In pion-induced double charge exchange on ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$, a number of new discrete states, in addition to the ground state and the double isobaric analog state (DIAS), have been observed in the residual ${}_{}{}^{93}{}_{}{}^{}\mathrm{Tc}$ nucleus. Cross sections for the different states exhibit widely different energy dependence characteristics. In particular, the state just below the DIAS has a very different excitation function from the DIAS. In addition, the cross section of the giant resonance GDR⊗IAS has been measured at ${\mathit{T}}_{\mathrm{\pi }}$=230 and 294 MeV.

We have developed semiempirical total reaction cross section formulas for proton-nucleus (with ${\mathit{Z}}_{\mathit{t}}$≤26) and nucleus-nucleus (with ${\mathit{Z}}_{\mathit{p}}$ and ${\mathit{Z}}_{\mathit{t}}$≤26) reactions. These formulas apply for incident energies above ≊15 MeV and ≊100 MeV/nucleon, respectively. We have also constructed a procedure for calculating the projectile-fragment production cross sections, by scaling semiempirical proton-nucleus partial cross section systematics. The scaling is done by a scaling parameter, which is based on a Bradt-Peters-type law and also takes advantage of the weak-factorization property of projectile fragments. All products from the Z of the projectile down to Z=2 can be calculated. The agreement between the calculated partial cross sections and the experimental data is better than all earlier published results.

A time-ordered relativistic scattering theory for nucleons and mesons based on clusters rather than individual particles is derived. The S-matrix-type approach provides a recursive hierarchy of Lippmann-Schwinger equations, each describing the dynamical evolution of two-cluster configurations at different levels of the many-body problem. The presentation is restricted to a fixed number of particles; particle absorption and creation are treated in part II. The main concern here are the kinematic aspects of the problem. It is shown that the on-shell results of the formalism are covariant, without requiring negative-energy antiparticle contributions. This is achieved by constructing off-shell T matrices as invariants under a set of energy and momentum transformations which reduce to Lorentz transformations for on-shell energies. The present relativistic formulation is formally equivalent to a previously given nonrelativistic N-body approach.

At energies below the Coulomb barrier the fusion process can be described as the shadow of the Rutherford scattering, but at very low energies it is not valid. However, if we define an effective Coulomb potential, the fusion can be described as the shadow of the elastic scattering relative to this effective potential. Then light systems at very low energy show an anomalous behavior and the effective Coulomb potential is a way to describe it.

We investigate the decay of an excited nucleus in which several light particles are emitted sequentially from the parent. A recursion relation is derived which relates the mean-square momenta of the emitted light particles and the final residue. The calculation of the mean-square residue momentum (or mean energy) is sensitive to the order in which particles are evaporated, and this sensitivity is explored using simulated evaporation cascades. The possibility of using the analysis to distinguish between the sequential mechanism and a prompt multifragmentation mechanism is discussed, and an application of the method to charge partitions of calcium measured in the reaction ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$${+}^{\mathrm{nat}}$Cu at 35 MeV/nucleon with a multidetector is made.

An algorithm to scale nucleus-nucleus collision projectile-fragment cross sections from the corresponding proton-nucleus ones is developed. The algorithm takes advantage of the weak factorization property of projectile fragments. It uses the participant-spectator model and Glauber scattering theory and approximates the collision’s sum rules. The algorithm is sufficiently robust over the energy range 0.1–2.0 GeV/nucleon with no restrictions on the sizes of target (apart from the special case of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$) nor projectile nuclei. It offers marked improvement over our earlier semiempirical scaling procedure. Using measured and simulated cross sections for comparison, the estimated systematic uncertainty of the algorithm averaged over this energy range is ∼15%.

Strong-interaction effects have been observed in the x-ray spectra of atoms formed with ${\mathrm{\Sigma }}^{\mathrm{-}}$ hyperons in W and Pb. The spectra were analyzed for energy shifts and broadenings and for yield reductions of the final x-ray transitions before absorption of the ${\mathrm{\Sigma }}^{\mathrm{-}}$ by the nucleus. The results for the 10l→9k transitions of ${\mathrm{\Sigma }}^{\mathrm{-}}$ hyperonic atoms averaged over fine structure components are ${}_{}{}^{184}{}_{}{}^{}\mathrm{W}$: ɛ(9k)=214±60 eV, Γ(9k)=18±149 eV, Γ(10l)=2±2 eV; ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$: ɛ(9k)=422±56 eV, Γ(9k)=428±158 eV, Γ(10l)=17±3 eV, where the strong interaction shift ɛ=${\mathit{E}}_{\mathit{m}}$-${\mathit{E}}_{\mathit{c}}$, ${\mathit{E}}_{\mathit{m}}$ is the measured transition energy, and ${\mathit{E}}_{\mathit{c}}$ is the transition energy calculated assuming no strong interaction and Γ is the Lorentzian broadening. A four-parameter optical potential representing an effective spin-independent ${\mathrm{\Sigma }}^{\mathrm{-}}$-nuclear hadronic interaction was fitted by these results in combination with previous data from lower-Z nuclei.

The tensor part of the color hyperfine interaction between quarks leads to a small electric quadrupole amplitude in the γN⇆Δ excitation. It is demonstrated that pion photoproduction data available previously have a low sensitivity to the (isospin 3/2) electric quadrupole amplitude, ${\mathit{E}}_{1+}$(3/2). An additional difficulty is that there is an appreciable background contribution to the total ${\mathit{E}}_{1+}$ amplitude. The consequent difficulties in extracting the resonant part of this small amplitude from experiment are discussed. It is shown that γp→${\mathrm{\pi }}^0$p and γp→${\mathrm{\pi }}^{+}$n cross sections near 0° and 180°, and also those near 90° with polarized γ rays, both with and without polarized targets, have the greatest sensitivity to the ${\mathit{E}}_{1+}$(3/2) amplitude. Since the anticipated observable effects of the resonant E2 amplitude are expected to be ∼10% to 20% in magnitude, the required accuracy to extract a precise E2/M1 ratio is ∼1% for both experiment and theory.

Singular integral equations for quarkonium (qq¯) spectra are solved in momentum space for relativistic confinement plus Coulomb potentials including spin. The confinement potential in momentum space is defined using an analytical regularization scheme. Further manipulations give rise to integro-differential equations and we obtain analytical approximations for the remaining singular integrals. The procedure is tested with two different reductions of the Bethe-Salpeter equation. Using both scalar and scalar plus pseudoscalar confinement we obtain the spectra of charmonium, b-quarkonium, and the light mesons. We compare the results with experiment and with results obtained by other techniques. Eigenfunctions for selected eigenstates are presented. A good description of both the light and heavy mesons is then obtained with scalar linear confinement in the instantaneous approximation to the Bethe-Salpeter equation. This description is based upon the inclusion of a Breit term to approximate transverse gluon effects.

We have assigned γ-ray transitions to ${}_{}{}^{136}{}_{}{}^{}\mathrm{Te}$ by examining the prompt gamma radiation following spontaneous fission of ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cm}$. The transitions were identified in spectra gated on the Ru complementary fragments, and confirmed by studying prompt γ rays following spontaneous fission of ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$. The results are examined in terms of the systematics of other tellurium and N=84 nuclei.

The ${\mathit{K}}_{\mathrm{\alpha }}$-x-ray yields associated with the superdeformed and normal-deformed bands in ${}_{}{}^{193}{}_{}{}^{}\mathrm{Hg}$ have been measured. The results indicate an excess yield of ${\mathit{K}}_{\mathrm{\alpha }}$-x rays in coincidence with the superdeformed cascade relative to that in coincidence with the normal-deformed cascade. The internal conversion of known transitions along the superdeformed cascade cannot account for the observed ${\mathit{K}}_{\mathrm{\alpha }}$-x-ray yield. It is likely that this excess x-ray yield is associated with low-energy interband-M1 transitions competing with the low-spin superdeformed-E2 transitions.

Calculations based on the rotational liquid-drop model including the nuclear proximity energy and using a family of compact and creviced shapes predict the existence of hyperdeformed prolate states of β∼0.9 in a spin range of about (70–110)ħ for ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$. These results are in good agreement with the recent observations at the Chalk River Laboratories of hyperdeformed shapes in ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$ using p-γ-γ coincidence techniques. Such hyperdeformed states are predicted in the whole Periodic Table but for different spin regions.

A shell model description of the 3/$2^{+}$ resonance is given to show that the main features of the experimental observations can be described by this model as well as by the resonating group model.

We have previously used a cluster model, employing a square well nuclear potential plus a surface charge Coulomb potential, in a consistent description of alpha and exotic decay of heavy nuclei. A novel feature of these analyses was the use of a constant depth of the nuclear potential, with the radius appropriate to a particular decay determined by fitting the decay Q value. For alpha decay, the treatment was subsequently generalized using a diffuse well geometry for the nuclear potential, as well as a more realistic form for the Coulomb potential. Here we make a similar generalization for exotic decay, and find several families of parameter values which give a good description of the data. The parameter values of one of these families correspond closely with those which give the best fit to the alpha decay data.

Fission fragment angular distributions have been measured for the reactions of ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$${+}^{238}$U and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{237}$Np at near- and sub-barrier energies. It is found that the experimental values of the fragment anisotropy are larger than the expected ones of the saddle point transition state model. Comments on fission before full K equilibration are made on the basis of our experimental results.

Apparent discrepancies between values of extra-push energies for fusion of two heavy nuclei derived through measurements of fusion evaporation residue cross sections and of differential fission cross sections have been reported by Keller et al. We show here that with the inclusion of the recently proposed preequilibrium fission decay channel in the analysis, there is no inconsistency between the two sets of data in terms of the deduced extra-push energies.

The ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$(p,p’) continuum data at ${\mathit{E}}_{\mathit{p}}$=65 MeV were reanalyzed in the framework of the distorted-wave impulse approximation and the distorted-wave Born approximation. This provides an analysis consistent with the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$(α,α’) work at ${\mathit{E}}_{\mathrm{\alpha }}$=50 MeV and reconfirms an earlier observation that the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ target breakup data, studied at low relative fragment energies, indicate a change in the reaction mechanism below a critical transfer of momentum. This is possibly due to the recombination of the breakup fragments, an effect which should be seriously considered in the analysis of all the breakup reaction data measured at low relative fragment energies.

Elastic differential cross sections of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ on a proton target recently observed at ${\mathit{E}}_{\mathrm{lab}}$/A=62 MeV are analyzed in a ${(}^9$Li+n+n)-p four-body model to take the halo structure of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ into consideration. The eikonal and adiabatic approximations are employed to derive the optical potential that includes the breakup effect of halo neutrons to continuum states. It is shown that both the breakup of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ and the exchange force of the n-p interaction lead to the reduced cross sections that are in satisfactory agreement with experiment with no adjustable parameters.

The strength of the final-state interactions between emitted particles depends on the spectrum of time delays between their emissions. Measured correlation functions reflect these interactions, and therefore time-scale information can be obtained by comparisons to associated reaction simulation calculations. We illustrate the sensitivity of the method to the emitter lifetime as well as the attention to several of the details needed for its effective use. Application to one set of data is shown.

There exists a basic uncertainty in the extraction method of ${\mathit{K}}^{+}$-nucleus total cross sections with the usual transmission experimental data. Although the errors are very small for light nuclei, they amount to about 10% for medium and heavy nuclei. When nontraditional effects of ${\mathit{K}}^{+}$-nucleon interactions within the nucleus, such as swelling of nucleon, are investigated, only the total cross sections on light nuclei should be used in order to avoid this uncertainty.