A5046154781- Atomic and Molecular Physics
- Muon and positron interactions and applications
- X-ray Spectroscopy and Fluorescence Analysis
- Advanced Chemical Physics Studies
- Atomic and Subatomic Physics Research
- Laser-induced spectroscopy and plasma
- Nuclear Physics and Applications
- Particle accelerators and beam dynamics
- Chemical Reactions and Isotopes
- Dark Matter and Cosmic Phenomena
- Mass Spectrometry Techniques and Applications
- Spectroscopy and Laser Applications
- Inorganic Fluorides and Related Compounds
- Plasma Diagnostics and Applications
- Quantum, superfluid, helium dynamics
- Electron and X-Ray Spectroscopy Techniques
- Astro and Planetary Science
- Laser-Matter Interactions and Applications
- Astrophysics and Star Formation Studies
- Photocathodes and Microchannel Plates
- Neutrino Physics Research
- Laser-Plasma Interactions and Diagnostics
- Particle Detector Development and Performance
- High-Energy Particle Collisions Research
- Chemical Analysis and Environmental Impact
Australian National University
2015-2025
Wright-Patterson Air Force Base
2021
U.S. Air Force Institute of Technology
2021
European Organization for Nuclear Research
2016
Max Planck Institute for Physics
2014
Jet Propulsion Laboratory
2014
California Institute of Technology
2014
Hunter Water
2012
University of Nebraska–Lincoln
2006-2011
Abstract Characteristic for devices based on two-dimensional materials are their low size, weight and power requirements. This makes them advantageous use in space instrumentation, including photovoltaics, batteries, electronics, sensors light sources long-distance quantum communication. Here we present a comprehensive study combined radiation effects Earth’s atmosphere various these nanomaterials. Using theoretical modeling packages, estimate relevant levels then expose field-effect...
Measurements of total scattering by positron impact have typically excluded a significant portion the forward angles differential cross section. This paper demonstrates effect that this can on measurements We show much apparent disagreement between experimental from atoms and molecules may be explained angular range. It is shown same also lead to an anomalous energy dependence some sections.
New acceleration technology is mandatory for the future elucidation of fundamental particles and their interactions. A promising approach to exploit properties plasmas. Past research has focused on creating large-amplitude plasma waves by injecting an intense laser pulse or electron bunch into plasma. However, maximum energy gain electrons accelerated in a single stage limited driver. Proton bunches are most drivers wakefields accelerate TeV scale stage. An experimental program at CERN—the...
High-resolution measurements of positron interactions with Ne and Ar are presented, as well theoretical treatments. The data extend over a range 0.3 to 60 eV comprise the grand total, positonium formation, total minus positronium formation cross sections. Theoretical treatments scattering from performed under relativistic optical potential approach, calculations using convergent close-coupling method. Comparisons present theories made previous experimental work.
We present total, elastic, and inelastic cross sections for positron electron scattering from tetrahydrofuran (THF) in the energy range between 1 5000 eV. Total (TCS), positronium formation sections, summed integral (ICS) electronic excitations direct ionization, as well elastic differential (DCS) at selected incident energies, have been measured collisions with THF. The beam used to carry out these experiments had an resolution 40–100 meV (full-width half-maximum). also TCS results THF...
We present in this study a self-consistent set of scattering cross sections for positron collisions with water molecules, the energy range 0.1–10 000 eV, prime motivation being to provide data modelling purposes. The structure database is based on new model potential calculation, including interference terms, which provides differential and integral elastic as well inelastic molecules over whole considered here. Experimental theoretical available literature have been integrated into after...
Utilising a high-resolution, trap-based positron beam, we have measured both elastic and inelastic scattering of positrons from water vapour. The measurements comprise differential elastic, total (not including positronium formation) absolute cross sections. energy range investigated is 1 eV to 60 eV. Comparison with theory made R-Matrix distorted wave calculations, our own application the Independent Atom Model for interactions.
Cross sections for positron scattering from krypton have been measured with an energy resolution of \ensuremath{\sim}60 meV over the range 0.5--60 eV. Absolute values grand total (${\ensuremath{\sigma}}_{\mathrm{GT}}$), positronium formation (${\ensuremath{\sigma}}_{\mathrm{Ps}}$), and minus (${\ensuremath{\sigma}}_{\mathrm{GT}}\ensuremath{-}{\ensuremath{\sigma}}_{\mathrm{Ps}}$,) cross are presented. Theoretical estimations ${\ensuremath{\sigma}}_{\mathrm{GT}}$...
We present results for total and partial cross sections positron scattering from H${}_{2}$. The positronium formation are reported between 0.5 200 eV. Total quasielastic inelastic energies the threshold 50 eV, with differential at 1, 3, 5, 7, 10 Our compared previous work, both experimental theoretical, particular attention paid to region below threshold, where there apparent discrepancies in work. A discussion of possible reasons this work is presented, including a focus on known systematic...
The emission of mixed inert/reactive gas plasmas, commonly used in a variety industrial applications and laboratory settings, is relatively unquantified the vacuum ultraviolet (VUV) wavelength range. VUV spectroscopy H2:Ar/Ne/He inductively coupled radio frequency (RF) plasmas was conducted for pressures range 20–80 mTorr with 400 W input RF power H2 concentrations 0% to 100%. For H2:Ar mixtures at 80 mTorr, Ly-α (121 nm) observed reach maximum 27.5% H2: 72.5%Ar, approximately 3.3 × greater...
In the present work we report on our experimental total cross section and positronium formation cross-section results for positron scattering from pyrimidine energies 1 to 180 eV. addition, inelastic integral sections (for electronic excitations plus direct ionization) have been measured up 21.5 We also quasi-elastic differential at Our are compared recent theoretical data scattering, as well electron this target.
Low-energy interactions of positrons with xenon have been studied both experimentally and theoretically. The experimental measurements were carried out using a trap-based positron beam an energy resolution ∼80 meV, while the theoretical calculations convergent close-coupling method relativistic optical potential approach. Absolute values grand total, positronium formation total minus cross sections are presented over range 1–60 eV. Elastic differential (DCS), for selected energies, also...
Measurements of the grand total and positronium formation cross sections for positron scattering from uracil have been performed energies between 1 180 eV, using a trap-based beam apparatus. Angular, quasi-elastic differential section measurements at 1, 3, 5, 10, 20 eV are also presented discussed. These compared to existing experimental results theoretical calculations, including our own calculations variant independent atom approach.
Abstract In an effort to aid the modelling of positron and positronium (Ps) transport in biological media we have compiled recent experimental results for total Ps formation scattering from atoms molecules. A simple function was found adequately describe cross section both The parameters this magnitude shape are compared physical characteristics target general trend is observed as a atom/molecule dipole polarisability. functional form may enable quick estimation molecules which measurements...
Channel coupling is a phenomenon that has been investigated for many scattering processes, and responsible the formation of cusps or steps in cross sections open channels at, near, onset new channel. It long speculated opening positronium channel may lead to such cusp features elastic positron section. In this work, positrons measured region threshold noble gases He-Xe. Cusplike behavior observed and, while which are appear broad, they represent magnitude between 4 15% total No evidence...
Cross section results from a joint experimental and theoretical investigation into positron scattering 3-hydroxy-tetrahydrofuran (3H-THF) are presented. Total positronium (Ps) formation cross sections have been measured 1 to 190 eV using the beamline at Australian National University, which has an energy resolution between 60 100 meV. The total (TCS) elastic inelastic integral in range 1000 computed within Independent Atom Model Screening Corrected Additivity Rule approach. In addition, we...
Absolute single- and double-charge-exchange cross sections for the astrophysically prominent ${\mathrm{O}}^{6+}$ ion with atomic molecular targets He ${\mathrm{H}}_{2}$ are reported. These collisions give rise to x-ray emissions in interplanetary medium, planetary atmospheres, comets as they approach sun. Measurements have been carried out using Caltech Jet Propulsion Laboratory electron cyclotron resonance source at energies of 1.17 2.33 keV/u characteristic slow fast components solar wind....
We have measured the production of both Lyα and Hα fluorescence from atomic H D for photodissociation H2 D2 by linearly polarized photons with energies between 24 60 eV. In this energy range, excited photofragments result primarily doubly molecular species which promptly autoionize or dissociate into two neutrals. Our data are compared ab initio calculations dissociation process, in state prompt ionization (non-resonant) channels considered. Agreement our experimental that earlier work,...
We describe a simple and versatile method to manipulate the amplitude of magnetron orbit ions stored in Penning trap, applied here cloud low energy positrons. By applying pulsed voltage split electrode which is normally used for rotating wall compression particles, size can be changed at will. The modified has been shown stable many periods. technique could find use applications require off-axis ejection instance filling arrays traps multicell positron storage.
We present a range of cross section measurements for the low-energy scattering positrons from pyridine, incident positron energies less than 20 eV, as well independent atom model with screening corrected additivity rule including interference effects calculation, dipole rotational excitations accounted using Born approximation. Comparisons are made between experimental and theoretical calculations. For positronium formation section, we also compare results recent empirical model. In general,...
Consolidation of pure molybdenum through laser powder bed fusion and other additive manufacturing techniques is complicated by a high melting temperature, thermal conductivity ductile-to-brittle transition temperature. Nano-sized SiC particles (0.1 wt%) were homogeneously mixed with the printing characteristics, chemical composition, microstructure, mechanical properties compared to for scan speeds 100, 200, 400, 800 mm/s. The addition improved optically determined density flexural strength...
Recent calculations by Bromley et al. [Phys. Rev. Lett. 109, 063201 (2012)] have indicated that the He(2${s}^{2}{\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{S}^{e}$) state will bind a positron. The ${e}^{+}$He(2${s}^{2}{\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{S}^{e}$) has binding energy of 0.447 eV with respect to state. Binding positron He 2${s}^{2}$ been predicted give rise two resonances in scattering from ground-state helium: at 57.3716 and...
We have measured the production of Lyman α and Balmer fluorescence from atomic H D for photodissociation H2, HD D2 by linearly-polarized photons with energies between 22 64 eV. discuss systematic uncertainties associated our data, compare results previous experimental ab initio calculations dissociation process. comment on discrepancies.
Relevant to modeling and understanding X-ray emission from cometary planetary atmospheres, total cross-sections for 1.17 2.33 keV/u O6+ colliding with H2O, CO, CO2, CH4, N2, NO, N2O, Ar have been measured the processes of single, double, triple charge exchanges. Using these measurements as benchmarks, synthetic spectra spanning X-ray, UV, visible range calculated based on theoretical treatment transfer between one six electrons target neutrals projectile ion, followed by radiative...