Isotopes of iridium

Isotopes of iridium (₇₇Ir)

Main isotopes^[1]			Decay
	abundance	half-life (t_1/2)	mode	product
¹⁹¹Ir	37.3%	stable
¹⁹²Ir	synth	73.827 d	β⁻	¹⁹²Pt
¹⁹²Ir	synth	73.827 d	ε	¹⁹²Os
^192m2Ir	synth	241 y	IT	¹⁹²Ir
¹⁹³Ir	62.7%	stable

Standard atomic weight A_r°(Ir)

192.217±0.002^[2]
192.22±0.01 (abridged)^[3]

There are two natural isotopes of iridium (₇₇Ir), and 37 radioisotopes, the most stable radioisotope being ¹⁹²Ir with a half-life of 73.83 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 a year, 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]

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List of isotopes

Nuclide^[5] ^[n 1]	Z	N	Isotopic mass (Da)^[6] ^[n 2]^[n 3]	Half-life ^[n 4]	Decay mode ^[n 5]	Daughter isotope ^[n 6]^[n 7]	Spin and parity ^[n 8]^[n 4]	Natural abundance (mole fraction)
Nuclide^[5] ^[n 1]	Excitation energy^[n 4]			Half-life ^[n 4]	Decay mode ^[n 5]	Daughter isotope ^[n 6]^[n 7]	Spin and parity ^[n 8]^[n 4]	Normal proportion	Range of variation
¹⁶⁴Ir^[7]	77	87	163.99220(44)#	<0.5 µs	p?	¹⁶³Os	2−#
^164mIr	270(110)# keV			70(10) µs	p (96%)	¹⁶³Os	9+#
^164mIr	270(110)# keV			70(10) µs	α (4%)	^160mRe	9+#
¹⁶⁵Ir	77	88	164.98752(23)#	1.20+0.82 −0.74 μs^[8]	p	¹⁶⁴Os	(1/2+)
^165mIr^[9]	~255 keV			340(40) µs	p (88%)	¹⁶⁴Os	(11/2−)
^165mIr^[9]	~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	172(6) keV			15.1(9) ms	α (98.2%)	¹⁶²Re	(9+)
^166mIr	172(6) keV			15.1(9) ms	p (1.8%)	¹⁶⁵Os	(9+)
¹⁶⁷Ir	77	90	166.981665(20)	35.2(20) ms	α (48%)	¹⁶³Re	1/2+
					p (32%)	¹⁶⁶Os
					β⁺ (20%)	¹⁶⁷Os
^167mIr	175.3(22) keV			30.0(6) ms	α (80%)	¹⁶³Re	11/2−
					β⁺ (20%)	¹⁶⁷Os
					p (.4%)	¹⁶⁶Os
¹⁶⁸Ir	77	91	167.97988(16)#	161(21) ms	α	¹⁶⁴Re	(2-)
¹⁶⁸Ir	77	91	167.97988(16)#	161(21) ms	β⁺ (rare)	¹⁶⁸Os	(2-)
^168mIr	50(100)# keV			125(40) ms	α	¹⁶⁴Re	(9+)
¹⁶⁹Ir	77	92	168.976295(28)	780(360) ms [0.64(+46−24) s]	α	¹⁶⁵Re	(1/2+)
¹⁶⁹Ir	77	92	168.976295(28)	780(360) ms [0.64(+46−24) s]	β⁺ (rare)	¹⁶⁹Os	(1/2+)
^169mIr	154(24) keV			308(22) ms	α (72%)	¹⁶⁵Re	(11/2−)
^169mIr	154(24) keV			308(22) ms	β⁺ (28%)	¹⁶⁹Os	(11/2−)
¹⁷⁰Ir	77	93	169.97497(11)#	910(150) ms [0.87(+18−12) s]	β⁺ (64%)	¹⁷⁰Os	low#
¹⁷⁰Ir	77	93	169.97497(11)#	910(150) ms [0.87(+18−12) s]	α (36%)	¹⁶⁶Re	low#
^170mIr	160(50)# keV			440(60) ms	α (36%)	¹⁶⁶Re	(8+)
					β⁺	¹⁷⁰Os
					IT	¹⁷⁰Ir
¹⁷¹Ir	77	94	170.97163(4)	3.6(10) s [3.2(+13−7) s]	α (58%)	¹⁶⁷Re	1/2+
¹⁷¹Ir	77	94	170.97163(4)	3.6(10) s [3.2(+13−7) s]	β⁺ (42%)	¹⁷¹Os	1/2+
^171mIr	180(30)# keV			1.40(10) s			(11/2−)
¹⁷²Ir	77	95	171.970610(30)	4.4(3) s	β⁺ (98%)	¹⁷²Os	(3+)
¹⁷²Ir	77	95	171.970610(30)	4.4(3) s	α (2%)	¹⁶⁸Re	(3+)
^172mIr	280(100)# keV			2.0(1) s	β⁺ (77%)	¹⁷²Os	(7+)
^172mIr	280(100)# keV			2.0(1) s	α (23%)	¹⁶⁸Re	(7+)
¹⁷³Ir	77	96	172.967502(15)	9.0(8) s	β⁺ (93%)	¹⁷³Os	(3/2+,5/2+)
¹⁷³Ir	77	96	172.967502(15)	9.0(8) s	α (7%)	¹⁶⁹Re	(3/2+,5/2+)
^173mIr	253(27) keV			2.20(5) s	β⁺ (88%)	¹⁷³Os	(11/2−)
^173mIr	253(27) keV			2.20(5) s	α (12%)	¹⁶⁹Re	(11/2−)
¹⁷⁴Ir	77	97	173.966861(30)	7.9(6) s	β⁺ (99.5%)	¹⁷⁴Os	(3+)
¹⁷⁴Ir	77	97	173.966861(30)	7.9(6) s	α (.5%)	¹⁷⁰Re	(3+)
^174mIr	193(11) keV			4.9(3) s	β⁺ (99.53%)	¹⁷⁴Os	(7+)
^174mIr	193(11) keV			4.9(3) s	α (.47%)	¹⁷⁰Re	(7+)
¹⁷⁵Ir	77	98	174.964113(21)	9(2) s	β⁺ (99.15%)	¹⁷⁵Os	(5/2−)
¹⁷⁵Ir	77	98	174.964113(21)	9(2) s	α (.85%)	¹⁷¹Re	(5/2−)
¹⁷⁶Ir	77	99	175.963649(22)	8.3(6) s	β⁺ (97.9%)	¹⁷⁶Os
¹⁷⁶Ir	77	99	175.963649(22)	8.3(6) s	α (2.1%)	¹⁷²Re
¹⁷⁷Ir	77	100	176.961302(21)	30(2) s	β⁺ (99.94%)	¹⁷⁷Os	5/2−
¹⁷⁷Ir	77	100	176.961302(21)	30(2) s	α (.06%)	¹⁷³Re	5/2−
¹⁷⁸Ir	77	101	177.961082(21)	12(2) s	β⁺	¹⁷⁸Os
¹⁷⁹Ir	77	102	178.959122(12)	79(1) s	β⁺	¹⁷⁹Os	(5/2)−
¹⁸⁰Ir	77	103	179.959229(23)	1.5(1) min	β⁺	¹⁸⁰Os	(4,5)(+#)
¹⁸¹Ir	77	104	180.957625(28)	4.90(15) min	β⁺	¹⁸¹Os	(5/2)−
¹⁸²Ir	77	105	181.958076(23)	15(1) min	β⁺	¹⁸²Os	(3+)
¹⁸³Ir	77	106	182.956846(27)	57(4) min	β⁺ ( 99.95%)	¹⁸³Os	5/2−
¹⁸³Ir	77	106	182.956846(27)	57(4) min	α (.05%)	¹⁷⁹Re	5/2−
¹⁸⁴Ir	77	107	183.95748(3)	3.09(3) h	β⁺	¹⁸⁴Os	5−
^184m1Ir	225.65(11) keV			470(30) µs			3+
^184m2Ir	328.40(24) keV			350(90) ns			(7)+
¹⁸⁵Ir	77	108	184.95670(3)	14.4(1) h	β⁺	¹⁸⁵Os	5/2−
¹⁸⁶Ir	77	109	185.957946(18)	16.64(3) h	β⁺	¹⁸⁶Os	5+
^186mIr	0.8(4) keV			1.92(5) h	β⁺	¹⁸⁶Os	2−
^186mIr	0.8(4) keV			1.92(5) h	IT (rare)	¹⁸⁶Ir	2−
¹⁸⁷Ir	77	110	186.957363(7)	10.5(3) h	β⁺	¹⁸⁷Os	3/2+
^187m1Ir	186.15(4) keV			30.3(6) ms	IT	¹⁸⁷Ir	9/2−
^187m2Ir	433.81(9) keV			152(12) ns			11/2−
¹⁸⁸Ir	77	111	187.958853(8)	41.5(5) h	β⁺	¹⁸⁸Os	1−
^188mIr	970(30) keV			4.2(2) ms	IT	¹⁸⁸Ir	7+#
^188mIr	970(30) keV			4.2(2) ms	β⁺ (rare)	¹⁸⁸Os	7+#
¹⁸⁹Ir	77	112	188.958719(14)	13.2(1) d	EC	¹⁸⁹Os	3/2+
^189m1Ir	372.18(4) keV			13.3(3) ms	IT	¹⁸⁹Ir	11/2−
^189m2Ir	2333.3(4) keV			3.7(2) ms			(25/2)+
¹⁹⁰Ir	77	113	189.9605460(18)	11.78(10) d	EC	¹⁹⁰Os	4−
¹⁹⁰Ir	77	113	189.9605460(18)	11.78(10) d	β⁺ (<0.002%)^[1]	¹⁹⁰Os	4−
^190m1Ir	26.1(1) keV			1.120(3) h	IT	¹⁹⁰Ir	(1−)
^190m2Ir	36.154(25) keV			>2 µs			(4)+
^190m3Ir	376.4(1) keV			3.087(12) h			(11)−
¹⁹¹Ir	77	114	190.9605940(18)	Observationally Stable^[n 9]			3/2+	0.373(2)
^191m1Ir	171.24(5) keV			4.94(3) s	IT	¹⁹¹Ir	11/2−
^191m2Ir	2120(40) keV			5.5(7) s
¹⁹²Ir	77	115	191.9626050(18)	73.827(13) d	β⁻ (95.24%)	¹⁹²Pt	4+
¹⁹²Ir	77	115	191.9626050(18)	73.827(13) d	EC (4.76%)	¹⁹²Os	4+
^192m1Ir	56.720(5) keV			1.45(5) min	IT (98.25%)	¹⁹²Ir	1−
^192m1Ir	56.720(5) keV			1.45(5) min	β⁻ (1.75%)	¹⁹²Pt	1−
^192m2Ir	168.14(12) keV			241(9) y	IT	¹⁹²Ir	(11−)
¹⁹³Ir	77	116	192.9629264(18)	Observationally Stable^[n 10]			3/2+	0.627(2)
^193mIr	80.240(6) keV			10.53(4) d	IT	¹⁹³Ir	11/2−
¹⁹⁴Ir	77	117	193.9650784(18)	19.28(13) h	β⁻	¹⁹⁴Pt	1−
^194m1Ir	147.078(5) keV			31.85(24) ms	IT	¹⁹⁴Ir	(4+)
^194m2Ir	370(70) keV			171(11) d			(10,11)(−#)
¹⁹⁵Ir	77	118	194.9659796(18)	2.5(2) h	β⁻	¹⁹⁵Pt	3/2+
^195mIr	100(5) keV			3.8(2) h	β⁻ (95%)	¹⁹⁵Pt	11/2−
^195mIr	100(5) keV			3.8(2) h	IT (5%)	¹⁹⁵Ir	11/2−
¹⁹⁶Ir	77	119	195.96840(4)	52(1) s	β⁻	¹⁹⁶Pt	(0−)
^196mIr	210(40) keV			1.40(2) h	β⁻ (99.7%)	¹⁹⁶Pt	(10,11−)
^196mIr	210(40) keV			1.40(2) h	IT	¹⁹⁶Ir	(10,11−)
¹⁹⁷Ir	77	120	196.969653(22)	5.8(5) min	β⁻	¹⁹⁷Pt	3/2+
^197mIr	115(5) keV			8.9(3) min	β⁻ (99.75%)	¹⁹⁷Pt	11/2−
^197mIr	115(5) keV			8.9(3) min	IT (.25%)	¹⁹⁷Ir	11/2−
¹⁹⁸Ir	77	121	197.97228(21)#	8(1) s	β⁻	¹⁹⁸Pt
¹⁹⁹Ir	77	122	198.97380(4)	7(5) s	β⁻	¹⁹⁹Pt	3/2+#
^199mIr	130(40)# keV			235(90) ns	IT	¹⁹⁹Ir	11/2−#
²⁰⁰Ir	77	123	199.976800(210)#	43(6) s	β⁻	²⁰⁰Pt	(2-, 3-)
²⁰¹Ir	77	124	200.978640(210)#	21(5) s	β⁻	²⁰¹Pt	(3/2+)
²⁰²Ir	77	125	201.981990(320)#	11(3) s	β⁻	²⁰²Pt	(2-)
^202mIr	2000(1000)# keV			3.4(0.6) µs	IT	²⁰²Ir
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:

EC: Electron capture

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.
^ Believed to undergo α decay to ¹⁸⁷Re
^ Believed to undergo α decay to ¹⁸⁹Re

Iridium-192

Iridium-192 (symbol ¹⁹²Ir) is a radioactive isotope of iridium, with a half-life of 73.83 days.^[10] 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.^[11] Iridium-192 is normally produced by neutron activation of natural-abundance iridium metal.^[12]

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).^[13]^[14] 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 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.
^ 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. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
^ Wang, M.; Audi, G.; Kondev, F. G.; Huang, W. J.; Naimi, S.; Xu, X. (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.
^ 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.
^ 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.
^ "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.