Superheavy Hydrogen

Superheavy hydrogen, a nucleus with one proton and four neutrons, has been made by Russian, French, and Japanese physicists at the accelerator at the Joint Institute for Nuclear Physics (JINR) near Moscow.

An exotic beam of helium-6 nuclei struck a hydrogen target, resulting in the occasional production of a hydrogen-5 nucleus plus a helium-2 nucleus. These unstable particles quickly fly apart. The debris--two protons from the ²He breakup and a triton and two neutrons from the ⁵H breakup--tell the story.

If the two-nucleon version of hydrogen is called deuterium and the three-nucleon hydrogen is called triton, what would one call a five-nucleon (intensely neutron rich) hydrogen--pentium? (Korsheninnikov et al., Physical Review Letters, 27 August 2001.)