arXiv subjects

R. V. Jolos

Publications and source records attributed to R. V. Jolos.

At least 19 recordsLinked to original sources

arXiv2026

Quasiparticle structure and $α$-decay scheme of nuclei along alpha-decay chain of $^{288}$Mc

Recent experiments on $α$-decay of odd-odd superheavy nuclei give an important information on the structure of the low-lying states of these nuclei. For this reason it is interesting to calculate the excitation spectra of these superheavy nuclei and compare the results with the experimental data. The aim of this work is to calculate the excitation energies of the two-quasiparticle states of nuclei belonging to the $α$-decay chain of $^{288}$Mc. The approximation of the noninteracting quasiparticles based on the Woods-Saxon single particle potentials is used. Different sets of deformation parameters are considered. The spectra of the low-lying two-quasiparticle states are calculated. The $α$-decay spectra of nuclei belonging to the $α$-decay chain of $^{288}$Mc are obtained and compared with the experimental data. A possibility of the $E1$ transitions in $^{276}$Mt and $^{272}$Bh following $α$-decay of $^{288}$Mc is considered. It is shown that the E1 transitions in $^{276}$Mt can be related to the transition $π[505]9/2\rightarrowπ[615]11/2$. In $^{272}$Bh the $E1$ transition can be related to the neutron single quasiparticle states.

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arXiv2025

Analysis of correlations between dipole transitions $1^-_1\rightarrow 0^+_1$ and $3^-_1\rightarrow 2^+_1$ based on the collective model

The purpose of the work is to evaluate effect of the isovector dipole and quadrupole-octupole modes coupling on the $B(E1;1^-_1\rightarrow 0^+_1)/B(E1;3^-_1\rightarrow 2^+_1)$ ratio. The Hamiltonian of the phenomenological collective model is used to calculate mixing of the isovector dipole and quadrupole and octupole modes. The effect of the admixture of the giant dipole resonance to the low-lying collective quadrupole and octupole modes is estimated. It is shown that the coupling of the quadrupole and octupole collective modes to giant dipole resonance leads to decrease of the ratio $B(E1;1^-_1\rightarrow 0^+_1)/B(E1;3^-_1\rightarrow 2^+_1)$ relative to the value 7/3 predicted by the pure collective quadrupole-octupole model.

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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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arXiv2025

Investigation of the properties of $1^-_1$ excited states of even-even nuclei

The commissioning of new sources of monochromatic $γ$-quanta will allow obtaining a large amount of new data on low-lying collective states of negative parity of even-even nuclei. The purpose of this work is to derive relations between observables characterizing the low-energy negative parity states in even-even nuclei and to investigate the dependence of E2 transitions between the low-energy collective states in these nuclei on the parity of states. The Hamiltonian of the Collective Model and the fermionic Q-phonon representation of the vectors of collective states are used. Relations between different E1 transition matrix elements are derived and the parity dependence of E2 transitions is investigated. Relations between the observables characterizing the low-lying collective states of both parities in even-even nuclei are obtained, which can be verified using experimental data produced by facilities generating intense monochromatic beams of $γ$-quanta.

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arXiv2025

Excitation energies of $2^+_1$ and $4^+_1$ states of neutron deficient U and Pu isotopes

The microscopic variant of the Grodzins relation and the Quasiparticle Phonon Model are applied to predict the excitation energies of the $2^+_1$ states of neutron deficient U and Pu isotopes. The P-factor systematics is used to determine the quadrupole deformation of nuclei under consideration. The excitation energies of the $4^+_1$ states are predicted based on the simple universal anharmonic vibrator type relation.

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arXiv2024

Influences of ${Z=100}$ and ${N=152}$ deformed shells on ${ K^π=8^{-} }$ isomers and rotational bands in ${N = 150}$ isotones

The $K^π=8^{-}$ isomeric states and rotational bands in the even-even $N = 150$ isotones with $94 \leqslant Z \leqslant 104$ are investigated by the cranked shell model (CSM) with pairing correlations treated by the particle-number-conserving (PNC) method. The experimental bandhead energies and kinematic moments of inertia (MOIs) are reproduced quite well by the PNC-CSM calculation. The two-neutron state with configuration $ν9/2^{-}[734] \otimes ν7/2^{+}[624]$ is the lowest $8^{-}$ state for these isomers. This is a demonstration of the deformed neutron shell at $N=152$. Low-lying two proton $π^{2}8^{-}$($π9/2^{+}[624] \otimes π7/2^{-}[514]$) configuration state is predicted only for $^{252}$No and $^{254}$Rf due to the deformed proton shell at $Z=100$. A distinct upbending is observed for the $ν^{2}8^{-}$ bands in the lighter isotones while it is absent for bands in the heavier ones. The upbending of the $ν^{2}8^{-}$ band at frequency $\hbarω\approx 0.20$ MeV in $^{244}$Pu attributes to the sudden proton alignment of the interference term $j_x(\pi5/2^{+}[642]\otimes\pi7/2^{+}[633])$. The irregularity of MOI observed in the $K^π=8^{-}$ band of $^{252}$No can be explained by the mixing of the $ν^{2}8^{-}$($ν9/2^{-}[734] \otimes ν7/2^{+}[624]$) and $π^{2}8^{-}$($π9/2^{+}[624] \otimes π7/2^{-}[514]$) configurations. The $20\%-30\%$ increase of the bandhead $J^{(1)}$ for the $8^{-}$ bands comparing to the ground-state band is attributed to the $\sim 5\%$ pairing gap reduction of the two-neutron $ν7/2^{+}[624] \otimes ν9/2^{-}[734]$ configuration state comparing to the ground-state band.

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arXiv2022

Coriolis mixing of the K=1 and K=0 mixed symmetry states in the well deformed even-even nuclei

The Coriolis matrix elements responsible for mixing of the $1^+ K=1$ and $1^+ K=0$ states are calculated in the framework of the Quasiparticle Phonon Model for several Gd and Dy isotopes. In many considered cases these matrix elements are equal to several tens of keV and are comparable with energy distances between the mixed levels. The results obtained indicates that Gd isotopes could be more suitable for finding deviations from Alaga rules in M1 transitions from $1^+$ state to the states of the ground band.

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arXiv2021

Evolution of the phenomenologically determined collective potential along the chain of Zr isotopes

The properties of the collective low-lying states of Zr isotopes which include excitation energies and $E2$ reduced transition probabilities indicate that some of these states are mainly spherical and the other are mainly deformed ones. We investigate the properties of the low-lying collective states of $^{92-102}$Zr and their evolution with increase of the number of neutrons based on the five-dimensional Geometrical Quadrupole Collective Model. The quadrupole-collective Bohr Hamiltonian with a potential having spherical and deformed minima, is applied. The relative depth of two minima, height and width of the barrier, rigidity of the potential near both minima are determined so as to achieve the best possible description of the observed properties of the low-lying collective quadrupole states of $^{92-102}$Zr. Satisfactory agreement with the experimental data on the excitation energies and the $E2$ reduced transition probabilities is obtained. The evolution of the collective potential with increase of $A$ is described and the distributions of the wave functions of the collective states in $β-γ$ plane are found. The resulting potential evolves with $A$ increase from having only one spherical minimum in $^{92}$Zr, through the potentials having both spherical and deformed minima, to the potential with one deformed minimum in $^{102}$Zr.

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arXiv2021

Influence of triaxiality on the description of low-energy excitation spectrum of $^{96}$Zr

The observed properties of the low-lying collective states of $^{96}$Zr are investigated within the geometrical collective model. The quadrupole-collective Bohr Hamiltonian with the potential having spherical and axially-symmetric deformed minima is applied. The role of triaxiality is investigated by rotating the potential in $γ$-degree of freedom so that the deformed minimum occurs at various axially asymmetric shapes. The change of excitation energies and reduced matrix elements of quadrupole transitions with increase of triaxiliaty is analyzed.

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arXiv2021

Prediction of the excitation energies of the 2$^+_1$ states for superheavy nuclei based on the microscopically derived Grodzins relation

As the result of synthesis of nuclei with large proton numbers a new region of investigations of the structure of nuclei has been discovered. Due to the recent significant increase in the yield of superheavy nuclei their gamma-spectroscopic studies became possible. The purpose of paper is to predict the excitation energies of the $2^+_1$ states of nuclei with Z$\ge 100$ using the microscopic variant of the Grodzins relation derived based on the geometrical collective model. The excitation energies of the $2^+_1$ states of the even-even nuclei from $^{256}$Fm to $^{296}_{120}$X which differ from each other in the number of $α$-particles are predicted. It is shown that at the beginning of the chain of the studied nuclei the excitation energies of the $2^+_1$ states don't exceed 100 keV. Then $E(2^+_1)$ sharply increases with $A$ and reaches maximum value of $400-500$ keV in $^{284}$Fl or $^{292}$Og.

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arXiv2021

Derivation of the Grodzins relation in collective nuclear model

Basing on the Bohr collective quadrupole Hamiltonian the $A$-dependence of the Grodzins product is derived and the proportionality coefficient for the Grodzins relation is evaluated. The result obtained is in a correspondence with the experimental data.

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arXiv2021

Collective model with isovector pair and alpha-particle type correlations

The collective Hamiltonian including isovector pairing and $α$-particle type correlation degrees of freedom is constructed. The Hamiltonian is applied to description of the relative energies of the ground states of even-even nuclei around $^{56}$Ni. A satisfactory description of the experimental data is obtained. A significant improvement of the agreement with the experimental data compared to our previous calculations is explained by inclusion in the Hamiltonian of the dynamical variables describing $α$-particle type correlations.

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arXiv2020

Isovector pair correlations in analytically solvable models

The eigensolutions of the collective Hamiltonian with different potentials suggested for description of the isovector pair correlations are obtained, analyzed and compared with the experimental energies. It is shown that the isovector pair correlations in nuclei around $^{56}$Ni can be described as anharmonic pairing vibrations. The results obtained indicate the presence of the $α$-particle type correlations in these nuclei and the existence of the interaction different from isovector pairing which also influences on the isospin dependence of the energies.

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arXiv2020

Description of the low-lying collective states of $^{96}$Zr based on the quadrupole-collective Bohr Hamiltonian

Experimental data on $^{96}$Zr indicate coexisting spherical and deformed structures with small mixing amplitudes. Several collective low-lying states and E2 and M1 transitions are observed for this nucleus. The quadrupole-collective Bohr Hamiltonian depending on both $β$ and $γ$ shape variables with a potential having spherical and deformed minima, is applied consideration of these data. The relative depth of two minima, height and width of the barrier, rigidity of the potential near both minima are determined so as to achieve a satisfactory description of the observed properties of the low-lying collective quadrupole states of $^{96}$Zr. Good agreement with the experimental data on the excitation energies, $B(E2)$ and $B(M1; 2^+_2\rightarrow 2^+_1)$ reduced transition probabilities is obtained. It is shown that the low-energy structure of $^{96}$Zr can be described in a satisfactory way within the Geometrical Collective Model with a potential function supporting shape coexistence without other restrictions of its shape. However, the excitation energy of the $2^+_2$ state can be reproduced only if the rotation inertia coefficient is taken by four times smaller than the vibrational one in the region of the deformed well. It is shown also that shell effects are important for the description of the $B(M1; 2^+_2 \rightarrow 2^+_1)$ and $B(M1; 3^+_1 \rightarrow 2^+_1)$ transition probabilities. An indication for the influence of the pairing vibrational mode on the $0^+_2 \rightarrow 0^+_1$ transition is confirmed in agreement with the previous result.

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arXiv2019

Collective treatment of the isovector pair correlations. Boson representation

The theoretical approach to consideration of the Hamiltonian with pairing forces using a technique of the finite boson representation is developed. It is shown that a simultaneous description of the pairing vibrational state in $^{56}$Ni and the pairing rotational states with $T$=0 in the neighboring $N=Z$ nuclei is possible if the pairing Hamiltonian takes into account only isovector monopole pairing. However, the calculated energies of the pairing rotational states of $N=Z$ nuclei removed from $^{56}$Ni by 12 and more nucleons exceed significantly the experimental values. The possible reason of this discrepancy is discussed.

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arXiv2019

Description of shape coexistence in $^{96}$Zr based on the collective quadrupole Bohr Hamiltonian

Experimental data on $^{96}$Zr indicate coexisting spherical and deformed structures with small mixing amplitudes. We investigate the properties of the low-lying collective states of $^{96}$Zr based on the collective quadrupole Bohr Hamiltonian. The $β$-dependent collective potential having two minima -- spherical and deformed, is fixed so to describe experimental data in the best way.Good agreement with the experimental data on the excitation energies, $B(E2)$ and $B(M1)$ reduced transition probabilities is obtained. It is shown that the low-energy structure of $^{96}$Zr can be reproduced in a satisfactory way in the geometrical model with a potential function supporting shape coexistence. However, the excitation energy of the $2^+_2$ state can be reproduced only if the rotation inertia coefficient is taken five times smaller then the vibrational one in the region of the deformed well. It is shown also that shell effects are important for the description of the $B(M1;2^+_2 \rightarrow 2^+_1)$ value. An indication on the influence of the pairing vibrational mode on the $ρ^2 (0^+_2 \rightarrow 0^+_1)$ value is obtained.

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arXiv2018

Analytical description of the excited state phase transition to octupole deformed shape in alternating parity bands

Angular momentum dependences of the parity splitting and electric dipole transitions in the alternating parity bands of heavy nuclei have been analyzed. It is shown that these dependences can be treated in a universal way with a single parameter of critical angular momentum, which characterizes phase transition from octupole vibrations to the stable octupole deformation. Using the simple but useful model of axially-symmetric reflection-asymmetric mode, the analytical expression for the parity splitting and electric dipole transitional moment have been obtained. The results obtained are in a good agreement with the experimental data for various isotopes of Ra, Th, U, and Pu.

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arXiv2017

Kinetic energy in the collective quadrupole Hamiltonian from the experimental data

Dependence of the kinetic energy term of the collective nuclear Hamiltonian on collective momentum is considered. It is shown that the fourth order in collective momentum term of the collective quadrupole Hamiltonian generates a sizable effect on the excitation energies and the matrix elements of the quadrupole moment operator. It is demonstrated that the results of calculation are sensitive to the values of some matrix elements of the quadrupole moment. It stresses the importance for a concrete nucleus to have the experimental data for the reduced matrix elements of the quadrupole moment operator taken between all low lying states with the angular momenta not exceeding 4.

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