Calculate nuclear decays per unit time in becquerels from decay constant and number of nuclei. Suitable for radiochemistry and nuclear medicine activity quantification.
单位时间衰变数（贝可勒尔）。
| Item | Formula / Note | Source / Standard |
|---|---|---|
| Activity definition | A = λN decays per second | Nuclear physics |
| Units | Bq = s⁻¹; 1 Ci = 3.7×10¹⁰ Bq | SI units |
| Specific activity | a = A/m | Nuclide properties |
| Atom count | N = m·N_A/M | Molar relation |
| Decay correction | A(t) = A₀e^(−λt) | Decay law |
| Measurement | Coincidence, 4π counting, LSC | Radioactivity metrology |
Constants used on this page and their authoritative sources, for verification and citation
| Constant | Value | Unit | Source |
|---|---|---|---|
| Curie (Ci, non-SI unit) | 3.7e10 | Bq | Historical definition (activity of 1 g of radium-226, exact by convention) |
| Avogadro constant N_A | 6.02214076e23 | mol⁻¹ | SI defining constant (exact) |
| Natural logarithm of 2, ln 2 | 0.6931471805599453 | — | Mathematical constant (exact) |
Note: the becquerel (Bq = s⁻¹) is the SI derived unit of activity; the curie is a historical non-SI unit retained by ICRU, with 1 mCi = 37 MBq.