Enhanced Electric Dipole Strength for the Weakly Bound States in ^{27}Ne

C Loelius; N Kobayashi; H Iwasaki; D Bazin; J Belarge; P C Bender; B A Brown; R Elder; B Elman; A Gade; M Grinder; S Heil; A Hufnagel; B Longfellow; E Lunderberg; M Mathy; T Otsuka; M Petri; I Syndikus; N Tsunoda; D Weisshaar; K Whitmore

doi:10.1103/PhysRevLett.121.262501

Enhanced Electric Dipole Strength for the Weakly Bound States in ^{27}Ne

Phys Rev Lett. 2018 Dec 28;121(26):262501. doi: 10.1103/PhysRevLett.121.262501.

Authors

C Loelius^{1

2}, N Kobayashi¹, H Iwasaki^{1

2}, D Bazin¹, J Belarge¹, P C Bender¹, B A Brown^{1

2}, R Elder^{1

2}, B Elman^{1

2}, A Gade^{1

2}, M Grinder^{1

2}, S Heil³, A Hufnagel³, B Longfellow^{1

2}, E Lunderberg^{1

2}, M Mathy³, T Otsuka^{1

4

5

6}, M Petri^{3

7}, I Syndikus³, N Tsunoda⁴, D Weisshaar¹, K Whitmore^{1

2}

Affiliations

¹ National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.
² Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA.
³ Institut für Kernphysik, Technische Universität Darmstadt, Darmstadt D64289, Germany.
⁴ Center for Nuclear Study, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku Tokyo, Japan.
⁵ Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku Tokyo, Japan.
⁶ RIKEN Nishina Center, Wako, Saitama 351-0198, Japan.
⁷ Department of Physics, University of York, Heslington, York YO10 5DD, United Kingdom.

PMID: 30636164
DOI: 10.1103/PhysRevLett.121.262501

Abstract

An enhanced low-energy electric dipole (E1) strength is identified for the weakly bound excited states of the neutron-rich isotope ^{27}Ne. The Doppler-shift lifetime measurements employing a combination of the γ-ray tracking array GRETINA, the plunger device, and the S800 spectrograph determine the lower limit of 0.030 e^{2} fm^{2} or 0.052 W.u. for the 1/2^{+}→3/2^{-} E1 transition in ^{27}Ne, representing one of the strongest E1 strengths observed among the bound discrete states in this mass region. This value is at least 30 times larger than that measured for the 3/2^{-} decay to the 3/2_{gs}^{+} ground state. A comparison of the present results to large-scale shell-model calculations points to an important role of core excitations and deformation in the observed E1 enhancement, suggesting a novel example of the electric dipole modes manifested in weakly bound deformed systems.