Table of contents

The generalization of grand angular momentum to N-particle states with relativistic energies achieved classically in a previous paper is now transcribed into quantum mechanical language. The grand angular momentum are the generators L_ij of a O(3N - 3)-invariance group of the invariant mass operator for N free particles. A radial momentum is defined as well as O(3N - 3)-invariant operators conjugate to radial momentum or total mass.

A construction is made of wave functions spanning irreducible representation spaces of O(3N - 3) which are labelled by the eigenvalues of "togetherness" Λ² = ½ Σ_ijL_ij². Finally the sum of all those spaces is shown to be irreducible under a group O(3N - 3, 1)/t (where t is "time reversal") which is an invariance group of the mass operator and its canonical conjugate.

An investigation of the integrated isothermal and isenthalpic Joule-Thomson effect and also of the isothermal and adiabatic Joule-Thomson coefficient for gas mixtures has been performed. It is shown that the experimental results of the integrated isenthalpic effect for gas mixtures obtained by Koeppe are in agreement with the qualitative results from the van der Waals thermal equation of state. A special interest is devoted to the question whether the cooling effect for a given inlet state and a given exit pressure of the throttling device, can be larger for a binary mixture than for both of its constituents. It is found that this is possible and this result is confirmed for a mixture of nitrous oxide and ethylen by the experimental results of Charnley et al. The adiabatic and isothermal zero pressure Joule-Thomson coefficients are analyzed as functions of the composition for fixed temperature and the conditions for maxima and minima are stated. The results for the isothermal coefficient are in agreement with the measurements reported by Charnley et al. The Joule-Thomson coefficients have also been studied with the aid of the principle of corresponding states and an equation for the zero pressure isothermal Joule-Thomson coefficient following from this principle has been derived from the experimental values of this coefficient. Further it is shown that for gases obeying the principle of corresponding states a necessary condition for a minimum of the zero pressure isothermal Joule-Thomson coefficient considered as a function of composition for fixed temperature, is that one of the constituents has a larger critical temperature and a smaller critical molar volume than the other one.

The atomic beam magnetic resonance method has been used for measurements of the spin and hyperfine structure of the ground state of ⁴⁹Cr (42 m) with the following results: I = 5/2, |a| = 49.754 (2) MHz and |b| = 0.018 (17) MHz. The magnetic dipole moment has been calculated from the measured hfs and the known values for ⁵³Cr to be |μ_I| = 0.476 (3) n.m.

The lifetimes of the excited states in ¹³³Cs have been measured by the delayed coincidence technique. The results are:

The 81.0 keV level: T_½ = 6.27 ± 0.04 ns

The 160.5 keV level: T_½ = 190 ± 15 ps

The 384 keV level: T_½ = 40 ± 20 ps

The 437 keV level: T_½ ⩽ 150 ps

A comparison is made between experimental and theoretical transition probabilities. The 160 keV state is interpreted as a three quasi particle state.

The energies and intensities of thermal-neutron capture gamma rays from ⁷⁴Ge have been measured with a Ge(Li) detector. An internal target of enriched ⁷³Ge has been used. The reaction Q-value and excitation energies have been determined. The decay scheme of ⁷⁴Ge is discussed in view of the vibrational model.

Auger spectra in gaseous CH₄, CH₃Br, CH₂Br₂, CHBr₃, CBr₄, C₂H₆, and C₆H₆ are excited by electron impact at about 5 keV energy and observed by means of a spherical electrostatic spectrometer at 90° to the primary electron beam. Besides the energies and the intensities of the Auger lines and the chemical shifts, the analysis of the spectra gives the energies and the lifetimes of the doubly ionized molecules. The line widths together with energy considerations indicate that some of these doubly ionized molecules rapidly dissociate. Comparisons are also made between the bromine and the carbon spectra.

The Kβ₁β' structure is investigated experimentally for all pure elements of the first transition series and for some of their compounds. Analogous structures are found for L emission spectra of some second transition series elements as well as of some lanthanides. Relative transition energies and probabilities are calculated in a frozen-orbital approximation for the transition from a normal K state to singly ionized states of the configuration 3p⁵3dⁿ4s² for the elements Sc-Ni. The results support the interpretation that the Kβ₁β' structure is due to the electron interaction between partially filled 3p and 3d subshells. The electron interaction mechanism also explains the effects in the heavier elements investigated.

Two new band systems attributed to the Si₂ molecule have been obtained in absorption in flash discharges in SiH₄. They are situated in the region 1 840-1 900 Å. They are here designated O³Σ_u^- - X³Σ_g^- and P³Π_g - D³Π_u. Rotational and vibrational constants have been derived for the O³Σ_u^- state. The 1-0 band of the N³Σ_u^--X³Σ_g^- system at 2118 Å has been reinvestigated.

The coupling coefficients, which account for the nonlinear interaction between three longitudinal plasma waves, are calculated. The results depend significantly on effects which are due to energy-dependent collision-frequencies and carrier masses.

The electrical resistivity of a single crystal of chromium was studied in the temperature range 10 to 70°C, allowing for nitrogenassociated relaxation near the Néel temperature. The results of these and earlier measurements are discussed using the theoretical model for the resistivity of heavy rare earths given by Elliott and Wedgwood (1963). In this discussion support is given to the Fermi surface proposed by Kimball (1969). A plausible explanation is given to the discontinuities and extra minima in the resistivity curves reported by other authors.

The existing experimental evidence for the influence of interstitial nitrogen on the physical properties of chromium near the Néel temperature and in the transversely polarized SDW region is discussed. On the basis of this influence it is proposed that the presence of interstitial nitrogen is essential to the problem of magnetic domain formation and the primary source of pinning of spins to "preferred" ⟨100⟩-directions.

Effects of co-axial magnetic and electric fields on time integral PAC have been studied theoretically. Formulae have been developed for the angular shift in the correlation pattern and for the P factor usually measured in a four detector set-up. The formulae have been applied to all the rare earth 3+ ions, for which values of electric and magnetic hyperfine interaction frequencies are calculated at zero temperature. The effect on the angular shift for different values of the lifetime of the excited states has been calculated for use in the interpretation of g-factor measurements at low temperatures. As an example of the temperature dependence of the hyperfine fields and angular shifts, one case was calculated for the temperature region 0-150 K.

The influence of non-coaxial magnetic and electric fields on radioactive nuclei embedded as impurities in ferromagnetic materials is considered. The attenuation factor G₂₂(t), as defined in perturbed angular correlation theory [1], is calculated for different angles β₀ between the directions of the magnetic field and the electric field gradient and for different ratios of the magnetic and electric frequencies. The method has been tested for Cd in ferromagnetic gadolinium.

Carbon 1s energies are measured by ESCA for a series of aliphatic saturated compounds, carbonyl compounds, and some aromatic compounds. For convenient use in chemical structure analysis the binding energy shifts are correlated with a charge parameter obtained from electronegativity considerations. The shifts are also analyzed in terms of group shifts from which group electronegativities are derived. A comparison is made between the shifts in solid and gaseous samples and it is shown that solid state effects are small for non-ionic compounds. The observed shifts are then compared with results of semi-empirical and ab initio molecular orbital calculations on free molecules. The theoretical calculations are simplified by use of an electrostatic potential model.