title: Proton-proton correlations observed in two-proton radioactivity of 94Ag.
abstract: 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 predicted to decay through one- and two-proton radioactivity, respectively. The experimental observation of one-proton radioactivity was first reported 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 silver, 94Ag, which is known to undergo one-proton decay. 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 one- as 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'.
authors.affiliation: Gesellschaft für Schwerionenforschung, D-64291 Darmstadt, Germany. I.Mukha@gsi.de
authors.forename: Ivan
authors.initials: I
authors.lastname: Mukha
authors.forename: Ernst
authors.initials: E
authors.lastname: Roeckl
authors.forename: Leonid
authors.initials: L
authors.lastname: Batist
authors.forename: Andrey
authors.initials: A
authors.lastname: Blazhev
authors.forename: Joachim
authors.initials: J
authors.lastname: Döring
authors.forename: Hubert
authors.initials: H
authors.lastname: Grawe
authors.forename: Leonid
authors.initials: L
authors.lastname: Grigorenko
authors.forename: Mark
authors.initials: M
authors.lastname: Huyse
authors.forename: Zenon
authors.initials: Z
authors.lastname: Janas
authors.forename: Reinhard
authors.initials: R
authors.lastname: Kirchner
authors.forename: Marco
authors.initials: M
authors.lastname: La Commara
authors.forename: Chiara
authors.initials: C
authors.lastname: Mazzocchi
authors.forename: Sam L
authors.initials: SL
authors.lastname: Tabor
authors.forename: Piet
authors.initials: P
authors.lastname: Van Duppen