arXiv subjects

N. Minkov

Publications and source records attributed to N. Minkov.

79 records · Page 5Linked to original sources

arXiv2001

Delta I = 1 staggering in octupole bands of light actinides: "Beat" patterns

The Delta I = 1 staggering (odd--even staggering) in octupole bands of light actinides is found to exhibit a ``beat'' behaviour as a function of the angular momentum I, forcing us to revise the traditional belief that this staggering decreases gradually to zero and then remains at this zero value. Various algebraic models (spf-Interacting Boson Model, spdf-IBM, Vector Boson Model, Nuclear Vibron Model) are shown to predict in their su(3) limits constant staggering for this case, being thus unable to describe the ``beat'' behaviour. An explanation of the ``beat'' behaviour is given in terms of two Dunham expansions (expansions in terms of powers of I(I+1)) with slightly different sets of coefficients for the ground state band and the negative parity band, the difference in the values of the coefficients being attributed to Coriolis couplings to other negative parity bands. Similar ``beat'' patterns have already been seen in rotational bands of some diatomic molecules, like AgH.

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arXiv2001

Symmetries and staggering effects in nuclear rotational spectra

We study the fine structure of nuclear rotational spectra on the basis of both dynamical and discrete symmetry approaches. In this framework we show that the odd--even (Delta I = 1) staggering effects observed in various rotational bands carry detailed information about the collective band-mixing interactions and the collective shape properties of heavy nuclei.

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arXiv1997

Broken SU(3) symmetry in deformed even-even nuclei

A collective vector-boson model with broken SU(3) symmetry, in which the ground state band and the lowest $γ$ band belong to the same irreducible representation but are non-degenerate, is applied to several deformed even-even nuclei. The model description of ground and $γ$ bands together with the corresponding B(E2) transition probabilities is investigated within a broad range of SU(3) irreducible representations $(λ,μ)$. The calculations show that the $(λ,μ)$ characteristics of rotational nuclei depend to a great extent on the magnitude of the SU(3) splitting between the ground and $γ$ bands. It is found that for weakly split spectra, the ground--$γ$ band coupling scheme is realized relevantly within narrow regions of ``favored'' $(λ,μ)$ multiplets, while in the cases of strong splitting a description in which the ground band is situated alone in an irreducible representation is favored. The obtained results are analyzed in terms of the bandmixing interactions. The possibility for a transition between the different collective SU(3) schemes is discussed.

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arXiv1997

Symmetries in nuclei and molecules

Recent progress in two different fronts is reported. First, the concept of bisection of a harmonic oscillator (HO) or hydrogen atom (HA), used in the past in establishing the connection between U(3) and O(4), is generalized into multisection (trisection, tetrasection, etc). It is then shown that all symmetries of the N-dim anisotropic HO with rational ratios of frequencies (RHO), some of which are underlying the structure of superdeformed and hyperdeformed nuclei, can be obtained from the U(N) symmetry of the corresponding isotropic HO with an appropriate combination of multisections. Furthermore, it is seen that bisections of the N-dim HA, which possesses an O(N+1) symmetry, lead to the U(N) symmetry, so that further multisections of the HA lead to the symmetries of the N-dim RHO. Second, it is shown that there is evidence that the recently observed in superdeformed nuclear bands $ΔI=4$ bifurcation is also occuring in rotational bands of diatomic molecules. In addition there is evidence that a $ΔI=8$ bifurcation, of the same order of magnitude as the $ΔI=4$ one, is observed in superdeformed nuclear bands and rotational bands of diatomic molecules.

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arXiv1997

Investigations of the broken SU(3) symmetry in deformed even-even nuclei

A collective vector-boson model with broken SU(3) symmetry is applied to several deformed even-even nuclei. The model description of ground and $γ$ bands together with the corresponding B(E2) transition probabilities is investigated within a broad range of SU(3) irreducible representations (irreps) $(λ,μ)$. The SU(3)-symmetry characteristics of rotational nuclei are analyzed in terms of the bandmixing interactions.

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arXiv1996

$ΔI=4$ and $ΔI=8$ bifurcations in rotational bands of diatomic molecules

It is shown that the recently observed $ΔI=4$ bifurcation seen in superdeformed nuclear bands is also occurring in rotational bands of diatomic molecules. In addition, signs of a $ΔI=8$ bifurcation, of the same order of magnitude as the $ΔI=4$ one, are observed both in superdeformed nuclear bands and rotational bands of diatomic molecules.

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arXiv1996

Nuclear $β$- and $γ$- Collective Bands in the SU$_q$(2) Rotator Model

The SU$_q$(2) rotator model is used for describing the $β_1$- and $γ_1$-bands of even-even rare earth and actinide collective nuclei. Good results are obtained in nuclei with valence pair number $N>10$. It is shown that in the excited bands the violation of the exact SU(2) symmetry is generally stronger than in the ground state bands, indicating the presence of a nonadiabatic perturbation caused by the excited vibrational degrees of freedom. The physical content of the parameter $q$ is discussed. Predictions of the SU$_q$(2) model for B(E2) intraband transitions in excited bands are presented and the need for specific experimental data is pointed out.

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