Isotopes of iridium

There are two natural isotopes of iridium (₇₇Ir), and 34 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.

Main isotopes of iridium (₇₇Ir)

Iso­tope Decay abun­dance half-life (t1/2) mode pro­duct ^188Ir syn 1.73 d ε ^188Os ^189Ir syn 13.2 d ε ^189Os ^190Ir syn 11.8 d ε ^190Os ^191Ir 37.3% stable ^192Ir syn 73.827 d β^− ^192Pt ε ^192Os ^192m2Ir syn 241 y IT ^192Ir ^193Ir 62.7% stable ^193mIr syn 10.5 d IT ^193Ir ^194Ir syn 19.3 h β^− ^194Pt ^194m2Ir syn 171 d IT ^194Ir
Standard atomic weight Ar, standard(Ir)	192.217(3)[1]

List of isotopes

Nuclide[2] [n 1]	Z	N	Isotopic mass (Da)[3] [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	77	87	163.99220(44)#	1# ms			2−#
^164mIr	270(110)# keV			94(27) µs			9+#
^165Ir	77	88	164.98752(23)#	50# ns (<1 µs)	p	^164Os	1/2+#
					α (rare)	^161Re
^165mIr	180(50)# keV			300(60) µs	p (87%)	^164Os	11/2−
					α (13%)	^161Re
^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 [0.64(+46−24) s]	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 [0.87(+18−12) s]	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)	11.78(10) d	β^+	^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)	Stable			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			1−
^192m2Ir	168.14(12) keV			241(9) y			(11−)
^193Ir	77	116	192.9629264(18)	Stable			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

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.

Iridium-192

Iridium-192 (symbol ¹⁹²Ir) is a radioactive isotope of iridium, with a half-life of 73.83 days.[4] 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.[5] Iridium-192 is normally produced by neutron activation of natural-abundance iridium metal.[6]

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).[7][8] There are seven principal energy packets produced during its disintegration process ranging from just over 0.2 to about 0.6 MeV. Iridium-192 is commonly used as a gamma ray source in industrial radiography to locate flaws in metal components.[9] It is also used in radiotherapy as a radiation source, in particular in brachytherapy.

Iridium-192 has accounted for the majority of cases tracked by the U.S Nuclear Regulatory Commission in which radioactive materials have gone missing in quantities large enough to make a dirty bomb.[10]

References

1. Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
2. 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.
3. 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.
4. "Radioisotope Brief: Iridium-192 (Ir-192)". Retrieved 20 March 2012.
5. Braggerly, L. L. (1956). "The radioactive decay of Iridium-192 (Pd.D. Thesis)" (PDF). Pasadena, Calif.: California Institute of Technology: 1, 2, 7. Cite journal requires |journal= (help)
6. "Isotope Supplier: Stable Isotopes and Radioisotopes from ISOFLEX - Iridium-192". www.isoflex.com. Retrieved 2017-10-11.
7. Delacroix, D; Guerre, J P; Leblanc, P; Hickman, C (2002). Radionuclide and Radiation Protection Data Handbook (PDF). Radiation Protection Dosimetry. 98 (2nd ed.). Ashford, Kent: Nuclear Technology Publishing. pp. 9–168. doi:10.1093/OXFORDJOURNALS.RPD.A006705. ISBN 1870965876. PMID 11916063. S2CID 123447679.
8. 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.
9. Charles Hellier (2003). Handbook of Nondestructive Evaluation. McGraw-Hill. p. 6.20. ISBN 978-0-07-028121-9.
10. Steve Coll (March 12, 2007). "The Unthinkable". The New Yorker. Retrieved 2007-03-09.

• 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. Lay summary.
• 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)