Nuclear Spectroscopy

MULTIPLE DECAY PATHS
If a nuclide can decay by multiple processes , then the
decay constant for the nuclide is the sum of the decay
constants for each decay process. A good example is
40
K, which can β − decay to 40 Ca with decay constant λ −
and can electron capture/β + decay to 40 Ar with a decay
constant λ +
. The decay constant for 40 K, λ, is
C.14
λ = λ− + λ+
and the half life of 40 K is
ln 2 ln 2
C.15 T 12 = =
λ λ + λ
( )
− +
For this example the beta activity, A β -, is given by
C.16 A − λ N 40 t λ N 40 0 e
β
= ()= ( )
−
K
−
K
( )
− λ− + λ+
t
and similarly for the electron capture-positron
decay path.
67