Nuclide reference
Sn-121m — Tin-121m
The half-life of Sn-121m is 43.9 years. Main decay mode: isomeric transition to Sn-121 (77.6%).
Identification
- Element
- Tin (Sn)
- Atomic number Z
- 50
- Mass number A
- 121
- State
- Radioactive
Key quantities
- Half-life
- 43.9 years
- Specific activity
- 2.49e+12 Bq/g
- Gamma constant Γ
- —
- A1 / A2 for transport (SSR-6, НП-053-16)
- 40 TBq / 0.9 TBq
- D-value (НП-067-24)
- 70 TBq
Decay modes
- isomeric transition → Sn-121 — 77.6 %
- β⁻ decay → Sb-121 — 22.4 %
Main gamma lines
| Energy, keV | Yield, % |
|---|---|
| 26.359 · X-ray line | 8.086 |
| 26.111 · X-ray line | 4.331 |
| 37.15 | 1.85 |
Lines of the nuclide itself (ENDF/B-VIII.0).
Alpha and beta particles
| Radiation | Energy, keV | Yield, % |
|---|---|---|
| β⁻, E max | 359.75 | 22.4 |
| 390.6 (Sn-121) | 77.61 |
For β⁻ the endpoint (maximum) energy of the spectrum is given. ENDF/B-VIII.0. Includes daughter nuclides in equilibrium: Sn-121 (yield per decay of Sn-121m); the emitting nuclide is in brackets. Equilibrium is reached in about 7.9 d.
Related calculators
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.