It is shown that addition of a two-body magnetic dipole operator arising from the exchange of the isovector pion and rho meson to the well-known one-body operator can give important corrections to the magnetic dipole moments of the A=4–16 nuclei. We performed shell-model calculations in complete 0ħω and (0+2)ħω model spaces, thus investigating simultaneously the effects of extension of the model space and meson exchange currents on the magnetic moments. In the enlarged model space a significant improvement on the description of the magnetic moments is obtained by including exchange currents.

We have measured the widths of the 3/$2^{\mathrm{-}}$ ground states of ${}_{}{}^5{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^5{}_{}{}^{}\mathrm{Li}$ using the ${}_{}{}^3{}_{}{}^{}\mathrm{H}$(d,γ${)}^5$He and the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(d,γ${)}^5$Li reactions at ${\mathit{E}}_{\mathit{d}}$=8.6 MeV. The γ-ray spectra were fitted with a convolution of the NaI line-shape response function, as measured with the ${}_{}{}^3{}_{}{}^{}\mathrm{H}$(p,γ${)}^4$He reaction, and a Breit-Wigner single-level expression. The widths extracted from the spectra were found to be ${\mathrm{\Gamma }}_{\mathit{n}}$=1.36±0.19 MeV for ${}_{}{}^5{}_{}{}^{}\mathrm{He}$, and ${\mathrm{\Gamma }}_{\mathit{p}}$=2.44±0.21 MeV for ${}_{}{}^5{}_{}{}^{}\mathrm{Li}$. These values, significantly different from previously quoted measurements, lead to reduced widths which are equal to within error, a result which is consistent with the charge-symmetry property of the nuclear force.

The isolated peak that is populated by the ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$(p,${\mathrm{\pi }}^{+}$) reaction at an excitation energy of 21.5 MeV in ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ has been proposed to be of high spin (15/$2^{\mathrm{-}}$) and of a configuration of ${}_{}{}^{14}{}_{}{}^{}\otimes$(${\mathit{p}}_{3/2}$${)}^{\mathrm{-}1}$(${\mathit{d}}_{5/2}$${)}^2$. No peak at the excitation energy of 21.5 MeV is observed with the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$${(}^7$Li,t) reaction at bombarding energies of 34, 40, and 45 MeV. States with a ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$+α configuration are observed at 13.85, 17.05, and 22.86 MeV.

We have added a new measurement at 100 MeV/nucleon to our previous excitation function for collective flow of light fragments from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{51}$V collisions. In the earlier work, flow decreased as the beam energy was raised from 45 to 85 MeV/nucleon. This provided hints to the disappearance of flow, but the lack of measurements at higher beam energies precluded the observation of the reappearance of flow. At a beam energy of 100 MeV/nucleon the flow has reappeared and this allows an experimental determination of the region where attractive scattering balances with repulsive scattering in these collisions. A simultaneous least-squares fit of the flow data for light fragments yields (85±10) MeV/nucleon for the balance energy.

We study the different mechanisms for the fragmentation of the giant dipole resonance in medium-mass nuclei with triaxial shape, by resorting to group-theoretical techniques. Coupling between low- and high-lying collective modes is considered, together with isospin effects, within the framework of the interacting boson model. An application to titanium isotopes is presented.

We investigate a recent suggestion that the Nolen-Schiffer anomaly can be resolved if the in-medium proton-neutron mass difference is substantially changed from its free space value. In a number of hadronic models, such an effect is a natural consequence of partial chiral restoration in the nuclear medium. This suggestion is meaningful in the context of a local-density approximation, which has strong implications for the systematics of the Nolen-Schiffer anomaly over a range of nuclei. We show that such a mechanism predicts both noticeable shell effects and modest variations in the anomaly as the nuclear size is changed.

Absorption of negative pions on ${}_{}{}^1{}_{}{}^{}$${\mathit{S}}_0$ proton pairs is studied in a model which treats the two nucleon final-state interactions (including isobar components, which simulate pion p-wave scattering) in an exact way, but leaves the third nucleon an inactive spectator. Pion s-wave rescattering is included by a phenomenological Hamiltonian. Otherwise the initial-state pions are considered undistorted. The influence of different proton pair wave functions, final-state interactions, and pion-nucleon vertex forms is studied. The experimentally observed asymmetry of the cross section about 90° is obtained only if a Galilean-invariant pion absorption operator is used. The final-state interaction is particularly important in the tensor coupled ${}_{}{}^3{}_{}{}^{}$${\mathit{S}}_{1\mathrm{-}}^3$${\mathit{D}}_1$ states, with the final ${}_{}{}^3{}_{}{}^{}$${\mathit{D}}_1$ state emerging as the dominant one. The normal polarization of outcoming protons is similar to the analyzing power in the reaction p→+n→(pp${)}_{\mathit{S}\mathrm{wave}}$+${\mathrm{\pi }}^{\mathrm{-}}$ and is very insensitive on any details of the dynamical input. Also the polarization correlation coefficients show relatively little dependence on the model being rather constrained by kinematics.

Gamow-Teller (GT) strength distributions were studied in the (p,n) reaction at 136 MeV on the self-conjugate s-d shell nuclei ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$,${\mathrm{}}^{24}$Mg, and ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. The measurements were performed in two separate experiments with the beam-swinger neutron time-of-flight facility at the Indiana University Cyclotron Facility. The flight paths were 91 and 131 m, respectively, for the two experiments. The neutrons were detected in large-volume plastic-scintillation detectors. The overall time resolutions were about 825 ps; this provided energy resolutions from 300 to 400 keV. GT strength was identified as Δl=0 contributions in transitions to discrete final states and also in the background and continuum. The 0°, Δl=0 cross sections were converted to B(GT) units using a ‘‘universal’’ conversion formula calibrated to (p,n) reactions on other even-even s-d shell nuclei. The resulting B(GT) distributions were compared with full s-d shell-model predictions. The distribution for ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ is described well, but the distributions for ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ and ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ are described poorly. The total B(GT) strength observed in discrete states (up to 12 MeV of excitation) for each reaction is 65±10 % of that predicted. If one considers B(GT) strength observed in the continuum above a calculated quasi-free-scattering background, the strength increases to 70–100 % of that predicted. If one considers B(GT) strength in an analysis of the full continuum (up to ∼20 MeV), the entire amount predicted may be observed. These results are consistent with that observed in other light nuclei.

The nucleus ${}_{}{}^{144}{}_{}{}^{}\mathrm{Nd}$ is studied via the ${}_{}{}^{144}{}_{}{}^{}\mathrm{Nd}$(p,p’) reaction with 35 MeV protons. Angular distributions are measured for 13 states; 12 are assigned ${\mathit{J}}^{\mathrm{\pi }}$=$2^{+}$, $3^{\mathrm{-}}$, $4^{+}$, or $5^{\mathrm{-}}$. The present results are useful in understanding the nuclear shape transition taking place in the range N=82–90 and in the investigation of a proposed mixed symmetry mode in ${}_{}{}^{144}{}_{}{}^{}\mathrm{Nd}$.

Measurements of relative differential cross sections have been obtained for elastic scattering of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ nuclei from ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ at energies well below the Coulomb barrier. The measurements show deviations from Rutherford scattering, which are attributed to electric polarization of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ nuclei in the Coulomb field of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. The deduced value of the electric polarizability for ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is α=0.250±0.040 ${\mathrm{fm}}^3$. This result is significantly larger than expected from measurements of cross sections for ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ photodisintegration.

We investigated ${\pi }^0$ decay branching ratios $\frac{{\Gamma }_{{\pi }^0}}{\Gamma }$ in the weak decay of the ${}_{\Lambda }{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{\Lambda }{}^{11}{}_{}{}^{}\mathrm{B}$ hypernuclei using the (stopped $K^{-}$, ${\pi }^{-}$) reaction. The branching ratios were estimated to be 0.174±0.057(stat)±0.008(syst) and 0.140±0.039(stat)±0.025(syst) for the ${}_{\Lambda }{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{\Lambda }{}^{11}{}_{}{}^{}\mathrm{B}$ hypernuclei, respectively. The branching ratios are compared with theoretical calculations and related experimental values. Importance of distortion of pion wave function was found.

Based on a hybrid mapping, the vector coherent state theory is revisited. The hybrid mapping of a fermion state with N coherent (collective) fermion pairs and u unpaired (noncollective) fermions leads to a hybrid state with N bosons and u fermions. The hybrid mapping is exact by which the formidable problem of finding the matrix elements of a fermion operator for a (2N+u)-fermion system is reduced to that for a u-fermion system. The Pauli effects are totally taken into account by the overlap matrix (the K matrix) for the fermion states. The application to a fermion system with the Sp(6)⊃U(3) dynamical symmetry is discussed where it is vividly seen that the occurrence of the dynamical Pauli factors is related to the fermion pair⇆boson transformation. The intricate properties of the intrinsic operators and the K operator are discussed in detail.

The six-nucleon system is studied with a multiconfiguration resonating-group calculation which consists of the dominant configuration d+α, the cluster-rearrangement configurations p${+}^5$He and n${+}^5$Li, and the pseudo-inelastic configuration ${\mathit{d}}^{\mathrm{*}}$+α. The result shows that, because the deuteron cluster is easily distortable, a d+α single-configuration study is inadequate. With the addition of the other cluster configurations, the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ ground-state energy is improved by a large amount equal to 1.76 MeV. From an overall viewpoint, the p${+}^5$He and n${+}^5$Li configurations are found to contribute more significantly than the ${\mathit{d}}^{\mathrm{*}}$+α configuration, thus confirming the findings from previous seven- and eight-nucleon investigations that single-nucleon transfer processes generally make important contributions and sequential-decay processes are more important than direct-breakup processes in the relatively low-energy region. The d+α total reaction cross sections have also been computed and found to agree rather well with empirical results. At 10 MeV, for example, the calculated total reaction cross section is equal to 85% of the empirical value, which is the highest percentage obtained in our six- to eight-nucleon microscopic resonating-group calculations containing no phenomenological imaginary potentials.

The Spin Spectrometer was used to separate Dy ground-band and two-quasiparticle populations in one- and two-neutron transfer reactions with Sn and Ni projectiles. Transfer probabilities ${\mathit{P}}_{1\mathit{n},2\mathrm{}\mathit{n}}$ and two-neutron enhancement factors F==${\mathit{P}}_{2\mathit{n}}$/${\mathit{P}}_{1\mathit{n}}^2$ were determined as a function of scattering angle. For the two-quasiparticle bands F≃7–20, but for the ground band F≃30–500, indicating large pairing effects in two-particle transfer to the ground band. The data also indicate larger enhancement factors in Sn than in Ni collisions.

The high-energy continuum from inelastic scattering of 84 MeV/nucleon ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$ by ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ was studied by measuring ${}_{}{}^{17}{}_{}{}^{}\mathrm{ray}$ coincidences. The particle spectra in coincidence with γ rays above ∼1 MeV show structures up to 45-MeV excitation energy that can be explained in terms of the statistical decay of the highly excited target nucleus. The observation in the γ-ray spectrum of the giant dipole resonance built on excited states in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ confirms that the continuum up to ∼60-MeV excitation energy is dominated by the excitation of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ and offers the unique possibility of detailed studies of the giant dipole resonance as a function of excitation energy decoupled from the influence of angular momentum.

Using the ${\mathrm{U}}_{\mathit{v}}$(6/12)×${\mathrm{U}}_{\mathrm{\pi }}$(6/4) supersymmetry a prediction for the negative parity states in the odd-odd nucleus ${}_{}{}^{196}{}_{}{}^{}\mathrm{Au}$ is obtained. Since almost no experimental knowledge existed on the excited states of ${}_{}{}^{196}{}_{}{}^{}\mathrm{Au}$, the study of this nucleus is a stringent test for the predictive power of supersymmetry in nuclear structure. The theoretical values for the single-particle transfer reaction intensities from ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ to ${}_{}{}^{196}{}_{}{}^{}\mathrm{Au}$ are derived and compared with results of a high-resolution measurement of the ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$(d,t) and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$${(}^3$He,α) reactions.

The validity of the commonly assumed closure approximation has been tested by explicit calculations of the 0ν ββ-decay matrix elements of ${}_{}{}^{76}{}_{}{}^{}\to _{}^{76}{}_{}{}^{}$Se performed in the context of the quasiparticle random-phase approximation with a realistic model space. The closure approximation seems to work well for those matrix elements not very suppressed. Our results indicate that unlike the 2ν decay, the 0ν ββ-decay matrix elements are not greatly suppressed, but are comparable to those of shell model calculations. They are dominated by multipoles other than $0^{+}$ and $1^{+}$.