Table of contents

The energies and intensities of gamma radiation from thermal neutron capture in ⁵⁰Ti and ⁶⁴Ni have been determined by means of a Ge(Li) pair and anti-Compton spectrometer. Internal reactor targets have been used. Decay schemes of ⁵¹Ti and ⁶⁵Ni are deduced. The neutron separation energy of ⁵¹Ti is 6 372.4±1.4 keV and that of ⁶⁵Ni 6 098.9±1.5 keV. The correlation coefficients between the (n,γ) and (d,p) strengths are -0.32 for ⁵¹Ti and 0.75 for ⁶⁵Ni.

Neutron radiative capture cross sections have been measured in the energy region 20 to 80 keV using time-of-flight techniques and a 12.7 cm × 10.2 cm NaI(Tl) scintillator as γ-ray detector. The samples studied were natural samples of F, Mg, Al, Si, P and S. Radiative widths were determined for the resonances in ¹⁹F at 27 keV (1.4±0.3 eV) and 50 keV (1.5±0.3 eV), in ²⁴Mg at 84 keV (4.0±0.9 eV) and in ²⁷Al at 35 keV (1.9±0.3 eV). Resonances were also observed in Mg at 45 keV, in Si at 38 keV and 68 keV, in P at 27 keV and in S at 30 keV and 42 keV.

The Mg I-like spectrum Ti XI has been analysed by using the line list of the titanium vacuum-spark spectrum in the region 50 to 425 Å published by Svensson and Ekberg. At the same time the iso-electronic spectra of potassium, calcium and scandium have been checked and extended. The main new results concern the singlets, but the triplet systems have also been improved. Intersystem combinations have been found for Ca IX, and the singlet-triplet connection for the other element has been established by interpolation. The np- and nd-series are now extended to n=7 and the nf-series to n=6. However, series perturbations affect the determination of the ionization energies, which causes an uncertainty of 0.08% to 0.05%.

The transitions 3s²3p^k-3s3p^k+1 have been measured in Ti VI (k = 5) and Ti VII (k = 4). In Ti VI the observed ground-term interval is found to be 5 829.3±1.1 cm^-1. A four-parameter formula, expressing the Z-dependence of this interval, has been derived from the best observed values through the sequence from Cl I to Ni XII. It reproduces the observed intervals within their error limits. In Ti VII the ground-configuration intervals are measured and compared to previous measurements and calculations.

Six new spectral lines have been observed in the lithium spectrum between 200 nm and 600 nm. Possible classifications are given and discussed.

When a thin foil is inserted in the beam of a beam-gas experiment the beam particle state populations are driven far from their beam-gas equilibrium values. Downstream from the foil the "new beam" and gas species interact to produce a new equilibrium, usually different from the beam-gas one. We present experimental results to demonstrate this effect and show how relative cross-section measurements can be used to study the beam-foil interaction.

Theoretical calculations of relative X-ray emission energies and intensities were made with all-valence-electron molecular orbital methods on the following systems: SO₄^2-, SO₃^2-, SCN^-, ClO₄^-, and ClO₃^-. The relative energies are, for all cases, in agreement with experiments while the calculated intensities depend heavily on the approximation scheme chosen. The results indicate that a feature in the ClO₃^- spectrum previously attributed to decay products may partly originate from a molecular level. For SCN^- an intensity calculation based on the ab initio calculations by McLean and Yoshimine is also presented.

The atomic scattering factors for Cu and Al have been obtained from diffuse thermal scattering measurements. The results for Cu show a pronounced effect probably due to extinction. A transmission method gives results for Al at low values of sin θ/λ for the first time. These seem to agree with the theoretical atomic scattering factors for neutral Al atoms.

Different spinodal hypotheses are discussed. An analysis of experimental results shows that the passage of the classical spinodal has a marked influence on the rate of the initial decomposition of supercooled homogeneous alloys both when the decomposition is continuous, as in the AuPt-alloys, and when it takes place at the front of a discontinuous precipitation, as in AuNi-alloys. The preference of the discontinuous to the continuous precipitation in AuNi-alloys at high temperatures is made understandable by a discussion of the activation energies of different types of diffusion.

Measurements of the magnetic susceptibility, electrical resistivity and Hall effect have been made on FeP₂ single crystals prepared by a chemical transport reaction. FeP₂ is a diamagnetic semiconductor with a nearly temperature independent susceptibility of -(8.8±0.7)·10-⁶SI (at room temperature), and a band gap of 0.37 eV.

Rb₂MnCl₄·2H₂O, Cs₂MnBr₄·2H₂O and Rb₂MnBr·2H₂O are three antiferromagnetic substances of triclinic structure with Néel temperatures 2.24, 2.84 and 3.33 K respectively. Magnetization measurements have been carried out at 1.4 K in pulsed magnetic fields up to 10 T (100 kG). Exchange and anisotropy fields are calculated from the spin flop and the saturation fields.