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Background: The even cadmium isotopes near the neutron midshell have long been considered among the best examples of vibrational nuclei. However, the vibrational nature of these nuclei has been questioned based on E2 transition rates that are not consistent with vibrational excitations. In the neighboring odd-mass nuclei, the g factors of the low-excitation collective states have been shown to be more consistent with a deformed rotational core than a vibrational core. Moving beyond the comparison of vibrational versus rotational models, recent advances in computational power have made shell-model calculations feasible for Cd isotopes. These calculations may give insights into the emergence and nature of collectivity in the Cd isotopes. Purpose: To investigate the nature of collective excitations in the A ≈ 100 region through experimental and theoretical studies of magnetic moments and electromagnetic transitions in 111Cd. Method: The spectroscopy of 111Cd has been studied following Coulomb excitation. Angular correlation measurements, transient-field g-factor measurements and lifetime measurements by the Doppler-broadened line shape method were performed. The structure of the nucleus was explored in relation to particle-vibration versus particle-rotor interpretations. Large-scale shell-model calculations were performed with the SR88MHJM Hamiltonian. Results: Excited-state g factors have been measured, spin assignments examined, and lifetimes determined. Attention was given to the reported 5/2+ 753-keV and 3/2+ 755-keV states. The 3/2+ 755-keV level was not observed; evidence is presented that the reported 3/2+ state was a misidentification of the 5/2+ 753-keV state. Conclusions: It is shown that the g factors and level structure of 111Cd are not readily explained by the particle-vibration model. A particle-rotor approach has both successes and limitations. The shell-model approach successfully reproduces much of the known low-excitation structure in 111Cd. [ABSTRACT FROM AUTHOR]

Transient-field g-factor measurements in inverse kinematics were performed for the first-excited states of the stable, even isotopes of Ge and Se. The g factors of 74Ge and 74Se were measured simultaneously using a cocktail beam, which eliminates most possible sources of systematic error in a relative g-factor measurement. The results are g(74Se)/g(74Ge)=1.34(7), g(70Ge)/g(74Ge)=1.16(15), g(72Ge)/g(74Ge)=0.92(13), g(76Ge)/g(74Ge)=0.88(5), g(76Se)/g(74Se)=0.96(7), g(78Se)/g(74Se)=0.82(5), g(80Se)/g(74Se)=0.99(7), and g(82Se)/g(74Se)=1.19(6). The measured g-factor ratios are in agreement with ratios from previous measurements, despite considerable variation in previous reported absolute values. The absolute values of the g factors remain uncertain, however, the Rutgers parametrization was used to set the transient-field strength and then compare the experimental g factors with shell-model calculations based on the JUN45 and jj44b interactions. Modest agreement was found between experiment and theory for both interactions. The shell-model calculations indicate that the g(21+) values and trends are determined largely by the balance of the spin carried by orbital motion of the protons. [ABSTRACT FROM AUTHOR]

The time differential perturbed angular distribution technique with LaBr3 detectors has been applied to the Iπ=11-/2 isomeric state (Ex=846 keV, τ=107 ns) in 107Cd, which was populated and recoil-implanted into a gadolinium host following the 98Mo(12C, 3n)107Cd reaction. The static hyperfine field strength of Cd recoil implanted into gadolinium was thus measured, together with the fraction of nuclei implanted into field-free sites, under similar conditions as pertained for a previous implantation perturbed angular distribution g-factor measurement on the Iπ=10+ state in 110Cd. The 110Cdg(10+) value was thereby reevaluated, bringing it into agreement with the value expected for a seniority-two νh11/2 configuration. [ABSTRACT FROM AUTHOR]

The only proposed observation of a discrete, hexacontatetrapole (E6) transition in nature occurs from the T_{1/2}=2.54(2)-min decay of ^{53m}Fe. However, there are conflicting claims concerning its γ-decay branching ratio, and a rigorous interrogation of γ-ray sum contributions is lacking. Experiments performed at the Australian Heavy Ion Accelerator Facility were used to study the decay of ^{53m}Fe. For the first time, sum-coincidence contributions to the weak E6 and M5 decay branches have been firmly quantified using complementary experimental and computational methods. Agreement across the different approaches confirms the existence of the real E6 transition; the M5 branching ratio and transition rate have also been revised. Shell model calculations performed in the full fp model space suggest that the effective proton charge for high-multipole, E4 and E6, transitions is quenched to approximately two-thirds of the collective E2 value. Correlations between nucleons may offer an explanation of this unexpected phenomenon, which is in stark contrast to the collective nature of lower-multipole, electric transitions observed in atomic nuclei.

The electric monopole (E0) transition strength ρ^{2} for the transition connecting the third 0^{+} level, a "superdeformed" band head, to the "spherical" 0^{+} ground state in doubly magic ^{40}Ca is determined via e^{+}e^{-} pair-conversion spectroscopy. The measured value ρ^{2}(E0;0&#95;{3}^{+}→0&#95;{1}^{+})=2.3(5)×10^{-3} is the smallest ρ^{2}(E0;0^{+}→0^{+}) found in A<50 nuclei. In contrast, the E0 transition strength to the ground state observed from the second 0^{+} state, a band head of "normal" deformation, is an order of magnitude larger ρ^{2}(E0;0&#95;{2}^{+}→0&#95;{1}^{+})=25.9(16)×10^{-3}, which shows significant mixing between these two states. Large-scale shell-model (LSSM) calculations are performed to understand the microscopic structure of the excited states and the configuration mixing between them; experimental ρ^{2} values in ^{40}Ca and neighboring isotopes are well reproduced by the LSSM calculations. The unusually small ρ^{2}(E0;0&#95;{3}^{+}→0&#95;{1}^{+}) value is due to destructive interference in the mixing of shape-coexisting structures, which are based on several different multiparticle-multihole excitations. This observation goes beyond the usual treatment of E0 strengths, where two-state shape mixing cannot result in destructive interference.