Photoionization of Kr near the 4s threshold: I. Experiment and LS coupling theory

Absolute cross sections for the transitions of the Kr atom into the 4s^1 and 4p^4nl states of the Kr^+ ion were measured in the 4s-electron threshold region by photon-induced fluorescence spectroscopy (PIFS). The cross sections for the transitions of the Kr atom into the 4s^1 and 4p^4nl states were also calculated, as well as the 4p^4nln'l' doubly excited states, in the frame of LS-coupling many-body technique. The cross sections of the doubly-excited atomic states were used to illustrate the pronounced contributions of the latter to the photoionization process, evident from the measurements. The comparison of theory and experiment led to conclusions about the origin of the main features observed in the experiment.

The Containment of Labour Unrest in the Post Socialist China

Due to its transition from the socialist mode of production to the capitalist mode, workers in China have been exposed to the exploitative class relations that they hardly experienced before. The working class is now assuming a subordinate position in the relations of production while the capitalist class remains in the dominant position. As a consequence, workers’ protests are constantly emerging and class conflicts are exacerbating in the contemporary China. I have set out to study in this paper how the party-state in China contains labour unrest through the All China Federation of Trade Unions (the ACFTU), which I argue is a state apparatus that performs the ideological, political and economic functions in different situations. There has been an ongoing academic debate on if the ACFTU is defending workers’ interests. Some scholars have expressed optimism while some have taken a dim view. Drawing on Poulantzas’ theory of capitalist state, I hope to make contribution to this debate by demonstrating that the ACFTU is under some circumstances serving the short term interests of workers as individuals, but not the economic and political interests of workers as a class. Instead of organizing workers to overcome the effects of isolation or forming a class for itself, the ACFTU attempts to contain labour unrest and reproduce their subordination in the relations of production.

Decision‐Making in Public Good Dilemmas: Theory and Agent‐Based Simulation

In many real world contexts individuals find themselves in situations where they have to decide between options of behaviour that serve a collective purpose or behaviours which satisfy one’s private interests, ignoring the collective. In some cases the underlying social dilemma (Dawes, 1980) is solved and we observe collective action (Olson, 1965). In others social mobilisation is unsuccessful. The central topic of social dilemma research is the identification and understanding of mechanisms which yield to the observed cooperation and therefore resolve the social dilemma. It is the purpose of this thesis to contribute this research field for the case of public good dilemmas. To do so, existing work that is relevant to this problem domain is reviewed and a set of mandatory requirements is derived which guide theory and method development of the thesis. In particular, the thesis focusses on dynamic processes of social mobilisation which can foster or inhibit collective action. The basic understanding is that success or failure of the required process of social mobilisation is determined by heterogeneous individual preferences of the members of a providing group, the social structure in which the acting individuals are contained, and the embedding of the individuals in economic, political, biophysical, or other external contexts. To account for these aspects and for the involved dynamics the methodical approach of the thesis is computer simulation, in particular agent-based modelling and simulation of social systems. Particularly conductive are agent models which ground the simulation of human behaviour in suitable psychological theories of action. The thesis develops the action theory HAPPenInGS (Heterogeneous Agents Providing Public Goods) and demonstrates its embedding into different agent-based simulations. The thesis substantiates the particular added value of the methodical approach: Starting out from a theory of individual behaviour, in simulations the emergence of collective patterns of behaviour becomes observable. In addition, the underlying collective dynamics may be scrutinised and assessed by scenario analysis. The results of such experiments reveal insights on processes of social mobilisation which go beyond classical empirical approaches and yield policy recommendations on promising intervention measures in particular.

Re-Framing Trade

Given the substantial and increasing encroachment of trade agreements into almost every aspect of economic and social life, there is a pressing need for research that provides a more coherent framework for understanding the source and effectiveness of organised labour ’s power and capacity to influence international trade policy. Taking the union protests against the General Agreement on Trade in Services (GATS) as a case study, this research uses core concepts derived from social movement theory to analyse the opportunities that existed for unions to influence these trade negotiations and their capacity to identify and take advantage of such opportunities. Importantly, it adds a power analysis designed to reveal the sources of power that unions draw on to take action. The research demonstrates that even where unions faced considerable constraints they were able to re-frame trade issues in a way that built broad support for their position and to utilise opportunities in the trade negotiation process to mobilise resistance against the GATS and further liberalisation of services. The theoretical framework developed for the research provides conceptual tools that can be developed for improving strategic campaign planning and for analytical assessment of past campaigns. The theoretical framework developed for this research has potential for further application as an analytical and strategic planning tool for unions.

Many-body theory of laser-induced ultrafast demagnetization and angular momentum transfer in ferromagnetic transition metals

An electronic theory is developed, which describes the ultrafast demagnetization in itinerant ferromagnets following the absorption of a femtosecond laser pulse. The present work intends to elucidate the microscopic physics of this ultrafast phenomenon by identifying its fundamental mechanisms. In particular, it aims to reveal the nature of the involved spin excitations and angular-momentum transfer between spin and lattice, which are still subjects of intensive debate. In the first preliminary part of the thesis the initial stage of the laser-induced demagnetization process is considered. In this stage the electronic system is highly excited by spin-conserving elementary excitations involved in the laser-pulse absorption, while the spin or magnon degrees of freedom remain very weakly excited. The role of electron-hole excitations on the stability of the magnetic order of one- and two-dimensional 3d transition metals (TMs) is investigated by using ab initio density-functional theory. The results show that the local magnetic moments are remarkably stable even at very high levels of local energy density and, therefore, indicate that these moments preserve their identity throughout the entire demagnetization process. In the second main part of the thesis a many-body theory is proposed, which takes into account these local magnetic moments and the local character of the involved spin excitations such as spin fluctuations from the very beginning. In this approach the relevant valence 3d and 4p electrons are described in terms of a multiband model Hamiltonian which includes Coulomb interactions, interatomic hybridizations, spin-orbit interactions, as well as the coupling to the time-dependent laser field on the same footing. An exact numerical time evolution is performed for small ferromagnetic TM clusters. The dynamical simulations show that after ultra-short laser pulse absorption the magnetization of these clusters decreases on a time scale of hundred femtoseconds. In particular, the results reproduce the experimentally observed laser-induced demagnetization in ferromagnets and demonstrate that this effect can be explained in terms of the following purely electronic non-adiabatic mechanism: First, on a time scale of 10–100 fs after laser excitation the spin-orbit coupling yields local angular-momentum transfer between the spins and the electron orbits, while subsequently the orbital angular momentum is very rapidly quenched in the lattice on the time scale of one femtosecond due to interatomic electron hoppings. In combination, these two processes result in a demagnetization within hundred or a few hundred femtoseconds after laser-pulse absorption.