Isotopes of sulfur
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Sulfur (16S) has 23 known isotopes with mass numbers ranging from 27 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-4 nuclei, in the so-called alpha process of exploding type II supernovas (see silicon burning).
34S abundances vary greatly (between 3.96 and 4.77 percent) in natural samples.
|Standard atomic weight Ar, standard(S)|
Other than 35S, the radioactive isotopes of sulfur 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 170 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-34 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.
List of isotopesEdit
|Z||N||Isotopic mass (u)
[n 2][n 3]
[n 6][n 7]
|Natural abundance (mole fraction)|
|Excitation energy||Normal proportion||Range of variation|
|27S[n 8]||16||11||27.01828(43)#||15.5(15) ms||β+ (96.6%)||27P||(5/2+)|
|β+, p (2.3%)||26Si|
|β+, 2p (1.1%)||25Al|
|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)||188(4) ms||β+ (53.6%)||29P||5/2+#|
|β+, p (46.4%)||28Si|
|35S||16||19||34.96903232(4)||87.37(4) d||β−||35Cl||3/2+||Trace[n 10]|
|41S||16||25||40.979593(4)||1.99(5) s||β− (>99.9%)||41Cl||7/2−#|
|β−, n (<.1%)||40Cl|
|42S||16||26||41.981065(3)||1.016(15) s||β− (>96%)||42Cl||0+|
|β−, n (<4%)||41Cl|
|43S||16||27||42.986908(5)||265(13) ms||β− (60%)||43Cl||3/2−#|
|β−, n (40%)||42Cl|
|43mS||319(5) keV||415.0(26) ns||(7/2−)|
|44S||16||28||43.990119(6)||100(1) ms||β− (81.7%)||44Cl||0+|
|β−, n (18.2%)||43Cl|
|44mS||1365.0(8) keV||2.619(26) µs||0+|
|45S||16||29||44.99572(111)||68(2) ms||β−, n (54%)||44Cl||3/2−#|
- mS – Excited nuclear isomer.
- ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
- # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
Modes of decay:
n: Neutron emission p: Proton emission
- Bold symbol as daughter – Daughter product is stable.
- ( ) spin value – Indicates spin with weak assignment arguments.
- # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
- Has 2 halo protons
- Heaviest theoretically stable nuclide with equal numbers of protons and neutrons
- 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.
- 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): 030001–1—030001–138, Bibcode:2017ChPhC..41c0001A, doi:10.1088/1674-1137/41/3/030001
- Wang, Meng; Audi, Georges; Kondev, Filip G.; Huang, Wen Jian; Naimi, Sarah; Xu, Xing (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
- Neufcourt, L.; Cao, Y.; Nazarewicz, W.; Olsen, E.; Viens, F. (2019). "Neutron drip line in the Ca region from Bayesian model averaging". Physical Review Letters. 122: 062502–1—062502–6. arXiv:1901.07632. doi:10.1103/PhysRevLett.122.062502.