Isotopes of sulfur

Sulfur (S) has 25 known isotopes with mass numbers ranging from 26 to 49, four of which are stable: ³²S (95.02%), ³³S (0.75%), ³⁴S (4.21%), and ³⁶S (0.02%). The preponderance of sulfur-32 is explained by its production from carbon-12 plus successive fusion capture of five helium nuclei, in the so-called alpha process of exploding type II supernovae (see silicon burning).

Other than ³⁵S, the radioactive isotopes of sulphur are all comparatively short-lived. ³⁵S is formed from cosmic ray spallation of ⁴⁰Ar in the atmosphere. It has a half-life of 87 days. The next longest-lived radioisotope is sulfur-38, with a half-life of 17 minutes. The shortest-lived is ⁴⁹S, with a half-life shorter than 200 nanoseconds.

When sulfide minerals are precipitated, isotopic equilibration among solids and liquid may cause small differences in the δS-64 values of co-genetic minerals. The differences between minerals can be used to estimate the temperature of equilibration. The δC-13 and δS-34 of coexisting carbonates and sulfides can be used to determine the pH and oxygen fugacity of the ore-bearing fluid during ore formation.

In most forest ecosystems, sulfate is derived mostly from the atmosphere; weathering of ore minerals and evaporites also contribute some sulfur. Sulfur with a distinctive isotopic composition has been used to identify pollution sources, and enriched sulfur has been added as a tracer in hydrologic studies. Differences in the natural abundances can also be used in systems where there is sufficient variation in the ³⁴S of ecosystem components. Rocky Mountain lakes thought to be dominated by atmospheric sources of sulfate have been found to have different δS-34 values from oceans believed to be dominated by watershed sources of sulfate.

Relative atomic mass: 32.065(5)

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)[1]	daughter isotope(s)[n 1]	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
	excitation energy
^26S	16	10	26.02788(32)#	10# ms	2p	^24Si	0+
^27S[n 2]	16	11	27.01883(22)#	15.5(15) ms	β^+ (98.0%)	^27P	(5/2+)
					β^+, 2p (2.0%)	^25Al
					β^+, p (<.1%)	^26Si
^28S	16	12	28.00437(17)	125(10) ms	β^+ (79.3%)	^28P	0+
					β^+, p (20.7%)	^27Si
^29S	16	13	28.99661(5)	187(4) ms	β^+ (53.6%)	^29P	5/2+
					β^+, p (46.4%)	^28Si
^30S	16	14	29.984903(3)	1.178(5) s	β^+	^30P	0+
^31S	16	15	30.9795547(16)	2.572(13) s	β^+	^31P	1/2+
^32S[n 3]	16	16	31.97207100(15)	Stable			0+	0.9493(31)	0.94454-0.95281
^33S	16	17	32.97145876(15)	Stable			3/2+	0.0076(2)	0.00730-0.00793
^34S	16	18	33.96786690(12)	Stable			0+	0.0429(28)	0.03976-0.04734
^35S	16	19	34.96903216(11)	87.51(12) d	β^−	^35Cl	3/2+	Trace[n 4]
^36S	16	20	35.96708076(20)	Stable			0+	2(1)×10^−4	1.3×10^−4-2.7×10^−4
^37S	16	21	36.97112557(21)	5.05(2) min	β^−	^37Cl	7/2−
^38S	16	22	37.971163(8)	170.3(7) min	β^−	^38Cl	0+
^39S	16	23	38.97513(5)	11.5(5) s	β^−	^39Cl	(3/2,5/2,7/2)−
^40S	16	24	39.97545(15)	8.8(22) s	β^−	^40Cl	0+
^41S	16	25	40.97958(13)	1.99(5) s	β^− (>99.9%)	^41Cl	(7/2−)#
					β^−, n (<.1%)	^40Cl
^42S	16	26	41.98102(13)	1.013(15) s	β^− (96%)	^42Cl	0+
					β^−, n (4%)	^41Cl
^43S	16	27	42.98715(22)	260(15) ms	β^− (60%)	^43Cl	3/2−#
					β^−, n (40%)	^42Cl
^43mS	319(5) keV			480(50) ns			(7/2−)
^44S	16	28	43.99021(42)	100(1) ms	β^− (82%)	^44Cl	0+
					β^−, n (18%)	^43Cl
^45S	16	29	44.99651(187)	68(2) ms	β^−, n (54%)	^44Cl	3/2−#
					β^− (46%)	^45Cl
^46S	16	30	46.00075(75)#	50(8) ms	β^−	^46Cl	0+
^47S	16	31	47.00859(86)#	20# ms [>200 ns]	β^−	^47Cl	3/2−#
^48S	16	32	48.01417(97)#	10# ms [>200 ns]	β^−	^48Cl	0+
^49S	16	33	49.02362(102)#	<200 ns	n	^48S	3/2−#

1. Bold for stable isotopes
2. Has 2 halo protons
3. Heaviest theoretically stable nuclide with equal numbers of protons and neutrons
4. Cosmogenic

Facts

• The precision of the isotope abundances and atomic mass is limited through variations. The given ranges should be applicable to any normal terrestrial material.
• 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.
• Abundance updated from Nubase data.

References

• Isotope masses from:
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
• Isotopic compositions and standard atomic masses from:
  • J. R. de Laeter; J. K. Böhlke; P. De Bièvre; H. Hidaka; H. S. Peiser; K. J. R. Rosman; P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry 75 (6): 683–800. doi:10.1351/pac200375060683.
  • M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry 78 (11): 2051–2066. doi:10.1351/pac200678112051. Lay summary.
• Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
  • National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005.
  • N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.

1. "Universal Nuclide Chart". nucleonica. (registration required (help)).

External links

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