Ядерна фізика та енергетика Nuclear Physics and Atomic Energy   ISSN: 1818-331X (Print), 2074-0565 (Online)   Publisher: Institute for Nuclear Research of the National Academy of Sciences of Ukraine   Languages: Ukrainian, English   Periodicity: 4 times per year   Open access peer reviewed journal

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V. A. Plujko^*, O. M. Gorbachenko, N. O. Romanovskyi

Taras Shevchenko National University of Kyiv, Kyiv, Ukraine

^*Corresponding author. E-mail address: plujko@gmail.com

Abstract: Fraction of the pygmy dipole resonance (PDR) in the energy-weighted sum rule for electric dipole gamma transitions (E1 EWSR) in medium-heavy and heavy nuclei with an excess of neutrons is analyzed. Macroscopic analytical expressions for the PDR fractions are compared with microscopic calculations and experimental data for isotopic chains of nickel, tin, and lead. Analytical expressions for calculating the PDR fractions of the E1 EWSR as a function of the number of surface neutrons are tested. The number of such neutrons is considered proportional to the thickness of the neutron skin. Systematics for the PDR fraction of the E1 EWSR are proposed.

Keywords: pygmy dipole resonance (PDR), energy-weighted sum rule for electric dipole transitions (E1 EWSR), PDR fraction of the E1 EWSR, neutron skin thickness, number of surface neutrons.

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