Speaker
Dr
Nikolay Arsenyev
(Bogoliubov Laboratory of Theoretical Physics, JINR, Dubna, Russia)
Description
The structure of exotic neutron-rich nuclei is one of the main science drivers in contemporary nuclear physics research. An attention has been devoted to effects of varying the ratio between the proton $Z$ and neutron $N$ numbers on different nuclear structure characteristics of nuclei deviated from their valley of $\beta$-stability. One of the phenomena associated with the change in $N/Z$ ratios is the pygmy dipole resonance (PDR) [1]. One of the successful tools for describing the PDR is the quasiparticle random phase approximation (QRPA) with the self-consistent mean-field derived from Skyrme energy density functionals (EDF) [2]. Such an approach can describe the properties of the low-lying states reasonably well by using existing Skyrme interactions. Due to the anharmonicity of the vibrations there is a coupling between one-phonon and more complex states [3]. 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 [4-6].
In the present report, we analyze the effects of phonon-phonon coupling (PPC) on the $E1$ strength distributions of neutron-rich calcium and nickel isotopes. Using the same set of the EDF parameters we describe available experimental data for $^{48}$Ca, $^{68}$Ni and give prediction for $^{50}$Ca, $^{70}$Ni. The inclusion of the PPC results in the formation of low energy $1^{-}$ states of $^{48}$Ca. There is an impact of the PPC effect on low-energy $E1$ strength of $^{48}$Ca [7]. The effect of the low-energy $E1$ strength on the electric dipole polarizability is discussed. We predict a strong increase of the summed $E1$ strength below 10 MeV (12 MeV), with increasing neutron number from $^{48}$Ca ($^{68}$Ni) till $^{50}$Ca ($^{70}$Ni) [8].
This work is partly supported by CNRS-RFBR agreement No. 16-52-150003.
1. D. Savran, T. Aumann, A. Zilges // Prog. Part. Nucl. Phys. 2013. V. 70. P. 210.
2. N. Paar, D. Vretenar, E. Khan, G. Colò // Rep. Prog. Phys. 2007. V. 70. P. 691.
3. V.G. Soloviev // Theory of Atomic Nuclei: Quasiparticles and Phonons. 1992. Bristol/Philadelphia.
4. Nguyen Van Giai, Ch. Stoyanov, V.V. Voronov // Phys. Rev. C. 1998. V. 57. P. 1204.
5. A.P. Severyukhin, V.V. Voronov, Nguyen Van Giai // Phys. Rev. C. 2008. V. 77. P. 024322.
6. A.P. Severyukhin, V.V. Voronov, Nguyen Van Giai // Eur. Phys. J. A. 2004. V. 22. P. 397.
7. N.N. Arsenyev, A.P. Severyukhin, V.V. Voronov, Nguyen Van Giai // Phys. Rev. C. 2017. V. 95. P. 054312.
8. N.N. Arsenyev, A.P. Severyukhin, V.V. Voronov, Nguyen Van Giai // in preparation.
Primary author
Dr
Nikolay Arsenyev
(Bogoliubov Laboratory of Theoretical Physics, JINR, Dubna, Russia)
Co-authors
Dr
Alexey Severyukhin
(Bogoliubov Laboratory of Theoretical Physics, JINR, Dubna, Russia)
Prof.
Van Giai NGUYEN
(Institut de Physique Nucléaire, CNRS-IN2P3, Université Paris-Sud, Orsay Cedex, France)
Prof.
Victor Voronov
(Bogoliubov Laboratory of Theoretical Physics, JINR, Dubna, Russia)
