24-25 March 2022
Europe/Paris timezone

Structure of Ca isotopes between doubly closed shells

25 Mar 2022, 15:15


Simone Bottoni (Università degli Studi di Milano and INFN)


Calcium nuclei between doubly closed shells, i.e. N=20 and N=28, offer a unique opportunity to investigate the evolution of nuclear structure from symmetric to neutron-rich systems. Along this isotopic chain, spherical configurations at shell closures are expected to be overcome by deformed structures in mid-shell nuclei, already at low excitation energy. This will significantly affect the interplay between single-particle and collective excitations, as well as particle/hole-core coupling schemes which appear in odd-mass isotopes. In this context, Ca nuclei lie in a mass region where different theoretical models, with different predictive powers, can be applied and turn out to be complementary to each other. This embraces ab initio approaches [1], shell-model calculations [2], DFT’s [3] and beyond-mean-field models [4-5].
In this work, we present recent results on the low-spin structure of $^{41-49}$Ca nuclei, populated in a series of (n,$\gamma$), neutron-capture experiments performed at Institut Laue-Langevin in Grenoble. These studies required the use of very rare target materials, such as $^{46}$Ca and $^{48}$Ca, as well as a radioactive $^{41}$Ca sample. High-resolution $\gamma$-ray spectroscopy was performed by using the high-efficiency EXILL [6-7] and FIPPS [8] HPGe composite arrays. Several new $\gamma$ rays were found, and level schemes were substantially extended up to the neutron-capture state, approaching a complete low-spin spectroscopy for these isotopes. Moreover, $\gamma$-ray angular correlations were performed in order to pin down the multipolarity of a number of transitions, thus helping in the spin-parity assignment of the observed states. A selection of the experimental results is discussed and compared with theoretical calculations, including those obtained with the Hybrid Configuration Mixing model recently developed by the Milano group [4,5,7].

[1] J. D. Holt et al., Phys. Rev. C 90, 024312 (2014).
[2] Y. Utsuno et al., Progr. Theor. Phys. Suppl. 196, 304 (2012).
[3] M. Bender et al., Rev. Mod. Phys. 75, 121 (2003).
[4] G. Colò et al., Phys. Rev. C 95 (2017) 034303.
[5] S. Bottoni et al., in preparation.
[6] M. Jentschel et al., J. Instrum. 12, 11003 (2017).
[7] S. Bottoni et al., Phys. Rev. C 103, 014320 (2020).
[8] C. Michelagnoli et al., EPJ Web of Conf. 193 04009 (2018).

Primary author

Simone Bottoni (Università degli Studi di Milano and INFN)


Silvia Leoni (University of Milano and INFN Milano) Giovanna Benzoni (INFN Milano) Angela Bracco (University of Milano and INFN) Gianluca Colò (University of Milano and INFN) Giacomo Colombi Fabio Crespi (Università degli Studi di Milano / INFN) Lukasz ISKRA Bogdan Fornal (IFJ PAN Krakow) Natalia Cieplicka-Orynczak (IFJ PAN) Michael Jentschel (Institut Laue-Langevin) Yung Hee Kim Ulli Koester Dr. Caterina Michelagnoli (Institut Laue-Langevin) Paolo Mutti Torsten Soldner Jean Marc Regis (University of Cologne, Germany) Lukas KNAFLA Nicolae Marius Marginean (IFIN-HH Bucharest) Calin Ur (ELI-NP, Magurele-Bucharest, Romania) Waldek Urban ( University of Warsaw, Poland) A. Türler (Universität Bern and Paul Scherrer Institut, Villigen, Switzerland) Yifei Niu (University of Lanzhou, China)

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