Theoretical description of adiabatic laser alignment and mixed-field orientation: the need for a non-adiabatic model

We present a theoretical study of recent laser-alignment and mixed-field-orientation experiments of asymmetric top molecules. In these experiments, pendular states were created using linearly polarized strong ac electric fields from pulsed lasers in combination with weak electrostatic fields. We compare the outcome of our calculations with experimental results obtained for the prototypical large molecule benzonitrile (C$_7$H$_5$N) [J.L. Hansen et al, Phys. Rev. A, 83, 023406 (2011)] and explore the directional properties of the molecular ensemble for several field configurations, i.e., for various field strengths and angles between ac and dc fields. For perpendicular fields one obtains pure alignment, which is well reproduced by the simulations. For tilted fields, we show that a fully adiabatic description of the process does not reproduce the experimentally observed orientation, and it is mandatory to use a diabatic model for population transfer between rotational states. We develop such a model and compare its outcome to the experimental data confirming the importance of non-adiabatic processes in the field-dressed molecular dynamics.Comment: 11 pages, 9 figure

Stark deceleration of CaF molecules in strong- and weak-field seeking states

We report the Stark deceleration of CaF molecules in the strong-field seeking ground state and in a weak-field seeking component of a rotationally-excited state. We use two types of decelerator, a conventional Stark decelerator for the weak-field seekers, and an alternating gradient decelerator for the strong-field seekers, and we compare their relative merits. We also consider the application of laser cooling to increase the phase-space density of decelerated molecules.Comment: 10 pages, 8 figure

Mathematical and computer modeling of electro-optic systems using a generic modeling approach

The conventional approach to modelling electro-optic sensor systems is to develop separate models for individual systems or classes of system, depending on the detector technology employed in the sensor and the application. However, this ignores commonality in design and in components of these systems. A generic approach is presented for modelling a variety of sensor systems operating in the infrared waveband that also allows systems to be modelled with different levels of detail and at different stages of the product lifecycle. The provision of different model types (parametric and image-flow descriptions) within the generic framework can allow valuable insights to be gained

Imaging Molecular Structure through Femtosecond Photoelectron Diffraction on Aligned and Oriented Gas-Phase Molecules

This paper gives an account of our progress towards performing femtosecond time-resolved photoelectron diffraction on gas-phase molecules in a pump-probe setup combining optical lasers and an X-ray Free-Electron Laser. We present results of two experiments aimed at measuring photoelectron angular distributions of laser-aligned 1-ethynyl-4-fluorobenzene (C8H5F) and dissociating, laseraligned 1,4-dibromobenzene (C6H4Br2) molecules and discuss them in the larger context of photoelectron diffraction on gas-phase molecules. We also show how the strong nanosecond laser pulse used for adiabatically laser-aligning the molecules influences the measured electron and ion spectra and angular distributions, and discuss how this may affect the outcome of future time-resolved photoelectron diffraction experiments.Comment: 24 pages, 10 figures, Faraday Discussions 17

Coulomb explosion imaging of small organic molecules at LCLS.

Fragmentation of small organic molecules by intense few-femtosecond X-ray free-electron laser pulses has been studied using Coulomb explosion imaging. By measuring kinetic energies and emission angles of the ionic fragments in coincidence, we disentangle different fragmentation pathways, for certain cases can reconstruct molecular geometry at the moment of explosion, and show how it depends on LCLS pulse duration

Reduction of quartz to silicon monoxide by methane-hydrogen mixtures

The reduction of quartz was studied isothermally in a fluidized bed reactor using continuously flowing methane-hydrogen gas mixture in the temperature range from 1623 K to 1773 K (1350 °C to 1500 °C). The CO content in the off-gas was measured online using an infrared gas analyzer. The main phases of the reduced samples identified by XRD analysis were quartz and cristobalite. Significant weight loss in the reduction process indicated that the reduction products were SiO and CO. Reduction of SiO2 to SiO by methane starts with adsorption and dissociation of CH4 on the silica surface. The high carbon activity in the CH4-H2 gas mixture provided a strongly reducing condition. At 1623 K (1350 °C), the reduction was very slow. The rate and extent of reduction increased with the increasing temperature to 1723 K (1450 °C). A further increase in temperature to 1773 K (1500 °C) resulted in a decrease in the rate and extent of reduction. An increase in the gas flow rate from 0.4 to 0.8 NL/min and an increase in the methane content in the CH4-H2 gas mixture from 0 to 5 vol pct facilitated the reduction. Methane content in the gas mixture should be maintained at less than 5 vol pct in order to suppress methane cracking

Die Integration der Länder Mittel- und Osteuropas in die Europäische Union. Gründe und Auswirkungen der Güterströme zwischen beiden Regionen.

Die jungen Marktwirtschaften der Staaten Mittel- und Osteuropas streben nach der Mitgliedschaft in der Europäischen Union. Bereits im April 1998 werden erste Beitrittsverhandlungen mit fünf Ländern aus der Region beginnen. Die ökonomische Problematik einer Integration der Reformländer in den Binnenmarkt betrifft u.a. die Frage nach den Gründen und Auswirkungen liberalisierten Handels, der mit dem Eintritt in die 15er-Gemeinschaft gewährleistet ist. Ist freier Handel - als Folge des EU-Beitritts - angesichts relativer wirtschaftlicher Unterentwicklung der früheren RGW-Staaten gegenüber den Ländern Westeuropas überhaupt möglich und für beide Regionen sinnvoll? Welche Effekte bringt der freie Güteraustausch den Handelspartnern und läßt sich eine Handelsstruktur ableiten? Unter welchen Bedingungen kann die Ausdehnung des Integrationsraumes Europäische Union für alle Beteiligten wohlfahrtserhöhende Wirkungen haben? Diesen Fragen soll mit Hilfe der in der Außenwirtschaftstheorie entwickelten Aussagen nachgegangen werden. Hierbei ist die Praktikabilität dieser Erklärungsansätze kritisch zu würdigen, und die gewonnenen Ergebnisse sind auf den untersuchten Sachverhalt anzuwenden. Anhand von Resultaten empirischer Untersuchungen sind schließlich die tatsächlichen und potentiellen Entwicklungen des Handels zu beleuchten sowie Handlungsempfehlungen für die Fortführung des Integrationsprozesses zu formulieren

The Ability of the Associate Reform States of Central and Eastern Europe to Free Trade with the European Union

The young market economies of the states in Central and Eastern Europe (CEE) are knocking at the door of the European Union. This led public and economic discussion to a debate on the question, if, considering the relative economic underdevelopment of the reform countries compared with the EU-states, is free trade - with resulting accession to EU - between CEE countries and the EU possible, without destroying these inferior economies because of confrontation with the superior western competition or exposing them to high welfare losses. Often the competitiveness of these countries is doubted, recommendations for a protectionist trade instead of opening the market to the west follow these assessments. The start point of this paper shows an approach against an eastern enlargement of the EU, the arguments are presented in political discussion as economic correlations. These arguments must be analysed. With the achieved results, the ability of the associate reform states to accede and perform economically will be examined, and either supported or rejected