Lars Asplund

Theory of band shape formation in Auger and autoionization spectra of molecules. Numerical applications and new high‐resolution spectra for CO

Theory of band shape formation in Auger and autoionization decay in molecules is presented and numerically applied to spectra of the CO molecule. In particular, the role of lifetime vibrational interference in the various vibronic decay channels is elucidated. New high resolution Auger and autoionization spectra are presented. The calculated band shapes are compared with the experimental recordings. The vibronic spectra of the intermediate states in the Auger and autoionization decay are analyzed and compared with available ESCA and EELS spectra, respectively. The role of the electron correlation on the formation of the core state potential surfaces is investigated in that connection. The assignment problem of the outer part of the CO Auger spectrum is reinvestigated and the effect of interference due to hole mixing in the wave functions is pointed out. The time dependent Franck–Condon (FC) formalism used to derive the lifetime vibrational interference is shown to have a bearing on the analogy of the sudd...

A high resolution multipurpose ESCA instrument with X-ray monochromator

Abstract The design and performance of a new high resolution multipurpose instrument are described and illustrated. The instrument comprises a high-power, fine-focusing e − -gun, a high speed rotating anode, a double focusing multi-crystal X-ray monochromator, a monochromatic UV-source with a toroidal grating, a fine-focus variable energy e − -source, a four-element electrostatic e − -lens system, a large 36 cm hemispherical electrostatic analyzer, a 12 cm wide electron multi-detector system and a dedicated computer system. Various sample probes for gases, liquids and solids are discussed. The instrument is shown to reach an energy resolution of at least 0.23 eV with X-ray excitation at a sufficient intensity to enable the study of gases. A number of illustrative examples of the proved instrumental performance is presented. A new “line-sharpening” effect, due to post-collision interaction in Auger electron spectra, is revealed due to the high spectrometer resolution. The strongest vibrational components of the C 1s ESCA line from methane are for the first time resolved. High resolution spectra are also presented for solids, e.g. the spin-orbit split Si 2p line is well resolved into two components and new resolved structures appear in the Ag and Au valence bands. Calculated density of states are found to be in good agreement with these structure rich d-bands. Phonon excitation accompanying the photoionization process is discussed in relation to its causing additional broadening of the Si 2p lines.

Vibrational structure and lifetime broadening in core-ionised methane

The ESCA spectrum of the 1s line from carbon in methane has been recorded and calibrated against the 2p line of argon using a new high-resolution multipurpose ESCA instrument with monochromatised Al Kalpha radiation. For the first time vibrational structure in a core-electron ESCA line is resolved. The energies, relative intensities and inherent widths of the resolved components of the core line have been accurately determined. Inclusion of the Doppler broadening effect is shown to be essential for the natural linewidth determinations. Energies and relative intensities have also been calculated using a contracted configuration interaction scheme (CCI) and a complete active space self-consistent field (CASSCF) program. Although the calculations reached well beyond the Hartree-Fock level, incorporating a large part of the correlation energy, the shape and position of the potential curves were still found to be non-stable. It was not possible to simultaneously accurately reproduce the experimental ionisation energy, vibrational splittings and relative vibrational intensities. The present kind of highly resolved experimental data therefore represents a critical test for advanced molecular CI calculations on deep core-hole states.

RUNESTONE, an international student collaboration project

Students will eventually work in a global market; what better preparation can be provided for international collaboration than...international collaboration? The RUNESTONE project is developing and evaluating the notion of incorporating international group projects into the undergraduate computer science curriculum. RUNESTONE adds new dimensions to student teamwork, requiring students to handle collaboration that is remote, cross-cultural and linguistically challenging. RUNESTONE is a three year project, with the prototype version running in Winter 1998 with students at Uppsala University, Sweden, and Grand Valley State University, Michigan, USA. The 1998 pilot study will be followed by a full-scale implementation in 1999 and another in 2000.

A Ravenscar-Compliant Run-time Kernel for Safety-Critical Systems*

The Ravenscar tasking profile for Ada 95 has been designed to allow implementation of highly safety critical systems. Ravenscar defines a tasking system with deterministic behavior and low complexity. We provide a formal model using UPPAAL of the primitives provided by Ravenscar including exceptions. This formal model is used to verify the correctness of the Ravenscar model and can be used to verify safety properties of applications using the Ravenscar profile. As an illustration of this, we model a sample application using all features of Ravenscar and formally verify its correctness. Furthermore, an introduction to the Ravenscar model is given.

An Improved Model for Post-Collision Interaction (PCI) and High Resolution Ar LMM Auger Spectra Revealing New PCI Effects

An improved semi-classical model for post-collision interaction (PCI) in photo-excited Auger decay is presented. A simple analytical expression is obtained by using complex WKB wave functions for the slow electron. The model gives the right asymtotic line-shape at high excess energies and the energy shift of the peak maximum is in agreement with experimental results. New high resolution argon LMM Auger spectra excited by electrons at different excess energies (4.5-2751.0 eV) relative the L3 level in Ar are presented. Extra structures are observed at low excess energies and are tentatively interpreted to be caused by shake-down processes of the slow electron. The relative shifts between Kr M5N2,3N2,3(1S 0) and Ar L3M2,3M2,3(1D 2) lines are measured and tabulated. The full widths and the asymmetry parameters at half and quarter maximum are also given.

Measuring the cache interference cost in preemptive real-time systems

Caches exploits locality of references to reduce memory access latencies and thereby improve processor performance. When an operating system switches application task or performs other kernel services, the assumption of locality may be violated because the instructions and data may no longer be in the cache when the preempted operation is resumed. Thus, these operations have an additional cache interference cost that must be taken into account when calculating or estimating the performance and responsiveness of the system.In this paper we present a simulation framework suitable for examining the cache interference cost in preemptive real-time systems. Using this framework we measure the interference cost for operating system services and a set of embedded benchmarks.The simulations show that there are a significant performance gap between the best- and worst case execution times even for simple hardware architectures. Also, the worst-case performance of some software modules was found to be more or less independent of the cache configuration. These results can be used to get a better understanding of the execution behavior of preemptive real-time systems and can serve as guidelines for choosing suitable cache configurations.

Intuitive industrial robot programming through incremental multimodal language and augmented reality

Developing easy to use, intuitive interfaces is crucial to introduce robotic automation to many small medium sized enterprises (SMEs). Due to their continuously changing product lines, reprogramming costs exceed installation costs by a large margin. In addition, traditional programming methods for industrial robots is too complex for an inexperienced robot programmer, thus external assistance is often needed. In this paper a new incremental multimodal language, which uses augmented reality (AR) environment, is presented. The proposed language architecture makes it possible to manipulate, pick or place the objects in the scene. This approach shifts the focus of industrial robot programming from coordinate based programming paradigm, to object based programming scheme. This makes it possible for non-experts to program the robot in an intuitive way, without going through rigorous training in robot programming.

Multi-level project work; a study in collaboration

This is a description of our latest effort to find new education forms. We have a long experience with running large projects (Daniels and Asplund, 1999), but wanted to expand the concept into an interdisciplinary setting. By combing three different student groups we have been able to formulate a project aiming at building robots from scratch that will participate in the robot soccer championships. This complex project resembles a realistic industry development that covers the, for us, usual computer science aspect, as well as interfacing with electronic hardware and mechanical construction.

GIMME - A General Image Multiview Manipulation Engine

This paper presents GIMME (General Image Multiview Manipulation Engine), a highly flexible reconfigurable stand-alone mobile two-camera vision platform with stereo-vision capability. GIMME relies on reconfigurable hard-ware (FPGA) to perform application-specific low to medium-level image-processing at video-rate. The Qseven-extension enables additional processing power. Thanks to its compact design, low power consumption and standardized interfaces (power and communication), GIMME is an ideal vision platform for autonomous and mobile robot applications.