Table of contents

New closed-form formulae for the discrete eigenvalues of the classical homogeneous one-speed transport equation (in the case of plane symmetry), a fundamental equation in linear transport theory with a particular importance in neutron diffusion and transport with regeneration, are derived. A very simple method, based on the Cauchy theorem in the theory of analytic functions, is used for the derivation of these formulae. Finally, two more physical applications of the same formulae are reported.

Some results on pseudorapidity distributions and rapidity-gap distributions of shower particles produced in pion-nucleus and proton-nucleus collisions at 50 and 400 GeV are presented and discussed. Study of the rapidity distributions reveals that the projectile fragmentation is mass independent and the target fragmentation depends upon the target mass. From the rapidity-gap distributions, we find an evidence for short-range correlations which indicates that the secondary particles are produced via cluster formation and the contribution of the long-range correlations is quite small.

Some selection rules and relations between cross sections of direct reactions, implied by SU(4) symmetry are discussed. Special cases with projectiles belonging to one supermultiplet are investigated.

Spectra emitted from laser-produced plasmas of scandium, titanium, vanadium and chromium have been recorded in the region 270-600 Å, and lines belonging to the 3s-3p and 3p-3d transition arrays in neonlike ions have been identified. The 2p⁵3s, 3p and 3d energy levels have been derived from the observations for Ti XIII and from solar flare lines for Fe XVII. Hartree-Fock calculations and parametric fits have yielded scaling factors for ab initio energy integrals that make it possible to predicts 3s-3p and 3p-3d wavelengths. Observed and predicted wavelengths for the strongest lines in Sc XII, V XIV, Cr XV and Ni XIX are presented.

The pure electric quadrupole transition λ = 587.0 nm between the ³P₂ and ¹S₀ levels of the ground configuration of Bi II was observed for the first time and the interferometric study of its hyperfine structure has been performed. A comparison between experimental and theoretical relative intensities of the hfs components of the multipole transitions λ = 485.0 nm, λ = 587.0 nm, and λ = 591.3 nm is made.

The structures of the 3s²3p²P⁰ ground state and of a number of excited states for aluminum and ions along the isoelectronic sequence up to Ca VIII have been calculated in the Multiconfiguration Optimized Potential Model. The excited states include the following: 3s²3d²D, 3s²4s²S, 3s3p²²D, ²S, as well as 3s²4p, 3p³ and 3s3p(³P⁰)3d²P⁰. There is strong configuration mixing in the spectroscopic terms but on the basis of our calculations we recommend a different designation from that currently adopted for the 3p³ and 3s3p(³P⁰)3d²P⁰ terms. Oscillator strengths for transitions among these terms have been calculated in the length and velocity formulation with particular emphasis on accurate description in the vicinity of term crossings. Comparison is made with other theory and with experiment where results are available. At present, the experimental data are inadequate to verify the many calculated structures in the isoelectronic gf dependence.

Observed level intervals within and between the configurations 2s² 2p³, 2s2p⁴ and 2p⁵ of the nitrogen sequence are compared with the corresponding theoretical values derived from the tables of Cheng, Kim and Desclaux. The differences are expressed by suitable functions of Z which give the systematic correction to the theoretical values and reveal the accidental errors in the experimental values. The technique is the same as was used in previous examinations of the Li, Be, B, O and F sequences. The results are summarized in tables of recommended level values (Z = 10-36) and recalculated wavelengths.

Ion cyclotron resonant heating (ICRH) using the minority heating scheme creates an extended tail on the ion distribution function at high perpendicular energies. Some of these fast ions have orbits which intersect the chamber walls of a Tokamak. The paper presents an analysis of the corresponding particle-orbit losses due to the r.f.-induced velocity diffusion. In particular the time evolution and the saturation value of the particle loss fraction are determined.

Power reflection coefficients in σ and π polarisation (R_σ and R_π) have been obtained for silicon type semiconductors doped epitaxially with various concentrations of phosphorous. The coefficients R_σ and R_π are obtained as a function of incidence angle ϕ for disks of semiconductor material doped on one side epitaxially. The R_σ(ϕ) and R_π(ϕ) data are reported at four spot frequencies in the far infra-red. These data are not interpretable in terms of the simple band-edge equations of homogenously doped semiconductors in the far infra-red and contain more information than normal angle reflectivity (ϕ = 0), for which R_σ = R_π. The differences between the measured R_σ and R_π and the values given by the simple homogenous band edge theory vanish as σ → 90°, i.e., for glancing angles of incidence. The differences are at a maximum level for ϕ = 0°, i.e., for normal angles of incidence, especially in σ polarisation, but less so for π polarisation. This suggests that normal incidence reflectivity data probe more deeply into the structure of inhomogenously doped semiconductors or epitaxial layers.

The critical properties of the one-dimensional ferromagnets with classical discrete spins interacting ∼ r^-(1+σ) (1 - σ ≪ 1) in external magnetic field are investigated. Using low T expansion, relating these models with classical gases with generalized charges, the thermal and magnetic critical properties are found as for σ ≠ 1 (in first order on 1 - σ), as for σ = 1.