Nuclide reference
Am-242m — Americium-242m
The half-life of Am-242m is 141 years. Main decay mode: isomeric transition to Am-242 (99.54%).
Identification
- Element
- Americium (Am)
- Atomic number Z
- 95
- Mass number A
- 242
- State
- Radioactive
Key quantities
- Half-life
- 141 years
- Specific activity
- 3.876e+11 Bq/g
- Gamma constant Γ
- —
- A1 / A2 for transport (SSR-6, НП-053-16)
- 10 TBq / 0.001 TBq
- D-value (НП-067-24)
- 0.3 TBq
Decay modes
Main gamma lines
| Energy, keV | Yield, % |
|---|---|
| 18.6806 · X-ray line | 12.85 |
| 14.6137 · X-ray line | 11.37 |
| 49.35 | 0.1336 |
| 984.45 (Np-238) | 0.1156 |
| 1,028.54 (Np-238) | 0.08395 |
| 1,025.87 (Np-238) | 0.04001 |
| 42.13 (Am-242) | 0.03917 |
| 44.08 (Cm-242) | 0.02721 |
| 86.65 | 0.02281 |
| 109.59 | 0.01974 |
Includes daughter nuclides in equilibrium: Am-242, Cm-242, Np-238 (yield per decay of Am-242m); the emitting nuclide is in brackets. Equilibrium is reached in about 3.1 years.
Alpha and beta particles
| Radiation | Energy, keV | Yield, % |
|---|---|---|
| α | 5,207.1 | 0.4085 |
| 6,112.7 (Cm-242) | 61.18 | |
| 6,069.4 (Cm-242) | 21.41 | |
| 5,969.2 (Cm-242) | 0.0289 | |
| β⁻, E max | 622.37 (Am-242) | 45.28 |
| 664.5 (Am-242) | 37.04 | |
| 263.46 (Np-238) | 0.2056 | |
| 1,247.9 (Np-238) | 0.1882 |
For β⁻ the endpoint (maximum) energy of the spectrum is given. ENDF/B-VIII.0.
Related calculators
Other isotopes of this element
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.