Here we present the theoretical results for the Gamow-Teller two-neutrino double-beta decay (DBD) matrix elements for $0_1^{+}$→$0_1^{+}$ and $2_1^{+}$ transitions in the case of ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$ to ${}_{}{}^{76}{}_{}{}^{}\mathrm{Se}$ and ${}_{}{}^{82}{}_{}{}^{}\mathrm{Se}$ to ${}_{}{}^{82}{}_{}{}^{}\mathrm{Kr}$ nuclei. The calculations have been done in the framework of the variation after projection on the Hartree-Fock-Bogoliubov model with 2${\mathit{p}}_{1/2}$, 2${\mathit{p}}_{3/2}$, 1${\mathit{f}}_{5/2}$, and 1${\mathit{g}}_{9/2}$ valence space employing the modified Kuo-Brown interactions. The value of DBD half-lives result in excellent agreement for ground state (g.s.) to g.s. excitations of ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$ and ${}_{}{}^{82}{}_{}{}^{}\mathrm{Se}$ nuclei. Our results are in contrast with existing theoretical calculations for g.s. to $2^{+}$ excited state and are much closer to the experimental limits.

We perform calculations for different systems to study the mass dependence of flow disappearance in heavy-ion collisions in a relativistic Vlasov-Uehling-Uhlenbeck approach based on Walecka’s σ-ω model. We find that the mass dependence of the energy of vanishing flow is the result of a complex interplay among the momentum dependence of the nuclear mean field, Coulomb potential, and n-n collisions. The effect of the n-n collisions is predominant and the particular scaling value (${\mathit{A}}^{\mathrm{-}1/3}$) of the mass dependence can be related to the scaling behavior of the collision number per nucleon.

The decay properties of giant multipole resonances (GMR) are studied using the hybrid model in the context of channel type competition. We found that the analysis of GMR decay with several open channel types has the same analytical expression as when only one channel type is allowed. The generalization of the hybrid model presented provides a simple way to study the competition between the direct and statistical decay of GMR.

We present microscopic density functional theory calculations of the total dipole absorption cross sections of the even-A calcium isotopes from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ through ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$. The results reveal the onset of a collective dipole oscillation occurring at low energy and decoupled from the giant dipole resonance. The radial density fluctuations associated with this low-lying mode have the character of the pygmy dipole resonance predicted to exist in neutron rich nuclei.

We study quantitatively the effects of the ${\mathit{N}}^{\mathrm{*}}$(1440) resonance on the production of kaons, antikaons, and antiprotons in heavy-ion collisions at subthreshold energies. It is found that baryon-baryon collisions involving the ${\mathit{N}}^{\mathrm{*}}$ have minor effects on the production of kaons and antikaons. For the production of antiprotons—considerably different from the previous finding that baryon-baryon collisions involving the Δ(1232) dominate—we found that collisions involving the ${\mathit{N}}^{\mathrm{*}}$ are at least equally important as those involving the Δ. Medium effects such as the broadened resonance widths and decreased masses of nucleons and antinucleons are also discussed.

The size and energy distributions of spectators in ALADIN fragmentation experiments with gold projectiles are inferred from experimental data. For the most violent collisions of Au on Cu, the mean projectile spectator has the size of an iron nucleus, with an excitation energy of about 23 MeV/nucleon. We claim that a correct interpretation of these data should take into account the large range covered by the extracted distributions, which are in good agreement with the prediction of the Boltzmann-Uheling-Uhlenbeck calculations and with those of a new diabatic abrasion model.

Using a recent shape-independent approximation for the ${}_{}{}^3{}_{}{}^{}$${\mathit{S}}_1$${\mathrm{-}}^3$${\mathit{D}}_1$ mixing parameter, theoretical prevision for the low-energy mixing parameters is made. The present prevision is consistent with the deuteron binding energy, its asymptotic D-state to S-state ratio, ${\mathrm{\eta }}_{\mathit{d}}$, the triplet-scattering length, and the meson exchange tail of the tensor nucleon-nucleon potential. The theoretical prevision up to an incident laboratory energy of 25 MeV is consistent with the recent multi-energy determination of mixing parameters, but is much higher than many single-energy determinations of the same. The low single-energy values of the mixing parameter could be reproduced by meson-theoretical potentials only with a substantially reduced ${\mathrm{\eta }}_{\mathit{d}}$.

Cross sections for the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(e,e’p)R reaction have been measured for recoil momenta between 225 and 500 MeV/c. We find (1) that in the continuum channel a peak in the missing energy spectrum appears which shifts with increasing recoil momentum in a predictable way, and (2) that for the highest recoil momenta (above 300 or 350 MeV/c) overall agreement is obtained with microscopic calculations in which the scattering on nucleon pairs predominates. These results strongly suggest that the highest recoil momenta are generated by the scattering on one of a pair of nucleons. This interpretation is reinforced by an observed continuum momentum distribution which, for high recoil momenta, resembles the momentum distribution of deuterium. We infer that the high momentum part of the momentum distributioon of a nucleon pair appears unmodified when embedded in a nuclear medium.

Electron-capture delayed fission was positively identified for the first time in ${}_{}{}^{228}{}_{}{}^{}\mathrm{Np}$ produced via the ${}_{}{}^{233}{}_{}{}^{}\mathrm{U}$(50-MeV p,6n${)}^{228}$Np reaction. The half-life of the observed fission activity was measured to be 61.4±1.4 s. The ECDF mode was verified by an x-ray–fission coincidence experiment. Only about 25% of the expected x-ray–fission coincidences were detected which indicates that ${}_{}{}^{228}{}_{}{}^{}\mathrm{U}$ does not have a fission isomer populated by the electron-capture and that the overall lifetime of the high-energy states populated by the electron-capture is less than about ${10}^{\mathrm{-}17}$ s. The fission activity was assigned to ECDF of ${}_{}{}^{228}{}_{}{}^{}\mathrm{Np}$ based on chemical separation and observation of known progeny activities. The ratio of electron-capture to alpha decay is 1.5±0.4 for ${}_{}{}^{228}{}_{}{}^{}\mathrm{Np}$. The production cross section for ${}_{}{}^{228}{}_{}{}^{}\mathrm{Np}$ is 35±10 μb and the delayed fission probability is (2.0±0.9)×${10}^{\mathrm{-}4}$. The kinetic energies of coincident fission fragments were measured and a pre-neutron emission, most probable total kinetic energy, of 169±6 MeV was obtained. The mass-yield distribution was found to be predominantly asymmetric.

Several collective rotational bands have been established in doubly-odd ${}_{}{}^{114}{}_{}{}^{}\mathrm{Sb}$ extending to high spin (∼35ħ) and excitation energy (∼18 MeV). Two pairs of strongly coupled negative-parity sequences were observed at low spin consisting of stretched quadrupole transitions and interlinking M1 dipole transitions. These bands are intepreted in terms of the π[404]9/$2^{+}$ orbital. A third pair of signature-partner bands was established; however, no interlinking M1 transitions were observed in this case. These bands are associated with the π[550]1/$2^{\mathrm{-}}$ intruder orbital, and the rotational properties are remarkably similar to those of a π${\mathit{h}}_{11/2}$ ‘‘intruder’’ band in ${}_{}{}^{113}{}_{}{}^{}\mathrm{Sb}$ having enhanced quadrupole deformation (${\mathrm{\beta }}_2$∼0.32). The experimental results are discussed with the aid of total Routhian surface and Woods-Saxon cranking calculations.

Here we report the microscopic variational model calculations for the recently available experimental data on transition charge densities (TCD) of ${}_{}{}^{104,106,108,110}{}_{}{}^{}\mathrm{Pd}$ nuclei employing ‘‘quadrupole-quadrupole plus pairing interactions’’ operating in the 2${\mathit{p}}_{1/2}$, 1${\mathit{g}}_{9/2}$, 2${\mathit{d}}_{5/2}$, 3${\mathit{s}}_{1/2}$, 2${\mathit{d}}_{3/2}$, 1${\mathit{g}}_{7/2}$, and 1${\mathit{h}}_{11/2}$ valence spaces. Results for different p-n interaction strengths are also given. It is seen that TCD, being sensitive to the strength parameters, can act as one of the best means for the fixing of these parameters accurately. The results of TCD, for quadrupole excitations, using the p-n interaction strength parameter ${\mathrm{\chi }}_{\mathrm{\pi }\nu }$=-0.0231 MeV ${\mathrm{b}}^{\mathrm{-}4}$, are in excellent agreement. The calculated static properties from the Hartree-Fock-Bogoliubov (HFB) model, employed for TCD calculations, are also in good agreement. Deviation in the TCD results for hexadecupole transitions, points toward the need for some modifications so as to simulate the other interaction effects.

We reanalyze the decay mode of Λ hypernuclei induced by two nucleons modifying previous numerical results and the interpretation of the process. The repercussions of this channel in the ratio of neutron to proton induced Λ decay is studied in detail in connection with the present experimental data. This leads to ratios that are in greater contradiction with usual one pion exchange models than those deduced before.

Boson creation operators constructed from linear combinations of q-deformed zero-coupled nucleon pair operators acting on the nucleus (A,0) are used to derive pp random phase approximation equations. The solutions of these equations are the pairing vibrations in (A±2) nuclei. For the $0_1^{+}$ and $0_2^{+}$ states of the nucleus ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$, the variations of relative energies and transfer cross sections for populating these states via (t,p) reaction, with deformation parameter τ have been analyzed. For τ=0.405 the experimental excitation energy of 4.87 MeV and the ratio σ($0_2^{+}$)/σ($0_1^{+}$)=0.45 are well reproduced. The critical value of pairing interaction strength, for which phase transition takes place, is seen to be lower for deformed zero-coupled nucleon pair condensate with τ real, supporting our earlier conclusion that the real deformation simulates the two-body residual interaction. For τ purely imaginary a stronger pairing interaction is required to bring about the phase transition. The effect of imaginary deformation is akin to that of an antipairing type repulsive interaction. Using deformed zero-coupled quasiparticle pairs, a deformed version of quasiboson approximation for $0^{+}$ states in superconducting nuclei is developed. For the test model of 20 particles in two shells, the results of q-deformed boson and quasiboson approximations have been compared with exact results. It is found that the deformation effectively takes into account the anharmonicities and may be taken as a quantitative measure of the correlations not being accounted for in a certain approximate treatment.

Constrained Hartree-Fock-Bogoliubov calculations based on Gogny’s force have been performed to determine the potential energy surfaces, collective masses, and moments of inertia used to build a five-dimension collective Hamiltonian treating quadrupole motion in the ${}_{}{}^{184,186,188,190}{}_{}{}^{}\mathrm{Hg}$ isotopes. Many collective states have been predicted at low excitation energy, some of them forming γ-vibrational bands. To expand experimental information on γ bands, high statistics measurements on the ${\mathrm{\beta }}^{+}$ and electron capture decay of ${}_{}{}^{190}{}_{}{}^{}\mathrm{Tl}_{}^{\mathit{g},}{}_{}{}^{}$m and ${}_{}{}^{186}{}_{}{}^{}\mathrm{Tl}_{}^{\mathit{g},}{}_{}{}^{}$m have been performed at the ISOCELE facility. For the first time, γ bands have been identified in ${}_{}{}^{190}{}_{}{}^{}\mathrm{Hg}$ and ${}_{}{}^{186}{}_{}{}^{}\mathrm{Hg}$. These new results together with previous experimental information available on the ground state and K=0 excited bands in ${}_{}{}^{184,186,188,190}{}_{}{}^{}\mathrm{Hg}$ form a database which has been analyzed and discussed in the present theoretical framework. It is argued that the first K=0 excited band in ${}_{}{}^{190}{}_{}{}^{}\mathrm{Hg}$ is a β-vibrational band, and that ${}_{}{}^{186}{}_{}{}^{}\mathrm{Hg}$ is a nucleus in which shape coexistence occurs not only for the K=0 bands but also for the γ bands.

The charge symmetry-breaking potentials including the effects of pseudoscalar (π-η) and (π-η’), and vector (ρ-ω) meson in a series of mirror nuclei are examined. The computed Coulomb energy differences along with the present charge symmetry-breaking effects provide a reasonably accurate description of the binding energy differences between mirror nuclei.

Varied signature splitting phenomena in odd proton rare earth nuclei are investigated. Signature splitting as functions of K and j in the angular momentum projection theory is explicitly shown and compared with those of the particle rotor model. The observed deviations from these rules are due to the band mixings. The recently measured ${}_{}{}^{169}{}_{}{}^{}\mathrm{Ta}$ high spin data are taken as a typical example where fruitful information about signature effects can be extracted. Six bands, two of which have not yet been observed, were calculated and discussed in detail in this paper. The experimentally unknown band head energies are given.

The static magnetic quadrupole moment of a nucleus, induced by the T- and P-odd nucleon-nucleon interaction, is investigated in the single-particle approximation. Models are considered allowing for an analytical solution. The problem is also treated numerically in a Woods-Saxon potential with spin-orbit interaction. The stability of results is discussed.

We investigate the possibility that microscopic boson g factor estimates may require revision and consider the impact on $2_1^{+}$ g factors of the difference ${\mathrm{\epsilon }}_{\mathit{v}}$ between the neutron and proton d boson energies found typically in microscopic evaluations of interacting boson model parameters. We recalculate microscopic estimates for both d and g boson g factors, this time using the similarity-transformed Dyson boson mapping approach. Modulo more pronounced variation at the beginning and end of shells, our results confirm previous estimates by other methods. Differences between d and g boson factors are too small for the inclusion of g bosons to have a significant effect on $2_1^{+}$ g factor predictions. Instead, we present qualitative and semiquantitative arguments in support of the contention that microscopic estimates of ${\mathrm{\epsilon }}_{\mathit{v}}$ (taken in conjunction with our microscopic boson g factors) can, by and large, account for the systematics of $2_1^{+}$ g factors in the Z=50-to-82 and N=82-to-126 shells. Detailed calculations for ${}_{}{}^{148}{}_{}{}^{}\mathrm{Sm}$ and ${}_{}{}^{154}{}_{}{}^{}\mathrm{Sm}$ are consistent with this assertion provided the Majorana interaction strength ${\xi }_2$ is negligible. Our detailed calculations suggest substantial F-spin admixtures in the $2_1^{+}$ states of ${}_{}{}^{148}{}_{}{}^{}\mathrm{Sm}$ (at the 20% level or more) and the members of ground-state band of ${}_{}{}^{154}{}_{}{}^{}\mathrm{Sm}$ (9% or so), and point to the existence of a mixed-symmetric β bandhead in ${}_{}{}^{154}{}_{}{}^{}\mathrm{Sm}$ at below 2 MeV.

The large distance behavior of weakly bound three-body systems is investigated. The Schrödinger equation and the Faddeev equations are reformulated by an expansion in eigenfunctions of the angular part of a corresponding operator. The resulting coupled set of effective radial equations are then derived. Both two- and three-body asymptotic behavior are possible and their relative importance is studied for systems where subsystems may be bound. The system of two nucleons outside a core is studied numerically in detail and the character of possible halo structure is pointed out and investigated.

The effects of the environment modifications in the structure of the low-lying high-spin states of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ are studied by analyzing how the in-medium scaling law works on the excitation energies, wave functions, and electron scattering form factors corresponding to these states. It is shown that the consideration of ${\mathit{f}}_{\mathrm{\pi }}^{\mathrm{*}}$ in addition to the effective ρ-meson mass does not affect too much most of the states analyzed. However, some of them appear to be extremely sensitive to its inclusion in the residual nucleon-nucleon interaction. As a result, a value of ${\mathit{m}}_{\mathrm{\rho }}^{\mathrm{*}}$/${\mathit{m}}_{\mathrm{\rho }}$≊${\mathit{f}}_{\mathrm{\pi }}^{\mathrm{*}}$/${\mathit{f}}_{\mathrm{\pi }}$≊0.91 gives a good description of the (e,e’) form factors of these particular states without any quenching factor. This value is in agreement with the one found for ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ in a similar analysis performed in a previous work.