Search

The level structure of 5422Ti32 has been explored for the first time by combining β-decay measurements from fragmentation products with prompt γ-ray spectroscopy following deep inelastic reactions. The latter technique was also instrumental in tracing 52Ti30 to higher spin. The data provide new tests of effective interactions for full pf-shell calculations in neutron-rich nuclei above 48Ca. The data indicate the presence of a significant subshell gap at N=32 and comparisons between theory and experiment suggest an additional shell closure at N=34 in Ca and Ti isotopes.

An 879.9(2) keV γ -ray transition has been identified following the β decay of 58 V and assigned as the 2 + 1 →0 + 1 transition in 58 Cr 34 . A peak in the energies of the first excited 2 + states for the even–even chromium isotopes is now evident at 56 Cr 32 , providing empirical evidence for a significant subshell gap at N =32. The appearance of this neutron subshell closure for neutron-rich nuclides may be attributed to the diminished π 1 f 7/2 – ν 1 f 5/2 monopole proton–neutron interaction as protons are removed from the 1 f 7/2 single-particle orbital.

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.

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 kinematical model that considers conservation of linear and angular momentum and assumes peripheral interactions between the fast projectile and target. Improvements to the kinematical model are discussed that aim to achieve quantitative agreement with spin polarization data from both the nucleon removal and pickup processes.

Details regarding the $\ensuremath{\beta}$-decay properties of $^{54,55,56}\mathrm{Sc}$ are reported and compared with shell model predictions. The low-energy level structures of even-even $^{54,56}\mathrm{Ti}$ are presented, and the systematic variation of the energy of the first excited ${2}_{1}^{+}$ state is discussed in light of proposed shell closures at $N=32,34$ for the neutron-rich $\mathrm{Ti}$ isotopes.

Spin polarization of 37K nuclei produced via single proton pickup from a 9Be target by a beam of 150 MeV/nucleon 36Ar has been observed. Positive spin polarization with magnitude (8.5+/-0.6)% was deduced near the peak of the 37K momentum distribution. The variation of the spin polarization as a function of outgoing 37K momentum is explained by a classical conservation model, as previously applied to describe the induced spin polarization observed for fragments produced in intermediate-energy heavy-ion reactions, with the condition that the picked-up proton has an average momentum equal to the Fermi momentum and is aligned along the incident beam direction.

$\ensuremath{\beta}$ decay of ${}^{56,57,58}\mathrm{V}$ has been used to populate low-energy levels of ${}^{56,57,58}\mathrm{Cr},$ respectively. The low-energy levels of the even-even Cr isotopes and $\ensuremath{\beta}$-decay half-lives and branching ratios of the parent V isotopes are compared to results of shell-model calculations. The Cr energy level calculations were completed in the full $\mathrm{pf}$-model space, using several different interactions. The systematic variation of ${E(2}_{1}^{+}),$ which is indicative of a subshell closure at $N=32,$ was best reproduced in calculations using a pf-shell-model interaction based on effective two-body matrix elements with some replacement by the G matrix.

We report on the low‐energy structure of the neutron‐rich, even‐even nuclides 54Ti32, 56Cr32, and 58Cr34 studied via β‐delayed γ‐ray spectroscopy. The systematic variation of the excitation energy of first excited 2+ states in the even‐even 24Cr and 22Ti isotopes provides evidence of a subshell closure at N = 32 for neutron‐rich nuclides having Z ⩽ 24. Shell model calculations, which correctly account for the appearance of the N = 32 subshell, also predict a new shell closure at N = 34 for Ti and Ca isotopes.

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.

The g factors of the ${2}_{1}^{+}$ states of the stable, even-even Mo isotopes ${}^{92,94,96,98,100}\mathrm{Mo}$ were measured using the transient field method. While ${}^{92}{\mathrm{Mo}}_{50}$ has a g factor consistent with that of the $\ensuremath{\pi}{g}_{9/2}^{2}$ configuration, the g factor of ${}^{94}\mathrm{Mo}$ is about 60% of the hydrodynamic model value, $Z/A.$ As further pairs of neutrons are added, the heavier isotopes ${}^{96,98,100}\mathrm{Mo}$ show a monotonic increase in ${g(2}^{+})$ to values that exceed $Z/A$ for ${}^{98}\mathrm{Mo}$ and ${}^{100}\mathrm{Mo}.$ The systematic behavior of the ${g(2}_{1}^{+})$ values for the Mo isotopes, as one moves away from the neutron shell closure at $N=50,$ is compared with the shell model, a collective model with pairing corrections and IBM-2 calculations.