arXiv subjects

V. V. Voronov

Publications and source records attributed to V. V. Voronov.

33 records · Page 2Linked to original sources

arXiv2007

Effects of the particle-particle channel on properties of low-lying vibrational states

Making use of the finite rank separable approach for the quasiparticle random phase approximation enables one to perform nuclear structure calculations in very large two-quasiparticle spaces. The approach is extended to take into account the residual particle-particle interaction. The calculations are performed by using Skyrme interactions in the particle-hole channel and density-dependent zero-range interactions in the particle-particle channel. To illustrate our approach, we study the properties of the lowest quadrupole states in the even-even nuclei $^{128}$Pd, $^{130}$Cd, $^{124-134}$Sn, $^{128-136}$Te and $^{136}$Xe.

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arXiv2006

Ground state correlations and structure of odd spherical nuclei

It is well known that the Pauli principle plays a substantial role at low energies because the phonon operators are not ideal boson operators. Calculating the exact commutators between the quasiparticle and phonon operators one can take into account the Pauli principle corrections. Besides the ground state correlations due to the quasiparticle interaction in the ground state influence the single particle fragmentation as well. In this paper, we generalize the basic QPM equations to account for both mentioned effects. As an illustration of our approach, calculations on the structure of the low-lying states in $^{131}$Ba have been performed.

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arXiv2006

Pseudospin symmetry and structure of nuclei with $Z\ge$ 100

In the framework of the Relativistic Mean Field Approach a pseudospin dependence of the residual forces in nuclei is considered. It is shown that this dependence is relatively weak. As a consequence, a pseudospin dependence of the particle--core coupling is weak as well. This leads to a small splitting of the pseudospin doublets produced by a vector coupling of an odd particle pseudospin and a pseudo--orbital momentum of the core. Some possibilities for experimental investigations of the manifestations of the pseudospin symmetry in the spectra of odd nuclei with $Z\ge$ 100 are indicated.

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arXiv2006

On neutron number dependence of B(E1;0+ --> 1-) reduced transition probability

A neutron number dependence of the E1 0+ --> 1- reduced transition probability in spherical even--even nuclei is analysed within the Q--phonon approach in the fermionic space to describe the structure of collective states. Microscopic calculations of the E1 0+ --> 1- transition matrix elements are carried out for the Xe isotopes based on the RPA for the ground state wave function. A satisfactory description of the experimental data is obtained.

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arXiv2004

Q-phonon description of low lying 1^- two-phonon states in spherical nuclei

The properties of 1^-_1 two-phonon states and the characteristics of E1 transition probabilities between low-lying collective states in spherical nuclei are analysed within the Q-phonon approach to the description of collective states. Several relations between observables are obtained. Microscopic calculations of the E1 0^+_1 -> 1^-_1 transition matrix elements are performed on the basis of the RPA. A satisfactory description of the experimental data is obtained.

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arXiv2004

Effects of phonon-phonon coupling on low-lying states in neutron-rich Sn isotopes

Starting from an effective Skyrme interaction we present a method to take into account the coupling between one- and two-phonon terms in the wave functions of excited states. The approach is a development of a finite rank separable approximation for the quasiparticle RPA calculations proposed in our previous work. The influence of the phonon-phonon coupling on energies and transition probabilities for the low-lying quadrupole and octupole states in the neutron-rich Sn isotopes is studied.

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arXiv2003

Nuclear structure calculations with a separable approximation for Skyrme interactions

A finite rank separable approximation for the quasiparticle RPA calculations with Skyrme interactions that was proposed in our previous work is extended to take into account the coupling between one- and two-phonon terms in the wave functions of excited states. It is shown that characteristics calculated within the suggested approach are in a good agreement with available experimental data.

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arXiv2002

Separabelized Skyrme Interactions and Quasiparticle RPA

A finite rank separable approximation for the quasiparticle RPA with Skyrme interactions is applied to study the low lying quadrupole and octupole states in some S isotopes and giant resonances in some spherical nuclei. It is shown that characteristics calculated within the suggested approach are in a good agreement with available experimental data.

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arXiv2002

Quasiparticle RPA with finite rank approximation for Skyrme interactions

A finite rank separable approximation for the particle-hole RPA calculations with Skyrme interactions is extended to take into account the pairing. As an illustration of the method energies and transition probabilities for the quadrupole and octupole excitations in some O, Ar, Sn and Pb isotopes are calculated. The values obtained within our approach are very close to those that were calculated within QRPA with the full Skyrme interaction. They are in reasonable agreement with experimental data.

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arXiv2001

Description of Double Giant Dipole Resonance within the Phonon Damping Model

In a recent Letter [1] an overall agreement with the experimental data for the excitation of the single and double giant dipole resonances in relativistic heavy ion collision in 136Xe and 208Pb nuclei has been reported. We point out that this agreement is achieved by a wrong calculation of the DGDR excitation mechanism. We also argue that the agreement with the data for the widths of resonances is achieved by an unrealistically large value of a model parameter. [1] Nguyen Dinh Dang, Vuong Kim Au, and Akito Arima, Phys. Rev. Lett. 85 (2000) 1827.

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arXiv2000

Ground state correlations and anharmonicity of vibrations

A consistent treatment of the ground state correlations beyond the random phase approximation including their influence on the pairing and phonon-phonon coupling in nuclei is presented. A new general system of nonlinear equations for the quasiparticle phonon model (QPM) is derived. It is shown that this system contains as a particular case all equations derived for the QPM early. New additional Pauli principle corrections resulting in the anharmonical shifts of energies of the two-phonon configurations are found. A correspondence between the generalized QPM equations and the nuclear field theory is discussed.

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arXiv2000

Anharmonic properties of double giant dipole resonance

A systematic microscopic study of the anharmonic properties of the double giant dipole resonance (DGDR) has been carried out, for the first time, for nuclei with mass number $A$ spanning the whole mass table. It is concluded that the corrections of the energy centroid of the $J^π = 0^+$ and $2^+$ components of the DGDR from its harmonic limit are negative, have a value of the order of few hundred keV and follow an $A^{-1}$ dependence.

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arXiv2000

Proton decay of high-lying states in odd nuclei

In the framework of the quasiparticle-phonon model, we study the non-statistical proton decay of excited states in odd nuclei towards low-lying collective states. Partial cross sections and branching ratios for the proton decay of the high angular momentum states in $^{41}$Sc, $^{59}$Cu and $^{91}$Nb %{\it excited by means of the ($^{7}$Li,$^{6}$He) reaction} are evaluated. The calculated branching ratios predict strong direct proton decays to the low-lying vibrational states in $^{41}$Sc and $^{91}$Nb. A general agreement with existing experimental data is found.

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arXiv1998

Effects of the ground state correlations on the structure of vibrational states

A method to treat the ground state correlations beyond the RPA is presented. A set of nonlinear equations taking into account effects of the ground state correlations on the pairing and phonon-phonon coupling is derived. The influence of such correlations on properties of the vibrational states in spherical nuclei is studied.

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arXiv1996

Quenching of $1^+$ excitations in the double giant resonance

The electromagnetic excitation of the two-phonon isovector giant dipole resonance in relativistic projectiles incident on heavy targets can be proceed via several intermediate $1^-$ one-phonon giant resonance states. In two step electric dipole transitions the population of $0^+$, $1^+$, and $2^+ $ two-phonon states are possible. We calculate the amplitude distribution of $1^-$ excitations with an RPA formalism, and use it to calculate the electromagnetic excitation of two-phonon states in second order perturbation theory and coupled-channels. We show that a conspiracy between angular momentum coupling and the strength of the electromagnetic fields suppresses contributions of $1^+$ states to the total cross sections.

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