The “Nested Doll” Nucleus Nitrogen-9 Stretches the Definition of a Nucleus to the Limit

Experimentalists and theorists have provided strong evidence for the creation of an exotic isotope, nitrogen-9, which has two neutrons and seven protons. This unbalanced ratio of protons to neutrons produces a nucleus that only survives for less than one-billionth of a nanosecond. The work also provides information on nitrogen-9’s mirror nucleus, helium-9, which has two protons to its seven neutrons.