Interaction of molecular nitrogen with Free-Electron-Laser radiation

We compute molecular continuum orbitals in the single center expansion scheme. We then employ these orbitals to obtain molecular Auger rates and single-photon ionization cross sections to study the interaction of N2 with Free-Electron-Laser (FEL) pulses. The nuclei are kept fixed. We formulate rate equations for the energetically allowed molecular and atomic transitions and we account for dissociation through additional terms in the rate equations. Solving these equations for different parameters of the FEL pulse, allows us to identify the most efficient parameters of the FEL pulse for obtaining the highest contribution of double core hole states (DCH) in the final atomic ion fragments. Finally we identify the contribution of DCH states in the electron spectra and show that the DCH state contribution is more easily identified in the photo-ionization rather than the Auger transitions

Atomic oxygen studies on polymers

The purpose was to study the effects of atomic oxygen on the erosion of polymer based materials. The development of an atomic oxygen neutral beam facility using a SURFATRON surface wave launcher that can produce beam energies between 2 and 3 eV at flux levels as high as approx. 10 to the 17th power atoms/cm (2)-sec is described. Thin film dielectric materials were studied to determine recession rates and and reaction efficiencies as a function of incident beam energy and fluence. Accelerated testing was also accomplished and the values of reaction efficiency compared to available space flight data. Electron microscope photomicrographs of the samples' surface morphology were compared to flight test specimens

Extraction efficiency of drifting electrons in a two-phase xenon time projection chamber

We present a measurement of the extraction efficiency of quasi-free electrons from the liquid into the gas phase in a two-phase xenon time-projection chamber. The measurements span a range of electric fields from 2.4 to 7.1 kV/cm in the liquid xenon, corresponding to 4.5 to 13.1 kV/cm in the gaseous xenon. Extraction efficiency continues to increase at the highest extraction fields, implying that additional charge signal may be attained in two-phase xenon detectors through careful high-voltage engineering of the gate-anode region

Uncertainty Estimates for Theoretical Atomic and Molecular Data

Sources of uncertainty are reviewed for calculated atomic and molecular data that are important for plasma modeling: atomic and molecular structure and cross sections for electron-atom, electron-molecule, and heavy particle collisions. We concentrate on model uncertainties due to approximations to the fundamental many-body quantum mechanical equations and we aim to provide guidelines to estimate uncertainties as a routine part of computations of data for structure and scattering.Comment: 65 pages, 18 Figures, 3 Tables. J. Phys. D: Appl. Phys. Final accepted versio

Why SF6 eats electrons: identifying high electrical strength molecules from their electron collision properties

The electrical strength of a molecule is a measure of its ability to act as an insulator and to absorb electrons. SF6 is a high electric strength gas. This work tries to explain why molecules like SF6 have a high electrical strength from the perspective of electron molecule scattering. The presence of a very low energy (<<1 eV) totally symmetric state in form of a very low-lying resonance, virtual state or very weakly bound state appears to be crucial. R-matrix calculations performed at the static exchange plus polarisation (SEP) level are performed for a number of molecules that show a range of electrical strengths. SEP calculations suggest that SF6 has a strong low energy 2Ag resonance feature which becomes a weakly bound state as more virtual orbitals are included in the calculation. High electrical strength molecules such as CCl4, CCl3F and CCl2F2 also have a totally-symmetric low-energy resonance, while the low electrical strength molecules such as CH4, CH3F...CF4 and CClF3, do not show any resonance behaviour in the low energy region. It is suggested that this low energy feature can be used as an indicator when searching for new molecules with high electrical strength facilitating searches for new gases which could provide an alternative to SF6

The Effect of Aortic Valve Replacement on Left Ventricular Function in Patients with Aortic Valvular Disease

Despite improved surgical techniques and survival in patients following aortic valve replacement for aortic stenosis and aortic insufficiency, the proper timing for surgery remains controversial. The incomplete reversibility of left ventricular dysfunction remains a concern, and postoperative improvement of left ventricular function is not consistently demonstrated. We studied 11 patients with aortic stenosis and nine patients with aortic insufficiency using angiographic and radioisotope assessment of left ventricular function preoperatively. Postoperative left ventricular function was assessed over nine to 13 months by radioisotope multiple-gated acquisition (MUGA) scan. All patients with impaired left ventricular function preoperatively showed slow but significant recovery toward a normal left ventricular ejection fraction by nine to 13 months postoperatively. Patients with aortic stenosis or aortic insufficiency and depressed left ventricular function can clearly obtain substantial, albeit delayed, improvement after valve replacement

Electron Scattering Cross Sections for Anthracene and Pyrene

UK molecular R-matrix calculations have been carried out for electron scattering from anthracene and pyrene. These molecules belong to the family of polycyclic hydrocarbons (PAHs) and are found in a nebula known as the Red Rectangle. Static exchange (SE), static exchange plus polarization (SEP), and close coupling (CC) approximations are used for scattering calculations. Different elastic and inelastic cross sections are computed in the present work in the energy range of 0.1-15 eV. Dissociative electron attachment cross sections are also calculated for both the molecules. Various shape, Feshbach/core-excited, and mixed resonances are detected for these molecules below 10 eV. All of the resonances detected in the present study are in agreement with the existing experimental and theoretical results. Due to the complexity of the present targets, electron collision cross sections are essentially unknown and hence most of the results are presented for the first time