Abstract
Inspired by the recent experimental data [J.-G. Wang, et al., Phys. Lett. B 675 (2009) 420], we extend the triaxial projected shell model approach to study the γ-band structure in odd-mass nuclei. As a first application of the new development, the γ-vibrational structure of 103Nb is investigated. It is demonstrated that the model describes the ground-state band and multi-phonon γ-vibrations quite satisfactorily, supporting the interpretation of the data as one of the few experimentally-known examples of simultaneous occurrence of one- and two-γ-phonon vibrational bands. This generalizes the well-known concept of the surface γ-oscillation in deformed nuclei built on the ground-state in even–even systems to γ-bands based on quasiparticle configurations in odd-mass systems.
Highlights
Theoretical investigations using quasiparticle-phonon nuclear model (QPNM) [8,9] predicted that γγ-vibrational bands cannot exist in deformed nuclei due to Pauli blocking of quasiparticle components
The multi-phonon method (MPM) [10,11] suggested that a two-phonon Kπ = 4+ state should appear at an excitation energy of about 2.6 times the energy of the one-phonon Kπ = 2+ state, and the decay from the γγ- to γ-band should be predominantly collective in character
Due to the violation of rotational symmetry, these methods do not calculate the states of angular-momentum, but the K states
Summary
Ellipsoidal oscillation of the shape is commonly termed γ-vibration [1]. Rotational bands based on the γ-vibrational states are known as γ-bands. [12] that the angular-momentum-projection on these K = 0, 2 and 4 vacuum states generates the low-spin parts of the ground, γ-, and γγband, respectively This is a pleasant feature of the TPSM that the quantummechanical treatment of angular-momentum-projection on the (triaxially deformed) quasiparticle vacuum alone gives rise to rotational ground band and multiphonon γ-vibrational bands. This simple configuration [12] is valid only for low-spin states because if the system goes to high spins, rotational alignment will bring various quasiparticle configurations down to the yrast region, and the quasiparticle excitations must be considered. For the study of odd-proton system, our model space is spanned by (angularmomentum-projected) one- and three-qp basis
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