Table of contents

A Monte Carlo programme simulating the parton jet evolution has been developed. The scheme underlying the programme is described. Some results are presented. Our predictions for the same-side energy flux correlations are in reasonable agreement with recent data from e⁺e^- experiments.

The dynamical properties of many-dimensional solitons in the framework of the Klein-Gordon equation with logarithmic nonlinearity have been studied by means of the computer simulations. The existence of the same types of soliton interactions found earlier in the framework of the Klein-Gordon equation with saturable nonlinearity is displayed. It means that the types of soliton interaction are model independent. Some details of the numerical simulation techniques are discussed.

The properties of high-spin levels in ²⁰⁴Bi have been studied using conventional in-beam γ-ray and conversion-electron spectroscopy on the products of the reactions ²⁰⁵Tl(α, 5n) ²⁰⁴Bi and ²⁰³Tl(α, 3n) ²⁰⁴Bi. The yrast cascade is followed to a 19⁺ level at 3808 keV and several non-yrast levels in the spin interval J = 9-16 are reported. The energies of the levels in ²⁰⁴Bi were calculated within the shell-model frame of multi-nucleon states, and the agreement is found to be good. A previously reported T_1/2 = 1 ms isomeric state is shown to have a main configuration πh_9/2ν(j^-2)₀+(i_13/2^-2)₁₂+f_5/2^-1 and a spin-parity 17⁺. The configuration mixing for the neutron-hole components of the wave functions is discussed.

The Vlasov description of the free electron laser is generalized in order to include in the formalism a nonzero static guide magnetic field as well as a finite frequency pump field. It then turns out that the coupling coefficients still are positive even if the amplitude of the helical wiggler field is arbitrarily large.

An investigation is made of the heat transport equation T_t = (1/r)(rKT_r)_r where the thermal conductivity, K, is of the form K ∼ r^γTⁿ (T being temperature and r radial coordinate). The analysis presents a systematic way to obtain analytic approximations for the radial temperature profile and the decay time of the temperature, in good agreement with numerical calculations. The results are applied to several thermal energy transport models for magnetically confined plasmas.

A gas of two-level atoms is strongly saturated by a standing wave field. The same transition is probed by a weak tunable field. The observed probe absorption displays features due to both population modifications and coherences induced by the strong field. The probe spectrum is evaluated and interpreted in terms of coherent and incoherent multiphoton processes, power shifts and Stark splittings. Specific standing wave effects are identified and discussed. The relations to previous treatments are clarified.

In this paper we report on the effects of recoil on the steady state response of a three level atomic system in two photon absorption. The strength of the fields and their respective frequencies are arbitrary. The expression we derive reduces to that derived earlier, when recoil is neglected. From numerical calculations we conclude that the inclusion of recoil introduces shifts and asymmetries in the response vs. the detuning. We found how the magnitude of the shift depends on the ratio of the probe frequency to the pumping frequency.

A theoretical investigation is made of the generation of coherent radiation by a relativistic electron beam interpenetrating an active molecular medium. The system is assumed to be acted upon by a ripple magnetic field. A cold-fluid model is used for the description of the relativistic electron beam and a two-level Lorentz model for the molecular medium. A dispersion relation is deduced which governs the various possibilities of wave couplings and associated instabilities.

The linear and nonlinear stability properties of pressure driven electromagnetic interchange modes are investigated in the presence of a transverse current gradient. Possibilities for both stabilization and destabilization are obtained. The influence of nonlinear mode interactions is considered and explosively unstable situations are found. The influence of injected ions and fusion generated alpha particles are also discussed. In particular it is demonstrated for a slab geometry that the curvature drift of alpha particles is not serious for the stability.

The neutral density profiles in the F-1 device have been calculated using the measured electron density and temperature profiles. The results from the fluid description have been compared with the numerical solution of the Boltzmann equation. It is found that the fluid model slightly underestimates the neutral density in the center of the discharge. The profiles indicate that a minimum input power of 0.3 MW is needed to keep the central plasma temperature above the hydrogen ionization limit. For higher input powers the plasma becomes impermeable to the neutrals and thus a true cold gas-blanket state is attained. The size of the ionization region of this blanket decreases with increasing input power and this confirms qualitatively the earlier obtained results.

Simple analytical expressions, describing the effects of negative ions on the density fluctuation spectrum of a plasma with different electron and ion temperatures, are presented.

The photoelectric yield spectrum, proportional to the absorptance, of thin metal films is calculated. The film is described by either a dielectric function having a discrete single-particle excitation spectrum or, for comparison, a continuous spectrum (Lindhard). A numerical example of a 15 Å thick potassium film on a substrate is given to illustrate the changes in absorptance when the dielectric response is described differently. In the frequency derivative of the absorptance spectrum structure due to bulk plasmon resonances, well in accordance with experimental data, as well as single-particle excitations, not yet looked for experimentally, are found. We predict structure due to single particle excitations in electron energy-loss spectra.

Accurate core level binding energies for the L and M shells in the metals ²²Ti to ³⁰Zn have been measured by means of ESCA. Comparisons with previously reported data in many cases show discrepancies of several eV. The spin-orbit splittings of the 2p subshells have been measured with high accuracy and are compared with theoretical values.

The primitive frozen core model of the Hartree-Fock approximation has been improved by including an l-dependent core polarization potential in the valence orbital equation. The improved model yields ionization energies in good agreement with observations for a large number of s-p- and d-levels of several members of the Beryllium isoelectronic sequence. These energies and the corresponding orbital wave-functions have been used to calculate oscillator strengths for electric dipole transitions and appear to yield reliable f-values in many cases.

The phase conventions for a rotating diatomic molecule (Hund's case a) under the symmetry operation E*(X_i, Y_i, Z_i) = (-X_i-Y_i-Z_i), where X_i, Y_i, Z_i are the space-fixed Cartesian coordinates of all particles, are considered. It is shown that although various possible ways of approach are followed, they all lead to the same result, E*|ηΛSΣJMΩ⟩ = (-1)^J-S+8 · |η-ΛS-ΣJM-Ω⟩, provided that Euler angles and the phase of the D-matrix are chosen in consistency with certain standard text books. A comparison with earlier results in the literature is made.

We report 279 newly identified transitions of five times ionized zirconium atom (Zr VI) based on recordings made at the 3 m normal incidence spectrograph of Lund University. Thirty-three new energy levels have been established, comprising all the twenty-one levels of 5p configuration, all the nine of 4d that were not known so far, and three of 7s. Previously reported values of one 5d and four 6s levels have been improved.

The sixth ionization potential of zirconium 4p⁵²P_3/2 -4p⁴³P₂ is reevaluated from smooth ns Rydberg series to be 776 500 ± 500 cm^-1 which corresponds to 96.21 ± o.06 eV. Latest isoelectronic situation of 4p⁵6s levels is presented.

Based on spectrograms recorded for the region 250-2550 Å on the 3 m normal incidence spectrograph of Lund University, we have classified 358 lines, including 164 newly identified ones, as transitions between levels of excited configurations of Zr V. These classifications led us to establish 35 new energy levels belonging to the 4s²4p⁵6p, 7p, 5f and 6f configurations and to confirm energy levels of the configurations 4s²4p⁵ns (n = 5-10), 5p, 4d, 5d, 4f, 5g, 6g and 4s4p⁶4d reported by Reader and Acquista.

The ANDC method, used to correct atomic decay curves for cascades in beam-foil spectroscopy, has been further developed by combining it with a multi-exponential fit and a constraint equation. The advantages of the method are demonstrated with both simulated and experimental data, and some special decay situations are commented upon.

The frequency-dependent polarizability of a closed shell atom is considered in an RPA type approximation. This is usually done using many-body perturbation theory but can also be recast into the form of equations for the density oscillations as previously shown by the authors. The latter approach is known to lead to a non-hermitian problem because of the structure of the interaction kernel. This note shows that this is also true if using the reaction matrix method. The main result is to derive the expression for the polarizability function taking into account the nonhermitian nature of the problem.

An interferometric study of some Te II lines from the visible region has been performed. The computer analysis of the h.f.s. of 6 transitions was carried out giving the values of h.f.s. splitting for 10 levels of excited configurations. The A h.f.s. constants for 6 levels (three of 5s²5p²6p and three of a group of 5s5p⁴, 5s²5p²6s, 5s²5p²5d configurations) have been determined for the first time.