Derya, V. ; Tsoneva, N. ; Aumann, T. ; Bhike, M. ; Endres, J. ; Gooden, M. ; Hennig, A. ; Isaak, J. ; Lenske, H. ; Löher, B. ; Pietralla, N. ; Savran, D. ; Tornow, W. ; Werner, V. ; Zilges, A. (2016)
Decay of quadrupole-octupole 1− states in Ca-40 and Ce-140.
In: Physical Review C, 93 (3)
doi: 10.1103/PhysRevC.93.034311
Artikel, Bibliographie

Kurzbeschreibung (Abstract)

Background: Two-phonon excitations originating from the coupling of two collective one-phonon states are of great interest in nuclear structure physics. One possibility to generate low-lying E1 excitations is the coupling of quadrupole and octupole phonons.

Purpose: In this work, the γ-decay behavior of candidates for the (2+1⊗3−1)1− state in the doubly magic nucleus 40Ca and in the heavier and semimagic nucleus 140Ce is investigated.

Methods: (→γ,γ′) experiments have been carried out at the High Intensity γ-ray Source (HIγS) facility in combination with the high-efficiency γ-ray spectroscopy setup γ3 consisting of HPGe and LaBr3 detectors. The setup enables the acquisition of γ−γ coincidence data and, hence, the detection of direct decay paths.

Results: In addition to the known ground-state decays, for 40Ca the decay into the 3−1 state was observed, while for 140Ce the direct decays into the 2+1 and the 0+2 state were detected. The experimentally deduced transition strengths and excitation energies are compared to theoretical calculations in the framework of EDF theory plus QPM approach and systematically analyzed for N=82 isotones. In addition, negative parities for two J=1 states in 44Ca were deduced simultaneously.

Conclusions: The experimental findings together with the theoretical calculations support the two-phonon character of the 1−1 excitation in the light-to-medium-mass nucleus 40Ca as well as in the stable even-even N=82 nuclei.

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