First Evidence of Axial Shape Asymmetry and Configuration Coexistence in

The excited states of N=44 ^{74}Zn were investigated via γ-ray spectroscopy following ^{74}Cu ß decay. By exploiting γ-γ angular correlation analysis, the 2_{2}^{+}, 3_{1}^{+}, 0_{2}^{+}, and 2_{3}^{+} states in ^{74}Zn were firmly established. The γ-ray branching and E2/M1 mixing ratios for transitions deexciting 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}^{+}→0_{2}^{+} and 2_{3}^{+}→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.

Evidence of a Near-Threshold Resonance in

A narrow near-threshold proton-emitting resonance (E_{x}=11.4 MeV, J^{π}=1/2^{+}, and Γ_{p}=4.4 keV) was directly observed in ^{11}B via proton resonance scattering. This resonance was previously inferred in the ß-delayed proton emission of the neutron halo nucleus ^{11}Be. The good agreement between both experimental results serves as a ground to confirm the existence of such exotic decay and the particular behavior of weakly bound nuclei coupled to the continuum. R-matrix analysis shows a sizable partial decay width for both, proton and α (Γ_{α}=11 keV) emission channels.

First Direct Measurement of an Astrophysical p-Process Reaction Cross Section Using a Radioactive Ion Beam.

We have performed the first direct measurement of the ^{83}Rb(p,γ) radiative capture reaction cross section in inverse kinematics using a radioactive beam of ^{83}Rb at incident energies of 2.4 and 2.7A MeV. The measured cross section at an effective relative kinetic energy of E_{cm}=2.393 MeV, which lies within the relevant energy window for core collapse supernovae, is smaller than the prediction of statistical model calculations. This leads to the abundance of ^{84}Sr produced in the astrophysical p process being higher than previously calculated. Moreover, the discrepancy of the present data with theoretical predictions indicates that further experimental investigation of p-process reactions involving unstable projectiles is clearly warranted.

Proton therapy range verification method via delayed γ-ray spectroscopy of a molybdenum tumour marker.

In this work, a new method of range verification for proton therapy (PT) is experimentally demonstrated for the first time. If a metal marker is implanted near the tumour site, its response to proton activation will result in the emission of characteristic γ rays. The relative intensity of γ rays originating from competing fusion-evaporation reaction channels provides a unique signature of the average proton energy at the marker, and by extension the beam's range, in vivo and in real time. The clinical feasibility of this method was investigated at the PT facility at TRIUMF with a proof-of-principle experiment which irradiated a naturally-abundant molybdenum foil at various proton beam energies. Delayed characteristic γ rays were measured with two Compton-shielded LaBr3 scintillators. The technique was successfully demonstrated by relating the relative intensity of two γ-ray peaks to the energy of the beam at the Mo target, opening the door to future clinical applications where the range of the beam can be verified in real time.

Absence of Low-Energy Shape Coexistence in

The ^{80}Ge structure was investigated in a high-statistics ß-decay experiment of ^{80}Ga using the GRIFFIN spectrometer at TRIUMF-ISAC through γ, ß-e, e-γ, and γ-γ 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.

Erratum: Direct Observation of Proton Emission in

This corrects the article DOI: 10.1103/PhysRevLett.123.082501.

Direct Observation of Proton Emission in

The elusive ß^{-}p^{+} decay was observed in ^{11}Be by directly measuring the emitted protons and their energy distribution for the first time with the prototype Active Target Time Projection Chamber in an experiment performed at ISAC-TRIUMF. The measured ß^{-}p^{+} branching ratio is orders of magnitude larger than any previous theoretical model predicted. This can be explained by the presence of a narrow resonance in ^{11}B above the proton separation energy.