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Radioactive Decay
Alpha decay
This occurs in very heavy nuclei, with very high atomic number, Z > 82. All
He
4
2
α
−
−
+ +
⇒
Q He
daughter
parent
4
2
4A
2Z
A
Z
nuclides with atomic number higher than 82 are unstable and the majority
follow the alpha decay scheme. This is shown in the following equation:
Q
α
is the disintegration energy which is distributed between the kinetic energy
of the emitted α-particle (this represents the majority) and the recoil energy of
the daughter nucleus.
This means that the emitted α-particles have
discrete energy values
(hence a
discrete energy spectrum) that are lower than the disintegration energy Q
α
.
MeV
8706 .4 He Rn
Ra
4
2
222
86
226
88
+ +
⇒