Isotopes of iridium

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]

Isotopes of iridium (₇₇Ir)

Main isotopes[1] Decay abun­dance half-life (t1/2) mode pro­duct 191Ir 37.3% stable 192Ir synth 73.827 d β− 192Pt ε 192Os 192m2Ir synth 241 y IT 192Ir 193Ir 62.7% stable
Standard atomic weight Ar°(Ir)
	192.217±0.002[2] 192.22±0.01 (abridged)[3]
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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)
	Excitation energy[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+#
					α (4%)	160mRe
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−)
					α (12%)	161mRe
166Ir	77	89	165.98582(22)#	10.5(22) ms	α (93%)	162Re	(2−)
					p (7%)	165Os
166mIr	172(6) keV			15.1(9) ms	α (98.2%)	162Re	(9+)
					p (1.8%)	165Os
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-)
					β+ (rare)	168Os
168mIr	50(100)# keV			125(40) ms	α	164Re	(9+)
169Ir	77	92	168.976295(28)	780(360) ms [640+460 −240 ms]	α	165Re	(1/2+)
					β+ (rare)	169Os
169mIr	154(24) keV			308(22) ms	α (72%)	165Re	(11/2−)
					β+ (28%)	169Os
170Ir	77	93	169.97497(11)#	910(150) ms [870+180 −120 ms]	β+ (64%)	170Os	low#
					α (36%)	166Re
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+
					β+ (42%)	171Os
171mIr	180(30)# keV			1.40(10) s			(11/2−)
172Ir	77	95	171.970610(30)	4.4(3) s	β+ (98%)	172Os	(3+)
					α (2%)	168Re
172mIr	280(100)# keV			2.0(1) s	β+ (77%)	172Os	(7+)
					α (23%)	168Re
173Ir	77	96	172.967502(15)	9.0(8) s	β+ (93%)	173Os	(3/2+,5/2+)
					α (7%)	169Re
173mIr	253(27) keV			2.20(5) s	β+ (88%)	173Os	(11/2−)
					α (12%)	169Re
174Ir	77	97	173.966861(30)	7.9(6) s	β+ (99.5%)	174Os	(3+)
					α (.5%)	170Re
174mIr	193(11) keV			4.9(3) s	β+ (99.53%)	174Os	(7+)
					α (.47%)	170Re
175Ir	77	98	174.964113(21)	9(2) s	β+ (99.15%)	175Os	(5/2−)
					α (.85%)	171Re
176Ir	77	99	175.963649(22)	8.3(6) s	β+ (97.9%)	176Os
					α (2.1%)	172Re
177Ir	77	100	176.961302(21)	30(2) s	β+ (99.94%)	177Os	5/2−
					α (.06%)	173Re
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−
					α (.05%)	179Re
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−
					IT (rare)	186Ir
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+#
					β+ (rare)	188Os
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)	11.7511(20) d[10]	EC	190Os	4−
					β+ (<0.002%)[10]
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	EC (91.4%)[10]	190Os	(11)−
					IT (8.6%)[10]	190Ir
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+
					EC (4.76%)	192Os
192m1Ir	56.720(5) keV			1.45(5) min	IT (98.25%)	192Ir	1−
					β− (1.75%)	192Pt
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−
					IT (5%)	195Ir
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−)
					IT	196Ir
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−
					IT (.25%)	197Ir
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

1. ^mIr – Excited nuclear isomer.
2. ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
3. # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
4. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
5. Modes of decay:

   EC:	Electron capture
   IT:	Isomeric transition
   p:	Proton emission

6. Bold italics symbol as daughter – Daughter product is nearly stable.
7. Bold symbol as daughter – Daughter product is stable.
8. ( ) spin value – Indicates spin with weak assignment arguments.
9. Believed to undergo α decay to ¹⁸⁷Re
10. Believed to undergo α decay to ¹⁸⁹Re

Iridium-192

Main article: 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

1. 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.
2. "Standard Atomic Weights: Iridium". CIAAW. 2017.
3. 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.
4. 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.
5. 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.
6. 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.
7. 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.
8. 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.
9. 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.
10. 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.
11. "Radioisotope Brief: Iridium-192 (Ir-192)". Retrieved 20 March 2012.
12. 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.
13. "Isotope Supplier: Stable Isotopes and Radioisotopes from ISOFLEX - Iridium-192". www.isoflex.com. Retrieved 2017-10-11.
14. 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.
15. 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.

• 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.

External links

• NLM Hazardous Substances Databank – Iridium, Radioactive (referring to iridium-192)