The discovery of sharp resonance states in exotic, proton emitting, nuclei.

The discovery of sharp resonance states in exotic, proton emitting, nuclei.Little is known about the structure of unstable, proton emitting, nuclei.These nuclei can be produced during stellar explosions in the cosmos, andlive only for a very small fraction of second before they disintegrateinto more stable products. Nowadays, they are also produced and detectedin experiments made in large modern nuclear physics laboratories that areequipped with radioactive ion beams. Such elusive nuclei rapidly decay byemitting one (and sometimes two) protons, and for this reason areindicated as nuclei that lie outside of the so-called proton drip line.A recent publication (1) reports results of an experiment at the GSIlaboratory in Darmstdtat, Germany that showed the existence of excitedunstable states in two such nuclei, Fluorine-15 and Neon-16. Contrary tothe ground level characterized by a broad resonance with short life, theseexcited states have half-lives sufficiently long that they can beidentified as sharp resonances. Of note is that they have excitationenergy of several MeV, establishing that such particle unstable systemscan have an observable set of levels just as do the many known, particlestable nuclei.The existence of such narrow resonances in particle unstable nuclei, andin Fluorine-15 in particular, was predicted (2) three years ago by amethod of calculation put forward by nuclear theoreticians of the INFN,sez. di Padova, in collaboration with colleagues from Australia, Canadaand South Africa. To implement the method (an algebraic solution ofsystems of coupled equations for the problem of nuclear scattering andreactions) expertise in high performance computing was employed. Theexistence of sharp resonances in the spectra of radioactive, andspecifically of proton (and, may-be, of neutron) emitting nuclei, opensnew and interesting perspectives on the way the nuclei, that we observe atpresent in our Universe, have been formed.(1) Physical Review C (Rapid Communication) 79, 061301 (2009).(2) Physical Review Letters, 96, 072502 (2006).