Nuclear Physics – Difference Between Binding Energy and Separation Energy

binding-energynuclear-physicsterminology

My understanding of the two was as follows: the binding energy of a nucleus is, classically speaking, the energy needed to put together/take apart that nucleus completely (i.e. a measure of the strong force within that nucleus). However, in my mind separation energy is the energy necessary to take apart that nucleus into two (or more I suppose) specific constituent particles/nuclei.

I keep seeing these terms used, and I'm pretty sure my idea of these words is completely skewed. Could you tell me what these terms actually mean?

Best Answer

I believe you have the basic ideas correct.

The binding energy is the energy required to create $Z$ separate protons and $N=A-Z$ separate neutrons from a $(A,Z)$ nucleus in its ground state. Another way to think about it is binding energy is the mass energy which is missing from a nucleus compared to the mass energy of the individual nucleons.

When talking about separation energy one should specify what is being separated from a nucleus. One can calculate 1-proton separation energy, 2-proton separation energy, 1-neutron separation energy, etc. For example (as you suggest correctly), the 1-proton separation energy would be $$ [m(A-1,Z-1) + m(p) - m(A,Z)]c^2$$ where $m$ is the nuclear mass.

Related Question