Evidence of octupole-phonons at high spin in Pb-207

A lifetime measurement of the 19/2(-) state in Pb-207 has been performed using the Recoil Distance Doppler-Shift (RDDS) method. The nuclei of interest were produced in multi-nucleon transfer reactions induced by a Pb-208 beam impinging on a Mo-100 enriched target. The beam-like nuclei were detected...

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Bibliographic Details
Published in:Physics letters. B 2019, Vol.797
Main Authors: Ralet, D., Cederwall, Bo, Wieland, O.
Format: Article
Language:English
Subjects:
AGATA spectrometer
Atomic, Subatomic and Astrophysics
Atomär fysik, subatomär fysik och astrofysik
gamma-Ray tracking
Nuclear deformation
Octupole phonon
Plunger device
VAMOS plus plus spectrometer
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Summary:A lifetime measurement of the 19/2(-) state in Pb-207 has been performed using the Recoil Distance Doppler-Shift (RDDS) method. The nuclei of interest were produced in multi-nucleon transfer reactions induced by a Pb-208 beam impinging on a Mo-100 enriched target. The beam-like nuclei were detected and identified in terms of their atomic mass number in the VAMOS++ spectrometer while the prompt gamma rays were detected by the AGATA tracking array. The measured large reduced transition probability B(E3, 19/2(-) -> 13/2(+)) = 40(8) W.u. is the first indication of the octupole phonon at high spin in Pb-207. An analysis in terms of a particle-octupole-vibration coupling model indicates that the measured B(E3) value in Pb-207 is compatible with the contributions from single-phonon and single particle E3 as well as E3 strength arising from the double-octupole-phonon 6(+) state, all adding coherently. A crucial aspect of the coupling model, namely the strong mixing between single-hole and the phonon-hole states, is confirmed in a realistic shell-model calculation. Crown Copyright B.V.
ISSN:0370-2693
1873-2445
DOI:10.1016/j.physletb.2019.134797