arXiv subjects

M. A. Mardyban

Publications and source records attributed to M. A. Mardyban.

4 recordsLinked to original sources

arXiv2026

Microscopic analysis of M1 scissors mode in $^{254}$No

The low-energy $M1$ orbital scissors mode (SM) was recently observed by Oslo group in deformed nucleus $^{254}$No. This is the heaviest nucleus where SM was ever experimentally found. We propose the analysis of SM, together with the spin-flip $M1$ resonance, within fully self-consistent Quasiparticle Random-Phase Approximation (QRPA) with Skyrme forces SG2, SLy4 and SLy5. The impact of "tensor" $J^2$-term, introduced by perturbative (on the base of SG2) and consistent (SLy5) ways, is analyzed and shown to be noticeable but not decisive. The deformation-induced coupling of $M1$ and $E2$ states is inspected. The calculations reasonably describe Oslo's experimental data. The best agreement is obtained for SLy5. A fine structure of SM in $^{254}$No is predicted. A significant constructive interference of the dominant orbital and minor spin-flip contributions to $M1$ strength at SM energy region is found. What is remarkable, our analysis of distributions of the convective nuclear currents challenges the scissors-like flow usually assumed for SM.

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arXiv2025

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

Low-lying $K^π=0^+$ 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 $β$-vibrations. The results are in a reasonable agreement with available experimental data for $^{252,254}$No.

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arXiv2025

Low-energy spectra of nobelium isotopes: Skyrme random-phase-approximation analysis

Low-energy spectra in the isotopic chain $^{250-262}$No are systematically investigated within the fully self-consistent Quasiparticle Random-Phase-Approximation (QRPA) using Skyrme forces SLy4, SLy6, SkM* and SVbas. QRPA states of multipolarity $λμ$=20, 22, 30, 31, 32, 33, 43, 44 and 98 are considered. The main attention is paid to isotopes $^{252}$No and $^{254}$No where the most extensive experimental spectroscopic information is available. In these two nuclei, a reasonable description of $K^π=8^-, 2^-$and $3^+$ isomers is obtained with forces SLy4 and SLy6. The disputed $8^-$ isomer in $^{254}$No is assigned as neutron two-quasiparticle configuration $nn[734\uparrow,613\uparrow]$. The isomers are additionally analyzed using Skyrme functionals UNEDF1, UNEDF2 and UNEDF1$^{\rm SO}$. At the energies 1.2 - 1.4 MeV, the 2qp $K$-isomers $4^-, 7^-$ in $^{252}$No and $4^-, 6^-, 7^-$ in $^{254}$No are also predicted. In $^{254}$No, the $K^π=3^+$ isomer should be accompanied by the nearby $K^π=4^+$ counterpart. It is shown that, in the chain $^{250-262}$No, some features of $^{252}$No and $^{254}$No should exhibit essential irregularities caused by a noticeable shell gap in the neutron single-particle spectrum and corresponding reduction of the neutron pairing. In particular, low-energy pairing-vibrational $K^π=0^+$ states in $^{252,254}$No are predicted.

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arXiv2024

Moments of inertia in light deformed nuclei: pairing and mean-field impacts

The dependence of the moment of inertia $\cal J$ on the pairing and axial quadrupole deformation $β$ in $^{24}$Mg and $^{20}$Ne was investigated. The study is based on quadrupole-constrained calculations with three cranking approaches for $\cal J$ (Inglis-Belyaev, Thouless-Valatin, adiabatic time-dependent Hartree-Fock) and a representative set of Skyrme forces (SVbas, SkM*, SLy6). At variance with macroscopic collective models, the calculations predict the specific regime $d{\cal J}/dβ<0$ at $β\ge 0.5$ ($^{24}$Mg) and $β\ge 0.6$ ($^{20}$Ne), where the pairing breaks down. This regime is explained by two effects: full break up of the pairing and specific evolution of a {\it single} dominant particle-hole (1ph) configuration with $β$. The analysis of experimental data for the ground-state rotational bands in $^{24}$Mg and $^{20}$Ne shows that such regime is possible at low spins.

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