The interaction strengths of the ground band with the S band are extracted by using observed states of both bands as well as observed relative E2 transition rates for γ decay to yrast and nonyrast states. The signature dependence of the strength observed in the negative-parity yrast sequences of ${}_{}{}^{157}{}_{}{}^{}\mathrm{Ho}$ is explained, if a relatively strong n-p Q’’⋅Q’’ interaction is introduced in the conventional axially symmetric particle-rotor model. The Q’’⋅Q’’ interaction is supposed to take care of the possible shape-driving effect due to the presence of aligned quasiparticles.

Distortion effects in the (p,${\mathrm{\Delta }}^{++}$) reaction in nuclei are studied in the distorted-wave impulse approximation. The distorted waves for the continuum particles are described in the partial-wave expansion. Calculations are done for the total cross section and the differential cross sections with respect to the missing mass, four-momentum transfer, and the emission angle. The beam energy is varied from threshold to 3 GeV. For comparison the calculations are also done using the eikonal approximation for the distorted waves.

It has been proposed that a nucleus may be excited by first exciting the atom’s electrons with UV photons. The incident photons couple to the electrons, which would then couple via a virtual photon to the nucleus. As a test case, experiments with ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ have been performed. A pulsed infrared laser produces an atomic vapor of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ which is then bombarded by a high-brightness UV laser beam. The resulting ions are collected. The first excited nuclear state of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ has a 26-min half-life and decays by internal conversion, resulting in emission of an atomic electron. These conversion electrons are detected by a channel electron multiplier. An upper limit of 4.0×${10}^{\mathrm{-}5}$ has been obtained for the probability of exciting the nucleus of a ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ atom that is in the 248-nm UV beam for 700 fs at an irradiance in the range of 1.0×${10}^{15}$ to 2.5×${10}^{15}$ W/${\mathrm{cm}}^2$.

The ${\mathrm{\beta }}^{\mathrm{-}}$ decay of ${}_{}{}^{152}{}_{}{}^{}\to _{}^{152}{}_{}{}^{}$Nd has been investigated. Levels and transitions in ${}_{}{}^{152}{}_{}{}^{}\mathrm{Nd}$ were studied with γ-ray spectroscopy including γγ(θ) measurements. The level scheme of ${}_{}{}^{152}{}_{}{}^{}\mathrm{Nd}$ has been considerably revised and extended. Previously suggested ${\mathit{K}}^{\mathrm{\pi }}$=$0^{\mathrm{-}}$, $2^{\mathrm{-}}$, and $3^{\mathrm{-}}$ rotational bands have been confirmed, and new band members have been identified. Similarly, a positive-parity K=0 band has been confirmed, and extended to the $4^{+}$ level. The moments of inertia of the ground state band and the first excited ${\mathit{K}}^{\mathrm{\pi }}$=$0^{+}$ band were found to be strongly different, and at variance with the general systematics for both bands in the region. It is suggested that these unusual moments of inertia are due to a local, orbital dependent structure effect at proton number Z=60.

We perform 2νββ and 0νββ calculations for ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$, ${}_{}{}^{128}{}_{}{}^{}\mathrm{Te}$, and ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}$ using effective interactions derived from the Paris and Bonn-A potentials. Extended model spaces are employed in setting up the quasiparticle random phase approximation (QRPA) equations, on which our present calculations are based. For ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$ the model space consists of nine orbits, the two major shells from 0${\mathit{f}}_{7/2}$ to 2${\mathit{s}}_{1/2}$, and for the tellurium case we include eleven orbits spanning three major shells from 1${\mathit{p}}_{3/2}$ to 1${\mathit{f}}_{7/2}$. The bare-G-matrix elements are first calculated, with the Pauli exclusion operator carefully treated with a matrix inversion method, so that double counting between the calculated effective interaction and the above model spaces is strictly avoided. We then calculate the renormalized effective interaction, including corrections from core polarizations and folded diagrams. The effect of core polarization is found to be highly significant, especially for ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$. There appears to be a compensating effect from the folded diagrams; the net results with core polarizations and folded diagrams both included become rather close to the bare-G results. Unlike earlier QRPA calculations, our calculated ${\mathit{M}}_{\mathrm{GT}}$ matrix elements for 2νββ do not seem to exhibit strong dependence on ${\mathit{g}}_{\mathrm{pp}}$, the particle-particle interaction strength parameter, in the vicinity of ${\mathit{g}}_{\mathrm{pp}}$=1.0.

For 0νββ decays, our calculated values for ${\mathit{T}}_{1/2}^{0\nu }$〈${\mathit{m}}_{\nu }$${\mathrm{〉}}^2$ are typically 5×${10}^{23}$ yr ${\mathrm{eV}}^2$ for ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$, 2×${10}^{24}$ yr ${\mathrm{eV}}^2$ for ${}_{}{}^{128}{}_{}{}^{}\mathrm{Te}$, and 9×${10}^{22}$ yr ${\mathrm{eV}}^2$ for ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}$. Although the Bonn-A potential gives generally more pairing force, the final results for ββ decays given by the Paris and Bonn-A potentials are rather close to each other.

Angular distributions and the corresponding absolute α decay widths are calculated microscopically in odd axially deformed nuclei. It is found that the angular distributions are mainly determined by the deformation. The available experimental data are well reproduced.

Transition energies of 25 superdeformed (SD) bands in 13 nuclei of the A=194 region were fitted by the power-series expansion of I in odd powers of ${\mathit{E}}_{\gamma }$/2, ħ(I+1/2)=2αω+4/3β${\mathrm{\omega }}^3$, where ${\mathit{E}}_{\gamma }$/2=ħω, and by the expression for transition energy, ${\mathit{E}}_{\gamma }$=E(I+2)-E(I), where E(I)=AI(I+1) +B[I(I+1)${]}^2$+C[I(I+1)${]}^3$. Results are generally similar, and level spins for these SD bands are given based on expectations of rotational model behavior.

A q-deformed analogue of zero-coupled nucleon pair states is constructed and the possibility of accounting for pairing correlations examined. For the single orbit case, the deformed pairs are found to be more strongly bound than the pairs with zero deformation, when a real-valued q parameter is used. It is found that an appropriately scaled deformation parameter reproduces the empirical few nucleon binding energies for nucleons in the 1${\mathit{f}}_{7/2}$ orbit and 1${\mathit{g}}_{9/2}$ orbit. The deformed pair Hamiltonian apparently accounts for many-body correlations, the strength of higher-order force terms being determined by the deformation parameter q. An extension to the multishell case, with deformed zero-coupled pairs distributed over several single particle orbits, has been realized. An analysis of calculated and experimental ground state energies and the energy spectra of three lowermost $0^{+}$ states, for even-A Ca isotopes, reveals that the deformation simulates the effective residual interaction to a large extent.

Using a G-matrix folded diagram method and the Bonn nucleon-nucleon potential, the s-d shell effective interaction is derived and applied to evaluate the spectra of some light sd-shell nuclei. Due to the relatively weak tensor-force characteristic for the Bonn potential, the effective interaction matrix elements, particularly those with isospin T=0, come out generally more attractive than in earlier derivations in which local, strong tensor-force potentials were used. As a consequence of this, our results for the effective interaction and the spectra are in considerably better agreement with empirical determinations and experimental data. The sensitivity of the above nuclear structure calculations to the strength of the nuclear tensor force is demonstrated systematically and the dependence of the s-d shell matrix elements on the nuclear mass number is studied.

Shell-model interactions are constructed in the cross-shell model space connecting the 0p and 1s0d shells with due regard for the perturbative effects of the neighboring 0s and 0f1p shells. The interactions have three distinctive 0p-shell, cross-shell, and 1s0d-shell parts. The latter is taken to be the previously determined W interaction. The 0p-shell interaction is represented by two-body matrix elements and the cross-shell by either a potential or by two-body matrix elements. The interactions are determined by least-squares fits to 51 0p-shell and 165 cross-shell binding energies. It is found that the addition of monopole terms to a potential that is otherwise similar to that of the Millener-Kurath interaction results in a great improvement in the fit. In the fit to two-body matrix elements, 45 of 97 possible linear combinations of parameters are varied and the root-mean-square deviation for the 165 cross-shell energies is 330 keV. Examples of the application of the interactions are given for the prediction of neutron-rich binding energies, Gamow-Teller decays, and 0ħω, 1ħω, and 2ħω energy spectra.

The signals of the energy dependence of the giant dipole resonance width, obtained earlier in neutron radiative capture in the vicinity of the neutron binding energy and in heavy-ion reactions, have been verified against the available experimental data of nucleon radiative capture in the energy range from 5 to 25 MeV and masses A>100. The study is done within the preequilibrium exciton model. Analyses of low-energy behavior (below 15 MeV) of the radiative capture excitation functions support the use of giant dipole resonance form with the energy-dependent width of the generalized Lorentzian.

Photoexcitations of the short-lived isomers ${}_{}{}^{167}{}_{}{}^{}\mathrm{Er}_{}^{\mathit{m}}{}_{}{}^{}$, ${\mathit{T}}_{1/2}$=2.28 s, ${}_{}{}^{179}{}_{}{}^{}\mathrm{Hf}_{}^{\mathit{m}}{}_{}{}^{}$, ${\mathit{T}}_{1/2}$=18.68 s, ${}_{}{}^{191}{}_{}{}^{}\mathrm{Ir}_{}^{\mathit{m}}{}_{}{}^{}$, ${\mathit{T}}_{1/2}$=4.94 s, and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}_{}^{\mathit{m}}{}_{}{}^{}$, ${\mathit{T}}_{1/2}$=7.8 s, were produced with bremsstrahlung from the superconducting Darmstadt linear accelerator. Excitation functions were measured for the population of these isomers by (γ,γ’) reactions between 2 and 7 MeV. They indicated that the isomers were excited by resonant absorption through isolated intermediate states having integrated cross sections in excess of ${10}^{\mathrm{-}26}$ ${\mathrm{cm}}^2$ keV, i.e., values about 1000 times larger than most (γ,γ’) activation reactions reported previously although they were comparable to those reported earlier for the depopulating reaction ${}_{}{}^{180}{}_{}{}^{}\mathrm{Ta}_{}^{\mathit{m}}{}_{}{}^{}$(γ,γ’${)}^{180}$Ta. In all four nuclei a common onset was observed near 2.5 MeV for intermediate states with strengths much larger than those occurring at lower energies. The summed cross sections exhibit a clear correlation with the ground state deformations.

In order to study the properties of hot nuclei, neutrons emitted in the ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$+Ni, ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$, ${}_{}{}^{122}{}_{}{}^{}\mathrm{Sn}$ reactions at E/A=26 MeV were measured in coincidence with fusion residues. The neutron spectra obtained for different residue velocities were analyzed with the moving source model. The spectra are well reproduced with two sources; one corresponds to preequilibrium emission and the other to the decay of fusion nuclei. The extracted neutron multiplicity and initial temperature of the fusion nuclei indicate the formation of thermally equilibrated nuclei with excitation energy up to 5.0 MeV/nucleon. The extracted relation between the temperature and the excitation energy shows that the level densities of the hot nuclei are well described with the level density parameter a=A/(9±1) for excitation energies from 2.5 to 5.0 MeV/nucleon.

We have studied primary and secondary γ rays (46 in ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$, 107 in ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$, and 33 in ${}_{}{}^{31}{}_{}{}^{}\mathrm{Si}$) following thermal-neutron capture by the stable ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$, and ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$ isotopes. Almost all of these γ rays have been incorporated into corresponding level schemes consisting of 12 excited levels in ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$, 28 in ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$, and 9 in ${}_{}{}^{31}{}_{}{}^{}\mathrm{Si}$. In each case, the observed γ rays account for nearly 100% of all captures. The measured neutron separation energies for ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$, and ${}_{}{}^{31}{}_{}{}^{}\mathrm{Si}$ are 8473.56±0.04, 10609.24±0.05, and 6587.40±0.05 keV, respectively. The measured thermal-neutron capture cross sections for ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$, and ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$ are 169±4, 119±3, and 107±3 mb, respectively. In all three cases, primary electric-dipole (E1) transitions account for the bulk of the total capture cross section. We have calculated these E1 partial cross sections using direct-capture theory. The agreement between theory and experiment is satisfactory.

The analyzing power ${\mathit{T}}_{20}$ in the inclusive ${}_{}{}^1{}_{}{}^{}\mathrm{H}$${(}^6$Li,d or α or t)X reaction with 4.5 GeV tensor polarized ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ nuclei has been measured at an angle of 0.8°. The kinematics chosen favor the detection of spectator fragments; in the impulse approximation the laboratory momentum of such a fragment is then the Lorentz boosted internal momentum. Nonzero ${\mathit{T}}_{20}$ values have been observed, in agreement with the known nonsphericity of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ indicated by its quadrupole moment. The sign of ${\mathit{T}}_{20}$ in the d channel suggests that near q=0 the D state in ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ has the same sign as in the deuteron; an abrupt change of sign near q=0.12 GeV/c is in agreement with theoretical expectation of a node in the αd position wave function. The α-channel data show larger ${\mathit{T}}_{20}$ values than the d channel; in this case the small-q-region has not been explored enough to establish a similar node. A few data points in the t channel might suggest that ${\mathit{T}}_{20}$ becomes positive above q=0.4 GeV/c in this case.

Fusionlike processes were studied in the ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$${+}^{232}$Th reaction at 30 MeV per nucleon. Partition of the fusionlike cross section was determined by detecting nonequilibrium charged particles with an array of phoswich detectors (plastic wall) in coincidence with fission fragments for which the folding angle and thus the momentum transfer was measured. By measuring both single and multiple hits in the plastic wall and by correcting for its incomplete angular coverage a very extensive database of the fusionlike channels was obtained. The results were compared with model predictions comprising the BUU, Fermi jetting, the Boltzmann master equation model, and the nucleon-exchange transport model. It was found that these models which globally describe the dependence of the inclusive momentum transfer in fusionlike reactions cannot account for the associated particle production, in particular if the nucleons bound in the observed complex particles (d,t,α) are included in the comparison. Calculations of the energy spectra of the complex particles with the coalescence formalism indicate that a large fraction of the observed complex particles in the fusionlike reactions cannot be accounted for by pre-equilibrium emission from the fused composite system. They most probably originate from massive-transfer-type reactions that contribute to the beam-velocity component in the energy spectra.

The role of one-pion-exchange currents in intermediate-energy photonuclear reactions of the type A(γ,p)B is studied within a mean-field approach. Calculations are presented for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(γ,p) reaction leading to the low-lying states of ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ including states with a predominant hole character and states with a more complicated two-hole–one-particle (2h-1p) structure. The level of agreement with the data for decay to the 2h-1p states suggests the important role of meson exchange currents in (γ,p) reactions at intermediate energies.

We have studied the β-delayed proton decay of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Mg}$ to search for the 2645 keV state in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$. This state is of astrophysical interest, because any proton capture through this state would dominate the stellar reaction rate of the reaction ${}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}$(p,γ${)}^{20}$Na. This reaction determines the break out from the hot CNO cycle. Several proton groups have been observed and their logft values have been determined. No protons from the 2645 keV state were seen and a lower limit of logft≥5.85 has been established. The impact of this result on the ${}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}$(p,γ) rate is discussed.

Total cross sections and angular distributions for the differential cross section and analyzing power of the reaction ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(p→,${\mathrm{\pi }}^0$${)}^3$He have been measured at four energies very near threshold (0.1<${\mathit{T}}_{\mathrm{\pi }}^{\mathrm{c}.\mathrm{m}.\mathrm{}}$<2.7 MeV). The large asymmetries observed in the angular distributions of the differential cross section indicate strong constructive interference between the amplitudes for s-wave pion emission and the amplitudes for p-wave emission. A measure of the s-wave strength at zero energy is obtained and found to be consistent with the results from pionic atoms. The new data indicate that the excitation function for this reaction differs significantly from that of p+n→d+${\mathrm{\pi }}^0$.

We report the results of a precise test of charge symmetry in the scattering of polarized neutrons from polarized protons at a laboratory bombarding energy of 183 MeV. The observable sensitive to charge symmetry is the difference between the analyzing powers associated with the neutron spin [${\mathit{A}}_{\mathit{n}}$(θ)] and with the proton spin [${\mathit{A}}_{\mathit{p}}$(θ)]. Systematic errors and experimental ambiguities in the measurement of this difference are extensively discussed. Our result for ΔA≡${\mathit{A}}_{\mathit{n}}$-${\mathit{A}}_{\mathit{p}}$, averaged over the angular range 82.2°≤${\mathrm{\theta }}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$≤116.1°, is (33.1±5.9±4.3)×${10}^{\mathrm{-}4}$. With the statistical and systematic errors added in quadrature, this value is 3.4 standard deviations larger than the effect expected from pure photon exchange (the electromagnetic spin-orbit interaction) between the neutron and proton, and thus represents clear evidence of charge symmetry breaking in the strong interaction. We also extract information about the angular dependence of ΔA(θ), within limitations imposed by uncertainties in the measured beam and target polarizations. Both the angle-averaged value and the angular dependence measured for ΔA are in excellent agreement with predictions from meson-exchange theory, when these include both the effect of the n-p mass difference on one-pion exchange and the isospin mixing of ${\mathrm{\rho }}^0$ and ${\mathrm{\omega }}^0$ mesons. In particular, the Bonn nucleon-nucleon (NN) potential model accounts for the present results utilizing ρNN and ωNN coupling constant values deduced previously for this potential from fits to more conventional NN scattering data.