A. B. Hayes

Direct evidence of octupole deformation in neutron-rich 144Ba

The neutron-rich nucleus ^{144}Ba (t_{1/2}=11.5u2009u2009s) is expected to exhibit some of the strongest octupole correlations among nuclei with mass numbers A less than 200. Until now, indirect evidence for such strong correlations has been inferred from observations such as enhanced E1 transitions and interleaving positive- and negative-parity levels in the ground-state band. In this experiment, the octupole strength was measured directly by sub-barrier, multistep Coulomb excitation of a post-accelerated 650-MeV ^{144}Ba beam on a 1.0-mg/cm^{2} ^{208}Pb target. The measured value of the matrix element, ⟨3_{1}^{-}∥M(E3)∥0_{1}^{+}⟩=0.65(+17/-23) eb^{3/2}, corresponds to a reduced B(E3) transition probability of 48(+25/-34)u2009u2009W.u. This result represents an unambiguous determination of the octupole collectivity, is larger than any available theoretical prediction, and is consistent with octupole deformation.

Direct Evidence for Octupole Deformation in Ba146 and the Origin of Large E1 Moment Variations in Reflection-Asymmetric Nuclei

Despite the more than 1 order of magnitude difference between the measured dipole moments in ^{144}Ba and ^{146}Ba, the octupole correlations in ^{146}Ba are found to be as strong as those in ^{144}Ba with a similarly large value of B(E3;3^{-}→0^{+}) determined as 48(+21-29)u2009u2009W.u. The new results not only establish unambiguously the presence of a region of octupole deformation centered on these neutron-rich Ba isotopes, but also manifest the dependence of the electric dipole moments on the occupancy of different neutron orbitals in nuclei with enhanced octupole strength, as revealed by fully microscopic calculations.

Shape coexistence and the role of axial asymmetry in 72Ge

Abstract The quadrupole collectivity of low-lying states and the anomalous behavior of the 0 2 + and 2 3 + levels in 72Ge are investigated via projectile multi-step Coulomb excitation with GRETINA and CHICO-2. A total of forty six E2 and M1 matrix elements connecting fourteen low-lying levels were determined using the least-squares search code, gosia . Evidence for triaxiality and shape coexistence, based on the model-independent shape invariants deduced from the Kumar–Cline sum rule, is presented. These are interpreted using a simple two-state mixing model as well as multi-state mixing calculations carried out within the framework of the triaxial rotor model. The results represent a significant milestone towards the understanding of the unusual structure of this nucleus.

Studies Around A∼100 Using Binary Reactions

The structure of stable and neutron‐rich nuclei with Z∼42 and N∼58 have been studied following binary heavy‐ion reactions between a 136Xe beam and a thin, self‐supporting 100Mo target. Discrete states at spins of 20ℏ and above have been identified and these data allow both gamma‐ray fold and binary‐fragment particle angular distribiution analyses to be made. On the basis of these results, suggestions are made for future directions of this research extending to higher spin states in this region where more exotic nuclear shapes are predicted.

First Direct Observation Of Enhanced Octupole Collectivity In 144,146Ba

The octupole strength present in the neutron-rich, radiocative nucleus

Observation of an isomeric state in {sup 197}Au

^{146}

Nuclear structure implications for controlled energy release of isomers

Ba has been experimentally determined for the first time using Coulomb excitation. To achieve this,

Aspects Of The Coriolis Interaction In 235U

A

Population of 195Os via a deep‐inelastic reaction

=146 fission fragments from CARIBU were post-accelerated by the Argonne Tandem Linac Accelerator System (ATLAS) and impinged on a thin

Structural Evolution in the (N,Z,Iπ) Coordinate Frame for A∼100

^{208}