Browsing by Author "Chen, Q. B."

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    Effective field theory for collective rotations and vibrations of triaxially deformed nuclei
    (American Physical Society, 2018) Chen, Q. B.; Kaiser, N.; Meibner, Ulf G.; Meng, Jie
    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.
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    Multiple chiral doublets in four-j shells particle rotor model : five possible chiral doublets in ¹³⁶₆₀Nd₇₆
    (Elsevier, 2018) Chen, Q. B.; Lv, B. F.; Petrache, C. M.; Meng, Jie
    A particle rotor model, which couples nucleons in four single-jshells to a triaxial rotor core, is developed to investigate the five pairs of nearly degenerate doublet bands recently reported in the even-even nucleus 136Nd. The experimental energy spectra and available B(M1)/B(E2)values are successfully reproduced. The angular momentum geometries of the valence nucleons and the core support the chiral rotation interpretations not only for the previously reported chiral doublet, but also for the other four candidates. Hence, 136Nd is the first even-even candidate nucleus in which the multiple chiral doublets exist. Five pairs of chiral doublet bands in a single nucleus is also a new record in the study of nuclear chirality.
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    Reexamining nuclear chiral geometry from the orientation of the angular momentum
    (American Physical Society, 2018) Chen, Q. B.; Meng, Jie
    The paradox on the previous interpretation for the nuclear chiral geometry based on the effective angle has been clarified by reexamining the system with the particle-hole configuration π(1h11/2)1⊗ν(1h11/2)−1 and a rotor with the deformation parameter γ=30∘. It is found that the paradox is caused by the fact that the angular momentum of the rotor is much smaller than those of the proton and the neutron near the bandhead. Hence, it does not support a chiral rotation interpretation near the bandhead. The nuclear chiral geometry based on the effective angle makes sense only when the angular momentum of the rotor becomes comparable with those of the proton and neutron for a particular range of spin values.
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    “Stapler” mechanism for a dipole band in 79Se
    (American Physical Society, 2019-10-24) Li, C. G.; Chen, Q. B.; Zhang, S. Q.; Xu, C.; Hua, H.; Wang, S. Y.; Bark, R. A.; Wyngaardt, S. M.; Shi, Z.; Dai, A. C.; Wang, C. G.; Li, X. Q.; Li, Z. H.; Meng, J.; Xu, F. R.; Ye, Y. L.; Jiang, D. X.; Han, R.; Niu, C. Y.; Chen, Z. Q.; Wu, H. Y.; Wang, X.; Luo, D. W.; Wu, C. G.; Wang, S.; Sun, D. P.; Liu, C.; Li, Z. Q.; Sun, B. H.; Jones, P.; Msebi, L.; Sharpey-Schafer, J. F.; Dinoko, T.; Lawrie, E. A.; Ntshangase, S. S.; Kheswa, B. V.; Shirinda, O.; Khumalo, N.; Bucher, T. D.; Malatji, K. L.
    The spectroscopy of 79 Se is studied via the 82 Se(α, α3n)79Se fusion-evaporation reaction. A negative-parity magnetic dipole band in 79Se is established for the first time. Based on the calculations by the self-consistent tilted axis cranking covariant density functional theory, this new dipole band can be classified as a “stapler” band, which has a relatively stable symmetric prolate deformation as a function of rotational frequency. Hence, it is demonstrated that the stapler bands exist not only in the oblate and triaxial nuclei, but also in prolate nuclei. By examining the angular momentum coupling, it is found that the five valence nucleons in the high-j orbitals play a major role in the closing of the stapler.