Isotopes of osmium

Isotopes of osmium (₇₆Os)
Standard atomic weight Ar°(Os)
	190.23±0.03; 190.23±0.03 (abridged);
	view; talk; edit;

Osmium (₇₆Os) has seven naturally occurring isotopes, five of which are stable: ¹⁸⁷Os, ¹⁸⁸Os, ¹⁸⁹Os, ¹⁹⁰Os, and (most abundant) ¹⁹²Os. The other natural isotopes, ¹⁸⁴Os, and ¹⁸⁶Os, have extremely long half-life (1.12×10¹³ years and 2×10¹⁵ years, respectively) and for practical purposes can be considered to be stable as well. ¹⁸⁷Os is the daughter of ¹⁸⁷Re (half-life 4.12×10¹⁰ years) and is most often measured in an ¹⁸⁷Os/¹⁸⁸Os ratio. This ratio, as well as the ¹⁸⁷Re/¹⁸⁸Os 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 Cretaceous–Paleogene boundary that marks the extinction of the dinosaurs 66 million years ago.

There are also 31 artificial radioisotopes,^[5] the longest-lived of which is ¹⁹⁴Os with a half-life of six years; all others have half-lives under 93 days. There are also ten known nuclear isomers, the longest-lived of which is ^191mOs with a half-life of 13.10 hours. All isotopes and nuclear isomers of osmium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.

Uses of osmium isotopes

The isotopic ratio of osmium-187 and osmium-188 (¹⁸⁷Os/¹⁸⁸Os) can be used as a window into geochemical changes throughout the ocean's history.^[6] The average marine ¹⁸⁷Os/¹⁸⁸Os ratio in oceans is 1.06.^[6] This value represents a balance of the continental derived riverine inputs of Os with a ¹⁸⁷Os/¹⁸⁸Os ratio of ~1.3, and the mantle/extraterrestrial inputs with a ¹⁸⁷Os/¹⁸⁸Os ratio of ~0.13.^[6] Being a descendant of ¹⁸⁷Re, ¹⁸⁷Os can be radiogenically formed by beta decay.^[7] This decay has actually pushed the ¹⁸⁷Os/¹⁸⁸Os ratio of the Bulk silicate earth (Earth minus the core) by 33%.^[8] This is what drives the difference in the ¹⁸⁷Os/¹⁸⁸Os ratio we see between continental materials and mantle material. Crustal rocks have a much higher level of Re, which slowly degrades into ¹⁸⁷Os driving up the ratio.^[7] Within the mantle however, the uneven response of Re and Os results in these mantle, and melted materials being depleted in Re, and do not allow for them to accumulate ¹⁸⁷Os like the continental material.^[7] The input of both materials in the marine environment results in the observed ¹⁸⁷Os/¹⁸⁸Os of the oceans and has fluctuated greatly over the history of our planet. These changes in the isotopic values of marine Os can be observed in the marine sediment that is deposited, and eventually lithified in that time period.^[9] This allows for researchers to make estimates on weathering fluxes, identifying flood basalt volcanism, and impact events that may have caused some of our largest mass extinctions. The marine sediment Os isotope record has been used to identify and corroborate the impact of the K-T boundary for example.^[10] The impact of this ~10 km asteroid massively altered the ¹⁸⁷Os/¹⁸⁸Os signature of marine sediments at that time. With the average extraterrestrial ¹⁸⁷Os/¹⁸⁸Os of ~0.13 and the huge amount of Os this impact contributed (equivalent to 600,000 years of present-day riverine inputs) lowered the global marine ¹⁸⁷Os/¹⁸⁸Os value of ~0.45 to ~0.2.^[6]

Os isotope ratios may also be used as a signal of anthropogenic impact.^[11] The same ¹⁸⁷Os/¹⁸⁸Os ratios that are common in geological settings may be used to gauge the addition of anthropogenic Os through things like catalytic converters.^[11] While catalytic converters have been shown to drastically reduce the emission of NO_x and CO₂, they are introducing platinum group elements (PGE) such as Os, to the environment.^[11] Other sources of anthropogenic Os include combustion of fossil fuels, smelting chromium ore, and smelting of some sulfide ores. In one study, the effect of automobile exhaust on the marine Os system was evaluated. Automobile exhaust ¹⁸⁷Os/¹⁸⁸Os has been recorded to be ~0.2 (similar to extraterrestrial and mantle derived inputs) which is heavily depleted (3, 7). The effect of anthropogenic Os can be seen best by comparing aquatic Os ratios and local sediments or deeper waters. Impacted surface waters tend to have depleted values compared to deep ocean and sediments beyond the limit of what is expected from cosmic inputs.^[11] This increase in effect is thought to be due to the introduction of anthropogenic airborne Os into precipitation.

The long half-life of ¹⁸⁴Os with respect to alpha decay to ¹⁸⁰W has been proposed as a radiometric dating method for osmium-rich rocks or for differentiation of a planetary core.^[2]^[12]^[13]

List of isotopes

Nuclide ^{[n 1]}	Z	N	Isotopic mass (Da)^[14] ^{[n 2]}^{[n 3]}	Half-life^[1] ^{[n 4]}	Decay mode^[1] ^{[n 5]}	Daughter isotope ^{[n 6]}^{[n 7]}	Spin and parity^[1] ^{[n 8]}^{[n 9]}	Natural abundance (mole fraction)
Nuclide ^{[n 1]}	Excitation energy			Half-life^[1] ^{[n 4]}	Decay mode^[1] ^{[n 5]}	Daughter isotope ^{[n 6]}^{[n 7]}	Spin and parity^[1] ^{[n 8]}^{[n 9]}	Normal proportion^[1]	Range of variation
¹⁶⁰Os^[15]	76	84		97+97 −32 μs	α	¹⁵⁶W	0+
^160mOs^[15]	1844(18) keV			41+15 −9 μs	α	¹⁵⁶W	8+
¹⁶¹Os	76	85	160.98905(43)#	0.64(6) ms	α	¹⁵⁷W	(7/2–)
¹⁶²Os	76	86	161.98443(32)#	2.1(1) ms	α	¹⁵⁸W	0+
¹⁶³Os	76	87	162.98246(32)#	5.7(5) ms	α	¹⁵⁹W	7/2–
¹⁶³Os	76	87	162.98246(32)#	5.7(5) ms	β⁺ ?	¹⁶³Re	7/2–
¹⁶⁴Os	76	88	163.97807(16)	21(1) ms	α (96%)	¹⁶⁰W	0+
¹⁶⁴Os	76	88	163.97807(16)	21(1) ms	β⁺ (4%)	¹⁶⁴Re	0+
¹⁶⁵Os	76	89	164.97665(22)#	71(3) ms	α (90%)	¹⁶¹W	(7/2–)
¹⁶⁵Os	76	89	164.97665(22)#	71(3) ms	β⁺ (10%)	¹⁶⁵Re	(7/2–)
¹⁶⁶Os	76	90	165.972698(19)	213(5) ms	α (83%)	¹⁶²W	0+
¹⁶⁶Os	76	90	165.972698(19)	213(5) ms	β⁺ (17%)	¹⁶⁶Re	0+
¹⁶⁷Os	76	91	166.971552(87)	839(5) ms	α (51%)	¹⁶³W	7/2–
¹⁶⁷Os	76	91	166.971552(87)	839(5) ms	β⁺ (49%)	¹⁶⁷Re	7/2–
^167mOs	434.3(11) keV			0.672(7) μs	IT	¹⁶⁷Os	13/2+
¹⁶⁸Os	76	92	167.967799(11)	2.1(1) s	β⁺ (57%)	¹⁶⁸Re	0+
¹⁶⁸Os	76	92	167.967799(11)	2.1(1) s	α (43%)	¹⁶⁴W	0+
¹⁶⁹Os	76	93	168.967018(28)	3.46(11) s	β⁺ (86.3%)	¹⁶⁹Re	(5/2–)
¹⁶⁹Os	76	93	168.967018(28)	3.46(11) s	α (13.7%)	¹⁶⁵W	(5/2–)
¹⁷⁰Os	76	94	169.963579(10)	7.37(18) s	β⁺ (90.5%)	¹⁷⁰Re	0+
¹⁷⁰Os	76	94	169.963579(10)	7.37(18) s	α (9.5%)	¹⁶⁶W	0+
¹⁷¹Os	76	95	170.963180(20)	8.3(2) s	β⁺ (98.20%)	¹⁷¹Re	(5/2−)
¹⁷¹Os	76	95	170.963180(20)	8.3(2) s	α (1.80%)	¹⁶⁷W	(5/2−)
¹⁷²Os	76	96	171.960017(14)	19.2(9) s	β⁺ (98.81%)	¹⁷²Re	0+
¹⁷²Os	76	96	171.960017(14)	19.2(9) s	α (1.19%)	¹⁶⁸W	0+
¹⁷³Os	76	97	172.959808(16)	22.4(9) s	β⁺ (99.6%)	¹⁷³Re	5/2–
¹⁷³Os	76	97	172.959808(16)	22.4(9) s	α (0.4%)	¹⁶⁹W	5/2–
¹⁷⁴Os	76	98	173.957063(11)	44(4) s	β⁺ (99.98%)	¹⁷⁴Re	0+
¹⁷⁴Os	76	98	173.957063(11)	44(4) s	α (.024%)	¹⁷⁰W	0+
¹⁷⁵Os	76	99	174.956945(13)	1.4(1) min	β⁺	¹⁷⁵Re	(5/2−)
¹⁷⁶Os	76	100	175.954770(12)	3.6(5) min	β⁺	¹⁷⁶Re	0+
¹⁷⁷Os	76	101	176.954958(16)	3.0(2) min	β⁺	¹⁷⁷Re	1/2−
¹⁷⁸Os	76	102	177.953253(15)	5.0(4) min	β⁺	¹⁷⁸Re	0+
¹⁷⁹Os	76	103	178.953816(17)	6.5(3) min	β⁺	¹⁷⁹Re	1/2–
^179m1Os	145.41(12) keV			~500 ns	IT	¹⁷⁹Os	(7/2)–
^179m2Os	243.0(8) keV			783(14) ns	IT	¹⁷⁹Os	(9/2)+
¹⁸⁰Os	76	104	179.952382(17)	21.5(4) min	β⁺	¹⁸⁰Re	0+
¹⁸¹Os	76	105	180.953247(27)	105(3) min	β⁺	¹⁸¹Re	1/2−
^181m1Os	49.20(14) keV			2.7(1) min	β⁺	¹⁸¹Re	7/2−
^181m2Os	156.91(15) keV			262(6) ns	IT	¹⁸¹Os	9/2+
¹⁸²Os	76	106	181.952110(23)	21.84(20) h	EC	¹⁸²Re	0+
^182m1Os	1831.4(3) keV			780(70) μs	IT	¹⁸²Os	8–
^182m2Os	7049.5(4) keV			150(10) ns	IT	¹⁸²Os	25+
¹⁸³Os	76	107	182.953125(53)	13.0(5) h	β⁺	¹⁸³Re	9/2+
^183mOs	170.73(7) keV			9.9(3) h	β⁺ (85%)	¹⁸³Re	1/2−
^183mOs	170.73(7) keV			9.9(3) h	IT (15%)	¹⁸³Os	1/2−
¹⁸⁴Os^{[n 10]}	76	108	183.95249292(89)	1.12(23)×10¹³ y	α^{[n 11]}	¹⁸⁰W	0+	2(2)×10⁻⁴
¹⁸⁵Os	76	109	184.95404597(89)	92.95(9) d	EC	¹⁸⁵Re	1/2−
^185m1Os	102.37(11) keV			3.0(4) μs	IT	¹⁸⁵Os	7/2−
^185m2Os	275.53(12) keV			0.78(5) μs	IT	¹⁸⁵Os	11/2+
¹⁸⁶Os^{[n 10]}	76	110	185.95383757(82)	2.0(11)×10¹⁵ y	α	¹⁸²W	0+	0.0159(64)
¹⁸⁷Os^{[n 12]}	76	111	186.95574957(79)	Observationally Stable^{[n 13]}			1/2−	0.0196(17)
^187m1Os	100.45(4) keV			112(6) ns	IT	¹⁸⁷Os	7/2−
^187m2Os	257.10(7) keV			231(2) μs	IT	¹⁸⁷Os	11/2+
¹⁸⁸Os^{[n 12]}	76	112	187.95583729(79)	Observationally Stable^{[n 14]}			0+	0.1324(27)
¹⁸⁹Os	76	113	188.95814595(72)	Observationally Stable^{[n 15]}			3/2−	0.1615(23)
^189mOs	30.82(2) keV			5.81(10) h	IT	¹⁸⁹Os	9/2−
^189mOs	30.82(2) keV			5.81(10) h	β⁻	¹⁸⁹Ir	9/2−
¹⁹⁰Os	76	114	189.95844544(70)	Observationally Stable^{[n 16]}			0+	0.2626(20)
^190mOs	1705.7(1) keV			9.86(3) min	IT	¹⁹⁰Os	10−
¹⁹¹Os	76	115	190.96092811(71)	14.99(2) d	β⁻	¹⁹¹Ir	9/2−
^191mOs	74.382(3) keV			13.10(5) h	IT	¹⁹¹Os	3/2−
¹⁹²Os	76	116	191.9614788(25)	Observationally Stable^{[n 17]}			0+	0.4078(32)
^192m1Os	2015.40(11) keV			5.94(9) s	IT	¹⁹²Os	10−
^192m1Os	2015.40(11) keV			5.94(9) s	β⁻?	¹⁹²Ir	10−
^192m2Os	4580.3(10) keV			205(7) ns	IT	¹⁹²Os	(20+)
¹⁹³Os	76	117	192.9641496(25)	29.830(18) h	β⁻	¹⁹³Ir	3/2−
^193mOs	315.6(3) keV			121(28) ns	IT	¹⁹²Os	(9/2−)
¹⁹⁴Os	76	118	193.9651794(26)	6.0(2) y	β⁻	¹⁹⁴Ir	0+
¹⁹⁵Os	76	119	194.968318(60)	6.5(11) min	β⁻	¹⁹⁵Ir	(3/2−)
^195mOs	427.8(3) keV			47(3) s	IT	¹⁹⁵Os	(13/2+)
^195mOs	427.8(3) keV			47(3) s	β⁻?	¹⁹⁵Ir	(13/2+)
¹⁹⁶Os	76	120	195.969643(43)	34.9(2) min	β⁻	¹⁹⁶Ir	0+
¹⁹⁷Os	76	121	196.97308(22)#	93(7) s	β⁻	¹⁹⁷Ir	5/2−#
¹⁹⁸Os	76	122	197.97466(22)#	125(28) s	β⁻	¹⁹⁸Ir	0+
¹⁹⁹Os	76	123	198.97824(22)#	6(3) s	β⁻	¹⁹⁹Ir	5/2−#
²⁰⁰Os	76	124	199.98009(32)#	7(4) s	β⁻	²⁰⁰Ir	0+
²⁰¹Os	76	125	200.98407(32)#	3# s [>300ns]	β⁻?	²⁰¹Ir	1/2−#
²⁰²Os	76	126	201.98655(43)#	2# s [>300ns]	β⁻?	²⁰²Ir	0+
²⁰³Os	76	127	202.99220(43)#	300# ms [>300ns]	β⁻?	²⁰³Ir	9/2+#
²⁰³Os	76	127	202.99220(43)#	300# ms [>300ns]	β⁻ n?	²⁰²Ir	9/2+#
This table header & footer: view

References

Isotope masses from:
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", 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:
- de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
- Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051.
"News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
Half-life, spin, and isomer data selected from the following sources.
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
- National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
- Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]

[12]

[13]

[n 1]

[14]

[n 2]

[n 3]

[n 4]

[n 5]

[n 6]

[n 7]

[n 8]

[n 9]

[15]

[n 10]

[n 11]

[n 12]

[n 13]

[n 14]

[n 15]

[n 16]

[n 17]