TY - JOUR

T1 - Energy systematics of low-lying [Formula Presented] states in neutron-deficient Ba nuclei

AU - Asai, M.

AU - Sekine, T.

AU - Osa, A.

AU - Koizumi, M.

AU - Kojima, Y.

AU - Shibata, M.

AU - Yamamoto, H.

AU - Kawade, K.

PY - 1997

Y1 - 1997

N2 - Low-spin states in [Formula Presented] fed by the [Formula Presented] decay of their La parents have been investigated by means of the γ-γ angular correlation measurement coupled with an isotope separator on-line. The spin of the first excited [Formula Presented] states [Formula Presented] were unambiguously established, and higher-excited [Formula Presented] states were newly identified. The energy of the [Formula Presented] state in [Formula Presented] previously assigned was revised upward. Resultingly, the level energy of the [Formula Presented] state in neutron-deficient Ba nuclei takes a minimum at [Formula Presented] and then gradually increases toward neutron midshell [Formula Presented] while the level energy of the [Formula Presented] state rapidly decreases with decreasing neutron number. From an extrapolation of these [Formula Presented] energies, it is highly expected that the energy relation between the [Formula Presented] and [Formula Presented] state would invert at [Formula Presented] or at more deformed Ba nuclei. This energy inversion is interpreted as the evolution of the [Formula Presented] state in γ-soft nuclei toward the two-phonon γ-vibrational [Formula Presented] state in axially-symmetric deformed nuclei, while the [Formula Presented] state toward the β-vibrational [Formula Presented] state.

AB - Low-spin states in [Formula Presented] fed by the [Formula Presented] decay of their La parents have been investigated by means of the γ-γ angular correlation measurement coupled with an isotope separator on-line. The spin of the first excited [Formula Presented] states [Formula Presented] were unambiguously established, and higher-excited [Formula Presented] states were newly identified. The energy of the [Formula Presented] state in [Formula Presented] previously assigned was revised upward. Resultingly, the level energy of the [Formula Presented] state in neutron-deficient Ba nuclei takes a minimum at [Formula Presented] and then gradually increases toward neutron midshell [Formula Presented] while the level energy of the [Formula Presented] state rapidly decreases with decreasing neutron number. From an extrapolation of these [Formula Presented] energies, it is highly expected that the energy relation between the [Formula Presented] and [Formula Presented] state would invert at [Formula Presented] or at more deformed Ba nuclei. This energy inversion is interpreted as the evolution of the [Formula Presented] state in γ-soft nuclei toward the two-phonon γ-vibrational [Formula Presented] state in axially-symmetric deformed nuclei, while the [Formula Presented] state toward the β-vibrational [Formula Presented] state.

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U2 - 10.1103/PhysRevC.56.3045

DO - 10.1103/PhysRevC.56.3045

M3 - Article

AN - SCOPUS:0031329548

VL - 56

SP - 3045

EP - 3053

JO - Physical Review C - Nuclear Physics

JF - Physical Review C - Nuclear Physics

SN - 0556-2813

IS - 6

ER -