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The slow β-decay of the 68Se waiting point in the astrophysical rp-process can in principle be bypassed by a sequential two proton capture. The rate of this reaction sequence depends exponentially on the 69Br proton separation energy. We studied β-delayed proton emission of 69Kr and extracted a proton separation energy of − 641 ( 42 ) keV . In addition, we determined a 69Kr β-decay half-life of T 1 / 2 = 28 ( 1 ) ms and an excitation energy of 3153(55) keV of the 69Kr isobaric analog state in 69Br. X-ray burst model calculations show that regardless of the values of other uncertain masses in the region, the new S p ( Br 69 ) allows for a reaction flow via Se 68 ( 2 p , γ ) of at most 20%. Uncertainties are sufficiently reduced to conclude that Se 68 ( 2 p , γ ) has at best a very small effect on burst light curve and composition, and that 68Se is a strong rp-process waiting point. Our results also exclude the possibility of a suggested longer lived, so far unobserved, 69Br ground state.

The dependence of the spin polarization on the incident angle of the primary beam has been measured for {sup 12}B fragments produced in the fragmentation of an {sup 18}O beam on a Nb target at 80 MeV/nucleon. A change in sign of the spin polarization was observed with a change in sign of the incident angle of the projectile. This result is in agreement with the kinematical model presented recently to qualitatively describe the mechanism for the production of spin-polarized fragments following intermediate-energy heavy-ion reactions. The resonance curve for {sup 12}B has also been measured using a technique of multiple adiabatic fast passage with continuous implantation. This technique is briefly compared to the single-pass adiabatic fast passage method employed with beam-on/beam-off data acquisition. {copyright} {ital 1997} {ital The American Physical Society}

The isomeric and $\beta$-decay properties of neutron-rich $^{53-57}$Sc and $^{53,54}$Ca nuclei near neutron number $N$=32 are reported, and the low-energy level schemes of $^{53,54,56}$Sc and $^{53-57}$Ti are presented. The low-energy level structures of the $_{21}$Sc isotopes are discussed in terms of the coupling of the valence $1f_{7/2}$ proton to states in the corresponding $_{20}$Ca cores. Implications with respect to the robustness of the $N$=32 subshell closure are discussed, as well as the repercussions for a possible $N$=34 subshell closure., Comment: 17 pages, 17 figures, accepted to Phys. Rev. C

Intermediate-energy heavy-ion collisions can produce a spin polarization of the projectile-like species. Spin polarization has been observed for both nucleon removal and nucleon pickup processes. Qualitative agreement with measured spin polarization as a function of the momentum of the projectile-like fragment is found in a kinematic model that considers conservation of linear and angular momentum and assumes peripheral interactions between the fast projectile and target. Better quantitative agreement was reached by including more realistic angular distributions and deorientation caused by {gamma}-ray emission and by correcting for the out-of-plane acceptance. The newly introduced corrections were found to apply to both nucleon removal and nucleon pickup processes.

32 Mg lies within a region of deformed nuclei commonly referred to as the “island of inversion”. The β decay of 33 Al and 33 Mg has been studied to learn about nuclear structure near 32 Mg. Decay curves and precise half-life measurements are presented for both species. Gamma-ray spectra from correlated 33 Al decay events are also presented. The β -decay properties of 33 Al are shown to be well-described by an sd shell model calculation, suggesting that the ground state of 33 Al lies primarily outside the island of inversion.

Matière Nucléaire; The decays of ${}^{119m}$Cs and ${}^{119g}$Cs to ${}^{119}$Xe have been studied on mass separated samples, using $\gamma\rm{-ray}$ and internal conversion electron measurements. Several new low-lying levels have been established in the ${}^{119}$Xe level scheme. Half-life evaluations for ${}^{119m}$Cs and ${}^{119g}$Cs have been revisited. The results are compared with other experimental data known in light odd-mass xenon isotopes and with calculations performed in the frame of the multi-shell interacting boson-fermion model.

Transient-field strengths for Mg ions traversing Gd hosts have been measured above the K-shell electron velocity. The results support a recent model-based extrapolation of the transient-field strength and show sufficient magnitude for g-factor measurements on exotic nuclei near the island of inversion around 32Mg produced as intermediate-energy fragments.

First experimental evidence for a high-spin isomer ( 25 / 2 + ) in 97Cd, a waiting point in the astrophysical rapid proton capture process, is presented. The data were obtained in β-decay studies at NSCL using the new RF Fragment Separator system and detecting β-delayed protons and β-delayed γ rays. Decays from ground and isomeric states were disentangled, and proton emission branches were determined for the first time. We find half-lives of 1.10(8) s and 3.8(2) s, and β-delayed proton emission branches of 12(2)% and 25(4)% were deduced for the ground and isomeric states, respectively. With these results, the nuclear data needed to determine an rp-process contribution to the unknown origin of solar 96Ru are in place. When the new data are included in astrophysical rp-process calculations, one finds that an rp-process origin of 96Ru is unlikely.