Table of contents

It is suggested that frictional forces can be incorporated into quantum mechanics by using the adiabatic time dependent approximation. In particular it is shown that for a linear harmonoc oscillator the ratio between the square of the displacement of the damped and undamped harmonoc oscillator is the same as the ratio between the expectation values of the squares of the displacement of the damped and undamped harmonic oscillator.

The γ-rays following inelastic scattering of highly monochromatic neutrons on ¹⁴¹Pr have been studied for neutron energies up to 2.6 MeV. The results suggest that the level scheme of ¹⁴¹Pr now can be considered to be complete as regards levels with I ⩽ 15/2 up to an energy of 2.2 MeV.

Theoretical and experimental investigations of the quartet system of B III have been undertaken. Numerous transitions not reported earlier are predicted with high accuracy. Experimentally a number of new transitions has been observed for the first time. Based on this work several lines from other experimental sources are reclassified. Oscillator strengths and lifetimes associated with these quartet states are also given. Finally an improved term diagram for the doubly-excited quartet levels in B III is presented on an absolute scale.

The spectrum of F VII has been studied between 400 and 6000 Å by the beam-foil method. In this interval 48 F VII lines have been identified. The analysis includes also 39 lines below 200 Å from an unpublished wavelength list from Edlén. From these lines, 35 energy levels have been determined and the whole term system is described by Ritz formulae and by using the polarization parameterization. The ionization energy is determined to 1 493 632 ± 5 cm^-1.

The experimentally determined energy levels are found to be in good agreement with the values predicted by Edlén (Physica Scripta, 19, 255 (1979)) in a study of the Li I isoelectronic sequence.

In addition five F VIII lines are also reported.

Because of the confusion between two low odd levels 1218 cm^-1 apart, the complete system of levels of Nd II built on the core f³ had to be revised with the help of the ¹⁴⁴Nd-¹⁵⁰Nd isotope shift. The lowest odd level f³d²⁶M_13/2 is now at 8009.810 cm^-1, 96 levels have been shifted and 126 new levels have been found. The new identifications rely upon parametric studies of the sub-configurations 4f³5d6s + 4f³(⁴I)5d² + 4f⁴(⁵I)6p (115 interpreted levels) and 4f³(⁴I)5d6p + 4f³(⁴I)6s6p (124 interpreted levels).

From the line emission of a pure neon plasma produced in a theta pinch discharge rate coefficients for the excitation of the n = 3 and 4 levels in Ne VIII ions are derived and compared with theoretical calculations and previous measurements. The general agreement between theory and all measurements is rather satisfactory for the excitation to the n = 3 levels, the measured rate coefficients to the 4p and 4d levels, however, being consistently too low.

It is found that the threshold strength value of the electric field of S-polarized SHF wave respecting the generation of the fast electron fluxes in an inhomogeneous plasma with the critical density is described by the dependence for the decay instability. At the decreasing plasma density below the critical value this dependence transforms into that for the kinetic instability. Evolution of the fast electron spectrum at increasing of the electric field strength of the wave and decreasing of the plasma density is studied.

The angular distribution of the overthermal electron currents and their energy spectra in the vicinity of the critical density layer in an inhomogeneous plasma due to the action of focused SHF radiation is studied. Relation of the overthermal electron streams to the anomalous high electron collision frequencies in plasma due to streaming instability is pointed out.

Littlejohn's guiding-center mechanics, with the polarization drift included, is rederived from a Lagrangian. The respective collisionless kinetic guiding-center theory is then established. While single-guiding-center energy is exactly conserved here in time-independent fields, the self-consistent kinetic guiding-center theory presented here conserves the total energy of the guiding-center plasma and its self-consistent electromagnetic fields only to leading order in ≡ r_g/L. The present formalism seems to be relevant to the theory of drift waves and anomalous transport.

We investigate the possible effects a realistic treatment of the surface region of a small metal particle can have for explaining the reported anomalously large far-infrared absorption. Though the absorption is about one order of magnitude larger, for the electric dipole term, than in a classical treatment for a sharp interface it is still too small. The magnetic dipole term is virtually unaffected since it does not involve the field component perpendicular to the surface which is the one mainly responsible for the increase in the electric dipole absorption.

Two simple models are developed for dealing with inelastic light scattering from an adsorbate-substrate complex. The first accounts for the surface enhanced Raman scattering viewing the metal as the source of light scattering and the molecule providing the vibrational quanta needed. Good agreement for the "chemical" enhancement is obtained compared with more sophisticated calculations and we elaborate upon a connection between the scattering cross section and the damping of the molecular vibration in question. The other model treats SHG from adsorbates, being possible because the surface breaks the inversion symmetry and thus sets up an unsymmetrical environment.

A previous treatment of core-level binding-energy shifts for metals is extended to Auger energy shifts. In comparison to single core-hole shifts, the new information given by the Auger shift is contained in the shift of the two core-hole final state. An accurate expression for the shift of the two core-hole ionization energy between the free atom and the metal is derived. In the actual calculation of the shift a (Z + 2) equivalent core approximation is applied, but where important corrections are included. Comparison between theory and experiment is performed for the metallic elements Na-Al, Ni-Ga, Pd-Sn, Au, Tl-Bi, Ba and Yb, and in all cases a good agreement is obtained. A rather detailed compilation of atomic and solid phase double-hole energies is presented in the Appendices. To elucidate the break-down of the concept of metallic screening, non-conducting elements like Si, Ge-Se, Sb and Te are also considered. In addition, atom-metal two core-hole energy shifts are calculated for the 4d transition series and an abrupt change in the energy shift is found when we proceed from the d elements to the elements beyond. The influence of the atomic structure on the shift is considered for the 4dⁿ5s², 4dⁿ+15s and 4dⁿ⁺² configurations. The metallic renormalization of the atomic core-hole Coulomb correlation energy is calculated for the 4d elements and the chemical shift of this quantity is shown to be closely related to the change of the Auger parameter. The present formalism provides a most suitable framework for treating chemical shifts in metallic systems. As a special example the situation at the surface of a metal is considered and surface shifts are predicted both for the two-hole and the Auger energies. As for the single core-holes, these surface shifts change sign as we proceed through a transition series due to the bonding-antibonding division of the d-band.

It is shown how results from an efficient calculational scheme for lattice dynamics of dipole active surface vibrational modes, in the energy range of the bulk phonon band, can be used to disciminate between different adsorption sites on a metal surface. In particular, the comparison of results for the ordered structures c(2 × 2)CO- and p(2 × 2)S-Cu(100) with measured Electron Energy Loss (EEL) spectra yields unique determination of the adsorption sites in the two cases. These results are readily interpreted in terms of symmetry restrictions for the dipole activity of surface phonons. In addition, sum rules for EEL spectra are derived and discussed.