Differential cross-section and vector analyzing-power angular distributions were measured at ${\mathit{E}}_{\mathit{p}\to }$ =58 MeV for the ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$(p→,d${)}^{89}$Zr reaction in the angular range from 6° to 50° and up to 10 MeV excitation energy, with 80 keV energy resolution. In addition to the transitions to low-lying states, the spectra display strong clusters of states from ${\mathit{E}}_{\mathit{x}}$=3.5 to 7 MeV. The observed fine structure was used to define energy bins for which cross sections and analyzing powers were obtained. The latter allowed spin and parity assignments for deep-lying hole states. Spectroscopic factors were deduced from standard distorted-wave Born approximation calculations. From the vector analyzing-power measurements, it was shown that most of the strength observed above 3.5 MeV belongs to the 1${\mathit{f}}_{7/2}$ inner neutron hole orbital.

In this paper, the dynamical symmetry concept is used to investigate the quantum integrability of nuclear many-body systems. It is found that such systems are generally nonintegrable due to the complicated inherent interactions. In fact, in certain regions of the intrinsic parameters, the time-dependent mean-field solution can be chaotic. However, when subdynamical symmetries, e.g., certain excitation modes, dominate, the corresponding dynamics will be rendered regular, thus signaling that the nuclear many-body system is not fully chaotic. Chaotic behavior emerges in the transitional region between the excitation modes where subdynamical symmetries are broken and accompanied by structural phase transitions.

Some years ago, Drisko et al. suggested that the discrete ambiguity often encountered for elastic scattering optical potentials could be understood as being due to the interior or small-l S-matrix elements for two ‘‘equivalent’’ potentials differing in phase by 2π, l-by-l. We point out that the absence of this phase change for peripheral partial waves is equally essential, and suggest that a deeper understanding of the ambiguity may be achieved by viewing it as a consequence of a farside interference between interior and peripheral partial waves. It is this interference which produces the broad ‘‘Airy maxima’’ of a nuclear rainbow, and we show that a Drisko-type phase-shift increment ${\mathrm{\delta }}_{\mathit{l}}$→(${\mathrm{\delta }}_{\mathit{l}}$+π) for low-l phases relative to the high-l ones is exactly what is needed to shift a farside rainbow pattern by one Airy maximum, thus providing an equivalent ‘‘rainbow-shift’’ interpretation of the discrete ambiguity. The physical importance of both interpretations lies in the fact that the existence of discrete ambiguities (as well as of nuclear rainbows) is explicit evidence for low-l transparency in nucleus-nucleus collisions. The essential role played by low partial waves explains why peripheral reactions have generally not proven helpful in resolving this ambiguity.

The approach to y scaling previously adopted to obtain the nucleon momentum distribution in the two- and three-nucleon systems is extended to the case of complex nuclei and nuclear matter. The basic elements of this approach, which takes properly into account nucleon binding and momentum, are reviewed. A new method of analysis, which allows one to obtain the experimental asymptotic scaling function from inclusive cross sections even if these data are affected by final-state interactions, is proposed and illustrated. By such a method, the asymptotic scaling functions of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$, and nuclear matter are obtained from recent experimental data and it is demonstrated that, particularly at high negative values of the scaling variable, the available data points at the highest value of the momentum transfer are affected by final-state interaction and cannot therefore be considered to represent the asymptotic scaling function. It is shown that, unlike what is commonly stated, the nucleon momentum distribution is not simply defined in terms of the derivative of the asymptotic scaling function, but as a sum of such a derivative plus the derivative of a quantity, the binding correction, generated by the removal energy distribution of nucleons embedded in the nuclear medium.

The binding correction and its derivative are evaluated with various types of spectral functions, and the nucleon momentum distributions in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$, and nuclear matter are obtained up to nucleon momenta k≊500 MeV/c. For few-body systems the obtained momentum distributions satisfactorily agree with the ones extracted from (e,e’p) reactions and with theoretical calculations performed within Faddeev or variational approaches, whereas for complex nuclei they qualitatively agree with predictions of theoretical many-body approaches which take nucleon-nucleon correlations into account and, at the same time, at k≥350 MeV/c they are larger by orders of magnitude than the ones predicted by mean field approaches. Such a result does represent unambiguous evidence of correlation effects in nuclei.

We demonstrate the construction of an exact sd-boson realization of the Sp(6) fermion dynamical symmetry model (Ginocchio model) from an application of the generalized Dyson mapping and subsequent truncation. This realization is an illustration of the validity of the procedure initiated by Geyer and Hahne and analyzed in full generality by Kim and Vincent. We discuss the connection of the Sp(6) model with the SU(3) limit of the interacting-boson model and the implications for the interpretation of its parameters.

The role of the hexadecapole degree of freedom in the description of band systematics in the rare-earth deformed nuclei is discussed. Using the 1/N expansion technique, we show that a self-consistent treatment of the quadrupole and hexadecapole modes can describe experimental systematics in the interacting boson model.

Through the example of the nucleus ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ taken as an α+p+n three-particle system, we show that the description of the disintegration of a multicluster system in terms of solely intercluster variables (‘‘macroscopic’’ description) cannot be maintained. The cluster internal structure enters into the spectroscopic amplitudes of macroscopic models through norm operators. The form in which these appear depends on how the macroscopic model is related to the underlying microscopic formalism. We assert that the treatment of the Pauli effects in the commonly used α+p+n models implies that these models are related to the six-nucleon problem via a transformation mediated by the square root of the α+p+n three-cluster norm operator. The spectroscopic amplitudes will then contain this operator and, in general, the norm operator of the two-cluster fragment involved. Using α+p+n wave functions available from the literature, we show that the inclusion of the norm operator required enhances the α+d spectroscopic factor by more than 30%. This reconciles the three-particle models with the microscopic models and improves the reproduction of experimental data. We point out that a smaller enhancement is expected in the spectroscopic factor of nucleon removal as well.

It is shown that the value obtained for the energy-weighted sum rule for bilinear fermionic operators using dressed one-particle propagators plus two-body random-phase approximation corrections is preserved when any higher-order correction is introduced. This is proven through the evaluation of the corresponding perturbative diagrams.

A generalized description of the variation of the mean field expressed in a coherent-state basis is presented. An appropriate form of the coherent state is used such that the parameters corresponding to creation operators of particle-hole pairs varying from -∞ to +∞ can be taken as the variables of of the Bohr-Mottelson model. The generators in the coherent state are classified into categories according to kinematic and dynamic properties. The collective modes are determined from the ground-state properties for deformed nuclei and from the lowest multipole vibrations for spherical nuclei. The general effective Hamiltonian is obtained in a systematic way as the continuous variable representation of the original Hamiltonian. The solution of the general effective Hamiltonian is discussed and the Bohr-Mottelson model is deduced by assuming that all modes except the quadrupole collective ones are kept fixed at their equilibrium positions.

Microscopic investigation of collective models is illustrated with the study of the multilevel pairing force model. The coherent-state description of pairing excitations through the variation of the pairing field and the classification of generators into collective and noncollective modes are discussed. Numerical calculations are performed for collective pairing rotations and vibrations built on the ground state. The coupling to the noncollective state is studied. Exact results from the Richardson method are given for comparison.

The variation of the configuration distribution of nucleons is described in a unified way with coherent states expressed by generators of the type of particle-particle pairs. The collective generators are determined from the ground state for deformed nuclei and from the lowest multipole vibrations for spherical nuclei. The general effective Hamiltonian in boson representation is derived in a systematic way. The interacting boson model II for collective bands on the ground state is directly deduced from the general effective Hamiltonian by neglecting the coupling to noncollective modes. The reduction of the interacting boson model II is discussed in the same way as in the derivation of the interacting boson model II itself. A critical analysis of the interacting boson model I is given. Some particular features of the paper are discussed in comparison to the previous studies.

Photoexcitation of the isomers of 19 nuclides was examined in this work. Four accelerators were used as sources of bremsstrahlung to expose the samples and end-point energies covered the range from 0.5 to 11 MeV. No evidence was found for nonresonant processes of excitation. However, more than half the cases showed enhanced channels for the resonant photoexcitation of isomers with integrated cross sections approaching ${10}^{\mathrm{-}21}$ ${\mathrm{cm}}^2$ keV. These results are three to four orders of magnitude larger than values usually characterizing (γ,γ’) reactions.

Inclusive spectra of different isotopes of He, Li, Be, B, C, and N nuclei emerging from the collisions of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ ions of energy 344.5 MeV with carbon, aluminum, and nickel target nuclei have been measured in the angular range of 4°–36° (laboratory). Experimental yields of reaction products are almost the same for the different targets. The continuous parts of momentum spectra have been decomposed into three components, corresponding to direct and damped fragmentation and to other processes, such as deep-inelastic and/or compound-nucleus reactions. At small angles (smaller than 20° in the laboratory system) the fragmentation processes dominate whereas at larger angles they become negligible in comparison to the other components. The direct fragmentation contribution is very small with respect to the damped one. The obtained reduced momentum widths of the direct fragmentation bumps are significantly smaller than those predicted by the Goldhaber model but agree with results obtained from other experiments at similar energies.

We report coincidence measurements of the (${\mathrm{\pi }}^{+}$,${\mathrm{\pi }}^0$p) reaction at a beam energy of ${\mathit{T}}_{\mathrm{\pi }}^{+}$=165 MeV. The neutral pions were detected by the LAMPF ${\mathrm{\pi }}^0$ spectrometer and the protons by an array of plastic-scintillator telescopes. The resulting energy resolution for the determination of the excitation energy of the residual nucleus was about 10 MeV. Measurements were performed on ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ at laboratory angles ${\mathrm{\theta }}_{\mathrm{\pi }}^0$=70°, 80°, 110°, and 130°. The cross section is predominantly quasifree. Its angular dependence follows the trend of the free single-charge-exchange cross section at back angles and is somewhat suppressed relative to this at more forward angles. Events corresponding to removal of p-shell nucleons were identified by their ${\mathrm{\pi }}^0$ and p energies. The ${\mathrm{\pi }}^0$ energy spectra for such events are compared to similar pion energy spectra for the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(${\mathrm{\pi }}^{\pm }$,${\mathrm{\pi }}^{\pm }$p) reactions; the cross-section ratios are consistent with ratios calculated from isospin coupling alone. ${\mathrm{\pi }}^0$ energy spectra are also compared to predictions of Δ-hole model calculations; the calculations for events in which protons are detected at the conjugate quasifree angle underestimate the (${\mathrm{\pi }}^{+}$,${\mathrm{\pi }}^0$p) cross sections by 30–55 %. At ${\mathrm{\theta }}_{\mathrm{\pi }}^0$=110° the (${\mathrm{\pi }}^{+}$,${\mathrm{\pi }}^0$p) reaction was also studied on Fe, Sn, and Pb. No significant A dependence of the cross section was observed.

We report new cross-section and analyzing power data for the excitation by 318 MeV protons of 20 states of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ below 14 MeV. The data for normal-parity isoscalar excitations are compared with calculations based upon the nonrelativistic impulse approximation using both density-independent and density-dependent interactions in the local-density approximation. These comparisons clearly indicate that density-dependent modifications of the effective interaction are required. Although the Paris-Hamburg, Nakayama-Love, and Ray interactions all predict significant medium modifications, none describes the data particularly well. Therefore, we fitted an empirical effective interaction to the data for five inelastic transitions simultaneously using a self-consistency cycle that maintains consistency between transition potentials and microscopic distorting potentials. This interaction describes the inelastic data as well as elastic data and data for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ which were not included in the fitting procedure. Therefore, the local-density approximation is supported by the phenomenology. However, medium modifications of the effective interaction are substantially stronger than predicted and persist to low density. The optical potentials are similar to the Schrödinger-equivalent potentials from the relativistic IA2 model, showing that the equivalent density dependence due to virtual NN¯ pairs is comparable to the short-range repulsion fitted to inelastic-scattering data.

Neutron folds in two high-efficiency neutron multiplicity meters (NMM) were measured in coincidence with projectilelike fragments from the ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$${+}^{56}$Fe reaction at a low bombarding energy of ${\mathit{E}}_{\mathrm{lab}}$=7.2 MeV/nucleon. Utilizing a complex Monte Carlo procedure to simulate both the fragment decay cascades and the response of the NMM’s, the average excitation energies of the fragments were deduced as functions of the total-kinetic-energy loss. The rather slow evolution of the experimental excitation energy partition from an equipartition at the initial stages of the collision towards its thermal equilibrium limit is found to be in quantitative agreement with the predictions of the one-body nucleon-exchange model.

We have used a low background detector with high efficiency for detection of bursts to search for emission of neutrons from Ti alloy in pressurized ${\mathrm{D}}_2$ gas cells (cooled to 77 K in liquid nitrogen). Each cell contained between 16 and 67 g of Ti alloy chips and was prepared by methods identical to those used in a recent Los Alamos-Brigham Young University collaboration of Menlove et al. Three to four cells were used in each experimental run, with a total counting time of 103 h, leading to an estimate (based on the early reports of Menlove et al.) of at least four bursts and as many as 12 bursts expected in our experiment. In a later report the burst rate of Menlove et al. is greatly reduced leading to only one or so burst(s) expected in our experiment. The data were analyzed in two modes. In the first mode (singles mode) all detectors were used to search for neutron bursts with an efficiency of 28% for neutron detection and a background of 100 counts per hour (cph). In the second mode (coincidence mode) the neutron time of flight was measured in a search for random emission with an efficiency of 2% and a background of 2 cph. No statistically significant deviations from the background were observed for correlated neutrons emitted in bursts or for neutrons emitted randomly. All events are shown (with 90% confidence) to be consistent with background. For bursts of neutrons we deduce (with 90% confidence) an upper limit on the bursts’ size of 50 neutrons. Our upper limit on the random emission of neutrons, 0.008 n/sec (90% confidence), is a factor of 6 to 25 smaller than the range of rates for random emission above background reported by the Los Alamos–Brigham Young University collaboration.

The average reaction cross section for 74- to 112-MeV α particles on ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}$ and ${}_{}{}^{133}{}_{}{}^{}\mathrm{Cs}$ was measured by a new method using a magnetic spectrograph and a CsI scintillation detector. The result, ${\mathrm{\sigma }}_{\mathit{R}}$=2220±50 mb, is in good agreement with optical model calculations and finite-range microscopic calculations. Zero-range microscopic calculations underpredict ${\mathrm{\sigma }}_{\mathit{R}}$ by about 10%, while strong absorption theories overpredict ${\mathrm{\sigma }}_{\mathit{R}}$ by large amounts.

Angular distributions for pion-induced double-charge-exchange (DCX) reaction have been measured at 164 MeV on the T=0 target nuclei ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$, and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. The data are compared to calculations using the Δ-nucleon interaction model with realistic wave functions and πNN and ρNN form factors deduced from fits to previously published DCX data on ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. The calculations reproduce the general shape of the angular distributions and the absolute magnitude of the cross sections to within a factor of two.

Target and target-like ejectiles emitted forward from ${}_{}{}^{93}{}_{}{}^{}\mathrm{beam}$ bombardment of thin ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$ targets were investigated at sub- and near-barrier energies using a magnetic spectrograph. Reaction products from three single-nucleon-transfer and seven multinucleon-transfer channels were observed. Multinucleon-transfer products were observed with a sharp onset only for those collisions with apsidal distances smaller than about 12.6 fm, while single-nucleon-transfer products were observed throughout the apsidal distance range studied. Average Q values of the multinucleon-transfer-reaction products are much more negative than the respective optimum values. These results suggest the formation of a neck at subbarrier energies.