Table of contents

Different convergence properties of the Sturm-Liouville expansion are investigated with particular attention to the case of states which satisfy Schrödinger-like equations with a fixed energy and different depths of a potential, particularly of the Woods-Saxon shape used in nuclear physics.

Different convergence properties of the Sturm-Liouville expansion are investigated with particular attention to the case of states which satisfy Schrödinger-like equations with a fixed energy and different depths of a potential, particularly of the Woods-Saxon shape used in nuclear physics.

From proton-nucleus emulsion data for 67, 200, 300, and 400 GeV we make an attempt to extract the leading baryon pseudorapidity distribution. The results indicate that the inelasticity in proton-nucleus collisions is much larger than in proton-proton interactions. Our result is consistent with an approximately equal probability for the leading baryon to be either a proton or a neutron and with the property that the π-meson distribution in the projectile fragmentation region is unaffected by the nuclear parameters.

Available pion-induced spallation cross-section data have been compiled and analysed with the Rudstam five-parameter formulae. The energy and mass dependence of the parameters are discussed. Comparison with parameter values obtained for proton- and photon-induced spallation data is made. The average number of nucleons and charged particles emitted are compared to results from Monte Carlo cascade-evaporation calculations. With parameter values determined the CDMD formula can be used to estimate unknown pion-induced spallation cross sections.

The determination of the inherent quadrupole moments of the even uranium isotopes 234, 236, 238, based on Optical Relative Isotope shift measurements, was effectuated. These values are in fair agreement with the values of the quadrupole moments deduced from nuclear electric-quadrupole transition probabilities.

Spectroscopic observations of a theta-pinch plasma are analysed, resulting in the classification of nearly 200 spectral lines of ArV to ArX. The ArIX data are of particular interest as the observed lines mainly belong to the 2p⁵3d-2p⁵4f, 5f, 6f, and 2p⁵3p-2p⁵4d, 5d, 4s, 5s and 2p⁵3s-2p⁵4p transition arrays, for which no information previously existed. 80 new ArIX energy levels are established. Theoretical calculations of atomic energy levels and oscillator strengths aided the identification of spectral lines.

In view of the lack of experimental and theoretical values of electric quadrupole oscillator strengths for sodium-like ions, we have proceeded to calculate Hartree-Fock gf-values along the sequence (11 ⩽ Z ⩽ 26; nl²L-n'l'²L' transitions with (3 ⩽ n, n' ⩽ 8; 0 ⩽ l, l' ⩽ 3). All the calculations were performed using the first two forms of the off-diagonal hypervirial theorem. The agreement between the two forms is very good for all the transitions considered.

The behaviour of the oscillator strengths was studied along the sequence by the Z-expansion method as for electric dipole transitions. As an extension of the "continued screening approximation" developed by Froese Fischer (1976) in the dipole case, it is shown that the transition integral can be represented accurately by the expression

I₀ being the hydrogenic value and s_i (i = 1,...,4), being parameters.

Data on the reactions pn → NπΔ(1236) and pp → NπΔ(1236) at 19 GeV/c have been used to study the reactions pN → N(πΔ) and pN → (Nπ)Δ in terms of crossed channel isospin amplitudes. The cross section of the reaction pN → N(πΔ) is about twice that of pN → (Nπ)Δ. Each reaction can be described by three amplitudes M_I^Ix, where I_x and I are the isospins of the exchange and of the Δπ or Nπ system, respectively. We find that for the reaction where the pion clusters to the Δ, i.e., pN → N(πΔ), the isoscalar exchange is the leading mechanism, but the M_3/2¹ amplitude also gives a large contribution. For the other reaction, i.e., pN → (Nπ)Δ, the isovector exchange amplitude leading to a I = 3/2 Nπ state, is dominating. The I_x = 2 exchange amplitude is unimportant. These results have been compared with the results of similar analyses of other three-body reactions and some common features and differences have been pointed out.

Available data at other energies have been used to investigate the energy dependence of the isospin amplitudes for the reaction pN → ΔπN in a double exchange representation. It is found that the amplitude involving isoscalar exchange is dominating above 20 GeV/c and has a weak energy dependence while the amplitude with double isovector exchange has an energy dependence pⁿ_lab with n ≈ - 1.5.

An interpretation of the heat flux limiting factor when ions are significantly non-Maxwellian due to collisionless damping of ion sound on ions is presented in the approximation of a two-temperature ion component description.

A stationary distribution of collisional ions and collisionless electrons in a plasma density step region has been found and the heat flux through the step evaluated. The diode behaviour of the step as a "heat conductor" has been shown.

We investigate parametric instabilities in a bounded inhomogeneous plasma when the pump wave frequency is close to that of the Gould-Trivelpiece mode. Using a suitable technique, we have obtained a dispersion relation in a radially inhomogeneous plasma column. The growth rates and threshold conditions for purely growing and four-phonon parametric instabilities are calculated. A comparison of these values with those for a homogeneous plasma shows that the plasma inhomogeneity enhances thresholds.

Raman spectra of NiSiF₆·6H₂O have been measured between 300 and 10 K. The Raman band due to vibrations of the water molecules in the solid shows an exponential variation of the half-width with temperature which is interpreted as due to thermally activated re-orientation of the water. This activation energy is significantly lower than the barrier height to water re-orientation measured by dielectric relaxation and we interpret the activation energy as the energy of the first excited vibrational level of the water.