Proton-proton correlations observed in two-proton radioactivity of 94Ag.
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'.
Mukha
Ivan
I
Gesellschaft für Schwerionenforschung, D-64291 Darmstadt, Germany. I.Mukha@gsi.de
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Batist
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Blazhev
Andrey
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Döring
Joachim
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Grawe
Hubert
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Grigorenko
Leonid
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Huyse
Mark
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Janas
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Kirchner
Reinhard
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La Commara
Marco
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Mazzocchi
Chiara
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Tabor
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Van Duppen
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