Excitation functions were measured for the ${}_{}{}^{46}{}_{}{}^{}\mathrm{Ti}$(n,p${)}^{46}$${\mathrm{Sc}}^{\mathit{m}}$ and ${}_{}{}^{46}{}_{}{}^{}\mathrm{Ti}$(n,p${)}^{46}$${\mathrm{Sc}}^{\mathit{m}+\mathit{g}}$ reactions over the neutron energy range of 5.4 to 10.5 MeV. Use was made of the activation technique in combination with high-resolution γ-ray spectroscopy. From the available experimental data isomeric cross-section ratios [${\mathrm{\sigma }}_{\mathit{m}}$/(${\mathrm{\sigma }}_{\mathit{m}}$+${\mathrm{\sigma }}_{\mathit{g}}$)] were determined. Statistical-model calculations taking into account precompound effects were performed for fast neutron-induced reactions on ${}_{}{}^{46}{}_{}{}^{}\mathrm{Ti}$. The calculational results agree well with the experimental data on emitted proton spectra as well as on the excitation functions of various reaction channels. The calculated cross section for the formation of the isomeric state (${\mathrm{\sigma }}_{\mathit{m}}$) is strongly dependent on the input level scheme of the product nucleus; the same effect is reflected in the calculation of the isomeric cross-section ratio.

Radiochemical yield measurements are reported for barium isotopes from ${}_{}{}^{133}{}_{}{}^{}\mathrm{Cs}$(γ,${\mathrm{\pi }}^{\mathrm{-}}$xn${)}^{133\mathrm{-}\mathit{x}}$Ba for x=0, 2, 4, 5, 6, 7, and 9 for bremsstrahlung maximum end-point energies ${\mathit{E}}_0$=30–1050 MeV and for ${}_{}{}^{133}{}_{}{}^{}\mathrm{Xe}$ from ${}_{}{}^{133}{}_{}{}^{}\mathrm{Cs}$(γ,${\mathrm{\pi }}^{+}$${)}^{133\mathit{m},}$gXe for ${\mathit{E}}_0$=300–1000 MeV. Emphasis was placed on Ba measurements near the pion threshold and for different target thicknesses in order to assess interfering secondary particle-induced reactions. Clear evidence of secondary reactions was found in the form of a shoulder in the yield curves for a range of values near ${\mathit{E}}_0$≲${\mathit{Q}}_{\mathrm{\pi }}^{\mathrm{-}}$, the ${\mathit{Q}}_{\mathrm{\pi }}^{\mathrm{-}}$ value of ${}_{}{}^{133}{}_{}{}^{}\mathrm{Cs}$(γ,${\mathrm{\pi }}^{\mathrm{-}}$xn) reaction. This result was used for the correction of yields at ${\mathit{E}}_0$≳${\mathit{Q}}_{\mathrm{\pi }}^{\mathrm{-}}$ with the aid of reported measurements of photoproton spectra from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and other complex nuclei and cross sections of ${(}^{133}$Cs+p) reactions. The yields corrected for the secondaries ${\mathrm{\sigma }}_{\mathit{q}}$(${\mathit{E}}_0$) were unfolded into cross sections per photon of energy k, σ(k). The characteristic features of ${\mathrm{\sigma }}_{\mathit{q}}$(${\mathit{E}}_0$) and σ(k) are then discussed in terms of ${\mathit{E}}_0$ and k dependences and product mass (${\mathit{A}}_{\mathit{p}}$=133-x) by comparing the present results with those for other systems currently obtained by our group. It was found that the present results of σ(k) are generally reproduced by a cascade-evaporation calculation based on the pica code of Gabriel and Alsmiller, only if the calculated values are shifted up in photon energy by 30 MeV and the neutron cutoff energy is chosen to be 1 MeV.

Measurements of the electrodisintegration cross sections, (e,p) and (e,2p), and their corresponding electrodisintegration-plus-photodisintegration yields for ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ and ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$ are presented. The experiment covers the range from 20 to 60 MeV electron incident energies. The experimental results were analyzed using E1 and E2 distorted-wave Born approximation virtual photon spectra for a finite nucleus in order to obtain the corresponding photodisintegration cross sections for both channels and isotopes. For ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ the integrated (γ,p) cross sections is 47% bigger than (γ,n) while for ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$ they are of the same order of magnitude. For both isotopes the (γ,p) decay channel is dominantly E1. The (γ,2p) channel is much smaller than the (γ,2n) channel but the E2 contribution to this decay mode is of the same magnitude of the E1.

The phenomena of backward proton emission and subthreshold antiproton production in the proton-nucleus interactions, and findings from the inclusive scattering of electrons from nuclei, are interpreted in terms of multiparticle interactions. Rates for multiparticle collisions are calculated using the results from many-body theory, with the products of the squared interaction amplitudes and Wigner functions. The rates for the processes with different number of particles are proportional to the different powers of spatial density. The many-body amplitudes are expanded in terms of propagators and elementary amplitudes with only two particles in the initial state. The leading processes are isolated on a tree level. They correspond to the expansion of a ground-state nuclear wave function. Reasonable agreement with data is obtained.

We discuss the consequences of energy and angular momentum conservation for nucleon-nucleon scattering in a nuclear environment during high-energy heavy-ion collisions. We describe algorithms that ensure stricter enforcement of such conservation laws within popular microscopic models of intermediate-energy heavy-ion collisions. We find that the net effects on global observables are small.

A simple parametrization of nuclear reaction cross sections in terms of resonance parameters is obtained from the expansion of a modified scrK matrix. The latter is defined in such a way that it has no other singularity in the complex energy plane than its poles. When expanded in terms of these poles, it can be used to analyze and parametrize low-energy data on resonance reactions. The pole energies ${\mathit{E}}_{\lambda }$ are the resonance energies without shift (except when there is a nearby threshold of a closed neutron channel), and the residues are the products of reduced width amplitudes ${\mathit{g}}_{\mathit{c}\lambda }$. These two sets of parameters (${\mathit{E}}_{\lambda }$,${\mathit{g}}_{\mathit{c}\lambda }$) are independent of the channel radii and no boundary condition constants are involved in their definitions. Also, few-level approximations of the expanded scrK matrix retain the unitarity of the S matrix. These properties add more reliability to the extrapolation of data to lower energies, as often necessary for reactions of astrophysical interest.

Elastic and inelastic observables for the scattering of 500 MeV protons from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ are calculated using either the first-order relativistic or nonrelativistic impulse approximation for the diagonal potentials and a collective model for the transition potentials. The calculations are done using either Dirac or Schrödinger coupled channel programs. The relativistic approach reproduces the inelastic observables better than the first-order nonrelativistic impulse approximation model.

We present here the first systematic and global analysis of nucleon-induced reactions on A<30 systems at incident energies of 50 MeV to 1 GeV by means of a cascade-statistical approach. Model simulations are tested against available data from nuclei such as C, N, O, Al, and Si. With one set of inputs provided here, most of the inclusive observables, such as the double differential spectra of light ions and heavy residual nuclei from the dominant channels, can be well reproduced. The model yields absolute cross sections and the calculations are done without any parameter adjustments. Given the success of this simple, classical approach, we reexamine the model in terms of the essential physics such as Pauli principle, Fermi motion, and medium corrections. We interpret the cascade part as a classical simulation of the intermediate multi-particle-hole configurations which dominate multistep-direct and preequilibrium reactions and provide a critical assessment of the microscopic foundation and the range of validity of the model. We also discuss possible extensions of this model to around Fermi energy.

We test the validity of calculating the process NN→πd in lowest order, with initial- and final-state interactions being included via square roots of s matrices for the respective elastic processes (so-called Sopkovich approximation). This is done by constructing a coupled-channels model with effective two-body potentials between the channels NN, πd, and NΔ. These potentials are taken to be separable, and are fitted to partial-wave amplitudes coming from a three-body calculation. We obtain reasonable fits in those partial waves where coupling to the NΔ channel is strongest; in particular, the dominant J=$2^{+}$ channel is well described. Within such a two-body potential model, it is known that the Sopkovich approximation should be valid for small, short-range transition potentials in the limit of high energies. Using this coupled-channels model, we find that the Sopkovich approximation in the $2^{+}$ channel works well only above 200-MeV total center-of-mass kinetic energy. Comparison with an approximation which assumes only a small transition potential leads us to observe that (i) the $2^{+}$ NN→πd transition potential is indeed small everywhere except at the Δ resonance peak (160 MeV), and (ii) away from this peak, the Sopkovich approximation breaks down below 200 MeV mainly due to the neglect of off-shell effects. For the smaller J=$2^{\mathrm{-}}$, $3^{\mathrm{-}}$, and $4^{+}$ partial waves, we find the Sopkovich approximation to work at least as well as for the $2^{+}$. No conclusions are made about the J=$0^{+}$ and $1^{\mathrm{-}}$ partial waves; these obtain large contributions from s-state πN rescattering which is not easily included in our model.

An elementary simple model for nuclear molecules is used to describe the molecular spectrum of the ${}_{}{}^{12}{}_{}{}^{}\mathrm{-}_{}^{12}{}_{}{}^{}$C system. Through that model the molecular potential is determined. Without further parameters the total fusion cross section around and below the barrier is calculated with good results indicating a correlation between the molecular spectrum and fusion. It is concluded that nuclear molecules may possibly be the doorway states for fusion. The simplicity of the model used allows a deeper schematic insight of the mechanism of fusion.

We consider (d,p) and (d,n) reactions on light nuclei at low energies. A simple estimate using the second-order distorted-wave Born approximation shows that Coulomb-induced predissociation of the deuteron influences the relative rate by less than 10%. This disagrees with a previous explanation of experiments involving ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ targets and invalidates speculations about such effects in ‘‘cold fusion’’ experiments.

The spin dependence of the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$${(}^2$H,γ${)}^6$Li capture reaction is studied in a deuteron-alpha-particle direct capture model. Nucleon-nucleon tensor interaction effects, manifest through the deuteron and ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ internal D states and through the deuteron-alpha-particle tensor interaction, are included within the d+α cluster model. The entrance channel tensor force, calculated from the folding model, is shown to produce relatively minor effects on the calculated reaction tensor analyzing powers compared to those of the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ D state for center-of-mass energies of proposed experiments (≊10 MeV).

The multistep compound formalism of Feshbach, Kerman, and Koonin has been extended to include γ-ray emission. By allowing the first few simple preequilibrium bound states to decay via electromagnetic transitions rather than particle emission, the large number of high-energy γ rays observed in the experimental data can be understood. It is assumed that single-particle and -hole transitions lead to the emission of γ rays, and radial matrix elements for such transitions are estimated by exploiting the inverse process, photoabsorption. Reactions of 14-MeV neutrons with ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$, ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$, and ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ are analyzed and it is found that between 20% and 50% of cross sections for high-energy γ-ray emission can be accounted for by the multistep compound mechanism.

We evaluate the contribution of quasifree nucleon knockout and of inelastic lepton-nucleon scattering in inclusive electron-deuteron reactions at large momentum transfer. We examine the degree of quantitative agreement with deuteron wave functions from the Reid soft-core and Bonn realistic nucleon-nucleon interactions. For the range of data available there is strong sensitivity to the tensor correlations which are distinctively different in these two deuteron models. At this stage of the analyses the Reid soft-core wave function provides a reasonable description of the data while the Bonn wave function does not. We then include a six-quark cluster component whose relative contribution is based on an overlap criterion and obtain a good description of all the data with both interactions. The critical separation at which overlap occurs (formation of six-quark clusters) is taken to be 1.0 fm and the six-quark cluster probability is 4.7% for Reid and 5.4% for Bonn. As a consequence the quark cluster model with either Reid or Bonn wave function describe the SLAC inclusive electron-deuteron scattering data equally well. We then show how additional data would be decisive in resolving which model is ultimately more correct.

A covariant formulation of the multiple scattering series for the optical potential is presented. We consider the case of a scalar ‘‘nucleon’’ interacting with a spin zero isospin zero A-body target through meson exchange. We show that a covariant equation for the projectile-target t matrix can be obtained that sums the ladder and crossed ladder diagrams efficiently. From this equation, a multiple scattering series for the optical potential is derived, and we show that in the impulse approximation, the two-body t matrix associated with the first-order optical potential is the one in which one particle is kept on mass shell. The meaning of various terms in the multiple scattering series is given and we describe how to construct the first-order optical potential for elastic scattering calculations.

A detailed calculation of the capture rate for ${\mathrm{\mu }}^{\mathrm{-}}$+d→${\nu }_{\mathrm{\mu }}$+n+n is carried out and the result compared with the latest data. Within the same framework we also calculate the cross sections of ν+d and ν¯+d reactions for incident energies ${\mathit{E}}_{\nu }$≤170 MeV in view of the importance of these cross sections for studying astrophysical neutrinos with the use of a heavy-water Čerenkov counter.

Previous theoretical work has shown that parity and time-reversal symmetry can be tested with particularly high sensitivity in the domain of isolated compound-nucleus resonances. In this domain, experiments will naturally focus on individual resonances rather than on the background cross section. The theoretical analysis of this situation leads to the concept of an ensemble of ‘‘on-resonance’’ measurements. This concept naturally emerges by combining two previous theoretical approaches to tests of fundamental symmetries. We investigate the properties of this new ensemble and show how to convert ‘‘on-resonance’’ data into statistically significant information on symmetry violation.

A new experimental method has been implemented for precise measurements of neutron capture cross sections in the energy range from 3 to 200 keV. Neutrons are produced via the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$(p,n${)}^7$Be reaction using a pulsed 3-MV Van de Graaff accelerator. The neutron energy is determined by the time-of-flight (TOF) technique using flight paths of less than 1 m. Capture events are detected with a 4π barium fluoride detector. This detector is characterized by a resolution in gamma-ray energy of 14% at 662 keV and 7% at 2.5 MeV, a time resolution of 500 ps, and a peak efficiency of 90% at 1 MeV. Capture events are registered with ∼95% probability above a gamma-ray threshold of 2.5 MeV. The combined effect of the relatively short primary flight path, the 10-cm inner radius of the detector sphere, and of the low capture cross section of ${\mathrm{BaF}}_2$ shifts the background due to capture of sample scattered neutrons in the scintillator to later TOF and therefore leaves the high-energy portion of the TOF spectrum undisturbed. The high efficiency and good energy resolution for capture gamma-rays yields a further reduction of this background by using only the relevant energy channels for data evaluation. In the first measurements with the new detector, the neutron capture cross sections of ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$, ${}_{}{}^{103}{}_{}{}^{}\mathrm{Rh}$, and ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ were determined in the energy range from 3 to 200 keV relative to gold as a standard. The cross-section ratios could be determined with overall systematic uncertainties of 0.7 to 0.8%; statistical uncertainties were less than 1% in the energy range from 20 to 100 keV, if the data are combined in 20-keV wide bins. This represents an improvement of factors 5–10 compared to existing experimental methods. The necessary sample masses were of the order of one gram. Maxwellian averaged capture cross sections were calculated in the temperature range relevant for s-process studies. Severe discrepancies were found compared to the data reported in literature.

A recent experiment has measured analyzing powers in d(p→,${\mathrm{\pi }}^{\mathrm{-}}$pp)p in a geometry which selected the quasifree two-body reaction p→n→${\mathrm{\pi }}^{\mathrm{-}}$pp${(}^1$${\mathit{S}}_0$). Analysis of the results indicated a significant contribution from a very-short-range part of the nucleon-nucleon interaction. We show that the analyzing power data measured in the above experiment is reasonably well described by a unitary NN → NNπ model containing only the one-pion-exchange driving force.

We have measured the production cross sections for 59 target fragments from the interaction of 13.3 GeV/nucleon ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ with ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$. We have deduced fragment mass-yield distributions from these data. The cross sections are consistent with limiting fragmentation (within ±20%). The electromagnetic dissociation cross section for the one-neutron removal process is in agreement with expectations although a large two-neutron removal cross section was observed.