Isotopes of iridium

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

Relative atomic mass: 192.217(3).

Iridium-192

Iridium-192 (symbol ¹⁹²Ir) is a radioactive isotope of iridium, with a half-life of 73.83 days.^[1] 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.^[2]

Iridium-192 is also a strong gamma ray emitter. 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.^[3] 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.^[4]

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)[5][n 1]	daughter isotope(s)[n 2]	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
	excitation energy
^164Ir	77	87	163.99220(44)#	1# ms			2−#
^164mIr	270(110)# keV			94(27) µs			9+#
^165Ir	77	88	164.98752(23)#	<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	high
					β^+ (rare)	^168Os
^168mIr	50(100)# keV			125(40) ms	α	^164Re	low
^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	270(70)# keV			440(60) ms			high#
^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	171.97046(11)#	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)	Observationally Stable[n 3]			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)	Observationally Stable[n 4]			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)	20# s	β^−	^199Pt	3/2+#

1. Abbreviations:
   EC: Electron capture
   IT: Isomeric transition
2. Bold for stable isotopes, bold italics for nearly-stable isotopes (half-life longer than the age of the universe)
3. Believed to undergo α decay to ¹⁸⁷Re
4. Believed to undergo α decay to ¹⁸⁹Re

Notes

• Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
• Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC, which use expanded uncertainties.

References

1. "Radioisotope Brief: Iridium-192 (Ir-192)". Retrieved 20 March 2012.
2. Braggerly, L. L. (1956). "The radioactive decay of Iridium-192 (Pd.D. Thesis)" (PDF). Pasadena, Calif.: California Institute of Technology: 1, 2, 7.
3. Charles Hellier (2003). Handbook of Nondestructive Evaluation. McGraw-Hill. p. 6.20. ISBN 0-07-028121-1.
4. Steve Coll (March 12, 2007). "The Unthinkable". The New Yorker. Retrieved 2007-03-09.
5. "Universal Nuclide Chart". nucleonica. (registration required (help)).

• Isotope masses from:
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). 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:
  • J. R. de Laeter; J. K. Böhlke; P. De Bièvre; H. Hidaka; H. S. Peiser; K. J. R. Rosman; P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry 75 (6): 683–800. doi:10.1351/pac200375060683.
  • M. E. Wieser (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. See editing notes on this article's talk page.
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
  • National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005.
  • N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.

External links

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