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\noindent \textbf{Background:} Detailed spectroscopy of neutron-rich, heavy, deformed nuclei is of broad interest for nuclear astrophysics and nuclear structure. Nuclei in the r-process path and following freeze-out region impact the resulting r-process abundance distribution, and the structure of nuclei midshell in both proton and neutron number helps to understand the evolution of subshell gaps and large deformation in these nuclei. \noindent \textbf{Purpose:} To improve the understanding of the nuclear structure of $^{160}$Gd, specifically the $K^\pi$=$4^+$ bands, as well as study the $\beta$-decay of $^{160}$Eu into $^{160}$Gd. \noindent \textbf{Methods:} High-statistics decay spectroscopy of $^{160}$Gd resulting from the $\beta$-decay of $^{160}$Eu was collected using the GRIFFIN spectrometer at the TRIUMF-ISAC facility. \noindent \textbf{Results:} Two new excited states and ten new transitions were observed in $^{160}$Gd. The $\beta$-decaying half-lives of the low- and high-spin isomer in $^{160}$Eu were determined, and the low-spin state's half-life was measured to be $t_{1/2}=26.0(8)$~s, $\sim$16\% shorter than previous measurements. Lifetimes of the two $K^\pi$=$4^+$ band-heads in $^{160}$Gd were measured for the first time, as well as $\gamma$-$\gamma$ angular correlations and mixing ratios of intense transitions out of those band-heads. \noindent \textbf{Conclusions:} Lifetimes and mixing ratios suggest that the hexadecapole phonon model of the $K^\pi$=$4^+$ band-heads in $^{160}$Gd is preferred over a simple two-state strong mixing scenario, although further theoretical calculations are needed to fully understand these states. Additionally, the 1999.0 keV state in $^{160}$Gd heavily populated in $\beta$-decay is shown to have positive parity, which raises questions regarding the structure of the high-spin $\beta$-decaying state in $^{160}$Eu.

We have measured the cross section of the $^{83}$Rb(p,$\gamma)^{84}$Sr radiative capture reaction in inverse kinematics using a radioactive beam of $^{83}$Rb at incident energies of 2.4 and $2.7 A$ MeV. Prior to the radioactive beam measurement, the $^{84}$Kr(p,$\gamma)^{85}$Rb radiative capture reaction was measured in inverse kinematics using a stable beam of $^{84}$Kr at an incident energy of $2.7 A$ MeV. The effective relative kinetic energies of these measurements lie within the relevant energy window for the $\gamma$ process in supernovae. The central values of the measured partial cross sections of both reactions were found to be $0.17-0.42$ times the predictions of statistical model calculations. Assuming the predicted cross section at other energies is reduced by the same factor leads to a slightly higher calculated abundance of the $p$ nucleus $^{84}$Sr, caused by the reduced rate of the $^{84}$Sr($\gamma$,p)$^{83}$Rb reaction derived from the present measurement., Comment: 11 pages, 11 figures. arXiv admin note: text overlap with arXiv:2109.06775

International audience; The excited states of $N=44$$^{74}$Zn were investigated via $\gamma$-ray spectroscopy following $^{74}$Cu $\beta$ decay. By exploiting $\gamma$-$\gamma$ angular correlation analysis, the $2_2^+$, $3_1^+$, $0_2^+$ and $2_3^+$ states in $^{74}$Zn were firmly established. The $\gamma$-ray branching and $E2/M1$ mixing ratios for transitions de-exciting the $2_2^+$, $3_1^+$ and $2_3^+$ states were measured, allowing for the extraction of relative $B(E2)$ values. In particular, the $2_3^+ \to 0_2^+$ and $2_3^+ \to 4_1^+$ transitions were observed for the first time. The results show excellent agreement with new microscopic large-scale shell-model calculations, and are discussed in terms of underlying shapes, as well as the role of neutron excitations across the $N=40$ gap. Enhanced axial shape asymmetry (triaxiality) is suggested to characterize $^{74}$Zn in its ground state. Furthermore, an excited $K=0$ band with a significantly larger softness in its shape is identified. A shore of the $N=40$``island of inversion'' appears to manifest above $Z=26$, previously thought as its northern limit in the chart of the nuclides.

The selenium isotopes lie at the heart of a tumultuous region of the nuclear chart where shape coexistence effects grapple with neutron-proton pairing correlations, triaxiality, and the impending proton drip line. In this work, a study of Se72 by internal conversion electron and γ-ray spectroscopy was undertaken with the SPICE and TIGRESS arrays. New measurements of the branching ratio and lifetime of the 02+ state were performed, yielding a determination of ρ2(E0;02+→01+)=29(3) milliunits. Two-state mixing calculations were performed that highlighted the importance of interpretation of such E0 strength values in the context of shape coexistence.

The half-life of the superallowed Fermi $\beta^+$ emitter $^{14}$O was determined to high precision via a direct $\beta$ counting experiment performed at the Isotope Separator and Accelerator (ISAC) facility at TRIUMF. The result, $T_{1/2}$($^{14}$O) = 70619.2(76) ms, is consistent with, but is more precise than, the world average obtained from 11 previous measurements. Combining the $^{14}$O half-life deduced in the present work with the previous most precise measurements of this quantity leads to a reduction in the overall uncertainty, by nearly a factor of 2. The new world average is $T_{1/2}$($^{14}$O) = 70619.6(63) ms with a reduced $\chi^2$ value of 0.87 obtained from 8 degrees of freedom., Comment: 8 pages, 6 figures, accepted for publication in the European Physical Journal A

The selenium isotopes lie at the heart of a tumultuous region of the nuclear chart where shape coexistence effects grapple with neutron-proton pairing correlations, triaxiality, and the impending proton drip line. In this work, a study of 72Se by internal conversion electron and γ-ray spectroscopy was undertaken with the SPICE and TIGRESS arrays. New measurements of the branching ratio and lifetime of the 02+ state were performed, yielding a determination of ρ2(E0;02+→01+)=29(3) milliunits. Two-state mixing calculations were performed that highlighted the importance of interpretation of such E0 strength values in the context of shape coexistence. peerReviewed

Background: Electric-quadrupole (E2) strengths relate to the underlying quadrupole deformation of a nucleus and present a challenge for many nuclear theories. Mirror nuclei in the vicinity of the line of N=Z represent a convenient laboratory for testing deficiencies in such models, making use of the isospin symmetry of the systems. Purpose: Uncertainties associated with literature E2 strengths in 23Mg are some of the largest in Tz=∣∣12∣∣ nuclei in the sd shell. The purpose of the present paper is to improve the precision with which these values are known, to enable better comparison with theoretical models. Methods: Coulomb-excitation measurements of 23Mg and 23Na were performed at the TRIUMF-ISAC facility using the TIGRESS spectrometer. They were used to determine the E2 matrix elements of mixed E2/M1 transitions. Results: Reduced E2 transition strengths, B(E2), were extracted for 23Mg and 23Na. Their precision was improved by factors of approximately 6 for both isotopes, while agreeing within uncertainties with previous measurements. Conclusions: A comparison was made with both shell-model and ab initio valence-space in-medium similarity renormalization group calculations. Valence-space in-medium similarity renormalization group calculations were found to underpredict the absolute E2 strength, in agreement with previous studies. peerReviewed

Background: Nuclei approaching are known to exhibit strongly deformed structures and are thought to be candidates for shape coexistence. In the krypton isotopes, are poorly characterized, preventing an understanding of evolving deformation approaching . Purpose: The present work aims to determine electric quadrupole transition strengths and quadrupole moments of in order to better characterize their deformation. Conclusions: Comparison of measured and values indicates that neutron-deficient () isotopes of krypton are closer to axial deformation than other isotopic chains in the mass region. A continuation of this trend to higher may result in Sr and Zr isotopes exhibiting near-axial prolate deformation. Methods: Sub-barrier Coulomb excitation was employed, impinging the isotopes of krypton on and targets. Utilizing a semiclassical description of the safe Coulomb-excitation process matrix elements could then be determined. Results: Eleven new or improved matrix elements are determined in and seven in . The new value in disagrees with the evaluated value by , which can be explained in terms of deficiencies in a previous Coulomb-excitation analysis.

10 pags., 8 figs., 4 tabs., The nature of the and excited states in is studied using the transfer reaction in inverse kinematics at 10A MeV at TRIUMF ISAC-II, in particular to assess whether either of them can be considered as an excited halo state. The angular distributions for both states are extracted using deuteron- coincidences and analyzed using a transfer model taking into account one-step and two-step processes. A good fit of the angular distributions is obtained considering only the one-step process, whereby an inner neutron of is removed, leaving the halo neutron intact. Higher-order processes however cannot be rejected. The small spectroscopic factors extracted suggest that the structure of both states is not uniquely halo-like, but rather display a more complex configuration mixing cluster and halo structures. Further insights are limited, as this experiment specifically probed the halo-like (but not cluster-like) configuration in both states., This work was partially supported by the U.S. Department of Energy (DOE) through Grants/Contracts No. DE-FG03-93ER40789 (Colorado School of Mines), No. DEFG02-96ER40978 (Louisiana State), No. DE-SC0021422 (Michigan State), No. DE-AC05-00OR22725 (Oak Ridge National Laboratory), the National Nuclear Security Administration (NNSA) under the Stewardship Science Academic Alliances program through U.S. DOE Cooperative Agreements No. DE-FG52-08NA28552, and the National Science Foundation under Grant No. PHY-1811815 (Michigan State). This work is also supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Canadian Foundation for Innovation (CFI), the British Columbia Knowledge and Development Fund (BCKDF), the Italian National Institute for Nuclear Physics (INFN), the Spanish Ministry of Science and Innovation and FEDER funds under Projects RTI2018-098117-B-C21 and PGC2018-096994-BC21, and the Spanish Agency of Research (AEI) via Project No. PID2019-104714GB-C21.

The occurrence of octupole shapes in even-mass neutron-rich Ba isotopes has been well established. However, the situation with the odd-mass Ba and odd or odd-odd La nuclei around them is far from settled. In order to shed light on these less-studied isotopes, a fast-timing experiment was performed using GRIFFIN at TRIUMF-ISAC. A wealth of excited-state lifetimes in the 100~ps to few ns range have been measured in $^{144, 145, 146}$Ba and $^{145,146}$La populated in the $\beta^-$ and $\beta^--n$ decay of $^{145,146}$Cs. The results do not allow to draw firm conclusions on the possible octupole deformation of these nuclei but suggest different spin and parity assignments than previous works. This work highlights the need for more detailed study of the odd and odd-odd isotopes in this region to properly understand their structure., Comment: 16 pages, 7 figures

Reactions on the proton-rich nuclides drive the nucleosynthesis in Core-Collapse Supernovae (CCSNe) and in X-ray bursts (XRBs). CCSNe eject the nucleosynthesis products to the interstellar medium and hence are a potential inventory of p-nuclei, whereas in XRBs nucleosynthesis powers the light curves. In both astrophysical sites the Ni-Cu cycle, which features a competition between $^{59}$Cu(p,$\alpha$)$^{56}$Ni and $^{59}$Cu(p,$\gamma$)$^{60}$Zn, could potentially halt the production of heavier elements. Here, we report the first direct measurement of $^{59}$Cu(p,$\alpha$)$^{56}$Ni using a re-accelerated $^{59}$Cu beam and cryogenic solid hydrogen target. Our results show that the reaction proceeds predominantly to the ground state of $^{56}$Ni and the experimental rate has been found to be lower than Hauser-Feshbach-based statistical predictions. New results hint that the $\nu p$-process could operate at higher temperatures than previously inferred and therefore remains a viable site for synthesizing the heavier elements.

The fusion-evaporation reaction 28Si+40Ca at 122 MeV beam energy was used to populate excited states in the N=Z+1 nucleus 63Ga. With the combination of the Gammasphere spectrometer and the Microball CsI(Tl) charged-particle detector array, the level scheme of 63Ga was extended by more than a factor of two in terms of number of γ-ray transitions and excited states, excitation energy (Ex>30 MeV), and angular momentum (I>30 ℏ). Nine regular sequences of states were newly established in the high-spin part of the level scheme. The majority of these rotational band structures could be connected to the previously known part of the level scheme by high-energy γ-ray transitions in the energy range Eγ=4–6 MeV. Low-spin states were assessed by shell-model calculations. The high-spin rotational bands were interpreted and classified by means of cranked Nilsson-Strutinsky calculations.

A high-precision branching ratio measurement for the superallowed Fermi $\beta^{+}$ emitter $^{62}$Ga was performed with the Gamma-Ray Infrastructure for Fundamental Investigations of Nuclei (GRIFFIN) spectrometer at the Isotope Separator and Accelerator (ISAC) radioactive ion beam facility at TRIUMF. The high efficiency of the GRIFFIN spectrometer allowed 63 $\gamma$-ray transitions, with intensities down to $\approx$1 part per million (ppm) per $^{62}$Ga $\beta^{+}$ decay, to be placed in the level scheme of the daughter nucleus $^{62}$Zn, establishing the superallowed $\beta$ branching ratio for $^{62}$Ga decay to be 99.8577$^{+0.0023}_{-0.0029}\%$, a factor of 4 more precise than the previous world average. For several cascades, $\gamma-\gamma$ angular correlation measurements were performed to assign spins and/or determine the mixing ratios of transitions. In particular, the spin of the 2.342 MeV excited state in the daughter nucleus $^{62}$Zn was definitively assigned as $J = 0$. This assignment resolves a discrepancy between previous measurements and has important implications for the isospin symmetry breaking correction, $\delta_{C1}$, in $^{62}$Ga superallowed Fermi $\beta$ decay., Comment: A text label in Figure 12 has been corrected compared to the original submission

The $\beta^-$ decay of $^{47}$K to $^{47}$Ca is an appropriate mechanism for benchmarking interactions spanning the $sd$ and $pf$ shells, but current knowledge of the $\beta^-$-decay scheme is limited. We have performed a high-resolution, high-efficiency study of the $\beta^-$-decay of $^{47}$K with the GRIFFIN spectrometer at TRIUMF-ISAC. The study revealed 48 new transitions, a more precise value for the $^{47}$K half-life (17.38(3)~s), and new spin and parity assignments for eight excited states. Levels placed for the first time here raise the highest state observed in $\beta^-$ decay to within 568(3) keV of the $Q$-value and confirm the previously measured large $\beta^-$-decay branching ratios to the low-lying states. Previously unobserved $\beta^-$-feeding to 3/2$^+$ states between 4.5 and 6.1~MeV excitation energy was identified with a total $\beta^-$-feeding intensity of 1.29(2)\%. The sum of the $B(GT)$ values for these states indicates that the $1s_{1/2}$ proton hole strength near this excitation energy is comparable to the previously known $1s_{1/2}$ proton and neutron hole strengths near 2.6 MeV.

The low-lying structure of semi-magic $^{118}$Sn has been investigated through the $\beta$-decay of $^{118}$In ($T_{1/2}=4.45$ min) to study shape coexistence via the reduced transition probabilities of states in the 2p-2h proton intruder band. This high-statistics study was carried out at TRIUMF-ISAC with the GRIFFIN spectrometer. In total, 99 transitions have been placed in the level scheme with 43 being newly observed. Three low-lying $\gamma$-ray transitions with energies near 285 keV have been resolved from which the 2$^+_{\mathrm{intr.}} \rightarrow 0^+_{\mathrm{intr.}}$ 284.52-keV transition was determined to have half of the previous branching fraction leading to a $B(E2;2^+_2\rightarrow 0^+_2)$ of 21(4) W.u. compared to 39(7) W.u. from the previous measurement. Calculations using $sd$ IBM-2 with mixing have also been made to compare the experimental $B(E2)$ values to the theoretical values and to make comparisons to the $^{114,116}$Sn isotopes previously studied using the same theoretical model.

The fusion-evaporation reaction 28Si + 40Ca at 122 MeV beam energy was used to populate high-spin states in the odd-odd N = Z nucleus 62Ga. With the combination of the Gammasphere spectrometer and the Microball CsI(Tl) charged-particle detector array the decay scheme of 62Ga was extended beyond 10 MeV excitation energy. The onset of band structures was observed. These high-spin rotational states are interpreted and classified by means of cranked Nilsson-Strutinsky calculations.

Background: Electric-quadrupole ($E2$) strengths relate to the underlying quadrupole deformation of a nucleus and present a challenge for many nuclear theories. Mirror nuclei in the vicinity of the line of $N=Z$ represent a convenient laboratory for testing deficiencies in such models, making use of the isospin-symmetry of the systems. Purpose: Uncertainties associated with literature $E2$ strengths in \textsuperscript{23}Mg are some of the largest in $T_z=\left|\frac{1}{2}\right|$ nuclei in the $sd$-shell. The purpose of the present work is to improve the precision with which these values are known, to enable better comparison with theoretical models. Methods: Coulomb-excitation measurements of $^{23}$Mg and $^{23}$Na were performed at the TRIUMF-ISAC facility using the TIGRESS spectrometer. They were used to determine the $E2$ matrix elements of mixed $E2$/$M1$ transitions. Results: Reduced $E2$ transition strengths, $B(E2)$, were extracted for \textsuperscript{23}Mg and \textsuperscript{23}Na. Their precision was improved by factors of approximately six for both isotopes, while agreeing within uncertainties with previous measurements. Conclusions: A comparison was made with both shell-model and {\it ab initio} valence-space in-medium similarity renormalization group calculations. Valence-space in-medium similarity-renormalization-group calculations were found to underpredict the absolute $E2$ strength - in agreement with previous studies.

The fusion-evaporation reaction Si-28 + Ca-40 at 122 MeV beam energy was used to populate high-spin states in the odd-odd N = Z nucleus Ga-62. With the combination of the Gammasphere spectrometer and the Microball CsI(Tl) charged-particle detector array the decay scheme of Ga-62 was extended beyond 10 MeV excitation energy. The onset of band structures was observed. These high-spin rotational states are interpreted and classified by means of cranked Nilsson-Strutinsky calculations.

The $^{80}$Ge structure was investigated in a high-statistics $\beta$-decay experiment of $^{80}$Ga using the GRIFFIN spectrometer at TRIUMF-ISAC through $\gamma$, $\beta$-$e$, $e$-$\gamma$ and $\gamma$-$\gamma$ spectroscopy. No evidence was found for the recently reported 0$_2^{+}$ 639-keV level suggested as evidence for low-energy shape coexistence in $^{80}$Ge. Large-scale shell model calculations performed in $^{78,80,82}$Ge place the $0^{+}_{2}$ level in $^{80}$Ge at 2\,MeV. The new experimental evidence combined with shell model predictions indicate that low-energy shape coexistence is not present in $^{80}$Ge.

We report on high-statistics data from the $\beta^-$ decay of the $^{46}$K $J^{\pi}$ = 2$^-$ ground state taken with the GRIFFIN spectrometer located at the TRIUMF-ISAC facility. In total, 199 $\gamma$ rays and 42 excited states were placed in the level scheme, and from the observed $\beta$ feeding and angular correlations of pairs of cascading $\gamma$ rays, it was possible to assign spins and parities to excited states and determine mixing ratios for selected $\gamma$ 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.