Isotopes of arsenic

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Although arsenic (As) has multiple isotopes, only one of these isotopes is stable; as such, it is considered a monoisotopic element. Arsenic has been proposed as a "salting" material for nuclear weapons (cobalt is another, better-known salting material). A jacket of ⁷⁵As, irradiated by the intense high-energy neutron flux from an exploding thermonuclear weapon, would transmute into the radioactive isotope ⁷⁶As with a half-life of 1.0778 days and produce approximately 1.13 MeV of gamma radiation, significantly increasing the radioactivity of the weapon's fallout for several hours.^{[citation needed]} Such a weapon is not known to have ever been built, tested, or used.
Standard atomic mass: 74.92160(2) u.

[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)
⁶⁰As	33	27	59.99313(64)#		5+#
⁶¹As	56	28	60.98062(64)#		3/2-#
⁶²As	33	29	61.97320(32)#		1+#
⁶³As	33	30	62.96369(54)#		(3/2-)#
⁶⁴As	33	31	63.95757(38)#	40(30) ms [18(+43-7) ms]	0+#
⁶⁵As	33	32	64.94956(32)#	170(30) ms	3/2-#
⁶⁶As	33	33	65.94471(73)	95.77(23) ms	(0+)
^66m1As	1356.70(17) keV			1.1(1) µs	(5+)
^66m2As	3023.9(3) keV			8.2(5) µs	(9+)
⁶⁷As	33	34	66.93919(11)	42.5(12) s	(5/2-)
⁶⁸As	33	35	67.93677(5)	151.6(8) s	3+
^68mAs	425.21(16) keV			111(20) s [?107(+23-16) ns]	1+
⁶⁹As	33	36	68.93227(3)	15.2(2) min	5/2-
⁷⁰As	33	37	69.93092(5)	52.6(3) min	4(+#)
^70mAs	32.008(23) keV			96(3) µs	2(+)
⁷¹As	33	38	70.927112(5)	65.28(15) h	5/2-
⁷²As	33	39	71.926752(5)	26.0(1) h	2-
⁷³As	33	40	72.923825(4)	80.30(6) d	3/2-
⁷⁴As	33	41	73.9239287(25)	17.77(2) d	2-
⁷⁵As	33	42	74.9215965(20)	STABLE	3/2-	1.0000
^75mAs	303.9241(7) keV			17.62(23) ms	9/2+
⁷⁶As	33	43	75.922394(2)	1.0942(7) d	2-
^76mAs	44.425(1) keV			1.84(6) µs	(1)+
⁷⁷As	33	44	76.9206473(25)	38.83(5) h	3/2-
^77mAs	475.443(16) keV			114.0(25) µs	9/2+
⁷⁸As	33	45	77.921827(11)	90.7(2) min	2-
⁷⁹As	33	46	78.920948(6)	9.01(15) min	3/2-
^79mAs	772.81(6) keV			1.21(1) µs	(9/2)+
⁸⁰As	33	47	79.922534(25)	15.2(2) s	1+
⁸¹As	33	48	80.922132(6)	33.3(8) s	3/2-
⁸²As	33	49	81.92450(21)	19.1(5) s	(1+)
^82mAs	250(200) keV			13.6(4) s	(5-)
⁸³As	33	50	82.92498(24)	13.4(3) s	3/2-#
⁸⁴As	33	51	83.92906(32)#	4.02(3) s	(3)(+#)
^84mAs	0(100)# keV			650(150) ms
⁸⁵As	33	52	84.93202(21)#	2.021(10) s	(3/2-)#
⁸⁶As	33	53	85.93650(32)#	0.945(8) s
⁸⁷As	33	54	86.93990(32)#	0.56(8) s	3/2-#
⁸⁸As	33	55	87.94494(54)#	300# ms [>300 ns]
⁸⁹As	33	56	88.94939(54)#	200# ms [>300 ns]	3/2-#
⁹⁰As	33	57	89.95550(86)#	80# ms [>300 ns]
⁹¹As	33	58	90.96043(97)#	50# ms [>300 ns]	3/2-#
⁹²As	33	59	91.96680(97)#	30# ms [>300 ns]

[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).
Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.
- 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.