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The effective field theory (EFT) for triaxially deformed even-even nuclei is generalized to include the vibrational degrees of freedom. The pertinent Hamiltonian is constructed up to next-to-leading order (NLO). The leading-order part describes the vibrational motion, and the NLO part couples rotations to vibrations. The applicability of the EFT Hamiltonian is examined through the description of the energy spectra of the ground state bands, γ bands, and K=4 bands in the 108,110,112Ru isotopes. It is found that, by taking into account the vibrational degrees of freedom, the deviations for high-spin states in the γ band observed in the EFT with only rotational degrees of freedom disappear. This supports the importance of including vibrational degrees of freedom in the EFT formulation for the collective motion of triaxially deformed nuclei. [ABSTRACT FROM AUTHOR]

Background: Triaxiality in nuclear low-lying states has attracted great interest for many years. Recently, reduced transition probabilities for levels near the ground state in 110Ru have been measured and provided strong evidence of a triaxial shape of this nucleus. Purpose: The aim of this work is to provide a microscopic study of low-lying states for Ru isotopes with A≈100 and to examine in detail the role of triaxiality and the evolution of quadrupole shapes with the isospin and spin degrees of freedom. Method: Low-lying excitation spectra and transition probabilities of even-even Ru isotopes are described at the beyond-mean-field level by solving a five-dimensional collective Hamiltonian with parameters determined by constrained self-consistent mean-field calculations based on the relativistic energy density functional PC-PK1. Results: The calculated energy surfaces, low-energy spectra, and intraband and interband transition rates, as well as some characteristic collective observables, such as E(4+g.s.)/E(2+g.s.),E(2+γ)/E(4+g.s.), and B(E2;2+g.s.→0+g.s.) and γ-band staggerings, are in good agreement with the available experimental data. Conclusions: The main features of the experimental low-lying excitation spectra and electric transition rates are well reproduced and, thus, strongly support the onset of triaxiality in the low-lying excited states of Ru isotopes around 110Ru. [ABSTRACT FROM AUTHOR]

The 98Ru nucleus, populated via the 97Mo(³He,2n) reaction, has been investigated by means of K-internal conversion coefficient, γ-ray angular distribution, γ-γ coincidence, and γ-γ angular correlation measurements. The results have led to an improved knowledge of the excitation energy pattern via the identification of new levels and transitions. New information on spin and parities of many levels as well as on mixing ratios of several transitions has been obtained. The presence of large M1 components in many transitions definitely excludes the possibility of considering 98 as a nucleus having a structure very close to the vibrational one and points to the need of an enlarged framework for a successful description. [ABSTRACT FROM AUTHOR]

Low-lying states of even-even and odd-mass ruthenium isotopes with mass numbers from 95 to 102, including level schemes, electric quadrupole and magnetic dipole moments, and E2 transition rates, are studied within the framework of the nucleon pair approximation (NPA) of the shell model, by using the phenomenological pairing plus quadrupole interactions. Good agreement is obtained between the calculated results and experimental data. The interesting behaviors of g(J1+) factors versus nuclear spin J (and mass number A) in even-even 96-102Ru nuclei are analyzed. The dominant configurations of yrast low-lying states in odd-mass 95-101Ru isotopes are discussed in the collective nucleon-pair subspace. The calculated electric quadrupole moments and magnetic moments of low-lying states, many of which have not yet been measured for these nuclei, are useful for future studies. [ABSTRACT FROM AUTHOR]

The structure of the low-lying states in the odd- and even-mass A≈100 Ru isotopes is studied in the framework of two algebraic models. The even-mass Ru nuclei are first described within the interacting boson model 1 (IBM-1). The output of these calculations was then used to calculate the odd-A isotopes within the interacting boson-fermion model 1 (IBFM-1), where a coupling of the odd neutron to the even-even core is considered. The level energies and transition probabilities calculated in the present work are tested against the experimental data. One-nucleon transfer spectroscopic factors as well as electromagnetic moments were also calculated for the odd-A Ru and compared to the experimental values. The transitional character of the isotopes is studied. Most of the low-lying positive-parity states in the odd-A Ru nuclei below 2 MeV are interpreted on the basis of νd5/2 and νg7/2 configurations. The role of the νs1/2 orbital in the nuclear structure of the odd-mass Ru nuclei at low energies is also studied. The negative-parity states are interpreted as νh11/2 excitations coupled to the core. The evolution of the IBM-1 and IBFM-1 parameters is discussed. [ABSTRACT FROM AUTHOR]