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High-spin structures of holmium ( $Z=67$ ) and erbium ( $Z=68$ ) isotopes are presented near mass 160, a region where collective and single-particle modes of excitation compete in the generation of angular momentum at the highest experimentally attainable spins in atomic nuclei. The level schemes of the ${}^{156,157,158}\mathrm{Ho}$ isotopes have been significantly extended, reaching spins in the $40\hslash$ to $55\hslash$ range, through multiple experiments utilizing the Gammasphere spectrometer. In particular, several new noncollective band-terminating states are reported for these nuclei. The nature of these states, including both valence-space terminations and core-excited oblateconfigurations, is discussed in terms of proton particle-hole (p-h) excitations across the semimagic $Z=64$ shell closure. Cranked-Nilsson–Strutinsky (CNS) calculations have been used to interpret the nature of these noncollective states. The corresponding terminating states in ${}^{154–159}\mathrm{Er}$ are also included, providing a systematic description of band termination in this mass region. In addition, three weak rotational structures have been assigned to ${}^{157}\mathrm{Ho}$ at the highest spins. These collective bands are proposed to be based on a triaxial strongly deformed nuclear shape, involving neutron p-h excitations across the $N=82$ shell gap. 

Abstract Lifetimes of higher-lying states ($$2_2^+$$ $2_2^{+}$ and$$4_1^+$$ $4_1^{+}$ ) in$$^{16}$$ $_{}^{16}$ C have been measured, employing the Gammasphere and Microball detector arrays, as key observables to test and refine ab initio calculations based on interactions developed within chiral Effective Field Theory. The presented experimental constraints to these lifetimes of$$\tau ({2_2^+}) = [\,244, 446]\,~\textrm{fs}$$ $\tau \left(2_2^{+}\right)=[244,446]\text{fs}$ and$$\tau ({4_1^+}) = [\,1.8, 4]\,~\textrm{ps}$$ $\tau \left(4_1^{+}\right)=[1.8,4]\text{ps}$ , combined with previous results on the lifetime of the$$2_1^+$$ $2_1^{+}$ state of$$^{16}$$ $_{}^{16}$ C, provide a rather complete set of key observables to benchmark the theoretical developments. We present No-Core Shell-Model calculations using state-of-the-art chiral 2- (NN) and 3-nucleon (3N) interactions at next-to-next-to-next-to-leading order for both the NN and the 3N contributions and a generalized natural-orbital basis (instead of the conventional harmonic-oscillator single-particle basis) which reproduce, for the first time, the experimental findings remarkably well. The level of agreement of the new calculations as compared to the CD-Bonn meson-exchange NN interaction is notable and presents a critical benchmark for theory. 

Abstract The observation ofγrays from the decay of⁴⁴Ti in the remnants of core-collapse supernovae (CCSNe) provides crucial information regarding the nucleosynthesis occurring in these events, as⁴⁴Ti production is sensitive to CCSNe conditions. The final abundance of⁴⁴Ti is also sensitive to specific nuclear input parameters, one of which is the⁵⁷Ni(p,γ)⁵⁸Cu reaction rate. A precise rate for⁵⁷Ni(p,γ)⁵⁸Cu is thus critical if⁴⁴Ti production is to be an effective probe into CCSNe. To experimentally constrain the⁵⁷Ni(p,γ)⁵⁸Cu rate, the structure properties of⁵⁸Cu were measured via the⁵⁸Ni(³He,t)⁵⁸Cu*(γ) reaction using GODDESS (GRETINA ORRUBA Dual Detectors for Experimental Structure Studies) at Argonne National Laboratory’s ATLAS facility. Details of the experiment, ongoing analysis, and plans are presented.