Individual low-energy E1 toroidal and compression states in light nuclei: deformation effect, spectroscopy and interpretation

¹ Bogoliubov Laboratory of Theoretical Physics, JINR, 141980 Dubna, Moscow region, Russia
² Dubna State University, 141982 Dubna, Moscow Region, Russia
³ Moscow Institute of Physics and Technology, 141701 Dolgoprudny, Moscow region, Russia
⁴ Institute of Particle and Nuclear Physics, Charles University, CZ-18000, Praha 8, Czech Republic
⁵ Institute of Physics, Slovak Academy of Sciences, 84511 Bratislava, Slovakia
⁶ Institut für Theoretische Physik II, Universität Erlangen, D-91058, Erlangen, Germany

^* e-mail: nester@theor.jinr.ru

Published online: 14 November 2018

Abstract

The existence of individual low-energy E1 toroidal and compression states (TS and CS) in ²⁴Mg was predicted recently in the framework of quasiparticle random phase approximation (QRPA) model with Skyrme forces. It was shown that the strong axial deformation of ²⁴Mg is crucial to downshift the toroidal strength to the low-energy region and thus make the TS the lowest E1(K=1) dipole state. In this study, we explain this result by simple mean-field arguments. Comparing TS in two strongly axial nuclei, ²⁴Mg and ²⁰Ne, we show that the lowest TS is not a universal phenomenon but rather a peculiarity of ²⁴Mg. The spectroscopy of TS and CS is analyzed and some additional interpretation of these states is suggested.