[en] This book presents papers on coincident particle emission from continuum states in nuclei. Topics covered include the following: the role of quasifree interactions in medium energy (p, 2p) reactions, evidence for d-d-d linear chain multi-cluster state; theoretical investigations of heavy-ion induced reactions; and experimental studies on projectile fragmentation

[en] Studies of the continuous energy spectra of alpha particles in the so called deep inelastic region are of special interest. Scattering of alpha particles of energies exceeding 100 meV was proved to be an excellent tool for investigation of giant isoscalar resonances in nuclei. These are usually embedded in the continuous part of the spectrum so that the extraction of a useful spectroscopic information depends strongly on the knowledge of the mechanism leading to the underlying physical background. Several models describing the shape and the angular dependence of single spectra of inelastically scattered alpha particles have been put forward. These can be classified in two groups. The microscopic models like multistep DWBA quasi free scattering (QFS) preequilibrium or exciton coalescence and macroscopic ones like moving source or drifting hot spot models. Each of these models describe only certain features of the measured cross sections usually in a rather limited energy range

[en] Recently the investigation of photonuclear reactions in the medium energy range has received new attention. Photoproduction of pions on complex nuclei can give information on the nuclear structure and on the interaction of pions with nuclear matter. Since the main production mechanism is the excitation of a nucleon to a Δ-isobar, one can also study the γNΔ vertex and the ΔN-interaction

[en] A correction to nuclear structure calculations due to the finite lifetime of the excited states of a finite nucleus is investigated. An additional term to the Hamilton operator as well as to the wave function of a nuclear state is shown to appear. The analytical expressions are given and results of numerical calculations are discussed. The additional term to the Hamilton operator determines the lifetime of the decaying nuclear states. It violates charge symmetry of the nuclear forces. Its nondiagonal matrix elements describe the external mixing of the states via the continuum by which the properties of overlapping resonances are governed. Long-lived and short-lived states are described in a unified manner. The interplay between giant resonances and underlying levels is studied. The basic assumptions of the statistical theories of compound nucleus resonances are discussed on the basis of numerical results obtained by taking into account the external mixing in a straightforward manner. The additional term to the wave function of a nuclear state describes virtual particles including clusters in the nuclear surface. It plays a role in most nuclear reactions

[en] In a previous study, the authors showed that the emission models used in the analysis of preequilibrium particles from light-ion reactions could be successfully applied, with appropriate modification, to the analysis of particles emitted from a nucleus-nucleus collision in an early stage of the reaction process. For that purpose, they used (a) the first term of the Griffin exciton model expansion and the Harp-Miller-Berne equilibration model in a modified form. Having established the feasibility of such analysis, the authors concentrate on its physical information content, and discuss in particular the significance of the relevant parameters that enter in the analysis, namely the initial number of degrees of freedom that share the available energy and the total time of preequilibrium emission

[en] The (p,2p) reaction is inherently associated with coincident particle emission from continuum states of nuclei. Historically, (p,2p) reactions were among the first tools used which coincident techniques to study the properties of nuclei. The hope was to use such reactions to provide information about hole states of nuclei. Early exploratory studies demonstrated that hole states could be identified with coincident techniques and suggested that the distribution of events in phase space could be related to the momentum wave function of the struck nucleon. A later study laid the theoretical foundation for understanding that the quasifree mechanism involved in medium energy (p,2p) reactions. That work suggested that distortions play an important role and that it may not be possible to obtain useful information from single plane wave analyses. Early studies of (p,2p) reactions were severely limited by the computers and computational techniques available. Considerable progress in the understanding of such reactions was made when realistic distorted wave impulse approximation (DWIA) calculations became possible with codes. The possibility of using on-line computers for data accumulation and analyses in connection with detectors capable of observing a broad energy range for both emitted particles, made it possible to study the properties of such reactions over wide regions of the available multi-body phase space. These comprehensive data provided further insight and helped to develop a more complete picture of the interaction of the nucleon with nuclei

[en] A comprehensive model for α induced reactions, that was recently proposed and successfully applied to the analysis of excitation functions of reactions induced on A --60 and A --90 nuclei and of inclusive spectra of particles emitted in these reactions, has been improved to predict the decay of continuum states excited in inelastic α scattering. The model, the A dependence of the model parameters, and the comparison of its predictions with neutron spectra from the decay of continuum states in (α, α') reactions are discussed

[en] A dynamical theory of partial fusion reactions is presented, which may fill the gap between direct and compound nuclear reaction theories. With the new theory one can calculate partial fusion taking place in three-body (and many more) channels reached via direct reactions, e.g., breakup and knockout reactions. The authors present first the results for the cross section for such reactions, taking as an example breakup followed by fusion. They then discuss a physical picture which emerges from their theory, namely that the partial fusion reactions, particularly of the massive-transfer type, take place in a so-called deep peripheral region. It is also shown that the deep peripheral character of such processes diminishes as the mass of the fused system decreases, so that the reactions essentially evolve to the usual peripheral character. Finally, comparisons are made of results of numerical calculations with experimental data, taking as an example the /sup 159/Tb(/sup 14/N,α) reaction with E/sub lab/ = 95 MeV

[en] In the last decade an increasing number of particle-particle coincidence measurements have been carried out with light- and heavy-ion beams to investigate the reaction mechanisms leading to the continuum structures in inclusive particle spectra. The inclusive particle spectra obtained with light- or heavy ions show, at forward angles and at incident energies of 10 MeV/amu or higher, a great resemblance: a more or less exponential part peaking at roughly the energy of the target Coulomb barrier (tail) and a bump at energies corresponding to approximately beam velocity. The basic topic of this paper therefore is ''are there essential differences between the mechanisms in light- and heavy-ion induced reactions and does the investigation via p-p correlations help to answer this question?''

[en] The authors report on an investigation of the /sup 28/Si(α,tp) reaction to identify the various processes leading to the continuum part of the inclusive (α,t) spectrum, to determine their contribution to the inclusive triton yield and to find out to what extent α and /sup 3/He projectile breakup differ. Such effects can originate from the large difference in binding energy and/or from the absence of well defined excited states in /sup 3/He, whereas several excited states are known in /sup 4/He, whereas several excited states are known in /sup 4/He. The authors show that α-breakup shows a process which is absent in the corresponding /sup 3/He breakup reactions