arXiv subjects

P. Van Isacker

Publications and source records attributed to P. Van Isacker.

79 records · Page 5Linked to original sources

arXiv2000

Anharmonic double-$γ$ vibrations in nuclei and their description in the interacting boson model

Double-$γ$ vibrations in deformed nuclei are studied in the context of the interacting boson model with special reference to their anharmonic character. It is shown that large anharmonicities can be obtained with interactions that are (at least) of three-body nature between the bosons. As an example the $γ$ vibrations of the nucleus $^{166}_{\phantom{0}68}$Er$^{\phantom{00}}_{98}$ are studied in detail.

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arXiv1999

Excitation of multiple giant dipole resonances: from spherical to deformed nuclei

The effect of deformation on the excitation of multiple giant dipole resonances is studied. Analytical expressions are derived in the framework of the interacting boson model for the energies and E1 properties of giant dipole resonances in spherical and deformed nuclei, and a numerical treatment of transitional nuclei is proposed. Coulomb-excitation cross sections are calculated in $^{238}$U and in the samarium isotopes.

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arXiv1998

The interacting boson model with SU(3) charge symmetry and its application to even--even N $\approx$ Z nuclei

The isospin-invariant interacting boson model IBM-3 is analyzed in situations where $SU_T(3)$ charge symmetry [or, equivalently, $U_L(6)$ $sd$ symmetry] is conserved. Analytic expressions for energies, electromagnetic transitions, two-nucleon transfer probabilities, and boson-number expectation values are obtained for the three possible dynamical symmetry limits, U(5), SU(3), and O(6). Results found in IBM-3 are related to corresponding ones in IBM-1 and IBM-2. Numerical calculations are presented for $f_{7/2}$-shell nuclei and some features that distinguish IBM-3 from its predecessors IBM-1 and IBM-2 are pointed out.

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arXiv1998

Intrinsic structure of two-phonon states in the interacting boson model

A general study of excitations up to two-phonon states is carried out using the intrinsic-state formalism of the Interacting Boson Model (IBM). Spectra and transitions for the different dynamical symmetries are analyzed and the correspondence with states in the laboratory frame is established. The influence of multi-phonon states is discussed. The approach is useful in problems where the complexity of the IBM spectrum renders the analysis in the laboratory frame difficult.

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arXiv1997

A Hartree-Bose Mean-Field Approximation for IBM-3

A Hartree-Bose mean-field approximation for the IBM-3 is presented. A Hartree- Bose transformation from spherical to deformed bosons with charge-dependent parameters is proposed which allows bosonic pair correlations and includes higher angular momentum bosons. The formalism contains previously proposed IBM-2 and IBM-3 intrinsic states as particular limits.

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arXiv1997

Analytically Solvable Mean-Field Potential for Stable and Exotic Nuclei

Slater determinants built from the single-particle wave functions of the analytically solvable Ginocchio potential are used to approximate the self-consistent Hartree-Fock solutions for the ground states of nuclei. The results indicate that the Ginocchio potential provides a good parametrization of the nuclear mean field for a wide range of nuclei, including those at the limit of particle stability.

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arXiv1995

Sum Rules for B(M1,0+ -> 1+) Strength in IBM-3 and IBM-4

Sum rules for $B(M1,0^+_1\rightarrow1^+_i)$ strength are derived for even-even nuclei in the isospin-invariant forms of the IBM, IBM-3 and IBM-4, in the cases where the respective natural internal symmetries, isospin $U$(3) and $U(6)\supset SU$(4), are conserved. Subsequently, the total strength is resolved into its component partial sums to the allowed isospins (and $SU(4)$ representations in IBM-4). In cases where the usual IBM dynamical symmetries are also valid, a complete description of all $B(M1,0^+_1\rightarrow1^+_i)$ is given. In contrast to IBM-2, there is fragmentation of the strength even in the dynamical symmetry cases, for $T\neq 0$, over two states in IBM-3, and over three states in IBM-4. The presence of $pn$ bosons in the ground state of the extended versions reduces the expected strength from that for IBM-2, allowing in principle the possibility of using $B(M1)$ data for a given nucleus to infer which version is the most appropriate.

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