In this chapter, the discovery and basic concepts of radioactive tracer methods, namely the first experiments by George de Hevesy, will be discussed, including the most important factors in the selection of the tracers (e.g., sensitivity, selectivity, homogeneity, half-life, type of radiation, purity, and costs).
A particular nucleus of this isotope has not decayed within a time interval of five minutes.
In the next five minute interval the nucleus has a 50% chance of decaying.
(Comes from : the rate of decay/ activity is proportional to the number of nuclei) Decay constant : The probability of decay of a nucleus per unit time, and is characteristic of that particular nuclide. Activity of a source: (Given initial activity and half-life, initial number of nuclei can be calculated from ) Half-life: The time taken for half the nuclei in a given sample to decay.
Method for measuring short half-life of an isotope: Background radiation: Cosmic rays from outside the earth, decay of minerals present in materials/the earth. Add actual count rate after half-life to background rate 5.
Nuclear decay is – A process of disintegration that occurs when unstable nuclei decay in an attempt to attain stability, until their N/Z (neutron/proton) number falls within the stability limit/ band of stability.