Table of contents

After a survey of the ground configurations of atoms in different stages of ionization through the periodic system we indicate the present state of analysis for spectra of atoms and ions containing up to 28 electrons. The energy level structure of systems with up to 18 electrons is illustrated by diagrams of individual spectra and of isoelectronic sequences. A critical compilation of references to recent analyses of the spectra of elements with Z⩽28 is appended.

The partially ionized plasma centrifuge contains a neutral gas mixture of isotopes or elements, the motion of which is driven by a small amount of rotating plasma. The plasma motion is, in its turn, controlled by externally imposed electric and magnetic fields. In this report earlier investigations of the centrifuge are extended by an analysis of its operation conditions. It is shown that high rotational velocities, large separation degrees, and stable velocity profiles can be achieved at comparatively small power losses, within certain ranges of the parameters involved.

Electrically conducting non-newtonian fluid materials, called second grade Rivlin-Ericksen magnetofluids are defined. We introduce and study the class of lineal magnetohydrodynamic flows, which includes Hartmann flow. Steady Hartmann flow is discussed in detail. In the class of lineal magnetohydrodynamic flows there are wave solutions for second grade Rivlin-Ericksen magnetofluids. Effects of our generalized constitutive assumption are examined for some special cases and compared with classical results for perfect and linearly viscous magnetofluids.

Cascade and cross-over transitions within the 3/2^-[521] and 11/2^-[505] bands as well as within a strongly perturbed band with positive parity are observed when high-spin levels in ¹⁵⁹Dy are populated in the ¹⁵⁸Gd(α,3n)¹⁵⁹Dy reaction. The rotational energies and the relative electromagnetic transition probabilities are discussed within the framework of the classical particle rotor model. The irregular structure of the 3/2^-[521] band and the positive-parity band can be reproduced to within 0.09 keV and 1.3 keV, respectively, in calculations where the theoretical Coriolis matrix elements are reduced. Furthermore, in these calculations the description of the relative transition probabilities in the positive-parity band is consistent with the calculations performed for ¹⁶¹Dy only if the intraband M1 transitions with ΔK=1 are artificially reduced by the same amount as the matrix elements of the Coriolis force.

The ordering in FeSi alloys with Si-content less than 25 at% has been examined. At low Si contents there is a relatively strong preference for large Si-Si inter-atomic distances. Furthermore a two phase region exists in the region from about 10 at% to about 20 at% Si, one of the phases probably of DO₃ type.

The design and performance of a high intensity pulsed electron beam system, operating at 600 kV, is discussed. The emitted peak current is 5.7 kA, the pulse length 25 ns and the calculated dose rate 3.6 × 10¹⁴ rad/s.

Periodic variations in geomagnetic activity have been investigated, in the range from 4 to 40 days, by means of power spectrum analysis during the period 1932 to 1969. Main periodicities are found to exist at periods of 28.7, 13.3, 9.1 and 6.9 days. To investigate the influence of recurrent magnetic storms on the periodic phenomena in the data, in particular the 27-day variation, an attempt has been made to remove disturbed periods from the data. The variation of the power density at different frequencies–particularly the 27-, 13-, 9- and 6-day variation–with the solar cycle has been investigated. An average value of the period of the 27-day variation has been determined by means of a modified power spectrum technique. A high correlation with the solar cycle has been found and possibilities of a multiple cycle have also been discussed.