Krypton-85
Krypton-85 (85Kr) is a radioisotope of krypton.
| General | |
|---|---|
| Symbol | 85Kr |
| Names | krypton-85, 85Kr, Kr-85 |
| Protons (Z) | 36 |
| Neutrons (N) | 49 |
| Nuclide data | |
| Half-life (t1/2) | 10.756 years |
| Isotope mass | 84.9125273(21) Da |
| Spin | 9/2+ |
| Excess energy | −81480.267 keV |
| Binding energy | 8698.562 keV |
| Decay products | 85Rb |
| Decay modes | |
| Decay mode | Decay energy (MeV) |
| Beta decay | 0.687 |
| Beta decay | 0.173 |
| Isotopes of krypton Complete table of nuclides | |
Krypton-85 has a half-life of 10.756 years and a maximum decay energy of 687 keV. It decays into stable rubidium-85. Its most common decay (99.57%) is by beta particle emission with maximum energy of 687 keV and an average energy of 251 keV. The second most common decay (0.43%) is by beta particle emission (maximum energy of 173 keV) followed by gamma ray emission (energy of 514 keV). Other decay modes have very small probabilities and emit less energetic gamma rays. Krypton-85 is mostly synthetic, though it is produced naturally in trace quantities by cosmic ray spallation.
In terms of radiotoxicity, 440 Bq of 85Kr is equivalent to 1 Bq of radon-222, without considering the rest of the radon decay chain.