Six-quark configurations relevant to N-N scattering and bound states are constructed from parity eigenfunctions which can be obtained from any static independent particle model. The two lowest, one even and one odd, parity orbitals are considered. In the (TS)=(10) and (01) sectors, there are 16 orthogonal color-singlet configurations of various orbital-spin-isospin symmetries; there are 7 in the (00) and 25 in the (11) sectors. The results obtained here are compared with the cluster model approach for single particle s states in each cluster. In that model, certain $p^n$$s^{6\mathrm{-}n}$ components disappear from the wave function in the zero-separation limit, whereas the parity eigenfunction representation preserves a symmetry between even and odd parity states (with respect to the center of mass). Furthermore, cluster model configurations have been limited to three-quark clusters, which also limits the number of basis states. It is demonstrated here how parity eigenfunctions can be constructed from cluster model functions, and utilized to build the ‘‘missing’’ basis states.

The three models for the structure of ${\mathrm{S}}^{\mathrm{*}}$, where it is considered as a member of the qq¯ L=1 nonet, or as a member of the lightest $q^2$q¯ ${}_{}{}^2{}_{}{}^{}$ nonet or as a KK¯ molecule, can be distinguished by studying the A dependence of the production cross sections at high energies of the inclusive reaction π+A→${\mathrm{S}}^{\mathrm{*}}$+X and of the exclusive reaction π+A→${\mathrm{S}}^{\mathrm{*}}$+N+(A-1). The energy dependence of the inclusive cross section can provide an independent test for the KK¯ molecular model where we find a depletion in the cross section at energies corresponding to the ${\mathrm{Y}}^{\mathrm{*}}$ resonances of the K¯-nucleon system.

The experimental information on reactions induced by stopped ${\pi }^{\mathrm{-}}$ absorbed in nuclei is critically reviewed. Evidence for the presence of α-cluster absorptions is presented and arguments are given to show that ≊25% of ${\pi }^{\mathrm{-}}$ absorptions are of this kind. In the case of two-nucleon absorption, the existing experimental information concerning the ratio of n-p to p-p absorbing pairs is discussed. Calculations of particle spectra and residue spallation yield distributions that, in addition to two-nucleon absorption, include α-cluster absorption are presented, and it is shown that a satisfactory reproduction of the data is achieved.

The decay of ${}_{}{}^{80}{}_{}{}^{}\mathrm{Zn}$ to levels in ${}_{}{}^{80}{}_{}{}^{}\mathrm{Ga}$ has been studied from mass-separated activity produced in the thermal neutron fission of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$. Based on γ singles and coincidence measurements, 26 γ rays were placed in a level scheme for ${}_{}{}^{80}{}_{}{}^{}\mathrm{Ga}$ with 13 excited states up to 2655 keV. The emission of a γ ray resulting from delayed neutron emission of ${}_{}{}^{80}{}_{}{}^{}\mathrm{Ga}$ is also reported. The structure of the ${}_{}{}^{80}{}_{}{}^{}\mathrm{Ga}$ level scheme is discussed. The properties of ${}_{}{}^{80}{}_{}{}^{}\mathrm{Zn}$ and ${}_{}{}^{80}{}_{}{}^{}\mathrm{Ga}$ reported here are of astrophysical interest for modeling the r process.

Gamma radiation and delayed neutrons following the decay of 44.9 ms ${}_{}{}^{29}{}_{}{}^{}\mathrm{Na}$ have been studied in singles and coincidence mode with mass-separated sources. Evidence for a first excited state in ${}_{}{}^{29}{}_{}{}^{}\mathrm{Mg}$ at 54.6 keV has been found, in good agreement with theoretical predictions. From the lifetime, τ=1.83±0.10 ns, deduced from γ-γ delayed coincidences with ${\mathrm{BaF}}_2$ counters, a transition strength B(M1)=0.11 Weisskopf units is found for the 55 keV ${(1/2\mathrm{}}^{+}$)→g.s. ${\left(\right(3/2\mathrm{}}^{+}$) transition. A level scheme built on the new state at 55 keV and involving five new transitions has been established for bound levels in ${}_{}{}^{29}{}_{}{}^{}\mathrm{Mg}$. The features of these levels are compared with predictions of shell-model calculations, with which they substantially agree. In the neutron time-of-flight spectra, high-energy neutron branches have been found in addition to the previously reported decays. The observed distribution of the Gamow-Teller transition strengths with excitation energy for particle-unbound levels in ${}_{}{}^{29}{}_{}{}^{}\mathrm{Mg}$ is found to be shifted upward by about 1 MeV relative to shell-model predictions.

A method based on an eigenmode condition and projection techniques is presented for solution of a general quadrupole Hamiltonian in the interacting boson model. It is shown that the intrinsic states obtained from the eigenmode condition provide a zeroth order solution to the diagonalization of the corresponding quadrupole Hamiltonian. The method is in effect a 1/N expansion, where N is the boson number, ideally suited for the deformed nuclei for which N≊12–16. Because of certain cancellations with the normalization, zeroth order solutions of the intrinsic states are sufficient to obtain matrix elements to order O(1/$N^2$).

Alpha particle cluster structure is known experimentally to persist throughout the mass range 16≤A≤20, and has been very successfully described in this region in terms of the Buck-Dover-Vary local potential cluster model. It is argued that an analogous cluster structure should be present in nuclei at the beginning of the fp shell, and the available experimental data are examined to determine likely alpha particle cluster state candidates in the mass range 40≤A≤44. Calculations of the cluster state spectra and mean square cluster-core separation distances (which may be readily used to evaluate E2 electromagnetic transition rates) for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{42}{}_{}{}^{}\mathrm{Sc}$, ${}_{}{}^{43}{}_{}{}^{}\mathrm{Sc}$, ${}_{}{}^{43}{}_{}{}^{}\mathrm{Ti}$, and ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ using the above-mentioned model are presented, and compared with experimental measurements where possible. The agreement between theory and experiment is generally good (although inferior to that obtained in the sd shell), and points to the desirability of an extension and improvement of the measurements of the properties of the excited states in these nuclei.

The nuclear thermodynamical quantities at low excitation energy are studied in terms of the temperature-dependent antisymmetrized density matrices of many fermions in a harmonic oscillator well. The relationship between this treatment and the conventional shell model is studied. The nuclear level density is formulated and compared with the conventional formula. It is found that characteristic features of nuclear level densities observed experimentally are reproduced. Also the excitation energy dependence of the level density parameter a is found.

Highly excited nuclear states formed by high energy heavy-ion collisions are studied in terms of the temperature-dependent antisymmetrized density matrix of many fermions in a harmonic oscillator well. The particle inclusive spectrum and multiplicity are studied with the density matrix derived. The deuteron formation probability, the coalescence model, and the d/pn and d/p ratios are formulated and studied. The relationship between the d/p ratio and the entropy is discussed. It is found that quantities obtained are consistent with those found in high energy heavy-ion collisions.

A formulation is given to derive an effective interaction in the framework of the unitary-model-operator approach. A unitary transformation is introduced to describe two-body correlations and is determined from the condition that the effective interaction should be decoupled between the low- and high-momentum spaces. A unitary transformation of the Hamiltonian is made and the transformed Hamiltonian is represented in a cluster-expansion form. The effective interaction thus defined is E independent and Hermitian. The contributions of one-, two-, and three-body-cluster terms are taken into consideration. The self-consistent single-particle potential is considered sym- metrically for both occupied (hole) and unoccupied (particle) states. The theory is applied to the calculation of the ground-state properties of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ using three potentials, namely, the Paris, Reid soft-core, and supersoft-core potentials. A large gain in the binding energy is obtained. Final results for the gound-state energy and the charge radius are as follows: -119.2 MeV and 2.62 fm for the Paris, -115.1 MeV and 2.60 fm for the Reid soft core, and -121.7 MeV and 2.62 fm for the supersoft core. The single-particle energies of the occupied orbits are also calculated. Good agreement between the calculated and experimental energies is obtained. In particular, a large spin-orbit splitting of the 0p orbits is reproduced with the results 5.6 MeV for the Paris, 5.1 MeV for the Reid soft core, and 5.4 MeV for the supersoft core, which should be compared with the experimental value 6.1 MeV.

New experiments are suggested to search for neutrinoless double-beta decay between pairs of single-beta emitters. This addresses the Majorana mass of the neutrino. The electron capture decay mode for single-beta emitters is much easier to investigate than the previously considered beta-decay modes. The experimental problems introduced by the bremsstrahlung background are examined. Actual implementation of these experiments appears somewhat beyond current technical means.

The (t→,α) reactions have been studied on ${}_{}{}^{191}{}_{}{}^{}$,193Ir targets. The analyzing power to the $2_2^{+}$ state in ${}_{}{}^{192}{}_{}{}^{}\mathrm{Os}$ does not indicate single step $d_{3/2}$ proton transfer. Implications of this result for the theoretical interpretation of earlier (d${,}^3$He) measurements in terms of supersymmetries are discussed.

With the use of an on-line isotope separator, ${}_{}{}^{149}{}_{}{}^{}\mathrm{Tm}$ ($T_{1/2}$=0.9±0.2 s) was identified in ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ bombardments of ${}_{}{}^{94}{}_{}{}^{}\mathrm{Mo}$. Seven γ rays were observed to follow the isotope’s (${\beta }^{+}$+electron capture) decay, including the 111.3-keV transition known from ${}_{}{}^{149}{}_{}{}^{}\mathrm{Er}_{}^{\mathrm{m}}{}_{}{}^{}$ isomeric decay to be the $d_{3/2}$ (111.3 keV)→$s_{1/2}$ (0.0 keV) γ ray in ${}_{}{}^{149}{}_{}{}^{}\mathrm{Er}$. In addition to the previously known levels at 111.3 ($d_{3/2}$) and 741.5 ($h_{11/2}$) keV in ${}_{}{}^{149}{}_{}{}^{}\mathrm{Er}$, our data establish three other excited states, at 907.4 ${\left(\right(5/2\mathrm{}}^{+}$), 1066.2 ${\left(\right(7/2\mathrm{}}^{\mathrm{-}}$), and 1482.9 ${\left(\right(9/2\mathrm{}}^{\mathrm{-}}$, ${(11/2\mathrm{}}^{\mathrm{-}}$) keV. Coincidences observed between Er K x rays and protons in the A=149 mass chain show that ${}_{}{}^{149}{}_{}{}^{}\mathrm{Tm}$ is a β-delayed proton precursor.

Angular distributions of recoil nuclei were measured in coincidence with low-energy intermediate-mass fragments emitted in ${}_{}{}^{14}{}_{}{}^{}\mathrm{induced}$ reactions on Ag at E/A=35 MeV. The measured correlations are inconsistent with a purely binary reaction mechanism. The incomplete linear momentum transfer mechanism alone does not reproduce the data, which show evidence for emission of additional matter to the same side of the beam axis as the intermediate-mass fragment.

The ${}_{}{}^{204}{}_{}{}^{}$,206,207,208Pb(p,xn) reactions have been investigated at $E_{\mathrm{p}}$=25.5 MeV. The hard energy spectra and the structures observed in the preequilibrium continuum are attributed to the nearby double shell closure. Application of semiclassical preequilibrium models requires the reduction of the state density g and/or the use of (1p)(1n${)}^{\mathrm{-}1}$ state densities based on realistic single particle level schemes.

Recent data on two-nucleon stretched high-spin states agree well with the crude shell model predictions. For two-neutron high-spin states, the A and T linear dependence of $B_{2\mathrm{n}}$ in the Bansal-French model can be deduced from the A and T linear dependence of $B_{\mathrm{n}}$ and the crude shell model. $7_2^{\mathrm{-}}$ states in some Zn and Ge even nuclei might be two-proton states. This hypothesis should be confirmed by two-proton transfer reaction.

A method is proposed to evaluate the nuclear compressibility in a Thomas-Fermi self-consistent approach at finite temperature with a suitably modified Skyrme force. The saturation curves of the Helmholtz free energy versus the root mean square radius of the matter distribution for ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ show a minimum which becomes shallower at T=6 MeV. The compressibility decreases with increasing temperature and at T=6 MeV reaches a value which is less than half of its value at zero temperature.

The differential cross section for ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(γ, ${\pi }^0$${)\mathrm{}}^2$H for photon energies from 500 to 800 MeV is calculated based on elementary processes. A comparison between calculated results and the experimental data at large angles demonstrates that double scattering becomes dominant in this region and that dibaryon resonances make no contribution to within the experimental accuracy.

The nature of the appearance of the spurious states in the ideal boson basis states is investigated. It is shown that the occurrence of the spurious states can be mainly attributed to the orthogonality of the boson basis states. It is further observed that the matrix element of the pairing interaction between the ideal boson basis is identical to the corresponding fermion matrix element.

It is shown that experimental g factors and B(E2) values of $2_1^{+}$ states in even-even nuclei can be consistently analyzed in order to simultaneously provide the effective numbers of both valence protons ($N_{\mathrm{p}}$) and neutrons ($N_{\mathrm{n}}$) for the respective shells. This method uses a simple linear relationship for g${(2\mathrm{}}_1^{+}$) and an improved analytic formula for the B(E2) values. It is applied to the transitional nuclei in the A=150 region and shown to give results reflecting the presence of a Z=64 subshell for N≤88.