African Nuclear Physics Conference 2021

Microscopic description of isoscalar giant monopole resonance: The case of 132Sn

24 Sep 2021, 12:20

20m

Oral Nuclear Structure, Reactions and Dynamics Session 12

Speaker

Nikolay Arsenyev (Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research)

Description

The study of nuclear giant resonances has long been a subject of extensive theoretical and experimental research. The multipole response of nuclei far from the beta-stability line and the possible occurrence of exotic modes of excitation present a growing field of research. In particular, the study of the isoscalar giant monopole resonances (ISGMR) in neutron-rich nuclei is presently an important problem not only from the nuclear structure point of view [1] but also because of the special role they play in many astrophysical processes such as prompt supernova explosions [2] and the interiors of neutron stars [3]. One of the successful tools for describing the ISGMR is the quasiparticle random phase approximation (QRPA) with the self-consistent mean-field derived from Skyrme energy density functionals (EDF) [4]. Due to the anharmonicity of the vibrations there is a coupling between one-phonon and more complex states [5]. The main difficulty is that the complexity of calculations beyond standard QRPA increases rapidly with the size of the configuration space, and one has to work within limited spaces. Using a finite rank separable approximation for the residual particle-hole interaction derived from the Skyrme forces one can overcome this numerical problem [6-8].
In the present report, we study the effects of phonon-phonon coupling on the monopole strength distributions of neutron-rich tin isotopes. Using the same set of the EDF parameters, we describe available experimental data for 118,120,122,124Sn [9] and give prediction for 132Sn [10]. The effects of the phonon-phonon coupling leads to a redistribution of the main monopole strength to lower energy states and also to higher energy tail. We analyze thoroughly the properties of the low-energy 0+ spectrum of two-phonon excitations of 132Sn. We give prediction for the excitation energy of the lowest two-phonon state around Ex=8 MeV in comparison to 11.5 MeV in the case of the lowest 0+ state within the random phase approximation.

This work was partly supported by the Heisenberg-Landau (Germany-BLTP JINR) program and the National Research Foundation of South Africa (Grant No.129603).

1. J.P. Blaizot, Phys. Rep. 64, 171 (1980).
2. H.A. Bethe, Rev. Mod. Phys. 62, 801 (1990).
3. N.K. Glendenning, Phys. Rev. Lett. 57, 1120 (1986).
4. N. Paar, D. Vretenar, E. Khan, G. Colò, Rep. Prog. Phys. 70, 691 (2007).
5. V.G. Soloviev, Theory of Atomic Nuclei: Quasiparticles and Phonons, Bristol/Philadelphia (1992).
6. N.V. Giai, Ch. Stoyanov, V.V. Voronov, Phys. Rev. C 57, 1204 (1998).
7. A.P. Severyukhin, V.V. Voronov, N.V. Giai, Phys. Rev. C 77, 024322 (2008).
8. A.P. Severyukhin, V.V. Voronov, N.V. Giai, Eur. Phys. J. A. 22, 397 (2004).
9. T. Li, U. Garg, Y. Liu et al., Phys. Rev. C 81, 034309 (2010).
10. N.N. Arsenyev, A.P. Severyukhin, Universe 7, 145 (2021).