Many-body nuclear theory utilizing microscopic or chiral potentials has developed to the point that collectivity might be dealt with in an ab initio framework without the use of effective charges; for example with the proper evolution of operators, or alternatively, through the use of an appropriate and manageable subset of particle-hole excitations.We present a precise determination of E2 strength in 22 Mg and its mirror 22 Ne by Coulomb excitation, allowing for rigorous comparisons with theory. No-core symplectic shell-model calculations were performed and agree with the new B(E2) values while in-medium similarity-renormalization-group calculations consistently underpredict the absolute strength, with the missing strength found to have both isoscalar and isovector components.

The β-decay half-lives of [128][129][130] Cd have been measured with the newly commissioned GRIFFIN γ-ray spectrometer at the TRIUMF-ISAC facility. The time structures of the most intense γ-rays emitted following the β-decay were used to determine the half-lives of 128 Cd and 130 Cd to be T 1/2 = 246.2(21) ms and T 1/2 = 126(4) ms, respectively. The half-lives of the 3/2 + and 11/2 − states of 129 Cd were measured to be T 1/2 (3/2 + ) = 157(8) ms and T 1/2 (11/2 − ) = 147(3) ms. The half-lives of the Cd isotopes around the N = 82 shell closure are an important ingredient in astrophysical simulations to derive the magnitude of the second r-process abundance peak in the A ∼ 130 region. Our new results are compared with recent literature values and theoretical calculations.

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Excited states in 58,60,62 Ni were populated via inelastic proton scattering at the Australian National University as well as via inelastic neutron scattering at the University of Kentucky Accelerator Laboratory. The Super-e electron spectrometer and the CAESAR Compton-suppressed HPGe array were used in complementary experiments to measure conversion coefficients and δ(E2/M 1) mixing ratios, respectively, for a number of 2 + → 2 + transitions. The data obtained were combined with lifetimes and branching ratios to determine E0, M 1, and E2 transition strengths between 2 + states. The E0 transition strengths between 0 + states were measured using internal conversion electron spectroscopy and compare well to previous results from internal pair formation spectroscopy. The E0 transition strengths between the lowest-lying 2 + states were found to be consistently large for the isotopes studied.

The island of inversion for neutron-rich nuclei in the vicinity of N = 20 has become the testing ground par excellence for our understanding and modeling of shell evolution with isospin. In this context, the structure of the transitional nucleus 29 Mg is critical. The first quantitative measurements of the single-particle structure of 29 Mg are reported, using data from the d (28 Mg, p γ) 29 Mg reaction. Two key states carrying significant = 3 (f-wave) strength were identified at 2.40 ± 0.10 (J π = 5/2 −) and 4.28 ± 0.04 MeV (7/2 −). New state-of-the-art shell-model calculations have been performed and the predictions are compared in detail with the experimental results. While the two lowest 7/2 − levels are well described, the sharing of single-particle strength disagrees with experiment for both the 3/2 − and 5/2 − levels and there appear to be general problems with configurations involving the p 3/2 neutron orbital and core-excited components. These conclusions are supported by an analysis of the neutron occupancies in the shell-model calculations.

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We report on high-statistics data from the β − decay of the 46 K J π = 2 − ground state taken with the GRIFFIN spectrometer located at the TRIUMF-ISAC facility. In total, 199 γ rays and 42 excited states were placed in the level scheme, and from the observed β feeding and angular correlations of pairs of cascading γ rays, it was possible to assign spins and parities to excited states and determine mixing ratios for selected γ rays. The level structure of 46 Ca is compared to theoretical predictions from a microscopic valence-space Hamiltonian derived from two-(NN) and three-nucleon (3N) forces. These calculations are in reasonable agreement with the experimental data and indicate that the protons in this region are not as inert as would be expected for semi-magic nuclei.

The Tz = − 3 2 nucleus 21 Mg has been studied by Coulomb excitation on 196 Pt and 110 Pd targets. A 205.6(1)-keV γ-ray transition resulting from the Coulomb excitation of the 5 * panu.ruotsalainen@jyu.fi; Present address: