Table of contents

A phenomenological model for heavy-ion potentials, equivalent to the double-folding model for large separations and to the liquid-drop model in the limit of spherical composite systems, is proposed. Applications of this model result in potential energies which have minima corresponding to surface contact of the nuclei. Results of numerical calculations are plotted for Pb-P, Pb-U and U-U interactions. The potential 'pockets' for deformed nuclei show a strong dependence on orientation.

The alpha -cluster structure in the mass distribution of the 75 MeV ¹⁶O+⁴⁰Ca reaction is shown to be given as collective mass transfer in the dynamical fragmentation theory.

The energy density of a non-interacting massive Bose field in lattice thermodynamics is considered. The deviations from the continuum limit due to both the finite volume of the system and pure lattice effects are studied. A considerable increase in the lattice corrections in the region of small (as compared with the field mass) temperatures is detected. The role of the latter in the estimate of the glueball mass obtained from lattice gauge thermodynamic data is pointed out.

The authors develop a method for diagonalisation of two- and three-body Hamiltonians which is algorithmically straightforward. The method is based on generalised coherent states associated with the symplectic group and on an elementary Monte-Carlo procedure for selecting important discrete sequences of such states. Detailed illustrations are given for the non-relativistic quark model of mesons and baryons using phenomenological power-law potentials. Generalisations to systems with many degrees of freedom appear feasible.

The energy dependence of pp to d pi is calculated for the Delta -resonance range (400<or approximately=T_p<or approximately=800 MeV) extending a preceding relativistic study at T_p=578 MeV. The leading graph is the exchange of a pion and a nucleon. Input are elastic pi N amplitudes (off shell) and relativistic pi NN and dpn vertex functions. Single-neutron exchange is added and distortion factors for the pp and pi d channels are applied. Only moderate sensitivity to variations of the input is found. Comparing with the existing body of data, good agreement is found for the total and differential cross sections. The relative spin observables are reproduced to within 10% of the possible range of variation. The remaining discrepancies can be traced to insufficient strength of pp spin-triplet channels.

Discusses relativistic corrections to the hadronic energy shifts in protonium. The main effect in the low-energy system was found to be due to a 2 pi -exchange potential, which modifies the medium-range behaviour of the NN interaction considerably. In view of the application to heavier antiprotonic atoms the author has checked the validity of the Born approximation for the hadronic interaction in various states of protonium.

A 2 pi -exchange (TPE) potential for pseudovector coupling of pions and nucleons is derived by transforming the Dirac equation into a Schrodinger-like form. The resulting TPE potential is spin dependent and attractive in all states of the NN and NN systems and describes part of the intermediate-range interaction. A comparison is made with the Hamada-Johnston potential and with the TPE potential obtained from different approaches.

The Pauli principle acting between quarks in different nucleons is expected to give rise to nuclear structure effects which have not yet been studied in detail. A general method of investigating the evolution of a many-quark system into colourless clusters with the quantum numbers of the nucleon is developed, and some results on the two-nucleon problem are presented.

The weight function in Lipkin's general expression (1958) for eliminating the centre-of-mass coordinate from nuclear wavefunctions has been approximated by a gaussian function exp(- lambda R²) with one parameter, lambda , to be determined by a variational calculation. This calculation has been carried out for the ground state of ⁶Li and the lowest energy has been obtained for a negative value of lambda . An explanation for this surprising result based on the cluster model is given. The result is also compared with other proposals in the literature for treating the centre-of-mass motion in nuclei.

The quasiclassical expression is given for the two-particle angular correlation function in compound-nucleus decay. In the second step of the cascade the excitation energy and angular momentum for the first daughter are replaced by their average values. While calculating these and the temperatures of the daughter nuclei, the rotational energy should not be small compared with the total excitation energy. The quasiclassical formula for the angular correlations is compared with quantum calculations and a good agreement is obtained with no fitting parameters.

The relation between the scattering wavefunction Psi (r₁) and the propagator K(r₁,t₁ mod p₀,t₀) is established for a short-range potential by means of the Moller operator. The semiclassical approximation to the propagator provides the usual asymptotic formula for Psi (r₁) where the scattering amplitude is substantiated by its semiclassical expression. An extension of this method to include a Coulomb potential provides similar results. The inelastic scattering case is then considered and the excitation wavefunction Psi _{beta alpha} (r₁) is expressed in terms of the reduced propagator K_{beta alpha} (r₁,t₁ mod p₀,t₀). An expression for the excitation cross section in terms of K_{beta alpha} (r₁,t₁ mod p₀, t₀) is finally obtained.

It is shown that some approximations implied in the optical limit of the Glauber theory are justified for low-energy heavy-ion surface collisions. The Glauber optical potential, with no free parameters, leads to reasonable predictions for both elastic and inelastic scattering in the ¹²C+¹²C system.

By regarding muon catalysis of nuclear fusion in a mixture of hydrogen isotopes as a series of stochastic processes. Markov chain theory is used to derive several exact analytic equations relating the rates of the various reactions and the sticking coefficients for the fusion channels. These include expressions for the mean number of pd, dd, dt, tt and pt fusion per muon, the mean total number of fusions per muon and the muon cycling rate lambda _c, which reduce to the corresponding well known expressions for catalysis in a deuterium-tritium mixture. Inclusion of the fusion reaction dd mu to p mu +t provides a particularly interesting complication, as this process gives rise to a catalysis cycle that may not return a free muon to the system. The application of Markov chain theory to more complex catalysis schemes, such as those including hyperfine states of the mesic atoms and mesic molecules, is considered briefly.

Using in-beam gamma -ray spectroscopy techniques experimental information on the presence of two-quasiparticle components in the band structures of ⁷⁸Kr has been derived. The observation of a second 10⁺ state decaying by a fast M1 transition of B(M1, 10₂⁺ to 10₁⁺)=0.8(4) Wu to the 10⁺ yrast level gives strong evidence for a band crossing between the collective ground-state band and a two-quasiparticle band. The residual interaction between these configurations has been estimated to be V(10⁺)=130+or-10 keV. The configuration mixing also provides an explanation for the decrease of the B(E2) values in the yrast sequence above the 8⁺ level.

The low-temperature orientation of ¹⁹³Os in an iron matrix and the Mossbauer effect of the 73 keV transition lead to mu (¹⁹³Os_GS)=+0.75(3) mu _N. The gamma-ray distribution coefficients combined with a quadrupole alignment measurement from the literature give Q(¹⁹³Os_GS)=+0.48(6)b. Several mixing parameters delta (E2/M1) in ¹⁹³Ir are also determined. The odd-mass Os nuclei are discussed in the light of mixing between ³/₂^-(512) and ¹/₂^-(510) Nilsson orbitals.