Bulg. J. Phys. vol.44 no.4 (2017), pp. 478-488

Introduction of Fermion Degrees of Freedom in IVBM for the Description of Spectra of Odd Nuclei

V.P. Garistov1, A.I. Georgieva2
1Institute of Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria
2Institute of Electronics, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria
Abstract. A very accurate results for the energy spectra of the even-even nuclei have been obtained in a new more physical application of the dynamical symmetry: Sp(12,R) ⊃ U(6) ⊃ U(3) ⊗ U(2) ⊃ O(3) ⊗ (U(1) ⊗ U(1)) of the Interacting Vector Boson Model (IVBM). The description of odd-mass nuclei requires the introduction of fermion degrees of freedom, that we make through the total moment I = ln + sn for a single fermion n coupled to the angular momentum L of the states of the ground and octupole bands of the even-even core J = L + I. From an algebraic point of view, this can be presented as an extension of the dynamical symmetry group Sp(12,R) of the IVBM to the orthosymplectic group OSp(2Ω/12,R), which contains the direct product of SOF(2Ω) of the fermion degrees of freedom and the boson part SpB(12,R) describing the even-even system. The approach can be extended for the description of the spectra of odd-odd nuclei as well. The results are illustrated by the comparison of the theory with the experimental spectra of the ground and octupole bands ot the even-even nuclei 236U and 238Pu and the long collective bands build on them in the odd 237U and 239Pu.

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