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arXiv · 1905.10313

Pairing-quadrupole interplay in the neutron-deficient tin nuclei: first lifetime measurements of low-lying states in $^{106,108}$Sn

Abstract

The lifetimes of the low-lying excited states $2^+$ and $4^+$ have been directly measured in the neutron-deficient $^{106,108}$Sn isotopes. The nuclei were populated via a deep-inelastic reaction and the lifetime measurement was performed employing a differential plunger device. The emitted $\gamma$ rays were detected by the AGATA array, while the reaction products were uniquely identified by the VAMOS++ magnetic spectrometer. Large-Scale Shell-Model calculations with realistic forces indicate that, independently of the pairing content of the interaction, the quadrupole force is dominant in the $B(E2; 2_1^+ \to 0_{g.s.}^+)$ values and it describes well the experimental pattern for $^{104-114}$Sn; the $B(E2; 4_1^+ \to 2_1^+)$ values, measured here for the first time, depend critically on a delicate pairing-quadrupole balance, disclosed by the very precise results in $^{108}$Sn. This result provides insight in the hitherto unexplained $B(E2; 4_1^+ \to 2_1^+)/B(E2; 2_1^+ \to 0_{g.s.}^+) < 1$ anomaly.

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M. Siciliano, J. J. Valiente-Dobón, A. Goasduff, F. Nowacki, A. P. Zuker, D. Bazzacco, A. Lopez-Martens, E. Clément, G. Benzoni, T. Braunroth, N. Cieplicka-Oryńczak, F. C. L. Crespi, G. de France, M. Doncel, S. Ertürk, C. Fransen, A. Gadea, G. Georgiev, A. Goldkuhle, U. Jakobsson, G. Jaworski, P. R. John, I. Kuti, A. Lemasson, H. Li, T. Marchi, D. Mengoni, C. Michelagnoli, T. Mijatović, C. Müller-Gatermann, D. R. Napoli, J. Nyberg, M. Palacz, R. M. Pérez-Vidal, B. Sayği, D. Sohler, S. Szilner, D. Testov, D. Barrientos, B. Birkenbach, H. C. Boston, A. J. Boston, B. Cederwall, D. M. Cullen, J. Collado, P. Désesquelles, J. Dudouet, C. Domingo-Pardo, J. Eberth, F. J. Egea-Canet, V. González, D. S. Judson, L. J. Harkness-Brennan, H. Hess, A. Jungclaus, W. Korten, M. Labiche, A. Lefevre, S. Leoni, A. Maj, R. Menegazzo, B. Million, A. Pullia, F. Recchia, P. Reiter, M. D. Salsac, E. Sanchis, O. Stezowski, Ch. Theisen, M. Zielińska. 2019-05-24. Pairing-quadrupole interplay in the neutron-deficient tin nuclei: first lifetime measurements of low-lying states in $^{106,108}$Sn. https://doi.org/10.1016/j.physletb.2020.135474

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