Nuclear halo

In nuclear physics, an atomic nucleus is called a halo nucleus or is said to have a nuclear halo if its radius is appreciably larger than that predicted by the liquid drop model, wherein the nucleus is assumed to be a sphere of constant density.For a nucleus of mass number A, the radius r is (approximately) where is 1.2 fm.
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In the 1980s at the Lawrence Radiation Laboratory, Berkeley it was found that the nucleus of 11Li had a a radius about 1.5 times larger than expected. Other very short lived light nuclides were found to have a large cross-sectional area as if there is a core protons and neutrons surrounded by 2-neutron halo . The larger than expected cross-sections may mean that collision probabilities in hot plasma in stars could be greater than hitherto calculated. This may be significant in the triple helium element building process.