Systematics of toroidal dipole modes in Ca, Ni, Zr, and Sn isotopes

Repko A, Nesterenko VO, Kvasil J, Reinhard PG (2019)

Publication Type: Journal article

Publication year: 2019

Journal

European Physical Journal A EDP Sciences: EPJ

Book Volume: 55

Article Number: 242

Journal Issue: 12

DOI: 10.1140/epja/i2019-12770-x

Abstract

We analyze the relation between isoscalar toroidal modes and so-called pygmy dipole resonance (PDR), which both appear in the same region of low-energy dipole excitations. To this end, we use a theoretical description within the fully self-consistent Skyrme quasiparticle random-phase approximation (QRPA). Test cases are spherical nuclei ^{40, 48}Ca, ^{58, 72}Ni, ^{90, 100}Zr, and ^{100, 120, 132}Sn which cover four different elements and for each element at least two isotopes with different neutron excess, one small and another large. The structure of the modes is investigated in terms of strength functions, transition densities (TD) and transition currents (TC). For all considered nuclei, we see that, independently on whether PDR strength exists or not, the flow pattern in the lower part of the “PDR energy region” is basically an isoscalar vortical toroidal motion with a minor irrotational fraction. A one-to-one correspondence between calculated TD and TC is established. The toroidal flow appears already in the uncoupled two-quasiparticle (2qp) excitations and becomes definitively strong for the QRPA modes. Altogether, we find that low-lying dipole strength often denoted as isoscalar PDR is actually an oversimplified imitation of the basically toroidal motion in nuclei with sufficient neutron excess.

Authors with CRIS profile

Paul-Gerhard Reinhard Naturwissenschaftliche Fakultät

Involved external institutions

Institute of Physics Slovak Academy of Sciences

Slovakia (SK) Joint Institute for Nuclear Research (JINR) / Объединённый институт ядерных исследований (ОИЯИ)

Russian Federation (RU) Univerzita Karlova v Praze / Charles University in Prague

Czech Republic (CZ)

How to cite

APA:

Repko, A., Nesterenko, V.O., Kvasil, J., & Reinhard, P.-G. (2019). Systematics of toroidal dipole modes in Ca, Ni, Zr, and Sn isotopes. European Physical Journal A, 55(12). https://doi.org/10.1140/epja/i2019-12770-x

MLA:

Repko, A., et al. "Systematics of toroidal dipole modes in Ca, Ni, Zr, and Sn isotopes." European Physical Journal A 55.12 (2019).

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