H-5 discovered

This is an update on the current state of the art concerning hydrogen.

The commonly known isotopes of hydrogen are:

  • Hydrogen-1, the "normal" and most abundant variety,
  • Hydrogen-2, known as deuterium, and
  • Hydrogen-3, known as tritium.
Isotopes, of course, are "variants" of an element with different numbers of neutrons in the nucleus. H-1 has a lone proton, H-2 has a proton and one neutron, H-3 has a proton and two neutrons.

Deuterium and tritium are constituents of heavy water. Tritium is radioactive. Both are much rarer than H-1 and play a role in the development both of the hydrogen bomb and of nuclear fusion reactors.

Atom-smashing equipment, in particular particle accelerators, enable physicists to create some isotopes which do not occur in nature. Apparently they've already produced H-4, a synthetic isotope with 3 neutrons in the nucleus, but I haven't come across any exciting information about this. The big news is H-5.

Late in 2001, an international group of researchers collided a beam of helium-6 nuclei into a target of cryogenic (frozen) hydrogen. In the ensuing nuclear reaction, it's possible for the He-6 to transfer all 4 of its neutrons to the hydrogen, turning it into - Hydrogen-5. Of course the experiment, which took place at the RIKEN detector in Japan, produced only trace quantities of the highly unstable isotope; and rather than collecting some of the product, the researchers obtained only indirect evidence of the production of this isotope. Still, it's considered a major breakthrough in nuclear physics, as the search for H-5 had been ongoing for 40 years previously.

  • http://www.spiegel.de/wissenschaft/mensch/0,1518,151441,00.html
  • http://physicsweb.org/article/news/5/8/15