Dipole transitions to bound states in the Sn nuclei ${}^{116}\mathrm{Sn}$ and ${}^{124}\mathrm{Sn}$ have been investigated by means of nuclear resonance fluorescence (NRF) using 12 MeV linearly polarized bremsstrahlung and unpolarized bremsstrahlung with different end point energies (4.1, 7.5, and 10 MeV). The measurements enable the determination in a completely model-independent way of reduced transition probabilities, multipolarities, and parities of the observed transitions. More than 150 new dipole ground state transitions have been identified. The observed dipole strength distribution displays for both isotopes a clear concentration around 6.5 MeV. For about half of the observed dipole excitations parities could be extracted. They all turned out to be $E1\mathrm{}$ excitations except for three tentative $M1\mathrm{}$ assignments. The NRF results are compared with data from tagged photon scattering experiments and quasiparticle phonon model calculations.

Several $\gamma$ transitions in ${}^{105-109}\mathrm{Tc}$ nuclei were identified for the first time from spontaneous fission studies with a ${}^{252}\mathrm{Cf}$ source and the Gammasphere. New level schemes are proposed and related to the underlying nuclear structure. Positive parity bands with a large signature splitting observed in ${}^{105,107,109}\mathrm{Tc}$ are evidently derived from $g_{9/2}$ orbitals and are similar to analogous bands in ${}^{103}\mathrm{Rh},$${}^{103}\mathrm{Ag},$ and ${}^{99}\mathrm{Y}.$ New $\gamma$ transitions have also been identified in ${}^{139-143}\mathrm{Cs}$ and used to construct level schemes for these isotopes. Correlated-pair fission yields extracted from the data show an appreciable field for the zero neutron ${}^{109}\mathrm{Tc}{/}^{143}\mathrm{Cs}$ pair.

The odd-odd $N=Z$ nuclide, ${}^{78}\mathrm{Y}$ has been produced in the ${}^{40}\mathrm{Ca}{(}^{40}\mathrm{Ca},pn)$ 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 β detectors and two Ge γ-ray detectors where β-γ coincidences were recorded as a function of time. γ rays with energies of 279 (100%), 504 (90%), and 713 (40%) keV, previously identified as yrast transitions in daughter ${}^{78}\mathrm{Sr},$ were observed and found to decay with a half-life of 5.8 (6) s. From the relative intensities of the γ-rays, a spin and parity of $5^{+}$ and $T=0\mathrm{}$ are assigned to the parent state in ${}^{78}\mathrm{Y}$ undergoing β decay. A production cross section of $4\pm 1\mu \mathrm{b}$ has been determined for ${}^{78}\mathrm{Y}$ 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 $T=1\mathrm{}$ $0^{+}$ ground state. From this limit, it can be inferred that $T=1\mathrm{}$ $\mathrm{pn}$ pairing is considerably quenched relative to such pairing in adjacent odd-odd $N=Z$ ${}^{74}\mathrm{Rb}.$ Two-quasiparticle rotor model calculations have been used to account for the structure of ${}^{78}\mathrm{Y}$ and adjacent nuclides.

Excited levels in ${}^{144}$Nd below 3.3 MeV have been studied using the ${(n,n}^{\prime }\gamma )$ reaction. Electromagnetic transition probabilities, multipole-mixing and branching ratios, and level spins and parities were deduced from measured $\gamma$-ray excitation functions, angular distributions, and Doppler shifts. Mixed-symmetry configurations in low-lying excited states were investigated by comparing experimental electromagnetic transition rates with theoretical calculations made using the interacting boson model and with existing calculations from the quasiparticle phonon model, the cluster vibrator model, and the particle-core coupling model. Fragmentation of the $2^{+}$ mixed-symmetry mode is clearly observed through strong $M1\mathrm{}$ transitions into the lowest symmetric $2^{+}$ level and through small $E2/M1\mathrm{}$ multipole-mixing ratios. Comparisons with similar measurements on ${}^{142}\mathrm{Ce}$ reveal that these $N=84\mathrm{}$ isotones exhibit strong fragmentation of the mixed-symmetry mode, although it appears to be spread into more levels in ${}^{144}\mathrm{Nd}$. Evidence is found to support the assignment of the 2779.0-keV level as the $3^{-}$ member of the octupole-quadrupole phonon coupled quintuplet in ${}^{144}\mathrm{Nd}$ and to propose that this excited mode is shared with the 2606.0-keV state. Two- and three-quadrupole phonon excitations, as well as other members of the quadrupole-octupole quintuplet, are also examined.

The density matrix expansion is used to obtain a local energy density functional for interactions with a realistic meson exchange structure. Hartree-Fock (HF) equations are derived and applications to infinite matter and finite nuclei are discussed. Using a generalized Slater approximation for the density matrix the HF equations still incorporate the momentum structure of the underlying finite range interaction. For applications a density dependent effective interaction is determined from a $G$ matrix where the density dependence is adjusted to the saturation properties of symmetric nuclear matter. Intending applications to systems far off stability special attention is paid to the low density regime and asymmetric nuclear matter. Results are compared to Skyrme HF calculations. The ground state properties of stable nuclei are well reproduced. The potential of the approach is further exemplified in calculations for $A=100\mathrm{}-140$ tin isotopes. Extended neutron skins are found beyond ${}^{130}\mathrm{Sn}$ corresponding to solid layers of neutron matter surrounding a core of normal composition.

Relativistic Hartree-Bogoliubov (RHB) theory is applied in the description of the ground-state properties of Ni and Sn isotopes. The NL3 parameter set is used for the effective mean-field Lagrangian, and pairing correlations are described by the pairing part of the finite range Gogny interaction D1S. Fully self-consistent RHB solutions are calculated for the Ni $(28\mathrm{}<~N<~50)$ and Sn $(50\mathrm{}<~N<~82)$ isotopes. Binding energies, neutron separation energies, and proton and neutron rms radii are compared with experimental data. The model predicts a reduction of the spin-orbit potential with the increase of the number of neutrons. The resulting energy splittings between spin-orbit partners are discussed, as well as pairing properties calculated with the finite range effective interaction in the $\mathrm{pp}$ channel.

Analytical expressions for $E1\mathrm{}$, $E2\mathrm{}$, $E3\mathrm{}$, $M1\mathrm{}$, and $M2\mathrm{}$ transition rates for low-lying negative-parity states in the SU(3) limit of the $\mathrm{spdf}$ IBM are given. Applications to some deformed nuclei in the $A=150\mathrm{}$ region and Uranium isotopes have yielded good agreement between calculation and data for $E1\mathrm{}$ transitions. These formulas are useful in studying both positive- and negative-parity states of deformed nuclei.

The spectroscopic factors for the low-lying quasihole states observed in the ${}^{16}\mathrm{O}{(e,e}^{\prime }{p)}^{15}\mathrm{N}$ reaction are reinvestigated with a variational Monte Carlo calculation for the structure of the initial and final nucleus. A computational error in a previous report is rectified. It is shown that a proper treatment of center-of-mass motion does not lead to a reduction of the spectroscopic factor for $p$-shell quasihole states, but rather to a 7% enhancement. This is in agreement with analytical results obtained in the harmonic oscillator model. The center-of-mass effect worsens the discrepancy between present theoretical models and the experimentally observed single-particle strength. We discuss the present status of this problem, including some other mechanisms that may be relevant in this respect.

Allowed ${\beta }^{+}$ branches of very proton-rich $\mathrm{fp}$ shell $T_z=-2$ nuclei at the proton drip line are calculated in the full $\mathrm{fp}$ valence space. The ${\beta }^{+}$ decay half-lives calculated with the standard quenching factor ${(g}_A^{\mathrm{eff}}{/g}_A)$=0.74 are in good agreement with existing experimental data. Detailed branching Gamow-Teller strength are predicted but comparison with experiment is still difficult since, in most cases, spectroscopic information is not yet available.

We study the binary cold fission of ${}^{252}$Cf in the frame of a cluster model where the fragments are born to their respective ground states and interact via a double-folded potential with deformation effects taken into account up to multipolarity $\lambda =4\mathrm{}$. The preformation factors were neglected. In the case when the fragments are assumed to be spherical or with ground-state quadrupole deformation, the $Q$-value principle dictates the occurrence of a narrow region around the double magic ${}^{132}$Sn, like in the case of cluster radioactivity. When the hexadecupole deformation is turned on, an entire mass region of cold fission in the range 138–156 for the heavy fragment arise, in agreement with the experimental observations. This fact suggests that in the above-mentioned mass region, contrary to the usual cluster radioactivity where the daughter nucleus is always a neutron/proton (or both) closed shell or nearly closed shell spherical nucleus, the clusterization mechanism seems to be strongly influenced by the hexadecupole deformations rather than the $Q$ value.

Led by the observation that particle-hole excitations play an important role in nuclei throughout the whole nuclear mass table, we have formulated a general framework such that particle-hole excitations can be incorporated in a systematic way in the interacting boson model. The particle-hole degree of freedom is introduced in the interacting boson models IBM-2 and IBM-3. Corresponding algebraic structures and reduction schemes are studied. The coexistence of intruder spin, $F$ spin, and isospin as good quantum numbers is investigated. The mixing of particle-hole excitations with ground state configurations is determined and compared with a commonly used IBM-1 treatment.

Collective vibrations in a finite Fermi system are studied within a phase space approach which is based on the Landau-Vlasov kinetic equation. The linear response theory is used and the semiclassical internal and collective response functions are evaluated with a continuous single-particle angular momentum $l.\mathrm{}$ We focus on the strength function and fragmentation width of the vibrations. We determine the contributions to the collective strength function which are associated with different values of relevant single-particle angular momentum. Applications to the nuclear isoscalar vibrations with multipolarities $L=0,$ 2, and 3 are presented.

The presence of not yet detected intruder states in ${}^8\mathrm{Be},$ e.g., a ${J=2\mathrm{}}^{+}$ intruder at 9 MeV excitation would affect the shape of the ${\beta }^{\mp }$-delayed $\alpha$ spectra of ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}.\mathrm{}$ In order to test the plausibility of this assumption, shell-model calculations with up to $4ħ\omega$ excitations in ${}^8\mathrm{Be}$ (and up to $2ħ\omega$ excitations in ${}^{10}\mathrm{Be}$) were performed. With the above restrictions on the model spaces, the calculations did not yield any low-lying intruder state in ${}^8\mathrm{Be}.$ Another approach—the simple deformed oscillator model with self-consistent frequencies and volume conservation—gives an intruder state in ${}^8\mathrm{Be}$ which is lower in energy than the above shell-model results, but its energy is still considerably higher than 9 MeV.

The excitation functions for different fragments produced in the ${}^{19}\mathrm{F}{+}^{27}\mathrm{Al}$ reaction have been measured in the incident energy range 113.5–130.0 MeV in steps of 250 keV. The detection of the outgoing fragments in a large solid angle allowed a study of the excitation functions for different [total kinetic energy loss (TKEL), ${\vartheta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}$] windows. Large fluctuations have been observed in all the excitation functions analyzed in this work. The $Z$ and angular cross correlation analysis does not support a compound nucleus origin of these fluctuations. The coherence widths extracted from the energy autocorrelation function (EAF) and by the peak counting method do not show, within errors, ${\vartheta }_{\mathrm{c}.\mathrm{m}.\mathrm{}},$ $Z$, or TKEL dependence. The lifetime of the dinuclear system (DNS) ${}^{19}\mathrm{F}{+}^{27}\mathrm{Al}$ is found to be equal with the DNS’s rotation period. This could explain the secondary structures evidenced in the EAF. A reaction mechanism involving the excitation of the DNS in intermediate states of molecular nature is supported by this experimental evidence.

The phenomenon of cold (neutronless) alpha ternary fission in spontaneous fission of ${}^{252}$Cf was experimentally observed by triple gamma coincidence technique with Gammasphere with 72 gamma-ray detectors. Correlated pairs of ${}_{36}$Kr-${}_{60}$Nd, ${}_{38}$Sr-${}_{58}$Ce, ${}_{40}$Zr-${}_{56}$Ba, ${}_{42}$Mo-${}_{54}$Xe, ${}_{44}$Ru-${}_{52}$Te, and ${}_{46}$Pd-${}_{50}$Sn were observed to be associated with $\alpha$ ternary fission of ${}^{252}$Cf. Yields of cold $\alpha$ ternary fission were extracted.

The formation and decay of hot nuclei generated in the interaction of light projectiles (475 MeV and 2 GeV protons and 2 GeV ${}^3$He) on a series of targets ${(}^{107}\mathrm{A}\mathrm{g},$ ${}^{197}\mathrm{A}\mathrm{u},$ ${}^{209}\mathrm{B}\mathrm{i},$ and ${}^{238}\mathrm{U})$ are studied with an apparatus combining the efficient detection of neutrons in 4$\pi$ sr and an accurate characterization of light charged particles, intermediate-mass fragments (IMF’s), and fission fragments. A two-step approach with an intranuclear cascade process for modeling the initial off-equilibrium phase of the collision followed by a classical step-by-step evaporation—including fission competition—is used to reproduce the data. It is inferred from the model, which is found to reproduce several data sensitive to heat, that nuclei with temperatures exceeding $T=5\mathrm{}$ MeV are produced for a sizable part of the events, thus giving the opportunity to study the behavior of hot nuclei free from strong collective excitations which generally accompany nucleus-nucleus collisions. Most of the observed features related to particle emission or more specifically to particle evaporation are rather well accounted for by the model calculation. The evaporationlike IMF emission is generally rather weak, and does not show any rapid onset at the highest excitation energies as would have been expected in a genuine thermal multifragmentation process. Binary fission of the U-like target is shown to be a fairly probable channel at most excitation energies. Some of the characteristics of the fission channel are satisfactorily reproduced, but not all.

Cross sections for multineutron transfer reactions in ${}^{58}\mathrm{Ni}{+}^{124}\mathrm{Sn}$ collisions have been measured with good particle identification at four energies around the Coulomb barrier. The angle- and energy-integrated multineutron transfer cross sections exhibit an exponential falloff with increasing number of transferred neutrons. The elastic scattering and one-nucleon transfer reaction data can be reproduced well by coupled-channels calculations and distorted-wave Born approximation calculations, respectively, using the same optical potential. The transfer probabilities for each transfer channel, plotted as a function of the distance of closest approach, fall on a common exponential curve; the slopes of these exponential falloff curves are discussed.

Measurements of multineutron transfer reactions in ${}^{58}\mathrm{Ni}{+}^{124}\mathrm{Sn}$ collisions are analyzed in a simplified coupled-channels model. Successive one-neutron and direct two-neutron transfer couplings are included explicitly, together with $2^{+}$ and $3^{-}$ excitations of projectile and target. Capture reactions, i.e., fusion and deep-inelastic reactions, are described by ingoing-wave boundary conditions. Quasielastic charged-particle transfer reactions are not treated explicitly but are simulated by a weak imaginary potential. The model provides a comprehensive description of the measured reaction and elastic scattering data, from far below to well above the Coulomb barrier. We find that subbarrier capture rates are enhanced by couplings to neutron transfer channels but the enhancement is not as large as caused by couplings to low-lying surface modes.

Differential cross sections for ${\pi }^{+}{+}^{12}\mathrm{C}$ elastic scattering in the energy range of 18–44 MeV for six scattering angles have been measured with an increment in the incident energy of 2 MeV. The measured cross sections are compared to calculations within the framework of a unitary scattering theory of the pion-nucleus interaction. It is shown that the excitation function at angles around $90°$ is dominated by the $D$ wave of the pion-nucleus interaction.

The prompt γ radiation from the interaction of fast neutrons with aluminum was measured using the white neutron beam of the WNR facility at the Los Alamos National Laboratory. Aluminum samples were positioned at about 20 m or 41 m distance from the neutron production target. The spectra of the emitted γ rays were measured with a high-resolution HPGe detector. The incident neutron energy was determined by the time-of-flight method and the neutron fluence was measured with a ${}^{238}\mathrm{U}$ fission chamber. From the γ-ray spectra excitation functions for prominent γ-ray transitions in various residual nuclei (in the element range from F to Al) were derived for neutron energies from 3 to 400 MeV. Up to 200 MeV incident neutron energy the results are compared with the predictions of nuclear model calculations performed with the code GNASH. This code combines compound nucleus calculations using Hauser-Feshbach statistical theory with preequilibrium calculations from an exciton model including multiple preequilibrium processes. For the majority of the γ-ray transitions there is reasonable agreement between the measured and the calculated cross sections.