Proportionality constant relating the activity of a radioactive substance,
A, to the number of decaying particles
B, N B, A = λNB. probability of a nuclear decay within a time interval divided by that time interval. Synonymous with disintegration constant.
Source:
Green Book, 2nd ed., p. 22 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)
See also:
PAC, 1994, 66, 2513. 'Nomenclature for radioanalytical chemistry (IUPAC Recommendations 1994)' on page 2518 (https://doi.org/10.1351/pac199466122513)
PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 968 (https://doi.org/10.1351/pac199668040957)