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Spin polarization in fragmentation reactions has been studied in several nuclei showing mainly that large polarization is produced at the tail of the fragments momentum distribution. Such polarization features are not so well known in pickup reactions, especially in studies of unstable nuclei, such as 35K and 37K. The spin polarization of 35K and 37K produced in single-proton pickup reactions at intermediate energies at the Coupled Cyclotrons at NSCL and the results for the ground-state magnetic moment involving the /3-NMR technique are reported in the present work.

Observed neutron-capture elemental abundances in metal-poor stars, along with ongoing analysis of the extremely metal-poor Eu-enriched sub-class provide new guidance for astrophysical models aimed at finding the r-process sites. The present paper emphasizes the importance of nuclear physics parameters entering in these models, particularly β -decay properties of neutron-rich nuclei. In this context, several r-process motivated β -decay experiments performed at the National Superconducting Cyclotron Laboratory (NSCL) are presented, including a summary of results and impact on model calculations.

Zhu, S. Janssens, R. V. F. Fornal, B. Freeman, S. J. Honma, M. Broda, R. Carpenter, M. P. Deacon, A. N. Kay, B. P. Kondev, F. G. Krolas, W. Kozemczak, J. Larabee, A. Lauritsen, T. Liddick, S. N. Lister, C. J. Mantica, P. F. Otsuka, T. Pawlat, T. Robinson, A. Seweryniak, D. Smith, J. F. Steppenbeck, D. Tomlin, B. E. Wrzesinski, J. Wang, X.

New high-spin levels have been identified in the nucleus 120Pd from analysis of the coincidence gamma rays observed in the 238U(α, f γ γ γ ) reaction. Recoiling fragments were detected with the Rochester heavy-ion detector array, CHICO, in coincidence with gamma-rays using Gammasphere. An A=110-130 mass-gated γ − γ − γ cube from this experiment was constructed and analyzed for coincident gamma-rays in several nuclei near A=120. New results for neutron-rich 118Pd and 120Pd have been obtained. The 120Pd level scheme was extended to spin of 10+ by building on the new low-energy gamma rays identified in decay studies of 120Rh. The details of the 118Pd level scheme derived from this work are compared to previous work. The systematics of the yrast levels in even-even Pd and Cd isotopes are presented and the symmetry of energy levels around N = 68 is discussed. A new 10+ level in 124Cd has been observed. The population intensity of even-even neutron-rich Cd isotopes is deduced, indicating that nuclides near 120Cd are preferentially populated following alpha-induced fission of 238U.

β-delayed γ-ray measurements have been part of an experimental program at the NSCL to understand the role of the πf7/2 - νf5/2 proton-neutron monopole interaction in neutron-rich pf-shell nuclei above 48Ca. Central to this study has been an attempt to observe the development of new shell structure at N = 32, 34 through the systematic observation of E(2+1 ) as a function of neutron number. Additionally, the ground state spin and parity of odd-odd and odd-A nuclei were interpreted in an extreme single-particle model to follow the monopole migration of the νf5/2 as protons are removed from the πf7/2state.

The beta-decay properties of neutron-rich nuclides in the vicinity of doubly magic 48 Ca, 78 Ni, and 132 Sn have been measured recently using the beta counting system at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. Some of the technical challenges faced by these experiments, including charge-state ambiguities, prompt gamma radiation flash, and presence of beta-decaying isomeric states, are discussed.

New half-lives for neutron-rich ruthenium, rhodium and palladium isotopes close to the r-process path along the N=82 closed shell have been measured at the National Superconducting Cyclotron Laboratory at Michigan State University. The studied isotopes are close to the critical A=118-126 mass region in the astrophysical r-process, where incorrect nuclear structure development towards the shell closure may have the most pronounced effect on the abundances of elements produced. Neutron-rich nuclei were produced by fragmentation of a 120-MeV per nucleon 136 Xe beam on Be and were separated by the A1900 fragment separator. The nuclei of interest were implanted into a double-sided Si strip detector at the center of the MSU β counting system. Charge states and fully- stripped isotopes were distinguished by a measurement of the total kinetic energy of each implant. Our measured half-lives will provide first clues on whether our understanding of nuclear structure evolution in this mass region is correct.

Despite a lot of experimental and theoretical progress the question of the r-process site and the origin of the heavy elements in nature remains one of the biggest open questions in nuclear astrophysics. We report first results from experiments with rare isotope beams of r-process nuclei at Michigan State University’s National Superconducting Cyclotron Laboratory. This includes a first measurement of the half-life of the doubly-magic waiting point nucleus 78Ni, which serves as a major bottle-neck for the synthesis of heavy elements in many r-process models

The regions around the doubly magic nuclei 100 Sn and 78 Ni are of great interest from a nuclear structure standpoint. These nuclei also play a key role in the astrophysical rp- and r-processes, respectively. Recently, nuclei in these regions were studied at the Coupled Cyclotron Facility at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University.

The β decay of neutron-rich nuclei in the π 1 f 7/2 and νpf shells has been studied at the NSCL to track the development of new proposed shell closures at N=32 and 34 due to the monopole migration of the ν 1 f 5/2 orbital. From a measurement of absolute γ -ray intensities following the β decay of odd-odd nuclei, the β -decay branching ratios to levels in the even-even daughters can be deduced. The branching ratios, especially to the 0 + daughter ground state, can be used to assign spins and parities to the parent ground states. The interpretation of these assignments for odd-odd nuclei in a single-particle limit can be used to track the migration of the ν 1 f 5/2 single-particle state.

The odd-odd N=Z nuclide, {sup 78}Y has been produced in the {sup 40}Ca({sup 40}Ca,pn) reaction at 125 MeV. Recoiling fragments separated by their A/Q values were implanted onto the tape of a moving tape collector and transported to a shielded position between two plastic {beta} detectors and two Ge {gamma}-ray detectors where {beta}-{gamma} coincidences were recorded as a function of time. {gamma} rays with energies of 279 (100{percent}), 504 (90{percent}), and 713 (40{percent}) keV, previously identified as yrast transitions in daughter {sup 78}Sr, were observed and found to decay with a half-life of 5.8 (6) s. From the relative intensities of the {gamma}-rays, a spin and parity of 5{sup +} and T=0 are assigned to the parent state in {sup 78}Y undergoing {beta} decay. A production cross section of 4{plus_minus}1{mu}b has been determined for {sup 78}Y by comparison of the counting rates with those of other reaction products with known cross sections. An upper limit of 500 keV can be set for the energy of this level relative to a possible highly deformed T=1 0{sup +} ground state. From this limit, it can be inferred that T=1 pn pairing is considerably quenched relative to such pairing in adjacent odd-odd N=Z more » {sup 74}Rb. Two-quasiparticle rotor model calculations have been used to account for the structure of {sup 78}Y and adjacent nuclides. {copyright} {ital 1998} {ital The American Physical Society} « less

The low energy level structure of neutron-rich 28,29Na has been investigated through β-delayed γ spectroscopy. The present work, which presents the first detailed spectroscopy of 29Na, clearly demonstrates that for Na isotopes between 28Na (N = 17) and 29Na (N = 18), intruder configurations start dominating the low lying excited states, suggestive of the small N = 20 shell gap.

The {beta} decays of very neutron-rich nuclides in the Co-Zn region were studied experimentally at the National Superconducting Cyclotron Laboratory using the NSCL {beta}-counting station in conjunction with the neutron detector NERO. We measured the branchings for {beta}-delayed neutron emission (P{sub n} values) for {sup 74}Co (18{+-}15%) and {sup 75-77}Ni (10{+-}2.8%, 14{+-}3.6%, and 30{+-}24%, respectively) for the first time, and remeasured the P{sub n} values of {sup 77-79}Cu, {sup 79,81}Zn, and {sup 82}Ga. For {sup 77-79}Cu and for {sup 81}Zn we obtain significantly larger P{sub n} values compared to previous work. While the new half-lives for the Ni isotopes from this experiment had been reported before, we present here in addition the first half-life measurements of {sup 75}Co (30{+-}11 ms) and {sup 80}Cu (170{sub -50}{sup +110} ms). Our results are compared with theoretical predictions, and their impact on various types of models for the astrophysical rapid neutron-capture process (r-process) is explored. We find that with our new data, the classical r-process model is better able to reproduce the A=78-80 abundance pattern inferred from the solar abundances. The new data also influence r-process models based on the neutrino-driven high-entropy winds in core collapse supernovae.

Excited states in the neutron-rich 121, 123, 125Ag were studied via the fragmentation of a 136Xe beam at 120MeV/nucleon in a thick 9Be target. The levels in 121Ag were populated in the $ \beta$ decay of 121Pd while those assigned to 123, 125Ag were identified via isomer spectroscopy. The transitions identified in 121Ag are consistent with the $ \gamma$ -rays reported in 117, 119Ag . The newly observed transitions were placed in the level schemes of 123, 125Ag based on the analysis of $ \gamma$ - $ \gamma$ coincidences and the systematics. We attribute the onset of isomerism in the 123, 125Ag isotopes to the drop in energy of the negative-parity levels similar to the 5- state in the even-even Cd cores. The proposed level scheme for 125Ag is well described by the NuShellX shell model calculations.

Low-spin states were studied in $^{30}\mathrm{Al}$ following the \ensuremath{\beta} decay of $^{30}\mathrm{Mg}$ produced in the fragmentation of 140-MeV/AMU $^{48}\mathrm{Ca}$. Analysis of the $\ensuremath{\beta}\text{\ensuremath{-}}\ensuremath{\gamma}$ and $\ensuremath{\beta}\text{\ensuremath{-}}\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidences revealed a new ${1}^{+}$ state at 2413 keV, confirmation of the level scheme, and a more accurate half-life measurement of 315(6) ms for the $^{30}\mathrm{Mg}$ ground state. Higher-spin states were investigated in the reaction of $^{14}\mathrm{C}$ on $^{18}\mathrm{O}$ at 22 MeV. Protons and deuterons were detected in a segmented E-\ensuremath{\Delta}E Si telescope in coincidence with one or two \ensuremath{\gamma} rays in the FSU Ge detector array. A comparison of the resulting level and decay scheme with predictions of the $\mathit{sd}$ shell model shows good agreement with all but six of the states in both excitation energy and \ensuremath{\gamma}-decay branching ratios. The root-mean-square deviations in energy of these states using the older USD and newer USDA and USDB interactions were 265, 176, and 173 keV, respectively. The remaining six states are well described as ${4}^{\ensuremath{-}}$ to ${7}^{\ensuremath{-}}$ states, similar in relative energy to those in $^{28}\mathrm{Al}$ but shifted down by about 1200 keV. These states also agree well with the predictions of shell-model calculations using the WBP interaction. A comparison of the lowest ${4}^{\ensuremath{-}}$ states in even A Na, Al, and P isotopes shows a systematic decrease in energy with increasing N and with decreasing Z. The energies of the ${4}^{\ensuremath{-}}$ states are almost identical in nuclei with the same $N\text{\ensuremath{-}}Z$ values.

The presence of isomeric levels with half-lives in the microsecond range has been identified in $^{125,126,127,128}\mathrm{Cd}$. Neutron-rich Cd isotopes were produced from the fragmentation of a 120 MeV/nucleon $^{136}\mathrm{Xe}$ beam and uniquely identified through their time-of-flight, energy loss, and total kinetic energy. \ensuremath{\gamma} rays from these isomeric levels were measured with an array of Ge detectors that were gated for 15 \ensuremath{\mu}s by a particle implantation trigger from a stack of Si detectors. The \ensuremath{\gamma} rays observed in the decay of $^{126,128}\mathrm{Cd}$ isomers populate low-energy levels previously identified in the \ensuremath{\beta} decay of $^{126,128}\mathrm{Ag}$. The \ensuremath{\gamma} rays found in the decay of $^{125,127}\mathrm{Cd}$ isomers are consistent with expected yrast structures observed in lighter, odd-mass Cd isotopes. The appearance of these isomers at the point where $N/Z$ exceeds 1.6 is interpreted as an indication of the onset of a weakened neutron-neutron interaction that has been proposed for $^{134}\mathrm{Sn}$, whose $N/Z$ also exceeds 1.6.

The structure of the $^{56,58,60}\mathrm{Cr}$ nuclei was investigated at Gammasphere using both deep inelastic and fusion-evaporation reactions. As a result of this work, expanded level schemes are now available for these three neutron-rich, even-even isotopes. Experimental signatures were found for both single-particle and collective excitations whose relative importance varies with neutron number. Together with recent structural information on the odd-$A$ $^{55,57,59}\mathrm{Cr}$ neighbors, the present data highlight the changing role of the ${g}_{9/2}$ orbital with neutron number. Comparisons with shell-model calculations using the recently developed GXPF1A interaction and with total Routhian surface calculations are presented.

The shell structure underlying shape changes in neutron-rich nuclei between $N=20$ and $N=28$ has been investigated by a novel application of the transient field technique to measure the first-excited state $g$ factors in $^{38}\mathrm{S}$ and $^{40}\mathrm{S}$ produced as fast radioactive beams. Details of the new methodology are presented. In both $^{38}\mathrm{S}$ and $^{40}\mathrm{S}$ there is a fine balance between the proton and neutron contributions to the magnetic moments. Shell-model calculations that describe the level schemes and quadrupole properties of these nuclei also give a satisfactory explanation of the $g$ factors. In $^{38}\mathrm{S}$ the $g$ factor is extremely sensitive to the occupation of the neutron ${p}_{3/2}$ orbit above the $N=28$ shell gap as occupation of this orbit strongly affects the proton configuration. The $g$ factor of deformed $^{40}\mathrm{S}$ does not resemble that of a conventional collective nucleus because spin contributions are more important than usual.

The low-energy level structure of the exotic Na isotopes $^{27,28,29}\mathrm{Na}$ has been investigated through \ensuremath{\beta}-delayed \ensuremath{\gamma} spectroscopy. Detailed level structure of $^{28,29}\mathrm{Na}$ has been obtained through $\ensuremath{\beta}\ensuremath{\gamma}$ and $\ensuremath{\beta}\ensuremath{\gamma}\ensuremath{\gamma}$ coincidence measurements. The low-lying levels populated in $^{27}\mathrm{Na}$ by \ensuremath{\beta} decay were found to corroborate well with the in-beam data from the literature. Half-lives of the parent nuclides, $^{27,28,29}\mathrm{Ne}$, were measured using \ensuremath{\beta} fragment as well as fragment $\ensuremath{\beta}\ensuremath{\gamma}$ coincidences and compared to previous measurements. The \ensuremath{\beta}-delayed one- and two-neutron emission branching probabilities have been obtained from the \ensuremath{\gamma} activities of the grand daughter nuclei. A comparison of the level schemes and the \ensuremath{\beta}-decay branching ratios is made with shell-model predictions, both with and without intruder configurations, to understand the transition from normal-dominant to intruder-dominant excitations in these neutron-rich nuclei approaching the island of inversion.

A value of 0.28{+-}0.02 s has been deduced for the half-life of the ground state of {sup 60}Mn, in sharp contrast to the previously adopted value of 51{+-}6 s. Access to the low-spin {sup 60}Mn ground state was accomplished via {beta} decay of the 0{sup +} {sup 60}Cr parent nuclide. New low-energy states in {sup 60}Mn have been identified from {beta}-delayed {gamma}-ray spectroscopy. The new, shorter half-life of {sup 60}Mn{sup g} is not suggestive of isospin-forbidden {beta} decay, and new spin and parity assignments of 1{sup +} and 4{sup +} have been adopted for the ground and isomeric {beta}-decaying states, respectively, of {sup 60}Mn.

The shell structure underlying shape changes in neutron-rich nuclei near N=28 has been investigated by a novel application of the transient-field technique to measure the first-excited-state g factors in {sup 38}S and {sup 40}S produced as fast radioactive beams. There is a fine balance between proton and neutron contributions to the magnetic moments in both nuclei. The g factor of deformed {sup 40}S does not resemble that of a conventional collective nucleus because spin contributions are more important than usual.

The nuclear magnetic moment of the ground state of $^{57}\mathrm{Cu}({I}^{\ensuremath{\pi}}=3/{2}^{\ensuremath{-}},{T}_{1/2}=196.3\text{ }\text{ }\mathrm{ms})$ has been measured to be $|\ensuremath{\mu}(^{57}\mathrm{Cu})|=(2.00\ifmmode\pm\else\textpm\fi{}0.05){\ensuremath{\mu}}_{N}$ using the $\ensuremath{\beta}$-NMR technique. Together with the known magnetic moment of the mirror partner $^{57}\mathrm{Ni}$, the spin expectation value was extracted as $⟨\ensuremath{\Sigma}{\ensuremath{\sigma}}_{z}⟩=\ensuremath{-}0.78\ifmmode\pm\else\textpm\fi{}0.13$. This is the heaviest isospin $T=1/2$ mirror pair above the $^{40}\mathrm{Ca}$ region for which both ground state magnetic moments have been determined. The discrepancy between the present results and shell-model calculations in the full $fp$ shell giving $\ensuremath{\mu}(^{57}\mathrm{Cu})\ensuremath{\sim}2.4{\ensuremath{\mu}}_{N}$ and $⟨\ensuremath{\Sigma}{\ensuremath{\sigma}}_{z}⟩\ensuremath{\sim}0.5$ implies significant shell breaking at $^{56}\mathrm{Ni}$ with the neutron number $N=28$.

{beta}-delayed neutron emission branchings (or upper limits) for neutron rich {sup 116-120}Rh, {sup 120-122}Pd, and {sup 124}Ag have been measured. These branching ratios serve as direct inputs to astrophysical rapid neutron capture process models and affect the final abundances calculated in these models. In addition, half-lives for neutron rich {sup 114-115}Tc, {sup 114-118}Ru, {sup 116-121}Rh, and {sup 119-124}Pd near the proposed path of the r-process have also been measured. The results agree with theoretical quasiparticle random-phase approximation calculations within model uncertainties; the only exception is the delayed neutron branching in the decay of {sup 120}Rh, which is found to be much smaller than predicted.

The ground state magnetic moment of $^{35}\mathrm{K}$ has been measured using the technique of nuclear magnetic resonance on \ensuremath{\beta}-emitting nuclei. The short-lived $^{35}\mathrm{K}$ nuclei were produced following the reaction of a $^{36}\mathrm{Ar}$ primary beam of energy 150 MeV/nucleon incident on a Be target. The spin polarization of the $^{35}\mathrm{K}$ nuclei produced at 2\ifmmode^\circ\else\textdegree\fi{} relative to the normal primary beam axis was confirmed. Together with the mirror nucleus $^{35}\mathrm{S}$, the measurement represents the heaviest $T=3/2$ mirror pair for which the spin expectation value has been obtained. A linear behavior of ${g}_{p}$ vs ${g}_{n}$ has been demonstrated for the $T=3/2$ known mirror moments and the slope and intercept are consistent with the previous analysis of $T=1/2$ mirror pairs.

The low-energy level structure of $^{25}\mathrm{Ne}$ has been investigated following the ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of $^{25}\mathrm{F}$. Beta-delayed \ensuremath{\gamma} spectroscopy revealed new \ensuremath{\gamma} transitions in $^{25}\mathrm{Ne}$ at 1234, 1622, and 2090 keV. The new transitions were placed in the level scheme of $^{25}\mathrm{Ne}$ in accordance with the observed $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidences. The total ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay strength has been accounted for. The spins and parities of the first two excited states could be ascertained by comparison with a shell model calculation and the literature. The half-life for $^{25}\mathrm{F}$ decay was also remeasured using fragment-$\ensuremath{\beta}\text{\ensuremath{-}}\ensuremath{\gamma}$ correlations, revealing a value of 90 \ifmmode\pm\else\textpm\fi{} 9 ms. Comparison with shell model calculations are indicative of a wider $N=16$ gap as compared to the stable nuclei.

The nuclear magnetic moment of the ground state of (57)Cu(Iota(pi) = 3/2(-), T(1/2) = 196.3 ms) has been measured to be /mu((57)Cu)/ = (2.00 +/- 0.05)mu(N) using the beta-NMR technique. Together with the known magnetic moment of the mirror partner (57)Ni, the spin expectation value was extracted asSigmasigma(z)= -0.078 +/- 0.13. This is the heaviest isospin mirror T = 1/2 pair above the (40)Ca region for which both ground state magnetic moments have been determined. The discrepancy between the present results and shell-model calculations in the full f p shell giving mu((57)Cu) approximately 2.4mu(N) andSigmasigma(z)approximately 0.5 implies significant shell breaking at (56)Ni with the neutron number N = 28.

The shell structure underlying shape changes in neutron-rich nuclei near N = 28 has been investigated by a novel application of the transient-field technique to measure the first-excited-state g factors in 38S and 40S produced as fast radioactive beams. There is a fine balance between proton and neutron contributions to the magnetic moments in both nuclei. The g factor of deformed 40S does not resemble that of a conventional collective nucleus because spin contributions are more important than usual.

The {beta}-decay of odd-A, neutron-rich {sup 57}Ti and {sup 59}V are studied. More precise {beta}-decay half-lives of 98{+-}5 and 97{+-}2 ms are deduced for {sup 57}Ti and {sup 59}V, respectively. In addition, {beta}-delayed {gamma}-ray spectroscopy is used to deduce {beta}-decay branching ratios and establish the low-energy-level structures of the daughter nuclides. The new data for levels in {sup 57}V and {sup 59}Cr are compared with the results of shell-model calculations completed in the full pf model space. Both {sup 57}V and {sup 59}Cr show evidence of modest oblate deformation near the ground state.

{gamma} rays from neutron-rich Ti nuclei in the vicinity of N=32 have been studied at Gammasphere using deep-inelastic reactions induced by {sup 48}Ca beams on thick {sup 208}Pb and {sup 238}U targets. The {sup 53}Ti yrast cascade was identified for the first time, and the location in energy of states with spin up to I = 21/2 was determined. The excitations of {sup 53}Ti provide new tests of effective interactions for full-pf-shell calculations. Comparisons between theory and experiment for the highest spin states in {sup 53}Ti favor the recently proposed GXPF1A interaction, which accounts for the appearance of a neutron subshell closure at N=32 in Ti isotopes as well as for the lack of a similar subshell closure at N=34, as predicted by earlier calculations with another interaction.

The low-energy level structure of the exotic Na isotopes (28,29)Na has been investigated through beta-delayed gamma spectroscopy. The N=20 isotones for Z=10-12 are considered to belong to the "island of inversion" where intruder configurations dominate the ground state wave function. However, it is an open question as to where and how the transition from normal to intruder dominated configurations happens in an isotopic chain. The present work, which presents the first detailed spectroscopy of (28,29)Na, clearly demonstrates that such a transition in the Na isotopes occurs between 28Na (N=17) and 29Na (N=18), supporting the smaller N=20 shell gap in neutron-rich sd shell nuclei. The evidence for inverted shell structure is found in beta-decay branching ratios, intruder dominated spectroscopy of low-lying states, and shell model analysis.

Nuclei with magic numbers serve as important benchmarks in nuclear theory. In addition, neutron-rich nuclei play an important role in the astrophysical rapid neutron-capture process (r process). 78Ni is the only doubly magic nucleus that is also an important waiting point in the r process, and serves as a major bottleneck in the synthesis of heavier elements. The half-life of 78Ni has been experimentally deduced for the first time at the Coupled Cyclotron Facility of the National Superconducting Cyclotron Laboratory at Michigan State University, and was found to be 110(+100)(-60) ms. In the same experiment, a first half-life was deduced for 77Ni of 128(+27)(-33) ms, and more precise half-lives were deduced for 75Ni and 76Ni of 344(+20)(-24) ms and 238(+15)(-18) ms, respectively.

The structure and decay of neutron‐rich r‐process nuclides has been studied by a variety of means that take advantage of enhanced selectivity to permit identification of exotic nuclides. New level structures are presented for 134,135Sb along with data for Ag isomers and Cd yrast structures. Some of the properties measured play an important role in calculations of the yields of elements and isotopes produced in r‐process nucleosynthesis that takes place at high temperature in the presence of large densities of neutrons.

The possible occurrence of sub‐shell gaps at N = 32 and N = 34 in neutron‐rich titanium isotopes is discussed in light of new experimental results from (i) deep‐inelastic reactions measured with Gammasphere at the ATLAS facility at Argonne National Laboratory and from (ii) intermediate‐energy Coulomb excitation performed at the National Superconducting Cyclotron Laboratory at Michigan State University.

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.

Gamma rays from neutron-rich nuclei in the vicinity of $Z=20$, $N=28$ have been studied at Gammasphere using deep-inelastic reactions induced by a $330\text{\ensuremath{-}}\mathrm{MeV}$ $^{48}\mathrm{Ca}$ beam on a thick $^{238}\mathrm{U}$ target. The yrast $\ensuremath{\gamma}$-ray cascade of $^{56}\mathrm{Ti}$ was identified for the first time and the location in energy of the ${2}^{+}$, ${4}^{+}$, and ${6}^{+}$ states was determined. The low-spin $^{56}\mathrm{Ti}$ yrast structure does not support the presence of a subshell closure at $N=34$ as suggested on the basis of other data on nuclei in the region as well as shell model calculations with a recently proposed interaction.

The low-energy level structure of the exotic Na isotopes (28,29)Na has been investigated through beta-delayed gamma spectroscopy. The N=20 isotones for Z=10-12 are considered to belong to the "island of inversion" where intruder configurations dominate the ground state wave function. However, it is an open question as to where and how the transition from normal to intruder dominated configurations happens in an isotopic chain. The present work, which presents the first detailed spectroscopy of (28,29)Na, clearly demonstrates that such a transition in the Na isotopes occurs between 28Na (N=17) and 29Na (N=18), supporting the smaller N=20 shell gap in neutron-rich sd shell nuclei. The evidence for inverted shell structure is found in beta-decay branching ratios, intruder dominated spectroscopy of low-lying states, and shell model analysis.

The low-energy levels of $^{120}\mathrm{Pd}_{74}$ were populated by $\ensuremath{\beta}$ decay of $^{120}\mathrm{Rh}_{75}$, which was produced via projectile fragmentation of a $^{136}\mathrm{Xe}_{82}$ beam at $120\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}∕\text{nucleon}$. Delayed $\ensuremath{\beta}$-gated $\ensuremath{\gamma}$ rays with energies of 438 and $618\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$ were observed in coincidence with $^{120}\mathrm{Rh}_{75}$ fragments and assigned to the ${2}_{1}^{+}\ensuremath{\rightarrow}{0}^{+}$ and ${4}_{1}^{+}\ensuremath{\rightarrow}{2}_{1}^{+}$ transitions, respectively, in $^{120}\mathrm{Pd}_{74}$. Isomeric $\ensuremath{\gamma}$-ray transitions are also reported for $^{120}\mathrm{Rh}_{75}$ and $^{126}\mathrm{Cd}_{78}$. The low-energy structure of $^{120}\mathrm{Pd}_{74}$ shows remarkable similarity to those of the isotopic $^{108}\mathrm{Pd}_{62}$ and isotonic $^{128}\mathrm{Xe}_{74}$ suggesting that these nuclides share the same $Z=50$ and $N=82$ closed shell structures with neutron-rich $^{120}\mathrm{Pd}_{74}$.

Recent experimental characterization of the subshell closure at $N=32$ in the Ca, Ti, and Cr isotones has stimulated shell-model calculations that indicated the possibility that the $N=34$ isotones of these same elements could exhibit characteristics of a shell closure, namely, a high energy for the first excited ${2}^{+}$ level. To that end, we have studied the decay of $^{56}\mathrm{S}\mathrm{c}$ produced in fragmentation reactions and identified new $\ensuremath{\gamma}$ rays in the daughter $N=34$ isotone $^{56}\mathrm{T}\mathrm{i}$. The first ${2}^{+}$ level is found at an energy of 1127 keV, well below the expected position that would indicate the presence of an $N=34$ shell closure in $^{56}\mathrm{T}\mathrm{i}$.

Recent experimental characterization of the subshell closure at N=32 in the Ca, Ti, and Cr isotones has stimulated shell-model calculations that indicated the possibility that the N=34 isotones of these same elements could exhibit characteristics of a shell closure, namely, a high energy for the first excited 2(+) level. To that end, we have studied the decay of 56Sc produced in fragmentation reactions and identified new gamma rays in the daughter N=34 isotone 56Ti. The first 2(+) level is found at an energy of 1127 keV, well below the expected position that would indicate the presence of an N=34 shell closure in 56Ti.

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.

The nuclear magnetic moment of the ground state of 57Cu(Iπ = 3/2-, T1/2 = 196.3 ms) has been measured to be |μ(57Cu)| = (2.00 ±0.05) μN using the β-NMR technique. Together with the known magnetic moment of the mirror partner 57Ni, the spin expectation value was extracted as $\langle\sum\sigma_z\rangle$ = -0.78 ± 0.13. Discrepancy between present results and shell model calculations in the full fp shell implies significant shell breaking at 56Ni with the neutron number N = 28.

Gamma rays have been identified in the decay of isomers in 125,126,127Cd, 123,124,125Ag, 121Pd, 120Rh, and 117Ru that provide information about the low-energy structures of these nuclei. In turn, comparison of low-energy levels in the Cd and Te isotones reveals that, whereas the yrast structures in the Te isotopes rise smoothly as N approaches the closed shell at 82, the 15/2- to 11/2- transitions level off as N exceeds 76. This is identified as the point where the Cd isotopes undergo a phase transition and become “neutron rich”.

We have utilized the selective process of β decay to populate low-energy excited states in the neutron-rich 22Ti, 23V, 24Cr, and 25Mn nuclei. The goal was to systematically track the monopole shift of the νf5/2 single-particle level with increased occupancy of the πf7/2 orbital. The β-decay properties of the parent nuclides, along with the low-energy structure of the daughters, are presented and compared with the results of shell model calculations employing the GXPF1 interaction.

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.