Ivan Mukha, Andrey Blazhev, Piet Van Duppen, H. Grawe, L. V. Grigorenko, L. Batist, Z. Janas, E. Roeckl, R. Kirchner, Marco La Commara, Chiara Mazzocchi, Sam L Tabor, Joachim Döring, Mark Huyse, Ivan, Mukha, Ernst, Roeckl, Leonid, Batist, Andrey, Blazhev, Joachim, Döring, Hubert, Grawe, Leonid, Grigorenko, Mark, Huyse, Zenon, Jana, Reinhard, Kirchner, LA COMMARA, Marco, Chiara, Mazzocchi, Sam L., Tabor, and Piet Van, Duppen
The stability and spontaneous decay of naturally occurring atomic nuclei have been much studied ever since Becquerel discovered natural radioactivity in 1896. In 1960, proton-rich nuclei with an odd or an even atomic number Z were predicted1 to decay through one- and two-proton radioactivity, respectively. The experimental observation of one-proton radioactivity was first reported2 in 1982, and two-proton radioactivity has now also been detected by experimentally studying the decay properties of 45Fe (refs 3, 4) and 54Zn (ref. 5). Here we report proton–proton correlations observed during the radioactive decay of a spinning long-lived state of the lightest known isotope of silver6, 94Ag, which is known to undergo one-proton decay7. We infer from these correlations that the long-lived state must also decay through simultaneous two-proton emission, making 94Ag the first nucleus to exhibit oneas well as two-proton radioactivity. We attribute the two-proton emission behaviour and the unexpectedly large probability for this decay mechanism to a very large deformation of the parent nucleus into a prolate (cigar-like) shape, which facilitates emission of protons either from the same or from opposite ends of the ‘cigar’.