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S W J Scully

Other affiliations: Queen's University Belfast
Bio: S W J Scully is an academic researcher from University of Nevada, Reno. The author has contributed to research in topics: Photoionization & Electron shell. The author has an hindex of 16, co-authored 26 publications receiving 670 citations. Previous affiliations of S W J Scully include Queen's University Belfast.

Papers
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Journal ArticleDOI
TL;DR: Time-dependent density functional calculations confirm the collective nature of this feature, which is characterized as a dipole-excited volume plasmon made possible by the special fullerene geometry.
Abstract: Neutral C60 is well known to exhibit a giant resonance in its photon absorption spectrum near 20 eV. This is associated with a surface plasmon, where delocalized electrons oscillate as a whole relative to the ionic cage. Absolute photoionization cross-section measurements for C+60, C2+60, and C3+60 ions in the 17-75 eV energy range show an additional resonance near 40 eV. Time-dependent density functional calculations confirm the collective nature of this feature, which is characterized as a dipole-excited volume plasmon made possible by the special fullerene geometry.

111 citations

Journal Article
TL;DR: In this article, a dipole-excited volume plasmon made possible by the special fullerene geometry is characterized as dipole excitation in the photon absorption spectrum of neutral C60.
Abstract: Neutral C60 is well known to exhibit a giant resonance in its photon absorption spectrum near 20 eV. This is associated with a surface plasmon, where delocalized electrons oscillate as a whole relative to the ionic cage. Absolute photoionization cross-section measurements for C+60, C2+60, and C3+60 ions in the 17-75 eV energy range show an additional resonance near 40 eV. Time-dependent density functional calculations confirm the collective nature of this feature, which is characterized as a dipole-excited volume plasmon made possible by the special fullerene geometry.

96 citations

Journal ArticleDOI
TL;DR: In this paper, the lifetime of the 1s2s 2 2p 22 D, 2 P and 2 S autoionizing states of C + was determined by measurement of the natural linewidth.
Abstract: Lifetimes for K-shell vacancy states in atomic carbon have been determined by measurement of the natural linewidth of the 1s → 2p photoexcited states of C + ions. The K-shell vacancy states produced by photoionization of atomic carbon are identical to those produced by 1s → 2p photoexcitation of a C + ion: 1s2s 2 2p 22 D, 2 P, and 2 S autoionizing states occur in both cases. These vacancy states stabilize by emission of an electron to produce C 2+ ions. Measurements are reported for the lifetime of the 1s2s 2 2p 22 D, 2 P and 2 S autoionizing states of C + :6 .3± 0.9 fs, 11.2 ± 1.1 fs and 5.9 ± 1.3 fs respectively. Knowledge of such lifetimes is important for comparative studies of the lifetimes of Kshell vacancies in carbon-containing molecules, benchmarking theory, and interpreting satellite x-ray spectra from astrophysical sources such as x-ray binaries. Absolute cross sections were measured for both ground-state and metastable-state ions providing a stringent test of state-of-the-art theoretical calculations. Carbon is ubiquitous in nature and is the building block of life. This atom in its various stages of ionization has relatively few electrons, and is thus amenable to theoretical study. Lifetimes

52 citations

Journal ArticleDOI
TL;DR: The absolute cross-section measurements for resonant double photoexcitation of Li + ions followed by autoionization have been performed at high resolution in the photon energy range from 148 eV, just below the 2s2p, 2(0, 1) + resonance, to 198 eV (the region of the double ionization threshold) as discussed by the authors.
Abstract: Absolute cross-section measurements for resonant double photoexcitation of Li + ions followed by autoionization have been performed at high resolution in the photon energy range from 148 eV, just below the 2s2p, 2(0, 1) + resonance, to 198 eV (the region of the double ionization threshold). The measurements have been made using the photon–ion merged-beam endstation at the Advanced Light Source, Lawrence Berkeley National Laboratory, USA. The absolute cross-section measurements show excellent agreement with theoretical results from the R-matrix plus pseudo-state (RMPS) method. Comparisons between theory and experiment for the Auger resonance energies, autoionization linewidth (� ) and the Fano line profile index q for several members of the principal 2snp, 2(0, 1) + and 3snp, 3(1, 1) + Rydberg series found in the photoionization spectra for the 1 P o symmetry show satisfactory accord. (Some figures in this article are in colour only in the electronic version)

41 citations

Journal ArticleDOI
TL;DR: In this paper, absolute cross-section measurements for K-shell photoionization of Be-like C2+ ions have been performed in the photon energy range 292 325 eV.
Abstract: Absolute cross-section measurements for K-shell photoionization of Be-like C2+ ions have been performed in the photon energy range 292 325 eV. These measurements have been made using the photon ion merged-beam endstation at the Advanced Light Source, Lawrence Berkeley National Laboratory. Absolute measurements compared with theoretical results from the R-matrix method indicate that the primary C2+ ion beam consisted of 62 percent ground-state (1s22s2 1S) and 38 percent metastable state (1s22s2p 3Po) ions. Reasonable agreement is seen between theory and experiment for absolute photoionization cross sections, resonance energies and autoionization line widths of K-shell-vacancy Auger states.

39 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the authors developed a toolkit to treat detailed ionization, relaxation, and scattering dynamics for an atom within a consistent theoretical framework, and showed that the x-ray scattering intensity saturates at a fluence of $~${10}^{7}$ photon/\AA{}${}^{2}$ per pulse but can be maximized by using a pulse duration much shorter than the time scales involved in the relaxation of the inner-shell vacancy states created.
Abstract: X-ray free-electron lasers (FELs) are promising tools for structural determination of macromolecules via coherent x-ray scattering. During ultrashort and ultraintense x-ray pulses with an atomic-scale wavelength, samples are subject to radiation damage and possibly become highly ionized, which may influence the quality of x-ray scattering patterns. We develop a toolkit to treat detailed ionization, relaxation, and scattering dynamics for an atom within a consistent theoretical framework. The coherent x-ray scattering problem including radiation damage is investigated as a function of x-ray FEL parameters such as pulse length, fluence, and photon energy. We find that the x-ray scattering intensity saturates at a fluence of $~$${10}^{7}$ photon/\AA{}${}^{2}$ per pulse but can be maximized by using a pulse duration much shorter than the time scales involved in the relaxation of the inner-shell vacancy states created. Under these conditions, both inner-shell electrons in a carbon atom are removed, and the resulting hollow atom gives rise to a scattering pattern with little loss of quality for a spatial resolution $g1$ \AA{}. Our numerical results predict that in order to scatter from a carbon atom 0.1 photon per x-ray pulse, within a spatial resolution of 1.7 \AA{}, a fluence of $1\ifmmode\times\else\texttimes\fi{}{10}^{7}$ photons/\AA{}${}^{2}$ per pulse is required at a pulse length of 1 fs and a photon energy of 12 keV. By using a pulse length of a few hundred attoseconds, one can suppress even secondary ionization processes in extended systems. The present results suggest that high-brightness attosecond x-ray FELs would be ideal for single-shot imaging of individual macromolecules.

169 citations

Journal ArticleDOI
TL;DR: The International Symposium on Atomic Cluster Collisions (ISSAC) as mentioned in this paper is the premier forum to present cutting-edge research in this field, and it was established in 2003 and held in Berlin, Germany in July of 2011.
Abstract: Atomic cluster collisions are a field of rapidly emerging research interest by both experimentalists and theorists. The international symposium on atomic cluster collisions (ISSAC) is the premier forum to present cutting-edge research in this field. It was established in 2003 and the most recent conference was held in Berlin, Germany in July of 2011. This Topical Issue presents original research results from some of the participants, who attended this conference. This issues specifically focuses on two research areas, namely Clusters and Fullerenes in External Fields and Nanoscale Insights in Radiation Biodamage.

152 citations

01 Oct 1999
TL;DR: In this article, the authors describe version 90 (C90) of the code, paying particular attention to changes in the atomic database and numerical methods that have affected predictions since the last publicly available version, C84.
Abstract: ABSTRACT CLOUDY is a large‐scale spectral synthesis code designed to simulate fully physical conditions within an astronomical plasma and then predict the emitted spectrum. Here we describe version 90 (C90) of the code, paying particular attention to changes in the atomic database and numerical methods that have affected predictions since the last publicly available version, C84. The computational methods and uncertainties are outlined together with the direction future development will take. The code is freely available and is widely used in the analysis and interpretation of emission‐line spectra. Web access to the Fortran source for CLOUDY, its documentation Hazy, and an independent electronic form of the atomic database is also described.

111 citations

Journal ArticleDOI
TL;DR: X-ray-initiated isomerization of acetylene, a model for proton dynamics in hydrocarbons, is studied to conclude that significant proton motion occurs on a timescale comparable to the Auger relaxation that refills the K-shell vacancy.
Abstract: Proton migration in the acetylene cation is commonly used as a model to study isomerisation dynamics. Here, the authors use X-ray pump-probe experiments to study this process, and show that isomerization occurs significantly faster than expected—within the first 12 femtoseconds following core ionization.

104 citations

Journal Article
TL;DR: In this article, a dipole-excited volume plasmon made possible by the special fullerene geometry is characterized as dipole excitation in the photon absorption spectrum of neutral C60.
Abstract: Neutral C60 is well known to exhibit a giant resonance in its photon absorption spectrum near 20 eV. This is associated with a surface plasmon, where delocalized electrons oscillate as a whole relative to the ionic cage. Absolute photoionization cross-section measurements for C+60, C2+60, and C3+60 ions in the 17-75 eV energy range show an additional resonance near 40 eV. Time-dependent density functional calculations confirm the collective nature of this feature, which is characterized as a dipole-excited volume plasmon made possible by the special fullerene geometry.

96 citations