Extension of the Skyrme-Hartree-Fock approach to double-$\Lambda$ hypernuclei is presented. Several Skyrme-like $\Lambda \Lambda$ potentials are fitted to the binding energy of ${}_{\Lambda \Lambda }^{13}\mathrm{B}.$ So-called $\Lambda \Lambda$ bond energy $\Delta B_{\Lambda \Lambda }$ appears generally from a complicated interplay between the $\Lambda \Lambda$ potential, the nuclear core polarization, and $\Lambda$ spatial distributions. The core polarization gives a positive contribution to the bond energy even in the absence of $\Lambda \Lambda$ interaction. This contribution can be substantial even in heavy double-$\Lambda$ hypernuclei. The greatest uncertainties in extraction of the $\Lambda \Lambda$ potential from empirical data arise if hyperons contract the core, a $\Lambda \Lambda$ potential is of a short range, and the nuclear incompressibility is small.

We construct a consistent framework for treating single-particle properties in finite translationally invariant (self-bound) many-body systems. The differences with the standard case of fixed-center systems are discussed. For some properties which result from the Pauli principle in many-fermion systems, these differences are shown to persist even in the limit of a large number of particles.

The response of the nuclear energy to changes in neutron and proton surface diffusenesses is investigated using the Thomas-Fermi model. Algebraic expressions are provided for the energy cost of changing the two diffusenesses away from their equilibrium values. This will make it possible to generalize the macroscopic-microscopic calculations of nuclear masses and deformation energies by the inclusion of the neutron and proton diffusenesses as degrees of freedom (to be varied along with the shape degrees of freedom). One result, which is suggested by the relatively low cost in macroscopic energy of increasing the diffuseness of a heavy nucleus by 10% (about 4 MeV), is that superheavy nuclei near $Z=126,\hspace{0.5em}N=184\mathrm{}$ may have a fair chance of becoming stabilized by shell effects. An appendix introduces an improved measure of surface diffuseness, with certain advantages over the conventional Süssmann width b.

A systematic study is presented for three characteristics of the giant dipole resonance (GDR): (i) its width, (ii) its shape, and (iii) the integrated yield of emitted $\gamma$ rays in ${}^{120}\mathrm{Sn}$ and ${}^{208}\mathrm{Pb}$ as a function of temperature T. The double-time Green’s function method has been used to derive a complete set of equations, which allow one to calculate explicitly the GDR width due to coupling to all forward-going processes up to two-phonon ones at most in the second order of the interaction strength. The numerical calculations have been performed using the single-particle energies defined from the Woods-Saxon potentials. An overall agreement between theory and experiment is found for all three characteristics. The results show that the total width of the GDR due to coupling of the GDR phonon to all $ph,$ $pp,$ and $\mathrm{hh}$ configurations increases sharply at low temperatures up to $T\sim$ 3 MeV and saturates at $T\sim 4–6$ MeV. The quantal width ${\Gamma }_Q$ due to coupling to $\mathrm{ph}$ configurations decreases slowly with increasing T. It becomes almost independent of T only when the contribution of two-phonon processes at $T\ne 0$ is omitted. The observed saturation of the integrated yield above $E^{*}\sim 300$ MeV is reproduced in both the GDR region and the region above it.

It is shown that the isoscalar (isovector) strength in the energy region just above the low-energy threshold, which is created by exciting particles to the continuum in nuclei far from β-stability lines, can be reduced (increased) by the attractive (repulsive) coupling to isoscalar (isovector) shape oscillations. This is in contrast to the well-known fact that in β-stable nuclei low-lying isoscalar (isovector) particle-hole strengths are increased (reduced) by the attractive (repulsive) isoscalar (isovector) coupling. We also study the core-polarization effect on one-particle operators for bound particles, of which separation energies are appreciably smaller than those in β-stable nuclei.

We investigate a description of shape mixing and shape transitions using collective coordinates. To that end we apply a theory of adiabatic large-amplitude motion to a simplified nuclear shell model, where the approximate results can be contrasted with exact diagonalizations. We find excellent agreement for different regimes, and contrast the results with those from a more standard calculation using a quadrupole constraint. We show that the method employed in this work selects diabatic (crossing) potential energy curves where these are appropriate, and discuss the implications for a microscopic study of shape coexistence.

We study two kinds of Dirac sea effects on the ${}^1{S}_0$ pairing gap in nuclear matter based on the relativistic Hartree approximation to quantum hadrodynamics and the Gor’kov formalism. We show that the vacuum fluctuation effect on the nucleon effective mass is more important than the direct coupling between the Fermi sea and the Dirac sea due to the pairing interaction. The effects of the high-momentum cutoff are also discussed.

We have measured the production cross section of 1.8-s ${}^{261}\mathrm{Ha}$ from two different reactions. It was produced in the ${}^{250}\mathrm{Cf}{(}^{15}\mathrm{N},4n)$ reaction at 84 MeV and in the ${}^{243}\mathrm{Am}{(}^{22}\mathrm{Ne},4n)$ reaction at 116 MeV. Our rotating wheel system with a special parent-daughter stepping mode was used to detect α-α correlations between ${}^{261}\mathrm{Ha}$ and ${}^{257}\mathrm{Lr}.$ We measured 13 and 9 correlations in the two reactions, respectively. Assuming a 100% α branch, we have determined the production cross section of ${}^{261}\mathrm{Ha}$ to be $0.51\pm 0.20\mathrm{nb}$ in the ${}^{250}\mathrm{Cf}{(}^{15}\mathrm{N},4n)$ reaction at 84 MeV, and $0.25\pm 0.11\mathrm{nb}$ in the ${}^{243}\mathrm{Am}{(}^{22}\mathrm{Ne},4n)$ reaction at 116 MeV. Based on the number of fission events observed in the latter reaction, we have been able to set an upper limit of 18% for the spontaneous fission branch of ${}^{261}\mathrm{Ha}.$

The pion induced pion production reactions ${\pi }^{\pm }\overrightarrow{p}{\pi }^{+}{\pi }^{\pm }n$ were studied at projectile incident energies of 223, 243, 264, 284, and 305 MeV, using a cryogenic liquid hydrogen target. The Canadian High Acceptance Orbit Spectrometer was used to detect the two outgoing pions in coincidence. The experimental results are presented in the form of single differential cross sections. Total cross sections obtained by integrating the differential quantities are also reported. In addition, the invariant mass distributions from the $\left({\pi }^{+}{\pi }^{-}\right)$ channel were fitted to determine the parameters for an extended model based on that of Oset and Vicente-Vacas. We find the model parameters obtained from fitting the $\left({\pi }^{+}{\pi }^{-}\right)$ data do not describe the invariant mass distributions in the $\left({\pi }^{+}{\pi }^{+}\right)$ channel.

An analysis of new data for the reaction ${\pi }^{\pm }\overrightarrow{p}{\pi }^{\pm }{\pi }^{+}n$ at incident energies between 223 and 284 MeV is presented. ${\pi }^{+}{\pi }^{-}$ cross sections are obtained via Goebel-Chew-Low techniques by extrapolation to the pion pole using the pseudoperipheral approximation. A consistency check between the present experimental results and previous experiments at higher energies is made using Roy equations. The isospin 0, S-wave $\pi \pi$ scattering length was obtained using a variety of methods. The result obtained from a threshold expansion is $a_0^0=0.204\mathrm{}\pm 0.014$ (statistical) $\pm 0.008$ (systematic) in inverse pion mass units. It is shown that there are significant differences between the reaction mechanisms for the $\left({\pi }^{-}{\pi }^{+}\right)$ and $\left({\pi }^{+}{\pi }^{+}\right)$ channels.

This report details a greatly improved measurement of the four-neutron evaporation cross section following the fusion of ${}^6\mathrm{He}{+}^{209}\mathrm{Bi}$ for center-of-mass energies between 23.5 and 30.7 MeV. The results, for energies above the Coulomb barrier, are interpreted within the context of the standard statistical model.

Elastic scattering angular distributions for the symmetric ${}^{27}\mathrm{Al}{+}^{27}\mathrm{Al}$ system were measured at bombarding energies from 50 to 70 MeV. The integrated inelastic cross section for the first two excited states was determined by the in-beam $\gamma$-ray spectroscopy method. The data were analyzed by the optical model and by coupled channel calculations. The spin-orbit couplings of the ground states of both nuclei are analyzed.

Neutron fluences were measured from 435 MeV/nucleon Nb ions stopping in a Nb target and 272 MeV/nucleon Nb ions stopping in targets of Nb and Al for neutrons above 20 MeV and at laboratory angles between 3° and 80°. The resultant spectra were integrated over angles to produce neutron energy distributions and over energy to produce neutron angular distributions. The total neutron yields for each system were obtained by integrating over the angular distributions. The angular distributions from all three systems are peaked forward, and the energy distributions from all three systems show an appreciable yield of neutrons with velocities greater than the beam velocity. Comparison of the total neutron yields from the two $\mathrm{N}\mathrm{b}+\mathrm{N}\mathrm{b}$ systems suggests that the average neutron multiplicity decreases with decreasing projectile energy. Comparison of the total yields from the two 272 MeV/nucleon systems suggests that the total yields show the same dependence on projectile and target mass number as do total inclusive neutron cross sections. The data are compared with Boltzmann-Uehling-Uhlenbeck model calculations.

The reaction ${}^{16}\mathrm{O}({\gamma }^{*},{\pi }^{-}p)$ was studied with high energy resolution in the region of the Δ resonance at the AmPS facility of NIKHEF. Photoproduction cross sections were extracted for ${1p}_{1/2}$ and ${1p}_{3/2}$ neutrons in ${}^{16}\mathrm{O}$ and the resulting pion and proton angular distributions are compared to model calculations by Lee, Wright, and Bennhold. The proton angular distributions are well described by the nonlocal version of the model and allow one to extract rms radii and spectroscopic factors for the ${1p}_{1/2}$ and ${1p}_{3/2}$ neutron shells. The same calculations are in fair agreement with the pion angular distributions.

Results from a measurement of the reaction ${}^2\mathrm{H}({\pi }^{+},pp)\pi °$ at $T_{{\pi }^{+}}=239\mathrm{}\mathrm{MeV}$ are presented. Because two protons were detected, the measurement was sensitive to events which involved both nucleons in a substantial way. Differential distributions are compared to the predictions of simple models. An integrated cross section for SCX (single charge exchange), with the emission of two protons each with kinetic energy $>25\mathrm{}\mathrm{MeV},$ is presented.

The kinetic energy spectra and angular distributions of projectilelike fragments were measured by silicon based $\Delta E-E$ telescopes in 95 MeV ${}^{19}{\mathrm{F}+}^{93}\mathrm{Nb}.$ The spectra of oxygen and nitrogen fragments show the existence of two reaction mechanisms, namely, quasielastic transfer and incomplete fusion reactions. On the other hand, the carbon and other lower Z fragments show broad Gaussian spectra indicative of incomplete fusion reactions only. The quasielastic transfer is explained in terms of the direct surface transfer model. The cross sections of complete and incomplete fusion channels agree with the calculations based on the sum-rule model. Recoil range distributions of evaporation residues formed in the 95 MeV ${}^{19}{\mathrm{F}+}^{93}\mathrm{Nb}$ reaction were measured using recoil catcher and off-line gamma-ray spectrometry. The results corroborate the binary nature of the incomplete fusion reactions.

Analyzing powers for $\pi p$ elastic scattering were measured using the CHAOS spectrometer at energies spanning the Δ(1232) resonance. This work presents ${\pi }^{+}$ data at the pion kinetic energies 117, 130, 139, 155, 169, 180, 193, 218, 241, and 267 MeV and ${\pi }^{-}$ data at 87, 117, 193, and 241 MeV, covering an angular range of $50°<~{\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}<~180°$ at the higher energies and $90°<~{\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}<~180°$ at the lower energies. Unique features of the spectrometer acceptance were employed to reduce systematic errors. Single-energy phase shift analyses indicate the resulting $S_{11}$ and $S_{31}$ phases favor the results of the SM95 phase shift analysis over that of the older KH80 analysis.

The impact parameter dependence of the disappearance of nuclear flow is examined within the framework of the quantum molecular dynamics model. We confront the model with recent experimental findings of He et al. who measured the balance energy at different impact parameters for the reaction ${}^{64}\mathrm{Zn}{+}^{27}\mathrm{Al}.$ We simulate the heavy ion collisions with different nucleon-nucleon cross sections which includes the energy-dependent cross section, in-medium cross section (G matrix), and several constant and isotropic cross sections. Our calculations show that the balance energy in central collisions can be explained nicely with standard energy-dependent cross section whereas one needs a larger cross section to explain the balance energy at peripheral collisions.

Experimental elastic angular distributions for pions and kaons in the region of laboratory momentum from 600 to 900 MeV/c over the nuclear-Coulomb interference region are analyzed to extract both the real and imaginary part of the forward meson-nucleus scattering amplitude. For pions, results for the total cross sections extracted are smaller than those found from transmission experiments. The real part of the amplitude is found to have an interesting energy dependence. The significance of this result for the behavior of hadrons in nuclei is discussed. For kaons, only qualitative results were obtained due to limited data.

In this paper we discuss the reaction mechanisms that occur in the overlap zone for semiperipheral heavy ion collisions at intermediate energies. In particular we focus on the development of neck instabilities, which could determine a possible increase of dynamical fluctuations. As observed in recent experimental data, at beam energies just above 10 MeV/nucleon the most relevant expected consequence is the possibility to obtain large variances in the projectilelike and targetlike observables. With increasing beam energy we pass to a midrapidity fragment production. In this way we predict a smooth transition from a deep-inelastic to a fragmentation reaction mechanism.