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Although all exotic helium isotopes decay with a half-life of less than one second, researchers have eagerly created exotic light isotopes though particle accelerator collisions to create unusual atomic nuclei for elements such as helium, lithium, and nitrogen. The bizarre nuclear structures of such isotopes may offer insight into the isolated properties of neutrons.
The most widely-studied exotic helium isotope, for example, is helium-8. This isotope is thought to consist of a normal helium-4 nucleus surrounded by four neutrons dubbed a "halo." Halo nuclei have become an area of intense research. Isotopes up to helium-10, with two protons and eight neutrons, have been confirmed. By comparison, the most common 4He isotope has only two neutrons.
isotope | decay chain produced from: | decays to: | half-life ( seconds) | notes |
| Helium-5 | none | helium-4 | ? | highly unstable |
| Helium-6 | helium-7 lithium-11 | lithium-6 | 0.8067 | decomposes through beta decayIn nuclear physics, beta decay (sometimes called neutron decay is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. In the case of electron emission, it is referred to as "beta minus" (β−); in the case |
| Helium-7 | none | helium-6 | very short | highly unstable |
| Helium-8 | helium-9 | lithium-7 lithium-8 | 0.119 | |
| Helium-9 | none | helium-8 | very short | highly unstable |
| Helium-10 | none | helium-9 | very short | highly unstable |