+
²⁷Al	13	14	26.98153863(12)	STABLE	5/2+	1.0000
²⁸Al	13	15	27.98191031(14)	2.2414(12) min	3+
²⁹Al	13	16	28.9804450(13)	6.56(6) min	5/2+
³⁰Al	13	17	29.982960(15)	3.60(6) s	3+
³¹Al	13	18	30.983947(22)	644(25) ms	(3/2,5/2)+
³²Al	13	19	31.98812(9)	31.7(8) ms	1+
^32mAl	955.7(4) keV			200(20) ns	(4+)
³³Al	13	20	32.99084(8)	41.7(2) ms	(5/2+)#
³⁴Al	13	21	33.99685(12)	56.3(5) ms	4-#
³⁵Al	13	22	34.99986(19)	38.6(4) ms	5/2+#
³⁶Al	13	23	36.00621(23)	90(40) ms
³⁷Al	13	24	37.01068(36)	10.7(13) ms
³⁸Al	13	25	38.01723(78)	7.6(6) ms
³⁹Al	13	26	39.02297(158)	7.6(16) ms	3/2+#
⁴⁰Al	13	27	40.03145(75)#	10# ms [>260 ns]
⁴¹Al	13	28	41.03833(86)#	2# ms [>260 ns]	3/2+#
⁴²Al	13	29	42.04689(97)#	1# ms

[edit] Notes

Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

[edit] References

Isotope masses from Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729 (2003).
Isotopic compositions and standard atomic masses from Atomic weights of the elements. Review 2000 (IUPAC Technical Report). Pure Appl. Chem. Vol. 75, No. 6, pp. 683-800, (2003) and Atomic Weights Revised (2005).
Audi, Bersillon, Blachot, Wapstra. The Nubase2003 evaluation of nuclear and decay properties, Nuc. Phys. A 729, pp. 3-128 (2003).
National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database (retrieved Sept. 2005).
David R. Lide (ed.), Norman E. Holden in CRC Handbook of Chemistry and Physics, 85th Edition, online version. CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.