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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.

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.

We have measured the cross section of the $^{83}$Rb(p,$γ)^{84}$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,$γ)^{85}$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 $γ$ 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($γ$,p)$^{83}$Rb reaction derived from the present measurement., 11 pages, 11 figures. arXiv admin note: text overlap with arXiv:2109.06775

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 dripline. In this work a study of $^{72}$Se by internal conversion electron and $\gamma$-ray spectroscopy was undertaken with the SPICE and TIGRESS arrays. New measurements of the branching ratio and lifetime of the $0_2^+$ state were performed yielding a determination of $\rho^2(E0;0_2^+{\rightarrow}0_1^+)=29(3)$ milliunits. two state mixing calculations were performed that highlighted the importance of interpretation of such $E0$ strength values in the context of shape-coexistence.

We present new experimental measurements of resonance strengths in the astrophysical 23Al(p, {\gamma})24Si reaction, constraining the pathway of nucleosynthesis beyond 22Mg in X-ray burster scenarios. Specifically, we have performed the first measurement of the (d, p) reaction using a radioactive beam of 23Ne to explore levels in 24Ne, the mirror analog of 24Si. Four strong single-particle states were observed and corresponding neutron spectroscopic factors were extracted with a precision of {\sim}20{\%}. Using these spectroscopic factors, together with mirror state identifications, we have reduced uncertainties in the strength of the key {\ell} = 0 resonance at Er= 157 keV, in the astrophysical 23Al(p, {\gamma}) reaction, by a factor of 4. Our results show that the 22Mg(p, {\gamma})23Al(p, {\gamma}) pathway dominates over the competing 22Mg({\alpha}, p) reaction in all but the most energetic X-ray burster events (T>0.85GK), significantly affecting energy production and the preservation of hydrogen fuel., Comment: 5 pages, 3 figures

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,$��$)$^{56}$Ni and $^{59}$Cu(p,$��$)$^{60}$Zn, could potentially halt the production of heavier elements. Here, we report the first direct measurement of $^{59}$Cu(p,$��$)$^{56}$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 $��p$-process could operate at higher temperatures than previously inferred and therefore remains a viable site for synthesizing the heavier elements.

The $��$-decay of neutron-rich $^{129}$In into $^{129}$Sn was studied using the GRIFFIN spectrometer at the ISAC facility at TRIUMF. The study observed the half-lives of the ground state and each of the $��$-decaying isomers. The level scheme of $^{129}$Sn has been expanded with thirty-one new $��$-ray transitions and nine new excited levels, leading to a re-evaluation of the $��$-branching ratios and level spin assignments. The observation of the $��$-decay of the (29/2$^{+}$) 1911-keV isomeric state in $^{129}$In is reported for the first time, with a branching ratio of 2.0(5)$\%$.

Background: Recent developments in {\it ab initio} nuclear theory demonstrate promising results in medium- to heavy-mass nuclei. A particular challenge for many of the many-body methodologies, however, is an accurate treatment of the electric-quadrupole, $E2$, strength associated with collectivity. Purpose: In this work we present high-precision $E2$ data for the mirror nuclei $^{23}$Mg and $^{23}$Na for comparison with such theory. We interpret these results in combination with other recent measurements performed by the collaboration and the available literature. Methods: Coulomb-excitation measurements of $^{23}$Mg and $^{23}$Na were performed at the TRIUMF-ISAC facility using the TIGRESS spectrometer and were used to determine the $E2$ matrix elements of mixed $E2$/$M1$ transitions. Results: $E2$ transition strengths were extracted for $^{23}$Mg and $^{23}$Na. Transition strength ($B(E2)$) 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 results - but a full analysis of $sd$-shell nuclei found no indication of an isovector component to the missing strength. Comparison with full configuration interaction and coupled cluster calculations in the case of $^{14}$C indicates that correlated multi-particle multi-hole excitations are essential to the reproduction of quadrupole excitation amplitudes., To be submitted to Physical Review C

The low-lying structure of semi-magic $^{118}$Sn has been investigated through the $��$-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 $��$-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.

Spectroscopy of doubly magic $^{132}_{50}$Sn$_{82}$ has been performed with the GRIFFIN spectrometer at TRIUMF-ISAC following the $��$ decay of $^{132}_{49}$In$_{83}$. The analysis has allowed for the placement of a total of 70 transitions and 29 excited states in $^{132}$Sn. Detailed spectroscopy has also been performed on $^{131}$Sb, resulting from the $��$ decay of $^{131}$Sn, produced from the $��$-delayed neutron decay of $^{132}$In. Measurement of $��$-rays in both $^{131}$Sn and $^{131}$Sb has led to the determination of the $��$-delayed neutron emission probability, $P_{n}$, from $^{132}$In. This is the first time the $P_{n}$ has been measured for this nucleus using $��$ spectroscopy, and the new value of 12.3(4)% is consistent with the most recent $��-n$ counting experiment. Additionally, $��$-$��$ angular correlations have been performed in $^{132}$Sn, supporting the spin assignments of several excited states. Novel ab initio calculations are presented which describe several of the excited states, and these are compared to the experimental spectrum., 14 pages, 7 figures, to be published in Physical Review C

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.

The $��^-$ 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 $��^-$-decay scheme is limited. We have performed a high-resolution, high-efficiency study of the $��^-$-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 $��^-$ decay to within 568(3) keV of the $Q$-value and confirm the previously measured large $��^-$-decay branching ratios to the low-lying states. Previously unobserved $��^-$-feeding to 3/2$^+$ states between 4.5 and 6.1~MeV excitation energy was identified with a total $��^-$-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.

A high-precision branching ratio measurement for the superallowed Fermi $��^{+}$ 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 $��$-ray transitions, with intensities down to $\approx$1 part per million (ppm) per $^{62}$Ga $��^{+}$ decay, to be placed in the level scheme of the daughter nucleus $^{62}$Zn, establishing the superallowed $��$ 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, $��-��$ 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, $��_{C1}$, in $^{62}$Ga superallowed Fermi $��$ decay., A text label in Figure 12 has been corrected compared to the original submission

The region around neutron number N = 60 in the neutron-rich Sr and Zr nuclei is one of the most dramatic examples of a ground state shape transition from (near) spherical below N = 60 to strongly deformed shapes in the heavier isotopes. The single-particle structure of 95-97Sr approaching the ground state shape transition at 98 Sr has been investigated via single-neutron transfer reactions using the (d, p) reaction in inverse kinematics. These reactions selectively populate states with a large overlap of the projectile ground state coupled to a neutron in a single-particle orbital. Radioactive 94,95,96Sr nuclei with energies of 5.5 AMeV were used to bombard a CD 2 target. Recoiling light charged particles and {\gamma} rays were detected using a quasi-4{\pi} silicon strip detector array and a 12 element Ge array. The excitation energy of states populated was reconstructed employing the missing mass method combined with {\gamma}-ray tagging and differential cross sections for final states were extracted. A reaction model analysis of the angular distributions allowed for firm spin assignments to be made for the low-lying 352, 556 and 681 keV excited states in 95Sr and a constraint has been placed on the spin of the higher-lying 1666 keV state. Angular distributions have been extracted for 10 states populated in the d(95Sr,p)96Sr reaction, and constraints have been provided for the spins and parities of several final states. Results are compared to shell model calculations in several model spaces and the structure of low-lying states in 94Sr and 95Sr is well-described. The spectroscopic strength of the 0+ and 2 states in 96Sr is significantly more fragmented than predicted., Comment: PRC accepted

The half-lives of three $��$ decaying states of $^{131}_{~49}$In$_{82}$ have been measured with the GRIFFIN $��$-ray spectrometer at the TRIUMF-ISAC facility to be $T_{1/2}(1/2^-)=328(15)$~ms, $T_{1/2}(9/2^+)=265(8)$~ms, and $T_{1/2}(21/2^+)=323(55)$~ms, respectively. The first observation of $��$-rays following the $��n$ decay of $^{131}$In into $^{130}$Sn is reported. The $��$-delayed neutron emission probability is determined to be $P_{1n} = 12(7)\%$ for the $21/2^+$ state and $2.3(3)\%$ from the combined $1/2^-$ and $9/2^+$ states of $^{131}_{~49}$In$_{82}$ observed in this experiment. A significant expansion of the decay scheme of $^{131}$In, including 17 new excited states and 34 new $��$-ray transitions in $^{131}_{~50}$Sn$_{81}$ is also reported. This leads to large changes in the deduced $��$ branching ratios to some of the low-lying states of $^{131}$Sn compared to previous work with implications for the strength of the first-forbidden $��$ transitions in the vicinity of doubly-magic $^{132}_{~50}$Sn$_{82}$., 14 pages, 15 figures, 5 tables

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

We used the 8$\pi$ $\gamma$-ray spectrometer at the TRIUMF-ISAC radiocative ion beam facility to obtain high-precision branching ratios for $^{19}$Ne $\beta^+$ decay to excited states in $^{19}$F. Together with other previous work, our measurements determine the superallowed $1/2^+ \to 1/2^+$ beta branch to the ground state in $^{19}$F to be 99.9878(7)\%, which is three times more precise than known previously. The implications of these measurements for testing a variety of weak interaction symmetries are discussed briefly.

Detailed spectroscopic measurements of excited states in $^{50}$Cr and $^{62}$Zn were performed using 24~MeV (p,t) transfer reactions on $^{52}$Cr and $^{64}$Zn, respectively. In total, forty-five states in $^{50}$Cr and sixty-seven states in $^{62}$Zn were observed up to excitation energies of 5.5~MeV, including several previously unobserved states. These experimental results are compared to {\it ab-initio} shell-model calculations using chiral effective field theory ($\chi$-EFT) with the valence-space in-medium similarity renormalization group (VS-IMSRG) method. This comparison demonstrates good agreement in the level orderings with these new theoretical methods, albeit with a slight over binding in the calculations. This work is part of a continued push to benchmark {\it ab-initio} theoretical techniques to nuclear structure data in $0^+\rightarrow0^+$ superallowed Fermi $\beta$ decay systems., Comment: Submitted to Physical Review C as a Regular Article. 10 pages, 9 figures, 2 tables

The half-lives of isotopes around the $N=82$ shell closure are an important ingredient in astrophysical simulations and strongly influence the magnitude of the second $r$-process abundance peak in the $A\sim130$ region. The most neutron-rich $N=82$ nuclei are not accessible to the current generation of radioactive beam facilities and $r$-process simulations must therefore rely on calculations of the half-lives of the isotopes involved. Half-life measurements of the experimentally accessible nuclei in this region are important in order to benchmark these calculations. The half-life of $^{130}$Cd is particularly important as it is used to tune the Gamow-Teller quenching in shell-model calculations for the $\beta$ decay of other nuclei in this region. In this work, the GRIFFIN $\gamma$-ray spectrometer at the TRIUMF-ISAC facility was used to measure the half-life of $^{130}_{~48}$Cd$_{82}$ to be $T_{1/2}= 126(4)$ ms. In addition, the half-lives of the three $\beta$ decaying states of $^{131}_{~49}$In$_{82}$ were measured to be $T_{1/2}(1/2^-)=328(15)$ ms, $T_{1/2}(9/2^+)=265(8)$ ms, and $T_{1/2}(21/2^+)=323(50)$ ms, respectively, providing an important benchmark for half-life calculations in this region., Comment: Talk presented CIPANP2018. 9 pages, LaTeX, 5 pdf figures, 1 png figure

The evolution of nuclear magic numbers at extremes of isospin is a topic at the forefront of contemporary nuclear physics. $N=50$ is a prime example, with increasing experimental data coming to light on potentially doubly-magic $^{100}$Sn and $^{78}$Ni at the proton-rich and proton-deficient extremes, respectively. Experimental discrepancies exist in the data for less exotic systems. In $^{86}$Kr the $B(E2;2^+_1\rightarrow0^+_1)$ value - a key indicator of shell evolution - has been experimentally determined by two different methodologies, with the results deviating by $3\sigma$. Here, we report on a new high-precision measurement of this value, as well as the first measured lifetimes and hence transition strengths for the $2^+_2$ and $3^-_{(2)}$ states in the nucleus. The Doppler-shift attenuation method was implemented using the TIGRESS gamma-ray spectrometer and TIGRESS integrated plunger (TIP) device. High-statistics Monte-Carlo simulations were utilized to extract lifetimes in accordance with state-of-the-art methodologies. Lifetimes of $\tau(2^+_1)=336\pm4\text{(stat.)}\pm20\text{(sys.)}$ fs, $\tau(2^+_2)=263\pm9\text{(stat.)}\pm19\text{(sys.)}$ fs and $\tau(3^-_{(2)})=73\pm6\text{(stat.)}\pm32\text{(sys.)}$ fs were extracted. This yields a transition strength for the first-excited state of $B(E2;2^+_1\rightarrow0^+)=259\pm3\text{(stat.)}\pm16\text{(sys.)}$ e$^2$fm$^4$. The measured lifetime disagrees with the previous Doppler-shift attenuation method measurement by more than $3\sigma$, while agreeing well with a previous value extracted from Coulomb excitation. The newly extracted $B(E2;2^+_1\rightarrow0^+_1)$ value indicates a more sudden reduction in collectivity in the $N=50$ isotones approaching $Z=40$., Comment: 17 pages, 10 figures, to be submitted to Physical Review C

The $T_z$~=~$-\frac{3}{2}$ nucleus ${}^{21}$Mg has been studied by Coulomb excitation on ${}^{196}$Pt and ${}^{110}$Pd targets. A 205.6(1)-keV $\gamma$-ray transition resulting from the Coulomb excitation of the $\frac{5}{2}^+$ ground state to the first excited $\frac{1}{2}^+$ state in ${}^{21}$Mg was observed for the first time. Coulomb excitation cross-section measurements with both targets and a measurement of the half-life of the $\frac{1}{2}^+$ state yield an adopted value of $B(E2;\frac{5}{2}^+\rightarrow\frac{1}{2}^+)$~=~13.3(4)~W.u. A new excited state at 1672(1)~keV with tentative $\frac{9}{2}^+$ assignment was also identified in ${}^{21}$Mg. This work demonstrates large difference of the $B(E2;\frac{5}{2}^+\rightarrow\frac{1}{2}^+)$ values between $T$~=~$\frac{3}{2}$, $A$~=~21 mirror nuclei. The difference is investigated in the shell-model framework employing both isospin conserving and breaking USD interactions and using modern \textsl{ab initio} nuclear structure calculations, which have recently become applicable in the $sd$ shell., Comment: 8 pages, 6 figures, submitted to Phys. Rev. C, Rapid Communication

The GRIFFIN spectrometer at TRIUMF-ISAC has been used to study excited states and transitions in $^{50}$Sc following the $\beta$-decay of $^{50}$Ca. Branching ratios were determined from the measured $\gamma$-ray intensities, and angular correlations of $\gamma$ rays have been used to firmly assign the spins of excited states. The presence of an isomeric state that decays by an $M3$ transition with a $B(M3)$ strength of 13.6(7)\,W.u. has been confirmed. We compare with the first {\it ab initio} calculations of $B(M3$) strengths in light and medium-mass nuclei from the valence-space in-medium similarity renormalization group approach, using consistently derived effective Hamiltonians and $M3$ operator. The experimental data are well reproduced for isoscalar $M3$ transitions when using bare $g$-factors, but the strength of isovector $M3$ transitions are found to be underestimated by an order of magnitude.

A previous measurement of the $\beta-\gamma$ directional coefficient in $^{22}$Na $\beta$ decay was used to extract recoil-order form factors. The data indicate the requirement of a significant induced-tensor matrix element for the decay.This conclusion largely relies on a Standard-Model-allowed weak magnetism form factor which was determined using an unpublished value of the analog $2_1^+\to3_1^+$ $\gamma$ branch in $^{22}$Na, with the further assumption that the transition is dominated by its isovector $M1$ component. We obtain for the first time an unambiguous determination of the $2_1^+ \to 3_1^+$ branch in $^{22}$Na to be $0.45(8)\%$. Using the Conserved Vector Current (CVC) hypothesis, our branch determines the weak magnetism form factor for $^{22}$Na $\beta$ decay to be $|b/Ac_1| = 8.7(1.1)$. Together with the $\beta-\gamma$ angular correlation coefficient, we obtain a large induced-tensor form factor for the decay that continues to disagree with theoretical predictions. Two plausible explanations are suggested., Comment: Submitted to Phys. Rev. C

A high-precision half-life measurement for the superallowed Fermi $��^+$ emitter $^{22}$Mg was performed at the TRIUMF-ISAC facility using a 4$��$ proportional gas counter. The result of $T_{1/2} = 3.87400 \pm 0.00079$ s is a factor of 3 more precise than the previously adopted world average and resolves a discrepancy between the two previously published $^{22}$Mg half-life measurements., 7 pages, 9 figures

A $^{52}$Cr$(p,t)$$^{50}$Cr two-neutron pickup reaction was performed using the Q3D magnetic spectrograph at the Maier-Leibnitz-Laboratorium in Garching, Germany. Excited states in $^{50}$Cr were observed up to an excitation energy of 5.3 MeV. Despite significantly increased sensitivity and resolution over previous work, no evidence of the previously assigned first excited $0^+$ state was found. As a result, the $0^+_2$ state is reassigned at an excitation energy of $E_x=3895.0(5)$ keV in $^{50}$Cr. This reassignment directly impacts direct searches for a non-analogue Fermi $��^+$ decay branch in $^{50}$Mn. These results also show better systematic agreement with the theoretical predictions for the $0^+$ state spectrum in $^{50}$Cr using the same formalism as the isospin-symmetry-breaking correction calculations for superallowed nuclei. The experimental data are also compared to $ab$-$initio$ shell-model predictions using the IM-SRG formalism based on $NN$ and $3N$ forces from chiral-EFT in the $pf$-shell for the first time., Accepted for Publication in Physical Review C as a Rapid Communication

The reaction mechanisms of the two-neutron transfer reaction $^{12}$C($^6$He,$^4$He) have been studied at 30 MeV at the TRIUMF ISAC-II facility using the SHARC charged-particle detector array. Optical potential parameters have been extracted from the analysis of the elastic scattering angular distribution. The new potential has been applied to the study of the transfer angular distribution to the 2$^+_2$ 8.32 MeV state in $^{14}$C, using a realistic 3-body $^6$He model and advanced shell model calculations for the carbon structure, allowing to calculate the relative contributions of the simultaneous and sequential two-neutron transfer. The reaction model provides a good description of the 30 MeV data set and shows that the simultaneous process is the dominant transfer mechanism. Sensitivity tests of optical potential parameters show that the final results can be considerably affected by the choice of optical potentials. A reanalysis of data measured previously at 18 MeV however, is not as well described by the same reaction model, suggesting that one needs to include higher order effects in the reaction mechanism., Comment: 9 pages, 9 figures

We report a precise determination of the 19Ne half-life to be $T_{1/2} = 17.262 \pm 0.007$ s. This result disagrees with the most recent precision measurements and is important for placing bounds on predicted right-handed interactions that are absent in the current Standard Model. We are able to identify and disentangle two competing systematic effects that influence the accuracy of such measurements. Our findings prompt a reassessment of results from previous high-precision lifetime measurements that used similar equipment and methods., Comment: 5 pages and 5 figures. Paper accepted for publication in Phys. Rev. Lett

The binding energies of even-even and odd-odd N=Z nuclei are compared. After correcting for the symmetry energy we find that the lowest T=1 state in odd-odd N=Z nuclei is as bound as the ground state in the neighboring even-even nucleus, thus providing evidence for isovector np pairing. However, T=0 states in odd-odd N=Z nuclei are several MeV less bound than the even-even ground states. We associate this difference with a pair gap and conclude that there is no evidence for an isoscalar pairing condensate in N=Z nuclei., RevTeX, twocolumns, 4 pages, 4 figures. Submitted to Phys. Rev. Lett

Excited states in 52Fe have been determined up to spin 10\hbar in the reaction 28Si + 28Si at 115 MeV by using \gamma-ray spectroscopy methods at the GASP array. The excitation energy of the yrast 10+ state has been determined to be 7.381 MeV, almost 0.5 MeV above the well known \beta+-decaying yrast 12+ state, definitely confirming the nature of its isomeric character. The mean lifetimes of the states have been measured by using the Doppler Shift Attenuation method. The experimental data are compared with spherical shell model calculations in the full pf-shell., Comment: 9 pages, RevTeX, 7 figures included

The levels in 26Na with single particle character have been observed for the first time using the d(25Na,p gamma) reaction at 5 MeV/nucleon. The measured excitation energies and the deduced spectroscopic factors are in good overall agreement with (0+1) hbar-omega shell model calculations performed in a complete spsdfp basis and incorporating a reduction in the N=20 gap. Notably, the 1p3/2 neutron configuration was found to play an enhanced role in the structure of the low-lying negative parity states in 26Na, compared to the isotone 28Al. Thus, the lowering of the 1p3/2 orbital relative to the 0f7/2 occurring in the neighbouring Z=10 and 12 nuclei -- 25,27Ne and 27,29Mg -- is seen also to occur at Z=11 and further strengthens the constraints on the modelling of the transition into the island of inversion., 6 figures