Butler P A, Gaffney L P, Spagnoletti P, Abrahams K, Bowry M, Cederkäll J, de Angelis G, De Witte H, Garrett P E, Goldkuhle A, Henrich C, Illana A, Johnston K, Joss D T, Keatings J M, Kelly N A, Komorowska M, Konki J, Kröll T, Lozano M, Nara Singh B S, O'Donnell D, Ojala J, Page R D, Pedersen L G, Raison C, Reiter P, Rodriguez J A, Rosiak D, Rothe S, Scheck M, Seidlitz M, Shneidman T M, Siebeck B, Sinclair J, Smith J F, Stryjczyk M, Van Duppen P, Vinals S, Virtanen V, Warr N, Wrzosek-Lipska K, Zielińska M
University of Liverpool, Liverpool L69 7ZE, United Kingdom.
ISOLDE, CERN, 1211 Geneva 23, Switzerland.
Phys Rev Lett. 2020 Jan 31;124(4):042503. doi: 10.1103/PhysRevLett.124.042503.
There is sparse direct experimental evidence that atomic nuclei can exhibit stable "pear" shapes arising from strong octupole correlations. In order to investigate the nature of octupole collectivity in radium isotopes, electric octupole (E3) matrix elements have been determined for transitions in ^{222,228}Ra nuclei using the method of sub-barrier, multistep Coulomb excitation. Beams of the radioactive radium isotopes were provided by the HIE-ISOLDE facility at CERN. The observed pattern of E3 matrix elements for different nuclear transitions is explained by describing ^{222}Ra as pear shaped with stable octupole deformation, while ^{228}Ra behaves like an octupole vibrator.
几乎没有直接的实验证据表明原子核能够因强八极关联而呈现出稳定的“梨形”。为了研究镭同位素中八极集体性的本质，利用亚势垒多步库仑激发方法，确定了(^{222,228}Ra)核跃迁中的电八极（E3）矩阵元。放射性镭同位素束由欧洲核子研究中心的HIE - ISOLDE设施提供。通过将(^{222}Ra)描述为具有稳定八极形变的梨形，而(^{228}Ra)表现为八极振动体，解释了不同核跃迁的E3矩阵元的观测模式。
