α-Decay:
The nucleus which emits the α-particle, is called the parent nuclus. When an external nucleus emits α-particles the internal energy of the parent nucleus is very high and it is stable. For emission of additional energy, the parent nucleus emits an α-particle and the built nucleus is called the daughter nucleus. This daughter nucleus expresses the mass and velocity by md and vd respectively.
The equation of α-decay is written as follows:
ZXA → Z – 2YA – 4 + 2He4 + Q(energy)
In the equation the number of nucleons and charge are conserved.
92U238 → 90Th234 + 2He4
By the linear momentum conservation
The daughter nucleus is very heavy compared to α-particle, so almost the entire disintegration energy appears as the kinetic energy of the α-particle.
For example, at the time of α-decay from the 94Po210 nucleus the kinetic energy of the α-particle is 5.3 MeV then by the equation (3),
It is clear that disintegration energy almost appears in the form of kinetic energy of α-particle. If the potential barrier of nucleus is like the kinetic energy of α-particle then the α-particle may get rid of. It has been seen that the potential barrier of nucleus is 26 MeV.
According to quantum Mechanics, α-particles whose energy is 5.4 MeV does not exceed the potential barrier. But the energy of any α-particle emitted by the radioactive is not so much, so it can not escape from the nucleus. The problem of the escape of the nucleus of α-particle is solved by Gamaw. Condon and Gurney in 1928. According to this theory, α-particles are present in the nucleus before the emission of the nucleus.
(i) When the α-particle occurs in the nucleus, the nuclear attraction force work on it (r < R1).
(ii) When the α-particle comes out of the nucleus then the unstable repulsive force acts between the α-particles in the nucleus (r < R2) Disintegration energy of α-decay is almost equal to the kinetic energy of α-particle.
