First direct lifetime measurement of the 2+1 state in 72,74Zn: new evidence for shape transition between N = 40 and N = 42 close to Z = 28

• Published in: arXiv.org 2012-04
• Main Authors: Niikura, M, Mouginot, B, Franchoo, S, Matea, I, Stefan, I, Verney, D, Azaiez, F, Assie, M, Bednarczyk, P, Borcea, C, Burger, A, Burgunder, G, Buta, A, Càceres, L, Clément, E, Coquard, L, de Angelis, G, de France, G, de Oliveira Santos, F, Dewald, A, Dijon, A, Dombradi, Z, Fiori, E, Fransen, C, Friessner, G, Gaudefroy, L, Georgiev, G, Grévy, S, Hackstein, M, Harakeh, M N, Ibrahim, F, Kamalou, O, Kmiecik, M, Lozeva, R, Maj, A, Mihai, C, Möller, O, Myalski, S, Negoita, F, Pantelica, D, Perrot, L, Pissulla, Th, Rotaru, F, Rother, W, Scarpaci, J A, Stodel, C, Thomas, J C, Ujic, P
• Format: Article
• Language: English
• Subjects: Inelastic scattering; Lifetime; Nuclei (nuclear physics); Recoil; Softness; Transition probabilities
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1105.4072

We report here the first direct lifetime measurement of the 2+1 state in 72,74Zn. The neutron-rich beam was produced by in-flight fragmentation of 76Ge at the Grand Accélérateur National d'Ions Lourds and separated with the LISE spectrometer. The 2+1 state was excited by inelastic scattering and knock-out reaction on a CD2 target and its lifetime was measured by the recoil-distance Dopplershift method with the K\"oln plunger device combined with the EXOGAM detectors. The lifetimes of the 2+1 states in 72,74Zn were determined to be 17.9(18) and 27.0(24) ps, which correspond to reduced transition probabilities B(E2; 2+1 \rightarrow 0+) = 385(39) and 370(33) e2fm4, respectively. These values support the idea of a systematic maximum of collectivity at N = 42 for Zn, Ge and Se nuclei. In addition, the available systematics in the neighboring nuclei point towards a transition from a spherical oscillator at N = 40 to complete {\gamma}-softness at N = 42.