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

  • 1
    $\begingroup$ You know the quark content of the nuclei. So why don't you just apply the connection between quark content and isospin? $\endgroup$
    – ACuriousMind
    Nov 12, 2014 at 20:55
  • $\begingroup$ 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. $\endgroup$
    – Caute
    Nov 12, 2014 at 21:15
  • $\begingroup$ This seems like two unrelated questions, which should be asked separately. $\endgroup$
    – user4552
    Nov 13, 2014 at 1:44
  • $\begingroup$ Ben, I think you are right. $\endgroup$
    – Caute
    Nov 13, 2014 at 11:15

1 Answer 1


The best place to look is the Evaluated Nuclear Structure Data File, hosted by the National Nuclear Data Center at Brookhaven National Lab. For example, the data file for helium-4,
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.


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