[en] Electromagnetic transitions in ²²F were investigated using the ⁹Be(¹⁴C, p) reaction at E_lab=22 MeV. Proton-γ and proton-γ-γ coincidences were measured using a segmented E-ΔE Si telescope and the Florida State University γ detector array. γ-ray energies, intensities, and branching ratios were measured, and mean lifetimes were inferred using the Doppler-shift attenuation method. Several new states and many new γ-decay branches were observed. The results are compared with sd shell model calculations using the USD, USDA, and USDB interactions. The excitation energies of the states below 2 MeV agree slightly better with the calculations using the USD interaction, while the levels between 2 and 4 MeV agree somewhat better with those using the newer USDA and USDB interactions

No abstract available

[en] A Reply to the Comment by D. T. Yordanov et al.

[en] High-spin states in 187Pt have been studied by means of γ-ray spectroscopy techniques. Known bands have been significantly extended and new bands have been found. The band structures are briefly discussed

[en] Here, the rate of the T=1, 2+ to T=1, 0⁺ transition in ¹⁰B (T=1, T_z=0) is compared to the analog transitions in ¹⁰Be (T=1, T_z=–1) and ¹⁰C (T=1, T_z=+1) to provide constraints on ab initio calculations using realistic nuclear forces. The relevant state in ¹⁰B, at E_x=5.164 MeV, is particle unbound. Therefore, a determination of the B(E2) electromagnetic transition rate requires a precise and accurate determination of the width of the state, as well as the α-particle and γ-ray branching ratios. Previous measurements of the α-particle branching ratio are just barely in agreement. We report on a new study of the α-particle branch by studying the ¹⁰B(p,p')¹⁰B* reaction in inverse kinematics with the HELIOS spectrometer. The α-particle branching ratio that we observe, 0.144±0.027, is in good agreement with the evaluated value and improves the associated uncertainty. The resulting experimental B(E2) value is 7.0±2.2 e²fm⁴ and is more consistent with a flat trend across the A=10 triplet than previously reported. This is inconsistent with Green's function Monte Carlo predictions using realistic three-nucleon Hamiltonians, which overpredict the B(E2) value in ¹⁰C and ¹⁰B.

[en] Low-spin states were studied in ³⁰Al following the β decay of ³⁰Mg produced in the fragmentation of 140-MeV/AMU ⁴⁸Ca. Analysis of the β-γ and β-γ-γ 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 ³⁰Mg ground state. Higher-spin states were investigated in the reaction of ¹⁴C on ¹⁸O at 22 MeV. Protons and deuterons were detected in a segmented E-ΔE Si telescope in coincidence with one or two γ rays in the FSU Ge detector array. A comparison of the resulting level and decay scheme with predictions of the sd shell model shows good agreement with all but six of the states in both excitation energy and γ-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^- to 7^- states, similar in relative energy to those in ²⁸Al 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^- 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^- states are almost identical in nuclei with the same N-Z values

[en] Spectroscopic studies of nuclei in the A∼250, Z∼100 region provide critical input to theoretical models that attempt to describe the structure and stability of the heaviest elements. We report here on new spectroscopic studies in the N = 150,151 nuclei ^244,245Pu. (Z = 94). Excitations in these nuclei on the neutron-rich side of the valley of stability, accessed via inelastic and transfer reactions, complement fusion-evaporation studies of Z≥100 nuclei. States in ^244,245Pu were populated using ⁴⁷Ti and ²⁰⁸Pb beams incident on a ²⁴⁴Pu target, with delayed and prompt gamma rays detected by the Gammasphere array. The new results are discussed in the context of emerging systematics of one- and two-quasiparticle excitations in N≥150 nuclei.

[en] A study of low-lying excited states in Z = 51 isotopes has been performed using single-proton adding reactions, (α,t) and (³He,d), on the series of stable, even mass Z = 50 isotopes. Our goal was to build upon results from a previous (α,t) study [1] by examining the fragmentation of high-j (g_7/2 and h_11/2) single-proton strengths utilising greater statistics. Data from the (³He,d) measurements provide further information regarding the low-j orbitals within this nuclear shell. Preliminary findings from the analysis are presented in this report.

[en] The energy of the lowest deformed 2-particle 2-hole (2p2h) 0⁺ state in even-even N = 20 nuclei is a key observable directly related to the size of the neutron N = 20 shell closure. ³⁴Si, with 14 protons and 20 neutrons, lies at the boundary of the ⁱsland of inversion^, where the deformed 2p2h 0⁺ state is the ground state in even-A nuclei. In ³⁴Si, the 2p2h 0⁺ state is expected to be particularly low lying - in some theories it is even predicted to lie below the first 2⁺ state. While there have been a number of attempts, using various techniques, no experiment to date has been able to firmly locate the ³⁴Si 2p2h 0⁺ state although a number of candidates have been suggested. Here we present, for the first time, data obtained from a fusion-evaporation reaction ¹⁸O(¹⁸O, 2p) to produce ³⁴Si. Gammasphere and Microball were used to detect γ-γ coincidences and charged particles (two protons), respectively. The increased sensitivity of this experiment using γ-γ coincidences and a high charged-particle detection efficiency helped to exclude previously reported candidates and provided a stringent limit on the anticipated γ decay from the first 2⁺ state to the 2p2h 0⁺ state.

[en] High-spin states in ⁷¹As were studied using the ⁵⁴Fe(²³Na,α2p) reaction at 80 MeV. Prompt γ-γ coincidences were measured using the Florida State University Compton-suppressed Ge array consisting of three clover detectors and seven single-crystal detectors. The existing high-spin level scheme has been verified, and 21 new transitions have been added based on an investigation of weak γ-ray coincidence relations and relative γ-ray intensities. Lifetimes of 16 excited states were measured using the Doppler-shift attenuation method applied to the experimental line shapes of decays in all of the known rotational bands. The B(E2) strengths inferred from the lifetimes indicate that moderate to high collective behavior persists to the highest observed spins in the lowest positive- and negative-parity bands, in qualitative agreement with projected shell-model calculations. The band suggested to be based on the πf_7/2 orbital shows a similar degree of collectivity within the same spin range, with B(E2) values in good agreement with those predicted by the projected shell model assuming a constant prolate deformation of ε₂=+0.27. The experimental Q_t values in this band are somewhat smaller than predicted by cranked Woods-Saxon calculations.