Table of contents

The theoretical work done in predicting a possible island of super-heavy elements with masses centered around A about 300, or about 15% in excess of the heaviest elements presently synthesized, is reviewed. Both the Hartree-Fock and the single-particle shell model approaches are discussed, with particular emphasis on the latter. The convergence in predictions of independent theoretical research groups is noted.

A single-particle model for non-spherical nuclei with a local diffuse potential having spheroidal and non-spheroidal shapes is studied. The dependence of energy eigenvalues, Coriolis matrix elements and some related quantities on various parameters of the model is investigated. The values of the potential parameters, as well as the questions of the ΔN = 2 mixing and the centrifugal interaction between particles in the rotor model, are discussed.

The relativistic effects in the hyperfine structure of the alkali atoms in their ground ²S_1/2 and excited ²S_1/2 and ²P_1/2,3/2 states are investigated by means of self-consistent-field calculations. Relativistic correction factors are obtained by comparing relativistic and non-relativistic results. Exact Hartree-Fock exchange as well as various statistical exchange approximations have been used. It is found that the correction factors are quite insensitive to the type of potential used in the calculation, while the values of the interaction parameters themselves differ appreciably between the different self-consistent-field schemes. The new correction factors are used to reanalyze the experimental data for the alkali atoms. Non-relativistic core polarization results have been corrected for relativistic effects and new quadrupole moments have been evaulated for the following nuclei: ⁷Li, ²³Na, ³⁹K, ⁸⁷Rb and ¹³⁴Cs.

Atomic lifetimes in multiply charged ions have been determined by the beam-foil technique at moderate ion energies (i.e. below 1 MeV). Low-lying transitions in In II, In III, Sn III, Sn IV, Sb IV, Sb V, Te V, Te VI, Tl II, Tl III, Pb III, Pb IV, Bi IV, and Bi V, exhibit sufficient spectral intensity at ∼ 500 keV initial ion energy to allow lifetime determinations. Systematic trends in oscillator strength values for the 5s²S-5p²P, 5p²P-5d²D and 6s²S-6p²P transitions in the Ag I and Au I sequences, and for the 5s¹S-5p¹P, 5p³P-5d³D, and 6s¹S-6p¹P transitions in the Cd I and Hg I sequences have been studied on the basis of the obtained atomic lifetimes. The f-value systematics in the Ag I, Au I, Cd I, and Hg I sequences are compared with similar trends in the Cu I and Zn I sequences.

The possibility of determining atomic mean-lives of excited levels in heavier atoms by the beam-foil technique using low initial ion energies was investigated with emphasis on correct energy-loss determinations. Cascade corrections are facilitated at low energies, especially for excited states with long lifetimes. The mean-life of the 3p²P⁰1 level in Na I was determined at 50 keV to be 16.2±0.5 ns. A number of mean-lives of excited levels in neutral and ionized neon, argon, krypton, and xenon were measured at ion energies ranging from 50 to 300 keV. The present xenon mean-lives are considerably shorter than reported in previous beam-foil studies.

The spectrum of trebly ionized magnesium, Mg IV, has been studied in the 2 000-100 Å and 3 500-3 300 Å ranges and the analysis revised and extended as regards the 2p⁴ 4s, 5s, 3p, 3d, 4d, 5d configurations: The 2p⁴ 3s, 4s, 3p, 3d configurations are now complete. Newly observed intercombination lines lead to accurate relative positions of level groups with different multiplicities or different parents. The (³P, ¹D) 3s, 4s, 3p, 3d and (¹S) 3s, 3p, 3d level systems have been located in relation to the ground term with an estimated accuracy of ±4 and ±5 cm^-1 respectively via the accurately measured resonance lines and 2s 2p⁶-2s² 2p⁴ 3p combinations. Accurate wavelengths in the 185-130 Å range have been calculated.

The coupling conditions have been studied using Condon-Slater theory. The 2p⁴ 3s, 3p, 3d, 4s configurations are best described with LS symbols; two 3p levels are heavily mixed and there are also deviations for some 3d levels.

The ionization energy derived from three members of the (³P)ns^4,2P_1½ series is 881 190 cm^-1.

The 2p⁴³P_2,1,0, ¹D₂, ¹S₀ intervals has been redetermined from the remeasured Mg V combinations 2s² 2p⁴³P-2s 2p⁵³P and 2s² 2p⁴¹S₀, ¹D₂, ³P₂-2s 2p⁵¹P₁.

The wavelengths of 31 Ce III lines from the transition 4f²-4f5d in the region 11 000-26 000 Å have been measured. The previously missing ³P term of the ground configuration 4f² has been found, so that this configuration is now completely known. The accuracy of the 4f² level values has been improved.

The high resolution Auger spectra from krypton (L_2,3MM and M_4,5NN) and xenon (M_4,5NN and N_4,5OO) have been obtained. The Auger lines are assigned by comparison with energies obtained from optical spectroscopy and relativistic Hartree-Fock-Stater calculations and the energies of new atomic levels have been found. Some of the satellite lines have been assigned to shake-up processes. Comparison with calculations of Auger intensities has also been made.

The spin structure of the metallic hexagonal B 35 phase of FeGe has been studied by means of susceptibility and magnetization measurements. Below the Neel temperature T_N = 411 K hexagonal FeGe is a uniaxial antiferromagnet with the spins parallel to the c-axis. In each c-plane all spins are ferromagnetically coupled with an exchange constant J₀ ≈ 22 meV. The antiferromagnetic exchange constant between nearest neighbour and next nearest neighbour c-planes are J₁ = -3.5 meV and J₂ = -0.9 meV resp. in the molecular field model. Susceptibility and spin flop experiments indicate that the spins tilt away from the c-axis below 30 K. We suggest that the spins then form a double cone structure with a cone halfangle of 20° at 4.2 K. In the double cone the c-plane components have a turn angle in the vicinity of 180° between nearest neighbour planes, which implies absence of long range order. The result is in good agreement with Fermi surface calculations by Sundström (Physica Scripta, following paper), which show the existence of several spin density wave vectors between Q = 0.89 π/c and Q = 1.3 π/c calipering different parts of the Fermi surface in a direction parallel to the c-axis.

Nonrelativistic APW calculations of the electronic energy bands of hexagonal (B 35) iron monogermanide (FeGe) have recently been published [15]. The present work extends these to determine the Fermi surface, which is formed from four energy bands. Large portions of the Fermi surface will be destroyed or distorted by magnetic superzones at the onset of antiferromagnetic ordering (T_N = 411 K). This is related to experimental resistivity measurements, which show a distinct anomaly at the Néel temperature. We find that "nesting" of Fermi hole and electron surfaces might give rise to a broad maximum in the generalized susceptibility around q = π/c. Further aspects of the role of the Fermi surface in magnetic ordering are briefly discussed.

The low field transverse magnetoresistance of hexagonal FeGe has been measured for the field in the basal plane with current both parallel and perpendicular to the c-axis. At a temperature dependent critical field (Δϱ/ϱ₀) // c shows a sharp peak, then decreases rapidly until it levels off at a second critical field. (Δϱ/ϱ₀) ⊥ c exhibits a sharp dip at the first critical field followed by rising magnetoresistance with increasing field until the second critical field, where it levels off. The observed anomalies are related to changes in the spin structure and magnetic superzone effects. The possibilities of itinerant antiferromagnetism are also considered.

The Comptonprofile for crystalline BN (hex.) is calculated for some simple models. The connection between different scattering functions and the total electronic energy is briefly discussed.

The characteristics of a continuously evacuated transmission anode flash X-ray tube have been studied in the voltage range 250 kV-600 kV. Tube current, dose, pulse length and spatial distribution of the emitted radition were studied. Typical values of the dose 0.5 m from the exit window and the pulse length are 115 mR and 20 ns respectively.

A new three-electrode light source, the hollow spark, has been developed by combining an open vacuum spark and a sliding spark. Its design and qualities are described and compared to other spark sources.