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Isotopes of osmium



Osmium (Os) has seven naturally-occurring isotopes, 5 of which are stable: 187Os, 188Os, 189Os, 190Os, and (most abundant) 192Os. The other two, 184Os and 186Os, have enormously long half-lives and for practical purposes can be considered to be stable as well. 187Os is the daughter of 187Re (half-life 4.56 x 1010 years) and is most often measured in an 187Os/188Os ratio. This ratio, as well as the 187Re/187Os ratio, have been used extensively in dating terrestrial as well as meteoric rocks. It has also been used to measure the intensity of continental weathering over geologic time and to fix minimum ages for stabilization of the mantle roots of continental cratons. However, the most notable application of Os in dating has been in conjunction with iridium, to analyze the layer of shocked quartz along the K-T boundary that marks the extinction of the dinosaurs 65 million years ago.
Standard atomic mass: 190.23(3) u

Additional recommended knowledge

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)
excitation energy
162Os 76 86 161.98443(54)# 1.87(18) ms 0+
163Os 76 87 162.98269(43)# 5.5(6) ms 7/2-#
164Os 76 88 163.97804(22) 21(1) ms 0+
165Os 76 89 164.97676(22)# 71(3) ms (7/2-)
166Os 76 90 165.972691(20) 216(9) ms 0+
167Os 76 91 166.97155(8) 810(60) ms 3/2-#
168Os 76 92 167.967804(13) 2.06(6) s 0+
169Os 76 93 168.967019(27) 3.40(9) s 3/2-#
170Os 76 94 169.963577(12) 7.46(23) s 0+
171Os 76 95 170.963185(20) 8.3(2) s (5/2-)
172Os 76 96 171.960023(16) 19.2(5) s 0+
173Os 76 97 172.959808(16) 22.4(9) s (5/2-)
174Os 76 98 173.957062(12) 44(4) s 0+
175Os 76 99 174.956946(15) 1.4(1) min (5/2-)
176Os 76 100 175.95481(3) 3.6(5) min 0+
177Os 76 101 176.954965(17) 3.0(2) min 1/2-
178Os 76 102 177.953251(18) 5.0(4) min 0+
179Os 76 103 178.953816(19) 6.5(3) min (1/2-)
180Os 76 104 179.952379(22) 21.5(4) min 0+
181Os 76 105 180.95324(3) 105(3) min 1/2-
181m1Os 48.9(2) keV 2.7(1) min (7/2)-
181m2Os 156.5(7) keV 316(18) ns (9/2)+
182Os 76 106 181.952110(23) 22.10(25) h 0+
183Os 76 107 182.95313(5) 13.0(5) h 9/2+
183mOs 170.71(5) keV 9.9(3) h 1/2-
184Os 76 108 183.9524891(14) STABLE [>56E+12 a] 0+ 0.0002(1)
185Os 76 109 184.9540423(14) 93.6(5) d 1/2-
185m1Os 102.3(7) keV 3.0(4) µs (7/2-)#
185m2Os 275.7(8) keV 0.78(5) µs (11/2+)
186Os 76 110 185.9538382(15) 2.0(11)E+15 a 0+ 0.0159(3)
187Os 76 111 186.9557505(15) STABLE 1/2- 0.0196(2)
188Os 76 112 187.9558382(15) STABLE 0+ 0.1324(8)
189Os 76 113 188.9581475(16) STABLE 3/2- 0.1615(5)
189mOs 30.812(15) keV 5.81(6) h 9/2-
190Os 76 114 189.9584470(16) STABLE 0+ 0.2626(2)
190mOs 1705.4(2) keV 9.9(1) min (10)-
191Os 76 115 190.9609297(16) 15.4(1) d 9/2-
191mOs 74.382(3) keV 13.10(5) h 3/2-
192Os 76 116 191.9614807(27) STABLE [>9.8E+12 a] 0+ 0.4078(19)
192mOs 2015.40(11) keV 5.9(1) s (10-)
193Os 76 117 192.9641516(27) 30.11(1) h 3/2-
194Os 76 118 193.9651821(28) 6.0(2) a 0+
195Os 76 119 194.96813(54) 6.5 min 3/2-#
196Os 76 120 195.96964(4) 34.9(2) min 0+
197Os 76 121 2.8(6) min

Notes

  • Evaluated isotopic composition is for most but not all commercial samples.
  • The precision of the isotope abundances and atomic mass is limited through variations. The given ranges should be applicable to any normal terrestrial material.
  • Geologically exceptional samples are known in which the isotopic composition lies outside the reported range. The uncertainty in the atomic mass may exceed the stated value for such specimens.
  • 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.

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.


Isotopes of rhenium Isotopes of osmium Isotopes of iridium
Index to isotope pages
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Isotopes_of_osmium". A list of authors is available in Wikipedia.
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