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The mass of 27P is expected to impact the X-ray burst (XRB) model predictions of burst light curves and the composition of the burst ashes, but large uncertainties and inconsistencies still exist in the reported 27P masses. We have used the β-decay spectroscopy of 27S to determine the most precise mass excess of 27P to date to be −659(9) keV, which is 63 keV (2.3σ) higher and a factor of 3 more precise than the value recommended in the 2016 Atomic Mass Evaluation. Based on the new 27P mass, the Si26(p,γ)27P reaction rate and its uncertainty were recalculated using Monte Carlo techniques. We also estimated the previously unknown mass excess of 27S to be 17678(77) keV, based on the measured β-delayed two-proton energy and the Coulomb displacement energy relations. The impact of these well-constrained masses and reaction rates on the modeling of the explosive astrophysical scenarios has been investigated by post-processing XRB and hydrodynamic nova models. Compared to the model calculations based on the masses and rates from databases, the abundance of A=26 in the burst ashes is increased by a factor of 2.4, while no substantial change was found in the XRB energy generation rate or the light curve. Our calculation also suggests that 27S is not a significant waiting point in the rapid proton capture process, and the change of the Si26(p,γ)27P reaction rate is not sufficiently large to affect the conclusion previously drawn on the nova contribution to the synthesis of galactic 26Al. Keywords: Masses of 27P and 27S, Si26(p,γ)27P reaction, X-ray bursts, Nova outbursts

Excited states in 63,65,67Mn were studied via in-beam γ-ray spectroscopy following knockout reactions from 68Fe. Similar level schemes, consisting of the 11/2−, 9/2−, 7/2− and 5/2g.s.− level sequence, connected by I→I−1 transitions, were established, the first time for 65,67Mn. Their level structures show features consistent with strongly-coupled rotational bands with K=5/2. State-of-the-art shell-model calculations with the modified LNPS effective interaction reproduce the observed levels remarkably well and suggest the dominance of 4-particle-4-hole neutron configurations for all the states. The data on the low-lying excited states of odd-mass 53−67Mn provide a textbook example of nuclear structure evolution from weak coupling through decoupling to strong coupling along a single isotopic chain on the n-rich side of the β stability line. These results help to deepen our understanding of the N=40 “island of inversion”. Keywords: In-beam γ-ray spectroscopy, “Island of inversion” around N=40, Strong coupling, Structure evolution

Fine structure in the α decay of 223U was observed in the fusion-evaporation reaction 187Re(40Ar, p3n) by using fast digital pulse processing technique. Two α-decay branches of 223U feeding the ground state and 244 keV excited state of 219Th were identified by establishing the decay chain 223U →α1 219Th →α2 215Ra →α3 211Rn. The α-particle energy for the ground-state to ground-state transition of 223U was determined to be 8993(17) keV, 213 keV higher than the previous value, the half-life was updated to be 62−10+14 μs. Evolution of nuclear structure for N = 131 even-Z isotones from Po to U was discussed in the frameworks of nuclear mass and reduced α-decay width, a weakening octupole deformation in the ground state of 223U relative to its lighter isotones 219Ra and 221Th was suggested. Keywords: Fine structure, α decay, Spin and parity, Reduced α-decay width, Quadrupole-octupole deformation