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 [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)
	Excitation energy[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+)
					α (4%)	160mRe
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−)
					α (12%)	161mRe
166Ir	77	89	165.98582(22)#	10.5(22) ms	α (93%)	162Re	(2)−
					p (7%)	165Os
166mIr	171(6) keV			15.1(9) ms	α (98.2%)	162Re	(9)+
					p (1.8%)	165Os
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+)
					β+ (47%)	169Os
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−)
					α (5.2%)	166Re
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+
					α (15%)	167Re
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−)
					α (~2%)	168Re
172mIr	139(10) keV			2.19(7) s	β+ (90.5%)	172Os	(7+)
					α (9.5%)	168Re
173Ir	77	96	172.967505(11)	9.0(8) s	β+ (96.5%)	173Os	(1/2+,3/2+)
					α (3.5%)	169Re
173mIr	226(9) keV			2.20(5) s	β+ (88%)	173Os	11/2−
					α (12%)	169Re
174Ir	77	97	173.966950(12)	7.9(6) s	β+ (99.5%)	174Os	(2+,3−)
					α (0.5%)	170Re
174mIr	124(16) keV			4.9(3) s	β+ (97.5%)	174Os	(6,7,8,9)
					α (2.5%)	170Re
175Ir	77	98	174.964150(13)	9(2) s	β+ (99.15%)	175Os	(1/2+)
					α (0.85%)	171Re
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+)
					α (3.1%)	172Re
177Ir	77	100	176.961302(21)	29.8(17) s	β+ (99.94%)	177Os	5/2−
					α (0.06%)	173Re
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−
					IT (~25%)	186Ir
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−
					β+ (<0.002%)[8]
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−
					IT (8.6%)	190Ir
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+
					EC (4.76%)	192Os
192m1Ir	56.720(5) keV			1.45(5) min	IT (99.98%)	192Ir	1−
					β− (0.0175%)	192Pt
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

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:

   α:	Alpha decay
   β+:	Positron emission
   EC:	Electron capture
   β−:	Beta decay
   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. Discovery of this isotope is unconfirmed
10. Order of ground state and isomer is uncertain.
11. Believed to undergo α decay to ¹⁸⁷Re^[9][10]
12. Believed to undergo α decay to ¹⁸⁹Re^[9]

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.