The analysis of the eigenvalue spacing of the shell-model Hamiltonian has been performed and related systematics have been provided. Large differences between densities of particle and hole excitations and strong isotopic and isotonic effects are found. A method of estimating the particle-hole state density, which takes into account these effects, has been proposed.

The rank-one separable part of the W-matrix representation of the t matrix for the Malfliet-Tjon I-III nucleon-nucleon potential has been shown to lead to results for the triton binding energy and low-energy ($E_{\mathrm{lab}\mathrm{\le }50}$ MeV) nucleon-deuteron scattering that agree well with results for that potential obtained by solving the full local-potential equations. We explore why this prescription appears to work so well for the Malfliet-Tjon I-III model and test it further using the Reid-soft-core spin-singlet interaction, which possesses a very strong short-range repulsion (a stiff core). For this model, a calculation using the rank-one separable part of the W-matrix representation of the two-body t matrix overbinds the triton by 25%.

The information of the equation of state of cold nuclear matter is extracted from the experimental nuclear masses by the droplet model. The result shows the asymmetry dependence of the equation of state in a more direct way than has been done before. It shows that the spherical or the deformed nuclear region appears alternately as the bulk nucleon density of the core of nuclei increases. An explanation of why the rms fit of the droplet model to the nuclear masses gives a very broad minimum region of the nuclear compressibility is possible based on this work.

A systematic method is devised to determine self-consistently the structure of the correlated S pair and D pair in a state with many such pairs. These pairs are defined to be independent from each other and without seniority mixing. They, however, block each other because of the Pauli principle. The method follows similar lines to the Hartree-Fock method for fermions.

A reexamination of the γ-ray spectrum of ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ has revealed a previously unobserved transition of 852.78(5) keV decaying with the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ half-life. Its intensity is 0.050(3) relative to $I_{847}$=100. Alternate explanations for this peak, such as summing, have been ruled out and the γ ray is assigned as the 4298.0(4+)→3445.3(3+) transition in ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ with a branching ratio of 1.4(1)%. Assuming an M1 assignment and a negligible E2 component, we find B(M1)=6.5(30)×${10}^{\mathrm{-}3}$ W.u., which lies between the B(M1) values for the other two M1 transitions from the 4298-keV state.

Photons from the reaction ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{\mathrm{nat}}$W have been measured using the Darmstadt-Heidelberg crystal ball. The source velocity for photons above 25 MeV deduced from the angular distribution identifies the nucleon-nucleon system as the emitting system consistent with proton-neutron bremsstrahlung. This observation is supported by a comparison of the experimental angle-integrated spectra with statistical model calculations, which suggest that photons below 20 MeV arise from thermal emission, whereas hard photons above 25 MeV cannot be explained by this mechanism.

We investigate the feasibility of identifying the spin monopole isovector resonance from the quadrupole contribution occurring at the same energy. In that context, we present the result of a continuum random-phase-approximation calculation which clearly indicates that because of very different momentum transfer patterns for L=0 and L=2 resonances, the spin monopole should be easily identifiable in reactions like ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$(n,p) at forward angles or low momentum transfer.

The temperature dependence of the specific heat for a finite system of fermions is investigated for some simple models. It is found that finite-size effects produce a maximum in the specific heat at a temperature $T_c$ that has a universal value when scaled by the appropriate characteristic energy.

It is shown that the energy shift of the π$h_{11/2}$ orbit near N=90, which results in the collapse of the Z=64 subshell gap, affects the behavior of low-energy octupole states in the vicinity of Gd.

A matrix element of a many-body Green’s function is estimated via a multiple integral over a basis of products of single-particle wave functions. Saddle points of this integral generate Hartree (-Fock) equations. The result is applied to a simple, correlated kinetic energy model.

We establish the relationship between the partial-wave analysis of the pp→pn${\pi }^{+}$ reaction by Shypit et al. [Phys. Rev. Lett. 60, 901 (1988); 61, 2385 (1988)] and the unitary formulation of the πNN problem. It is shown that the NΔ phases extracted by Shypit et al. are not exclusively due to the NΔ interaction.

Limits on the scalar and induced-scalar coupling constants are established from experimental ft values of superallowed Fermi transitions. The role of the uncertainties in the ft values is discussed, leading to minimal coupling strengths that can be extracted from ft values. The implications for the Kobayashi-Maskawa mixing angles are also discussed.

Multiplicity distributions of intermediate mass fragments observed in the reactions ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$${+}^{\mathrm{nat}}$Ag and ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$${+}^{197}$Au at E/A=84 MeV are compared to statistical model calculations. The emission of intermediate mass fragments from a highly excited ($E_x$/A≥6 MeV) A=100 nucleus is found to be suppressed compared to the predictions of a sequential statistical evaporation model. This deficiency may be interpreted as resulting from dynamical constraints imposed by the finite time necessary to emit complex fragments.

We briefly review the status of recent analyses of kaon photoproduction data. The utility of future measurements of other kaon photoproduction observables is discussed. We note that a set of target polarization data has been neglected in all recent analyses. The constraint imposed by this data set is illustrated.

Using an independent nucleon model, it is shown that p- and ${}_{}{}^{12}{}_{}{}^{}\mathrm{induced}$ subthreshold pion production can be described with a similar reaction process. The ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ momentum distribution determined in that way is comparable to that obtained from high-energy proton backward scattering.

Recently published direct capture model calculations for the ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$(p,${\gamma }_0$,1) reaction are critically commented on with respect to the selection of the entrance channel interaction potential, which in our opinion led to an overestimate of the cross section values.

We reply to the preceding Comment.

The skeleton boson realizations of fermion collective subalgebras proposed by Kim and Vincent are discussed. The Dyson boson mapping is found to play an essential role in the possibility of such realizations. A simple but instructive example is given to show that a straightforward application of the ‘‘skeletonization procedure’’ to the Holstein-Primakoff boson mapping may lead to serious errors in reproducing the fermion matrix elements. A possible way of constructing the modified skeleton Holstein-Primakoff realization of the collective subalgebra is suggested.

Photons with energies of 5–40 MeV have been measured in the ${}_{}{}^{12}{}_{}{}^{}$C${+}^{112}$,124Sn reactions at incident energies of 7.5 and 10.5 MeV/nucleon and at laboratory angles of 60°, 90°, and 120°. Statistical model calculations which describe the photon yields in the 5–20 MeV photon energy range cannot account for the relatively large yields measured at $E_{\gamma }$>20 MeV. For these energies, the angular distribution suggests photon emission from a source moving at the nucleon-nucleon center-of-mass velocity. The magnitude of the nonstatistical photon yields is roughly consistent with a scaling relationship based on nucleon-nucleon bremsstrahlung. However, this does not account for the observation that the ${}_{}{}^{124}{}_{}{}^{}\mathrm{Sn}$ yield is considerably larger than the ${}_{}{}^{112}{}_{}{}^{}\mathrm{Sn}$ yield and suggests differences in the neutron-proton dynamics play a role in these low energy collisions.