The pseudo SU(3) model, in an extended version in which proton and neutron degrees of freedom are incorporated explicitly, is used to study the nature of low-lying magnetic dipole excitations in even-even rare-earth nuclei. Through a linear mapping between invariants of the rotor group and SU(3), a microscopic interpretation of the “scissors” mode of the two-rotor model is realized. The model allows for, first, a classification of SU(3) shell-model configurations in terms of collective degrees of freedom and, second, an adjustment of the relative energy of distinct $1^{+}$ states. Triaxiality of the parent proton and neutron distributions is shown to add a “twist” degree of freedom to the usual “scissors” mode picture. This new mode should be observed as: (1) a low-lying $K=0\mathrm{}$ excitation, and (2) a second, doubly degenerate, $K=1\mathrm{}$ transition only slightly higher in energy than the usual scissors mode. Fragmentation of the $M1\mathrm{}$ strength distribution can be reproduced within framework of the model by including representation mixing terms in the Hamiltonian.

Recent and planned experiments aiming at the observation of the direct links between superdeformed and normal-deformed structures in the $A\sim 190$ mass region may offer unique information on the absolute nuclear binding energy in the 2:1 minima, and hence on the magnitude of shell effects in the superdeformed well. In the present paper, the self-consistent mean-field theory with density-dependent pairing interaction is used to explain at the same time the two-particle separation energies in the first and second wells, and the excitation energies of superdeformed states in the $A\sim 190$ and $A\sim 240$ mass regions.

An iterative relationship connecting a series of two-parameter formulas for rotational spectra is revealed. It is also pointed out that various two-parameter formulas are merely solutions of a universal equation with different powers.

A cranking Hartree-Fock-BCS HFB model with $T=0\mathrm{}$ and $T=1\mathrm{}$ proton-neutron correlations is proposed and discussed. Numerical calculations are carried out on a single ${(g}_{9/2}{)}_p{(g}_{9/2}{)}_n$ shell as a first practical try. It is found that the $T=0\mathrm{}$ proton-neutron pairing correlation is crucial for a crossing of an even-spin ground band by an odd-spin band, a so-called $T=1\mathrm{}$ and $T=0\mathrm{}$ band crossing in an $N=Z$ odd-odd system. A conventional spin alignment of a ground state band in an even-even system is also examined. A delay of this spin alignment due to a $T=1,J=0\mathrm{}$ proton-neutron pairing correlation is found for nuclei with $N=Z$.

The renormalized proton-neutron quasiparticle random phase approximation approach has been used to study double β decay matrix elements and associated transition half-lives for neutrino-accompanied double β decay to the first excited $2^{+}$ state for five medium-heavy parent nuclei ${}^{76}$Ge, ${}^{82}$Se, ${}^{96}$Zr, ${}^{100}$Mo, and ${}^{116}$Cd. The results of these calculations are compared with the normal approach and experiments where available. The dependence on the size of the single particle basis is also discussed.

The binding energy of polarized nuclear matter with excess of neutrons, spin-up neutrons, and spin-up protons contains three symmetry energies: the spin symmetry energy, the isospin symmetry energy, and the spin-isospin symmetry energy. The potential used here for polarized nuclear matter is a modified density-dependent Seyler-Blanchard potential with an explicit dependence on the density of protons with spin-up and -down ${\rho }_{p\uparrow }$ and ${\rho }_{p\downarrow },$ also on the neutron density with spin-up and -down ${\rho }_{n\uparrow }$ and ${\rho }_{n\downarrow }.$ It is found that the binding energy per particle, pressure, velocity of sound, and entropy agree very well with previous theoretical estimates.

Elastic scattering of polarized protons from ${}^{58}\mathrm{Ni}$ has been measured at incident proton energies of 192, 295, and 400 MeV. Optical model calculations employing relativistic impulse approximations and a microscopic folding model using a nonrelativistic $G$ matrix are compared with the experimental results. In order to explain the experiment further, it is necessary to use a density distribution deduced from the charge distribution measured by electron scattering and to modify the nucleon-nucleon interaction in the nuclear medium by altering coupling constants between nucleons and mesons and also adjusting the masses of exchanged mesons.

Exclusive measurements of the analyzing power and two spin-transfer observables for nucleon knockout from an ${}^{16}\mathrm{O}$ target are presented, at kinematic conditions chosen to emphasize interactions in the nuclear interior. The analyzing power data are substantially reduced in comparison with values calculated in the distorted wave impulse approximation (DWIA) using the free nucleon-nucleon interaction, particularly for knockout of the deeply bound ${1s}_{1/2}$ nucleons. Inclusion of density dependence for the interaction in the calculations improves the agreement with the data, but does not provide a satisfactory description for nucleon knockout from ${}^{16}\mathrm{O}.$ Spin-orbit distortions are shown to strongly affect the DWIA predictions of the ${1s}_{1/2}$ analyzing powers over most of the experimental kinematic range, but notably not near the points of negligible recoil momentum. Hence these data offer constraints on the optical potentials and independently on the two-body effective interaction.

The ${}^{41}\mathrm{Ca}{\mathrm{}(n,p)\mathrm{}}^{41}\mathrm{K}$ and ${}^{41}\mathrm{Ca}(n,\alpha {)}^{38}\mathrm{Ar}$ reaction cross sections were determined with thermal neutrons at the high flux reactor of the ILL in Grenoble. For the ${}^{41}\mathrm{Ca}{(n}_{\mathrm{th}}{,p)}^{41}\mathrm{K}$ reaction cross section, a value of $(7\mathrm{}\pm 2)\hspace{0.5em}\mathrm{mb}$ was obtained. In the case of the ${}^{41}\mathrm{Ca}{(n}_{\mathrm{th}},\alpha {)}^{38}\mathrm{Ar}$ reaction, the transition to the ground state in ${}^{38}\mathrm{Ar}$ has a cross section $\sigma {(n}_{\mathrm{th}},{\alpha }_0)\hspace{0.5em}=\hspace{0.5em}(42\mathrm{}\pm 6)\hspace{0.5em}\mathrm{mb}$, the most prominent decay going to the first excited state in ${}^{38}\mathrm{Ar}$ with a cross section $\sigma {(n}_{\mathrm{th}},{\alpha }_1)\hspace{0.5em}=\hspace{0.5em}(130\mathrm{}\pm 25)\hspace{0.5em}\mathrm{mb}$. This can be explained by the presence of a nearby bound level with $J^{\pi }{=4\mathrm{}}^{-}$. Also ${}^{41}\mathrm{Ca}{(n}_{\mathrm{th}},\gamma \alpha {)}^{38}\mathrm{Ar}$ transitions have been observed with a cross section of $(10\mathrm{}\pm 2)\hspace{0.5em}\mathrm{mb}$. The primary $\gamma$ transitions are shown to have a $M1\mathrm{}$ multipolarity.

Events with 3–5 intermediate mass fragments [(IMF’s), $Z>\mathrm{}2\mathrm{}]$ have been studied for peripheral and more central collisions in the ${}^{40}\mathrm{Ca}{+}^{40}\mathrm{Ca}$ reaction at $E_{\mathrm{lab}}=35\mathrm{}$ MeV/nucleon. For a significant portion of events, in coincidence with projectilelike and with targetlike fragments, we observe IMF’s, with velocities close to zero in the center-of-mass reference frame. Properties of this “intermediate velocity” source suggest a stochastic character of its creation. Microscopic model calculations are also presented.

Inelastic scattering of 600 MeV vector and tensor polarized deuterons has been carried out at energy losses corresponding to quasielastic, incoherent scattering from individual nucleons in targets of ${\mathrm{CH}}_2$, ${\mathrm{CD}}_2$, C, Ca, and Pb at fixed momentum transfers of 345 and $500\hspace{0.5em}\mathrm{MeV}/c$. Vector ${(A}_y)$ and tensor ${(A}_{\mathrm{yy}})$ analyzing powers were measured, and the vector polarizations $P_{y^{\prime }}$ of the scattered deuterons were determined by the polarimeter POMME. These observables were combined to determine the vector spin transfer coefficients $K_y^{y^{\prime }}$ for the deuterons and several signatures for spin transfer probabilities across the quasielastic spectra.

In the reactions ${}^{40}\mathrm{Ar}{+}^{232}\mathrm{Th}$ at $44A$ and $77A\hspace{0.5em}\mathrm{MeV}$ heavy fragments (HF) are produced in events where a large fraction of the incident energy is thermalized. These events are accompanied by, on the average, two intermediate mass fragments (IMF). The IMF’s have various origins: evaporation from a rather massive complex, projectile remnants, and from partially damped collisions. It is concluded that the heavy fragments are formed in semicentral collisions with light particle and IMF emissions which reduce the mass and excitation energy of the residual system such that fission becomes improbable. The HF production is found to be low at $27A\hspace{0.5em}\mathrm{MeV}$.

Measurement of elastic ${}^{16}\mathrm{O}{+}^{12}\mathrm{C}$ scattering at $E_{\mathrm{lab}}=132\mathrm{}\hspace{0.5em}\mathrm{MeV}$ has been performed over the angular range $6°<{\Theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}<125\mathrm{}°$, which covers both the diffractive and refractive regions. A prominent minimum has been observed at ${\Theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\approx 86°$, which can be identified as an Airy minimum preceding the rainbow maximum. It thus provides the first clear experimental evidence for the refractive (rainbow) scattering pattern in the ${}^{16}\mathrm{O}{+}^{12}\mathrm{C}$ system. This Airy structure can be well described by discrete sets of optical potentials with a relatively weak absorption and a deep real potential. Candidates for the realistic family of ${}^{16}\mathrm{O}{+}^{12}\mathrm{C}$ optical potentials at $E_{\mathrm{lab}}=132\mathrm{}\hspace{0.5em}\mathrm{MeV}$ are discussed; those include the semimicroscopic potential given by the double-folding model.

The mass-symmetric reactions ${}^{58}{\mathrm{F}\mathrm{e},}^{58}{\mathrm{Ni}\mathrm{}+}^{58}{\mathrm{F}\mathrm{e},}^{58}\mathrm{Ni}$ were studied at a beam energy of $E_{\mathrm{beam}}=30\mathrm{}\hspace{0.5em}\mathrm{M}\mathrm{e}\mathrm{V}/\mathrm{n}\mathrm{u}\mathrm{c}\mathrm{l}\mathrm{e}\mathrm{o}\mathrm{n}$ in order to investigate the isospin dependence of fragment emission. Ratios of inclusive yields of isotopic fragments from hydrogen through nitrogen were extracted as a function of laboratory angle. A moving source analysis of the data indicates that at laboratory angles around $40°$ the yield of intermediate mass fragments (IMF’s) beyond $Z=3\mathrm{}$ is predominantly from a midrapidity source. The angular dependence of the relative yields of isotopes beyond $Z=3\mathrm{}$ indicates that the IMF’s at more central angles originate from a source which is more neutron deficient than the source responsible for fragments emitted at forward angles. The charge distributions and kinetic energy spectra of the IMF’s at various laboratory angles were well reproduced by calculations employing a quantum molecular-dynamics code followed by a statistical multifragmentation model for generating fragments. The calculations indicate that the measured IMF’s originate mainly from a single source. The isotopic composition of the emitted fragments is, however, not reproduced by the same calculation. The measured isotopic and isobaric ratios indicate an emitting source that is more neutron rich in comparison to the source predicted by model calculations.

The yield $Y$ of the ${}^{180}{\mathrm{Ta}}^m(\gamma ,{\gamma }^{\prime }{)}^{180}{\mathrm{Ta}}^g$ ($T_{1/2}=8.15\mathrm{}\hspace{0.5em}\mathrm{h}$) reaction has been measured as a function of the bremsstrahlung end-point energy $E_e$ in the range of 2.5–7.6 MeV. An activation technique was used for the yield measurement which was calibrated by monitoring the ${}^{232}\mathrm{Th}(\gamma ,f)$ reaction yield. The ${Y(E}_e)$ function was numerically simulated and the probability ${\sigma }_g/({\sigma }_g+{\sigma }_m)$ for the depletion of the ${}^{180}{\mathrm{Ta}}^m$ isomer after $\gamma$-ray absorption was deduced. This probability is important for astrophysical questions and schemes for producing induced γ emission and perhaps a $\gamma$-ray laser.

The ${}^4\mathrm{He}\left(\alpha {,t)}^5\mathrm{Li}\right(\mathrm{g}.\mathrm{s}.\mathrm{})\mathrm{}$ reaction was investigated at incident energies of 120, 160, and 200 MeV in order to resolve discrepancies found between previous measurements and theoretical predictions for the analogous reaction ${}^4{\mathrm{H}\mathrm{e}(\mathrm{\alpha },}^3{\mathrm{H}\mathrm{e})}^5\mathrm{He}(\mathrm{g}.\mathrm{s}.\mathrm{})\mathrm{}$ at these energies. The line shapes of the ${}^5\mathrm{Li}$ ground-state resonance in the measured triton energy spectra are well reproduced by distorted-wave Born approximation (DWBA) calculations. Cluster-core optical potentials, which yield better overall agreement both for $\alpha -\alpha$ elastic scattering and for the single-nucleon transfer reactions, are presented. It is shown that the previously observed discrepancies in magnitude between measured and calculated cross sections by a factor of $\sim 2$ can be improved by employing spectroscopic factors obtained from a realistic shell model for the transitions to the final mass-3 and mass-5 systems.

Two-particle correlation functions at small relative momenta were measured in the binary fission processes for ${}^{40}\mathrm{Ar}{+}^{197}\mathrm{Au}$ reactions at 25 MeV/nucleon. Compared to trajectory calculations the mean emission times of light charged particles were determined from two-particle correlation functions. The emission times varied weakly with the mass of the particles, but strongly with the kinetic energy of the particles. A slightly shorter emission time was determined for the particles emitted in the fission plane compared to out of the fission plane due to preferential, in-plane preequilibrium emission with shorter emission time. The emission time of light particles was nearly independent of the mass asymmetry of the fission fragments, depending mainly on the degree of equilibration in the emitting nuclei. A very short emission time of less than 100 fm/$c$ was deduced for the preequilibrium emission of high-energy particle pairs with kinetic energy $E>~$20 MeV/nucleon while a long emission time of about 600–1000 fm/$c$ was deduced for emission of low-energy particles with $E<~$9 MeV/nucleon. Such a long time suggests evaporation for these low-energy particles from thermalized compound nuclei or fission fragments.

Assuming a binary reaction mechanism, the yield of isotopes near the heaviest $N=Z$ neutron-deficit nucleus ${}^{100}\mathrm{Sn}$ is studied with a microscopic transport model. The large influence of nuclear shell structure and isotope composition of the colliding nuclei on the production of exotic nuclei is demonstrated. It is shown that the reaction ${}^{54}{\mathrm{F}\mathrm{e}+}^{106}\mathrm{Cd}$ seems to be most favorable for producing primary exotic Sn isotopes which may survive if the excitation energy in the entrance reaction channel is less than about 100 MeV. In the case of large differences in the charge (mass) numbers between entrance and exit channels the light fragment yield is essentially fed from the decay of excited primary heavier fragments. The existence of optimal energies for the production of some oxygen isotopes in the binary mechanism is demonstrated for the ${}^{32}{\mathrm{S}+}^{197}\mathrm{Au}$ reaction.

In this paper we continue the investigation of the lattice gas model. The main improvement is that we use two strengths for bonds: one between like particles and another between unlike particles to implement the isospin dependence of nuclear force. The main effect is the elimination of unphysical clusters, such as the dineutron or diproton. It is therefore a better description of a nuclear system. The equation of state in mean field theory is obtained for nuclear matter as well as for $N\ne Z$ systems. Through numerical and analytical calculation we show that the new model maintains all the important features of the older model. We study the effect of the Coulomb interaction on multifragmentation of a compound system of $A=86\mathrm{}$, $Z=40\mathrm{}$, and also for $A=197\mathrm{}$, $Z=79\mathrm{}$. For the first case the Coulomb interaction has small effect. For the latter case the effect is much more pronounced but typical signatures of the lattice gas model such as a minimum (maximum) in the value of $\tau$ ${(S}_2)$ are still obtained but at a much lower temperature.

We present a theoretical analysis of recently published experimental data for the elastic scattering of protons from the helium isotopes ${}^6\mathrm{He}$ and ${}^8\mathrm{He}$ at energies near 700 MeV per nucleon. The analysis treats the few-body degrees of freedom of these light neutron-rich nuclei explicitly and is developed in terms of three- and five-body wave functions for ${}^6\mathrm{He}$ and ${}^8\mathrm{He}$, respectively. Comparisons of calculations with the data show that the sizes of the He nuclei consistent with such an analysis are larger by about 0.2 fm than those deduced from a more approximate procedure in which the structure of the weakly bound nuclei enters only through an assumed nuclear matter density.