# Isospin quantum number for light nuclei

Does anyone know where I can find the Isospin values for light nuclei (H, C,N, O, S, Cl, ..) in their ground state?

• You know the quark content of the nuclei. So why don't you just apply the connection between quark content and isospin? Nov 12, 2014 at 20:55
• I know the connection between quarks and nucleons, but I am not interested to that higher energy scale. We can give Isospin projection value +1/2 to protons and -1/2 to neutrons as they form a Isospin multiplet, and therefore determine Isospin from the nucleons in a nucleus. I would like to know where I can find experimental data for this quantum number in nuclei of light elements. Nov 12, 2014 at 21:15
• This seems like two unrelated questions, which should be asked separately.
– user4552
Nov 13, 2014 at 1:44
• Ben, I think you are right. Nov 13, 2014 at 11:15

shows that the first two states with isospin $T\neq 0$ are the negative-parity states centered at 23.3 and 23.6 MeV.
Be warned that at modest proton number $Z$ the assumption underlying isospin symmetry, namely that protons and neutrons can be treated symmetrically inside the nucleus, starts to break down and it may no longer be possible to assign a definite isospin to a state. For example neon-20, an "alpha-cluster" nucleus, is assigned a $T=0$ ground state, but neon-21 has isospin assignments only for some excited states and neon-22 seems to have no isospin-assigned states at all. The next alpha-cluster nucleus, magnesium-24, has no isospin assignment in the ground state and several excited states labeled "T=0 and 1". You can compare this to the orbital angular momentum mixing that makes the ground states for deuterium and helium-4 into complicated mixtures of $S$ and $D$ waves.