Why Does Alpha Emission Occur in Nuclear Physics?

[jokeb]

Hi, quick one:

In my nuclear physics notes it says alpha emission is often the only light particle emission that takes place due to its very high binding energy.

What I don't understand is that how come the nucleus wants to retain binding energy?
I would have thought that it wants to get rid of the positive charge, but retain as much binding energy as possible to stay stable?

thanks for any help.

 

[ansgar]

you have to think of tunnelling, the protons inside the nucleus has a large coulomb barrier to climb and they all have individual wave functions. Since the alpha has so high Bind Energy it can be formed "inside" the nucleus and be viewed as one entity and thus have one wavefunction and will have higher probability to be emitted than just two single protons.