The spurious state problem is generalized Dyson boson mapping is examined. For cases where the fermion space is restricted to at most four-quasiparticle excitations, we show that Dyson boson images of normal-ordered quasiparticle interactions have identically vanishing matrix elements in the unphysical boson space. This ‘‘decoupling’’ feature explains the finding of previous authors that, in systems with at most four quasiparticles, every spurious state appears at its unperturbed energy. However, we show that the decoupling property does not generally hold in problems where there are excitations of more than four quasiparticles. Claims about methods for the spurious state problem, even though verified in four-quasiparticle calculations, may therefore be of limited validity.

The cross section for creating, in high-energy heavy-ion collisions, a negatively charged meson such as ${\pi }^{\mathrm{-}}$ or $K^{\mathrm{-}}$ in the atomic orbits of the nuclear fragments is evaluated in the participant-spectator model. Its magnitude depends sensitively on the lifetime of the source. For a lifetime comparable to the collision time, the cross section is appreciable.

We reexamine a simple two-dimensional fission model and show that in the sudden limit the standard Wentzel-Kramers-Brillouin approximation gives results of practically the same accuracy as those obtained earlier by more elaborate semiclassical methods using complex paths.

An important role for three-particle collisions in nuclear matter is shown. The idea of a mean field is discussed. It is argued that the applicability of gas theory methods to the description of excited nuclear matter is very questionable.

The role of two-step processes in the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(e,e,’p${)}^{11}$B reaction has been investigated by studying the transition to the ${\mathrm{}(5/2)\mathrm{}}^{\mathrm{-}}$ state at $E_x$=4.45 MeV. In a (1s${)}^4$(1p${)}^8$ shell-model space this state cannot be excited by a one-step process, and a secondary process is therefore required. Such processes are found to be sufficiently small to enable the study of small wave-function components with the (e,e’p) reaction.

The ${}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}$(α,α’n${)}^{91}$Zr reaction through the giant quadrupole resonance in ${}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}$ was studied with α’-n correlation measurements. Three groups of fast neutrons decaying from the giant quadrupole resonance were found, which leave single-neutron-hole states of (i) 2d${\mathrm{}(5/2)\mathrm{}}^{\mathrm{-}1}$, (ii) 1g${\mathrm{}(9/2)\mathrm{}}^{\mathrm{-}1}$, and (iii) 2$p^{\mathrm{-}1}$ and 1$g^{\mathrm{-}1}$ in the residual ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}$ nucleus. They indicate the microscopic particle-hole configuration of the giant quadrupole resonance. The direct fast decay branch is about 16%.

For the long time delay apparently needed for the spontaneous decay of the quantum-electrodynamic vacuum in reactions of very heavy ions (U+U, U+Cm), it is necessary that the deformed nuclei collide with a well-defined orientation. Because of dynamic orientation of the nuclear quadrupole moments, the probability for ‘‘favorable’’ alignment is calculated to be only about one percent. Implications for observing the vacuum decay are discussed.

We present results for nucleon-deuteron elastic scattering obtained for the first time with a genuine meson-exchange nucleon-nucleon interaction. In particular, we employ the Paris potential and introduce it into momentum-space Faddeev calculations. Predictions are made for n-d differential cross sections at $E_{\mathrm{n}=8\mathrm{}}$, 10, 10.25, and 12 MeV and for nucleon-to-nucleon spin transfers of the process ${}_{}{}^2{}_{}{}^{}$H(N,${\mathrm{N})\mathrm{}}^2$H at $E_{\mathrm{N}=10\mathrm{}}$ MeV. Comparison of these results with modern experimental data allows for a sensible test of the reliability of the underlying nucleon-nucleon interaction.

Fluctuations in the pseudorapidity or the azimuthal angle distribution of secondary particles in three emulsion nucleus-nucleus events are analyzed using a statistical model with simulation. The local density, the power spectrum, and the Chebyshef expansion are used to define various measures of the fluctuations. Fairly strong signals for nonstatistical fluctuations are found in all the events. The most remarkable feature is the concentration of the signals into a long wavelength region in qualitative agreement with the prediction from models of decay of quark-gluon plasmas.

A comprehensive theoretical and experimental investigation of electron scattering on ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ is presented. Theoretical procedures for calculating the various components of electron scattering form factors from multiparticle shell-model wave functions are summarized. These procedures are used to compare shell-model predictions with data from electron scattering on ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$. For the positive-parity states of ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ we use 1s0d shell-model wave functions obtained with a new ‘‘universal’’ Hamiltonian and for the negative-parity states we use 0p-1s0d shell-model wave functions based on the cross-shell Hamiltonian of Millener and Kurath. The comparisons are made with measured longitudinal and transverse form factors for momentum transfers up to 2.4 ${\mathrm{fm}}^{\mathrm{-}1}$ which are extracted from experimental data obtained with electron energies from 78 to 340 MeV, and angles of 45°, 90°, and 160°. The energy resolution was 25–50 keV and most of the known levels below 8 MeV in excitation were resolved and compared with theory.

Surface effects on direct particle emission in the exciton model of preequilibrium nuclear reactions are described in terms of the mean effective well depth in the region of the first target-projectile interaction. A simple parametrization for this quantity as a function of the bombarding energy is derived, and its predictive ability is demonstrated. There is no evidence for a mass dependence of the parameter values. The question of surface effects is found to be tied to the assumed energy dependence of the single particle state density. A Fermi gas model square root dependence is used in this work. Only (nucleon, nucleon) reactions are considered, but sizable effects on complex particle spectra are anticipated.

Optical model calculations with double-folded microscopic real central and spin-orbit potentials and an imaginary Woods-Saxon potential have been carried out for previously reported t→${+}^{12}$C and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ elastic scattering data. The t→${+}^{12}$C calculations are not able to reproduce the changes in the measured analyzing powers as a function of bombarding energy, whereas they do describe the t→${+}^{58}$Ni data. This analysis suggests that information about the cluster-core t→${+}^{12}$C spin-orbit potential, necessary for cluster structure calculations, cannot be determined without considerably more data. Three-particle-transfer reactions leading to ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ show numerous structures that could appear in the t${+}^{12}$C entrance channel. Excitation functions are needed for both the elastic and 4.43 MeV first excited state in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ if this scattering is to be understood.

Differential cross sections for the elastic scattering of tagged, monochromatic photons have been measured for targets of carbon and calcium between 19 and 52 MeV. The formalism for the interpretation of these cross sections in terms of the total photoabsorption cross section and its partitioning into E1 and E2 parts is presented. For carbon, we find excellent agreement between the photoabsorption deduced from the scattering and previous direct measurements. The fore-to-aft asymmetries in the cross sections indicate that the bulk of E2 strength is above 50 MeV and not between 30 and 45 MeV, as previously thought. For calcium, the scattering data indicate that the integrated photoabsorption cross sections per nucleon are closer to the nearly constant value reported for A>100 than previously thought. No compact E2 strength exhausting more than 0.5 classical sums is found below 50 MeV, although weaker or less compact strength cannot be ruled out.

A model for the N-N interaction is proposed which has a long range part to account for the low energy properties and a short range component to incorporate the quark degrees of freedom. Based on the quark compound bag model, Simonov recently derived a short range repulsive core which is nonlocal and, with a characteristic energy dependence, can be expressed in terms of the parameters relating to the six-quark compound bag. Adding to it an s-wave separable potential for the long range component which is only operative outside the bag radius, we here study n-p scattering in ${}_{}{}^3{}_{}{}^{}\mathrm{S}_1^{}{}_{}{}^{}$ and ${}_{}{}^1{}_{}{}^{}\mathrm{S}_0^{}{}_{}{}^{}$ states for laboratory energies up to 400 MeV and the electromagnetic form factor for the deuteron. The parameters obtained to reproduce the data are compared with those of earlier investigations. The short range parameters, and, in particular, the bag range parameter, are found to have a marked variation from the one obtained in the P-matrix analysis.

The integrated and bremsstrahlung-weighted cross section for deuteron photodisintegration have been calculated taking the relativistic one-body charge density and the two-body charge density with its local and nonlocal contributions for several nucleon-nucleon potentials in pseudoscalar and pseudovector pion-nucleon couplings. The relativistic correction lowers the enhancement factor for the soft-core potentials and raises it for the hard-core potentials as well as for the Paris potential which has velocity dependence in it to simulate the effect of the hard core. This increase and decrease pattern of the enhancement factor is found to be related to the maxima of the deuteron ground-state wave functions. Though there are some changes in the enhancement factor for different potentials, they are not large enough to enable us to distinguish between the various hard-core or soft-core nucleon-nucleon potentials.

We report on a microscopic calculation of the spreading width ${\Gamma }_A^{\downarrow }$ of the isobaric analog state in ${}_{}{}^{49}{}_{}{}^{}\mathrm{Sc}$ of the ground state of ${}_{}{}^{49}{}_{}{}^{}\mathrm{Ca}$. In calculating the coupling of the isobaric analog state to hallway states we included (1) first and second order Coulomb coupling, (2) a charge-dependent but charge-symmetric interaction from the mass difference between charged and neutral pions, and (3) a charge-asymmetric interaction fitted to the Coulomb displacement anomaly in ${}_{}{}^{41}{}_{}{}^{}\mathrm{-}_{}^{41}{}_{}{}^{}$Ca. The second order Coulomb terms arise from mixing with the T=(7/2) component of a giant isovector monopole. The different sets of matrix elements are found to add coherently to give ${\Gamma }_A^{\downarrow }$=5–7 keV, in excellent agreement with the value of ${\Gamma }_A^{\downarrow }$=5.3 keV which we obtain from a strength function analysis of the high resolution data on ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$(p,p). The coherent charge-symmetric–charge-dependent contribution gives approximately one-half of ${\Gamma }_A^{\downarrow }$. The result for ${\Gamma }_A^{\downarrow }$ also includes a charge-asymmetric reduction of about 1 keV, but this is too small to confirm its presence in view of the uncertainty in the value of ${\Gamma }_A^{\downarrow }$. .AE

Data for the diffraction region of the elastic scattering of 42–140 MeV α particles from ${}_{}{}^{42}{}_{}{}^{}$,44,48Ca have been compared to calculations based on Hartree-Fock nuclear densities. The α-particle optical potential was obtained from the densities using a double folding model where the effective interaction was adjusted to the scattering from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. This study is insensitive to the details of the reaction calculation because it is restricted to the diffraction region and is only for the purpose of comparing relative sizes. The predicted cross section is in good agreement with data indicating that the theoretical densities are correct in the vicinity of 10% of central density to approximately ±0.1 fm. This uncertainty is dominated by the approximations in the reaction calculation.

The recoil range distributions of ${}_{}{}^{61}{}_{}{}^{}\mathrm{Cu}$, ${}_{}{}^{60}{}_{}{}^{}\mathrm{Cu}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Co}$, ${}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$, ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$, ${}_{}{}^{54}{}_{}{}^{}\mathrm{Mn}$, and ${}_{}{}^{52}{}_{}{}^{}\mathrm{Mn}$ residual nuclei produced in α particle bombardment of ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$ at 38, 50, 65, and 85 MeV have been measured and analyzed. Analysis of these measurements, as well as other recently published measurements of longitudinal linear momentum transfer to residue isobars at energies extending up to ≊200 MeV, in the same reaction, shows that calculations based on the exciton model and a realistic description of the α-nucleus interaction allow a quantitatively correct description of α-induced reactions. Contrary to recent suggestions, data of this kind do not seem to indicate a change in the general character of the α-nucleus interaction for incident energies below ≊50 MeV/nucleon.