Iridium-190

Properties and data of the isotope ¹⁹⁰Ir.

Contents

Iridium-190 is a radioisotope of the chemical element iridium, which has 113 neutrons in its atomic nucleus in addition to the element-specific 77 protons, resulting in a mass number of 190. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ¹⁹⁰Ir is exclusively for academic purposes.

Reactions to generate the ¹⁹⁰Ir nuclide include

- ¹⁹²Os(p,3n)¹⁹⁰Ir and

- ¹⁹²Os(d,4n)¹⁹⁰Ir

using radiation with 18–31 MeV protons (p) and 27.8 MeV deuterons (d) respectively [1].

General data

Name of the isotope:Iridium-190; Ir-190Symbol:¹⁹⁰Ir or 19077IrMass number A:190 (= number of nucleons)Atomic number Z:77 (= number of protons)Neutrons N:113Isotopic mass:189.9605434(15) u (atomic weight of Iridium-190)Nuclide mass:189.9183072 u (calculated nuclear mass without electrons)Mass excess:-36.75359 MeVMass defect:1.621119572 u (per nucleus)Nuclear binding energy:1510.0631546 MeV (per nucleus)
7.94770081 MeV (average binding energy per nucleon)Separation energy:S_N = 6.375(13) MeV (first neutron)
S_P = 5.0558(12) MeV (first proton)Half-life:11.7511(20) dDecay constant λ:6.827051775609 × 10^-7 s^-1Specific activity α:2.175315738137 × 10⁺¹⁵ Bq g^-1
58792.317246962 Ci g^-1Spin and parity:
(nuclear angular momentum)4-Magnetic dipole moment:μ(μ_N) = 0.04(1)Quadrupole moment Q:+ 2.85(14) barn (100 fm²)Nuclear g-factor:g_l = 0.01Year of discovery:1947

Radioactive Decay

The half-life value of ¹⁹⁰Ir used here was re-determined and published in 2024 [1]; until then, t_1/2 was given as 11.78(10) days.

Half-life T_½ = 11.7511(20) d respectively 1.01529504 × 10⁶ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC	¹⁹⁰Os	> 99.99 %	1.9542(15) MeV
β⁺	¹⁹⁰Os	< 0.002 %

Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear Isomer	Excitation Energy	Half-life	Spin
^190m1Ir	26.1(1) keV	1.120(3) h	(1-)
^190m2Ir	376.4(1) keV	3.087(12) h	(11)-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 113) and isobaric (same nucleon number A = 190) with Iridium-190. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 113	Isobar A = 190
70	¹⁸³Yb
71	¹⁸⁴Lu
72	¹⁸⁵Hf	¹⁹⁰Hf
73	¹⁸⁶Ta	¹⁹⁰Ta
74	¹⁸⁷W	¹⁹⁰W
75	¹⁸⁸Re	¹⁹⁰Re
76	¹⁸⁹Os	¹⁹⁰Os
77	¹⁹⁰Ir	¹⁹⁰Ir
78	¹⁹¹Pt	¹⁹⁰Pt
79	¹⁹²Au	¹⁹⁰Au
80	¹⁹³Hg	¹⁹⁰Hg
81	¹⁹⁴Tl	¹⁹⁰Tl
82	¹⁹⁵Pb	¹⁹⁰Pb
83	¹⁹⁶Bi	¹⁹⁰Bi
84	¹⁹⁷Po	¹⁹⁰Po
85	¹⁹⁸At	¹⁹⁰At
86	¹⁹⁹Rn
87	²⁰⁰Fr
88	²⁰¹Ra