Study of $0^{+}$ and $8^{-}$ states in even-even ${}^{250-260}$No isotopes

Abstract

Low-lying $K^{\pi }=0^{+}$ and isomeric $8^{-}$ states in even-even isotopes ${}^{250-260}$No are explored within the Quasiparticle Random-Phase Approximation (QRPA) method with Skyrme parametrization SLy4. The deformations, single-particle (s-p) spectra and pairing in the isotopes are inspected. The calculations predict a pronounced minimum in the neutron pairing at $A$=252, 254, which significantly affects the properties of $0^{+}$ and $8^{-}$ states and leads to a correlation of their spectra. It is shown that $8^{-}$ isomers are basically low-energy two-quasiparticle (2qp) states. The appearance or absence of these isomers in ${}^{250-260}$No is explained as a combined effect of the s-p spectra and pairing. The collective $0^{+}$ states are predicted in all the isotopes as the lowest multipole non-rotational excitations. These states are interpreted as a superposition of pairing vibrations and $\beta$-vibrations. The results are in a reasonable agreement with available experimental data for ${}^{252,254}$No.

Comments: 4 pages, 3 figures, 3 tables. Submitted to proceedings of INPC-2025