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


Ralet D., CLEMENT E., Georgiev G., Stuchbery A. E., REJMUND M., VAN ISACKER R., ...More

PHYSICS LETTERS B, vol.797, 2019 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 797
  • Publication Date: 2019
  • Doi Number: 10.1016/j.physletb.2019.134797
  • Journal Name: PHYSICS LETTERS B
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Keywords: AGATA spectrometer, gamma-Ray tracking, VAMOS plus plus spectrometer, Plunger device, Nuclear deformation, Octupole phonon, NUCLEAR-DATA SHEETS, VIBRATIONAL-STATE, EXCITATION, SEARCH, DECAY
  • Istanbul University Affiliated: Yes

Abstract

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 (C) 2019 Published by Elsevier B.V.