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Nuclide reference

Hg-197m — Mercury-197m

The half-life of Hg-197m is 23.8 h. Main decay mode: isomeric transition to Hg-197 (91.4%).

Identification

Element
Mercury (Hg)
Atomic number Z
80
Mass number A
197
State
Radioactive

Key quantities

Half-life
23.8 h
Specific activity
2.473e+16 Bq/g
Gamma constant Γ
—
A1 / A2 for transport (SSR-6, НП-053-16)
10 TBq / 0.4 TBq
D-value (НП-067-24)
0.7 TBq

Decay modes

  • isomeric transition → Hg-197 — 91.4 %
  • electron capture → Au-197m — 8.6 %

Main gamma lines

Energy, keVYield, %
133.9833.9
70.819 · X-ray line16.4
9.97695 · X-ray line14.7
279.01 (Au-197m)6.098
164.970.2712
130.2 (Au-197m)0.2683
201.6 (Au-197m)0.09757
77.351 (Au-197m)0.02625

Includes daughter nuclides in equilibrium: Au-197m (yield per decay of Hg-197m); the emitting nuclide is in brackets. Equilibrium is reached in about 54 s.

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.

Mercury-197m (Hg-197m) — reference data

What is in the card

This card gathers the key data of radionuclide Hg-197m 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 Hg-197m 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.