← nuclearjs halo nuclei scattering
The deuteron
One proton and one neutron, held together by 2.2 MeV, the only bound state of two nucleons. Its spins are aligned (Jπ = 1+), and the force between them depends on how those spins point relative to the line joining them: the tensor force. It mixes a little D wave into the S wave, and the deuteron stops being round. And it is so weakly bound that the neutron spends most of its time outside the range of the force that holds it.