Results 1 - 10 of 939
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[en] Predictions for the spontaneous pion emission from the nuclear ground state of odd-A parent nuclei are obtained from the spontaneous fission half lives using a fission-like model. (authors)
[en] Magnetic dipole moments of odd-odd lanthanides. Collective model of odd-odd nuclei is applied to predict the magnetic dipole moments, (μ) of odd-odd lanthanides. A simplified version of expression for μ based on diagonalisation of Hamiltonian (subsequent use of eigenvectors to compute μ) is developed for cases of ground state as well as excited states using no configuration mixing and is applied to the cases of odd-odd lanthanides. The formulae applied to the eleven (11) cases of ground states show significant improvement over the results obtained using shell model. Configuration mixing and coriolis coupling is expected to cause further improvement in the results. On comparing the earlier work in this direction the present analysis has clarified that in the expression μ the projection factors have different signs for the case I=Ωp - Ωn and I=Ωn - Ωp, and sign of μ is negative in general in the second case while it is positive in all others of spin projection alignments. Although the general expression holds for excited states as well but in lanthanide region, the experimental reports of magnetic dipole moments of excite states (band heads of higher rational sequences) are not available except in case of five (5) neutron resonance states which cannot be handled on the basis of the present approach with no configuration mixing. Although in the present discussion, the model could not be applied to excited states but the systematics of change in its magnitude with increasing spin at higher rational states is very well understood. The particle part supressed under faster rotation of the nuclear core and thus finally at higher spin I, the value μ is given by μ=gcI (same as in case of even-even nuclei). These systematics are to be verified whenever enough data for higher excited states are available. (author). 11 refs
[en] The strong coupling model was used to investigate the possible regions of stable deformation for the positive parity states of the odd nuclei in the 1fsub(7/2) shell. In strongly deformed nuclei, two regions of stable deformation are obtained. In each nucleus where sufficient experimental data are available, a potential having a positive deformation β approximately 0.20 can reproduce the variation observed for Esub(x) as a function of J(J+1)
[fr]Une recherche systematique de regions de deformation stable, pour les etats de parite positive des noyaux impairs de la couche 1fsub(7/2), a ete entreprise dans le cadre du modele a couplage fort. L'energie totale des noyaux du milieu de la couche presente deux minima prononces (deformation positive et negative). Seule une deformation positive β de l'ordre de 0,20 permet de reproduire le spectre d'energie en J(J+1) de ces noyaux
[en] An odd-mass nucleus has been thought as coupling of a single nucleon in the single-particle orbit with the γ-unstable even-core. To get the properties of such a system, the Collective model Hamiltonian with the Morse potential has been used. Two cases, in which the interaction strength between the nucleon and the core are fixed or deformation dependent, are examined. The excitation energy spectrum and the electric quadrupole transition ratios have been obtained. Then the results have been used to predict the experimental data of the some selected odd-mass nuclei.
[en] The multiphonon method previously developed for a system containing an even number of fermions is extended to the case where this number is odd. Recursion formulas well suited for realistic applications to odd-mass nuclei are given for overlaps and matrix elements of one- and two-body operators
[en] The energy levels of the double-well potential receive, beyond perturbation theory, contributions which are non-analytic in the coupling strength; these are related to instanton effects. For example, the separation between the energies of odd- and even-parity states is given at leading order by the one-instanton contribution. However to determine the energies more accurately multi-instanton configurations have also to be taken into account. We investigate here the two-instanton contributions. First we calculate analytically higher-order corrections to multi-instanton effects. We then verify that the difference between numerically determined energy eigenvalues and the generalized Borel sum of the perturbation series can be described to very high accuracy by two-instanton contributions. We also calculate higher-order corrections to the leading factorial growth of the perturbative coefficients and show that these are consistent with analytic results for the two-instanton effect and with exact data for the first 200 perturbative coefficients. (author). Letter-to-the-editor
[en] The Hartree-Bose-Fermi and the adiabatic approximations are used to derive analytic formulas for the moment of inertia and the decoupling parameter of the interacting boson fermion approximation for deformed systems. These formulas are applied to the SU(3) dynamical symmetry, obtaining perfect agreement with the exact results. (Authors)
[pt]As aproximacoes de Hartree-Bose-Fermi e a adiabatica sao utilizadas para derivar formulas analiticas para o momento de inercia e o parametro de desacoplamento, na aproximacao de interacao boson-fermian (extensao do metodo da aproximacao de interacao para bosons, a nucleos impar-par) para nucleos deformados. As formulas sao aplicadas a simetria dinamica SU(3), obtendo-se perfeita concordancia com os resultados sem aproximacao. (S.D.)
[en] The quantum shape phase transitions in odd-even nuclei are investigated within the intrinsic frame approach to the interacting boson-fermion model. In this work, the case of a single-j fermion coupled to a bosonic core that performs a transition from prolate to oblate shapes is considered. The focus is on the effect of the coupled fermion on the whole system along the transitional path from prolate to oblate shapes, passing through the γ-unstable shape. One could expect that all the magnetic substates of the coupled single-fermion with j=9/2 would be driven by the shape of the bosonic core. However, the present work shows that the odd-fermion follows some unexpected and unique paths. The five-components of the j=9/2 orbital do show quite interesting and diverse behaviour. Two of them move slowly from the prolate to the oblate shape by venturing into the triaxial region and also show γ-softness around their slow shape-changing region. The other three odd-states show sudden jumps from prolate side to oblate side and shape coexistence appears, although one of them is fairly close to γ-instability. These unexpected situations make this shape phase transition worth of investigation and discussion.