Isotopes of iridium

Isotopes of iridium (₇₇Ir)
ε	192Os
Standard atomic weight Ar°(Ir)
	192.217±0.002; 192.22±0.01 (abridged);
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There are two natural isotopes of iridium (₇₇Ir), and 37 radioisotopes, the most stable radioisotope being ¹⁹²Ir with a half-life of 73.82 days, and many nuclear isomers, the most stable of which is ^192m2Ir with a half-life of 241 years. All other isomers have half-lives under two weeks, most under a day. All isotopes of iridium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.^[4]

List of isotopes

Nuclide ^{[n 1]}	Z	N	Isotopic mass (Da)^[5] ^{[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 4]}	Natural abundance (mole fraction)
Nuclide ^{[n 1]}	Excitation energy^{[n 4]}			Half-life^[1] ^{[n 4]}	Decay mode^[1] ^{[n 5]}	Daughter isotope ^{[n 6]}^{[n 7]}	Spin and parity^[1] ^{[n 8]}^{[n 4]}	Normal proportion^[1]	Range of variation
¹⁶⁴Ir^{[n 9]}^[6]	77	87	163.99197(34)#	<0.5 μs	p?	¹⁶³Os	2−#
^164mIr	260(100)# keV			70(10) μs	p (96%)	¹⁶³Os	(9+)
^164mIr	260(100)# keV			70(10) μs	α (4%)	^160mRe	(9+)
¹⁶⁵Ir	77	88	165.98572(22)#	1.20+0.82 −0.74 μs^[7]	p	¹⁶⁴Os	(1/2+)
^165mIr^[6]	~255 keV			340(40) μs	p (88%)	¹⁶⁴Os	(11/2−)
^165mIr^[6]	~255 keV			340(40) μs	α (12%)	^161mRe	(11/2−)
¹⁶⁶Ir	77	89	165.98582(22)#	10.5(22) ms	α (93%)	¹⁶²Re	(2)−
¹⁶⁶Ir	77	89	165.98582(22)#	10.5(22) ms	p (7%)	¹⁶⁵Os	(2)−
^166mIr	171(6) keV			15.1(9) ms	α (98.2%)	¹⁶²Re	(9)+
^166mIr	171(6) keV			15.1(9) ms	p (1.8%)	¹⁶⁵Os	(9)+
¹⁶⁷Ir	77	90	166.981672(20)	29.3(6) ms	α (43.5%)	¹⁶³Re	1/2+
					p (38.6%)	¹⁶⁶Os
					β⁺ (17.9%)	¹⁶⁷Os
^167mIr	175.5(21) keV			28.5(5) ms	α (89%)	¹⁶³Re	11/2−
					β⁺ (11%)	¹⁶⁷Os
					p (0.41%)	¹⁶⁶Os
¹⁶⁸Ir	77	91	167.979961(59)	230(50) ms	α	¹⁶⁴Re	(2)-
^168mIr^{[n 10]}	40(250) keV			163(16) ms	α (77%)	¹⁶⁴Re	(9,10)+
					β⁺?	¹⁶⁸Os
					β⁺, p?	¹⁶⁷Re
¹⁶⁹Ir	77	92	168.976282(25)	353(4) ms	α (53%)	¹⁶⁵Re	(1/2+)
¹⁶⁹Ir	77	92	168.976282(25)	353(4) ms	β⁺ (47%)	¹⁶⁹Os	(1/2+)
^169mIr	153(22) keV			280(1) ms	α (79%)	¹⁶⁵Re	(11/2−)
					β⁺?	¹⁶⁹Os
					p?	¹⁶⁸Os
¹⁷⁰Ir	77	93	169.97511(11)#	910(150) ms	β⁺ (94.8%)	¹⁷⁰Os	(3−)
¹⁷⁰Ir	77	93	169.97511(11)#	910(150) ms	α (5.2%)	¹⁶⁶Re	(3−)
^170mIr^{[n 10]}	40(50)# keV			811(18) ms	α (38%)	¹⁶⁶Re	(8+)
					β⁺?	¹⁷⁰Os
					IT?	¹⁷⁰Ir
¹⁷¹Ir	77	94	170.971646(41)	3.1(3) s	β⁺ (85%)	¹⁷¹Os	1/2+
¹⁷¹Ir	77	94	170.971646(41)	3.1(3) s	α (15%)	¹⁶⁷Re	1/2+
^171mIr	164(11)# keV			1.47(6) s	α (54%)	¹⁶⁷Re	(11/2−)
					β⁺?	¹⁷¹Os
					p?	¹⁷⁰Os
¹⁷²Ir	77	95	171.970607(35)	4.4(3) s	β⁺ (~98%)	¹⁷²Os	(3−,4−)
¹⁷²Ir	77	95	171.970607(35)	4.4(3) s	α (~2%)	¹⁶⁸Re	(3−,4−)
^172mIr	139(10) keV			2.19(7) s	β⁺ (90.5%)	¹⁷²Os	(7+)
^172mIr	139(10) keV			2.19(7) s	α (9.5%)	¹⁶⁸Re	(7+)
¹⁷³Ir	77	96	172.967505(11)	9.0(8) s	β⁺ (96.5%)	¹⁷³Os	(1/2+,3/2+)
¹⁷³Ir	77	96	172.967505(11)	9.0(8) s	α (3.5%)	¹⁶⁹Re	(1/2+,3/2+)
^173mIr	226(9) keV			2.20(5) s	β⁺ (88%)	¹⁷³Os	11/2−
^173mIr	226(9) keV			2.20(5) s	α (12%)	¹⁶⁹Re	11/2−
¹⁷⁴Ir	77	97	173.966950(12)	7.9(6) s	β⁺ (99.5%)	¹⁷⁴Os	(2+,3−)
¹⁷⁴Ir	77	97	173.966950(12)	7.9(6) s	α (0.5%)	¹⁷⁰Re	(2+,3−)
^174mIr	124(16) keV			4.9(3) s	β⁺ (97.5%)	¹⁷⁴Os	(6,7,8,9)
^174mIr	124(16) keV			4.9(3) s	α (2.5%)	¹⁷⁰Re	(6,7,8,9)
¹⁷⁵Ir	77	98	174.964150(13)	9(2) s	β⁺ (99.15%)	¹⁷⁵Os	(1/2+)
¹⁷⁵Ir	77	98	174.964150(13)	9(2) s	α (0.85%)	¹⁷¹Re	(1/2+)
^175m1Ir	50(40)# keV			33(4) s	β⁺	¹⁷⁵Os	9/2−#
^175m2Ir	97.4(7) keV			6.58(15) μs	IT	¹⁷⁵Ir	(5/2−)
¹⁷⁶Ir	77	99	175.9636263(87)	8.7(5) s	β⁺ (96.9%)	¹⁷⁶Os	(3+)
¹⁷⁶Ir	77	99	175.9636263(87)	8.7(5) s	α (3.1%)	¹⁷²Re	(3+)
¹⁷⁷Ir	77	100	176.961302(21)	29.8(17) s	β⁺ (99.94%)	¹⁷⁷Os	5/2−
¹⁷⁷Ir	77	100	176.961302(21)	29.8(17) s	α (0.06%)	¹⁷³Re	5/2−
^177mIr	180.9(4) keV			>100 ns	IT	¹⁷⁷Ir	(5/2+)
¹⁷⁸Ir	77	101	177.961079(20)	12(2) s	β⁺	¹⁷⁸Os	3+#
¹⁷⁹Ir	77	102	178.959118(10)	79(1) s	β⁺	¹⁷⁹Os	(5/2)−
¹⁸⁰Ir	77	103	179.959229(23)	1.5(1) min	β⁺	¹⁸⁰Os	(5+)
¹⁸¹Ir	77	104	180.9576347(56)	4.90(15) min	β⁺	¹⁸¹Os	5/2−
^181m1Ir	289.33(13) keV			298 ns	IT	¹⁸¹Ir	5/2+
^181m2Ir	366.30(22) keV			126(6) ns	IT	¹⁸¹Ir	9/2−
¹⁸²Ir	77	105	181.958076(23)	15.0(10) min	β⁺	¹⁸²Os	3+
^182m1Ir	71.02(17) keV			170(40) ns	IT	¹⁸²Ir	(5)+
^182m2Ir	176.4(3) keV			130(50) ns	IT	¹⁸²Ir	(6−)
¹⁸³Ir	77	106	182.956841(26)	58(5) min	β⁺	¹⁸³Os	5/2−
¹⁸⁴Ir	77	107	183.957476(30)	3.09(3) h	β⁺	¹⁸⁴Os	5−
^184m1Ir	225.65(11) keV			470(30) μs	IT	¹⁸⁴Ir	3+
^184m2Ir	328.40(24) keV			350(90) ns	IT	¹⁸⁴Ir	7+
¹⁸⁵Ir	77	108	184.956698(30)	14.4(1) h	β⁺	¹⁸⁵Os	5/2−
^185mIr	2197(23) keV			120(20) ns	IT	¹⁸⁵Ir	(23/2,25/2)#
¹⁸⁶Ir	77	109	185.957947(18)	16.64(3) h	β⁺	¹⁸⁶Os	5+
^186mIr	0.8(4) keV			1.92(5) h	β⁺ (~75%)	¹⁸⁶Os	2−
^186mIr	0.8(4) keV			1.92(5) h	IT (~25%)	¹⁸⁶Ir	2−
¹⁸⁷Ir	77	110	186.957542(30)	10.5(3) h	β⁺	¹⁸⁷Os	3/2+
^187m1Ir	186.16(4) keV			30.3(6) ms	IT	¹⁸⁷Ir	9/2−
^187m2Ir	433.75(6) keV			152(12) ns	IT	¹⁸⁷Ir	11/2−
^187m3Ir	2487.7(4) keV			1.8(5) μs	IT	¹⁸⁷Ir	29/2−
¹⁸⁸Ir	77	111	187.958835(10)	41.5(5) h	β⁺	¹⁸⁸Os	1−
^188mIr	964(23) keV			4.15(15) ms	IT	¹⁸⁸Ir	11−#
¹⁸⁹Ir	77	112	188.958723(14)	13.2(1) d	EC	¹⁸⁹Os	3/2+
^189m1Ir	372.17(4) keV			13.3(3) ms	IT	¹⁸⁹Ir	11/2−
^189m2Ir	2332.8(3) keV			3.7(2) ms	IT	¹⁸⁹Ir	25/2+
¹⁹⁰Ir	77	113	189.9605434(15)	11.7511(20) d^[8]	EC	¹⁹⁰Os	4−
¹⁹⁰Ir	77	113	189.9605434(15)	11.7511(20) d^[8]	β⁺ (<0.002%)^[8]	¹⁹⁰Os	4−
^190m1Ir	26.1(1) keV			1.120(3) h	IT	¹⁹⁰Ir	1−
^190m2Ir	36.154(25) keV			>2 μs	IT	¹⁹⁰Ir	4+
^190m3Ir	376.4(1) keV			3.087(12) h	EC (91.4%)	¹⁹⁰Os	11−
^190m3Ir	376.4(1) keV			3.087(12) h	IT (8.6%)	¹⁹⁰Ir	11−
¹⁹¹Ir	77	114	190.9605915(14)	Observationally Stable^{[n 11]}			3/2+	0.373(2)
^191m1Ir	171.29(4) keV			4.899(23) s	IT	¹⁹¹Ir	11/2−
^191m2Ir	2101.0(9) keV			5.7(4) s	IT	¹⁹¹Ir	31/2(+)
¹⁹²Ir	77	115	191.9626024(14)	73.820(14) d	β⁻ (95.24%)	¹⁹²Pt	4+
¹⁹²Ir	77	115	191.9626024(14)	73.820(14) d	EC (4.76%)	¹⁹²Os	4+
^192m1Ir	56.720(5) keV			1.45(5) min	IT (99.98%)	¹⁹²Ir	1−
^192m1Ir	56.720(5) keV			1.45(5) min	β⁻ (0.0175%)	¹⁹²Pt	1−
^192m2Ir	168.14(12) keV			241(9) y	IT	¹⁹²Ir	(11−)
¹⁹³Ir	77	116	192.9629238(14)	Observationally Stable^{[n 12]}			3/2+	0.627(2)
^193m1Ir	80.238(6) keV			10.53(4) d	IT	¹⁹³Ir	11/2−
^193m2Ir	2278.9(5) keV			124.8(21) μs	IT	¹⁹³Ir	31/2+
¹⁹⁴Ir	77	117	193.9650757(14)	19.35(7) h	β⁻	¹⁹⁴Pt	1−
^194m1Ir	147.072(2) keV			31.85(24) ms	IT	¹⁹⁴Ir	4+
^194m2Ir	370(70) keV			171(11) d	β⁻	¹⁹⁴Pt	(11−)
¹⁹⁵Ir	77	118	194.9659769(14)	2.29(17) h	β⁻	¹⁹⁵Pt	3/2+
^195m1Ir	100(5) keV			3.74(7) h	β⁻	¹⁹⁵Pt	11/2−
^195m2Ir	2354(6) keV			4.4(6) μs	IT	¹⁹⁵Ir	(27/2+)
¹⁹⁶Ir	77	119	195.968400(41)	52.0(11) s	β⁻	¹⁹⁶Pt	(1,2−)
^196mIr	210(40) keV			1.40(2) h	β⁻	¹⁹⁶Pt	11−#
¹⁹⁷Ir	77	120	196.969657(22)	5.8(5) min	β⁻	¹⁹⁷Pt	3/2+
^197m1Ir	115(5) keV			8.9(3) min	β⁻	¹⁹⁷Pt	11/2−
^197m2Ir	1700(500)# keV			30(8) μs	IT	¹⁹⁷Ir
^197m3Ir	2800(500)# keV			15(9) μs	IT	¹⁹⁷Ir
¹⁹⁸Ir	77	121	197.97240(22)#	8.7(4) s	β⁻	¹⁹⁸Pt	1−
¹⁹⁹Ir	77	122	198.973807(44)	7(5) s	β⁻	¹⁹⁹Pt	3/2+#
²⁰⁰Ir	77	123	199.97684(21)#	43(6) s	β⁻	²⁰⁰Pt	(2−, 3−)
²⁰¹Ir	77	124	200.97870(22)#	21(5) s	β⁻	²⁰¹Pt	(3/2+)
²⁰²Ir	77	125	201.98214(32)#	11(3) s	β⁻	²⁰²Pt	(2−)
^202mIr	2600(300)# keV			3.4(6) μs	IT	²⁰²Ir
²⁰³Ir	77	126	202.98457(43)#	7# s [>300 ns]			3/2+#
^203mIr	2140(50)# keV			798(350) ns	IT	²⁰³Ir
²⁰⁴Ir	77	127	203.98973(43)#	2# s [>300 ns]			3/2+#
²⁰⁵Ir	77	128	204.99399(54)#	1# s [>300 ns]			3/2+#
This table header & footer: view

^ ^mIr – 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).
^ ^a ^b ^c # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
^ Modes of decay:

α: Alpha decay

β⁺: Positron emission

EC: Electron capture

β⁻: Beta decay

IT: Isomeric transition

p: Proton emission
^ Bold italics symbol as daughter – Daughter product is nearly stable.
^ Bold symbol as daughter – Daughter product is stable.
^ ( ) spin value – Indicates spin with weak assignment arguments.
^ Discovery of this isotope is unconfirmed
^ ^a ^b Order of ground state and isomer is uncertain.
^ Believed to undergo α decay to ¹⁸⁷Re^[9]^[10]
^ Believed to undergo α decay to ¹⁸⁹Re^[9]

Iridium-192

Iridium-192 (symbol ¹⁹²Ir) is a radioactive isotope of iridium, with a half-life of 73.83 days.^[11] It decays by emitting beta (β) particles and gamma (γ) radiation. About 96% of ¹⁹²Ir decays occur via emission of β and γ radiation, leading to ¹⁹²Pt. Some of the β particles are captured by other ¹⁹²Ir nuclei, which are then converted to ¹⁹²Os. Electron capture is responsible for the remaining 4% of ¹⁹²Ir decays.^[12] Iridium-192 is normally produced by neutron activation of natural-abundance iridium metal.^[13]

Iridium-192 is a very strong gamma ray emitter, with a gamma dose-constant of approximately 1.54 μSv·h⁻¹·MBq⁻¹ at 30 cm, and a specific activity of 341 TBq·g⁻¹ (9.22 kCi·g⁻¹).^[14]^[15] There are seven principal energy packets produced during its disintegration process ranging from just over 0.2 to about 0.6 MeV.

The ^192m2Ir isomer is unusual, both for its long half-life for an isomer, and that said half-life greatly exceeds that of the ground state of the same isotope.

References

^ ^a ^b ^c ^d ^e Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
^ "Standard Atomic Weights: Iridium". CIAAW. 2017.
^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
^ Belli, P.; Bernabei, R.; Danevich, F. A.; et al. (2019). "Experimental searches for rare alpha and beta decays". European Physical Journal A. 55 (8): 140–1–140–7. arXiv:1908.11458. Bibcode:2019EPJA...55..140B. doi:10.1140/epja/i2019-12823-2. ISSN 1434-601X. S2CID 201664098.
^ Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
^ ^a ^b Drummond, M. C.; O'Donnell, D.; Page, R. D.; Joss, D. T.; Capponi, L.; Cox, D. M.; Darby, I. G.; Donosa, L.; Filmer, F.; Grahn, T.; Greenlees, P. T.; Hauschild, K.; Herzan, A.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Lopez-Martens, A.; Mistry, A. K.; Nieminen, P.; Peura, P.; Rahkila, P.; Rinta-Antila, S.; Ruotsalainen, P.; Sandzelius, M.; Sarén, J.; Sayğı, B.; Scholey, C.; Simpson, J.; Sorri, J.; Thornthwaite, A.; Uusitalo, J. (16 June 2014). "α decay of the π h 11 / 2 isomer in Ir 164". Physical Review C. 89 (6): 064309. Bibcode:2014PhRvC..89f4309D. doi:10.1103/PhysRevC.89.064309. ISSN 0556-2813. Retrieved 21 June 2023.
^ Hilton, Joshua Ben. "Decays of new nuclides 169Au, 170Hg, 165Pt and the ground state of 165Ir discovered using MARA". University of Liverpool. ProQuest 2448649087. Retrieved 21 June 2023.
^ ^a ^b Janiak, Ł.; Gierlik, M.; Kosinski, T.; Matusiak, M.; Madejowski, G.; Wronka, S.; Rzadkiewicz, J. (2024). "Half-life of ¹⁹⁰Ir". Physical Review C. 110 (014306). doi:10.1103/PhysRevC.110.014306.
^ ^a ^b Danevich, F. A.; Andreotti, E.; Hult, M.; Marissens, G.; Tretyak, V. I.; Yuksel, A. (2012). "Search for α decay of ¹⁵¹Eu to the first excited level of ¹⁴⁷Pm using underground γ-ray spectrometry". European Physical Journal A. 48 (157): 157. arXiv:1301.3465. Bibcode:2012EPJA...48..157D. doi:10.1140/epja/i2012-12157-7. S2CID 118657922.
^ Belli, P.; Bernabei, R.; Danevich, F. A.; et al. (2019). "Experimental searches for rare alpha and beta decays". European Physical Journal A. 55 (8): 140–1–140–7. arXiv:1908.11458. Bibcode:2019EPJA...55..140B. doi:10.1140/epja/i2019-12823-2. ISSN 1434-601X. S2CID 201664098.
^ "Radioisotope Brief: Iridium-192 (Ir-192)". Retrieved 20 March 2012.
^ Baggerly, Leo L. (1956). The radioactive decay of Iridium-192 (PDF) (Ph.D. thesis). Pasadena, Calif.: California Institute of Technology. pp. 1, 2, 7. doi:10.7907/26VA-RB25.
^ "Isotope Supplier: Stable Isotopes and Radioisotopes from ISOFLEX - Iridium-192". www.isoflex.com. Retrieved 2017-10-11.
^ Delacroix, D; Guerre, J P; Leblanc, P; Hickman, C (2002). Radionuclide and Radiation Protection Data Handbook (PDF). Radiation Protection Dosimetry. Vol. 98, no. 1 (2nd ed.). Ashford, Kent: Nuclear Technology Publishing. pp. 9–168. doi:10.1093/OXFORDJOURNALS.RPD.A006705. ISBN 1870965876. PMID 11916063. S2CID 123447679. Archived from the original (PDF) on 2019-08-22.
^ Unger, L M; Trubey, D K (May 1982). Specific Gamma-Ray Dose Constants for Nuclides Important to Dosimetry and Radiological Assessment (PDF) (Report). Oak Ridge National Laboratory. Archived from the original (PDF) on 22 March 2018.