New type of asymmetric fission in proton-rich nuclei

陽子過剰核における新しい非対称核分裂

Andreyev, A. N.*; Elseviers, J.*; Huyse, M.*; Van Duppen, P.*; Antalic, S.*; Barzakh, A.*; Bree, N.*; Cocolios, T. E.*; Comas, V. F.*; Diriken, J.*; Fedorov, D.*; Fedosseev, V.*; Franchoo, S.*; Heredia, J. A.*; Ivanov, O.*; Kster, U.*; Marsh, B. A.*; 西尾 勝久   ; Page, R. D.*; Patronis, N.*; Seliverstov, M.*; Tsekhanovich, I.*; Van den Bergh, P.*; Van De Walle, J.*; Venhart, M.*; Vermote, S.*; Veselsky, M.*; Wagemans, C.*; 市川 隆敏*; 岩本 昭; Mller, P.*; Sierk, A. J.*

Andreyev, A. N.*; Elseviers, J.*; Huyse, M.*; Van Duppen, P.*; Antalic, S.*; Barzakh, A.*; Bree, N.*; Cocolios, T. E.*; Comas, V. F.*; Diriken, J.*; Fedorov, D.*; Fedosseev, V.*; Franchoo, S.*; Heredia, J. A.*; Ivanov, O.*; Kster, U.*; Marsh, B. A.*; Nishio, Katsuhisa; Page, R. D.*; Patronis, N.*; Seliverstov, M.*; Tsekhanovich, I.*; Van den Bergh, P.*; Van De Walle, J.*; Venhart, M.*; Vermote, S.*; Veselsky, M.*; Wagemans, C.*; Ichikawa, Takatoshi*; Iwamoto, Akira; Mller, P.*; Sierk, A. J.*

A very exotic process of -delayed fission of Tl is studied in detail by using resonant laser ionization with subsequent mass separation at ISOLDE (CERN). In contrast to common expectations, the fission-fragment mass distribution of the post--decay daughter nucleus Hg (/ = 1.25) is asymmetric. This asymmetry is more surprising since a mass-symmetric split of this extremely neutron-deficient nucleus would lead to two Zr fragments, with magic = 50 and semi-magic = 40. This is a new type of asymmetric fission, not caused by large shell effects related to fragment magic proton and neutron numbers, as observed in the actinide region. The newly-measured branching ratio for -delayed fission of Tl is 3.6(7)10 %.