Focus: Nuclei Emit Paired-up Neutrons Published March 9, 2012 | Physics 5, 30 (2012) | DOI: 10.1103/Physics.5.30
A neutron-rich nucleus can emit a neutron pair as a single unit as a product of nuclear decay. A neutron-only nucleus is considered physically impossible, but researchers have now seen a short-lived neutron pairing as a product of nuclear decay. The so-called dineutron had been indirectly observed inside neutron-rich nuclei, but the new experimental evidence reported in Physical Review Letters confirms that pairs of neutrons can exist outside the nucleus, albeit for a very short time. Further dineutron research could provide insight into the nuclear physics of neutron stars and supernovae. The forces holding together the protons and neutrons in a nucleus are not completely understood. Exotic forms of matter, such as dineutrons and diprotons, offer researchers the chance to push their models to extremes and see how well they hold up. Both dineutrons and diprotons are nearly stable, so researchers have searched for brief appearances of these particle pairs in nuclear reactions for several decades. Most of these searches have looked for diprotons because neutron-rich nuclei are harder to make, and neutrons are harder to detect. The results have been ambiguous, in part because the electric charge on the proton complicates the data analysis... http://physics.aps.org/articles/v5/30 http://prl.aps.org/abstract/PRL/v108/i10/e102501
