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Nuclide reference

Ho-166m — Holmium-166m

The half-life of Ho-166m is 1,200 years. Main decay mode: β⁻ decay to Er-166 (100%).

Identification

Element
Holmium (Ho)
Atomic number Z
67
Mass number A
166
State
Radioactive

Key quantities

Half-life
1,200 years
Specific activity
6.64e+10 Bq/g
Gamma constant Γ
—
A1 / A2 for transport (SSR-6, НП-053-16)
0.6 TBq / 0.5 TBq
D-value (НП-067-24)
0.04 TBq

Decay modes

  • β⁻ decay → Er-166 — 100 %

Main gamma lines

Energy, keVYield, %
184.41172
810.29356.88
711.68154.14
280.46429.36
49.129 · X-ray line18.98
752.31312.1
80.57411.97
410.94911.2
48.223 · X-ray line9.963
529.8079.461

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

Alpha and beta particles

RadiationEnergy, keVYield, %
β⁻, E max73.673.9
33.01717.23
1,315.13.3
644.612.27

For β⁻ the endpoint (maximum) energy of the spectrum is given. ENDF/B-VIII.0.

Related calculators

DecayActivity ↔ massSource categoryDose rateA1/A2 and package type
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.

Holmium-166m (Ho-166m) — reference data

What is in the card

This card gathers the key data of radionuclide Ho-166m 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 Ho-166m 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.