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Nuclide reference

Ir-191m — Iridium-191m

The half-life of Ir-191m is 4.899 s. Main decay mode: isomeric transition to Ir-191 (100%).

Identification

Element
Iridium (Ir)
Atomic number Z
77
Mass number A
191
State
Radioactive

Key quantities

Half-life
4.899 s
Specific activity
4.461e+20 Bq/g
Gamma constant Γ
—
D-value (НП-067-24)
—

Decay modes

  • isomeric transition → Ir-191 — 100 %

Main gamma lines

Energy, keVYield, %
64.896 · X-ray line27.67
129.43126.5
10.7674 · X-ray line19.66
82.4270.031
41.8460.005885
47.050.0025

Lines of the bare nuclide (ENDF/B-VIII.0), without daughter ingrowth.

Related calculators

DecayActivity ↔ massDose rate

Other isotopes of this element

Ir-192
Reference data vs computed valuesHalf-life, gamma lines and D-value are reference data (ENDF/B-VIII.0, НП-067-24).Gamma constant Γ is H*(10) at 1 m computed from ICRP-107 spectra (NIST µ_en/ρ, ICRP-74 Table A.21) including short-lived progeny in equilibrium (e.g. Cs-137/Ba-137m, Ra-226 series); specific activity uses molar mass M ≈ mass number A.K-series X-ray energies are from NIST SRD 128 (Deslattes et al., 2003): in ENDF/B-VIII.0 they are given to 1 % and shifted by up to 0.7 keV for heavy elements. L-series lines and all yields are ENDF/B-VIII.0.

Iridium-191m (Ir-191m) — reference data

What is in the card

This card gathers the key data of radionuclide Ir-191m in one place: half-life, decay modes, main gamma lines, alpha and beta particle energies, gamma constant, specific activity and the D-value for source categorization. Decay and emission data are from ENDF/B-VIII.0; the D-value follows NP-067-24; the gamma constant is the ambient dose equivalent H*(10) at 1 m, computed from ICRP-107 spectra.

How to use the data

Half-life and specific activity let you recalculate the activity of a Ir-191m source to the delivery or disposal date — use the decay calculator. Gamma lines with yields identify the nuclide from a spectrum and pick the line for gamma spectrometry; the gamma constant Γ gives the dose rate at a distance, while the D-value and A1/A2 set the source category and the package type for transport.