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Sample records for 4d photoionization states

  1. Attosecond delay of xenon 4 d photoionization at the giant resonance and Cooper minimum

    NASA Astrophysics Data System (ADS)

    Magrakvelidze, Maia; Madjet, Mohamed El-Amine; Chakraborty, Himadri S.

    2016-07-01

    A Kohn-Sham time-dependent local-density-functional scheme is utilized to predict attosecond time delays of xenon 4 d photoionization that involves the 4 d giant dipole resonance and Cooper minimum. The fundamental effect of electron correlations to uniquely determine the delay at both regions is demonstrated. In particular, for the giant dipole resonance, the delay underpins strong collective effect, emulating the recent prediction at C60 giant plasmon resonance [T. Barillot et al., Phys. Rev. A 91, 033413 (2015), 10.1103/PhysRevA.91.033413]. For the Cooper minimum, a qualitative similarity with a photorecombination experiment near argon 3 p minimum [S. B. Schoun et al., Phys. Rev. Lett. 112, 153001 (2014), 10.1103/PhysRevLett.112.153001] is found. The result should encourage attosecond measurements of Xe 4 d photoemission.

  2. Dynamical Relativistic Effects in Photoionization: Spin-Orbit-Resolved Angular Distributions of Xenon 4d Photoelectrons near the Cooper Minimum

    SciTech Connect

    Wang, H.; Snell, G.; Hemmers, O.; Sant'Anna, M. M.; Sellin, I.; Berrah, N.; Lindle, D. W.; Deshmukh, P. C.; Haque, N.; Manson, S. T.

    2001-09-17

    Two decades ago, it was predicted [Y.S.Kim et al., Phys.Rev.Lett.46, 1326 (1981)] that relativistic effects should alter the dynamics of the photoionization process in the vicinity of Cooper minima. The present experimental and theoretical study of the angular distributions of Xe 4d{sub 3/2} and 4d{sub 5/2} photoelectrons demonstrates this effect for the first time. The results clearly imply that relativistic effects are likely to be important for intermediate-Z atoms at most energies.

  3. Significant Redistribution of Ce 4d Oscillator Strength Observed in Photoionization of Endohedral Ce-C{sub 82}{sup +} Ions

    SciTech Connect

    Mueller, A.; Schippers, S.; Habibi, M.; Esteves, D.; Wang, J. C.; Phaneuf, R. A.; Kilcoyne, A. L. D.; Aguilar, A.; Dunsch, L.

    2008-09-26

    Mass-selected beams of atomic Ce{sup q+} ions (q=2, 3, 4), of C{sub 82}{sup +} and of endohedral Ce-C{sub 82}{sup +} ions were employed to study photoionization of free and encaged cerium atoms. The Ce 4d inner-shell contributions to single and double ionization of the endohedral Ce-C{sub 82}{sup +} fullerene have been extracted from the data and compared with expectations based on theory and the experiments with atomic Ce ions. Dramatic reduction and redistribution of the ionization contributions to 4d photoabsorption is observed. More than half of the Ce 4d oscillator strength appears to be diverted to the additional decay channels opened by the fullerene cage surrounding the Ce atom.

  4. Photoionization from excited states of helium

    NASA Technical Reports Server (NTRS)

    Jacobs, V. L.

    1973-01-01

    The cross sections for photoionization from the 2 1S, 2 3S, 2 1P and 2 3P excited states of helium are calculated for photoelectron energies below the n = 2 threshold of He(+) using Hylleraas bound state wave functions and 1s-2s-2p close coupling final state wave functions. The resonant structures associated with the lowest-lying 1S, 1P, 3P, and 1D autoionizing states of helium are found to be characterized by large values of the line profile parameter q. The cross sections and the photoelectron angular distribution asymmetry parameters for the P-states are calculated for various polarization states of the target atom and the incident photon. Experiments which would lead to the separate determinations of the S- and D- wave partial photoionization cross sections are discussed.

  5. Absolute Photoionization Cross Sections for Br2+ in the 4 p --> 4d and 3d --> 4p Energy Regions

    NASA Astrophysics Data System (ADS)

    Aguilar, A.; Juarez, A. M.; Bilodeau, R. C.; Esteves, D. A.; Hardy, D. A.; Red, E. C.

    2011-05-01

    Absolute single photoionization cross-section measurements are reported for Br2+ in the 31 eV to 46 eV and 64 eV to 72 eV photon energy ranges. The first energy range includes the low-lying 2P3 / 2 , 1 / 2 and 2D5 / 2 , 3 / 2 metastable state thresholds and extends for 10 eV above the 4S3 / 2 ground state threshold. Strong photoexcitation-autoionization resonances due to 4p --> nd transitions are seen in the cross-section spectrum and identified based on a quantum-defect analysis of the series. The systematic behavior of the quantum defect parameter of some of the Rydberg series observed in the Br2+ spectrum as well as in previously measured Se+ spectrum, are analyzed as a function of the nuclear charge. The 64 eV to 72 eV energy range contains discrete structure that arises from 3d --> np excitations. The R-matrix photoionization cross section calculations of Cummings and O'Sullivan, PRA, 54 (1996) are compared to our absolute cross section measurements in this energy range. Absolute single photoionization cross-section measurements are reported for Br2+ in the 31 eV to 46 eV and 64 eV to 72 eV photon energy ranges. The first energy range includes the low-lying 2P3 / 2 , 1 / 2 and 2D5 / 2 , 3 / 2 metastable state thresholds and extends for 10 eV above the 4S3 / 2 ground state threshold. Strong photoexcitation-autoionization resonances due to 4p --> nd transitions are seen in the cross-section spectrum and identified based on a quantum-defect analysis of the series. The systematic behavior of the quantum defect parameter of some of the Rydberg series observed in the Br2+ spectrum as well as in previously measured Se+ spectrum, are analyzed as a function of the nuclear charge. The 64 eV to 72 eV energy range contains discrete structure that arises from 3d --> np excitations. The R-matrix photoionization cross section calculations of Cummings and O'Sullivan, PRA, 54 (1996) are compared to our absolute cross section measurements in this energy range. This work is

  6. Fourier photospectroscopy of Xe@C60 in the Xe 4d giant resonance region: Testing the single-photoionization theory against recent measurements

    NASA Astrophysics Data System (ADS)

    Patel, Aakash; Chakraborty, Himadri

    2012-06-01

    We have developed a technique, based on Fourier-transforming cross sections to the reciprocal configuration space, to explore the electronic multiple interferences in the photoionization of endohedral fullerene molecules. Using this technique, the single photoionization cross section of endohedral Xe@C60 over Xe 4d giant resonance energy region, calculated in the time dependent local density approximation (TDLDA), is compared with recent double photoionization experimental data [1]. The analysis of oscillatory cross sections derives a number of inherent similarities between the prediction and the data, including a large beating-type oscillation and several others of intermediate size [2]. Results stress the need for more accurate measurements to access the wealth of information about the geometry of the system.[4pt] [1] A.L.D. Kilcoyne et al., Phys. Rev. Lett. 105, 213001 (2010);[0pt] [2] A.B. Patel and H.S. Chakraborty, J. Phys. B Fast Track Comm. 44, 191001 (2011).

  7. Photoionization of potassium atoms from the ground and excited states

    SciTech Connect

    Zatsarinny, O.; Tayal, S. S.

    2010-04-15

    The Dirac-based B-spline R-matrix method is used to investigate the photoionization of atomic potassium from the 4s ground and 4p, 5s-7s, 3d-5d excited states. The effect of the core polarization by the outer electron is included through the polarized pseudostates. Besides the dipole core polarization, we also found a noticeable influence of the quadrupole core polarization. We obtained excellent agreement with experiment for cross sections of the 4s photoionization, including accurate description of the near-threshold Cooper-Seaton minimum. We also obtained close agreement with experiment for the 4p photoionization, but there are unexpectedly large discrepancies with available experimental data for photoionization of the 5d and 7s excited states.

  8. Photoionization of ground and excited states of Ti I

    NASA Astrophysics Data System (ADS)

    Nahar, Sultana N.

    2015-07-01

    Detailed photoionization of ground and many excited states with autoionizing resonances of neutral Ti are presented. Ti I with 22 electrons forms a large number of bound states, the present work finds a total of 908 bound states with n ⩽ 10 and l ⩽ 8 . Photoionization cross sections (σPI) for all these bound states have been obtained. Calculations were carried out in the close-coupling R-matrix method using a wave function expansion that included 36 states of core ion Ti II. It is found that the resonances enhance the low energy region of photoionization of the ground and low lying excited states. The resonant features will increase the opacity, as expected of astrophysical observation, and hence play important role in determination of abundances in the elements in the astronomical objects. The excited states also show prominent structures of Seaton or photo-excitation-of-core resonances.

  9. Strong-Field Photoionization as Excited-State Tunneling.

    PubMed

    Serebryannikov, E E; Zheltikov, A M

    2016-03-25

    We show that, in an intense laser field, ultrafast photoionization can occur through quantum pathways that cannot be categorized as multiphoton ionization or ground-state tunneling. In this regime, the subcycle electron-wave-packet dynamics leading to photoionization occurs via electron excited states, from where the electrons tunnel to the continuum within a tiny fraction of the field cycle. For high field intensities, this ionization pathway is shown to drastically enhance the dynamic leakage of the electron wave packet into the continuum, opening an ionization channel that dominates over ground-state electron tunneling. PMID:27058079

  10. Two-electron photoionization of ground-state lithium

    SciTech Connect

    Kheifets, A. S.; Fursa, D. V.; Bray, I.

    2009-12-15

    We apply the convergent close-coupling (CCC) formalism to single-photon two-electron ionization of the lithium atom in its ground state. We treat this reaction as single-electron photon absorption followed by inelastic scattering of the photoelectron on a heliumlike Li{sup +} ion. The latter scattering process can be described accurately within the CCC formalism. We obtain integrated cross sections of single photoionization leading to the ground and various excited states of the Li{sup +} ion as well as double photoionization extending continuously from the threshold to the asymptotic limit of infinite photon energy. Comparison with available experimental and theoretical data validates the CCC model.

  11. Photoionization of furan from the ground and excited electronic states

    NASA Astrophysics Data System (ADS)

    Ponzi, Aurora; Sapunar, Marin; Angeli, Celestino; Cimiraglia, Renzo; Došlić, Nada; Decleva, Piero

    2016-02-01

    Here we present a comparative computational study of the photoionization of furan from the ground and the two lowest-lying excited electronic states. The study aims to assess the quality of the computational methods currently employed for treating bound and continuum states in photoionization. For the ionization from the ground electronic state, we show that the Dyson orbital approach combined with an accurate solution of the continuum one particle wave functions in a multicenter B-spline basis, at the density functional theory (DFT) level, provides cross sections and asymmetry parameters in excellent agreement with experimental data. On the contrary, when the Dyson orbitals approach is combined with the Coulomb and orthogonalized Coulomb treatments of the continuum, the results are qualitatively different. In excited electronic states, three electronic structure methods, TDDFT, ADC(2), and CASSCF, have been used for the computation of the Dyson orbitals, while the continuum was treated at the B-spline/DFT level. We show that photoionization observables are sensitive probes of the nature of the excited states as well as of the quality of excited state wave functions. This paves the way for applications in more complex situations such as time resolved photoionization spectroscopy.

  12. Photoionization of furan from the ground and excited electronic states.

    PubMed

    Ponzi, Aurora; Sapunar, Marin; Angeli, Celestino; Cimiraglia, Renzo; Došlić, Nađa; Decleva, Piero

    2016-02-28

    Here we present a comparative computational study of the photoionization of furan from the ground and the two lowest-lying excited electronic states. The study aims to assess the quality of the computational methods currently employed for treating bound and continuum states in photoionization. For the ionization from the ground electronic state, we show that the Dyson orbital approach combined with an accurate solution of the continuum one particle wave functions in a multicenter B-spline basis, at the density functional theory (DFT) level, provides cross sections and asymmetry parameters in excellent agreement with experimental data. On the contrary, when the Dyson orbitals approach is combined with the Coulomb and orthogonalized Coulomb treatments of the continuum, the results are qualitatively different. In excited electronic states, three electronic structure methods, TDDFT, ADC(2), and CASSCF, have been used for the computation of the Dyson orbitals, while the continuum was treated at the B-spline/DFT level. We show that photoionization observables are sensitive probes of the nature of the excited states as well as of the quality of excited state wave functions. This paves the way for applications in more complex situations such as time resolved photoionization spectroscopy. PMID:26931702

  13. Photoionization of Fe7+ from the ground and metastable states

    NASA Astrophysics Data System (ADS)

    Tayal, S. S.; Zatsarinny, O.

    2015-01-01

    The B -spline Breit-Pauli R -matrix method is used to investigate the photoionization of Fe7 + from the ground and metastable states in the energy region from ionization thresholds to 172 eV. The present calculations were designed to resolve the large discrepancies between recent measurements and available theoretical results. The multiconfiguration Hartree-Fock method in connection with B -spline expansions is employed for an accurate representation of the initial- and final-state wave functions. The close-coupling expansion includes 99 fine-structure levels of the residual Fe8 + ion in the energy region up to 3 s23 p54 s states. It includes levels of the 3 s23 p6,3 s23 p53 d ,3 s23 p54 s , and 3 s 3 p63 d configurations and some levels of the 3 s23 p43 d2 configuration which lie in the energy region under investigation. The present photoionization cross sections in the length and velocity formulations exhibit excellent agreement. The present photoionization cross sections agree well with the Breit-Pauli R -matrix calculation by Sossah et al. and the TOPbase data in the magnitude of the background nonresonant cross sections but show somewhat richer resonance structures, which qualitatively agree with the measurements. The calculated cross sections, however, are several times lower than the measured cross sections, depending upon the photon energy. The cross sections for photoionization of metastable states were found to have approximately the same magnitude as the cross sections for photoionization of the ground state, thereby the presence of metastable states in the ion beam may not be the reason for the enhancement of the measured cross sections.

  14. Photoionization dynamics of the C2+ ion in Rydberg states

    NASA Astrophysics Data System (ADS)

    Stancalie, Viorica

    2014-11-01

    The goal of this work is to examine in detail the ionization dynamics of Be-like C ion in Rydberg states. An initial calculation has been done to output the lifetime due to spontaneous decay for unperturbed 1s22sns (1Se) Rydberg states using the multi-configuration Dirac-Fock (MCDF) method with configuration interaction option implemented in the general-purpose relativistic atomic structure package (GRASP). Both the C2+ ground state and the C3+ target state energies have been carefully calculated. We report results from a detailed and systematic study of the behaviour of complex photoionization amplitudes, the lifetime due to spontaneous decay for unperturbed 1s22sns (1Se) Rydberg states, the `resonant' phase shift and the rapidly increasing of this shift from well below to well above the resonance position. The sum-over-state method is used to calculate the static dipole polarizability, while the frequency-dependent polarizability values of C2+ ion in these Rydberg states are obtained from two-state model calculation results. Contribution to the Topical Issue "Elementary Processes with Atoms and Molecules in Isolated and Aggregated States", edited by Friedrich Aumayr, Bratislav Marinkovic, Stefan Matejcik, John Tanis and Kurt H. Becker.

  15. Laser-induced photoionization of molecular hydrogen: A technique to measure revibrational ground state populations

    NASA Astrophysics Data System (ADS)

    Marinero, E. E.; Rettner, C. T.; Zare, R. N.

    1982-09-01

    Using tunable anti-Stokes orders of a frequency-doubled dye laser, rotationally-selective excited-state populations in H2 are prepared by two-photon excitation. The ensuing photoionization allows direct determination of (v'', J'') populations.

  16. State-to-state spectroscopy and dynamics of ions and neutrals by photoionization and photoelectron methods.

    PubMed

    Ng, Cheuk-Yiu

    2014-01-01

    Recent advances in high-resolution photoionization, photoelectron, and photodissociation studies based on single-photon vacuum ultraviolet (VUV) and two-color infrared (IR)-VUV, visible (Vis)-ultraviolet (UV), and VUV-VUV laser excitations are illustrated with selected examples. VUV laser photoionization coupled with velocity-map-imaging threshold photoelectron (VMI-TPE) detection can achieve comparable energy resolution but has higher-detection sensitivities than those observed in VUV laser pulsed field ionization photoelectron (PFI-PE) measurements. For molecules with known intermediate states, IR-VUV and Vis-UV excitation schemes are highly sensitive for rovibronically selected and resolved PFI-PE studies. The successful applications of the VUV-PFI-PE, VUV-VMI-TPE, and Vis-UV-PFI-PE methods to state-resolved and state-to-state photoelectron studies of transient radicals and transitional metal-containing molecules are highlighted. The most recently established VUV-VUV pump-probe time-slice VMI photoion method is shown to be promising for state-to-state photodissociation studies of small molecules relevant to planetary atmospheres and for the fundamental understanding of photodissociation dynamics. PMID:24328445

  17. State-to-State Spectroscopy and Dynamics of Ions and Neutrals by Photoionization and Photoelectron Methods

    NASA Astrophysics Data System (ADS)

    Ng, Cheuk-Yiu

    2014-04-01

    Recent advances in high-resolution photoionization, photoelectron, and photodissociation studies based on single-photon vacuum ultraviolet (VUV) and two-color infrared (IR)-VUV, visible (Vis)-ultraviolet (UV), and VUV-VUV laser excitations are illustrated with selected examples. VUV laser photoionization coupled with velocity-map-imaging threshold photoelectron (VMI-TPE) detection can achieve comparable energy resolution but has higher-detection sensitivities than those observed in VUV laser pulsed field ionization photoelectron (PFI-PE) measurements. For molecules with known intermediate states, IR-VUV and Vis-UV excitation schemes are highly sensitive for rovibronically selected and resolved PFI-PE studies. The successful applications of the VUV-PFI-PE, VUV-VMI-TPE, and Vis-UV-PFI-PE methods to state-resolved and state-to-state photoelectron studies of transient radicals and transitional metal-containing molecules are highlighted. The most recently established VUV-VUV pump-probe time-slice VMI photoion method is shown to be promising for state-to-state photodissociation studies of small molecules relevant to planetary atmospheres and for the fundamental understanding of photodissociation dynamics.

  18. GaAs-oxide interface states - A gigantic photoionization effect and its implications to the origin of these states

    NASA Technical Reports Server (NTRS)

    Lagowski, J.; Walukiewicz, W.; Kazior, T. E.; Gatos, H. C.; Siejka, J.

    1981-01-01

    Gigantic photoionization was discovered on GaAs-oxide interfaces leading to the discharge of deep surface states with rates exceeding 1000 times those of photoionization transitions to the conduction band. It exhibits a peak similar to acceptor-donor transitions and is explained as due to energy transfer from photo-excited donor-acceptor pairs to deep surface states. This new process indicates the presence of significant concentrations of shallow donor and acceptor levels not recognized in previous interface models.

  19. Charge-state distribution and Doppler effect in an expanding photoionized plasma.

    PubMed

    Foord, M E; Heeter, R F; van Hoof, P A M; Thoe, R S; Bailey, J E; Cuneo, M E; Chung, H-K; Liedahl, D A; Fournier, K B; Chandler, G A; Jonauskas, V; Kisielius, R; Mix, L P; Ramsbottom, C; Springer, P T; Keenan, F P; Rose, S J; Goldstein, W H

    2004-07-30

    The charge state distributions of Fe, Na, and F are determined in a photoionized laboratory plasma using high resolution x-ray spectroscopy. Independent measurements of the density and radiation flux indicate unprecedented values for the ionization parameter xi=20-25 erg cm s(-1) under near steady-state conditions. Line opacities are well fitted by a curve-of-growth analysis which includes the effects of velocity gradients in a one-dimensional expanding plasma. First comparisons of the measured charge state distributions with x-ray photoionization models show reasonable agreement.

  20. Photoionization with excitation and double photoionization of the Li{sup +} ground 1 {sup 1}S state and metastable 2 {sup 1,3}S states

    SciTech Connect

    Kleiman, U.; Pindzola, M.S.; Robicheaux, F.

    2005-08-15

    Partial cross-sections for photoionization with excitation of Li{sup +} leaving the remaining bound electron in the 1s, 2s, 2p, 3s, 3p, and 3d states and total cross-sections for double photoionization have been calculated employing the time-dependent close-coupling method. The calculations include both the ground state 1s{sup 2} {sup 1}S and the two lowest metastable excited states 1s2s {sup 1,3}S. Photon energies below and up to about 200 eV above the respective thresholds for double ionization are considered. Comparisons are drawn mainly with convergent close-coupling results [A. S. Kheifets and I. Bray, Phys. Rev. A 58, 4501 (1998)] and B-spline based R-matrix results [H. W. van der Hart and L. Feng, J. Phys. B 34, L601 (2001)].

  1. Highly Efficient State-Selective Submicrosecond Photoionization Detection of Single Atoms

    SciTech Connect

    Henkel, F.; Krug, M.; Hofmann, J.; Rosenfeld, W.; Weber, M.; Weinfurter, H.

    2010-12-17

    We experimentally demonstrate a detection scheme suitable for state analysis of single optically trapped atoms in less than 1 {mu}s with an overall detection efficiency {eta} exceeding 98%. The method is based on hyperfine-state-selective photoionization and subsequent registration of the correlated photoion-electron pairs by coincidence counting via two opposing channel electron multipliers. The scheme enables the calibration of absolute detection efficiencies and might be a key ingredient for future quantum information applications or precision spectroscopy of ultracold atoms.

  2. Photoionization from the 5p {sup 2}P{sub 3/2} state of rubidium

    SciTech Connect

    Nadeem, Ali; Haq, S. U.

    2011-06-15

    We report two-step photoionization studies from the 5p {sup 2}P{sub 3/2} excited state of rubidium using two dye lasers simultaneously pumped by a common Nd:YAG laser in conjunction with a thermionic diode ion detector. The photoionization cross section at the first ionization threshold is measured as 18.8 {+-} 3 Mb and at excess energies of 0.013, 0.106, 0.229, and 0.329 eV is measured as 15, 13.6, 12.6, and 12.5 Mb, respectively. The measured value of the photoionization cross section at the threshold is used to calibrate the oscillator strengths of the 5p {sup 2}P{sub 3/2}{yields}nd {sup 2}D{sub 5/2} (22 {<=}n{<=} 52) Rydberg transitions.

  3. Double photoionization of helium from the 1s2p {}^{3}{\\rm{P}} excited state

    NASA Astrophysics Data System (ADS)

    Li, Y.; Pindzola, M. S.; Colgan, J.

    2016-10-01

    Time-dependent close-coupling (TDCC) calculations are carried out for the double photoionization of Helium in the 1{{s}}2{{p}}{}3{{P}} excited state. TDCC {l}1{l}2L results are presented for the total and energy differential cross sections for the 1{{s}}2{{p}}{}3{{P}} term. TDCC {l}1{j}1{l}2{j}2J results are presented for the total and energy differential cross sections for the 1{{s}}2{{p}}{}3{{{P}}}{0,1,2} levels. Differences found between the level resolved double photoionization cross sections are due to varying degrees of continuum correlation found in the outgoing two electrons.

  4. Trauma-Related Altered States of Consciousness: Exploring the 4-D Model

    PubMed Central

    Frewen, Paul A.; Lanius, Ruth A.

    2014-01-01

    Frewen and Lanius (in press) recently articulated a 4-D model as a framework for classifying symptoms of posttraumatic stress into those that potentially occur within normal waking consciousness (NWC) versus those that intrinsically represent dissociative experiences of trauma-related altered states of consciousness (TRASC). Four dimensions were specified: time-memory, thought, body, and emotion. The 4-D model further hypothesizes that in traumatized persons, symptoms of TRASC, compared with NWC forms of distress, will be (a) observed less frequently; (b) less intercorrelated, especially as measured as moment-to-moment states; (c) observed more frequently in people with high dissociative symptomatology as measured independently; and (d) observed more often in people who have experienced repeated traumatization, particularly early developmental trauma. The aim of the present research was to begin to evaluate these 4 predictions of the 4-D model. Within a sample of 74 women with posttraumatic stress disorder (PTSD) primarily due to histories of childhood trauma, as well as within a 2nd sample of 504 undergraduates (384 females), the 1st 2 hypotheses of the 4-D model were supported. In addition, within the PTSD sample, the 3rd hypothesis was supported. However, inconsistent with the 4th hypothesis, severity of childhood trauma history was not strongly associated with TRASC. We conclude that the hypotheses articulated by the 4-D model were generally supported, although further research in different trauma-related disorders is needed, and the role of childhood trauma history in the etiology of TRASC requires further research. PMID:24650122

  5. Experimental study of 4f wavefunction contraction: 4d-photoionization of low-charged ions of I, Xe, Cs and Ba

    NASA Astrophysics Data System (ADS)

    Kjeldsen, H.; Andersen, P.; Folkmann, F.; Hansen, J. E.; Kitajima, M.; Andersen, T.

    2002-07-01

    The photon-ion merged beam technique has been used to measure the ionization cross sections of I-, Cs+, Ba+ and Ba2+ ions in the energy region from 40 to 185 eV, which is dominated by photoexcitation from the 4d shell (the experimental data are available at http:// www.ifa.au.dk/amo/atomphys/atomphys.htm). Within the experimental accuracy, the total oscillator strengths for these ions and for the I+, I2+, Xe+ and Xe2+ ions, that were recently studied by some of the present authors, are identical, with the contribution from the 4d → np or nf resonances becoming more important with increasing nuclear charge and ionization stage, and with the maximum value of the continuum cross section increasing as the nuclear number is enlarged. The present data support the assumption that the 4f wavefunctions contract gradually with increasing ionization, both along isonuclear and isoelectronic sequences, for ionic charges ranging from -1 to +2.

  6. Efficient representations of continuum states for photoionization processes from atomic and molecular targets

    NASA Astrophysics Data System (ADS)

    Yip, Frank L.

    The investigation of single and double photoionization effects in small atoms and molecules provides a means to probe fundamental quantum mechanical phenomena concerning electron correlation and interference effects. To consider these concepts accurately from first principles requires the construction of the exact final continuum states of a many body problem in atomic double photoionization and of the complicated continuum states in molecular single photoionization. Methods designed for incorporating exterior complex scaling (ECS) have proven very successful towards accomplishing these goals, providing a rigorous framework for describing continuum states involving any number of outgoing electrons with numerical exactness. Furthermore, such methods render solutions that can be interrogated to extract the full richness of information about the photoionization process from the wave function. This work aims to demonstrate the use of exterior complex scaling by first exactly solving the three-body breakup problem of the atomic hydride anion. H-- is the simplest atomic system and is most sensitive to electron correlation effects. The application of ECS with an efficient finite-element discrete variable representation proves quite capable and well-suited for this atomic Coulomb breakup problem. The evolution of this framework to treat molecular problems efficiently with exactness is furthered by the design of a hybrid basis method. The incorporation of analytic Gaussian basis sets ubiquitous in bound state molecular descriptions seems natural for considering molecular continuum states. The hybrid method is described in full detail and applied to completely describe photoionization of molecular H+2 and Li+2 . Photoionization of simple molecular systems offers significantly more complexity in the resulting angular distributions of the ejected electron as the target geometry becomes less atomic-like, i.e., as the internuclear separation increases. In this regard

  7. Measurement of the photoionization cross section of the 5S{sub 1/2} state of rubidium

    SciTech Connect

    Lowell, J.R.; Northup, T.; Patterson, B.M.; Takekoshi, T.; Knize, R.J.

    2002-12-01

    We report the measurement of the photoionization cross section for the 5S{sub 1/2} state of rubidium, using atoms confined in a magneto-optical trap. A single-photon rate at {lambda}=266 nm was found by monitoring the decay of trap fluorescence after exposure to ionizing radiation from a quadrupled Nd:YVO{sub 4} laser. In order to eliminate excited-state ionization, the photoionization and trapping lasers were alternately chopped, so that only ground-state atoms were ionized. We determine that the photoionization cross section at {lambda}=266 nm is {sigma}=1.7(2)x10{sup -20} cm{sup 2}.

  8. State-To Spectroscopy and Dynamics of Ions and Neutrals by Photoionization and Photoelectron Methods

    NASA Astrophysics Data System (ADS)

    Ng, Cheuk-Yiu

    2014-06-01

    Recent advances in high-resolution photoionization, photoelectron, and photodissociation studies based on single-photon vacuum ultraviolet (VUV) and two-color infrared (IR)-VUV, visible (VIS)-ultraviolet (UV), and VUV-VUV laser excitations are illustrated with selected examples. We show that VUV laser photoionization coupled with velocity-map-imaging (VMI)-threshold photoelectron (VMI-TPE) detection can achieve comparable energy resolutions, but higher detection sensitivities than those observed in VUV laser pulsed field ionization-photoelectron (PFI-PE) measurements. For molecules with known intermediate states, IR-VUV and VIS-UV excitation schemes are highly sensitive for rovibronically selected and resolved PFI-PE studies. The successful applications of the VUV-PFI-PE, VUV-VMI-TPE and VIS-UV-PFI-PE methods to state-resolved and state-to-state photoelectron studies of transient radicals and transitional metal-containing molecules are highlighted. The most recently established VUV-VUV pump-probe time-slice VMI-photoion method is shown to be promising for state-to-state photodissociation studies of small molecules relevant to planetary atmospheres and for the fundamental understanding of photodissociation dynamics.

  9. Photoionization cross section measurements of the excited states of cobalt in the near-threshold region

    SciTech Connect

    Zheng, Xianfeng Zhou, Xiaoyu; Cheng, Zaiqi; Jia, Dandan; Qu, Zehua; Yao, Guanxin; Zhang, Xianyi; Cui, Zhifeng

    2014-10-15

    We present measurements of photoionization cross-sections of the excited states of cobalt using a two-color, two-step resonance ionization technique in conjunction with a molecular beam time of flight (TOF) mass spectrometer. The atoms were produced by the laser vaporization of a cobalt rod, coupled with a supersonic gas jet. The absolute photoionization cross-sections at threshold and near-threshold regions (0-1.2 eV) were measured, and the measured values ranged from 4.2±0.7 Mb to 10.5±1.8 Mb. The lifetimes of four odd parity energy levels are reported for the first time.

  10. Real-Space Mapping of Surface Trap States in CIGSe Nanocrystals Using 4D Electron Microscopy.

    PubMed

    Bose, Riya; Bera, Ashok; Parida, Manas R; Adhikari, Aniruddha; Shaheen, Basamat S; Alarousu, Erkki; Sun, Jingya; Wu, Tom; Bakr, Osman M; Mohammed, Omar F

    2016-07-13

    Surface trap states in copper indium gallium selenide semiconductor nanocrystals (NCs), which serve as undesirable channels for nonradiative carrier recombination, remain a great challenge impeding the development of solar and optoelectronics devices based on these NCs. In order to design efficient passivation techniques to minimize these trap states, a precise knowledge about the charge carrier dynamics on the NCs surface is essential. However, selective mapping of surface traps requires capabilities beyond the reach of conventional laser spectroscopy and static electron microscopy; it can only be accessed by using a one-of-a-kind, second-generation four-dimensional scanning ultrafast electron microscope (4D S-UEM) with subpicosecond temporal and nanometer spatial resolutions. Here, we precisely map the collective surface charge carrier dynamics of copper indium gallium selenide NCs as a function of the surface trap states before and after surface passivation in real space and time using S-UEM. The time-resolved snapshots clearly demonstrate that the density of the trap states is significantly reduced after zinc sulfide (ZnS) shelling. Furthermore, the removal of trap states and elongation of carrier lifetime are confirmed by the increased photocurrent of the self-biased photodetector fabricated using the shelled NCs. PMID:27228321

  11. Photoionization cross section of image potential states around nanotubes

    NASA Astrophysics Data System (ADS)

    Bocan, G. A.; Segui, S.; Gervasoni, J. L.; Arista, N. R.

    2013-06-01

    In this paper, we theoretically address the photoemission from image potential states (IPS) around nanotubes. The relevance of this process is related to the fact that this particular kind of IPS has been experimentally detected for carbon nanotubes by means of femtosecond-resolved two-photon photoemission (Zamkov et al 2004 Phys. Rev. Lett. 93 156803). The quantum interaction between the bound electron and the incident radiation field is considered within the dipolar approximation, and the transition matrix for the process is obtained using a first-order Born expansion. For a linearly polarized photon with the polarization vector perpendicular to the nanotube's axis, electrons are found to be emitted with a polar angle that is determined by the initial parallel momentum of the bound electron.

  12. GaAs-oxide interface states - Gigantic photoionization via Auger-like process

    NASA Technical Reports Server (NTRS)

    Lagowski, J.; Kazior, T. E.; Gatos, H. C.; Walukiewicz, W.; Siejka, J.

    1981-01-01

    Spectral and transient responses of photostimulated current in MOS structures were employed for the study of GaAs-anodic oxide interface states. Discrete deep traps at 0.7 and 0.85 eV below the conduction band were found with concentrations of 5 x 10 to the 12th/sq cm and 7 x 10 to the 11th/sq cm, respectively. These traps coincide with interface states induced on clean GaAs surfaces by oxygen and/or metal adatoms (submonolayer coverage). In contrast to surfaces with low oxygen coverage, the GaAs-thick oxide interfaces exhibited a high density (about 10 to the 14th/sq cm) of shallow donors and acceptors. Photoexcitation of these donor-acceptor pairs led to a gigantic photoionization of deep interface states with rates 1000 times greater than direct transitions into the conduction band. The gigantic photoionization is explained on the basis of energy transfer from excited donor-acceptor pairs to deep states.

  13. Photoionization Dynamics and Ion State Distributions in Single-Photon and Resonance-Enhanced Multiphoton Ionization of Molecules.

    NASA Astrophysics Data System (ADS)

    Braunstein, Matthew

    This thesis presents results of theoretical studies of single-photon ionization and resonance enhanced multiphoton ionization (REMPI) of several small molecules. The first part of the thesis examines shape resonances in the photoionization of O_2. Studies reported here include investigations of branching ratios of electronic multiplet states in the 3sigma _{g} and 1pi_ {u} photoionization of O_2 and a comparison of photoionization of the singlet states, a ^1Delta_{g} and d ^1prod_{g } (3ssigma_{g} 1pi_{g}), with that of the ground state of O_2. These studies show that the electronic exchange interaction between the ion core and the photoelectron in shape resonant energy regions profoundly affects the electronic state distributions of the molecular ion. We also report vibrational branching ratios in the single-photon ionization of O_2 , and in REMPI of O_2 via the G^3prod_{g} Rydberg state. In these studies, we find that a shape resonance causes a dependence of the electronic transition moment on the molecular geometry leading to non-Franck -Condon ion vibrational distributions and a dependence of the rotational branch intensity on the ion vibrational state. The second part of this thesis examines shape resonances in other molecules, focusing on the more general aspects of the photoionization dynamics. Here we present studies of the vibrational state distributions in the 7 sigma photoionization of the polyatomic N_2O, where a shape resonance causes non-Franck-Condon vibrational state distributions, the degree of which depends on the nuclear displacements involved and whether the shape resonance is localized on a particular bond. We also study the photoionization dynamics of the valence shell of Cl_2, where a shape resonance is also seen. Finally, we present studies of the K-shell ionization of CO. Studies in this energy region have assumed a new importance with the development of tunable X-ray synchrotron sources. Here, electronic relaxation in the production of a K

  14. Communication: State-to-state photoionization and photoelectron study of vanadium methylidyne radical (VCH)

    SciTech Connect

    Luo, Zhihong; Zhang, Zheng; Huang, Huang; Chang, Yih-Chung; Ng, C. Y.

    2014-05-14

    By employing the infrared (IR)-ultraviolet (UV) laser excitation scheme, we have obtained rotationally selected and resolved pulsed field ionization-photoelectron (PFI-PE) spectra for vanadium methylidyne cation (VCH{sup +}). This study supports that the ground state electronic configuration for VCH{sup +} is …7σ{sup 2}8σ{sup 2}3π{sup 4}9σ{sup 1} (X{sup ~2}Σ{sup +}), and is different from that of …7σ{sup 2}8σ{sup 2}3π{sup 4}1δ{sup 1} (X{sup ~2}Δ) for the isoelectronic TiO{sup +} and VN{sup +} ions. This observation suggests that the addition of an H atom to vanadium carbide (VC) to form VCH has the effect of stabilizing the 9σ orbital relative to the 1δ orbital. The analysis of the state-to-state IR-UV-PFI-PE spectra has provided precise values for the ionization energy of VCH, IE(VCH) = 54 641.9 ± 0.8 cm{sup −1} (6.7747 ± 0.0001 eV), the rotational constant B{sup +} = 0.462 ± 0.002 cm{sup −1}, and the v{sub 2}{sup +} bending (626 ± 1 cm{sup −1}) and v{sub 3}{sup +} V–CH stretching (852 ± 1 cm{sup −1}) vibrational frequencies for VCH{sup +}(X{sup ~2}Σ{sup +}). The IE(VCH) determined here, along with the known IE(V) and IE(VC), allows a direct measure of the change in dissociation energy for the V–CH as well as the VC–H bond upon removal of the 1δ electron of VCH(X{sup ~3}Δ{sub 1}). The formation of VCH{sup +}(X{sup ~2}Σ{sup +}) from VCH(X{sup ~3}Δ{sub 1}) by photoionization is shown to strengthen the VC–H bond by 0.3559 eV, while the strength of the V–CH bond remains nearly unchanged. This measured change of bond dissociation energies reveals that the highest occupied 1δ orbital is nonbonding for the V–CH bond; but has anti-bonding or destabilizing character for the VC–H bond of VCH(X{sup ~3}Δ{sub 1})

  15. Vibrationally specific photoionization cross sections of acrolein leading to the X̃²A' ionic state.

    PubMed

    López-Domínguez, Jesús A; Lucchese, Robert R; Fulfer, K D; Hardy, David; Poliakoff, E D; Aguilar, A A

    2014-09-01

    The vibrational branching ratios in the photoionization of acrolein for ionization leading to the X̃²A' ion state were studied. Computed logarithmic derivatives of the cross section and the corresponding experimental data derived from measured vibrational branching ratios for several normal modes (ν9, ν10, ν11, and ν12) were found to be in relatively good agreement, particularly for the lower half of the 11-100 eV photon energy range considered. Two shape resonances have been found near photon energies of 15.5 and 23 eV in the photoionization cross section and have been demonstrated to originate from the partial cross section of the A' scattering symmetry. The wave functions computed at the resonance complex energies are delocalized over the whole molecule. By looking at the dependence of the cross section on the different normal mode displacements together with the wave function at the resonant energy, a qualitative explanation is given for the change of the cross sections with respect to changing geometry.

  16. Steady-state benchmarks of DK4D: A time-dependent, axisymmetric drift-kinetic equation solver

    SciTech Connect

    Lyons, B. C.; Jardin, S. C.; Ramos, J. J.

    2015-05-15

    The DK4D code has been written to solve a set of time-dependent, axisymmetric, finite-Larmor-radius drift-kinetic equations (DKEs) for the non-Maxwellian part of the electron and ion distribution functions using the full, linearized Fokker–Planck–Landau collision operator. The plasma is assumed to be in the low- to finite-collisionality regime, as is found in the cores of modern and future magnetic confinement fusion experiments. Each DKE is formulated such that the perturbed distribution function carries no net density, parallel momentum, or kinetic energy. Rather, these quantities are contained within the background Maxwellians and would be evolved by an appropriate set of extended magnetohydrodynamic (MHD) equations. This formulation allows for straight-forward coupling of DK4D to existing extended MHD time evolution codes. DK4D uses a mix of implicit and explicit temporal representations and finite element and spectral spatial representations. These, along with other computational methods used, are discussed extensively. Steady-state benchmarks are then presented comparing the results of DK4D to expected analytic results at low collisionality, qualitatively, and to the Sauter analytic fits for the neoclassical conductivity and bootstrap current, quantitatively. These benchmarks confirm that DK4D is capable of solving for the correct, gyroaveraged distribution function in stationary magnetic equilibria. Furthermore, the results presented demonstrate how the exact drift-kinetic solution varies with collisionality as a function of the magnetic moment and the poloidal angle.

  17. Steady-state benchmarks of DK4D: A time-dependent, axisymmetric drift-kinetic equation solvera)

    NASA Astrophysics Data System (ADS)

    Lyons, B. C.; Jardin, S. C.; Ramos, J. J.

    2015-05-01

    The DK4D code has been written to solve a set of time-dependent, axisymmetric, finite-Larmor-radius drift-kinetic equations (DKEs) for the non-Maxwellian part of the electron and ion distribution functions using the full, linearized Fokker-Planck-Landau collision operator. The plasma is assumed to be in the low- to finite-collisionality regime, as is found in the cores of modern and future magnetic confinement fusion experiments. Each DKE is formulated such that the perturbed distribution function carries no net density, parallel momentum, or kinetic energy. Rather, these quantities are contained within the background Maxwellians and would be evolved by an appropriate set of extended magnetohydrodynamic (MHD) equations. This formulation allows for straight-forward coupling of DK4D to existing extended MHD time evolution codes. DK4D uses a mix of implicit and explicit temporal representations and finite element and spectral spatial representations. These, along with other computational methods used, are discussed extensively. Steady-state benchmarks are then presented comparing the results of DK4D to expected analytic results at low collisionality, qualitatively, and to the Sauter analytic fits for the neoclassical conductivity and bootstrap current, quantitatively. These benchmarks confirm that DK4D is capable of solving for the correct, gyroaveraged distribution function in stationary magnetic equilibria. Furthermore, the results presented demonstrate how the exact drift-kinetic solution varies with collisionality as a function of the magnetic moment and the poloidal angle.

  18. Observation of Interference between Two Distinct Autoionizing States in Dissociative Photoionization of H2

    NASA Astrophysics Data System (ADS)

    Reddish, T. J.; Padmanabhan, A.; MacDonald, M. A.; Zuin, L.; Fernández, J.; Palacios, A.; Martín, F.

    2012-01-01

    Dissociative photoionization (DPI) of randomly oriented H2 molecules has been studied using linearly polarized synchrotron radiation at selected photon energies of 31, 33, and 35 eV. Large amplitude oscillations in the photoelectron asymmetry parameter β, as a function of electron energy, have been observed. The phase of these β oscillations are in excellent agreement with the results of recent close coupling calculations [Fernández and Martín, New J. Phys. 11, 043020 (2009)NJOPFM1367-263010.1088/1367-2630/11/4/043020]. We show that the oscillations are the signature of interferences between the 1Q1Σu+1 and 1Q2Πu1 doubly excited states decaying at different internuclear distances. The oscillations thus provide information about the classical paths followed by the nuclei. The presence of such oscillations is predicted to be a general phenomenon in DPI.

  19. The 2p photoionization of ground-state sodium in the vicinity of Cooper minima

    NASA Astrophysics Data System (ADS)

    Liu, Xiaobin; Shi, Yinglong; Dong, Chenzhong

    2016-07-01

    The photoionization processes of ground-state sodium have been investigated with the multiconfiguration Dirac-Fock method. The results are in good or at least reasonable agreement with available experimental and theoretical data. In the energy region near the threshold, the cross sections show non-monotonic changes because of Cooper minima, which due to the sign changes of dominant dipole matrix elements and are very sensitive to electron correlations. As the energy increases continuously, the radial wave functions of the photoelectrons will move towards the nucleus. The values of the cross sections, and hence the Cooper minima, mainly depend on the relative positions of the one-electron radial wave functions of the initial bound electrons 2{p}1/{2,3/2} and the continuum photoelectrons.

  20. Toward Rotational State-Selective Photoionization of ThF+ Ions

    NASA Astrophysics Data System (ADS)

    Zhou, Yan; Ng, Kia Boon; Gresh, Dan; Cairncross, William; Grau, Matt; Ni, Yiqi; Cornell, Eric; Ye, Jun

    2016-06-01

    ThF+ has been chosen to replace HfF+ for a second-generation measurement of the electric dipole moment of the electron (eEDM). Compared to the currently running HfF+ eEDM experiment, ThF+ has several advantages: (i) the eEDM-sensitive state (3Δ1) is the ground state, which facilitates a long coherence time [1]; (ii) its effective electric field (35 GV/cm) is 50% larger than that of HfF+, which promises a direct increase of the eEDM sensitivity [2]; and (iii) the ionization energy of neutral ThF is lower than its dissociation energy, which introduces greater flexibility in rotational state-selective photoionization via core-nonpenetrating Rydberg states [3]. In this talk, we first present our strategy of preparing and utilizing core-nonpenetrating Rydberg states for rotational state-selective ionization. Then, we report spectroscopic data of laser-induced fluorescence of neutral ThF, which provides critical information for multi-photon ionization spectroscopy. [1] D. N. Gresh, K. C. Cossel, Y. Zhou, J. Ye, E. A. Cornell, Journal of Molecular Spectroscopy, 319 (2016), 1-9 [2] M. Denis, M. S. Nørby, H. J. A. Jensen, A. S. P. Gomes, M. K. Nayak, S. Knecht, T. Fleig, New Journal of Physics, 17 (2015) 043005. [3] Z. J. Jakubek, R. W. Field, Journal of Molecular Spectroscopy 205 (2001) 197-220.

  1. Total photoionization cross-sections of excited electronic states by the algebraic diagrammatic construction-Stieltjes-Lanczos method

    SciTech Connect

    Ruberti, M.; Yun, R.; Averbukh, V.; Gokhberg, K.; Kopelke, S.; Cederbaum, L. S.; Tarantelli, F.

    2014-05-14

    Here, we extend the L{sup 2} ab initio method for molecular photoionization cross-sections introduced in Gokhberg et al. [J. Chem. Phys. 130, 064104 (2009)] and benchmarked in Ruberti et al. [J. Chem. Phys. 139, 144107 (2013)] to the calculation of total photoionization cross-sections of molecules in electronically excited states. The method is based on the ab initio description of molecular electronic states within the many-electron Green's function approach, known as algebraic diagrammatic construction (ADC), and on the application of Stieltjes-Chebyshev moment theory to Lanczos pseudospectra of the ADC electronic Hamiltonian. The intermediate state representation of the dipole operator in the ADC basis is used to compute the transition moments between the excited states of the molecule. We compare the results obtained using different levels of the many-body theory, i.e., ADC(1), ADC(2), and ADC(2)x for the first two excited states of CO, N{sub 2}, and H{sub 2}O both at the ground state and the excited state equilibrium or saddle point geometries. We find that the single excitation ADC(1) method is not adequate even at the qualitative level and that the inclusion of double electronic excitations for description of excited state photoionization is essential. Moreover, we show that the use of the extended ADC(2)x method leads to a substantial systematic difference from the strictly second-order ADC(2). Our calculations demonstrate that a theoretical modelling of photoionization of excited states requires an intrinsically double excitation theory with respect to the ground state and cannot be achieved by the standard single excitation methods with the ground state as a reference.

  2. Probing Invisible, Excited Protein States by Non-Uniformly Sampled Pseudo-4D CEST Spectroscopy.

    PubMed

    Long, Dong; Delaglio, Frank; Sekhar, Ashok; Kay, Lewis E

    2015-09-01

    Chemical exchange saturation transfer (CEST) NMR spectroscopy is a powerful tool for studies of slow timescale protein dynamics. Typical experiments are based on recording a large number of 2D data sets and quantifying peak intensities in each of the resulting planes. A weakness of the method is that peaks must be resolved in 2D spectra, limiting applications to relatively small proteins. Resolution is significantly improved in 3D spectra but recording uniformly sampled data is time-prohibitive. Here we describe non-uniformly sampled HNCO-based pseudo-4D CEST that provides excellent resolution in reasonable measurement times. Data analysis is done through fitting in the time domain, without the need of reconstructing the frequency dimensions, exploiting previously measured accurate peak positions in reference spectra. The methodology is demonstrated on several protein systems, including a nascent form of superoxide dismutase that is implicated in neurodegenerative disease. PMID:26178142

  3. High efficiency photoionization detector

    DOEpatents

    Anderson, D.F.

    1984-01-31

    A high efficiency photoionization detector is described using tetraaminoethylenes in a gaseous state having a low ionization potential and a relative photoionization cross section which closely matches the emission spectrum of xenon gas. Imaging proportional counters are also disclosed using the novel photoionization detector of the invention. The compound of greatest interest is TMAE which comprises tetrakis(dimethylamino)ethylene which has a measured ionization potential of 5.36 [+-] 0.02 eV, and a vapor pressure of 0.35 torr at 20 C. 6 figs.

  4. High efficiency photoionization detector

    DOEpatents

    Anderson, David F.

    1984-01-01

    A high efficiency photoionization detector using tetraaminoethylenes in a gaseous state having a low ionization potential and a relative photoionization cross section which closely matches the emission spectrum of xenon gas. Imaging proportional counters are also disclosed using the novel photoionization detector of the invention. The compound of greatest interest is TMAE which comprises tetrakis(dimethylamino)ethylene which has a measured ionization potential of 5.36.+-.0.02 eV, and a vapor pressure of 0.35 torr at 20.degree. C.

  5. Experimental investigation of photoionization cross section for the 3d 2D excited states of lithium and sodium

    NASA Astrophysics Data System (ADS)

    Nadeem, Ali; Shah, Mehmood; Shahzada, Shaista; Ahmed, Mushtaq; Haq, Sami-ul-

    2013-09-01

    We report experimentally measured photoionization cross sections for the 3 d 2D excited states of lithium and sodium at first ionization threshold. The experiments were performed using two dye lasers simultaneously pumped by the second harmonic of a Nd:YAG laser. The vapor contentment and the detection system was a thermionic diode ion detector operating in a space charge limited mode. Photoionization cross sections of the excited states were deduced from the dependence of ion signal intensity on the ionizing laser energies as 19 ± 3 Mb and 21.5 ± 3.5 Mb for lithium and sodium respectively, which are in good agreement with the previously computed theoretical results.

  6. Spin-orbit driven magnetic insulating state with Jeff=1/2 character in a 4d oxide

    DOE PAGES

    Calder, S.; Li, Ling; Okamoto, Satoshi; Choi, Yongseong; Mukherjee, Rupam; Haskel, Daniel; Mandrus, D.

    2015-11-30

    The unusual magnetic and electronic ground states of 5d iridates has been shown to be driven by intrinsically enhanced spin-orbit coupling (SOC). The influence of appreciable but reduced SOC in creating the manifested magnetic insulating states in 4d oxides is less clear, with one hurdle being the existence of such compounds. Here we present experimental and theoretical results on Sr4RhO6 that reveal SOC dominated behavior. Neutron measurements show the octahedra are both spatially separated and locally ideal, making the electronic ground state susceptible to alterations by SOC. Magnetic ordering is observed with a similar structure to an analogous Jeff=1/2 Mottmore » iridate. We consider the underlying role of SOC in this rhodate with density functional theory and x-ray absorption spectroscopy and find a magnetic insulating ground state with Jeff =1/2 character.The unusual magnetic and electronic ground states of 5d iridates have been shown to be driven by intrinsically enhanced spin-orbit coupling (SOC). The influence of appreciable but reduced SOC in creating the manifested magnetic insulating states in 4d oxides is less clear, with one hurdle being the existence of such compounds. Here, we present experimental and theoretical results on Sr4RhO6 that reveal SOC dominated behavior. Neutron measurements show the octahedra are both spatially separated and locally ideal, making the electronic ground state susceptible to alterations by SOC. Magnetic ordering is observed with a similar structure to an analogous Jeff=1/2 Mott iridate. We consider the underlying role of SOC in this rhodate with density functional theory and x-ray absorption spectroscopy, and find a magnetic insulating ground state with Jeff=12 character.« less

  7. Massless ground state for a compact SU (2) matrix model in 4D

    NASA Astrophysics Data System (ADS)

    Boulton, Lyonell; Garcia del Moral, Maria Pilar; Restuccia, Alvaro

    2015-09-01

    We show the existence and uniqueness of a massless supersymmetric ground state wavefunction of a SU (2) matrix model in a bounded smooth domain with Dirichlet boundary conditions. This is a gauge system and we provide a new framework to analyze the quantum spectral properties of this class of supersymmetric matrix models subject to constraints which can be generalized for arbitrary number of colors.

  8. Above-threshold ionization near the 3p4d 1Fo autoionizing state in magnesium

    NASA Astrophysics Data System (ADS)

    Reber, A.; Baynard, T.; Martín, F.; Bachau, H.; Berry, R. S.

    2005-05-01

    Two-photon above-threshold ionization (ATI) relative cross sections from the 3P1 state of Mg have been measured using two-color ionization in the focus of a magnetic bottle spectrometer and have been calculated using the Green’s-function method in the Feshbach formalism and an L2 -integrable close-coupling approach, with a basis of L2 -integrable B -spline functions. We report these cross sections in the region of 3d4p Fo1 autoionizing state, with photon energies of 3.3-3.6eV . This is one of the few direct comparisons between ab initio theory and experiments in ATI in the vicinity of a Feshbach resonance. A good agreement between theory and experiment is found in the relative total cross sections.

  9. Excited state dynamics in SO2. I. Bound state relaxation studied by time-resolved photoelectron-photoion coincidence spectroscopy.

    PubMed

    Wilkinson, Iain; Boguslavskiy, Andrey E; Mikosch, Jochen; Bertrand, Julien B; Wörner, Hans Jakob; Villeneuve, David M; Spanner, Michael; Patchkovskii, Serguei; Stolow, Albert

    2014-05-28

    The excited state dynamics of isolated sulfur dioxide molecules have been investigated using the time-resolved photoelectron spectroscopy and time-resolved photoelectron-photoion coincidence techniques. Excited state wavepackets were prepared in the spectroscopically complex, electronically mixed (B̃)(1)B1/(Ã)(1)A2, Clements manifold following broadband excitation at a range of photon energies between 4.03 eV and 4.28 eV (308 nm and 290 nm, respectively). The resulting wavepacket dynamics were monitored using a multiphoton ionisation probe. The extensive literature associated with the Clements bands has been summarised and a detailed time domain description of the ultrafast relaxation pathways occurring from the optically bright (B̃)(1)B1 diabatic state is presented. Signatures of the oscillatory motion on the (B̃)(1)B1/(Ã)(1)A2 lower adiabatic surface responsible for the Clements band structure were observed. The recorded spectra also indicate that a component of the excited state wavepacket undergoes intersystem crossing from the Clements manifold to the underlying triplet states on a sub-picosecond time scale. Photoelectron signal growth time constants have been predominantly associated with intersystem crossing to the (c̃)(3)B2 state and were measured to vary between 750 and 150 fs over the implemented pump photon energy range. Additionally, pump beam intensity studies were performed. These experiments highlighted parallel relaxation processes that occurred at the one- and two-pump-photon levels of excitation on similar time scales, obscuring the Clements band dynamics when high pump beam intensities were implemented. Hence, the Clements band dynamics may be difficult to disentangle from higher order processes when ultrashort laser pulses and less-differential probe techniques are implemented.

  10. Communication: State-to-state photodissociation study by the two-color VUV-VUV laser pump-probe time-slice velocity-map-imaging-photoion method

    NASA Astrophysics Data System (ADS)

    Gao, Hong; Song, Yu; Jackson, William M.; Ng, C. Y.

    2013-05-01

    We demonstrate that combining two independently tunable vacuum ultraviolet (VUV) lasers and the time-slice velocity-map-imaging-photoion (VMI-PI) method allows the rovibronically state-selected photodissociation study of CO in the VUV region along with the state-selective detection of product C(3P0,1,2) using the VUV-UV (1+1') resonance-enhanced photoionization and the VUV Rydberg autoionization methods. Both tunable VUV lasers are generated based on the two-photon resonance-enhanced four-wave mixing scheme using a pulsed rare gas jet as the nonlinear medium. The observed fine-structure distributions of product C(3PJ), J = 0, 1, and 2, are found to depend on the CO rovibronic state populated by VUV photoexcitation. The branching ratios for C(3P0) + O(3PJ): C(3P0) + O(1D2), C(3P1) + O(3PJ): C(3P1) + O(1D2), and C(3P2) + O(3PJ): C(3P2) + O(1D2), which were determined based on the time-slice VMI-PI measurements of C+ ions formed by J-state selective photoionization sampling of C(3P0,1,2), also reveal strong dependences on the spin-orbit state of C(3P0,1,2). By combining the measured branching ratios and fine-structure distributions of C(3P0,1,2), we have determined the correlated distributions of C(3P0,1,2) accompanying the formation of O(1D2) and O(3PJ) produced in the VUV photodissociation of CO. The success of this demonstration experiment shows that the VUV photodissociation pump-VUV photoionization probe method is promising for state-to-state photodissociation studies of many small molecules, which are relevant to planetary atmospheres as well as fundamental understanding of photodissociation dynamics.

  11. Photoionization of FE3+ Ions

    SciTech Connect

    Ovchinnikov, O.; Schlachter, F.

    2003-01-01

    Photoionization of Fe3+ ions was studied for the first time using synchrotron radiation from the Advanced Light Source (ALS) and the merged-beams technique. Fe3+ ions were successfully produced using ferrocene in an electron cyclotron resonance ion source (ECR). The measured yield of Fe4+ photoions as a function of photon energy revealed the presence of resonances that correspond to excitation of autoionizing states. These resonances are superimposed upon the photoion yield produced by direct photoionization, which is a smooth, slowly decreasing function of energy. The spectra for the photoionization of Fe3+ will be analyzed and compared with theory. The data collected will also serve to test models for the propagation of light through ionized matter.

  12. Manifestation of Strongly Delocalized Atomic States in the 5{ital s} Photoionization of Xenon

    SciTech Connect

    Schmoranzer, H.; Lauer, S.; Vollweiler, F.; Reichardt, G.; Schartner, K.; Mentzel, G.; Wilhelmi, O.; Sukhorukov, V.L.; Lagutin, B.M.; Petrov, I.D.

    1997-12-01

    The photoionization (PI) of the Xe atom was investigated in the vicinity of the 5s -shell threshold by photon-induced fluorescence spectroscopy. The highest resolution so far attained of 2meV enabled us to observe a new series of resonance structures in the 5s -PI cross section closely above threshold. Calculations of the partial 5s - and 5p -PI cross sections were performed taking into account many-electron correlations. These structures were related with strongly delocalized f -resonances which affect the 5s -PI cross section due to their mixing with p -resonances. {copyright} {ital 1997} {ital The American Physical Society}

  13. Methods for studying the coherent 4D structural dynamics of free molecules and condensed state of matter

    NASA Astrophysics Data System (ADS)

    Ishchenko, A. A.; Bagratashvili, V. N.; Avilov, A. S.

    2011-09-01

    Studies in the coupled 4D spatial and temporal continuum are necessary for understanding the dynamic features of molecular systems with a complex profile of the potential energy surface. The introduction of time sweep into diffraction methods and the development of principles for studying coherent processes have revealed new approaches to the analysis of the dynamics of wave packets, the intermediate products and the transition state of the reaction center, and short-lived compounds in gaseous and condensed media. The use of picosecond and femtosecond electron probe pulses, synchronized with excitation laser pulses, determined the development of ultrafast electron crystallography, time-resolved X-ray diffraction, and dynamic transmission electron microscopy (DTEM). One of the most promising applications of the developed diffraction methods is the characterization and visualization of the processes occurring upon the photoexcitation of free molecules and biological objects and the analysis of surface and thin films. The whole set of spectral and diffraction methods based on different physical principles, which are complementary and make it possible to perform the photoexcitation of nuclei and electrons and carry out diagnostics of their dynamics at ultrashort time sequences, reveal new possibilities for studies with the necessary integration of the "structure-dynamics-function" triad in chemistry, biology, and materials science.

  14. Joint CO2 state and flux estimation with the 4D-Var system EURAD-IM

    NASA Astrophysics Data System (ADS)

    Klimpt, Johannes; Elbern, Hendrik

    2016-04-01

    Atmospheric CO2 inversion studies seek to improve CO2 surface-atmosphere fluxes with the usage of adjoint transport models and CO2 concentration measurements. Terrestrial CO2 fluxes -anthropogenic emissions, photosynthesis, and respiration- bear large spatial and temporal variability and are highly uncertain. Additionally to the high uncertainty of the three CO2 fluxes itself, regional inversion studies suffer from uncertainty of the boundary layer height and atmospheric transport especially during night, leading to uncertainty of atmospheric CO2 mixing ratios during sunrise. This study assesses the potential of the 4-dimensional variational (4D-Var) method to estimate CO2 fluxes and atmospheric CO2 concentrations jointly at each grid cell on a regional scale. Identical twin experiments are executed with the nested EURopean Air pollution Dispersion-Inverse Model (EURAD-IM) with 5 km resolution in Central Europe with synthetic half hourly measurements from eleven concentration towers. The assimilation window is chosen to start from sunrise for 12 hours. We find that joint estimation of CO2 fluxes and initial states requires a more careful balance of the background error covariance matrices but enables a more detailed analysis of atmospheric CO2 and the surface-atmosphere fluxes.

  15. Vibrationally specific photoionization cross sections of acrolein leading to the tilde{X} {}^2 A^' } ionic state

    NASA Astrophysics Data System (ADS)

    López-Domínguez, Jesús A.; Lucchese, Robert R.; Fulfer, K. D.; Hardy, David; Poliakoff, E. D.; Aguilar, A. A.

    2014-09-01

    The vibrational branching ratios in the photoionization of acrolein for ionization leading to the tilde{X} {}^2 A^' } ion state were studied. Computed logarithmic derivatives of the cross section and the corresponding experimental data derived from measured vibrational branching ratios for several normal modes (ν9, ν10, ν11, and ν12) were found to be in relatively good agreement, particularly for the lower half of the 11-100 eV photon energy range considered. Two shape resonances have been found near photon energies of 15.5 and 23 eV in the photoionization cross section and have been demonstrated to originate from the partial cross section of the A' scattering symmetry. The wave functions computed at the resonance complex energies are delocalized over the whole molecule. By looking at the dependence of the cross section on the different normal mode displacements together with the wave function at the resonant energy, a qualitative explanation is given for the change of the cross sections with respect to changing geometry.

  16. Vibrationally specific photoionization cross sections of acrolein leading to the Χ{sup ~}A{sup '} ionic state

    SciTech Connect

    López-Domínguez, Jesús A.; Lucchese, Robert R.; Fulfer, K. D.; Hardy, David; Poliakoff, E. D.; Aguilar, A. A.

    2014-09-07

    The vibrational branching ratios in the photoionization of acrolein for ionization leading to the Χ{sup ~}A{sup '} ion state were studied. Computed logarithmic derivatives of the cross section and the corresponding experimental data derived from measured vibrational branching ratios for several normal modes (ν{sub 9}, ν{sub 10}, ν{sub 11}, and ν{sub 12}) were found to be in relatively good agreement, particularly for the lower half of the 11–100 eV photon energy range considered. Two shape resonances have been found near photon energies of 15.5 and 23 eV in the photoionization cross section and have been demonstrated to originate from the partial cross section of the A{sup ′} scattering symmetry. The wave functions computed at the resonance complex energies are delocalized over the whole molecule. By looking at the dependence of the cross section on the different normal mode displacements together with the wave function at the resonant energy, a qualitative explanation is given for the change of the cross sections with respect to changing geometry.

  17. Photoionization microscopy of the lithium atom: Wave-function imaging of quasibound and continuum Stark states

    NASA Astrophysics Data System (ADS)

    Cohen, S.; Harb, M. M.; Ollagnier, A.; Robicheaux, F.; Vrakking, M. J. J.; Barillot, T.; Lépine, F.; Bordas, C.

    2016-07-01

    Photoionization of an atom in the presence of a uniform static electric field provides the unique opportunity to expand and visualize the atomic wave function at a macroscopic scale. In a number of seminal publications dating back to the 1980s, Fabrikant, Demkov, Kondratovich, and Ostrovsky showed that this goal could be achieved by projecting slow (meV) photoionized electrons onto a position-sensitive detector and underlined the distinction between continuum and resonant contributions. The uncovering of resonant signatures was achieved fairly recently in experiments on the nonhydrogenic lithium atoms [Cohen et al., Phys. Rev. Lett. 110, 183001 (2013)], 10.1103/PhysRevLett.110.183001. The purpose of the present article is the general description of these findings, with emphasis on the various manifestations of resonant character. From this point of view, lithium has been chosen as an illustrative example between the two limiting cases of hydrogen, where resonance effects are more easily identified, and heavy atoms like xenon, where resonant effects were not observed.

  18. Molecular photoionization studies

    SciTech Connect

    Dehmer, P.M.

    1983-01-01

    This program is concerned with the study of the electronic structure of small molecules and clusters of molecules. Of particular interest is the interaction of discrete electronic states with one another and with the various ionization and dissociation continua. Since the Second Annual Meeting of the DOE-OHER Program on The Physics and Chemistry of Energy-Related Atmospheric Pollutants in April 1981, significant progress has been made in the following areas: (1) the study of the electronic structure of dimers and small clusters of rare gas atoms using photoionization techniques; (2) similar studies on clusters of CO/sub 2/ molecules; (3) the study of electronic structure of rare gas dimers and trimers using photoelectron and photoelectron-photoion coincidence techniques; (4) the investigation of the relationship between Rydberg states in atoms, van der Waals molecules, and chemically-bonded molecules; (5) the extension of the study of photoabsorption, photoionization, and predissociation processes in H/sub 2/ to the unsymmetric isotope HD; (6) the study of photoelectron spectra of H/sub 2/ and C/sub 2/H/sub 2/; (7) a review of some of the aspects of dissociation processes in small molecules; and (8) the creation of a new program to study the spectra and dynamics of the photoionization processes in small molecules using the technique of multiphoton ionization followed by mass and electron energy analysis of the product ions and electrons. Some of the highlights of this work are reviewed.

  19. Photoelectron photoion molecular beam spectroscopy

    SciTech Connect

    Trevor, D.J.

    1980-12-01

    The use of supersonic molecular beams in photoionization mass spectroscopy and photoelectron spectroscopy to assist in the understanding of photoexcitation in the vacuum ultraviolet is described. Rotational relaxation and condensation due to supersonic expansion were shown to offer new possibilities for molecular photoionization studies. Molecular beam photoionization mass spectroscopy has been extended above 21 eV photon energy by the use of Stanford Synchrotron Radiation Laboratory (SSRL) facilities. Design considerations are discussed that have advanced the state-of-the-art in high resolution vuv photoelectron spectroscopy. To extend gas-phase studies to 160 eV photon energy, a windowless vuv-xuv beam line design is proposed.

  20. Gadolinium photoionization process

    DOEpatents

    Paisner, J.A.; Comaskey, B.J.; Haynam, C.A.; Eggert, J.H.

    1993-04-13

    A method is provided for selective photoionization of the odd-numbered atomic mass gadolinium isotopes 155 and 157. The selective photoionization is accomplished by circular or linear parallel polarized laser beam energy effecting a three-step photoionization pathway.

  1. Gadolinium photoionization process

    DOEpatents

    Paisner, Jeffrey A.; Comaskey, Brian J.; Haynam, Christopher A.; Eggert, Jon H.

    1993-01-01

    A method is provided for selective photoionization of the odd-numbered atomic mass gadolinium isotopes 155 and 157. The selective photoionization is accomplished by circular or linear parallel polarized laser beam energy effecting a three-step photoionization pathway.

  2. Communication: State-to-state photodissociation study by the two-color VUV-VUV laser pump-probe time-slice velocity-map-imaging-photoion method.

    PubMed

    Gao, Hong; Song, Yu; Jackson, William M; Ng, C Y

    2013-05-21

    We demonstrate that combining two independently tunable vacuum ultraviolet (VUV) lasers and the time-slice velocity-map-imaging-photoion (VMI-PI) method allows the rovibronically state-selected photodissociation study of CO in the VUV region along with the state-selective detection of product C((3)P(0,1,2)) using the VUV-UV (1+1') resonance-enhanced photoionization and the VUV Rydberg autoionization methods. Both tunable VUV lasers are generated based on the two-photon resonance-enhanced four-wave mixing scheme using a pulsed rare gas jet as the nonlinear medium. The observed fine-structure distributions of product C((3)P(J)), J = 0, 1, and 2, are found to depend on the CO rovibronic state populated by VUV photoexcitation. The branching ratios for C((3)P0) + O((3)P(J)): C((3)P0) + O((1)D2), C((3)P1) + O((3)P(J)): C((3)P1) + O((1)D2), and C((3)P2) + O((3)PJ): C((3)P2) + O((1)D2), which were determined based on the time-slice VMI-PI measurements of C(+) ions formed by J-state selective photoionization sampling of C((3)P(0,1,2)), also reveal strong dependences on the spin-orbit state of C((3)P(0,1,2)). By combining the measured branching ratios and fine-structure distributions of C((3)P(0,1,2)), we have determined the correlated distributions of C((3)P(0,1,2)) accompanying the formation of O((1)D2) and O((3)P(J)) produced in the VUV photodissociation of CO. The success of this demonstration experiment shows that the VUV photodissociation pump-VUV photoionization probe method is promising for state-to-state photodissociation studies of many small molecules, which are relevant to planetary atmospheres as well as fundamental understanding of photodissociation dynamics.

  3. Spin-resolved photoionization studies

    NASA Astrophysics Data System (ADS)

    Snell, G.; Berrah, N.; Langer, B.; Bozek, J. D.

    2000-06-01

    We performed spin-polarization measurements of the Xe N_45O_23O_23, Kr M_45N_23N_23 and Ar L_23M_23M_23 Auger electron with circularly polarized light from the ALS fom threshold up to 540 eV photon energy. The spin-resolved electron spectra were recorded by a new spectrometer system that combines our time-of flight spectrometers with a retarding field Mott polarimeter of the Burnett et al. design.footnote C. Burnett, T. J. Monroe, and F. B. Dunning, Rev. Sci. Instrum. 65,1893 (1994). From our measurements, the orientation parameter A_10 of the Xe 4d-1, Kr 3d-1 and Ar 2p-1 hole states were obtained over a broad photon energy range covering the shape resonance (≈ 100 eV) and the Cooper minimum (≈ 175 eV) of the photoionization cross section. Our measurements are the first direct experimental proof that in the Cooper minimum of a d-subshell photoionziation the outgoing electrons have a purely p character. This work was funded by DOE/BES/Chem.Sci.

  4. Effects of exchange-correlation potentials in density functional descriptions of ground-state and photoionization of fullerenes

    NASA Astrophysics Data System (ADS)

    Choi, Jinwoo; Chang, Eonho; Anstine, Dylan M.; Chakraborty, Himadri

    2016-05-01

    We study the ground state properties of C60 and C240 molecules in a spherical frame of local density approximation (LDA). Within this mean-field theory, two different approximations to the exchange-correlation (xc) functional are used: (i) The Gunnerson-Lundqvist parametrization augmented by a treatment to correct for the electron self-interaction and (ii) the van Leeuwen and Baerends (LB94) model potential that inclusively restores electron's asymptotic properties. Results show differences in the ground-state potential, level energies and electron densities between the two xc choices. We then use the ground structure to find the excited and ionized states of the systems and calculate dipole single-photoionization cross sections in a time-dependent LDA method that incorporates linear-response dynamical correlations. Comparative effects of the choices of xc on collective plasmon and single-excitation Auger resonances as well as on geometry driven cavity oscillations are found significant. The work is supported by the NSF, USA.

  5. State-selected and state-to-state photoionization study of trichloroethene using the two-color infrared-vacuum ultraviolet scheme

    NASA Astrophysics Data System (ADS)

    Woo, H. K.; Wang, P.; Lau, K.-C.; Xing, X.; Chang, C.; Ng, C. Y.

    2003-11-01

    By employing the two-color infrared (IR)-vacuum ultraviolet (VUV) laser photoionization (PI) schemes, we have determined the C-H stretching frequencies ν12=3097.7 cm-1 for trichloroethene (CHCl=CCl2) and ν12+=3066 cm-1 for CHCl=CCl2+. On the basis of the IR-VUV-pulsed field ionization-photoelectron (PFI-PE) measurement, the ratio of the state-to-state PI cross section for CHCl=CCl2+(ν12+=1)←CHCl=CCl2(ν12=1) to that for the formation of the ground state ion from the ground state neutral is determined to be 0.24. The VUV-PI efficiency (PIE) spectrum for CHCl=CCl2 and IR-VUV-PIE spectrum for CHCl=CCl2(ν12=1) show that the state-to-state PI cross section for the formation of CHCl=CCl2+ in the ground state from CHCl=CCl2(ν12=1) is ≈0.006 that from CHCl=CCl2 in its ground state. As expected, the IR-VUV-PIE onset for CHCl=CCl2(ν12=1) exhibits less hot-band tailing than the VUV-PIE onset for supersonically cooled CHCl=CCl2. After taking into account the ν12 frequency, the ionization energy values for CHCl=CCl2 determined based on the IR-VUV-PIE and VUV-PFI-PE measurements are found to be in excellent agreement.

  6. Spin-Orbit Activated Interchannel Coupling Effect in Dipole and Quadrupole Photoionization

    NASA Astrophysics Data System (ADS)

    Kumar, S. Sunil; Deschmukh, P. C.; Banerjee, T.; Manson, S. T.

    2008-05-01

    Spin-orbit activated interchannel coupling has been found to affect photoelectron parameters in both the dipole and quadrupole manifolds [1-3]. This effect has been reported in the dipole photoionization parameters of 3d subshells of Xe [1], Ba [1, 3] and Cs [1, 3] and quadrupole spin-polarization parameters of Xe 3d [2]. In the present work, dipole and quadrupole photoionization from 4d and 4p subshells of Xe and 5d and 5p subshells of Rn have been investigated. The effect is significant in dipole photoionization of Xe 4d and Rn 5d, and in quadrupole photoionization of Xe 4p and of Rn 5p states. [1] M. Ya. Amusia, L. V. Chernysheva, S. T. Manson, A. M. Msezane, and V. Radojevic, Phys. Rev. Lett. 88 093002 (2002). [2] M. Ya. Amusia, N. A. Cherepkov, L. V. Chernysheva, Z. Felfli and A. Z. Msezane, J. Phys. B 38 1133 (2005). [3] T. Richter, E. Heinecke, P. Zimmermann, K. Godehusen, M. Yalcinkaya, D. Cubaynes, and M. Meyer, Phys. Rev. Lett. 98 143002 (2007).

  7. Analysis of 1s(2s2p {sup 3}P)nl Rydberg states in the K-shell photoionization of the Be atom

    SciTech Connect

    Yoshida, Fumiko; Matsuoka, Leo; Takashima, Ryuta; Hasegawa, Shuichi; Nagata, Tetsuo; Azuma, Yoshiro; Obara, Satoshi; Koike, Fumihiro

    2006-06-15

    We have observed inner-shell photoionization of Be using synchrotron radiation in the energy region of the 1s(2s2p {sup 3}P)nl Rydberg states. We used a time-of-flight method to distinguish singly and doubly charged photoions and obtained the Be{sup +} [ns; n=5-12 ({sup 1}P)3s] and Be{sup 2+} [ns; n=5-8, nd=5,6 ({sup 1}P)3s] ion spectra with high resolution corresponding to an instrumental bandpass of 13 meV. Detailed analysis enabled the autoionization parameters, resonance energy position E{sub 0}, resonance width {gamma}, and Fano parameter q, to be obtained. From the resonance positions of the {sup 3}Pnl series members, the series limit was determined to be 127.97 eV, which is in good agreement with previous experiments.

  8. Fine- and hyperfine-structure effects in molecular photoionization. I. General theory and direct photoionization.

    PubMed

    Germann, Matthias; Willitsch, Stefan

    2016-07-28

    We develop a model for predicting fine- and hyperfine intensities in the direct photoionization of molecules based on the separability of electron and nuclear spin states from vibrational-electronic states. Using spherical tensor algebra, we derive highly symmetrized forms of the squared photoionization dipole matrix elements from which we derive the salient selection and propensity rules for fine- and hyperfine resolved photoionizing transitions. Our theoretical results are validated by the analysis of the fine-structure resolved photoelectron spectrum of O2 reported by Palm and Merkt [Phys. Rev. Lett. 81, 1385 (1998)] and are used for predicting hyperfine populations of molecular ions produced by photoionization. PMID:27475368

  9. Fine- and hyperfine-structure effects in molecular photoionization. I. General theory and direct photoionization.

    PubMed

    Germann, Matthias; Willitsch, Stefan

    2016-07-28

    We develop a model for predicting fine- and hyperfine intensities in the direct photoionization of molecules based on the separability of electron and nuclear spin states from vibrational-electronic states. Using spherical tensor algebra, we derive highly symmetrized forms of the squared photoionization dipole matrix elements from which we derive the salient selection and propensity rules for fine- and hyperfine resolved photoionizing transitions. Our theoretical results are validated by the analysis of the fine-structure resolved photoelectron spectrum of O2 reported by Palm and Merkt [Phys. Rev. Lett. 81, 1385 (1998)] and are used for predicting hyperfine populations of molecular ions produced by photoionization.

  10. Fine- and hyperfine-structure effects in molecular photoionization. I. General theory and direct photoionization

    NASA Astrophysics Data System (ADS)

    Germann, Matthias; Willitsch, Stefan

    2016-07-01

    We develop a model for predicting fine- and hyperfine intensities in the direct photoionization of molecules based on the separability of electron and nuclear spin states from vibrational-electronic states. Using spherical tensor algebra, we derive highly symmetrized forms of the squared photoionization dipole matrix elements from which we derive the salient selection and propensity rules for fine- and hyperfine resolved photoionizing transitions. Our theoretical results are validated by the analysis of the fine-structure resolved photoelectron spectrum of O2 reported by Palm and Merkt [Phys. Rev. Lett. 81, 1385 (1998)] and are used for predicting hyperfine populations of molecular ions produced by photoionization.

  11. Rotationally resolved state-to-state photoionization and photoelectron study of titanium carbide and its cation (TiC/TiC⁺).

    PubMed

    Luo, Zhihong; Huang, Huang; Chang, Yih-Chung; Zhang, Zheng; Yin, Qing-Zhu; Ng, C Y

    2014-10-14

    Titanium carbide and its cation (TiC/TiC(+)) have been investigated by the two-color visible (VIS)-ultraviolet (UV) resonance-enhanced photoionization and pulsed field ionization-photoelectron (PFI-PE) methods. Two visible excitation bands for neutral TiC are observed at 16,446 and 16,930 cm(-1). Based on rotational analyses, these bands are assigned as the respective TiC((3)Π1) ← TiC(X(3)Σ(+)) and TiC((3)Σ(+)) ← TiC(X(3)Σ(+)) transition bands. This assignment supports that the electronic configuration and term symmetry for the neutral TiC ground state are …7σ(2)8σ(1)9σ(1)3π(4) (X(3)Σ(+)). The rotational constant and the corresponding bond distance of TiC(X(3)Σ(+); v″ = 0) are determined to be B0″ = 0.6112(10) cm(-1) and r0″ = 1.695(2) Å, respectively. The rotational analyses of the VIS-UV-PFI-PE spectra for the TiC(+)(X; v(+) = 0 and 1) vibrational bands show that the electronic configuration and term symmetry for the ionic TiC(+) ground state are …7σ(2)8σ(1)3π(4) (X(2)Σ(+)) with the v(+) = 0 → 1 vibrational spacing of 870.0(8) cm(-1) and the rotational constants of B(e)(+) = 0.6322(28) cm(-1), and α(e)(+) = 0.0085(28) cm(-1). The latter rotational constants yield the equilibrium bond distance of r(e)(+) = 1.667(4) Å for TiC(+)(X(2)Σ(+)). The cleanly rotationally resolved VIS-UV-PFI-PE spectra have also provided a highly precise value of 53 200.2(8) cm(-1) [6.5960(1) eV] for the adiabatic ionization energy (IE) of TiC. This IE(TiC) value along with the known IE(Ti) has made possible the determination of the difference between the 0 K bond dissociation energy (D0) of TiC(+)(X(2)Σ(+)) and that of TiC(X(3)Σ(+)) to be D0(Ti(+)-C) - D0(Ti-C) = 0.2322(2) eV. Similar to previous experimental observations, the present state-to-state PFI-PE study of the photoionization transitions, TiC(+)(X(2)Σ(+); v(+) = 0 and 1, N(+)) ← TiC((3)Π1; v', J'), reveals a strong decreasing trend for the photoionization cross section as |ΔN(+)| = |N

  12. The ionic states of iodobenzene studied by photoionization and ab initio configuration interaction and DFT computations

    SciTech Connect

    Palmer, Michael H. E-mail: tr01@staffmail.ed.ac.uk E-mail: nykj@phys.au.dk E-mail: desimone@iom.cnr.it Ridley, Trevor; Hoffmann, Søren Vrønning; Jones, Nykola C.; Coreno, Marcello; Grazioli, Cesare; Biczysko, Malgorzata; Baiardi, Alberto

    2015-04-07

    New valence electron photoelectron spectra of iodobenzene obtained using synchrotron radiation have been recorded. Ionization energies (IEs) determined using multi-configuration SCF calculation (MCSCF) procedures confirmed the adiabatic IE order as: X{sup 2}B{sub 1}state. The fifth ionization process shown to be D{sup 2}A{sub 1} exhibits dissociation to C{sub 6}H{sub 5}{sup +} + I both in the experimental and theoretical studies. The calculated Franck-Condon vibrational spectral envelopes, including hot band contributions, for the first four ionic states reproduce the observed peak positions and intensities with reasonable accuracy. In order to simulate the observed spectra, different bandwidths are required for different states. The increase in the required bandwidths for the A{sup 2}A{sub 2} and B{sup 2}B{sub 2} states is attributed to internal conversion to lower-lying states. The presence of relatively high intensity sequence bands leads to asymmetry of each of the X{sup 2}B{sub 1} state bands.

  13. The ionic states of iodobenzene studied by photoionization and ab initio configuration interaction and DFT computations

    NASA Astrophysics Data System (ADS)

    Palmer, Michael H.; Ridley, Trevor; Hoffmann, Søren Vrønning; Jones, Nykola C.; Coreno, Marcello; de Simone, Monica; Grazioli, Cesare; Biczysko, Malgorzata; Baiardi, Alberto

    2015-04-01

    New valence electron photoelectron spectra of iodobenzene obtained using synchrotron radiation have been recorded. Ionization energies (IEs) determined using multi-configuration SCF calculation (MCSCF) procedures confirmed the adiabatic IE order as: X2B1state. The fifth ionization process shown to be D2A1 exhibits dissociation to C6H5+ + I both in the experimental and theoretical studies. The calculated Franck-Condon vibrational spectral envelopes, including hot band contributions, for the first four ionic states reproduce the observed peak positions and intensities with reasonable accuracy. In order to simulate the observed spectra, different bandwidths are required for different states. The increase in the required bandwidths for the A2A2 and B2B2 states is attributed to internal conversion to lower-lying states. The presence of relatively high intensity sequence bands leads to asymmetry of each of the X2B1 state bands.

  14. Nondipole Effects in Xe 4d Photoemission

    SciTech Connect

    Hemmers, O; Guillemin, R; Wolska, A; Lindle, D W; Rolles, D; Cheng, K T; Johnson, W R; Zhou, H L; Manson, S T

    2004-07-14

    We measured the nondipole parameters for the spin-orbit doublets Xe 4d{sub 5/2} and Xe 4d{sub 3/2} over a photon-energy range from 100 eV to 250 eV at beamline 8.0.1.3 of the Advanced Light Source at the Lawrence Berkeley National Laboratory. Significant nondipole effects are found at relatively low energies as a result of Cooper minima in dipole channels and interchannel coupling in quadrupole channels. Most importantly, sharp disagreement between experiment and theory, when otherwise excellent agreement was expected, has provided the first evidence of satellite two-electron quadrupole photoionization transitions, along with their crucial importance for a quantitatively accurate theory.

  15. Spin-orbit driven magnetic insulating state with Jeff=1/2 character in a 4d oxide

    SciTech Connect

    Calder, S.; Li, Ling; Okamoto, Satoshi; Choi, Yongseong; Mukherjee, Rupam; Haskel, Daniel; Mandrus, D.

    2015-11-30

    The unusual magnetic and electronic ground states of 5d iridates has been shown to be driven by intrinsically enhanced spin-orbit coupling (SOC). The influence of appreciable but reduced SOC in creating the manifested magnetic insulating states in 4d oxides is less clear, with one hurdle being the existence of such compounds. Here we present experimental and theoretical results on Sr4RhO6 that reveal SOC dominated behavior. Neutron measurements show the octahedra are both spatially separated and locally ideal, making the electronic ground state susceptible to alterations by SOC. Magnetic ordering is observed with a similar structure to an analogous Jeff=1/2 Mott iridate. We consider the underlying role of SOC in this rhodate with density functional theory and x-ray absorption spectroscopy and find a magnetic insulating ground state with Jeff =1/2 character.The unusual magnetic and electronic ground states of 5d iridates have been shown to be driven by intrinsically enhanced spin-orbit coupling (SOC). The influence of appreciable but reduced SOC in creating the manifested magnetic insulating states in 4d oxides is less clear, with one hurdle being the existence of such compounds. Here, we present experimental and theoretical results on Sr4RhO6 that reveal SOC dominated behavior. Neutron measurements show the octahedra are both spatially separated and locally ideal, making the electronic ground state susceptible to alterations by SOC. Magnetic ordering is observed with a similar structure to an analogous Jeff=1/2 Mott iridate. We consider the underlying role of SOC in this rhodate with density functional theory and x-ray absorption spectroscopy, and find a magnetic insulating ground state with Jeff=12 character.

  16. Double photoionization of SO 2 and fragmentation spectroscopy of SO 2++ studied by a photoion-photoion coincidence method

    NASA Astrophysics Data System (ADS)

    Dujardin, Gérald; Leach, Sydney; Dutuit, Odile; Guyon, Paul-Marie; Richard-Viard, Martine

    1984-08-01

    Doubly charged sulphur dioxide cations (SO 2++) are produced by photoionization with synchrotron radiation from ACO in the excitation-energy range 34-54 eV. A new photoion-photoion coincidence (PIPICO) experiment is described in which coincidences between photoion fragments originating from the dissociation of the doubly charged parent cation are counted. This PIPICO method enables us to study the fragmentation of individual electronically excited states of SO 2++ and to determine the corresponding absolute double-photoionization partial cross sections as a function of the excitation energy. A tentative assignment of the three observed α, β and γ SO 2++ states is given. The dissociation processes of the α and β states into the products SO + + O + are found to be non-statistical in nature; the γ state dissociates completely into three atomic fragments S + + O + + O. Three main observed features of the double-photoionization cross-section curves are discussed in the text: appearance potentials, linear threshold laws, and constant double-photoionization cross sections relative to the total ionization cross section at high energies.

  17. Effects of the admixed state on the photoionization in the 6p subshell of Pb

    SciTech Connect

    Krause, M.O.; Gerard, P.; Fahlman, A.

    1986-11-01

    Photoelectrons that leave the residual Pb ion in the 6s/sup 2/6p( /sup 2/P/sub 1/2/) and 6s/sup 2/6p( /sup 2/P/sub 3/2/) states were observed from the ionization threshold (7.42 eV) to 12 eV. Partial and total cross sections were obtained, the latter also from ion measurements. The 6p/sub 1/2/ cross section was found to be unexpectedly small near threshold (/sup 2/P/sub 1/2/), but strongly enhanced near the /sup 2/P/sub 3/2/ threshold associated with the admixed 6p/sub 3/2/ configuration. The 6p/sub 3/2/ cross section is unusually large at threshold.

  18. Novel thiazolo[5,4-d]thiazole-based organic dyes for quasi-solid-state dye-sensitized solar cells.

    PubMed

    Zhang, Weiyi; Feng, Quanyou; Wang, Zhong-Sheng; Zhou, Gang

    2013-05-01

    A series of novel metal-free organic dyes containing the thiazolo[5,4-d]thiazole moiety were designed and synthesized for quasi-solid-state dye-sensitized solar cells (DSSCs). Different alkoxy chains were introduced into the electron donor part of the dye molecules for comparison. The optical, electrochemical, and photovoltaic properties for all sensitizers were systematically investigated. It was found that the sensitizers with the different alkoxy groups have similar photophysical and electrochemical properties, such as absorbance and energy levels, owing to their close chemical structures. However, the quasi-solid-state DSSCs based on the resulting sensitizers exhibit different performance parameters. The quasi-solid-state DSSC based on sensitizer FNE74 with two octyloxy chains possessed the highest solar energy conversion efficiency of 5.10 % under standard AM 1.5G sunlight illumination without the use of coadsorbant agents.

  19. PHOTOIONIZATION IN THE SOLAR WIND

    SciTech Connect

    Landi, E.; Lepri, S. T.

    2015-10-20

    In this work we investigate the effects of photoionization on the charge state composition of the solar wind. Using measured solar EUV and X-ray irradiance, the Michigan Ionization Code and a model for the fast and slow solar wind, we calculate the evolution of the charge state distribution of He, C, N, O, Ne, Mg, Si, S, and Fe with and without including photoionization for both types of wind. We find that the solar radiation has significant effects on the charge state distribution of C, N, and O, causing the ionization levels of these elements to be higher than without photoionization; differences are largest for oxygen. The ions commonly observed for elements heavier than O are much less affected, except in ICMEs where Fe ions more ionized than 16+ can also be affected by the solar radiation. We also show that the commonly used O{sup 7+}/O{sup 6+} density ratio is the most sensitive to photoionization; this sensitivity also causes the value of this ratio to depend on the phase of the solar cycle. We show that the O{sup 7+}/O{sup 6+} ratio needs to be used with caution for solar wind classification and coronal temperature estimates, and recommend the C{sup 6+}/C{sup 4+} ratio for these purposes.

  20. 4-D Photoacoustic Tomography

    NASA Astrophysics Data System (ADS)

    Xiang, Liangzhong; Wang, Bo; Ji, Lijun; Jiang, Huabei

    2013-01-01

    Photoacoustic tomography (PAT) offers three-dimensional (3D) structural and functional imaging of living biological tissue with label-free, optical absorption contrast. These attributes lend PAT imaging to a wide variety of applications in clinical medicine and preclinical research. Despite advances in live animal imaging with PAT, there is still a need for 3D imaging at centimeter depths in real-time. We report the development of four dimensional (4D) PAT, which integrates time resolutions with 3D spatial resolution, obtained using spherical arrays of ultrasonic detectors. The 4D PAT technique generates motion pictures of imaged tissue, enabling real time tracking of dynamic physiological and pathological processes at hundred micrometer-millisecond resolutions. The 4D PAT technique is used here to image needle-based drug delivery and pharmacokinetics. We also use this technique to monitor 1) fast hemodynamic changes during inter-ictal epileptic seizures and 2) temperature variations during tumor thermal therapy.

  1. 4D Electron Tomography

    NASA Astrophysics Data System (ADS)

    Kwon, Oh-Hoon; Zewail, Ahmed H.

    2010-06-01

    Electron tomography provides three-dimensional (3D) imaging of noncrystalline and crystalline equilibrium structures, as well as elemental volume composition, of materials and biological specimens, including those of viruses and cells. We report the development of 4D electron tomography by integrating the fourth dimension (time resolution) with the 3D spatial resolution obtained from a complete tilt series of 2D projections of an object. The different time frames of tomograms constitute a movie of the object in motion, thus enabling studies of nonequilibrium structures and transient processes. The method was demonstrated using carbon nanotubes of a bracelet-like ring structure for which 4D tomograms display different modes of motion, such as breathing and wiggling, with resonance frequencies up to 30 megahertz. Applications can now make use of the full space-time range with the nanometer-femtosecond resolution of ultrafast electron tomography.

  2. Rotationally resolved state-to-state photoionization and photoelectron study of titanium carbide and its cation (TiC/TiC{sup +})

    SciTech Connect

    Luo, Zhihong; Huang, Huang; Chang, Yih-Chung; Zhang, Zheng; Ng, C. Y.; Yin, Qing-Zhu

    2014-10-14

    Titanium carbide and its cation (TiC/TiC{sup +}) have been investigated by the two-color visible (VIS)-ultraviolet (UV) resonance-enhanced photoionization and pulsed field ionization-photoelectron (PFI-PE) methods. Two visible excitation bands for neutral TiC are observed at 16 446 and 16 930 cm{sup −1}. Based on rotational analyses, these bands are assigned as the respective TiC({sup 3}Π{sub 1}) ← TiC(X{sup 3}Σ{sup +}) and TiC({sup 3}Σ{sup +}) ← TiC(X{sup 3}Σ{sup +}) transition bands. This assignment supports that the electronic configuration and term symmetry for the neutral TiC ground state are …7σ{sup 2}8σ{sup 1}9σ{sup 1}3π{sup 4} (X{sup 3}Σ{sup +}). The rotational constant and the corresponding bond distance of TiC(X{sup 3}Σ{sup +}; v″ = 0) are determined to be B{sub 0}″ = 0.6112(10) cm{sup −1} and r{sub 0}″ = 1.695(2) Å, respectively. The rotational analyses of the VIS-UV-PFI-PE spectra for the TiC{sup +}(X; v{sup +} = 0 and 1) vibrational bands show that the electronic configuration and term symmetry for the ionic TiC{sup +} ground state are …7σ{sup 2}8σ{sup 1}3π{sup 4} (X{sup 2}Σ{sup +}) with the v{sup +} = 0 → 1 vibrational spacing of 870.0(8) cm{sup −1} and the rotational constants of B{sub e}{sup +} = 0.6322(28) cm{sup −1}, and α{sub e}{sup +} = 0.0085(28) cm{sup −1}. The latter rotational constants yield the equilibrium bond distance of r{sub e}{sup +} = 1.667(4) Å for TiC{sup +}(X{sup 2}Σ{sup +}). The cleanly rotationally resolved VIS-UV-PFI-PE spectra have also provided a highly precise value of 53 200.2(8) cm{sup −1} [6.5960(1) eV] for the adiabatic ionization energy (IE) of TiC. This IE(TiC) value along with the known IE(Ti) has made possible the determination of the difference between the 0 K bond dissociation energy (D{sub 0}) of TiC{sup +}(X{sup 2}Σ{sup +}) and that of TiC(X{sup 3}Σ{sup +}) to be D{sub 0}(Ti{sup +}−C) − D{sub 0}(Ti−C) = 0.2322(2) eV. Similar to previous experimental

  3. Dissociative Photoionization of Diethyl Ether.

    PubMed

    Voronova, Krisztina; Mozaffari Easter, Chrissa M; Covert, Kyle J; Bodi, Andras; Hemberger, Patrick; Sztáray, Bálint

    2015-10-29

    The dissociative photoionization of internal energy selected diethyl ether ions was investigated by imaging photoelectron photoion coincidence spectroscopy. In a large, 5 eV energy range Et2O(+) cations decay by two parallel and three sequential dissociative photoionization channels, which can be modeled well using statistical theory. The 0 K appearance energies of the CH3CHOCH2CH3(+) (H-loss, m/z = 73) and CH3CH2O═CH2(+) (methyl-loss, m/z = 59) fragment ions were determined to be 10.419 ± 0.015 and 10.484 ± 0.008 eV, respectively. The reemergence of the hydrogen-loss ion above 11 eV is attributed to transition-state (TS) switching, in which the second, outer TS is rate-determining at high internal energies. At 11.81 ± 0.05 eV, a secondary fragment of the CH3CHOCH2CH3(+) (m/z = 73) ion, protonated acetaldehyde, CH3CH═OH(+) (m/z = 45) appears. On the basis of the known thermochemical onset of this fragment, a reverse barrier of 325 meV was found. Two more sequential dissociation reactions were examined, namely, ethylene and formaldehyde losses from the methyl-loss daughter ion. The 0 K appearance energies of 11.85 ± 0.07 and 12.20 ± 0.08 eV, respectively, indicate no reverse barrier in these processes. The statistical model of the dissociative photoionization can also be used to predict the fractional ion abundances in threshold photoionization at large temperatures, which could be of use in, for example, combustion diagnostics. PMID:26444101

  4. Photoionization of atoms and molecules. [of hydrogen, helium, and xenon

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.

    1976-01-01

    A literature review on the present state of knowledge in photoionization is presented. Various experimental techniques that have been developed to study photoionization, such as fluorescence and photoelectron spectroscopy, mass spectroscopy, are examined. Various atoms and molecules were chosen to illustrate these techniques, specifically helium and xenon atoms and hydrogen molecules. Specialized photoionization such as in positive and negative ions, excited states, and free radicals is also treated. Absorption cross sections and ionization potentials are also discussed.

  5. Optimization of 4D vessel‐selective arterial spin labeling angiography using balanced steady‐state free precession and vessel‐encoding

    PubMed Central

    Schmitt, Peter; Bi, Xiaoming; Chappell, Michael A.; Tijssen, Rob H. N.; Sheerin, Fintan; Miller, Karla L.; Jezzard, Peter

    2016-01-01

    Vessel‐selective dynamic angiograms provide a wealth of useful information about the anatomical and functional status of arteries, including information about collateral flow and blood supply to lesions. Conventional x‐ray techniques are invasive and carry some risks to the patient, so non‐invasive alternatives are desirable. Previously, non‐contrast dynamic MRI angiograms based on arterial spin labeling (ASL) have been demonstrated using both spoiled gradient echo (SPGR) and balanced steady‐state free precession (bSSFP) readout modules, but no direct comparison has been made, and bSSFP optimization over a long readout period has not been fully explored. In this study bSSFP and SPGR are theoretically and experimentally compared for dynamic ASL angiography. Unlike SPGR, bSSFP was found to have a very low ASL signal attenuation rate, even when a relatively large flip angle and short repetition time were used, leading to a threefold improvement in the measured signal‐to‐noise ratio (SNR) efficiency compared with SPGR. For vessel‐selective applications, SNR efficiency can be further improved over single‐artery labeling methods by using a vessel‐encoded pseudo‐continuous ASL (VEPCASL) approach. The combination of a VEPCASL preparation with a time‐resolved bSSFP readout allowed the generation of four‐dimensional (4D; time‐resolved three‐dimensional, 3D) vessel‐selective cerebral angiograms in healthy volunteers with 59 ms temporal resolution. Good quality 4D angiograms were obtained in all subjects, providing comparable structural information to 3D time‐of‐flight images, as well as dynamic information and vessel selectivity, which was shown to be high. A rapid 1.5 min dynamic two‐dimensional version of the sequence yielded similar image features and would be suitable for a busy clinical protocol. Preliminary experiments with bSSFP that included the extracranial vessels showed signal loss in regions of poor magnetic field

  6. Quadrupole photoionization of hydrogen atoms in Debye plasmas

    SciTech Connect

    Lin, C. Y.; Ho, Y. K.

    2010-09-15

    Although a great deal of effort has been devoted to investigating dipole photoionization of plasma-embedded atoms, far less is known about the corresponding quadrupole transitions. In the present work, quadrupole photoionization processes for the ground and excited states of hydrogen atoms in Debye plasma are explored using the method of complex coordinate rotation. The plasma shielding effects on the quadrupole photoionization cross sections are reported for a variety of Debye screening lengths and compared to the dipole results accordingly. Under the perturbation of plasma screening, shape resonances and Cooper-type minima occurring in both dipole and quadrupole photoionization cross sections are presented and discussed. Comparisons are made to other theoretical calculations for the dipole photoionization with good agreement. The present quadrupole results are the first predictions for hydrogen photoionization in Debye plasmas.

  7. Molecular photoionization dynamics

    SciTech Connect

    Dehmer, Joseph L.

    1982-05-01

    This program seeks to develop both physical insight and quantitative characterization of molecular photoionization processes. Progress is briefly described, and some publications resulting from the research are listed. (WHK)

  8. IONIS: Approximate atomic photoionization intensities

    NASA Astrophysics Data System (ADS)

    Heinäsmäki, Sami

    2012-02-01

    A program to compute relative atomic photoionization cross sections is presented. The code applies the output of the multiconfiguration Dirac-Fock method for atoms in the single active electron scheme, by computing the overlap of the bound electron states in the initial and final states. The contribution from the single-particle ionization matrix elements is assumed to be the same for each final state. This method gives rather accurate relative ionization probabilities provided the single-electron ionization matrix elements do not depend strongly on energy in the region considered. The method is especially suited for open shell atoms where electronic correlation in the ionic states is large. Program summaryProgram title: IONIS Catalogue identifier: AEKK_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEKK_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 1149 No. of bytes in distributed program, including test data, etc.: 12 877 Distribution format: tar.gz Programming language: Fortran 95 Computer: Workstations Operating system: GNU/Linux, Unix Classification: 2.2, 2.5 Nature of problem: Photoionization intensities for atoms. Solution method: The code applies the output of the multiconfiguration Dirac-Fock codes Grasp92 [1] or Grasp2K [2], to compute approximate photoionization intensities. The intensity is computed within the one-electron transition approximation and by assuming that the sum of the single-particle ionization probabilities is the same for all final ionic states. Restrictions: The program gives nonzero intensities for those transitions where only one electron is removed from the initial configuration(s). Shake-type many-electron transitions are not computed. The ionized shell must be closed in the initial state. Running time: Few seconds for a

  9. Correlation between photoeletron and photoion in ultrafast multichannel photoionization of Ar

    SciTech Connect

    Itakura, R.; Fushitani, M.; Hishikawa, A.; Sako, T.

    2015-12-31

    We theoretically investigate coherent dynamics of ions created through ultrafast multichannel photoionization from a viewpoint of photoelectron-photoion correlation. The model calculation on single-photon ionization of Ar reveals that the coherent hole dynamics in Ar{sup +} associated with a superposition of the spin-orbit states {sup 2}PJ (J = 3/2 and 1/2) can be identified by monitoring only the photoion created by a Fourier-transform limited extreme ultraviolet (EUV) pulse with the fs pulse duration, while the coherence is lost by a chirped EUV pulse. It is demonstrated that by coincidence detection of the photoelectron and photoion the coherent hole dynamics can be extracted even in the case of ionization by a chirped EUV pulse with the sufficiently wide bandwidth.

  10. Photoionization and Recombination

    NASA Technical Reports Server (NTRS)

    Nahar, Sultana N.

    2000-01-01

    Theoretically self-consistent calculations for photoionization and (e + ion) recombination are described. The same eigenfunction expansion for the ion is employed in coupled channel calculations for both processes, thus ensuring consistency between cross sections and rates. The theoretical treatment of (e + ion) recombination subsumes both the non-resonant recombination ("radiative recombination"), and the resonant recombination ("di-electronic recombination") processes in a unified scheme. In addition to the total, unified recombination rates, level-specific recombination rates and photoionization cross sections are obtained for a large number of atomic levels. Both relativistic Breit-Pauli, and non-relativistic LS coupling, calculations are carried out in the close coupling approximation using the R-matrix method. Although the calculations are computationally intensive, they yield nearly all photoionization and recombination parameters needed for astrophysical photoionization models with higher precision than hitherto possible, estimated at about 10-20% from comparison with experimentally available data (including experimentally derived DR rates). Results are electronically available for over 40 atoms and ions. Photoionization and recombination of He-, and Li-like C and Fe are described for X-ray modeling. The unified method yields total and complete (e+ion) recombination rate coefficients, that can not otherwise be obtained theoretically or experimentally.

  11. Single and double photoionizations of methanal (formaldehyde)

    NASA Astrophysics Data System (ADS)

    Hochlaf, M.; Eland, J. H. D.

    2005-10-01

    Single and double photoionization spectra of formaldehyde have been measured at 40.81 and 48.37 eV photon energy and the spectrum of the doubly charged cation has been interpreted using high-level electronic structure calculations. The adiabatic double-ionization energy is determined as 31.7±0.25eV and the vertical ionization energy is 33 eV. The five lowest excited electronic states are identified and located. The potential-energy surfaces of the accessible states explain the lack of stable H2CO2+ dications and the lack of vibrational structure. The experimental double-ionization spectrum can be decomposed into two distinct contributions, one from direct photoionization and the second from indirect double photoionization by an inner-valence shell Auger effect.

  12. Density-matrix formalism for the photoion-electron entanglement in atomic photoionization

    SciTech Connect

    Radtke, T.; Fritzsche, S.; Surzhykov, A.

    2006-09-15

    The density-matrix theory, based on Dirac's relativistic equation, is applied for studying the entanglement between the photoelectron and residual ion in the course of the photoionization of atoms and ions. In particular, emphasis is placed on deriving the final-state density matrix of the overall system 'photoion+electron', including interelectronic effects and the higher multipoles of the radiation field. This final-state density matrix enables one immediately to analyze the change of entanglement as a function of the energy, angle and the polarization of the incoming light. Detailed computations have been carried out for the 5s photoionization of neutral strontium, leading to a photoion in a 5s {sup 2}S J{sub f}=1/2 level. It is found that the photoion-electron entanglement decreases significantly near the ionization threshold and that, in general, it depends on both the photon energy and angle. The possibility to extract photoion-electron pairs with a well-defined degree of entanglement may have far-reaching consequences for quantum information and elsewhere.

  13. Attosecond Delays in Resonant Photoionization

    NASA Astrophysics Data System (ADS)

    Maquet, Alfred

    2015-05-01

    Attosecond delays in the photoionization of atomic states have been evidenced in recent experiments performed in the 2010's. The delays were associated to the emission of photoelectron wave packets ejected from different atomic states, in the combined presence of attosecond pulses of XUV radiation and of a synchronized IR laser pulse, the latter being used as a reference ``clock''. These experiments were performed at XUV frequencies connecting the ground state to a ``flat'' continuum. Theoretical treatments were able to relate the measured delays to Wigner's definition of time delays in terms of the energy derivative of the phase-shift attached to the continuum wave functions of the photoelectrons. Attention has recently shifted towards the case of resonant photoionization in the course of which the XUV frequency is tuned close to a resonance of the target system. The case of a transition towards an autoionizing states of the target is particularly interesting as it makes evident the role of electronic correlations. Here, we shall present recent advances realized in the theoretical interpretation of this new class of experiments.

  14. Double Photoionization Near Threshold

    NASA Technical Reports Server (NTRS)

    Wehlitz, Ralf

    2007-01-01

    The threshold region of the double-photoionization cross section is of particular interest because both ejected electrons move slowly in the Coulomb field of the residual ion. Near threshold both electrons have time to interact with each other and with the residual ion. Also, different theoretical models compete to describe the double-photoionization cross section in the threshold region. We have investigated that cross section for lithium and beryllium and have analyzed our data with respect to the latest results in the Coulomb-dipole theory. We find that our data support the idea of a Coulomb-dipole interaction.

  15. Total quadruple photoionization cross section of beryllium

    SciTech Connect

    Emmanouilidou, Agapi

    2007-11-15

    In a quasiclassical framework, we formulate the quadruple ionization by single-photon absorption of the Coulomb five-body problem. We present the quadruple photoionization total cross section of the ground state of beryllium for energies up to 620 eV. Our results for energies close to threshold are in agreement with the Wannier threshold law for four-electron escape. In addition, the agreement of our results with a shape formula provides support for the overall shape of our total quadruple cross section. Finally, we find that the photon energy where the maximum of the total photoionization cross section occurs for single, double, triple, and quadruple photoionization of H, He, Li, and Be, respectively, seems to follow a linear relation with the threshold energy for complete breakup of the respective element.

  16. Comparative analysis of theories of relativistic photoionization

    NASA Astrophysics Data System (ADS)

    Hafizi, Bahman; Gordon, Daniel; Palastro, John

    2015-11-01

    Laser-plasma experiments routinely rely on photoionization for plasma formation. For large laser intensities or for high-Z atoms relativistic effects become important. We investigate a unique regime of relativistic photoionization from high-Z atoms where relativistic effects modify both the bound and continuum electronic states. Theories of photoionization are based on the imaginary time method and the S-matrix method, amongst others. We compare the results of these approaches for both the Dirac and the Klein-Gordon equations. Analytical results for the momentum distribution of ejected electrons and ionization rate are presented and compared with those from numerical solutions. Work supported by the Department of Energy and the NRL Base Program.

  17. Photoionization-photoelectron research

    SciTech Connect

    Berkowitz, J.; Ruscic, B.

    1993-12-01

    The photoionization research program is aimed at understanding the basic processes of interaction of vacuum ultraviolet (VUV) light with atoms and molecules. This research provides valuable information on both thermochemistry and dynamics. Recent studies include atoms, clusters, hydrides, sulfides and an important fluoride.

  18. Indirect double photoionization of water

    NASA Astrophysics Data System (ADS)

    Resccigno, T. N.; Sann, H.; Orel, A. E.; Dörner, R.

    2011-05-01

    The vertical double ionization thresholds of small molecules generally lie above the dissociation limits corresponding to formation of two singly charged fragments. This gives the possibility of populating singly charged molecular ions by photoionization in the Franck-Condon region at energies below the lowest dication state, but above the dissociation limit into two singly charged fragment ions. This process can produce a superexcited neutral fragment that autoionizes at large internuclear separation. We study this process in water, where absorption of a photon produces an inner-shell excited state of H2O+ that fragments to H++OH*. The angular distribution of secondary electrons produced by OH* when it autoionizes produces a characteristic asymmetric pattern that reveals the distance, and therefore the time, at which the decay takes place. LBNL, Berkeley, CA, J. W. Goethe Universität, Frankfurt, Germany. Work performed under auspices of US DOE and supported by OBES, Div. of Chemical Sciences.

  19. Absorption spectroscopy of a laboratory photoionized plasma experiment at Z

    SciTech Connect

    Hall, I. M.; Durmaz, T.; Mancini, R. C.; Bailey, J. E.; Rochau, G. A.; Golovkin, I. E.; MacFarlane, J. J.

    2014-03-15

    The Z facility at the Sandia National Laboratories is the most energetic terrestrial source of X-rays and provides an opportunity to produce photoionized plasmas in a relatively well characterised radiation environment. We use detailed atomic-kinetic and spectral simulations to analyze the absorption spectra of a photoionized neon plasma driven by the x-ray flux from a z-pinch. The broadband x-ray flux both photoionizes and backlights the plasma. In particular, we focus on extracting the charge state distribution of the plasma and the characteristics of the radiation field driving the plasma in order to estimate the ionisation parameter.

  20. Parallelizing the XSTAR Photoionization Code

    NASA Astrophysics Data System (ADS)

    Noble, M. S.; Ji, L.; Young, A.; Lee, J. C.

    2009-09-01

    We describe two means by which XSTAR, a code which computes physical conditions and emission spectra of photoionized gases, has been parallelized. The first is pvmxstar, a wrapper which can be used in place of the serial xstar2xspec script to foster concurrent execution of the XSTAR command line application on independent sets of parameters. The second is pmodel, a plugin for the Interactive Spectral Interpretation System (ISIS) which allows arbitrary components of a broad range of astrophysical models to be distributed across processors during fitting and confidence limits calculations, by scientists with little training in parallel programming. Plugging the XSTAR family of analytic models into pmodel enables multiple ionization states (e.g., of a complex absorber/emitter) to be computed simultaneously, alleviating the often prohibitive expense of the traditional serial approach. Initial performance results indicate that these methods substantially enlarge the problem space to which XSTAR may be applied within practical timeframes.

  1. Shape resonant features in the photoionization spectra of NO

    SciTech Connect

    Wallace, Scott; Dill, Dan; Dehmer, Joseph L.

    1982-01-01

    Calculations of core and valence level photoionization spectra of NO are presented and compared with available experimental data. A low-lying continuum shape resonance is identified in the sigma photoionization channel, which is the analog of similar states found in other first-row diatomic molecules. Both partial cross sections and photoelectron angular distributions are discussed, and the effect of nuclear motion on these observables is treated.

  2. Absolute photoionization cross sections of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Pareek, P. N.

    1985-01-01

    The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states.

  3. Absolute photoionization cross sections of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Pareek, P. N.

    1982-01-01

    The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states.

  4. Alignment of Ar{sup +} [{sup 3}P]4p{sup 2}P{sup 0}{sub 3/2} satellite state from the polarization analysis of fluorescent radiation after photoionization

    SciTech Connect

    Yenen, O.; McLaughlin, K.W.; Jaecks, D.H.

    1997-04-01

    The measurement of the polarization of radiation from satellite states of Ar{sup +} formed after the photoionization of Ar provides detailed information about the nature of doubly excited states, magnetic sublevel cross sections and partial wave ratios of the photo-ejected electrons. Since the formation of these satellite states is a weak process, it is necessary to use a high flux beam of incoming photons. In addition, in order to resolve the many narrow doubly excited Ar resonances, the incoming photons must have a high resolution. The characteristics of the beam line 9.0.1 of the Advanced Light Source fulfill these requirements. The authors determined the polarization of 4765 {Angstrom} fluorescence from the Ar{sup +} [{sup 3}P] 4p {sup 2}P{sub 3/2}{sup 0} satellite state formed after photoionization of Ar by photons from the 9.0.1 beam line of ALS in the 35.620-38.261 eV energy range using a resolution of approximately 12,700. This is accomplished by measuring the intensities of the fluorescent light polarized parallel (I{parallel}) and perpendicular (I{perpendicular}) to the polarization axis of the incident synchrotron radiation using a Sterling Optics 105MB polarizing filter. The optical system placed at 90{degrees} with respect to the polarization axis of the incident light had a narrow band interference filter ({delta}{lambda}=0.3 nm) to isolate the fluorescent radiation.

  5. Photoionization-photoelectron research.

    SciTech Connect

    Ruscic, B.

    1998-03-06

    In the broad sense of a general definition, the fundamental goal of this research program is to explore, understand, and utilize the basic processes of interaction of vacuum UV light with atoms and molecules. In practical terms, this program uses photoionization mass spectrometry and other related techniques to study chemically relevant transient and metastable species that are intimately connected to energy-producing processes, such as combustion, or play-prominent roles in the associated environmental issues. Some recent examples of species that have been studied are: CH{sub 3}, CH{sub 2}, CH{sub 3}O, CH{sub 2}OH, CH{sub 3}S, CH{sub 2}SH, HCS, HNCO, NCO, HNCS, NCS, the isomers of C{sub 2}H{sub 5}O, HOBr, CF{sub 3} and CF{sub 3}OH. The ephemeral species of interest are produced in situ using various suitable techniques, such as sublimation, pyrolysis, microwave discharge, chemical abstraction reactions with H or F atoms, laser photodissociation, on-line synthesis, and others. The desired information is obtained by applying a variety of suitable photoionization methods, which use both conventional and coherent light sources in the vacuum W region. The spiritus movens of our studies is the need to provide the chemical community with essential information on the species of interest, such as accurate and reliable thermochemical, spectroscopic and structural data, and thus contribute to the global comprehension of the underlying chemical processes. The scientific motivation is also fueled by the necessity to unveil useful generalities, such as bonding patterns within a class of related compounds, or systematic behavior in the ubiquitous autoionization processes. In addition, the nature of the results obtained in this program is such that it generates a significant impetus for further theoretical work. The experimental work of this program is coordinated with other related experimental and theoretical efforts of the Chemical Dynamics Group to provide a broad perspective

  6. Advances in 4D radiation therapy for managing respiration: part II - 4D treatment planning.

    PubMed

    Rosu, Mihaela; Hugo, Geoffrey D

    2012-12-01

    The development of 4D CT imaging technology made possible the creation of patient models that are reflective of respiration-induced anatomical changes by adding a temporal dimension to the conventional 3D, spatial-only, patient description. This had opened a new venue for treatment planning and radiation delivery, aimed at creating a comprehensive 4D radiation therapy process for moving targets. Unlike other breathing motion compensation strategies (e.g. breath-hold and gating techniques), 4D radiotherapy assumes treatment delivery over the entire respiratory cycle - an added bonus for both patient comfort and treatment time efficiency. The time-dependent positional and volumetric information holds the promise for optimal, highly conformal, radiotherapy for targets experiencing movements caused by respiration, with potentially elevated dose prescriptions and therefore higher cure rates, while avoiding the uninvolved nearby structures. In this paper, the current state of the 4D treatment planning is reviewed, from theory to the established practical routine. While the fundamental principles of 4D radiotherapy are well defined, the development of a complete, robust and clinically feasible process still remains a challenge, imposed by limitations in the available treatment planning and radiation delivery systems.

  7. Advances in 4D Radiation Therapy for Managing Respiration: Part II – 4D Treatment Planning

    PubMed Central

    Rosu, Mihaela; Hugo, Geoffrey D.

    2014-01-01

    The development of 4D CT imaging technology made possible the creation of patient models that are reflective of respiration-induced anatomical changes by adding a temporal dimension to the conventional 3D, spatial-only, patient description. This had opened a new venue for treatment planning and radiation delivery, aimed at creating a comprehensive 4D radiation therapy process for moving targets. Unlike other breathing motion compensation strategies (e.g. breath-hold and gating techniques), 4D radiotherapy assumes treatment delivery over the entire respiratory cycle – an added bonus for both patient comfort and treatment time efficiency. The time-dependent positional and volumetric information holds the promise for optimal, highly conformal, radiotherapy for targets experiencing movements caused by respiration, with potentially elevated dose prescriptions and therefore higher cure rates, while avoiding the uninvolved nearby structures. In this paper, the current state of the 4D treatment planning is reviewed, from theory to the established practical routine. While the fundamental principles of 4D radiotherapy are well defined, the development of a complete, robust and clinically feasible process still remains a challenge, imposed by limitations in the available treatment planning and radiation delivery systems. PMID:22796324

  8. 2008 Photoions, Photoionization & Photodetachment Gordon Research Conference January 27-February 1, 2008

    SciTech Connect

    Klaus Muller-Dethefs Nancy Ryan GRay

    2009-03-31

    This conference brings together scientists interested in a range of basic phenomena linked to the ejection and scattering of electrons from atoms, molecules, clusters, liquids and solids by absorption of light. Photoionization, a highly sensitive probe of both structure and dynamics, can range from perturbative single-photon processes to strong-field highly non-perturbative interactions. It is responsible for the formation and destruction of molecules in astrophysical and plasma environments and successfully used in advanced analytical techniques. Positive ions, which can be produced and studied most effectively using photoionization, are the major components of all plasmas, vital constituents of flames and important intermediates in many chemical reactions. Negative ions are significant as transient species and, when photodetached, the corresponding neutral species often undergoes remarkable, otherwise non-observable, dynamics. The scope of the meeting spans from novel observations in atomic and molecular physics, such as Coulomb Crystals, highly excited states and cold Rydberg plasmas, to novel energy resolved or ultrafast time-resolved experiments, photoionization in strong laser fields, theoretical method development for electron scattering, photoionization and photodetachment and more complex phenomena such as charge transfer and DNA and protein conductivity, important for biological and analytical applications.

  9. Photoionization and electron-ion recombination of Ti I

    NASA Astrophysics Data System (ADS)

    Nahar, Sultana N.

    2016-07-01

    Study of the inverse processes of photoionization and electron-ion recombination of (Ti I + h ν ⇋ Ti II + e) using the unified method is reported. The method, based on close coupling (CC) approximation and R-matrix method, subsumes both the radiative recombination (RR) and dielectronic recombination (DR) in a unified manner and provides state-specific and total electron-ion recombination rate coefficients which are self-consistent with the state-specific photoionization cross sections. The present results include state-specific electron-ion recombination rates (αRC(i))and partial photoionization cross sections (σPI(i)) leaving the ion in the ground state of 813 bound states with n ≤ 10 and l ≤ 9 of Ti I. Various features of state-specific and total electron-ion recombination with temperature, and the corresponding photoionization cross sections with energies are discussed with illustrations. Due to closely lying excited states near the ground state of the core, photoionization cross sections show presence of narrow Rydberg resonances in low energy region near the ionization threshold. Many excited states also show broad and enhanced Seaton resonances due to PEC (photo-excitation-of-core) which contribute to the high temperature recombination. The total recombination rate coefficient is found to show a low hump around temperature 280 K and a high dielectronic recombination peak at temperature 25,000 K. Total spectrum of recombination cross sections and rates with photoelectron energy are also presented for experimental observation. Calculations were carried out using a CC wave function expansion of 36 states of the core ion Ti II. The large set of data for recombination rates and partial photoionization cross sections with resonances should provide a complete and accurate modelings of plasmas.

  10. Application of a VMI spectrometer to near-threshold photoionization with synchrotron radiation

    NASA Astrophysics Data System (ADS)

    O'Keeffe, P.; Bolognesi, P.; Mihelic, A.; Richter, R.; Moise, A.; Ovcharenko, E.; King, G. C.; Avaldi, L.

    2011-04-01

    A new developed velocity map imaging spectrometer has been used to study the photoionization of atoms near threshold. The application of the spectrometer to the measurement of the angular distributions of the photoelectrons emitted in the photoionization of the Ne 2p3/2 state between the 2p spin orbit thresholds and of polarised Ne atoms are presented.

  11. Double photoionization of doubly-excited lithium

    NASA Astrophysics Data System (ADS)

    Armstrong, G.; Pindzola, M. S.; Kheifets, A.; Schuricke, M.; Veeravalli, G.; Dornes, Ch.; Zhu, G.; Joachimsmeyer, K.; Treusch, R.; Dorn, A.; Colgan, J.

    2012-06-01

    We present triple differential cross sections and recoil ion momentum distributions for double photoionization of the 1s2s2p state of lithium. Double ionization of lithium may be treated as a two-active-electron process, where the ``active'' 2s and 2p electrons move in the field of the ``frozen-core'' Li^2+ 1s state.The time-dependent close-coupling (TDCC) method is used to solve the two-electron time-dependent Schr"odinger equation in full dimensionality. This work is motivated by recent FLASH experiments, which have obtained recoil-ion momentum distributions at a photon energy of 59 eV, where the 1s2s2p state is first reached via a 1s-2p photoexcitation from the initial ground state, and may then be doubly-ionized after the absorption of a second photon. The TDCC calculations in this work treat the subsequent photoionization of this doubly-excited state. The results are compared to those obtained by the convergent close-coupling method and to measurement, and provide a first comparison between theory and experiment in this fundamental few-photon few-body problem.

  12. Photoionization of Xe inside C{sub 60}: Atom-fullerene hybridization, giant cross-section enhancement, and correlation confinement resonances

    SciTech Connect

    Madjet, Mohamed E.; Renger, Thomas; Hopper, Dale E.; McCune, Matthew A.; Chakraborty, Himadri S.; Rost, Jan-M.; Manson, Steven T.

    2010-01-15

    A theoretical study of the subshell photoionization of the Xe atom endohedrally confined in C{sub 60} is presented. Powerful hybridization of the Xe 5s state with the bottom edge of C{sub 60} pi band is found that induces strong structures in the 5s ionization, causing the cross section to differ significantly from earlier results that omit this hybridization. The hybridization also affects the angular distribution asymmetry parameter of Xe 5p ionization near the Cooper minimum. The 5p cross section, on the other hand, is greatly enhanced by borrowing considerable oscillator strength from the C{sub 60} giant plasmon resonance via the atom-fullerene dynamical interchannel coupling. Beyond the C{sub 60} plasmon energy range the atomic subshell cross sections display confinement-induced oscillations in which, over the large 4d shape resonance region, the dominant 4d oscillations induce their 'clones' in all degenerate weaker channels known as correlation confinement resonances.

  13. Photoionization Dynamics of Small Molecules

    SciTech Connect

    Dehmer, Joseph L.; Dill, Dan; Parr, Albert C.

    1985-01-01

    The last decade has witnessed remarkable progress in characterizing dynamical aspects of the molecular photoionization process. The general challenge is to gain physical insight into those processes occuring during photo excitation and eventual escape of the photoelectron through the anisotropic molecular field, in terms of various observables such as photoionization cross-sections and branching ratios, photoelectron angular distributions and even newer probes mentioned below. Much of the progress in this field has mirrored earlier work in atomic photoionization dynamics where many key ideas were developed (e.g., channel interaction, quantum defect analysis, potential barrier phenomena and experimental techniques). However, additional concepts and techniques were required to deal with the strictly molecular aspects of the problem, particularly the anisotropy of the multicenter molecular field and the interaction among rovibronic modes.

  14. Double Photoionization of Aligned Molecular Hydrogen

    SciTech Connect

    Vanroose, Wim; Horner, Daniel A.; Martin, Fernando; Rescigno,Thomas N.; McCurdy, C. William

    2006-07-21

    We present converged, completely ab initio calculations ofthe triple differential cross sections for double photoionization ofaligned H2 molecules for a photon energy of 75.0 eV. The method ofexterior complex scaling, implemented with both the discrete variablerepresentation and B-splines, is used to solve the Schroedinger equationfor a correlated continuum wave function corresponding to a single photonhaving been absorbed by a correlated initial state. Results for a fixedinternuclear distance are compared with recent experiments and show thatintegration over experimental angular and energy resolutions is necessaryto produce good qualitative agreement, but does not eliminate somediscrepancies. Limitations of current experimental resolution are shownto sometimes obscure interesting details of the crosssection.

  15. VUV state-selected photoionization of thermally-desorbed biomolecules by coupling an aerosol source to an imaging photoelectron/photoion coincidence spectrometer: case of the amino acids tryptophan and phenylalanine.

    PubMed

    Gaie-Levrel, François; Garcia, Gustavo A; Schwell, Martin; Nahon, Laurent

    2011-04-21

    Gas phase studies of biological molecules provide structural and dynamical information on isolated systems. The lack of inter- or intra-molecular interactions facilitates the interpretation of the experimental results through theoretical calculations, and constitutes an informative complement to the condensed phase. However advances in the field are partially hindered by the difficulty of vaporising these systems, most of which are thermally unstable. In this work we present a newly developed aerosol mass thermodesorption setup, which has been coupled to a Velocity Map Imaging (VMI) analyzer operated in coincidence with a Wiley-McLaren Time of Flight spectrometer, using synchrotron radiation as a single photon ionization source. Although it has been previously demonstrated that thermolabile molecules such as amino acids can be produced intact by the aerosol vaporisation technique, we show how its non-trivial coupling to a VMI analyzer plus the use of electron/ion coincidences greatly improves the concept in terms of the amount of spectroscopic and dynamic information that can be extracted. In this manner, we report on the valence shell ionization of two amino acids, tryptophan and phenylalanine, for which threshold photoelectron spectra have been recorded within the first 3 eV above the first ionization energy using synchrotron radiation emitted from the DESIRS beamline located at SOLEIL in France. Their adiabatic ionization energies (IEs) have been measured at 7.40 ± 0.05 and 8.65 ± 0.02 eV, respectively, and their spectra analyzed using existing theoretical data from the literature. The IE values agree well with previously published ones, but are given here with a considerably reduced uncertainty by up to a factor of 5. The photostability of both amino acids is also described in detail, through the measurement of the state-selected fragmentation pathways via the use of threshold electron/ion coincidences (TPEPICO), with appearance energies for the different

  16. Near-Threshold, Vibrationally-Resolved Photoionization of Molecular Nitrogen

    NASA Astrophysics Data System (ADS)

    Vangyseghem, Gaetan; Gorczyca, Thomas; Ballance, Connor

    2016-05-01

    Photoionization of molecular nitrogen N2 is investigated near the first ionization threshold using an R-matrix, multi-channel quantum defect theory (MQDT) approach. Building on an existing fixed-nuclei R-matrix photoionization model, which, in turn, is built on the UKRmol suite of codes, photoionization cross sections, as well as scattering and dipole matrices, are computed in the Born-Oppenheimer approximation. By varying the internuclear separation, potential energy curves have been constructed for the N2 and N 2 + states and compared to quantum chemistry calculations. Using these fixed-nuclei potential energy curves, and corresponding vibronic eigenenergies and eigenfunctions, a frame transformation is enacted on the fixed-nuclei scattering and dipole matrices, allowing for the calculation of vibrationally-resolved photoionization cross sections. The resultant photoionization cross sections are compared to high-resolution experimental data near threshold, a region complicated by multiple vibrationally-resolved, interacting Rydberg series.

  17. Rotationally resolved photoionization with coherent VUV radiation

    SciTech Connect

    Wiedmann, R.T.; Tonkyn, R.G.; White, M.G.

    1992-09-01

    Pulsed field ionization (PFI) has been used in conjunction with coherent VUV radiation to investigate the rotational state distributions of molecular cations following single photon ionization. The rotational state distributions for several linear cations (O{sub 2}, NO, OH(OD), HCl and N{sub 2}0) can be interpreted predominately on the basis of the near-threshold, one-electron photoionization dynamics; however, field-induced autoionization is often the dominate ionization pathway for rotational branches involving negative changes in core angular momentum. For photoionization of the H{sub 2}X (X = 0, S) non-linear triatomic molecules, transitions between asymmetric top levels involving the rotational angular momentum projections, K{sub a} and K{sub c} permit resolution of the photoelectron continua according to symmetry. The observed spectra clearly demonstrate the importance of the non-spherical nature of the molecular ion potential which leads to photoelectron final states which are unexpected from atomic-like analogies.

  18. Rotationally resolved photoionization with coherent VUV radiation

    SciTech Connect

    Wiedmann, R.T.; Tonkyn, R.G.; White, M.G.

    1992-01-01

    Pulsed field ionization (PFI) has been used in conjunction with coherent VUV radiation to investigate the rotational state distributions of molecular cations following single photon ionization. The rotational state distributions for several linear cations (O{sub 2}, NO, OH(OD), HCl and N{sub 2}0) can be interpreted predominately on the basis of the near-threshold, one-electron photoionization dynamics; however, field-induced autoionization is often the dominate ionization pathway for rotational branches involving negative changes in core angular momentum. For photoionization of the H{sub 2}X (X = 0, S) non-linear triatomic molecules, transitions between asymmetric top levels involving the rotational angular momentum projections, K{sub a} and K{sub c} permit resolution of the photoelectron continua according to symmetry. The observed spectra clearly demonstrate the importance of the non-spherical nature of the molecular ion potential which leads to photoelectron final states which are unexpected from atomic-like analogies.

  19. Mass-Selective Laser Photoionization.

    ERIC Educational Resources Information Center

    Smalley, R. E.

    1982-01-01

    Discusses the nature and applications of mass-selective laser photoionization. The ionization can be done with a single intense laser pulse lasting a few billionths of a second with no molecular fragmentation. Applications focus on: (1) benzene clusters, excimers, and exciplexes; (2) metal clusters; and (3) triplet formation and decay. (Author/JN)

  20. Soft Route to 4D Tomography.

    PubMed

    Taillandier-Thomas, Thibault; Roux, Stéphane; Hild, François

    2016-07-01

    Based on the assumption that the time evolution of a sample observed by computed tomography requires many less parameters than the definition of the microstructure itself, it is proposed to reconstruct these changes based on the initial state (using computed tomography) and very few radiographs acquired at fixed intervals of time. This Letter presents a proof of concept that for a fatigue cracked sample its kinematics can be tracked from no more than two radiographs in situations where a complete 3D view would require several hundreds of radiographs. This 2 order of magnitude gain opens the way to a "computed" 4D tomography, which complements the recent progress achieved in fast or ultrafast computed tomography, which is based on beam brightness, detector sensitivity, and signal acquisition technologies.

  1. Soft Route to 4D Tomography

    NASA Astrophysics Data System (ADS)

    Taillandier-Thomas, Thibault; Roux, Stéphane; Hild, François

    2016-07-01

    Based on the assumption that the time evolution of a sample observed by computed tomography requires many less parameters than the definition of the microstructure itself, it is proposed to reconstruct these changes based on the initial state (using computed tomography) and very few radiographs acquired at fixed intervals of time. This Letter presents a proof of concept that for a fatigue cracked sample its kinematics can be tracked from no more than two radiographs in situations where a complete 3D view would require several hundreds of radiographs. This 2 order of magnitude gain opens the way to a "computed" 4D tomography, which complements the recent progress achieved in fast or ultrafast computed tomography, which is based on beam brightness, detector sensitivity, and signal acquisition technologies.

  2. MRCI study of spectroscopic and molecular properties of X2Πg, a 4Πu, A2Πu, b 4 ? , D2Δg and B2 ? electronic states of ? ion

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoniu; Shi, Deheng; Sun, Jinfeng; Zhu, Zunlue

    2011-06-01

    The potential energy curves (PECs) of six low-lying electronic states (X2Πg, a 4Πu, A2Πu, b 4 ? , D2Δg and B2 ? ) of ? ion were studied by the ab initio quantum chemical method. The calculations were carried out with the full valence complete active space self-consistent field (CASSCF) method followed by the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach in combination with large correlation-consistent basis sets. Effects on the PECs of the core-valence correlation and relativistic corrections are taken into account. The way to consider the relativistic correction is to use the second-order Douglas-Kroll Hamiltonian (DKH2) approximation. The core-valence correlation correction is carried out with the cc-pCVQZ basis set, and the relativistic correction is performed at the level of cc-pVQZ basis set. To obtain more reliable results, the PECs determined by the MRCI calculations are also corrected for size-extensivity errors by means of the Davidson modification (MRCI + Q). These PECs are extrapolated to the complete basis set (CBS) limit by the two-point total-energy extrapolation scheme. With these PECs, the spectroscopic parameters (Te , De , D 0, Re , ωe , ωexe , αe and Be ) are determined and compared with those reported in the literature. The conclusion can be reached that the effect on the spectroscopic parameters of the core-valence correlation correction is larger than that of the relativistic correction. With the PECs obtained by the MRCI + Q/CV+DK+56 calculations, the vibrational levels and inertial rotation constants of the first 26 vibrational states are determined for these electronic states of non-rotating ? ion. Comparison with the experimental data shows that the present spectroscopic parameters and molecular constants are accurate.

  3. 4-D OCT in Developmental Cardiology

    NASA Astrophysics Data System (ADS)

    Jenkins, Michael W.; Rollins, Andrew M.

    Although strong evidence exists to suggest that altered cardiac function can lead to CHDs, few studies have investigated the influential role of cardiac function and biophysical forces on the development of the cardiovascular system due to a lack of proper in vivo imaging tools. 4-D imaging is needed to decipher the complex spatial and temporal patterns of biomechanical forces acting upon the heart. Numerous solutions over the past several years have demonstrated 4-D OCT imaging of the developing cardiovascular system. This chapter will focus on these solutions and explain their context in the evolution of 4-D OCT imaging. The first sections describe the relevant techniques (prospective gating, direct 4-D imaging, retrospective gating), while later sections focus on 4-D Doppler imaging and measurements of force implementing 4-D OCT Doppler. Finally, the techniques are summarized, and some possible future directions are discussed.

  4. 4D-DSA and 4D fluoroscopy: preliminary implementation

    NASA Astrophysics Data System (ADS)

    Mistretta, C. A.; Oberstar, E.; Davis, B.; Brodsky, E.; Strother, C. M.

    2010-04-01

    We have described methods that allow highly accelerated MRI using under-sampled acquisitions and constrained reconstruction. One is a hybrid acquisition involving the constrained reconstruction of time dependent information obtained from a separate scan of longer duration. We have developed reconstruction algorithms for DSA that allow use of a single injection to provide the temporal data required for flow visualization and the steady state data required for construction of a 3D-DSA vascular volume. The result is time resolved 3D volumes with typical resolution of 5123 at frame rates of 20-30 fps. Full manipulation of these images is possible during each stage of vascular filling thereby allowing for simplified interpretation of vascular dynamics. For intravenous angiography this time resolved 3D capability overcomes the vessel overlap problem that greatly limited the use of conventional intravenous 2D-DSA. Following further hardware development, it will be also be possible to rotate fluoroscopic volumes for use as roadmaps that can be viewed at arbitrary angles without a need for gantry rotation. The most precise implementation of this capability requires availability of biplane fluoroscopy data. Since the reconstruction of 3D volumes presently suppresses the contrast in the soft tissue, the possibility of using these techniques to derive complete indications of perfusion deficits based on cerebral blood volume (CBV), mean transit time (MTT) and time to peak (TTP) parameters requires further investigation. Using MATLAB post-processing, successful studies in animals and humans done in conjunction with both intravenous and intra-arterial injections have been completed. Real time implementation is in progress.

  5. Molecular photoionization processes of astrophysical and aeronomical interest

    NASA Technical Reports Server (NTRS)

    Langhoff, P. W.

    1985-01-01

    An account is given of aspects of photoionization processes in molecules, with particular reference to recent theoretical and experimental studies of partial cross sections for production of specific final electronic states and of parent and fragment ions. Such cross sections help provide a basis for specifying the state of excitation of the ionized medium, are useful for estimating the kinetic energy distributions of photoejected electrons and fragment ions, provide parent-and fragment-ion yields, and clarify the possible origins of neutral fragments in highly excited rovibronic states. A descriptive account is given of photoionization phenomena, including tabulation of valence- and inner-shell potentials for some molecules of astrophysical and aeronomical interest. Cross sectional expressions are given. Various approximations currently employed in computational studies are described briefly, threshold laws and high-energy limits are indicated, and distinction is drawn between resonant and direct photoionization phenomena. Recent experimental and theoretical studies of partial photoionization cross sections in selected compounds of astrophysical and aeronomical relevance are described and discussed.

  6. Photoionization Dynamics in Pure Helium Droplets

    SciTech Connect

    Peterka, Darcy S.; Kim, Jeong Hyun; Wang, Chia C.; Poisson,Lionel; Neumark, Daniel M.

    2007-02-04

    The photoionization and photoelectron spectroscopy of pure He droplets are investigated at photon energies between 24.6 eV (the ionization energy of He) and 28 eV. Time-of-flight mass spectra and photoelectron images were obtained at a series of molecular beam source temperatures and pressures to assess the effect of droplet size on the photoionization dynamics. At source temperatures below 16 K, the photoelectron images are dominated by fast electrons produced via direct ionization of He atoms, with a small contribution from very slow electrons with kinetic energies below 1 meV arising from an indirect mechanism. The fast photoelectrons have as much as 0.5 eV more kinetic energy than those from atomic He at the same photon energy. This result is interpreted and simulated within the context of a 'dimer model', in which one assumes vertical ionization from two nearest neighbor He atoms to the attractive region of the He2+ potential energy curve. Possible mechanism for the slow electrons, which were also seen at energies below IE(He), are discussed, including vibrational autoionizaton of Rydberg states comprising an electron weakly bound to the surface of a large HeN+ core.

  7. Advances in 4D radiation therapy for managing respiration: part I - 4D imaging.

    PubMed

    Hugo, Geoffrey D; Rosu, Mihaela

    2012-12-01

    Techniques for managing respiration during imaging and planning of radiation therapy are reviewed, concentrating on free-breathing (4D) approaches. First, we focus on detailing the historical development and basic operational principles of currently-available "first generation" 4D imaging modalities: 4D computed tomography, 4D cone beam computed tomography, 4D magnetic resonance imaging, and 4D positron emission tomography. Features and limitations of these first generation systems are described, including necessity of breathing surrogates for 4D image reconstruction, assumptions made in acquisition and reconstruction about the breathing pattern, and commonly-observed artifacts. Both established and developmental methods to deal with these limitations are detailed. Finally, strategies to construct 4D targets and images and, alternatively, to compress 4D information into static targets and images for radiation therapy planning are described.

  8. Advances in 4D Radiation Therapy for Managing Respiration: Part I – 4D Imaging

    PubMed Central

    Hugo, Geoffrey D.; Rosu, Mihaela

    2014-01-01

    Techniques for managing respiration during imaging and planning of radiation therapy are reviewed, concentrating on free-breathing (4D) approaches. First, we focus on detailing the historical development and basic operational principles of currently-available “first generation” 4D imaging modalities: 4D computed tomography, 4D cone beam computed tomography, 4D magnetic resonance imaging, and 4D positron emission tomography. Features and limitations of these first generation systems are described, including necessity of breathing surrogates for 4D image reconstruction, assumptions made in acquisition and reconstruction about the breathing pattern, and commonly-observed artifacts. Both established and developmental methods to deal with these limitations are detailed. Finally, strategies to construct 4D targets and images and, alternatively, to compress 4D information into static targets and images for radiation therapy planning are described. PMID:22784929

  9. Attosecond Delays in Molecular Photoionization

    NASA Astrophysics Data System (ADS)

    Huppert, Martin; Jordan, Inga; Baykusheva, Denitsa; von Conta, Aaron; Wörner, Hans Jakob

    2016-08-01

    We report measurements of energy-dependent photoionization delays between the two outermost valence shells of N2O and H2O . The combination of single-shot signal referencing with the use of different metal foils to filter the attosecond pulse train enables us to extract delays from congested spectra. Remarkably large delays up to 160 as are observed in N2O , whereas the delays in H2O are all smaller than 50 as in the photon-energy range of 20-40 eV. These results are interpreted by developing a theory of molecular photoionization delays. The long delays measured in N2O are shown to reflect the population of molecular shape resonances that trap the photoelectron for a duration of up to ˜110 as. The unstructured continua of H2O result in much smaller delays at the same photon energies. Our experimental and theoretical methods make the study of molecular attosecond photoionization dynamics accessible.

  10. Attosecond Delays in Molecular Photoionization.

    PubMed

    Huppert, Martin; Jordan, Inga; Baykusheva, Denitsa; von Conta, Aaron; Wörner, Hans Jakob

    2016-08-26

    We report measurements of energy-dependent photoionization delays between the two outermost valence shells of N_{2}O and H_{2}O. The combination of single-shot signal referencing with the use of different metal foils to filter the attosecond pulse train enables us to extract delays from congested spectra. Remarkably large delays up to 160 as are observed in N_{2}O, whereas the delays in H_{2}O are all smaller than 50 as in the photon-energy range of 20-40 eV. These results are interpreted by developing a theory of molecular photoionization delays. The long delays measured in N_{2}O are shown to reflect the population of molecular shape resonances that trap the photoelectron for a duration of up to ∼110 as. The unstructured continua of H_{2}O result in much smaller delays at the same photon energies. Our experimental and theoretical methods make the study of molecular attosecond photoionization dynamics accessible. PMID:27610849

  11. Decoherence in attosecond photoionization.

    PubMed

    Pabst, Stefan; Greenman, Loren; Ho, Phay J; Mazziotti, David A; Santra, Robin

    2011-02-01

    The creation of superpositions of hole states via single-photon ionization using attosecond extreme-ultraviolet pulses is studied with the time-dependent configuration-interaction singles (TDCIS) method. Specifically, the degree of coherence between hole states in atomic xenon is investigated. We find that interchannel coupling not only affects the hole populations, but it also enhances the entanglement between the photoelectron and the remaining ion, thereby reducing the coherence within the ion. As a consequence, even if the spectral bandwidth of the ionizing pulse exceeds the energy splittings among the hole states involved, perfectly coherent hole wave packets cannot be formed. For sufficiently large spectral bandwidth, the coherence can only be increased by increasing the mean photon energy.

  12. Radiative properties measurements of photoionized plasmas on Z

    NASA Astrophysics Data System (ADS)

    Loisel, Guillaume; Bailey, Jim; Nagayama, Taisuke; Hansen, Stephanie; Rochau, Greg; Liedahl, Duane; Fontes, Chris; Flaugh, Matt; Koepke, Mark; Lane, Ted; Mancini, Roberto

    2015-11-01

    Physical descriptions of accretion-powered objects such as black holes, x-ray binaries, or AGN are informed through the interpretation of emergent spectra from the photoionized plasmas that surround them. Line formation in photoionized plasmas is dependent on the details of the radiation transport treatment and the so-called Resonant Auger Destruction hypothesis typically required to interpret the relativistically broadened Fe K α emitted from near the black hole event horizon. The Z facility at Sandia National Laboratories can produced such photoionized plasmas producing 1.6MJ of x-rays from the z-pinch dynamic hohlraum. The extended suite of diagnostics allows for a detailed characterization of plasmas conditions through absorption spectroscopy. present accurate and high-resolution emergent intensity observed from a photoionized silicon plasma for a discrete set of column densities that will help us evaluate understanding for radiation transport in accretion powered objects. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000.

  13. Photoionization cross sections and oscillator strengths of neutral cesium

    NASA Astrophysics Data System (ADS)

    Haq, S. U.; Nadeem, Ali; Nawaz, M.

    2012-11-01

    The absolute photoionization cross sections from the 6p 2P1/2 excited state of cesium at threshold and above the threshold region have been measured using the saturation absorption technique. The photoionization cross section at the ionization threshold is determined as 22.6±3.6 Mb, whereas in the region above threshold its value ranges from 22 to 20 Mb for photoelectron energies up to 0.1 eV. A comparison of the photoionization cross sections with earlier reported theoretical and experimental data have been presented and are in good agreement within the uncertainty. In addition, the oscillator strengths of the 6p 2P1/2→n d 2D3/2 (21≤n≤60) Rydberg transitions of cesium have been calibrated using the threshold value of the photoionization cross section. A complete picture of the oscillator strengths from the present work and previously reported data from n=5-60 is presented.

  14. Los Alamos National Laboratory 4D Database

    SciTech Connect

    Atencio, Julian J.

    2014-05-02

    4D is an integrated development platform - a single product comprised of the components you need to create and distribute professional applications. You get a graphical design environment, SQL database, a programming language, integrated PHP execution, HTTP server, application server, executable generator, and much more. 4D offers multi-platform development and deployment, meaning whatever you create on a Mac can be used on Windows, and vice-versa. Beyond productive development, 4D is renowned for its great flexibility in maintenance and modification of existing applications, and its extreme ease of implementation in its numerous deployment options. Your professional application can be put into production more quickly, at a lower cost, and will always be instantly scalable. 4D makes it easy, whether you're looking to create a classic desktop application, a client-server system, a distributed solution for Web or mobile clients - or all of the above!

  15. Relative charge transfer cross section from Rb (4d)

    NASA Astrophysics Data System (ADS)

    Shah, M. H.; Camp, H. A.; Trachy, M. L.; Fléchard, X.; Gearba, M. A.; Nguyen, H.; Brédy, R.; Lundeen, S. R.; Depaola, B. D.

    2005-08-01

    Relative charge transfer cross section measurements for the excited state Rb(4d) with 7keV Na+ is reported. The specific channels reported are Na++Rb(4d5/2)→Na(nl)+Rb+ , where the dominant transfer cross sections channels were nl=3d and 4s . Using a combination of a magneto-optical trap and recoil ion momentum spectroscopy (MOTRIMS methodology), the cross sections were measured relative to the previously studied Na++Rb(5s,5p) systems at the same collision energy.

  16. Relative charge transfer cross section from Rb(4d)

    SciTech Connect

    Shah, M.H.; Camp, H.A.; Trachy, M.L.; De Paola, B.D.; Flechard, X.; Gearba, M.A.; Nguyen, H.; Bredy, R.; Lundeen, S.R.

    2005-08-15

    Relative charge transfer cross section measurements for the excited state Rb(4d) with 7 keV Na{sup +} is reported. The specific channels reported are Na{sup +}+Rb(4d{sub 5/2}){yields}Na(nl)+Rb{sup +}, where the dominant transfer cross sections channels were nl=3d and 4s. Using a combination of a magneto-optical trap and recoil ion momentum spectroscopy (MOTRIMS methodology), the cross sections were measured relative to the previously studied Na{sup +}+Rb(5s,5p) systems at the same collision energy.

  17. The 4-D approach to visual control of autonomous systems

    NASA Technical Reports Server (NTRS)

    Dickmanns, Ernst D.

    1994-01-01

    Development of a 4-D approach to dynamic machine vision is described. Core elements of this method are spatio-temporal models oriented towards objects and laws of perspective projection in a foward mode. Integration of multi-sensory measurement data was achieved through spatio-temporal models as invariants for object recognition. Situation assessment and long term predictions were allowed through maintenance of a symbolic 4-D image of processes involving objects. Behavioral capabilities were easily realized by state feedback and feed-foward control.

  18. Helical 4D CT and Comparison with Cine 4D CT

    NASA Astrophysics Data System (ADS)

    Pan, Tinsu

    4D CT was one of the most important developments in radiation oncology in the last decade. Its early development in single slice CT and commercialization in multi-slice CT has radically changed our practice in radiation treatment of lung cancer, and has enabled the stereotactic radiosurgery of early stage lung cancer. In this chapter, we will document the history of 4D CT development, detail the data sufficiency condition governing the 4D CT data collection; present the design of the commercial helical 4D CTs from Philips and Siemens; compare the differences between the helical 4D CT and the GE cine 4D CT in data acquisition, slice thickness, acquisition time and work flow; review the respiratory monitoring devices; and understand the causes of image artifacts in 4D CT.

  19. Biomedical applications of laser photoionization

    NASA Astrophysics Data System (ADS)

    Xiong, Xiaoxiong; Moore, Larry J.; Fassett, John R.; O'Haver, Thomas C.

    1991-07-01

    Trace elements are important for many essential metabolic functions. Zinc is a structural/functional component in more than 200 enzymes active in the biochemistry of cell division and tissue growth, neurology and endocrine control. Calcium is involved in intracellular control mechanisms and in skeletal bone building and resorption processes related to osteoporosis. Sensitive and selective laser photoionization is being developed to understand mechanisms in smaller samples and biological units approaching the cellular domain. Zinc has an ionization potential of 9.4 eV, or 75766.8 cm-1. Several processes are being explored, including two-photon resonant, three- photon ionization utilizing sequential UV transitions, e.g., 4s2 1S0 yields 4s4p 3P1 and 4s4p 3P1 yields 4s5d 3D1. Preliminary zinc stable isotope ratio data obtained by thermal atomization and laser photoionization agree with accepted values within 2 to 5%, except for anomalous 67Zn. Photoionization of calcium is being studied for isotope enrichment and ratio measurement using narrow and medium bandwidth lasers. Several ionization pathways, e.g., 4s2 1S0 - 2hv1 yields 4s10s - hv2 yields Ca+ (4s2S), are being investigated for isotopically selective ionization. Auto-ionization pathways are explored for greater efficiency in isotopic analysis. All studies have utilized a Nd:YAG- pumped laser system with one or two frequency-doubled tunable dye lasers coupled either to a magnetic sector or time-of-flight mass spectrometer.

  20. Work toward experimental evidence of hard x-ray photoionization in highly charged krypton.

    SciTech Connect

    Silver, E.; Gillaspy, J.D.; Gokhale, P.; Kanter, E.P.; Brickhouse, N.S.; Dunford, R.W.; Kirby, K.; Lin, T.; McDonald, J.; Schneider, D.; Seifert, S.; Young, L.

    2011-06-01

    Ions of almost any charge state can be produced through electron-impact ionization. Here we describe our first experiments designed to photoionize these highly charged ions with hard x-rays by pairing an electron and photon beam. A spectral line at 12.7(1) keV with an intensity corroborated by theory may be the first evidence of hard x-ray photoionization of a highly charged ion.

  1. Work Towards Experimental Evidence Of Hard X-Ray Photoionization In Highly Charged Krypton

    SciTech Connect

    Silver, E.; Brickhouse, N. S.; Kirby, K.; Lin, T.; Gillaspy, J. D.; Gokhale, P.; Kanter, E. P.; Dunford, R. W.; Seifert, S.; Young, L.; McDonald, J.; Schneider, D.

    2011-06-01

    Ions of almost any charge state can be produced through electron-impact ionization. Here we describe our first experiments designed to photoionize these highly charged ions with hard x-rays by pairing an electron and photon beam. A spectral line at 12.7(1) keV with an intensity corroborated by theory may be the first evidence of hard x-ray photoionization of a highly charged ion.

  2. 4D flow imaging with MRI

    PubMed Central

    Stankovic, Zoran; Allen, Bradley D.; Garcia, Julio; Jarvis, Kelly B.

    2014-01-01

    Magnetic resonance imaging (MRI) has become an important tool for the clinical evaluation of patients with cardiovascular disease. Since its introduction in the late 1980s, 2-dimensional phase contrast MRI (2D PC-MRI) has become a routine part of standard-of-care cardiac MRI for the assessment of regional blood flow in the heart and great vessels. More recently, time-resolved PC-MRI with velocity encoding along all three flow directions and three-dimensional (3D) anatomic coverage (also termed ‘4D flow MRI’) has been developed and applied for the evaluation of cardiovascular hemodynamics in multiple regions of the human body. 4D flow MRI allows for the comprehensive evaluation of complex blood flow patterns by 3D blood flow visualization and flexible retrospective quantification of flow parameters. Recent technical developments, including the utilization of advanced parallel imaging techniques such as k-t GRAPPA, have resulted in reasonable overall scan times, e.g., 8-12 minutes for 4D flow MRI of the aorta and 10-20 minutes for whole heart coverage. As a result, the application of 4D flow MRI in a clinical setting has become more feasible, as documented by an increased number of recent reports on the utility of the technique for the assessment of cardiac and vascular hemodynamics in patient studies. A number of studies have demonstrated the potential of 4D flow MRI to provide an improved assessment of hemodynamics which might aid in the diagnosis and therapeutic management of cardiovascular diseases. The purpose of this review is to describe the methods used for 4D flow MRI acquisition, post-processing and data analysis. In addition, the article provides an overview of the clinical applications of 4D flow MRI and includes a review of applications in the heart, thoracic aorta and hepatic system. PMID:24834414

  3. Phosphodiesterase4D (PDE4D)--A risk factor for atrial fibrillation and stroke?

    PubMed

    Jørgensen, Carina; Yasmeen, Saiqa; Iversen, Helle K; Kruuse, Christina

    2015-12-15

    Mutations in the gene encoding phosphodiesterase 4D (PDE4D) enzyme are associated with ischemic stroke; however the functional implications of such mutations are not well understood. PDE4D is part of a complex protein family modulating intracellular signalling by cyclic nucleotides. The PDE4 family includes subtypes A-D, all of which show unique intracellular, cellular and tissue distribution. PDE4D is the major subtype expressed in human atrial myocytes and involved in the pathophysiology of arrhythmias, such as atrial fibrillation. The PDE4D enzyme hydrolyses cyclic adenosine monophosphate (cAMP). Though diverging results are reported, several population based studies describe association of various PDE4D single nucleotide polymorphisms (SNP) with cardio-embolic stroke in particular. Functionally, a down regulation of PDE4D variants has been reported in stroke patients. The anti-inflammatory and vasodilator properties of PDE4 inhibitors make them suitable for treatment of stroke and cardiovascular disease. PDE4D has recently been suggested as factor in atrial fibrillation. This review summarizes the possible function of PDE4D in the brain, heart, and vasculature. Further, association of the described SNPs, in particular, with cardioembolic stroke, is reviewed. Current findings on the PDE4D mutations suggest functionality involves an increased cardiac risk factor as well as augmented risk of atrial fibrillation. PMID:26671126

  4. Communication: The influence of vibrational parity in chiral photoionization dynamics

    SciTech Connect

    Powis, Ivan

    2014-03-21

    A pronounced vibrational state dependence of photoelectron angular distributions observed in chiral photoionization experiments is explored using a simple, yet realistic, theoretical model based upon the transiently chiral molecule H{sub 2}O{sub 2}. The adiabatic approximation is used to separate vibrational and electronic wavefunctions. The full ionization matrix elements are obtained as an average of the electronic dipole matrix elements over the vibrational coordinate, weighted by the product of neutral and ion state vibrational wavefunctions. It is found that the parity of the vibrational Hermite polynomials influences not just the amplitude, but also the phase of the transition matrix elements, and the latter is sufficient, even in the absence of resonant enhancements, to account for enhanced vibrational dependencies in the chiral photoionization dynamics.

  5. Effect of core polarizability on photoionization cross-section calculations.

    NASA Technical Reports Server (NTRS)

    Kirkpatrick, R. C.

    1972-01-01

    Demonstration of the importance of core polarizability in a case where cancellation is only moderate, with suggestion of an improvement to the scaled Thomas-Fermi (STF) wave functions of Stewart and Rotenberg (1965). The inclusion of dipole polarizability of the core for argon is shown to substantially improve the agreement between the theoretical and experimental photoionization cross sections for the ground-state configuration.

  6. Shadow-driven 4D haptic visualization.

    PubMed

    Zhang, Hui; Hanson, Andrew

    2007-01-01

    Just as we can work with two-dimensional floor plans to communicate 3D architectural design, we can exploit reduced-dimension shadows to manipulate the higher-dimensional objects generating the shadows. In particular, by taking advantage of physically reactive 3D shadow-space controllers, we can transform the task of interacting with 4D objects to a new level of physical reality. We begin with a teaching tool that uses 2D knot diagrams to manipulate the geometry of 3D mathematical knots via their projections; our unique 2D haptic interface allows the user to become familiar with sketching, editing, exploration, and manipulation of 3D knots rendered as projected imageson a 2D shadow space. By combining graphics and collision-sensing haptics, we can enhance the 2D shadow-driven editing protocol to successfully leverage 2D pen-and-paper or blackboard skills. Building on the reduced-dimension 2D editing tool for manipulating 3D shapes, we develop the natural analogy to produce a reduced-dimension 3D tool for manipulating 4D shapes. By physically modeling the correct properties of 4D surfaces, their bending forces, and their collisions in the 3D haptic controller interface, we can support full-featured physical exploration of 4D mathematical objects in a manner that is otherwise far beyond the experience accessible to human beings. As far as we are aware, this paper reports the first interactive system with force-feedback that provides "4D haptic visualization" permitting the user to model and interact with 4D cloth-like objects.

  7. 4D Confocal Imaging of Yeast Organelles.

    PubMed

    Day, Kasey J; Papanikou, Effrosyni; Glick, Benjamin S

    2016-01-01

    Yeast cells are well suited to visualizing organelles by 4D confocal microscopy. Typically, one or more cellular compartments are labeled with a fluorescent protein or dye, and a stack of confocal sections spanning the entire cell volume is captured every few seconds. Under appropriate conditions, organelle dynamics can be observed for many minutes with only limited photobleaching. Images are captured at a relatively low signal-to-noise ratio and are subsequently processed to generate movies that can be analyzed and quantified. Here, we describe methods for acquiring and processing 4D data using conventional scanning confocal microscopy. PMID:27631997

  8. The scientific value of 4D visualizations

    NASA Astrophysics Data System (ADS)

    Minster, J.; Olsen, K.; Day, S.; Moore, R.; Jordan, T. H.; Maechling, P.; Chourasia, A.

    2006-12-01

    Significant scientific insights derive from viewing measured, or calculated three-dimensional, time-dependent -- that is four-dimensional-- fields. This issue cuts across all disciplines of Earth Sciences. Addressing it calls for close collaborations between "domain" scientists and "IT" visualization specialists. Techniques to display such 4D fields in a intuitive way are a major challenge, especially when the relevant variables to be displayed are not scalars but tensors. This talk will illustrate some attempts to deal with this challenge, using seismic wave fields as specific objects to display. We will highlight how 4D displays can help address very difficult issues of significant scientific import.

  9. Absolute Photoionization Cross Section with an Ultra-high Energy Resolution for Ne in the Region of 1s Rydberg States

    SciTech Connect

    Kato, M.; Morishita, Y.; Suzuki, I. H.; Saito, N.; Oura, M.; Yamaoka, H.; Okada, K.; Matsudo, T.; Gejo, T.

    2007-01-19

    The high-resolution absolute photoabsorption cross section with an absolute photon energy scale for Ne in the energy region of 864-872 eV (1s-1np Rydberg states) has been measured using a multi-electrode ionization chamber and monochromatized synchrotron radiation. The natural lifetime width of Ne 1s-13p resonance state has been obtained to be 252 {+-} 5 meV. The Ne+ (1s-1) ionization potential is determined to be 870.16 {+-} 0.04 eV by using the Rydberg formula. These absolute values are supposed to be more reliable than those previously reported.

  10. Coherent control of photoionization of atomic barium

    NASA Astrophysics Data System (ADS)

    Yamazaki, Rekishu

    We present the results of our study on coherent control of photoionization of atomic barium. Our study focused on the understanding of the controllability, especially due to the effect of the coherent interaction between the atomic system and the laser field. The first half of the study investigates the mechanisms of the control behind the previously observed laser phase-insensitive product state control. The controllability of this excitation scheme, two-color two-photon resonantly enhanced excitation, was analyzed from two aspects, the role of ac Stark shift introduced by the strong laser field and the multi-pathway quantum mechanical interferences. We have analyzed the excitation scheme from the analysis of the photoelectron angular distribution measured using the excitation scheme and the monitoring of the intermediate state population. Analysis of the data as well as the numerical simulation showed clear understanding of the role of two mechanisms in the product state control reported. We also investigated the control of the phase lag during the product state control. We conducted the control of the phase lag in the study of asymmetric photoelectron angular distribution, which arises from the concurrent even-odd parity outgoing electron wave excitation. The phase lag was controlled in full range, 2pi, and the results were analyzed in terms of the role of autoionizing resonance structures as well as the nature of outgoing electron waves at different locations of the autoionizing resonances.

  11. Maximizing hole coherence in ultrafast photoionization of argon with an optimization by sequential parametrization update

    NASA Astrophysics Data System (ADS)

    Goetz, R. Esteban; Merkel, Maximilian; Karamatskou, Antonia; Santra, Robin; Koch, Christiane P.

    2016-08-01

    Photoionization with attosecond pulses populates hole states in the photoion. Superpositions of hole states represent ideal candidates for time-dependent spectroscopy, for example via pump-probe studies. The challenge consists in identifying pulses that create coherent superpositions of hole states while satisfying practical constraints. Here, we employ quantum optimal control to maximize the degree of coherence between these hole states. To this end, we introduce a derivative-free optimization method with sequential parametrization update (SPA optimization). We demonstrate the versatility and computational efficiency of SPA optimization for photoionization in argon by maximizing the coherence between the 3 s and 3 p0 hole states using shaped attosecond pulses. We show that it is possible to maximize the hole coherence while simultaneously prescribing the ratio of the final hole state populations.

  12. Constrained reconstructions for 4D intervention guidance.

    PubMed

    Kuntz, J; Flach, B; Kueres, R; Semmler, W; Kachelriess, M; Bartling, S

    2013-05-21

    Image-guided interventions are an increasingly important part of clinical minimally invasive procedures. However, up to now they cannot be performed under 4D (3D + time) guidance due to the exceedingly high x-ray dose. In this work we investigate the applicability of compressed sensing reconstructions for highly undersampled CT datasets combined with the incorporation of prior images in order to yield low dose 4D intervention guidance. We present a new reconstruction scheme prior image dynamic interventional CT (PrIDICT) that accounts for specific image features in intervention guidance and compare it to PICCS and ASD-POCS. The optimal parameters for the dose per projection and the numbers of projections per reconstruction are determined in phantom simulations and measurements. In vivo experiments in six pigs are performed in a cone-beam CT; measured doses are compared to current gold-standard intervention guidance represented by a clinical fluoroscopy system. Phantom studies show maximum image quality for identical overall doses in the range of 14 to 21 projections per reconstruction. In vivo studies reveal that interventional materials can be followed in 4D visualization and that PrIDICT, compared to PICCS and ASD-POCS, shows superior reconstruction results and fewer artifacts in the periphery with dose in the order of biplane fluoroscopy. These results suggest that 4D intervention guidance can be realized with today's flat detector and gantry systems using the herein presented reconstruction scheme.

  13. 4D-Var Developement at GMAO

    NASA Technical Reports Server (NTRS)

    Pelc, Joanna S.; Todling, Ricardo; Akkraoui, Amal El

    2014-01-01

    The Global Modeling and Assimilation Offce (GMAO) is currently using an IAU-based 3D-Var data assimilation system. GMAO has been experimenting with a 3D-Var-hybrid version of its data assimilation system (DAS) for over a year now, which will soon become operational and it will rapidly progress toward a 4D-EnVar. Concurrently, the machinery to exercise traditional 4DVar is in place and it is desirable to have a comparison of the traditional 4D approach with the other available options, and evaluate their performance in the Goddard Earth Observing System (GEOS) DAS. This work will also explore the possibility for constructing a reduced order model (ROM) to make traditional 4D-Var computationally attractive for increasing model resolutions. Part of the research on ROM will be to search for a suitably acceptable space to carry on the corresponding reduction. This poster illustrates how the IAU-based 4D-Var assimilation compares with our currently used IAU-based 3D-Var.

  14. Constrained reconstructions for 4D intervention guidance

    NASA Astrophysics Data System (ADS)

    Kuntz, J.; Flach, B.; Kueres, R.; Semmler, W.; Kachelrieß, M.; Bartling, S.

    2013-05-01

    Image-guided interventions are an increasingly important part of clinical minimally invasive procedures. However, up to now they cannot be performed under 4D (3D + time) guidance due to the exceedingly high x-ray dose. In this work we investigate the applicability of compressed sensing reconstructions for highly undersampled CT datasets combined with the incorporation of prior images in order to yield low dose 4D intervention guidance. We present a new reconstruction scheme prior image dynamic interventional CT (PrIDICT) that accounts for specific image features in intervention guidance and compare it to PICCS and ASD-POCS. The optimal parameters for the dose per projection and the numbers of projections per reconstruction are determined in phantom simulations and measurements. In vivo experiments in six pigs are performed in a cone-beam CT; measured doses are compared to current gold-standard intervention guidance represented by a clinical fluoroscopy system. Phantom studies show maximum image quality for identical overall doses in the range of 14 to 21 projections per reconstruction. In vivo studies reveal that interventional materials can be followed in 4D visualization and that PrIDICT, compared to PICCS and ASD-POCS, shows superior reconstruction results and fewer artifacts in the periphery with dose in the order of biplane fluoroscopy. These results suggest that 4D intervention guidance can be realized with today’s flat detector and gantry systems using the herein presented reconstruction scheme.

  15. Photoion Auger-electron coincidence measurements near threshold

    SciTech Connect

    Levin, J.C.; Biedermann, C.; Keller, N.; Liljeby, L.; Short, R.T.; Sellin, I.A. . Dept. of Physics Oak Ridge National Lab., TN ); Lindle, D.W. , Gaithersburg, MD )

    1990-01-01

    The vacancy cascade which fills an atomic inner-shell hole is a complex process which can proceed by a variety of paths, often resulting in a broad distribution of photoion charge states. We have measured simplified argon photoion charge distributions by requiring a coincidence with a K-LL or K-LM Auger electron, following K excitation with synchrotron radiation, as a function of photon energy, and report here in detail the argon charge distributions coincident with K-L{sub 1}L{sub 23} Auger electrons. The distributions exhibit a much more pronounced photon-energy dependence than do the more complicated non-coincident spectra. Resonant excitation of the K electron to np levels, shakeoff of these np electrons by subsequent decay processes, double-Auger decay, and recapture of the K photoelectron through postcollision interaction occur with significant probability. 17 refs.

  16. 2006 Photoions, Photoionization & Photodetachment held on January 29-February 3, 2006

    SciTech Connect

    Robert Continetti Nancy Ryan Gray

    2006-09-06

    The 4th Gordon Conference on Photoions, Photoionization and Photodetachment will be held January 29-February 3, 2006 at the Santa Ynez Valley Marriott in Buellton, California. This meeting will continue to cover fundamentals and applications of photoionization and photodetachment, including valence and core-level phenomena and applications to reaction dynamics, ultrashort laser pulses and the study of exotic molecules and anions. Further information will be available soon at the Gordon Conference Website, and will be announced.

  17. Photoionization of endohedral fullerenes using soft x-ray coincidence spectroscopy

    NASA Astrophysics Data System (ADS)

    Obaid, Razib; Xiong, Hui; Ablikim, Utuq; Augustin, Sven; Schnorr, Kirsten; Battistoni, Andrea; Wolf, Thomas; Carroll, Ann Marie; Bilodeau, Rene; Osipov, Timur; Rolles, Daniel; Berrah, Nora

    2016-05-01

    Endohedral fullerenes are a model system to understand the reorganization dynamics of highly charged molecular systems with delocalized electronic clouds in the multiphoton excitation regime. Previous experiments at the Linac Coherent Light Source (LCLS) using free-electron laser (FEL) and ultrafast IR laser pulses studied this feature in Ho3N@C80. The question remains whether these dynamics can be studied in the site-specific single photo-ionization regime. Ho3N@C80 is particularly interesting since the inner molecule, Ho3N, is unstable in its natural form. The presence of the encapsulating cage, with the charge exchange characteristics of Holmium, stabilizes the whole molecule. In this study, we will present the charge fragmentation dynamics of this species in the single photoionization process of inner shell electrons (4d) of Holmium using the Advanced Light Source (ALS) at LBNL. Photoion-photoion correlation data, alongside with qualitative electron data will be presented. Funded by the DoE-BES, Grant No. DE-SC0012376.

  18. Double K-shell photoionization of atomic beryllium

    SciTech Connect

    Yip, F. L.; Martin, F.; McCurdy, C. W.; Rescigno, T. N.

    2011-11-15

    Double photoionization of the core 1s electrons in atomic beryllium is theoretically studied using a hybrid approach that combines orbital and grid-based representations of the Hamiltonian. The {sup 1} S ground state and {sup 1} P final state contain a double occupancy of the 2s valence shell in all configurations used to represent the correlated wave function. Triply differential cross sections are evaluated, with particular attention focused on a comparison of the effects of scattering the ejected electrons through the spherically symmetric valence shell with similar cross sections for helium, representing a purely two-electron target with an analogous initial-state configuration.

  19. Ultraviolet photoionization in CO2 TEA lasers

    NASA Astrophysics Data System (ADS)

    Scott, S. J.; Smith, A. L. S.

    1988-07-01

    The effects of gas composition and spark parameters on the UV emission in CO2 TEA laser gas mixtures were investigated together with the nature of photoionization process and the photoelectron-loss mechanism. A linear relationship was found between N2 concentration and photoionization (with no such dependence on C concentration, from CO and CO2), but the increases in photoionization that could be effected by optimizing the spark discharge circuit parameters were much higher than those produced by changes in gas composition. UV emission was directly proportional to the amount of stored electrical energy in the spark-discharge circuit and to the cube of the peak current produced in the spark by the discharge of this energy. Photoionization was also found to be proportional to the spark electrode gap. It was found that free-space sparks gave a considerably broader emission pattern than a surface-guided notched spark.

  20. Interactive animation of 4D performance capture.

    PubMed

    Casas, Dan; Tejera, Margara; Guillemaut, Jean-Yves; Hilton, Adrian

    2013-05-01

    A 4D parametric motion graph representation is presented for interactive animation from actor performance capture in a multiple camera studio. The representation is based on a 4D model database of temporally aligned mesh sequence reconstructions for multiple motions. High-level movement controls such as speed and direction are achieved by blending multiple mesh sequences of related motions. A real-time mesh sequence blending approach is introduced, which combines the realistic deformation of previous nonlinear solutions with efficient online computation. Transitions between different parametric motion spaces are evaluated in real time based on surface shape and motion similarity. Four-dimensional parametric motion graphs allow real-time interactive character animation while preserving the natural dynamics of the captured performance.

  1. Interactive animation of 4D performance capture.

    PubMed

    Casas, Dan; Tejera, Margara; Guillemaut, Jean-Yves; Hilton, Adrian

    2013-05-01

    A 4D parametric motion graph representation is presented for interactive animation from actor performance capture in a multiple camera studio. The representation is based on a 4D model database of temporally aligned mesh sequence reconstructions for multiple motions. High-level movement controls such as speed and direction are achieved by blending multiple mesh sequences of related motions. A real-time mesh sequence blending approach is introduced, which combines the realistic deformation of previous nonlinear solutions with efficient online computation. Transitions between different parametric motion spaces are evaluated in real time based on surface shape and motion similarity. Four-dimensional parametric motion graphs allow real-time interactive character animation while preserving the natural dynamics of the captured performance. PMID:23492379

  2. Influence of shape resonances on minima in cross sections for photoionization of excited atoms

    SciTech Connect

    Felfli, Z.; Manson, S.T. Department of Astronomy, Georgia State University, Atlanta, Georgia 30303 )

    1990-02-01

    A relationship between the location of Cooper minima and the difference between the quantum defect of the initial state and the threshold phase shift (in units of {pi}) of the final state in excited photoionization has been suggested earlier (Phys. Rev. Lett. 48, 473 (1982)). The existence of a shape resonance in the final state is shown to modify this relationship.

  3. Photoelectron wave function in photoionization: plane wave or Coulomb wave?

    PubMed

    Gozem, Samer; Gunina, Anastasia O; Ichino, Takatoshi; Osborn, David L; Stanton, John F; Krylov, Anna I

    2015-11-19

    The calculation of absolute total cross sections requires accurate wave functions of the photoelectron and of the initial and final states of the system. The essential information contained in the latter two can be condensed into a Dyson orbital. We employ correlated Dyson orbitals and test approximate treatments of the photoelectron wave function, that is, plane and Coulomb waves, by comparing computed and experimental photoionization and photodetachment spectra. We find that in anions, a plane wave treatment of the photoelectron provides a good description of photodetachment spectra. For photoionization of neutral atoms or molecules with one heavy atom, the photoelectron wave function must be treated as a Coulomb wave to account for the interaction of the photoelectron with the +1 charge of the ionized core. For larger molecules, the best agreement with experiment is often achieved by using a Coulomb wave with a partial (effective) charge smaller than unity. This likely derives from the fact that the effective charge at the centroid of the Dyson orbital, which serves as the origin of the spherical wave expansion, is smaller than the total charge of a polyatomic cation. The results suggest that accurate molecular photoionization cross sections can be computed with a modified central potential model that accounts for the nonspherical charge distribution of the core by adjusting the charge in the center of the expansion.

  4. Photoelectron wave function in photoionization: plane wave or Coulomb wave?

    PubMed

    Gozem, Samer; Gunina, Anastasia O; Ichino, Takatoshi; Osborn, David L; Stanton, John F; Krylov, Anna I

    2015-11-19

    The calculation of absolute total cross sections requires accurate wave functions of the photoelectron and of the initial and final states of the system. The essential information contained in the latter two can be condensed into a Dyson orbital. We employ correlated Dyson orbitals and test approximate treatments of the photoelectron wave function, that is, plane and Coulomb waves, by comparing computed and experimental photoionization and photodetachment spectra. We find that in anions, a plane wave treatment of the photoelectron provides a good description of photodetachment spectra. For photoionization of neutral atoms or molecules with one heavy atom, the photoelectron wave function must be treated as a Coulomb wave to account for the interaction of the photoelectron with the +1 charge of the ionized core. For larger molecules, the best agreement with experiment is often achieved by using a Coulomb wave with a partial (effective) charge smaller than unity. This likely derives from the fact that the effective charge at the centroid of the Dyson orbital, which serves as the origin of the spherical wave expansion, is smaller than the total charge of a polyatomic cation. The results suggest that accurate molecular photoionization cross sections can be computed with a modified central potential model that accounts for the nonspherical charge distribution of the core by adjusting the charge in the center of the expansion. PMID:26509428

  5. Abdominal and pancreatic motion correlation using 4D CT, 4D transponders, and a gating belt.

    PubMed

    Betancourt, Ricardo; Zou, Wei; Plastaras, John P; Metz, James M; Teo, Boon-Keng; Kassaee, Alireza

    2013-01-01

    The correlation between the pancreatic and external abdominal motion due to respiration was investigated on two patients. These studies utilized four dimensional computer tomography (4D CT), a four dimensional (4D) electromagnetic transponder system, and a gating belt system. One 4D CT study was performed during simulation to quantify the pancreatic motion using computer tomography images at eight breathing phases. The motion under free breathing and breath-hold were analyzed for the 4D electromagnetic transponder system and the gating belt system during treatment. A linear curve was fitted for all data sets and correlation factors were evaluated between the 4D electromagnetic transponder system and the gating belt system data. The 4D CT study demonstrated a modest correlation between the external marker and the pancreatic motion with R-square values larger than 0.8 for the inferior-superior (inf-sup). Then, the relative pressure from the belt gating system correlated well with the 4D electromagnetic transponder system's motion in the anterior-posterior (ant-post) and the inf-post directions. These directions have a correlation value of -0.93 and 0.76, while the lateral only had a 0.03 correlation coefficient. Based on our limited study, external surrogates can be used as predictors of the pancreatic motion in the inf-sup and the ant-post directions. Although there is a low correlation on the lateral direction, its motion is significantly shorter. In conclusion, an appropriate treatment delivery can be used for pancreatic cancer when an internal tracking system, such as the 4D electromagnetic transponder system, is unavailable. PMID:23652242

  6. Abdominal and pancreatic motion correlation using 4D CT, 4D transponders, and a gating belt.

    PubMed

    Betancourt, Ricardo; Zou, Wei; Plastaras, John P; Metz, James M; Teo, Boon-Keng; Kassaee, Alireza

    2013-05-06

    The correlation between the pancreatic and external abdominal motion due to respiration was investigated on two patients. These studies utilized four dimensional computer tomography (4D CT), a four dimensional (4D) electromagnetic transponder system, and a gating belt system. One 4D CT study was performed during simulation to quantify the pancreatic motion using computer tomography images at eight breathing phases. The motion under free breathing and breath-hold were analyzed for the 4D electromagnetic transponder system and the gating belt system during treatment. A linear curve was fitted for all data sets and correlation factors were evaluated between the 4D electromagnetic transponder system and the gating belt system data. The 4D CT study demonstrated a modest correlation between the external marker and the pancreatic motion with R-square values larger than 0.8 for the inferior-superior (inf-sup). Then, the relative pressure from the belt gating system correlated well with the 4D electromagnetic transponder system's motion in the anterior-posterior (ant-post) and the inf-post directions. These directions have a correlation value of -0.93 and 0.76, while the lateral only had a 0.03 correlation coefficient. Based on our limited study, external surrogates can be used as predictors of the pancreatic motion in the inf-sup and the ant-post directions. Although there is a low correlation on the lateral direction, its motion is significantly shorter. In conclusion, an appropriate treatment delivery can be used for pancreatic cancer when an internal tracking system, such as the 4D electromagnetic transponder system, is unavailable.

  7. Dirac R-matrix calculations of photoionization cross-sections of Ni XIII

    NASA Astrophysics Data System (ADS)

    Sardar, S.; Bilal, M.; Bari, M. A.; Nazir, R. T.; Hannan, A.; Salahuddin, M.; Nasim, M. H.

    2016-05-01

    In this paper, we report total photoionization cross-sections of Ni XIII in the ground state (3P2) and four excited states (3P1,0, 1D2, 1S0) for the first time over the photon energy range 380-480 eV. The target wavefunctions are constructed with fully relativistic atomic structure GRASP code. Our calculated energy levels and oscillator strengths of core ion Ni XIV agree well with available experimental and theoretical results. The ionization threshold value of ground state of Ni XIII is found to be more closer to the experimental ionization energy and improved over the previous calculations. The photoionization cross-sections are calculated using the fully relativistic DARC code with an appropriate energy step of 0.01 eV to delineate the resonance structures. The calculated ionization cross-sections are important for the modelling of features of photoionized plasmas and for stellar opacities.

  8. 2001 Gordon Research Conference on Photoions, Photoionization and Photodetachment. Final progress report [agenda and attendees list

    SciTech Connect

    Johnson, Mark

    2001-07-13

    The Gordon Research Conference on Photoions, Photoionization and Photodetachment was held at Williams College, Williamstown, Massachusetts, July 8-13, 2001. The 72 conference attendees represented the spectrum of endeavor in this field, coming from academia, industry, and government laboratories, and including US and foreign scientists, senior researchers, young investigators, and students. Emphasis was placed on current unpublished research and discussion of the future target areas in this field. There was a conscious effort to stimulate discussion about the key issues in the field today. Time for formal presentations was limited. Sessions included the following topics: Vibrational structure, Time resolved studies: nuclear wavepackets, Valence photoionization, Clusters and networks, Resonance structures and decay mechanisms, Ultrafast photoionization, Threshold photoionization, Molecule fixed properties, and Collisional phenomena.

  9. Active origami by 4D printing

    NASA Astrophysics Data System (ADS)

    Ge, Qi; Dunn, Conner K.; Qi, H. Jerry; Dunn, Martin L.

    2014-09-01

    Recent advances in three dimensional (3D) printing technology that allow multiple materials to be printed within each layer enable the creation of materials and components with precisely controlled heterogeneous microstructures. In addition, active materials, such as shape memory polymers, can be printed to create an active microstructure within a solid. These active materials can subsequently be activated in a controlled manner to change the shape or configuration of the solid in response to an environmental stimulus. This has been termed 4D printing, with the 4th dimension being the time-dependent shape change after the printing. In this paper, we advance the 4D printing concept to the design and fabrication of active origami, where a flat sheet automatically folds into a complicated 3D component. Here we print active composites with shape memory polymer fibers precisely printed in an elastomeric matrix and use them as intelligent active hinges to enable origami folding patterns. We develop a theoretical model to provide guidance in selecting design parameters such as fiber dimensions, hinge length, and programming strains and temperature. Using the model, we design and fabricate several active origami components that assemble from flat polymer sheets, including a box, a pyramid, and two origami airplanes. In addition, we directly print a 3D box with active composite hinges and program it to assume a temporary flat shape that subsequently recovers to the 3D box shape on demand.

  10. Relativistic effects in the photoionization of hydrogen-like ions with screened Coulomb interaction

    SciTech Connect

    Xie, L. Y.; Wang, J. G.; Janev, R. K.

    2014-06-15

    The relativistic effects in the photoionization of hydrogen-like ion with screened Coulomb interaction of Yukawa type are studied for a broad range of screening lengths and photoelectron energies. The bound and continuum wave functions have been determined by solving the Dirac equation. The study is focused on the relativistic effects manifested in the characteristic features of photoionization cross section for electric dipole nl→ε,l±1 transitions: shape resonances, Cooper minima and cross section enhancements due to near-zero-energy states. It is shown that the main source of relativistic effects in these cross section features is the fine-structure splitting of bound state energy levels. The relativistic effects are studied in the photoionization of Fe{sup 25+} ion, as an example.

  11. EUV optics in photoionization experiments

    NASA Astrophysics Data System (ADS)

    Bartnik, Andrzej; Wachulak, Przemysław; Fiedorowicz, Henryk; Fok, Tomasz; Jarocki, Roman; Kostecki, Jerzy; Szczurek, Anna; Szczurek, Mirosław; Pina, Ladislav; Sveda, Libor

    2013-05-01

    In this work photoionized plasmas were created by irradiation of He, Ne and Ar gases with a focused EUV beam from one of two laser-plasma sources employing Nd:YAG laser systems of different parameters. First of them was a 10-Hz laser-plasma EUV source, based on a double-stream gas-puff target, irradiated with the 3-ns/0.8J laser pulse. EUV radiation in this case was focused using a gold-plated grazing incidence ellipsoidal collector in the wavelength range λ = 9÷70 nm. The most intense emission was in the relatively narrow spectral region centred at λ = 11 +/- 1 nm. The second source was based on a 10 ns/10 J/10 Hz laser system. In this case EUV radiation was focused using a gold-plated grazing incidence multifoil collector or a Mo-coated ellipsoidal collector. The most intense emission in this case was in the 5 ÷ 15 nm spectral region. Radiation fluence ranged from 60 mJ/cm2 to 400 mJ/cm2. Different gases were injected into the interaction region, perpendicularly to an optical axis of the irradiation system, using an auxiliary gas puff valve. Irradiation of the gases resulted in ionization and excitation of atoms and ions. Spectra in EUV range were measured using a grazing incidence, flat-field spectrometer (McPherson Model 251), equipped with a 450 lines/mm toroidal grating. In all cases the most intense emission lines were assigned to singly charged ions. The other emission lines belong to atoms or doubly charged ions. The spectra were excited in low density gases of the order of 1 ÷ 10% atmospheric density.

  12. A sinogram warping strategy for pre-reconstruction 4D PET optimization.

    PubMed

    Gianoli, Chiara; Riboldi, Marco; Fontana, Giulia; Kurz, Christopher; Parodi, Katia; Baroni, Guido

    2016-03-01

    A novel strategy for 4D PET optimization in the sinogram domain is proposed, aiming at motion model application before image reconstruction ("sinogram warping" strategy). Compared to state-of-the-art 4D-MLEM reconstruction, the proposed strategy is able to optimize the image SNR, avoiding iterative direct and inverse warping procedures, which are typical of the 4D-MLEM algorithm. A full-count statistics sinogram of the motion-compensated 4D PET reference phase is generated by warping the sinograms corresponding to the different PET phases. This is achieved relying on a motion model expressed in the sinogram domain. The strategy was tested on the anthropomorphic 4D PET-CT NCAT phantom in comparison with the 4D-MLEM algorithm, with particular reference to robustness to PET-CT co-registrations artefacts. The MLEM reconstruction of the warped sinogram according to the proposed strategy exhibited better accuracy (up to +40.90 % with respect to the ideal value), whereas images reconstructed according to the 4D-MLEM reconstruction resulted in less noisy (down to -26.90 % with respect to the ideal value) but more blurred. The sinogram warping strategy demonstrates advantages with respect to 4D-MLEM algorithm. These advantages are paid back by introducing approximation of the deformation field, and further efforts are required to mitigate the impact of such an approximation in clinical 4D PET reconstruction.

  13. ICT4D: A Computer Science Perspective

    NASA Astrophysics Data System (ADS)

    Sutinen, Erkki; Tedre, Matti

    The term ICT4D refers to the opportunities of Information and Communication Technology (ICT) as an agent of development. Research in that field is often focused on evaluating the feasibility of existing technologies, mostly of Western or Far East Asian origin, in the context of developing regions. A computer science perspective is complementary to that agenda. The computer science perspective focuses on exploring the resources, or inputs, of a particular context and on basing the design of a technical intervention on the available resources, so that the output makes a difference in the development context. The modus operandi of computer science, construction, interacts with evaluation and exploration practices. An analysis of a contextualized information technology curriculum of Tumaini University in southern Tanzania shows the potential of the computer science perspective for designing meaningful information and communication technology for a developing region.

  14. 4D Clinical Imaging for Dynamic CAD

    PubMed Central

    McIntyre, Frederick

    2013-01-01

    A basic 4D imaging system to capture the jaw motion has been developed that produces high resolution 3D surface data. Fluorescent microspheres are brushed onto the areas of the upper and the lower arches to be imaged, producing a high-contrast random optical pattern. A hand-held imaging device operated at about 10 cm from the mouth captures time-based perspective images of the fluorescent areas. Each set of images, containing both upper and the lower arch data, is converted to a 3d point mesh using photogrammetry, thereby providing an instantaneous relative jaw position. Eight 3d positions per second are captured. Using one of the 3d frames as a reference, incremental transforms are derived to express the free body motion of the mandible. Conventional 3d models of the dentition are directly registered to the reference frame, allowing them to be animated using the derived transforms. PMID:24082882

  15. Vacuum Ultraviolet Photoionization of Complex Chemical Systems

    NASA Astrophysics Data System (ADS)

    Kostko, Oleg; Bandyopadhyay, Biswajit; Ahmed, Musahid

    2016-05-01

    Tunable vacuum ultraviolet (VUV) radiation coupled to mass spectrometry is applied to the study of complex chemical systems. The identification of novel reactive intermediates and radicals is revealed in flame, pulsed photolysis, and pyrolysis reactors, leading to the elucidation of spectroscopy, reaction mechanisms, and kinetics. Mass-resolved threshold photoelectron photoion coincidence measurements provide unprecedented access to vibrationally resolved spectra of free radicals present in high-temperature reactors. Photoionization measurements in water clusters, nucleic acid base dimers, and their complexes with water provide signatures of proton transfer in hydrogen-bonded and π-stacked systems. Experimental and theoretical methods to track ion-molecule reactions and fragmentation pathways in intermolecular and intramolecular hydrogen-bonded systems in sugars and alcohols are described. Photoionization of laser-ablated molecules, clusters, and their reaction products inform thermodynamics and spectroscopy that are relevant to astrochemistry and catalysis. New directions in coupling VUV radiation to interrogate complex chemical systems are discussed.

  16. Vacuum Ultraviolet Photoionization of Complex Chemical Systems.

    PubMed

    Kostko, Oleg; Bandyopadhyay, Biswajit; Ahmed, Musahid

    2016-05-27

    Tunable vacuum ultraviolet (VUV) radiation coupled to mass spectrometry is applied to the study of complex chemical systems. The identification of novel reactive intermediates and radicals is revealed in flame, pulsed photolysis, and pyrolysis reactors, leading to the elucidation of spectroscopy, reaction mechanisms, and kinetics. Mass-resolved threshold photoelectron photoion coincidence measurements provide unprecedented access to vibrationally resolved spectra of free radicals present in high-temperature reactors. Photoionization measurements in water clusters, nucleic acid base dimers, and their complexes with water provide signatures of proton transfer in hydrogen-bonded and π-stacked systems. Experimental and theoretical methods to track ion-molecule reactions and fragmentation pathways in intermolecular and intramolecular hydrogen-bonded systems in sugars and alcohols are described. Photoionization of laser-ablated molecules, clusters, and their reaction products inform thermodynamics and spectroscopy that are relevant to astrochemistry and catalysis. New directions in coupling VUV radiation to interrogate complex chemical systems are discussed. PMID:26980311

  17. Vacuum Ultraviolet Photoionization of Complex Chemical Systems.

    PubMed

    Kostko, Oleg; Bandyopadhyay, Biswajit; Ahmed, Musahid

    2016-05-27

    Tunable vacuum ultraviolet (VUV) radiation coupled to mass spectrometry is applied to the study of complex chemical systems. The identification of novel reactive intermediates and radicals is revealed in flame, pulsed photolysis, and pyrolysis reactors, leading to the elucidation of spectroscopy, reaction mechanisms, and kinetics. Mass-resolved threshold photoelectron photoion coincidence measurements provide unprecedented access to vibrationally resolved spectra of free radicals present in high-temperature reactors. Photoionization measurements in water clusters, nucleic acid base dimers, and their complexes with water provide signatures of proton transfer in hydrogen-bonded and π-stacked systems. Experimental and theoretical methods to track ion-molecule reactions and fragmentation pathways in intermolecular and intramolecular hydrogen-bonded systems in sugars and alcohols are described. Photoionization of laser-ablated molecules, clusters, and their reaction products inform thermodynamics and spectroscopy that are relevant to astrochemistry and catalysis. New directions in coupling VUV radiation to interrogate complex chemical systems are discussed.

  18. Photoion mass spectroscopy and valence photoionization of hypoxanthine, xanthine and caffeine

    NASA Astrophysics Data System (ADS)

    Feyer, Vitaliy; Plekan, Oksana; Richter, Robert; Coreno, Marcello; Prince, Kevin C.

    2009-03-01

    Photoionization mass spectra of hypoxanthine, xanthine and caffeine were measured using the photoelectron-photoion coincidence technique and noble gas resonance radiation at energies from 8.4 to 21.2 eV for ionization. The fragmentation patterns for these compounds show that hydrogen cyanide is the main neutral loss species at higher photon energies, while photoionization below 16.67 eV led predominantly to the parent ion. The valence photoelectron spectra of this family of molecules were measured over an extended energy range, including the inner C, N and O 2s valence orbitals. The observed ion fragments were related to ionization of the valence orbitals.

  19. Confinement Resonances in Photoionization of Xe-C{sub 60}{sup +}

    SciTech Connect

    Kilcoyne, A. L. D.; Aguilar, A.; Mueller, A.; Schippers, S.; Cisneros, C.; Alna'Washi, G.; Aryal, N. B.; Baral, K. K.; Esteves, D. A.; Thomas, C. M.; Phaneuf, R. A.

    2010-11-19

    Experimental evidence is presented for confinement resonances associated with photoabsorption by a Xe atom in a C{sub 60} cage. The giant 4d resonance in photoionization of Xe is predicted to be redistributed into four components due to multipath interference of photoelectron waves reflected by the cage. The measurements were made in the photon energy range 60-150 eV by merging a beam of synchrotron radiation with a mass/charge selected Xe-C{sub 60}{sup +} ion beam. The phenomenon was observed in the Xe-C{sub 583}{sup +} product ion channel.

  20. Opening the Black Box of ICT4D: Advancing Our Understanding of ICT4D Partnerships

    ERIC Educational Resources Information Center

    Park, Sung Jin

    2013-01-01

    The term, Information and Communication Technologies for Development (ICT4D), pertains to programs or projects that strategically use ICTs (e.g. mobile phones, computers, and the internet) as a means toward the socio-economic betterment for the poor in developing contexts. Gaining the political and financial support of the international community…

  1. Experimental study of linear magnetic dichroism in photoionization satellite transitions of atomic rubidium

    SciTech Connect

    Jaenkaelae, K.; Alagia, M.; Feyer, V.; Richter, R.; Prince, K. C.

    2011-11-15

    Laser orientation in the initial state has been used to study the properties of satellite transitions in inner-shell photoionization of rubidium atoms. The linear magnetic dichroism in the angular distribution (LMDAD) has been utilized to probe the continuum waves of orbital angular momentum conserving monopole, and angular momentum changing conjugate satellites, accompanying the 4p ionization of atomic Rb. We show experimentally that LMDAD of both types of satellite transitions is nonzero and that LMDAD of monopole satellites, measured as a function of photon energy, mimics the LMDAD of direct photoionization, whereas the LMDAD of conjugate transitions deviates drastically from that trend. The results indicate that conjugate transitions cannot be described theoretically without explicit inclusion of electron-electron interaction. The present data can thus be used as a very precise test of current models for photoionization.

  2. Negative photoion spectroscopy of freon molecules in the vicinity of the Cl 2p edge

    SciTech Connect

    Scully, S.W.J.; Mackie, R.A.; Browning, R.; Dunn, K.F.; Latimer, C.J.

    2004-10-01

    Polar photodissociation of CF{sub n}Cl{sub 4-n} (n=0-2) has been studied using synchrotron radiation within the energy range 195-217 eV. The first observations of negative photoion fragments from these molecules after core excitation are reported. In addition to observing a number of previously known resonances two additional resonant states, just above the Cl 2p ionization limit, are observed and play an important role in the polar photodissociation process. The difficulties in identifying these above threshold spin-split features using negative photoion spectroscopy are discussed.

  3. The production of CO(+) (B2Sigma +) from dissociative photoionization excitation of CO2

    NASA Astrophysics Data System (ADS)

    Wu, C. Y. R.; Judge, D. L.

    1986-04-01

    The dissociative photoionization excitation process in CO2 is studied. In contrast to previous studies, attention is focused on the vibrational and rotational levels produced in fragment ions, partial cross-section measurements for producing such fragment ions in a specific quantum state, and the mechanisms that govern the dissociative ionization excitation processes. The partial fluorescence cross section for the production of CO(+) (B2Sigma +) from CO2 over a wide wavelength range was measured. It is concluded that the production of the CO(+) (B2Sigma +) fragment near the threshold is through a direct dissociative photoionization process.

  4. The production of CO(+) (B2Sigma +) from dissociative photoionization excitation of CO2

    NASA Technical Reports Server (NTRS)

    Wu, C. Y. R.; Judge, D. L.

    1986-01-01

    The dissociative photoionization excitation process in CO2 is studied. In contrast to previous studies, attention is focused on the vibrational and rotational levels produced in fragment ions, partial cross-section measurements for producing such fragment ions in a specific quantum state, and the mechanisms that govern the dissociative ionization excitation processes. The partial fluorescence cross section for the production of CO(+) (B2Sigma +) from CO2 over a wide wavelength range was measured. It is concluded that the production of the CO(+) (B2Sigma +) fragment near the threshold is through a direct dissociative photoionization process.

  5. Absolute partial photoionization cross sections of ozone.

    SciTech Connect

    Berkowitz, J.; Chemistry

    2008-04-01

    Despite the current concerns about ozone, absolute partial photoionization cross sections for this molecule in the vacuum ultraviolet (valence) region have been unavailable. By eclectic re-evaluation of old/new data and plausible assumptions, such cross sections have been assembled to fill this void.

  6. Photoionization of Atomic Oxygen and Nitrogen

    NASA Technical Reports Server (NTRS)

    Dalgarno, Alexander

    1960-01-01

    A knowledge of the photoionization cross sections of atomic oxygen and atomic nitrogen from the spectral heads down to the x-ray region is necessary for the interpretaton of the behavior of the ionized layers. In this note we examine the available theoretical and experimental data and obtain sets of recommended values.

  7. K-shell photoionization of Li, Be+ and B2+

    NASA Astrophysics Data System (ADS)

    Li, Jun; Liu, Jian Dang; Zhang, Song Bin; Ye, Bang Jiao

    2016-06-01

    K-shell photoionization (PI) of Li, Be+ and B2+ from ground state 1s22s2Se have been studied by using the R-matrix method with pseudostates. The K-shell PI process is featured with the contributions from the core-excited metastable states or dominated by the Auger states 2Po. The resonant parameters of the Auger states 2Po and the PI cross-sections have been calculated and compared with the available experimental and theoretical works. Our results agree very well with that of the published works. It is worth noting that compared with previous theoretical calculations, our results of B2+ show better agreements with the latest high-resolution advanced light source measurements [A. Müller et al., J. Phys. B 43 (2010) 135602].

  8. THE PHOTOIONIZED ACCRETION DISK IN HER X-1

    SciTech Connect

    Ji, L.; Schulz, N.; Nowak, M.; Marshall, H. L.; Kallman, T.

    2009-08-01

    We present an analysis of several high-resolution Chandra grating observations of the X-ray binary pulsar Her X-1. With a total exposure of 170 ks, the observations are separated by years and cover three combinations of orbital and superorbital phases. Our goal is to determine distinct properties of the photoionized emission and its dependence on phase-dependent variations of the continuum. We find that the continua can be described by a partial covering model which above 2 keV is consistent with recent results from Rossi X-Ray Timing Explorer studies and at low energies is consistent with recent XMM-Newton and BeppoSAX studies. Besides a power law with fixed index, an additional thermal blackbody of 114 eV is required to fit wavelengths above 12 A ({approx}1 keV). We find that likely all the variability is caused by highly variable absorption columns in the range (1-3) x 10{sup 23} cm{sup -2}. Strong Fe K line fluorescence in almost all observations reveals that dense, cool material is present not only in the outer regions of the disk but interspersed throughout the disk. Most spectra show strong line emission stemming from a photoionized accretion disk corona (ADC). We model the line emission with generic thermal plasma models as well as with the photoionization code XSTAR and investigate changes of the ionization balance with orbital and superorbital phases. Most accretion disk coronal properties such as disk radii, temperatures, and plasma densities are consistent with previous findings for the low state. We find that these properties change negligibly with respect to orbital and superorbital phases. A couple of the higher energy lines exhibit emissivities that are significantly in excess of expectations from a static ADC.

  9. Localization of 4D gravity on pure geometrical thick branes

    SciTech Connect

    Barbosa-Cendejas, Nandinii; Herrera-Aguilar, Alfredo

    2006-04-15

    We consider the generation of thick brane configurations in a pure geometric Weyl integrable 5D spacetime which constitutes a non-Riemannian generalization of Kaluza-Klein (KK) theory. In this framework, we show how 4D gravity can be localized on a scalar thick brane which does not necessarily respect reflection symmetry, generalizing in this way several previous models based on the Randall-Sundrum (RS) system and avoiding both, the restriction to orbifold geometries and the introduction of the branes in the action by hand. We first obtain a thick brane solution that preserves 4D Poincare invariance and breaks Z{sub 2}-symmetry along the extra dimension which, indeed, can be either compact or extended, and supplements brane solutions previously found by other authors. In the noncompact case, this field configuration represents a thick brane with positive energy density centered at y=c{sub 2}, whereas pairs of thick branes arise in the compact case. Remarkably, the Weylian scalar curvature is nonsingular along the fifth dimension in the noncompact case, in contraposition to the RS thin brane system. We also recast the wave equations of the transverse traceless modes of the linear fluctuations of the classical background into a Schroedinger's equation form with a volcano potential of finite bottom in both the compact and the extended cases. We solve Schroedinger equation for the massless zero mode m{sup 2}=0 and obtain a single bound wave function which represents a stable 4D graviton. We also get a continuum gapless spectrum of KK states with m{sup 2}>0 that are suppressed at y=c{sub 2} and turn asymptotically into plane waves.

  10. Inner-shell Photoionization Studies of Neutral Atomic Nitrogen

    NASA Astrophysics Data System (ADS)

    Stolte, W. C.; Jonauskas, V.; Lindle, D. W.; Sant'Anna, M. M.; Savin, D. W.

    2016-02-01

    Inner-shell ionization of a 1s electron by either photons or electrons is important for X-ray photoionized objects such as active galactic nuclei and electron-ionized sources such as supernova remnants. Modeling and interpreting observations of such objects requires accurate predictions for the charge state distribution (CSD), which results as the 1s-hole system stabilizes. Due to the complexity of the complete stabilization process, few modern calculations exist and the community currently relies on 40-year-old atomic data. Here, we present a combined experimental and theoretical study for inner-shell photoionization of neutral atomic nitrogen for photon energies of 403-475 eV. Results are reported for the total ion yield cross section, for the branching ratios for formation of N+, {{{N}}}2+, and {{{N}}}3+, and for the average charge state. We find significant differences when comparing to the data currently available to the astrophysics community. For example, while the branching ratio to {{{N}}}2+ is somewhat reduced, that for N+ is greatly increased, and that to {{{N}}}3+, which was predicted to be zero, grows to ≈ 10% at the higher photon energies studied. This work demonstrates some of the shortcomings in the theoretical CSD data base for inner-shell ionization and points the way for the improvements needed to more reliably model the role of inner-shell ionization of cosmic plasmas.

  11. Photoionization of He above the n =2 threshold

    SciTech Connect

    Sanchez, I.; Martriaan, F. )

    1991-12-01

    We report a theoretical study of He(1{ital s}{sup 2})+{ital h}{nu}{r arrow}He{sup +}(1{ital s},2{ital s},2{ital p})+{ital e}{sup {minus}} photoionization processes, for photon energies greater than 65.4 eV. We pay special attention to the energy region 69.0--73.0 eV, where recent synchrotron experiments exhibit clearly resonant structure associated to 3{ital lnl}{prime} doubly excited states of He. Our method is based on a Feshbach partitioning of the total wave function that includes explicitly resonant structure. Total and partial cross sections do not depend on parametrization, although an obvious one can be obtained in a straightforward manner in the vicinity of isolated resonances; this is very useful for the analysis of most of the resonance peaks observed experimentally. An appealing feature of our approach is the use of {ital L}{sup 2}-integrable basis sets to describe the scattering wave functions. Our discretization method provides coupled continuum states with the proper {delta}-function normalization and with the correct asymptotic behavior. With this method, we have calculated partial photoionization cross sections for leaving the ion in the 1{ital s}, 2{ital s}, and 2{ital p} levels, and the results are in good agreement with recently published experimental data. A complete set of parameters describing the first twelve resonances in partial cross sections is also provided.

  12. 4-D ultrafast shear-wave imaging.

    PubMed

    Gennisson, Jean-Luc; Provost, Jean; Deffieux, Thomas; Papadacci, Clément; Imbault, Marion; Pernot, Mathieu; Tanter, Mickael

    2015-06-01

    Over the last ten years, shear wave elastography (SWE) has seen considerable development and is now routinely used in clinics to provide mechanical characterization of tissues to improve diagnosis. The most advanced technique relies on the use of an ultrafast scanner to generate and image shear waves in real time in a 2-D plane at several thousands of frames per second. We have recently introduced 3-D ultrafast ultrasound imaging to acquire with matrix probes the 3-D propagation of shear waves generated by a dedicated radiation pressure transducer in a single acquisition. In this study, we demonstrate 3-D SWE based on ultrafast volumetric imaging in a clinically applicable configuration. A 32 × 32 matrix phased array driven by a customized, programmable, 1024-channel ultrasound system was designed to perform 4-D shear-wave imaging. A matrix phased array was used to generate and control in 3-D the shear waves inside the medium using the acoustic radiation force. The same matrix array was used with 3-D coherent plane wave compounding to perform high-quality ultrafast imaging of the shear wave propagation. Volumetric ultrafast acquisitions were then beamformed in 3-D using a delay-and-sum algorithm. 3-D volumetric maps of the shear modulus were reconstructed using a time-of-flight algorithm based on local multiscale cross-correlation of shear wave profiles in the three main directions using directional filters. Results are first presented in an isotropic homogeneous and elastic breast phantom. Then, a full 3-D stiffness reconstruction of the breast was performed in vivo on healthy volunteers. This new full 3-D ultrafast ultrasound system paves the way toward real-time 3-D SWE. PMID:26067040

  13. Time-dependent local density approximation study of attosecond time delays in the photoionization of xenon

    NASA Astrophysics Data System (ADS)

    Magrakvelidze, Maia; Madjet, Mohamed; Chakraborty, Himadri

    2016-05-01

    We investigate Wigner-Smith (WS) time delays of the photoionization from various subshells of xenon using the time-dependent local density approximation (TDLDA) with the Leeuwen and Baerends exchange-correlation functional. At the 4d giant dipole resonance region as well as near all the Cooper minimum anti-resonances in 5p, 5s and 4d photoemissions, effects of electron correlations uniquely determine the shapes of the emission quantum phase. The Wigner-Smith time delay derived from this phase indicates significant variations as a function of energy. The results qualitatively support our TDLDA predictions at the fullerene plasmon region and at 3p Cooper minimum in argon, and should encourage attosecond measurements of Xe photoemission via two-photon interferometric techniques, such as RABITT. The work is supported by the NSF, USA.

  14. 17 CFR 260.4d-8 - Content.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 17 Commodity and Securities Exchanges 3 2013-04-01 2013-04-01 false Content. 260.4d-8 Section 260.4d-8 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION (CONTINUED) GENERAL RULES AND REGULATIONS, TRUST INDENTURE ACT OF 1939 Rules Under Section 304 § 260.4d-8 Content. (a)...

  15. 17 CFR 260.4d-8 - Content.

    Code of Federal Regulations, 2012 CFR

    2005-04-01

    ... 17 Commodity and Securities Exchanges 3 2005-04-01 2005-04-01 false Content. 260.4d-8 Section 260.4d-8 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION (CONTINUED) GENERAL RULES AND REGULATIONS, TRUST INDENTURE ACT OF 1939 Rules Under Section 304 § 260.4d-8 Content. (a)...

  16. 17 CFR 260.4d-8 - Content.

    Code of Federal Regulations, 2013 CFR

    2000-04-01

    ... 17 Commodity and Securities Exchanges 3 2000-04-01 2000-04-01 false Content. 260.4d-8 Section 260.4d-8 Commodity and Securities Exchanges GENERAL RULES AND REGULATIONS, TRUST INDENTURE ACT OF 1939 Rules Under Section 304 § 260.4d-8 Content. (a) Each application for an order under section 304(d)...

  17. 17 CFR 260.4d-8 - Content.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 17 Commodity and Securities Exchanges 3 2011-04-01 2011-04-01 false Content. 260.4d-8 Section 260.4d-8 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION (CONTINUED) GENERAL RULES AND REGULATIONS, TRUST INDENTURE ACT OF 1939 Rules Under Section 304 § 260.4d-8 Content. (a)...

  18. 17 CFR 260.4d-8 - Content.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 17 Commodity and Securities Exchanges 3 2012-04-01 2012-04-01 false Content. 260.4d-8 Section 260.4d-8 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION (CONTINUED) GENERAL RULES AND REGULATIONS, TRUST INDENTURE ACT OF 1939 Rules Under Section 304 § 260.4d-8 Content. (a)...

  19. 17 CFR 260.4d-8 - Content.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 17 Commodity and Securities Exchanges 3 2010-04-01 2010-04-01 false Content. 260.4d-8 Section 260.4d-8 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION (CONTINUED) GENERAL RULES AND REGULATIONS, TRUST INDENTURE ACT OF 1939 Rules Under Section 304 § 260.4d-8 Content. (a)...

  20. 76 FR 55814 - 2,4-D; Pesticide Tolerances

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-09

    ... AGENCY 40 CFR Part 180 2,4-D; Pesticide Tolerances AGENCY: Environmental Protection Agency (EPA). ACTION: Final rule. SUMMARY: This regulation establishes tolerances for residues of 2,4-D in or on teff, bran... 180.142 be amended by establishing a tolerance for residues of the herbicide 2,4-D...

  1. 17 CFR 260.4d-8 - Content.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 17 Commodity and Securities Exchanges 4 2014-04-01 2014-04-01 false Content. 260.4d-8 Section 260.4d-8 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION (CONTINUED) GENERAL RULES AND REGULATIONS, TRUST INDENTURE ACT OF 1939 Rules Under Section 304 § 260.4d-8 Content. (a)...

  2. Double Photoionization of Beryllium atoms using Effective Charge approximation

    NASA Astrophysics Data System (ADS)

    Saha, Haripada

    2016-05-01

    We plan to report the results of our investigation on double photoionization K-shell electrons from Beryllium atoms. We will present the results of triple differential cross sections at excess energy of 20 eV using our recently extended MCHF method. We will use multiconfiguration Hartree Fock method to calculate the wave functions for the initial state. The final state wave functions will be obtained in the angle depended Effective Charge approximation which accounts for electron correlation between the two final state continuum electrons. We will discuss the effect of core correlation and the valence shell electrons in the triple differential cross section. The results will be compared with the available accurate theoretical calculations and experimental findings.

  3. Photodissociation of Small Molecules and Photoionization of Free Radicals Using the VUV Velocity-Map Imaging Photoion and Photoelectron Method

    NASA Astrophysics Data System (ADS)

    Gao, Hong

    The tunable vacuum ultraviolet (VUV) laser generated through the two-photon resonance-enhanced four-wave mixing scheme is combined with the newly developed time-slice velocity map imaging photoion method to study the photodissociation of small molecules in the VUV region, and with the velocity map imaging photoelectron method to study the photoionization of free radicals. The photodissociation dynamics of NO in the energy region around 13.5 eV has been investigated. Branching ratios of the three lowest dissociation channels of 12C 16O that produce C(3P) + O(3P), C( 1D) + O(3P) and C(3P) + O(1D) are measured for the first time in the VUV region from 102,500 cm-1 to 110,500 cm-1, valuable information of the dissociation dynamics for this prototype system has been deduced. We demonstrated an experiment that has two independently tunable VUV lasers and a time-slice velocity map imaging setup, this provides us a global way to perform systematic state-selected photodissociation of small molecules via state-selected detection of the atomic products in the VUV region. The velocity map imaging photoelectron method was successfully used to obtain the photoelectron spectrum of the propargyl radical (C3H3) via a single VUV photoionization process. The propargyl radical is generated by the 193 nm laser photodissociation of the precursor C3H3Cl. This is the first time that the velocity map imaging photoelectron method is used to get the photoelectron spectra of free radicals, indicating that it is a powerful technique for studying the photoionization of free radicals which are always hard to be produced with high enough number densities for spectroscopic studies. This dissertation is mainly based on the following peer-reviewed journal articles: 1. Hong Gao, Yang Pan, Lei Yang, Jingang Zhou, C. Y. Ng and William M. Jackson. "Time-slice velocity-map ion imaging studies of the Photodissociation of NO in the vacuum ultraviolet region", the Journal of Chemical Physics, 136, 134302

  4. 4D electron microscopy: principles and applications.

    PubMed

    Flannigan, David J; Zewail, Ahmed H

    2012-10-16

    achievable with short intense pulses containing a large number of electrons, however, are limited to tens of nanometers and nanoseconds, respectively. This is because Coulomb repulsion is significant in such a pulse, and the electrons spread in space and time, thus limiting the beam coherence. It is therefore not possible to image the ultrafast elementary dynamics of complex transformations. The challenge was to retain the high spatial resolution of a conventional TEM while simultaneously enabling the temporal resolution required to visualize atomic-scale motions. In this Account, we discuss the development of four-dimensional ultrafast electron microscopy (4D UEM) and summarize techniques and applications that illustrate the power of the approach. In UEM, images are obtained either stroboscopically with coherent single-electron packets or with a single electron bunch. Coulomb repulsion is absent under the single-electron condition, thus permitting imaging, diffraction, and spectroscopy, all with high spatiotemporal resolution, the atomic scale (sub-nanometer and femtosecond). The time resolution is limited only by the laser pulse duration and energy carried by the electron packets; the CCD camera has no bearing on the temporal resolution. In the regime of single pulses of electrons, the temporal resolution of picoseconds can be attained when hundreds of electrons are in the bunch. The applications given here are selected to highlight phenomena of different length and time scales, from atomic motions during structural dynamics to phase transitions and nanomechanical oscillations. We conclude with a brief discussion of emerging methods, which include scanning ultrafast electron microscopy (S-UEM), scanning transmission ultrafast electron microscopy (ST-UEM) with convergent beams, and time-resolved imaging of biological structures at ambient conditions with environmental cells.

  5. Quantum beat oscillations in the two-color-photoionization continuum of neon and their dependence on the intensity of the ionizing laser pulse

    SciTech Connect

    Geiseler, Henning; Rottke, Horst; Steinmeyer, Guenter; Sandner, Wolfgang

    2011-09-15

    We investigate quantum beat oscillations in the photoionization continuum of Ne atoms that are photoionized by absorption of two photons via a group of excited bound states using ultrashort extreme ultraviolet and infrared laser pulses. The extreme ultraviolet pulse starts an excited-state wave packet that is photoionized by a high-intensity infrared pulse after a variable time delay. We analyze the continuum quantum beats from this two-step photoionization process and their dependence on the photoelectron kinetic energy. We find a pronounced dependence of the quantum beat amplitudes on the photoelectron kinetic energy. The dependence changes significantly with the applied infrared laser-pulse intensity. The experimental results are in good qualitative agreement with a model calculation that is adapted to the experimental situation. It accounts for the intensity dependence of the quantum beat structure through the coupling of the excited-state wave packet to other bound Ne states induced by the high-intensity infrared laser pulse.

  6. Photoionization capable, extreme and vacuum ultraviolet emission in developing low temperature plasmas in air

    NASA Astrophysics Data System (ADS)

    Stephens, J.; Fierro, A.; Beeson, S.; Laity, G.; Trienekens, D.; Joshi, R. P.; Dickens, J.; Neuber, A.

    2016-04-01

    Experimental observation of photoionization capable extreme ultraviolet and vacuum ultraviolet emission from nanosecond timescale, developing low temperature plasmas (i.e. streamer discharges) in atmospheric air is presented. Applying short high voltage pulses enabled the observation of the onset of plasma formation exclusively by removing the external excitation before spark development was achieved. Contrary to the common assumption that radiative transitions from the b{{}1}{{\\Pi}u} (Birge-Hopfield I) and b{{}\\prime 1}Σu+ (Birge-Hopfield II) singlet states of N2 are the primary contributors to photoionization events, these results indicate that radiative transitions from the c{{4\\prime}1}Σu+ (Carroll-Yoshino) singlet state of N2 are dominant in developing low temperature plasmas in air. In addition to c{}4\\prime transitions, photoionization capable transitions from atomic and singly ionized atomic oxygen were also observed. The inclusion of c{{4\\prime}1}Σu+ transitions into a statistical photoionization model coupled with a fluid model enabled streamer growth in the simulation of positive streamers.

  7. Double-photoionization of CO few eV above threshold

    NASA Astrophysics Data System (ADS)

    Belkacem, A.; Osipov, T.; Hertlein, M.; Prior, M.; Adaniya, H.; Feinberg, B.; Weber, Th.; Jahnke, T.; Dorner, R.; Schmidt, L.; Schoffler, M.; Jagutzki, O.; Cocke, C. L.; Landers, A.

    2006-05-01

    We measured double photoionization of CO molecules at 48 eV photon energy. The double ionization of CO produces mostly C^+ + O^+ fragments with non-measurable amounts of CO^2+. The formation of C^+ + O^+ can proceed through two possible channels: a) Direct ionization of two electron into the continuum -- similar to the H2 double ionization -- direct channel. b) Ionization of one electron into the continuum followed by autoionization of a second electron -- Indirect channel. The electron distribution measured with a COLTRIMS shows a very clear distinction of the direct and indirect channels. The kinetic energy release spectrum shows a series of peaks corresponding to the transient vibrational states of the various electronic states of (CO^2+)*. These states are similar to previous measurements at higher energies (K-shell photoionization). (CO^2+)* is found to predissociate through a ^3σ^- and ^1δ dissociative states leading to considerably faster dissociation times than natural lifetimes of the electronic bound states.

  8. Double Photoionization of He and H2

    NASA Astrophysics Data System (ADS)

    Colgan, J.; Pindzola, M. S.; Robicheaux, F.

    2006-01-01

    Photoionization cross sections for both atomic helium and molecular hydrogen have recently been calculated using a time-dependent close-coupling method. The total electronic wavefunction for the two electron system is expanded in six dimensions, where four dimensions are represented on a radial and angular lattice and a coupled channels expansion is used to represent the other two dimensions. The double photoionization cross sections obtained for both He and H2 for a range of photon energies above the complete fragmentation threshold were compared with absolute experimental measurements. Very good agreement is found with experiment. Our method is also capable of being extended to calculations of single and triple differential cross sections of H2.

  9. Entropy of 4D extremal black holes

    NASA Astrophysics Data System (ADS)

    Johnson, Clifford V.; Khuri, Ramzi R.; Myers, Robert C.

    1996-02-01

    We derive the Bekenstein-Hawking entropy formula for four-dimensional Reissner-Nordström extremal black holes in type II string theory. The derivation is performed in two separate (T-dual) weak coupling pictures. One uses a type IIB bound state problem of D5- and D1-branes, while the other uses a bound state problem of D0- and D4-branes with macroscopic fundamental type IIA strings. In both cases, the D-brane systems are also bound to a Kaluza-Klein monopole, which then yields the four-dimensional black hole at strong coupling.

  10. Motion4D-library extended

    NASA Astrophysics Data System (ADS)

    Müller, Thomas

    2011-06-01

    The new version of the Motion4D-library now also includes the integration of a Sachs basis and the Jacobi equation to determine gravitational lensing of pointlike sources for arbitrary spacetimes.New version program summaryProgram title: Motion4D-libraryCatalogue identifier: AEEX_v3_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEEX_v3_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 219 441No. of bytes in distributed program, including test data, etc.: 6 968 223Distribution format: tar.gzProgramming language: C++Computer: All platforms with a C++ compilerOperating system: Linux, WindowsRAM: 61 MbytesClassification: 1.5External routines: Gnu Scientic Library (GSL) (http://www.gnu.org/software/gsl/)Catalogue identifier of previous version: AEEX_v2_0Journal reference of previous version: Comput. Phys. Comm. 181 (2010) 703Does the new version supersede the previous version?: YesNature of problem: Solve geodesic equation, parallel and Fermi-Walker transport in four-dimensional Lorentzian spacetimes. Determine gravitational lensing by integration of Jacobi equation and parallel transport of Sachs basis.Solution method: Integration of ordinary differential equations.Reasons for new version: The main novelty of the current version is the extension to integrate the Jacobi equation and the parallel transport of the Sachs basis along null geodesics. In combination, the change of the cross section of a light bundle and thus the gravitational lensing effect of a spacetime can be determined. Furthermore, we have implemented several new metrics.Summary of revisions: The main novelty of the current version is the integration of the Jacobi equation and the parallel transport of the Sachs basis along null geodesics. The corresponding set of equations readd2xμdλ2=-Γρ

  11. Photoionization models of the CALIFA HII regions

    NASA Astrophysics Data System (ADS)

    Morisset, C.; Delgado-Inglada, G.; Sánchez, S. F.

    2016-06-01

    We present here a short summary of a forthcoming paper on photoionization models based on CALIFA observations of HII regions. For each of the ˜ 20,000 sources of the CALIFA H ii regions catalog, a grid of photoionization models is computed assuming the ionizing SED being described by the underlying stellar population obtained from spectral synthesis modeling. The nebular metallicity (associated to O/H) is defined using the classical strong line method O3N2. The remaining free parameters are the abundance ratio N/O and the ionization parameter U, which are determined by looking for the model fitting [N II]/Hα and [O III]/Hβ. The models are also selected to fit [O II]/Hβ. This process leads to a set of ˜ 3,200 models that reproduce simultaneously the three observations. We determine new relations between the nebular parameters, like the ionization parameter U and the [O II]/[O III] or [S II]/[S III] line ratios. A new relation between N/O and O/H is obtained, mostly compatible with previous empirical determinations (and not with previous results obtained using photoionization models). A new relation between U and O/H is also determined. All the models are publicly available on the Mexican Millions Models database 3MdB.

  12. Theoretical Studies on Photoionization Cross Sections of Solid Gold

    NASA Astrophysics Data System (ADS)

    Ma, Xiao-Guang; Sun, Wei-Guo; Cheng, Yan-Song

    2005-01-01

    Accurate expression for photoabsorption (photoionization) cross sections of high density system proposed recently is used to study the photoionization of solid gold. The results show that the present theoretical photoionization cross sections have good agreement both in structure and in magnitude with the experimental results of gold crystal. The studies also indicate that both the real part ε' and the imaginary part ε'' of the complex dielectric constant ε, and the dielectric influence function of a nonideal system have rich structures in low energy side with a range about 50 eV, and suggest that the influence of particle interactions of surrounding particles with the photoionized particle on the photoionization cross sections can be easily investigated using the dielectric influence function. The electron overlap effects are suggested to be implemented in the future studies to improve the accuracy of theoretical photoionization cross sections of a solid system.

  13. Double and triple photoionization of Li and Be

    SciTech Connect

    Colgan, J.; Pindzola, M.S.; Robicheaux, F.

    2005-08-15

    We present calculations for the double photoionization (with excitation) and the triple photoionization of Li and Be. We extend and more fully discuss the previous calculations made for Li by Colgan et al. [Phys. Rev. Lett. 93, 053201 (2004)] and present calculations for Be. The Be triple photoionization cross sections are compared with previous double shake-off model calculations of Kheifets and Bray [J. Phys. B 36, L211 (2003)], and our calculations are found to be significantly lower.

  14. The 4D-TECS integration for NASA TSRV airplane

    NASA Technical Reports Server (NTRS)

    Kaminer, I.; Oshaughnessy, P. R.

    1989-01-01

    The integration of the Total Energy Control System (TECS) concept with 4D navigation is described. This integration was made to increase the operational capacity of modern aircraft and encourage incorporation of this increased capability with the evolving National Airspace System (NAS). Described herein is: 4D smoothing, the basic concepts of TECS, the spoiler integration concept, an algorithm for nulling out time error, speed and altitude profile modes, manual spoiler implementation, 4D logic, and the results of linear and nonlinear analysis.

  15. Killing Weeds with 2,4-D. Extension Bulletin 389.

    ERIC Educational Resources Information Center

    Lee, Oliver C.

    Discussed is the use of the herbicide 2,4-D. Though written for farmers and agricultural workers, the pamphlet considers turf weed control and use of 2,4-D near ornamental plants. Aspects of the use of this herbicide covered are: (1) the common forms of 2,4-D; (2) plant responses and tolerances to the herbicide; (3) dilution and concentration of…

  16. The role of photoionization in negative corona discharge

    NASA Astrophysics Data System (ADS)

    Lu, B. X.; Sun, H. Y.

    2016-09-01

    The effect of photoionization on the negative corona discharge was simulated based on the needle to plane air gaps. The Trichel pulse, pulse train, electron density and the distribution of electric field will be discussed in this manuscript. Effect of photoionization on the magnitude and interval of the first pulse will be discussed for different applied voltages. It is demonstrated that the peak of the first pulse current could be weakened by photoionization and a critical voltage of the first pulse interval influenced by photoionization was given.

  17. Pros and cons for C4d as a biomarker.

    PubMed

    Cohen, Danielle; Colvin, Robert B; Daha, Mohamed R; Drachenberg, Cinthia B; Haas, Mark; Nickeleit, Volker; Salmon, Jane E; Sis, Banu; Zhao, Ming-Hui; Bruijn, Jan A; Bajema, Ingeborg M

    2012-04-01

    The introduction of C4d in daily clinical practice in the late nineties aroused an ever-increasing interest in the role of antibody-mediated mechanisms in allograft rejection. As a marker of classical complement activation, C4d made it possible to visualize the direct link between anti-donor antibodies and tissue injury at sites of antibody binding in a graft. With the expanding use of C4d worldwide several limitations of C4d were identified. For instance, in ABO-incompatible transplantations C4d is present in the majority of grafts but this seems to point at 'graft accommodation' rather than antibody-mediated rejection. C4d is now increasingly recognized as a potential biomarker in other fields where antibodies can cause tissue damage, such as systemic autoimmune diseases and pregnancy. In all these fields, C4d holds promise to detect patients at risk for the consequences of antibody-mediated disease. Moreover, the emergence of new therapeutics that block complement activation makes C4d a marker with potential to identify patients who may possibly benefit from these drugs. This review provides an overview of the past, present, and future perspectives of C4d as a biomarker, focusing on its use in solid organ transplantation and discussing its possible new roles in autoimmunity and pregnancy. PMID:22297669

  18. Phosphodiesterase 4D Inhibitors Limit Prostate Cancer Growth Potential

    PubMed Central

    Powers, Ginny L.; Hammer, Kimberly D.P.; Domenech, Maribella; Frantskevich, Katsiaryna; Malinowski, Rita L.; Bushman, Wade; Beebe, David J.; Marker, Paul C.

    2014-01-01

    Phosphodiesterase 4D (PDE4D) has recently been implicated as a proliferation-promoting factor in prostate cancer and is over-expressed in human prostate carcinoma. However, the effects of PDE4D inhibition using pharmacological inhibitors have not been examined in prostate cancer. These studies examined the effects of selective PDE4D inhibitors, NVP-ABE171 and cilomilast, as anti-prostate cancer therapies in both in vitro and in vivo models. The effects of PDE4D inhibitors on pathways that are critical in prostate cancer and/or downstream of cyclic AMP (cAMP) were examined. Both NVP-ABE171 and cilomilast decreased cell growth. In vitro, PDE4D inhibitors lead to decreased signaling of the sonic hedgehog (SHH), Androgen Receptor (AR), and MAPK pathways, but growth inhibition was best correlated to the sonic hedgehog pathway. PDE4D inhibition also reduced proliferation of epithelial cells induced by paracrine signaling from co-cultured stromal cells that had activated hedgehog signaling. In addition, PDE4D inhibitors decreased the weight of the prostate in wild-type mice. Prostate cancer xenografts grown in nude mice that were treated with cilomilast or NVP-ABE171 had decreased wet weight and increased apoptosis compared to vehicle treated controls. These studies suggest the pharmacological inhibition of PDE4D using small molecule inhibitors is an effective option for prostate cancer therapy. Implications PDE4D inhibitors decrease the growth of prostate cancer cells in vivo and in vitro, and PDE4D inhibition has therapeutic potential in prostate cancer. PMID:25149359

  19. Laser resonance photoionization spectroscopy of Rydberg levels in Fr

    SciTech Connect

    Andreev, S.V.; Letokhov, V.S.; Mishin, V.I.

    1987-09-21

    We investigated for the first time the high-lying Rydberg levels in the rare radioactive element francium (Fr). The investigations were conducted by the highly sensitive laser resonance atomic photoionization technique with Fr atoms produced at a rate of about 10/sup 3/ atoms/s in a hot cavity. We measured the wave numbers of the 7p/sup 2/P/sub 3/2/..-->..nd/sup 2/D (n = 22--33) and 7p/sup 2/P/sub 3/2/..-->..ns/sup 2/S (n = 23, 25--27,29--31) transitions and found the binding energy of the 7p/sup 2/P/sub 3/2/ state to be T = -18 924.8(3) cm/sup -1/, which made it possible to establish accurately the ionization potential of Fr.

  20. Sensitivity of nonlinear photoionization to resonance substructure in collective excitation

    PubMed Central

    Mazza, T.; Karamatskou, A.; Ilchen, M.; Bakhtiarzadeh, S.; Rafipoor, A. J.; O'Keeffe, P.; Kelly, T. J.; Walsh, N.; Costello, J. T.; Meyer, M.; Santra, R.

    2015-01-01

    Collective behaviour is a characteristic feature in many-body systems, important for developments in fields such as magnetism, superconductivity, photonics and electronics. Recently, there has been increasing interest in the optically nonlinear response of collective excitations. Here we demonstrate how the nonlinear interaction of a many-body system with intense XUV radiation can be used as an effective probe for characterizing otherwise unresolved features of its collective response. Resonant photoionization of atomic xenon was chosen as a case study. The excellent agreement between experiment and theory strongly supports the prediction that two distinct poles underlie the giant dipole resonance. Our results pave the way towards a deeper understanding of collective behaviour in atoms, molecules and solid-state systems using nonlinear spectroscopic techniques enabled by modern short-wavelength light sources. PMID:25854939

  1. Sensitivity of nonlinear photoionization to resonance substructure in collective excitation

    DOE PAGES

    Mazza, T.; Karamatskou, A.; Ilchen, M.; Bakhtiarzadeh, S.; Rafipoor, A. J.; O’Keeffe, P.; Kelly, T. J.; Walsh, N.; Costello, J. T.; Meyer, M.; et al

    2015-04-09

    Collective behaviour is a characteristic feature in many-body systems, important for developments in fields such as magnetism, superconductivity, photonics and electronics. Recently, there has been increasing interest in the optically nonlinear response of collective excitations. Here we demonstrate how the nonlinear interaction of a many-body system with intense XUV radiation can be used as an effective probe for characterizing otherwise unresolved features of its collective response. Resonant photoionization of atomic xenon was chosen as a case study. The excellent agreement between experiment and theory strongly supports the prediction that two distinct poles underlie the giant dipole resonance. Our results pavemore » the way towards a deeper understanding of collective behaviour in atoms, molecules and solid-state systems using nonlinear spectroscopic techniques enabled by modern short-wavelength light sources.« less

  2. Sensitivity of nonlinear photoionization to resonance substructure in collective excitation

    SciTech Connect

    Mazza, T.; Karamatskou, A.; Ilchen, M.; Bakhtiarzadeh, S.; Rafipoor, A. J.; O’Keeffe, P.; Kelly, T. J.; Walsh, N.; Costello, J. T.; Meyer, M.; Santra, R.

    2015-04-09

    Collective behaviour is a characteristic feature in many-body systems, important for developments in fields such as magnetism, superconductivity, photonics and electronics. Recently, there has been increasing interest in the optically nonlinear response of collective excitations. Here we demonstrate how the nonlinear interaction of a many-body system with intense XUV radiation can be used as an effective probe for characterizing otherwise unresolved features of its collective response. Resonant photoionization of atomic xenon was chosen as a case study. The excellent agreement between experiment and theory strongly supports the prediction that two distinct poles underlie the giant dipole resonance. Our results pave the way towards a deeper understanding of collective behaviour in atoms, molecules and solid-state systems using nonlinear spectroscopic techniques enabled by modern short-wavelength light sources.

  3. Photoionization studies of the 2p resonances of atomic calcium

    NASA Astrophysics Data System (ADS)

    Obst, B.; Hansen, J. E.; Sonntag, B.; Wernet, Ph.; Zimmermann, P.

    2002-06-01

    The Ca 2p resonances at 345-355 eV were studied by photoion and photoelectron spectroscopy using monochromatized synchrotron radiation and atomic-beam technique. The analysis of the excitation and decay of these resonances shows strong configuration mixing between the different subshells of the valence electrons 4s, 3d, and 4p. In the case of the 2p-13/2 resonance structure at 348 eV there are two excited states with nearly equal contributions from the configuration 2p53d4s2 and 2p53d24s, which gives rise to strong variations of the resonantly enhanced 3p4(3d,4s)3 photoelectron lines when scanning the photon energy across the resonance.

  4. Sensitivity of nonlinear photoionization to resonance substructure in collective excitation.

    PubMed

    Mazza, T; Karamatskou, A; Ilchen, M; Bakhtiarzadeh, S; Rafipoor, A J; O'Keeffe, P; Kelly, T J; Walsh, N; Costello, J T; Meyer, M; Santra, R

    2015-01-01

    Collective behaviour is a characteristic feature in many-body systems, important for developments in fields such as magnetism, superconductivity, photonics and electronics. Recently, there has been increasing interest in the optically nonlinear response of collective excitations. Here we demonstrate how the nonlinear interaction of a many-body system with intense XUV radiation can be used as an effective probe for characterizing otherwise unresolved features of its collective response. Resonant photoionization of atomic xenon was chosen as a case study. The excellent agreement between experiment and theory strongly supports the prediction that two distinct poles underlie the giant dipole resonance. Our results pave the way towards a deeper understanding of collective behaviour in atoms, molecules and solid-state systems using nonlinear spectroscopic techniques enabled by modern short-wavelength light sources. PMID:25854939

  5. K-shell photoionization of Be-like carbon ions: experiment andtheory for C2+

    SciTech Connect

    Scully, S.W.J.; Aguilar, A.; Emmons, E.D.; Phaneuf, R.A.; Halka,M.; Leitner, D.; Levin, J.C.; Lubell, M.S.; Puettner, R.; Schlachter,A.S.; Covington, A.M.; Schippers, S.; Muller, A.; McLaughlin, B.M.

    2005-06-21

    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.

  6. Photoionization cross-section of isotropic defects or impurity centers in isolators

    NASA Astrophysics Data System (ADS)

    Lima, H.; Batista, J. V.; Couto dos Santos, M. A.

    2016-08-01

    An analytical expression to calculate the photoionization cross-section of isotropic defects or impurity centers is being proposed by using the time-dependent perturbation theory. The ground-state wave function of the electron captured in the impurity state is described by a three-dimensional isotropic harmonic oscillator and the electron excited state in the continuum conduction band is described by a plane wave. The expression has been obtained considering all multipoles terms in the Hamiltonian, and that the radiation field which interacts with electrons is semi-classical and linearly polarized. This approximation is assumed because the effects of the linear contribution are dominant. The available data of the Al2O3:C and Lu2SiO5:Ce systems are in good agreement with our predictions. Such satisfactory comparison is a strong indication that the present model can be used to provide good predictions of the photoionization cross-section in several areas.

  7. 4D Printing with Mechanically Robust, Thermally Actuating Hydrogels.

    PubMed

    Bakarich, Shannon E; Gorkin, Robert; in het Panhuis, Marc; Spinks, Geoffrey M

    2015-06-01

    A smart valve is created by 4D printing of hydrogels that are both mechanically robust and thermally actuating. The printed hydrogels are made up of an interpenetrating network of alginate and poly(N-isopropylacrylamide). 4D structures are created by printing the "dynamic" hydrogel ink alongside other static materials. PMID:25864515

  8. 32 CFR 1645.4 - Exclusion from Class 4-D.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... MINISTERS OF RELIGION § 1645.4 Exclusion from Class 4-D. A registrant is excluded from Class 4-D when his... duly ordained minister of religion in accordance with the ceremonial rite or discipline of a church... principles of religion and administer the ordinances of public worship, as embodied in the creed...

  9. 4D Printing with Mechanically Robust, Thermally Actuating Hydrogels.

    PubMed

    Bakarich, Shannon E; Gorkin, Robert; in het Panhuis, Marc; Spinks, Geoffrey M

    2015-06-01

    A smart valve is created by 4D printing of hydrogels that are both mechanically robust and thermally actuating. The printed hydrogels are made up of an interpenetrating network of alginate and poly(N-isopropylacrylamide). 4D structures are created by printing the "dynamic" hydrogel ink alongside other static materials.

  10. 32 CFR 1645.4 - Exclusion from Class 4-D.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... MINISTERS OF RELIGION § 1645.4 Exclusion from Class 4-D. A registrant is excluded from Class 4-D when his... duly ordained minister of religion in accordance with the ceremonial rite or discipline of a church... principles of religion and administer the ordinances of public worship, as embodied in the creed...

  11. 32 CFR 1645.4 - Exclusion from Class 4-D.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... MINISTERS OF RELIGION § 1645.4 Exclusion from Class 4-D. A registrant is excluded from Class 4-D when his... duly ordained minister of religion in accordance with the ceremonial rite or discipline of a church... principles of religion and administer the ordinances of public worship, as embodied in the creed...

  12. 32 CFR 1645.4 - Exclusion from Class 4-D.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... MINISTERS OF RELIGION § 1645.4 Exclusion from Class 4-D. A registrant is excluded from Class 4-D when his... duly ordained minister of religion in accordance with the ceremonial rite or discipline of a church... principles of religion and administer the ordinances of public worship, as embodied in the creed...

  13. 32 CFR 1645.4 - Exclusion from Class 4-D.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... MINISTERS OF RELIGION § 1645.4 Exclusion from Class 4-D. A registrant is excluded from Class 4-D when his... duly ordained minister of religion in accordance with the ceremonial rite or discipline of a church... principles of religion and administer the ordinances of public worship, as embodied in the creed...

  14. Molecular Photoionization Calculations Using the Complex Basis Function Method.

    NASA Astrophysics Data System (ADS)

    Yu, Chin-Hui

    The complex basis function method (CBF) using both real and complex basis functions has been applied to the calculation of photoionization cross sections. The CBF method requires less computational resources than rigorous full-scattering methods and is effective for the evaluation of shape-resonance features. Neither the number of electrons in the system nor the molecular geometry is restricted. Moreover, the cross section obtained by the CBF method satisfies a variational principle and provides a practical diagnostic tool for the calculation of cross sections. The photoionization cross sections of H _sp{2}{+}, H _2, N_2, CO _2, and SF_6 have been computed using the CBF method. The computed partial cross sections for linear molecules agreed fairly well with other theoretical and experimental values. Particularly encouraging is the nearly perfect agreement of the CBF results with the results by rigorous full-scattering methods in the regions of sharp resonance features such as the K-shell ionization of N_2 and the 4sigma_{rm g} --> ksigma_ {rm u} transition of CO _2. The effect of averaging over all vibrational modes on the ionization cross sections for the 4 sigma_{rm g} orbital in CO_2 has also been studied for the first time. The resonance peak in the totally vibrationally averaged cross sections was reduced by 20%, but still represents a feature which has not yet been detected experimentally. The photoionization of SF_6 valence shells, 1t_{1rm g} , 5t_{1rm u}, 1t_{2rm u}, 3e _{rm g}, 1t_ {2rm g}, 4t_{1 rm u}, and 5a_{1 rm g}, has also been studied for the continuum symmetries a_{1rm g }, t_{1rm u} , e_{rm g}, and t_{2rm g}. The CBF results of SF_6 are numerically stable and essentially approach the static-exchange limit. These static-exchange partial cross sections, however, do not compare well with the experimental measurements. The discrepancy may be attributed to the physical approximations made in the theoretical model and to the quality of the ground -state

  15. Spin effects in double photoionization of lithium

    SciTech Connect

    Kheifets, A. S.; Fursa, D. V.; Hines, C. W.; Bray, I.; Colgan, J.; Pindzola, M. S.

    2010-02-15

    We apply the nonperturbative convergent close-coupling (CCC) and time-dependent close coupling (TDCC) formalisms to calculate fully differential energy and angular resolved cross sections of double photoionization (DPI) of lithium. The equal energy sharing case is considered in which dynamics of the DPI process can be adequately described by two symmetrized singlet and triplet amplitudes. The angular width of these amplitudes serves as a measure of the strength of the angular correlation between the two ejected electrons. This width is interpreted in terms of the spin of the photoelectron pair.

  16. Double photoionization of helium with synchrotron x-rays: Proceedings

    SciTech Connect

    Not Available

    1994-01-01

    This report contains papers on the following topics: Overview and comparison of photoionization with charged particle impact; The ratio of double to single ionization of helium: the relationship of photon and bare charged particle impact ionization; Double photoionization of helium at high energies; Compton scattering of photons from electrons bound in light elements; Electron ionization and the Compton effect in double ionization of helium; Elimination of two atomic electrons by a single energy photon; Double photoionization of helium at intermediate energies; Double Photoionization: Gauge Dependence, Coulomb Explosion; Single and Double Ionization by high energy photon impact; The effect of Compton Scattering on the double to single ionization ratio in helium; and Double ionization of He by photoionization and Compton scattering. These papers have been cataloged separately for the database.

  17. Studies of x-ray emission properties of photoionized plasmas

    NASA Astrophysics Data System (ADS)

    Wang, Feilu; Han, Bo; Jin, Rui; Salzmann, David; Liang, Guiyun; Wei, Huigang; Zhong, Jiayong; Zhao, Gang; Li, Jia-ming

    2016-03-01

    In this paper three aspects of photoionized plasmas are discussed in both laboratory and astrophysical contexts. First, the importance of accurate atomic/ionic data for the analysis of photoionized plasmas is shown. Second, an overview of present computer codes for the analysis of photoionized plasmas is given. We introduce our computer model, radiative-collisional code based on the flexible atomic code (RCF), for calculations of the properties of such plasmas. RCF uses database generated by the flexible atomic code. Using RCF it is shown that incorporating the satellite lines from doubly excited Li-like ions into the He{}α triplet lines is necessary for reliable analysis of observational spectra from astrophysical objects. Finally, we introduce a proposal to generate photoionized plasmas by x-ray free electron laser, which may facilitate the simulation in lab of astrophysical plasmas in photoionization equilibrium.

  18. ATOMIC AND MOLECULAR PHYSICS: Interference effects on the photoionization cross sections between two neighbouring atoms: nitrogen as an example

    NASA Astrophysics Data System (ADS)

    Wu, Jian-Hua; Yuan, Jian-Min

    2009-12-01

    Interference effects on the photoionization cross sections between two neighbouring atoms are considered based on the coherent scattering of the ionized electrons by the two nuclei when their separation is less than or comparable to the de Broglie wave length of the ionized electrons. As an example, the single atomic nitrogen ionization cross section and the total cross sections of two nitrogen atoms with coherently added photoionization amplitudes are calculated from the threshold to about 60 Å (1 Å = 0.1 nm) of the photon energy. The photoionization cross sections of atomic nitrogen are obtained by using the close-coupling R-matrix method. In the calculation 19 states are included. The ionization energy of the atomic nitrogen and the photoionization cross sections agree well with the experimental results. Based on the R-matrix results of atomic nitrogen, the interference effects between two neighbouring nitrogen atoms are obtained. It is shown that the interference effects are considerable when electrons are ionized just above the threshold, even for the separations between the two atoms are larger than two times of the bond length of N2 molecules. Therefore, in hot and dense samples, effects caused by the coherent interference between the neighbours are expected to be observable for the total photoionization cross sections.

  19. RELATIVISTIC R-MATRIX CLOSE-COUPLING CALCULATIONS FOR PHOTOIONIZATION OF Si-LIKE Ni XV

    SciTech Connect

    Singh, Jagjit; Jha, A. K. S.; Mohan, Man

    2010-02-01

    We present relativistic close-coupling photoionization calculations of Ni XV using the Breit-Pauli R-matrix method to obtain photoionization cross section of Ni XV from the ground state 3s {sup 2}3p {sup 2}({sup 3} P {sub 0}) and the lowest four 3s {sup 2}3p {sup 2} ({sup 3} P {sub 1,2}, {sup 1} D {sub 2}, {sup 1} S {sub 0}) excited states. A multiconfiguration eigenfunction expansion of the core Ni XVI is employed with configurations 3s {sup 2}3p, 3s3p {sup 2}, 3s {sup 2}3d, 3p {sup 3}, 3s3p3d, 3p {sup 2}3d, 3s3d {sup 2}, 3p3d {sup 2}. We have included the lowest 40 target level states of Ni XVI in the photoionization calculations of Ni XV. Cross sections are determined by the Rydberg series of autoionizing resonances converging to several ionic states of Ni XVI. In our calculations, we have taken into account all the important physical effects such as exchange, channel coupling, and short-range correlation. Further, relativistic effects are incorporated by including mass correction, Darwin term, and spin-orbit interaction terms. The present calculations using the lowest 40 target levels of Ni XVI are presented for the first time and can be useful for modeling the ionization balance of Ni XV in laboratory and astrophysical plasmas.

  20. 4D Dynamic RNP Annual Interim Report-Year 1

    NASA Technical Reports Server (NTRS)

    Finkelsztein, Daniel M.; Sturdy, James L.; Alaverdi, Omeed; Chung, William W.; Salvano, Daniel; Klooster, Joel; Hochwarth, Joachim K.

    2010-01-01

    experiment using the Airspace and Traffic Operations Simulation (ATOS) system to validate the 4D Dynamic RNP construct. This Annual Interim Report summarizes the activities led by Raytheon, in collaboration with GE Aviation and SAIC, and presents the results obtained during the first year of this research effort to expand the RNP concept to 4 dimensions relative to a dynamic frame of reference. A comprehensive assessment of the state-of-the-art international implementation of current RNP was completed and presented in the Contractor Report RNP State-of-the-Art Assessment, Version 4, 17 December 2008 . The team defined in detail two 4DT operations, Airborne Precision Spacing and Self-Separation, that are ideally suited to be supported by 4D Dynamic RNP and developed their respective conceptual frameworks, Required Interval Management Performance (RIMP) Version 1.1, 13 April 2009 and Required Self Separation Performance (RSSP) Version 1.1, 13 April 2009 . Finally, the team started the development of a mathematical model and simulation tool for RIMP and RSSP scheduled to be delivered during the second year of this research effort.

  1. 4D-fingerprints, universal QSAR and QSPR descriptors.

    PubMed

    Senese, Craig L; Duca, J; Pan, D; Hopfinger, A J; Tseng, Y J

    2004-01-01

    An elusive goal in the field of chemoinformatics and molecular modeling has been the generation of a set of descriptors that, once calculated for a molecule, may be used in a wide variety of applications. Since such universal descriptors are generated free from external constraints, they are inherently independent of the data set in which they are employed. The realization of a set of universal descriptors would significantly streamline such chemoinformatics tasks as virtual high-throughout screening (VHTS) and toxicity profiling. The current study reports the derivation and validation of a potential set of universal descriptors, referred to as the 4D-fingerprints. The 4D-fingerprints are derived from the 4D-molecular similarity analysis. To evaluate the applicability of the 4D-fingerprints as universal descriptors, they are used to generate descriptive QSAR models for 5 independent training sets. Each of the training sets has been analyzed previously by several varying QSAR methods, and the results of the models generated using the 4D-fingerprints are compared to the results of the previous QSAR analyses. It was found that the models generated using the 4D-fingerprints are comparable in quality, based on statistical measures of fit and test set prediction, to the previously reported models for the other QSAR methods. This finding is particularly significant considering the 4D-fingerprints are generated independent of external constraints such as alignment, while the QSAR methods used for comparison all require an alignment analysis.

  2. Physical Mechanisms and Scaling Laws of K-Shell Double Photoionization

    SciTech Connect

    Hoszowska, J.; Dousse, J.-Cl.; Berset, M.; Cao, W.; Fennane, K.; Kayser, Y.; Szlachetko, J.; Szlachetko, M.; Kheifets, A. K.; Bray, I.; Kavcic, M.

    2009-02-20

    We report on the photon energy dependence of the K-shell double photoionization (DPI) of Mg, Al, and Si. The DPI cross sections were derived from high-resolution measurements of x-ray spectra following the radiative decay of the K-shell double vacancy states. Our data evince the relative importance of the final-state electron-electron interaction to the DPI. By comparing the double-to-single K-shell photoionization cross-section ratios for neutral atoms with convergent close-coupling calculations for He-like ions, the effect of outer shell electrons on the K-shell DPI process is assessed. Universal scaling of the DPI cross sections with the effective nuclear charge for neutral atoms is revealed.

  3. Influence of Debye plasmas on photoionization of Li-like ions: Emergence of Cooper minima

    SciTech Connect

    Lin, C. Y.; Ho, Y. K.

    2010-03-15

    The photoionizaton processes of lithium isoelectronic sequence (Be{sup +}, B{sup 2+}, C{sup 3+}, N{sup 4+}, O{sup 5+}, and F{sup 6+}) under the influence of plasma environments are explored using the method of complex coordinate rotation in combination with the model potential approximation. The photoionization cross sections compared to existing theoretical predictions and varied with Debye screening lengths are reported. Under the perturbation of plasmas with certain Debye screening lengths, Cooper minima are uncovered in photoionization cross-section curves of the ground-state Li-like ions, in which the Cooper minima are absent in the respective free ion cases. The relations between the appearance of Cooper minima and the instability of the ground states due to plasma environments are discussed.

  4. Coherent correlation enhancement of outer shell photoionization cross sections of alkali-like ions

    SciTech Connect

    Amusia, M.Y.; Avdonina, B.; Pratt, R.H.

    1995-08-01

    An alkali-like ion interaction with inner electrons of an alkali-like ion leads to a significant increase in the photoionization cross section of the outer s electron. This occurs not only for ground-state ions with one s electron in the outer shell, but also when the outer s electron is in an excited state. The reason for this amplification, in addition to coherent enhancement in summing of the correlation amplitudes, is that the zero in the direct amplitude occurs below threshold. This leads to a constructive interference with the correlation amplitude above the photoionization threshold, in contrast to a destructive interference in the case of a neutral atom with the same electronic configuration, for which the zero occurs above threshold. Results of this research were published.

  5. Two-electron photoionization of endohedral atoms

    NASA Astrophysics Data System (ADS)

    Amusia, M. Ya.; Liverts, E. Z.; Mandelzweig, V. B.

    2006-10-01

    Using He@C60 as an example, we demonstrate that the static potential of the fullerene core essentially alters the cross section of the two-electron ionization differential in one-electron energy dσ++(ω)/dɛ . We found that at high photon energy prominent oscillations appear in it due to reflection of the second slow electron wave on the C60 shell, which “dies out” at relatively high ɛ values, of about 2-3 two-electron ionization potentials. The results were presented for ratios RC60(ω,ɛ)≡dσ++(ω,ɛ)/dσa++(ω,ɛ) , where dσa++(ω,ɛ)/dɛ is the two-electron differential photoionization cross section. We have calculated the ratio Ri,ful=σi++(ω)/σia++(ω) , that accounts for reflection of both photoelectrons by the C60 shell. We have also calculated the value of two-electron photoionization cross section σ++(ω) and found that this value is close to that of an isolated He atom. Results similar to He@C60 are presented for He@C70 and He@C76 .

  6. Two-electron photoionization of endohedral atoms

    NASA Astrophysics Data System (ADS)

    Amusia, Miron; Liverts, Evgeny; Mandelzweig, Victor

    2006-05-01

    Using He@C60 as an example, we demonstrate that static potential of the fullerene core essentially alters the differential in one-electron energy cross section of the two-electron ionization dσ^++(,)/dɛ. We found that at high photon energy prominent oscillations appear in it due to reflection of the second, slow electron wave on the C60 shell, which dies out at relatively high ɛ values, of about 23 two-electron ionization potentials. The results were presented for ratios RC60(φ,ɛ)≡dσ^++(φ,ɛ)/dσ^a++(,), where d&a++circ;(,) /dɛ is the two-electron differential photoionization cross-section. We have calculated also the ratio Ri,ful=σi^++(φ)/σi^a++(φ), that accounts reflection of both photoelectrons by the C60 shell. We have calculated also the value of two-electron photoionization cross section σ^++(φ) and found that this value is close to that of an isolated He atom.

  7. Probing confinement resonances by photoionizing Xe inside a C60+ molecular cage

    NASA Astrophysics Data System (ADS)

    Phaneuf, R. A.; Kilcoyne, A. L. D.; Aryal, N. B.; Baral, K. K.; Thomas, C. M.; Esteves-Macaluso, D. A.; Lomsadze, R.; Gorczyca, T. W.; Ballance, C. P.; Manson, S. T.; Hasoglu, M. F.; Hellhund, J.; Schippers, S.; Müller, A.

    2014-05-01

    Double photoionization accompanied by loss of n C atoms (n = 0 , 2 , 4 , 6) was investigated by merging beams of Xe@C60+ ions and synchrotron radiation and measuring the yields of product ions. The giant 4 d dipole resonance of the caged Xe atom has a prominent signature in the cross section for these product channels, which together account for 6 . 2 +/- 1 . 4 of the total Xe 4 d oscillator strength of 10. Compared to that for a free Xe atom, the oscillator strength is redistributed in photon energy due to multipath interference of outgoing Xe 4 d photoelectron waves that may be transmitted or reflected by the spherical C60+ molecular cage, yielding so-called confinement resonances. The data are compared with an earlier measurement and with theoretical predictions for this single-molecule photoelectron interferometer system. Relativistic R-matrix calculations for the Xe atom in a spherical potential shell representing the fullerene cage show the sensitivity of the interference pattern to the molecular geometry.

  8. Probing confinement resonances by photoionizing Xe inside a C60+ molecular cage

    NASA Astrophysics Data System (ADS)

    Phaneuf, R. A.; Kilcoyne, A. L. D.; Aryal, N. B.; Baral, K. K.; Esteves-Macaluso, D. A.; Thomas, C. M.; Hellhund, J.; Lomsadze, R.; Gorczyca, T. W.; Ballance, C. P.; Manson, S. T.; Hasoglu, M. F.; Schippers, S.; Müller, A.

    2013-11-01

    Double photoionization accompanied by loss of n C atoms (n=0, 2, 4, 6) was investigated by merging beams of Xe@C60+ ions and synchrotron radiation and measuring the yields of product ions. The giant 4d dipole resonance of the caged Xe atom has a prominent signature in the cross section for these product channels, which together account for 6.2 ± 1.4 of the total Xe 4d oscillator strength of 10. Compared to that for a free Xe atom, the oscillator strength is redistributed in photon energy due to multipath interference of outgoing Xe 4d photoelectron waves that may be transmitted or reflected by the spherical C60+ molecular cage, yielding so-called confinement resonances. The data are compared with an earlier measurement and with theoretical predictions for this single-molecule photoelectron interferometer system. Relativistic R-matrix calculations for the Xe atom in a spherical potential shell representing the fullerene cage show the sensitivity of the interference pattern to the molecular geometry.

  9. Photoionization of optically trapped ultracold atoms with a high-power light-emitting diode

    SciTech Connect

    Goetz, Simone; Hoeltkemeier, Bastian; Amthor, Thomas; Weidemueller, Matthias

    2013-04-15

    Photoionization of laser-cooled atoms using short pulses of a high-power light-emitting diode (LED) is demonstrated. Light pulses as short as 30 ns have been realized with the simple LED driver circuit. We measure the ionization cross section of {sup 85}Rb atoms in the first excited state, and show how this technique can be used for calibrating efficiencies of ion detector assemblies.

  10. Internal energy selection in vacuum ultraviolet photoionization of ethanol and ethanol dimers

    NASA Astrophysics Data System (ADS)

    Bodi, Andras

    2013-10-01

    Internal energy selected ethanol monomer and ethanol dimer ions were prepared by threshold photoionization of a supersonic molecular beam seeded with ethanol. The dissociative photoionization processes of the monomer, the lowest-energy CH3-loss channel of the dimer, and the fragmentation of larger clusters were found to be disjunct from the ionization onset to about 12 eV, which made it possible to determine the 0 K appearance energy of C-C bond breaking in the H-donor unit of the ethanol dimer cation as 9.719 ± 0.004 eV. This reaction energy is used together with ab initio calculations in a thermochemical cycle to determine the binding energy change from the neutral ethanol dimer to a protonated ethanol-formaldehyde adduct. The cycle also shows general agreement between experiment, theory, and previously published enthalpies of formation. The role of the initial ionization site, or rather the initial photoion state, is also discussed based on the dimer breakdown diagram and excited state calculations. There is no evidence for isolated state behavior, and the ethanol dimer dissociative photoionization processes appear to be governed by statistical theory and the ground electronic state of the ion. In the monomer breakdown diagram, the smoothly changing branching ratio between H and CH3 loss is at odds with rate theory predictions, and shows that none of the currently employed few-parameter rate models, appropriate for experimental rate curve fitting, yields a correct description for this process in the experimental energy range.

  11. Ultrafast Electronic And Nuclear Dynamics In Dissociative Photoionization Of Molecular Hydrogen and Deuterium

    NASA Astrophysics Data System (ADS)

    Billaud, P.; Picard, Y. J.; Géléoc, M.; Hergott, J.-F.; Carré, B.; Breger, P.; Ruchon, T.; Veyrinas, K.; Roulliay, M.; Delmotte, F.; Böttcher, M.; Huetz, A.; Dowek, D.

    2012-11-01

    Single-photon dissociative photoionization of H2/D2 in the Q1, Q2 doubly excited states resonance regions, where ultrafast electronic and nuclear dynamics are coupled, is studied using the vector-correlation method with single selected femtosecond high-order harmonic and synchrotron radiation in the VUV. Results are compared at the level of electron-ion kinetic energy correlation diagrams, asymmetry parameters, and the molecular frame photoelectron angular distributions.

  12. K-shell Photoionization of Na-like to Cl-like Ions of Mg, Si, S, Ar, and Ca

    NASA Technical Reports Server (NTRS)

    Witthoeft, M. C.; Garcia, J.; Kallman, T. R.; Bautista, M. A.; Mendoza, C.; Palmeri, P.; Quinet, P.

    2010-01-01

    We present R-matrix calculations of photoabsorption and photoionization cross sections across the K edge of Mg, Si, S, Ar, and Ca ions with more than 10 electrons. The calculations include the effects of radiative and Auger damping by means of an optical potential. The wave functions are constructed from single-electron. orbital bases obtained using a Thomas-Fermi-Dirac statistical model potential. Configuration interaction is considered among all states up to n = 3. The damping processes affect the resonances converging to the K-thresholds causing them to display symmetric profiles of constant width that smear the otherwise sharp edge at the photoionization threshold. These data are important for the modeling of features found in photoionized plasmas.

  13. K-SHELL PHOTOIONIZATION OF Na-LIKE TO Cl-LIKE IONS OF Mg, Si, S, Ar, AND Ca

    SciTech Connect

    Witthoeft, M. C.; Garcia, J.; Kallman, T. R.; Bautista, M. A.; Mendoza, C.; Palmeri, P.; Quinet, P.

    2011-01-15

    We present R-matrix calculations of photoabsorption and photoionization cross sections across the K edge of Mg, Si, S, Ar, and Ca ions with more than 10 electrons. The calculations include the effects of radiative and Auger damping by means of an optical potential. The wave functions are constructed from single-electron orbital bases obtained using a Thomas-Fermi-Dirac statistical model potential. Configuration interaction is considered among all states up to n = 3. The damping processes affect the resonances converging to the K-thresholds causing them to display symmetric profiles of constant width that smear the otherwise sharp edge at the photoionization threshold. These data are important for the modeling of features found in photoionized plasmas.

  14. Double imaging photoelectron photoion coincidence sheds new light on the dissociation of energy-selected CH3Cl(+) ions.

    PubMed

    Tang, Xiaofeng; Lin, Xiaoxiao; Zhang, Weijun; Garcia, Gustavo A; Nahon, Laurent

    2016-09-14

    The vacuum ultraviolet (VUV) photoionization and dissociative photoionization of CH3Cl in the energy range of 11-17 eV have been investigated in detail by combining synchrotron radiation and double imaging photoelectron photoion coincidences (i(2)PEPICO). Three low-lying electronic states of the CH3Cl(+) molecular ion, X(2)E, A(2)A1 and B(2)E, were prepared and analyzed. The appearance energies of the energetically accessible fragment ions, CH2Cl(+), CHCl(+), CH3(+) and CH2(+), have been obtained from their respective mass-selected threshold photoelectron spectra (TPES) or photoionization efficiency (PIE) curves. The dissociation mechanisms of energy-selected CH3Cl(+) ions, prepared in the A(2)A1 and the B(2)E electronic states, as well as outside the Franck-Condon region, have been revealed to be state-specific via ion/electron kinetic energy correlation diagrams. In particular, the umbrella mode vibrational progression of the CH3(+) fragment ion in the direct dissociation of the A(2)A1 electronic state was identified and assigned indicating that this state correlates to the CH3(+)(1(1)A1') + Cl((2)P1/2) dissociation limit, in agreement with the theoretical calculations performed in this work. PMID:27524637

  15. Dirac R-matrix calculations of photoionization cross-sections of Ca IV

    NASA Astrophysics Data System (ADS)

    Nazir, R. T.; Bari, M. A.; Sardar, S.; Bilal, M.; Salahuddin, M.; Nasim, M. H.

    2016-08-01

    In this paper total photoionization cross sections in the ground (^2P^o_{3/2}) and two meta-stable states (^2P^o_{1/2},^2S_{1/2}) of Ca IV are reported using the relativistic Dirac Atomic R-matrix Codes (DARC) in the photon energy range 67-122 eV. The target wavefunctions are constructed with fully relativistic atomic structure GRASP package. A total of lowest lying 48 fine-structure levels arising from the four main configuration (3s23p4, 3s3p5 3s23p33d, 3p6) are considered for the target wavefunctions expansion. Our calculated eigenvalues of the core ion Ca V show reasonable agreement with available experimental and theoretical results. It is found that present ionization threshold energies of first three levels of Ca IV are in excellent agreement with NIST energies and experimental measurements. The photoionization cross sections of Ca IV are calculated with an appropriate energy step (0.1× 10-3 eV) to describe the resonance structures in vivid details. A comparison for the statistically weighted mixture of states (^2P^o_{3/2},^2P^o_{1/2}) with other experimental measurements including term-resolved ground state theoretical calculations is presented. Our computed photoionization cross sections agree better with the measured cross sections than the other theoretical approaches and are potentially more accurate.

  16. Dirac R-matrix calculations of photoionization cross-sections of Ca IV

    NASA Astrophysics Data System (ADS)

    Nazir, R. T.; Bari, M. A.; Sardar, S.; Bilal, M.; Salahuddin, M.; Nasim, M. H.

    2016-11-01

    In this paper total photoionization cross-sections in the ground (^2P^o_{3/2}) and two meta-stable states (^2P^o_{1/2},^2S_{1/2}) of Ca IV are reported using the relativistic Dirac Atomic R-matrix Codes (DARC) in the photon energy range 67-122 eV. The target wavefunctions are constructed with fully relativistic atomic structure GRASP package. A total of lowest lying 48 fine-structure levels arising from the four main configuration (3s23p4, 3s3p5 3s23p33d, 3p6) are considered for the target wavefunctions expansion. Our calculated eigenvalues of the core ion Ca V show reasonable agreement with available experimental and theoretical results. It is found that present ionization threshold energies of first three levels of Ca IV are in excellent agreement with NIST energies and experimental measurements. The photoionization cross-sections of Ca IV are calculated with an appropriate energy step (0.1 × 10-3 eV) to describe the resonance structures in vivid details. A comparison for the statistically weighted mixture of states (^2P^o_{3/2},^2P^o_{1/2}) with other experimental measurements including term-resolved ground state theoretical calculations is presented. Our computed photoionization cross-sections agree better with the measured cross-sections than the other theoretical approaches and are potentially more accurate.

  17. C4d staining as immunohistochemical marker in inflammatory myopathies.

    PubMed

    Pytel, Peter

    2014-10-01

    The diagnosis of an inflammatory myopathy is often established based on basic histologic studies. Additional immunohistochemical studies are sometimes required to support the diagnosis and the classification of inflammatory myopathies. Staining for major histocompatibility complex 1 (MHC1) often shows increased sarcolemmal labeling in inflammatory myopathies. Endomysial capillary staining C5b-9 (membrane attack complex) is a feature that is reported as frequently associated with dermatomyositis. Immunohistochemical staining for C4d is widely used for various applications including the assessment of antibody-mediated rejection after solid organ transplantation. In the context of dermatomyositis, C4d staining has been described in skin biopsies but not in muscle biopsies. A total of 32 muscle biopsy specimens were examined. The hematoxylin and eosin-stained slides were reviewed, and immunohistochemical studies for MHC1, C5b-9, and C4d were conducted. The staining observed for C5b-9 and C4d was compared. Overall, the staining pattern for C4d mirrored the one observed for C5b-9 in the examined muscle biopsy specimens. There was high and statistically significant (P<0.0001) correlation between the staining seen with these 2 antibodies. Both antibodies labeled the cytoplasm of degenerating necrotic myofibers. In addition, both antibodies showed distinct endomysial capillary labeling in a subset of dermatomyositis. Areas with perifascicular atrophy often exhibited the most prominent vascular labeling for C4d and C5b-9. In conclusion, C4d and C5b-9 show similar expression patterns in muscle biopsies of patients with inflammatory myopathies and both highlight the presence of vascular labeling associated with dermatomyositis. C4d antibodies are widely used and may offer an alternative for C5b-9 staining.

  18. Synchrotron-based valence shell photoionization of CH radical.

    PubMed

    Gans, B; Holzmeier, F; Krüger, J; Falvo, C; Röder, A; Lopes, A; Garcia, G A; Fittschen, C; Loison, J-C; Alcaraz, C

    2016-05-28

    We report the first experimental observations of X(+) (1)Σ(+)←X (2)Π and a(+) (3)Π←X (2)Π single-photon ionization transitions of the CH radical performed on the DESIRS beamline at the SOLEIL synchrotron facility. The radical was produced by successive hydrogen-atom abstractions on methane by fluorine atoms in a continuous microwave discharge flow tube. Mass-selected ion yields and photoelectron spectra were recorded as a function of photon energy using a double imaging photoelectron/photoion coincidence spectrometer. The ion yield appears to be strongly affected by vibrational and electronic autoionizations, which allow the observation of high Rydberg states of the neutral species. The photoelectron spectra enable the first direct determinations of the adiabatic ionization potential and the energy of the first triplet state of the cation with respect to its singlet ground state. This work also brings valuable information on the complex electronic structure of the CH radical and its cation and adds new observations to complement our understanding of Rydberg states and autoionization processes. PMID:27250306

  19. Synchrotron-based valence shell photoionization of CH radical

    NASA Astrophysics Data System (ADS)

    Gans, B.; Holzmeier, F.; Krüger, J.; Falvo, C.; Röder, A.; Lopes, A.; Garcia, G. A.; Fittschen, C.; Loison, J.-C.; Alcaraz, C.

    2016-05-01

    We report the first experimental observations of X+ 1Σ+←X 2Π and a+ 3Π←X 2Π single-photon ionization transitions of the CH radical performed on the DESIRS beamline at the SOLEIL synchrotron facility. The radical was produced by successive hydrogen-atom abstractions on methane by fluorine atoms in a continuous microwave discharge flow tube. Mass-selected ion yields and photoelectron spectra were recorded as a function of photon energy using a double imaging photoelectron/photoion coincidence spectrometer. The ion yield appears to be strongly affected by vibrational and electronic autoionizations, which allow the observation of high Rydberg states of the neutral species. The photoelectron spectra enable the first direct determinations of the adiabatic ionization potential and the energy of the first triplet state of the cation with respect to its singlet ground state. This work also brings valuable information on the complex electronic structure of the CH radical and its cation and adds new observations to complement our understanding of Rydberg states and autoionization processes.

  20. Substitutional 4d and 5d impurities in graphene.

    PubMed

    Alonso-Lanza, Tomás; Ayuela, Andrés; Aguilera-Granja, Faustino

    2016-08-21

    We describe the structural and electronic properties of graphene doped with substitutional impurities of 4d and 5d transition metals. The adsorption energies and distances for 4d and 5d metals in graphene show similar trends for the later groups in the periodic table, which are also well-known characteristics of 3d elements. However, along earlier groups the 4d impurities in graphene show very similar adsorption energies, distances and magnetic moments to the 5d ones, which can be related to the influence of the 4d and 5d lanthanide contraction. Surprisingly, within the manganese group, the total magnetic moment of 3 μB for manganese is reduced to 1 μB for technetium and rhenium. We find that compared with 3d elements, the larger size of the 4d and 5d elements causes a high degree of hybridization with the neighbouring carbon atoms, reducing spin splitting in the d levels. It seems that the magnetic adjustment of graphene could be significantly different if 4d or 5d impurities are used instead of 3d impurities.

  1. Substitutional 4d and 5d impurities in graphene.

    PubMed

    Alonso-Lanza, Tomás; Ayuela, Andrés; Aguilera-Granja, Faustino

    2016-08-21

    We describe the structural and electronic properties of graphene doped with substitutional impurities of 4d and 5d transition metals. The adsorption energies and distances for 4d and 5d metals in graphene show similar trends for the later groups in the periodic table, which are also well-known characteristics of 3d elements. However, along earlier groups the 4d impurities in graphene show very similar adsorption energies, distances and magnetic moments to the 5d ones, which can be related to the influence of the 4d and 5d lanthanide contraction. Surprisingly, within the manganese group, the total magnetic moment of 3 μB for manganese is reduced to 1 μB for technetium and rhenium. We find that compared with 3d elements, the larger size of the 4d and 5d elements causes a high degree of hybridization with the neighbouring carbon atoms, reducing spin splitting in the d levels. It seems that the magnetic adjustment of graphene could be significantly different if 4d or 5d impurities are used instead of 3d impurities. PMID:27439363

  2. Photoionization research on atomic beams. 2: The photoionization cross section of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Comes, F. J.; Speier, F.; Elzer, A.

    1982-01-01

    An experiment to determine the absolute value of the photo-ionization cross section of atomic oxygen is described. The atoms are produced in an electrical discharge in oxygen gas with 1% hydrogen added. In order to prevent recombination a crossed beam technique is employed. The ions formed are detected by a time-of-flight mass spectrometer. The concentration of oxygen atoms in the beam is 57%. The measured photoionization cross section of atomic oxygen is compared with theoretical data. The results show the participation of autoionization processes in ionization. The cross section at the autoionizing levels detected is considerably higher than the absorption due to the unperturbed continuum. Except for wavelengths where autoionization occurs, the measured ionization cross section is in fair agreement with theory. This holds up to 550 A whereas for shorter wavelengths the theoretical values are much higher.

  3. Synchrotron photoionization measurements of combustion intermediates: the photoionization efficiency of HONO

    NASA Astrophysics Data System (ADS)

    Taatjes, Craig A.; Osborn, David L.; Cool, Terrill A.; Nakajima, Koichi

    2004-08-01

    The HONO radical has recently been observed by photoionization mass spectrometry in low-pressure hydrogen-oxygen flames doped with NO 2. The photoionization efficiency (PIE) spectrum has been measured between 10.83 and 11.63 eV. A Franck-Condon simulation using calculated geometries and force constants of the cation and neutral, and including the effects of Duschinsky rotation, is presented to describe the PIE as a function of photon energy. The simulated PIE is used as a fitting function to estimate the adiabatic ionization potential from the experimental data. The apparent ionization threshold of (10.97 ± 0.03) eV is in excellent agreement with calculated values and is consistent with published bracketing determinations of the proton affinity of NO 2.

  4. Energy levels in Ag-like (4d{sup 10}4f, 4d{sup 10}5l (l = 0-3)), Pd-like (4d{sup 9}4f [J = 1], 4d{sup 9}5p [J = 1], 4d{sup 9}5f [J = 1]), and Rh-like (4d{sup 9} [J = 5/2, 3/2]) ions with Z {<=} 86

    SciTech Connect

    Ivanova, E.P.

    2009-11-15

    Relativistic perturbation theory with a model potential is used for the calculation of energy levels of the states 4f{sub 5/2}, 4f{sub 7/2}, 5s{sub 1/2}, 5p{sub 1/2}, 5p{sub 3/2}, 5d{sub 3/2}, 5d{sub 5/2}, 5f{sub 5/2}, and 5f{sub 7/2} above the 1s{sup 2}2s{sup 2}2p{sup 6}3s{sup 2}3p{sup 6}3d{sup 10}4s{sup 2}4p{sup 6}4d{sup 10} core, with one vacancy 4d{sub 5/2}{sup 9}, 4d{sub 7/2}{sup 9} in the same core, in the silver and rhodium isoelectronic sequences with the maximum nuclear charge Z = 86. The method of extrapolation of the model potential parameter is applied to calculate one-electron and one-vacancy wavefunctions. The wavefunctions of Ag- and Rh-like ions were used to calculate the energies of resonance transitions to the ground state {sup 1}S{sub 0} in Pd-like ions. Good agreement between the theoretical and the experimental energies of the resonance transitions in Pd-like ions indicates the reliability of the results obtained.

  5. Shape resonances in the photoionization of CF4

    SciTech Connect

    Stephens, J. A.; Dill, Dan; Dehmer, Joseph L.

    1986-01-01

    Calculations of photoionization cross sections and photoelectron angular distributions have been performed for all occupied orbitals of CF4 using the multiple-scattering model. Results are compared with very recent experiments which employ synchrotron radiation to measure these quantities, namely the measurements of Truesdale e t a l. for the carbonK shell, and measurements of Carlson e t a l. and Novak e t a l. for the five outermost valence levels. The calculations predict intense shape resonances below 3 eV in continua of a1 and t2 final state symmetry. Qualitative agreement is attained on comparing much of the theory with experiment, notably the five outer valence levels, which serves to establish a one-electron picture of the photoionization dynamics of CF4.

  6. Evolution of plasmonic and hybrid photoionization properties of alkaline earth metallofullerenes with the increasing fullerene size

    NASA Astrophysics Data System (ADS)

    Patel, Aakash; Chakraborty, Himadri

    2013-05-01

    A theoretical study of the photoionization of endohedral fullerenes with a selection of fullerene molecules of increasing size and with confined alkaline earth atoms like Be and Mg is carried out. The fullerene ion cores, comprised of C4+ ions, are smudged into a continuous jellium charge distribution, while the delocalized cloud of carbon valence electrons plus the electrons of the encaged atom are treated in the Kohn-Sham local density approximation (LDA). Only the spherical geometry is considered. The photoionization spectra are calculated by the time-dependent LDA that includes essential electron correlations. A systematic evolution of the mixing of valence atomic levels with states of fullerene single-electron bands is found along the sequence. This hybridization as a function of the fullerene size is seen to primarily define the properties of the subshell-differential ionization spectra both in the low energy plasmonic as well as the high energy oscillatory regions. Supported by NSF and DOE.

  7. Disentangling Multichannel Photodissociation Dynamics in Acetone by Time-Resolved Photoelectron-Photoion Coincidence Spectroscopy.

    PubMed

    Maierhofer, Paul; Bainschab, Markus; Thaler, Bernhard; Heim, Pascal; Ernst, Wolfgang E; Koch, Markus

    2016-08-18

    For the investigation of photoinduced dynamics in molecules with time-resolved pump-probe photoionization spectroscopy, it is essential to obtain unequivocal information about the fragmentation behavior induced by the laser pulses. We present time-resolved photoelectron-photoion coincidence (PEPICO) experiments to investigate the excited-state dynamics of isolated acetone molecules triggered by two-photon (269 nm) excitation. In the complex situation of different relaxation pathways, we unambiguously identify three distinct pump-probe ionization channels. The high selectivity of PEPICO detection allows us to observe the fragmentation behavior and to follow the time evolution of each channel separately. For channels leading to fragment ions, we quantitatively obtain the fragment-to-parent branching ratio and are able to determine experimentally whether dissociation occurs in the neutral molecule or in the parent ion. These results highlight the importance of coincidence detection for the interpretation of time-resolved photochemical relaxation and dissociation studies if multiple pathways are present.

  8. VizieR Online Data Catalog: Photoionization cross sections of Selenium ions (Sterling+, 2011)

    NASA Astrophysics Data System (ADS)

    Sterling, N. C.; Witthoeft, M. C.

    2011-02-01

    'Direct' and 'Direct and resonant' photoionization cross sections are tabulated for neutral and the first five ions of Se. Note that photoexcitation-autoionization resonances are not included in these data files. Names of the files are given by pxd.dat (px.dat), e.g., se2+pxd.dat (se2+px.dat) for photoionization of Se2+ ions. Comments are indicated by '#' in the first column of a line. The first two lines of a file are header information indicating the number of photon targets (ground state and metastable states in the ground configuration, with 1 the lowest energy) and number of energies. The photoionization cross section of each state is preceded by a comment giving the energy above the ground state (or the total energy, in the case of the ground state), the total energy of the target state, and the energy-order of that state (1 = ground state, 2 = first excited state, etc.). All energies are reported in Rydbergs, and cross sections in megabarns (10-18cm2). Total and partial final state resolved dielectronic recombination rate coefficients are tabulated for the first six ions of Se, in the ADAS adf09 and adf48 formats. Names of the files are given by adf09.dat (adf48), e.g., adf09_se2+.dat (adf48_se2+.dat) gives dielectronic recombination data for Se2+ forming Se+. These files are available in adf subdirectory. The format of these files is complex, and beyond the scope of this README file. The reader is referred to http://amdpp.phys.strath.ac.uk/tamoc/RR/RR_web/appxa-09.pdf for a complete description of the adf09 and adf48 files format. (14 data files).

  9. Photoionization in negative streamers: Fast computations and two propagation modes

    SciTech Connect

    Luque, Alejandro; Ebert, Ute; Montijn, Carolynne; Hundsdorfer, Willem

    2007-02-19

    Streamer discharges play a central role in electric breakdown of matter in pulsed electric fields, both in nature and in technology. Reliable and fast computations of the minimal model for negative streamers in simple gases such as nitrogen have recently been developed. However, photoionization was not included; it is important in air and poses a major numerical challenge. The authors here introduce a fast and reliable method to include photoionization into our numerical scheme with adaptive grids, and they discuss its importance for negative streamers. In particular, they identify different propagation regimes where photoionization does or does not play a role.0.

  10. Photoionization-pumped, Ne II, x-ray laser studies project. Final report

    SciTech Connect

    Richardson, M.C.; Hagelstein, P.L.; Eckart, M.J.; Forsyth, J.M.; Gerrassimenko, M.; Soures, J.M.

    1984-01-01

    The energetics of this pumping scheme are shown. Short-pulse (50 to 100 ps) laser irradiation of an appropriate x-ray flashlamp medium generates broad-band emission in the range of 300 to 800 eV which preferentially photoionizes Ne to the /sup 2/S state of Ne II creating an inversion at approximately 27 eV. Although this approach does not depend on precise spectral overlap between the x-ray pump radiation and the medium to be pumped, it does require that the x-ray medium remain un-ionized prior to photoionization by the soft x-ray emission. Well-controlled focus conditions are required to ensure that the x-ray medium is not subjected to electron or x-ray preheat prior to irradiation by the soft x-ray source. The magnitude of the population inversion is predicted to be critically dependent upon rapid photoionization of the two states; therefore, ultra-short pulse irradiation of the laser flashlamps is required.

  11. Semaphorin 4D Promotes Skeletal Metastasis in Breast Cancer.

    PubMed

    Yang, Ying-Hua; Buhamrah, Asma; Schneider, Abraham; Lin, Yi-Ling; Zhou, Hua; Bugshan, Amr; Basile, John R

    2016-01-01

    Bone density is controlled by interactions between osteoclasts, which resorb bone, and osteoblasts, which deposit it. The semaphorins and their receptors, the plexins, originally shown to function in the immune system and to provide chemotactic cues for axon guidance, are now known to play a role in this process as well. Emerging data have identified Semaphorin 4D (Sema4D) as a product of osteoclasts acting through its receptor Plexin-B1 on osteoblasts to inhibit their function, tipping the balance of bone homeostasis in favor of resorption. Breast cancers and other epithelial malignancies overexpress Sema4D, so we theorized that tumor cells could be exploiting this pathway to establish lytic skeletal metastases. Here, we use measurements of osteoblast and osteoclast differentiation and function in vitro and a mouse model of skeletal metastasis to demonstrate that both soluble Sema4D and protein produced by the breast cancer cell line MDA-MB-231 inhibits differentiation of MC3T3 cells, an osteoblast cell line, and their ability to form mineralized tissues, while Sema4D-mediated induction of IL-8 and LIX/CXCL5, the murine homologue of IL-8, increases osteoclast numbers and activity. We also observe a decrease in the number of bone metastases in mice injected with MDA-MB-231 cells when Sema4D is silenced by RNA interference. These results are significant because treatments directed at suppression of skeletal metastases in bone-homing malignancies usually work by arresting bone remodeling, potentially leading to skeletal fragility, a significant problem in patient management. Targeting Sema4D in these cancers would not affect bone remodeling and therefore could elicit an improved therapeutic result without the debilitating side effects.

  12. Soil matrix and macropore biodegradation of 2,4-D

    SciTech Connect

    Pivetz, B.E.; Steenhuis, T.S.

    1995-07-01

    Preferential flow of pesticides in macropores can lead to decreased travel times through the vadose zone and increased groundwater contamination. Macropores, however, may present a favorable environment for biodegradation because of greater oxygen, nutrient, and substrate supply, and higher microbial populations in earthworm burrows, compared to the soil matrix. The biodegradation of 2,4-dichlorophenoxyacetic acid (2,4-D) was measured in macropores and soil matrix of packed soil columns (7.0-cm diam., 10-cm length) and undisturbed cores contained as well-defined artificial macropore and the undisturbed cores contained earthworm-burrow macropores. A 50 {mu}g/L 2,4-D solution was continuously applied to the unsaturated soil surface and breakthrough curves (BTCs) indicating pesticide loss in the effluent were obtained from the soil matrix and macropore flow paths. Biodegradation rates were calculated separately for each flow path by comparing the BTCs to BTCs representing abiotic conditions, and dividing the 2,4-D loss by the travel time through each flow path. The biodegradation rates increased with time in both flow paths, and the final biodegradation rate in the macropore region surpassed that of the matrix, presumably because of increased microbial populations in the macropore. Complete loss of the 2,4-D in both flow paths was observed after continuous application of 2,4-D for 400 h, with maximum column-averaged 2,4-D loss rates of 0.879 {mu}g/(L h) in the matrix and 1.073 {mu}g/(L h) in the macropore. Biodegradation of 2,4-D was also observed in the macropore and matrix regions of the undisturbed soil cores. 19 refs., 7 figs., 2 tabs.

  13. Semaphorin 4D Promotes Skeletal Metastasis in Breast Cancer

    PubMed Central

    Yang, Ying-Hua; Buhamrah, Asma; Schneider, Abraham; Lin, Yi-Ling; Zhou, Hua; Bugshan, Amr; Basile, John R.

    2016-01-01

    Bone density is controlled by interactions between osteoclasts, which resorb bone, and osteoblasts, which deposit it. The semaphorins and their receptors, the plexins, originally shown to function in the immune system and to provide chemotactic cues for axon guidance, are now known to play a role in this process as well. Emerging data have identified Semaphorin 4D (Sema4D) as a product of osteoclasts acting through its receptor Plexin-B1 on osteoblasts to inhibit their function, tipping the balance of bone homeostasis in favor of resorption. Breast cancers and other epithelial malignancies overexpress Sema4D, so we theorized that tumor cells could be exploiting this pathway to establish lytic skeletal metastases. Here, we use measurements of osteoblast and osteoclast differentiation and function in vitro and a mouse model of skeletal metastasis to demonstrate that both soluble Sema4D and protein produced by the breast cancer cell line MDA-MB-231 inhibits differentiation of MC3T3 cells, an osteoblast cell line, and their ability to form mineralized tissues, while Sema4D-mediated induction of IL-8 and LIX/CXCL5, the murine homologue of IL-8, increases osteoclast numbers and activity. We also observe a decrease in the number of bone metastases in mice injected with MDA-MB-231 cells when Sema4D is silenced by RNA interference. These results are significant because treatments directed at suppression of skeletal metastases in bone-homing malignancies usually work by arresting bone remodeling, potentially leading to skeletal fragility, a significant problem in patient management. Targeting Sema4D in these cancers would not affect bone remodeling and therefore could elicit an improved therapeutic result without the debilitating side effects. PMID:26910109

  14. Spectral Dependence of Nanocrystal Photoionization Probability: The Role of Hot-Carrier Transfer

    SciTech Connect

    Padilha, Lazaro A.; Robel, Istvan; Lee, Doh C.; Nagpal, Prashant; Pietryga, Jeffrey M.; Klimov, Victor I.

    2011-01-01

    We conduct measurements of photocharging of PbSe and PbS nanocrystal quantum dots (NQDs) as a function of excitation energy (ℏω). We observe a rapid growth of the degree of photocharging with increasing ℏω, which indicates an important role of hot-carrier transfer in the photoionization process. The corresponding spectral dependence exhibits two thresholds that mark the onsets of weak and strong photocharging. Interestingly, both thresholds are linked to the NQD band gap energy (Eg) and scale as ~1.5Eg and ~3Eg, indicating that the onsets of photoionization are associated with specific nanocrystal states (tentatively, 1P and 2P, respectively) and are not significantly dependent on the energy of external acceptor sites. For all samples, the hot-electron transfer probability increases by nearly 2 orders of magnitude as photon energy increases from 1.5 to 3.5 eV, although at any given wavelength the photoionization probability shows significant sample-to-sample variations (~10–6 to 10–3 for 1.5 eV and ~10–4 to 10–1 for 3.5 eV). In addition to the effect of the NQD size, these variations are likely due to differences in the properties of the NQD surface and/or the number and identity of external acceptor trap sites. The charge-separated states produced by photoionization are characterized by extremely long lifetimes (20 to 85 s) that become longer with increasing NQD size.

  15. Motion artifacts occurring at the lung/diaphragm interface using 4D CT attenuation correction of 4D PET scans.

    PubMed

    Killoran, Joseph H; Gerbaudo, Victor H; Mamede, Marcelo; Ionascu, Dan; Park, Sang-June; Berbeco, Ross

    2011-11-15

    For PET/CT, fast CT acquisition time can lead to errors in attenuation correction, particularly at the lung/diaphragm interface. Gated 4D PET can reduce motion artifacts, though residual artifacts may persist depending on the CT dataset used for attenuation correction. We performed phantom studies to evaluate 4D PET images of targets near a density interface using three different methods for attenuation correction: a single 3D CT (3D CTAC), an averaged 4D CT (CINE CTAC), and a fully phase matched 4D CT (4D CTAC). A phantom was designed with two density regions corresponding to diaphragm and lung. An 8 mL sphere phantom loaded with 18F-FDG was used to represent a lung tumor and background FDG included at an 8:1 ratio. Motion patterns of sin(x) and sin4(x) were used for dynamic studies. Image data was acquired using a GE Discovery DVCT-PET/CT scanner. Attenuation correction methods were compared based on normalized recovery coefficient (NRC), as well as a novel quantity "fixed activity volume" (FAV) introduced in our report. Image metrics were compared to those determined from a 3D PET scan with no motion present (3D STATIC). Values of FAV and NRC showed significant variation over the motion cycle when corrected by 3D CTAC images. 4D CTAC- and CINE CTAC-corrected PET images reduced these motion artifacts. The amount of artifact reduction is greater when the target is surrounded by lower density material and when motion was based on sin4(x). 4D CTAC reduced artifacts more than CINE CTAC for most scenarios. For a target surrounded by water equivalent material, there was no advantage to 4D CTAC over CINE CTAC when using the sin(x) motion pattern. Attenuation correction using both 4D CTAC or CINE CTAC can reduce motion artifacts in regions that include a tissue interface such as the lung/diaphragm border. 4D CTAC is more effective than CINE CTAC at reducing artifacts in some, but not all, scenarios.

  16. Stability and dissociation dynamics of N2++ ions following core ionization studied by an Auger-electron-photoion coincidence method

    NASA Astrophysics Data System (ADS)

    Iwayama, H.; Kaneyasu, T.; Hikosaka, Y.; Shigemasa, E.

    2016-07-01

    An Auger-electron-photoion coincidence (AEPICO) method has been applied to study the stability and dissociation dynamics of dicationic states after the N K-shell photoionization of nitrogen molecules. From time-of-flight and kinetic energy analyses of the product ions, we have obtained coincident Auger spectra associated with metastable states of N2++ ions and dissociative states leading to N2++ → N+ + N+ and N++ + N. To investigate the production of dissociative states, we present two-dimensional AEPICO maps which reveal the correlations between the binding energies of the Auger final states and the ion kinetic energy release. These correlations have been used to determine the dissociation limits of individual Auger final states.

  17. 4-D reconstruction for dynamic fluorescence diffuse optical tomography.

    PubMed

    Liu, Xin; Zhang, Bin; Luo, Jianwen; Bai, Jing

    2012-11-01

    Dynamic fluorescence diffuse optical tomography (FDOT) is important for the research of drug delivery, medical diagnosis and treatment. Conventionally, dynamic tomographic images are reconstructed frame by frame, independently. This approach fails to account for the temporal correlations in measurement data. Ideally, the entire image sequence should be considered as a whole and a four-dimensional (4-D) reconstruction should be performed. However, the fully 4-D reconstruction is computationally intensive. In this paper, we propose a new 4-D reconstruction approach for dynamic FDOT, which is achieved by applying a temporal Karhunen-Loève (KL) transformation to the imaging equation. By taking advantage of the decorrelation and compression properties of the KL transformation, the complex 4-D optical reconstruction problem is greatly simplified. To evaluate the performance of the method, simulation, phantom, and in vivo experiments (N=7) are performed on a hybrid FDOT/x-ray computed tomography imaging system. The experimental results indicate that the reconstruction images obtained by the KL method provide good reconstruction quality. Additionally, by discarding high-order KL components, the computation time involved with fully 4-D reconstruction can be greatly reduced in contrast to the conventional frame-by-frame reconstruction.

  18. New C4D Sensor with a Simulated Inductor

    PubMed Central

    Lyu, Yingchao; Ji, Haifeng; Yang, Shijie; Huang, Zhiyao; Wang, Baoliang; Li, Haiqing

    2016-01-01

    A new capacitively coupled contactless conductivity detection (C4D) sensor with an improved simulated inductor is developed in this work. The improved simulated inductor is designed on the basis of the Riordan-type floating simulated inductor. With the improved simulated inductor, the negative influence of the coupling capacitances is overcome and the conductivity measurement is implemented by the series resonance principle. The conductivity measurement experiments are carried out in three pipes with different inner diameters of 3.0 mm, 4.6 mm and 6.4 mm, respectively. The experimental results show that the designs of the new C4D sensor and the improved simulated inductor are successful. The maximum relative error of the conductivity measurement is less than 5%. Compared with the C4D sensors using practical inductors, the measurement accuracy of the new C4D sensor is comparable. The research results also indicate that the adjustability of a simulated inductor can reduce the requirement for the AC source and guarantee the interchangeableness. Meanwhile, it is recommended that making the potential of one terminal of a simulated inductor stable is beneficial to the running stability. Furthermore, this work indirectly verifies the possibility and feasibility of the miniaturization of the C4D sensor by using the simulated inductor technique and lays a good foundation for future research work. PMID:26828493

  19. Early events in radiation chemistry and in photoionization

    SciTech Connect

    Trifunac, A.D.; Loffredo, D.M.; Liu, A.-D.

    1992-01-01

    Real-time studies of aliphatic and aromatic hydrocarbons by pulse radiolysis and laser photoionization reveal the chemistry of the ionic species in the condensed phase. The occurrence of radical cation reactions with solvent molecules provides the core mechanism capable of explaining a wide range of observations in photoionization and radiation chemistry. The study of products and transients in photoionization of aromatic solutes in hydrocarbon and alcohol solvent illustrates several details of this high-energy'' chemistry. A reaction pathway involving ion-molecule reaction of excited ions is indicated for a series of polycyclic aromatic hydrocarbons photoionized using intense excimer laser (248 and 308 nm) pulses in hydrocarbon and alcohol solutions. We have found that condensed-phase ion-molecule reactions in radiolysis are ubiquitous and we speculate on their overall role in hydrocarbon radiolysis.

  20. Early events in radiation chemistry and in photoionization

    SciTech Connect

    Trifunac, A.D.; Loffredo, D.M.; Liu, A.-D.

    1992-12-31

    Real-time studies of aliphatic and aromatic hydrocarbons by pulse radiolysis and laser photoionization reveal the chemistry of the ionic species in the condensed phase. The occurrence of radical cation reactions with solvent molecules provides the core mechanism capable of explaining a wide range of observations in photoionization and radiation chemistry. The study of products and transients in photoionization of aromatic solutes in hydrocarbon and alcohol solvent illustrates several details of this ``high-energy`` chemistry. A reaction pathway involving ion-molecule reaction of excited ions is indicated for a series of polycyclic aromatic hydrocarbons photoionized using intense excimer laser (248 and 308 nm) pulses in hydrocarbon and alcohol solutions. We have found that condensed-phase ion-molecule reactions in radiolysis are ubiquitous and we speculate on their overall role in hydrocarbon radiolysis.

  1. A 4D Hyperspherical Interpretation of q-Space

    PubMed Central

    Hosseinbor, A. Pasha; Chung, Moo K.; Wu, Yu-Chien; Alexander, Andrew L.; Bendlin, Barbara B.

    2014-01-01

    3D q-space can be viewed as the surface of a 4D hypersphere. In this paper, we seek to develop a 4D hyperspherical interpretation of q-space by projecting it onto a hypersphere and subsequently modeling the q-space signal via 4D hyperspherical harmonics (HSH). Using this orthonormal basis, we analytically derive several quantitative indices and numerically estimate the diffusion ODF. Importantly, we derive the integral transform describing the relationship between the diffusion signal and propagator on a hypersphere. We also show that the HSH basis expends less fitting parameters than other well-established methods to achieve comparable signal and better ODF reconstructions. All in all, this work provides a new way of looking at q-space. PMID:24505799

  2. Molecular alignment dependent electron interference in attosecond ultraviolet photoionization

    PubMed Central

    Yuan, Kai-Jun; Bandrauk, André D.

    2015-01-01

    We present molecular photoionization processes by intense attosecond ultraviolet laser pulses from numerical solutions of time-dependent Schrödinger equations. Simulations preformed on a single electron diatomic H2+ show minima in molecular photoelectron energy spectra resulting from two center interference effects which depend strongly on molecular alignment. We attribute such sensitivity to the spatial orientation asymmetry of the photoionization process from the two nuclei. A similar influence on photoelectron kinetic energies is also presented. PMID:26798785

  3. Photoionization of noble-gas atoms by ultrashort electromagnetic pulses

    SciTech Connect

    Astapenko, V. A. Svita, S. Yu.

    2014-11-15

    The photoionization of atoms of noble gases (Ar, Kr, and Xe) by ultrashort electromagnetic pulses of a corrected Gaussian shape is studied theoretically. Computations are performed in the context of perturbation theory using a simple expression for the total probability of photoionization of an atom by electromagnetic pulses. The features of this process are revealed and analyzed for various ranges of the parameters of the problem.

  4. Single and double photoionization of Be and Mg

    NASA Astrophysics Data System (ADS)

    Pindzola, M. S.; Ballance, C. P.; Abdel-Naby, Sh A.; Robicheaux, F.; Armstrong, G. S. J.; Colgan, J.

    2013-02-01

    A new version of the time-dependent close-coupling method is used to calculate the single and double photoionization of the Be and Mg atoms. Total cross sections are calculated using an implicit time propagator with a core orthogonalization method on a variable radial mesh. The double to single photoionization cross section ratios are found to be in good agreement with experiment for both Be and Mg.

  5. Effect of strongly coupled plasma on photoionization cross section

    NASA Astrophysics Data System (ADS)

    Das, Madhusmita

    2014-01-01

    The effect of strongly coupled plasma on the ground state photoionization cross section is studied. In the non relativistic dipole approximation, cross section is evaluated from bound-free transition matrix element. The bound and free state wave functions are obtained by solving the radial Schrodinger equation with appropriate plasma potential. We have used ion sphere potential (ISP) to incorporate the plasma effects in atomic structure calculation. This potential includes the effect of static plasma screening on nuclear charge as well as the effect of confinement due to the neighbouring ions. With ISP, the radial equation is solved using Shooting method approach for hydrogen like ions (Li+2, C+5, Al+12) and lithium like ions (C+3, O+5). The effect of strong screening and confinement is manifested as confinement resonances near the ionization threshold for both kinds of ions. The confinement resonances are very much dependent on the edge of the confining potential and die out as the plasma density is increased. Plasma effect also results in appearance of Cooper minimum in lithium like ions, which was not present in case of free lithium like ions. With increasing density the position of Cooper minimum shifts towards higher photoelectron energy. The same behaviour is also true for weakly coupled plasma where plasma effect is modelled by Debye-Huckel potential.

  6. Effect of strongly coupled plasma on photoionization cross section

    SciTech Connect

    Das, Madhusmita

    2014-01-15

    The effect of strongly coupled plasma on the ground state photoionization cross section is studied. In the non relativistic dipole approximation, cross section is evaluated from bound-free transition matrix element. The bound and free state wave functions are obtained by solving the radial Schrodinger equation with appropriate plasma potential. We have used ion sphere potential (ISP) to incorporate the plasma effects in atomic structure calculation. This potential includes the effect of static plasma screening on nuclear charge as well as the effect of confinement due to the neighbouring ions. With ISP, the radial equation is solved using Shooting method approach for hydrogen like ions (Li{sup +2}, C{sup +5}, Al{sup +12}) and lithium like ions (C{sup +3}, O{sup +5}). The effect of strong screening and confinement is manifested as confinement resonances near the ionization threshold for both kinds of ions. The confinement resonances are very much dependent on the edge of the confining potential and die out as the plasma density is increased. Plasma effect also results in appearance of Cooper minimum in lithium like ions, which was not present in case of free lithium like ions. With increasing density the position of Cooper minimum shifts towards higher photoelectron energy. The same behaviour is also true for weakly coupled plasma where plasma effect is modelled by Debye-Huckel potential.

  7. Emerging Applications of Abdominal 4D Flow MRI

    PubMed Central

    Roldán-Alzate, Alejandro; Francois, Christopher J.; Wieben, Oliver; Reeder, Scott B.

    2016-01-01

    OBJECTIVE Comprehensive assessment of abdominal hemodynamics is crucial for many clinical diagnoses but is challenged by a tremendous complexity of anatomy, normal physiology, and a wide variety of pathologic abnormalities. This article introduces 4D flow MRI as a powerful technique for noninvasive assessment of the hemodynamics of abdominal vascular territories. CONCLUSION Four-dimensional flow MRI provides clinicians with a more extensive and straightforward approach to evaluate disorders that affect blood flow in the abdomen. This review presents a series of clinical cases to illustrate the utility of 4D flow MRI in the comprehensive assessment of the abdominal circulation. PMID:27187681

  8. 4D imaging of protein aggregation in live cells.

    PubMed

    Spokoini, Rachel; Shamir, Maya; Keness, Alma; Kaganovich, Daniel

    2013-01-01

    ubiquitinated are diverted to the IPOD, where they are actively aggregated in a protective compartment. Up until this point, the methodological paradigm of live-cell fluorescence microscopy has largely been to label proteins and track their locations in the cell at specific time-points and usually in two dimensions. As new technologies have begun to grant experimenters unprecedented access to the submicron scale in living cells, the dynamic architecture of the cytosol has come into view as a challenging new frontier for experimental characterization. We present a method for rapidly monitoring the 3D spatial distributions of multiple fluorescently labeled proteins in the yeast cytosol over time. 3D timelapse (4D imaging) is not merely a technical challenge; rather, it also facilitates a dramatic shift in the conceptual framework used to analyze cellular structure. We utilize a cytosolic folding sensor protein in live yeast to visualize distinct fates for misfolded proteins in cellular aggregation quality control, using rapid 4D fluorescent imaging. The temperature sensitive mutant of the Ubc9 protein (Ubc9(ts)) is extremely effective both as a sensor of cellular proteostasis, and a physiological model for tracking aggregation quality control. As with most ts proteins, Ubc9(ts) is fully folded and functional at permissive temperatures due to active cellular chaperones. Above 30 ° C, or when the cell faces misfolding stress, Ubc9(ts) misfolds and follows the fate of a native globular protein that has been misfolded due to mutation, heat denaturation, or oxidative damage. By fusing it to GFP or other fluorophores, it can be tracked in 3D as it forms Stress Foci, or is directed to JUNQ or IPOD. PMID:23608881

  9. Configuration-interaction relativistic-many-body-perturbation-theory calculations of photoionization cross sections from quasicontinuum oscillator strengths

    SciTech Connect

    Savukov, I. M.; Filin, D. V.

    2014-12-29

    Many applications are in need of accurate photoionization cross sections, especially in the case of complex atoms. Configuration-interaction relativistic-many-body-perturbation theory (CI-RMBPT) has been successful in predicting atomic energies, matrix elements between discrete states, and other properties, which is quite promising, but it has not been applied to photoionization problems owing to extra complications arising from continuum states. In this paper a method that will allow the conversion of discrete CI-(R)MPBT oscillator strengths (OS) to photoionization cross sections with minimal modifications of the codes is introduced and CI-RMBPT cross sections of Ne, Ar, Kr, and Xe are calculated. A consistent agreement with experiment is found. RMBPT corrections are particularly significant for Ar, Kr, and Xe and improve agreement with experimental results compared to the particle-hole CI method. As a result, the demonstrated conversion method can be applied to CI-RMBPT photoionization calculations for a large number of multivalence atoms and ions.

  10. Configuration-interaction relativistic-many-body-perturbation-theory calculations of photoionization cross sections from quasicontinuum oscillator strengths

    DOE PAGES

    Savukov, I. M.; Filin, D. V.

    2014-12-29

    Many applications are in need of accurate photoionization cross sections, especially in the case of complex atoms. Configuration-interaction relativistic-many-body-perturbation theory (CI-RMBPT) has been successful in predicting atomic energies, matrix elements between discrete states, and other properties, which is quite promising, but it has not been applied to photoionization problems owing to extra complications arising from continuum states. In this paper a method that will allow the conversion of discrete CI-(R)MPBT oscillator strengths (OS) to photoionization cross sections with minimal modifications of the codes is introduced and CI-RMBPT cross sections of Ne, Ar, Kr, and Xe are calculated. A consistent agreementmore » with experiment is found. RMBPT corrections are particularly significant for Ar, Kr, and Xe and improve agreement with experimental results compared to the particle-hole CI method. As a result, the demonstrated conversion method can be applied to CI-RMBPT photoionization calculations for a large number of multivalence atoms and ions.« less

  11. High-resolution soft x-ray photoionization studies of selected molecules

    SciTech Connect

    Hudson, E.A.

    1993-08-01

    Near-edge soft x-ray photoionization spectra were measured for CO, SF{sub 6}, H{sub 2}S, and D{sub 2}S in the gas phase, using the Free University of Berlin plane-grating SX-700-II monochromator at the synchrotron radiation source BESSY. Photoionization spectra of carbon monoxide were measured near the carbon and oxygen K edges. Vibrational spacings and bond lengths are derived for several resonances. Results are consistent with equivalent-core model and indicate the different influences of the carbon and oxygen Is core holes. Corresponding spectra of H{sub 2}CO and D{sub 2}CO were also measured. Assignment of complex vibrational structure in valence-shell and Rydberg resonances is facilitated by comparison of spectra for the two isotopic species. Geometric and vibrational parameters are derived for several carbon 1s core-excited states. Isotopic shifts are observed in the energies and linewidths of some core-excited states. Sulfur hexafluoride photoionization spectra, measured near the sulfur L{sub 2,3} edges, show several series of weak, narrow Rydberg resonances. High resolution and good counting statistics allow a complete assignment of these states. Lineshapes of the broad inner-well resonances are analyzed to establish the magnitudes of vibrational and lifetime broadening in these states. Spectra of the H{sub 2}S and D{sub 2}S molecules were also measured near the sulfur L{sub 2,3} edges. Besides lower-energy transitions to inner-well states, a complex manifold of overlapping Rydberg resonances is observed. The rich fine structure of these states arises mainly from removal of orbital degeneracies in molecular field. Additional structure due to vibrational excitations in the final state is identified by comparison of the spectra for the two isotopic species.

  12. Impact of Petrophysical Experiments on Quantitative Interpretation of 4D Seismic Data at Ketzin, Germany

    NASA Astrophysics Data System (ADS)

    Ivanova, A.; Lueth, S.

    2015-12-01

    Petrophysical investigations for CCS concern relationships between physical properties of rocks and geophysical observations for understanding behavior of injected CO2 in a geological formation. In turn 4D seismic surveying is a proven tool for CO2 monitoring. At the Ketzin pilot site (Germany) 4D seismic data have been acquired by means of a baseline (pre-injection) survey in 2005 and monitor surveys in 2009 and 2012. At Ketzin CO2 was injected in supercritical state from 2008 to 2013 in a sandstone saline aquifer (Stuttgart Formation) at a depth of about 650 m. The 4D seismic data from Ketzin reflected a pronounced effect of this injection. Seismic forward modeling using results of petrophysical experiments on two core samples fromthe target reservoir confirmed that effects of the injected CO2 on the 4D seismic data are significant. The petrophysical data were used in that modeling in order to reflect changes due to the CO2 injection in acoustic parameters of the reservoir. These petrophysical data were further used for a successful quantitative interpretation of the 4D seismic data at Ketzin. Now logs from a well (drilled in 2012) penetrating the reservoir containing information about changes in the acoustic parameters of the reservoir due to the CO2 injection are available. These logs were used to estimate impact of the petrophysical data on the qualitative and quantitative interpretation of the 4D seismic data at Ketzin. New synthetic seismograms were computed using the same software and the same wavelet as the old ones apart from the only difference and namely the changes in the input acoustic parameters would not be affected with any petrophysical experiments anymore. Now these changes were put in computing directly from the logs. In turn the new modelled changes due to the injection in the newly computed seismograms do not include any effects of the petrophysical data anymore. Key steps of the quantitative and qualitative interpretation of the 4D seismic

  13. 2,4-Dichlorophenoxyacetic acid (2,4-D)

    Integrated Risk Information System (IRIS)

    2,4 - Dichlorophenoxyacetic acid ( 2,4 - D ) ; CASRN 94 - 75 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Asses

  14. Enterococcus faecalis promotes osteoclastogenesis and semaphorin 4D expression.

    PubMed

    Wang, Shuai; Deng, Zuhui; Seneviratne, Chaminda J; Cheung, Gary S P; Jin, Lijian; Zhao, Baohong; Zhang, Chengfei

    2015-10-01

    Enterococcus faecalis is considered a major bacterial pathogen implicated in endodontic infections and contributes considerably to periapical periodontitis. This study aimed to investigate the potential mechanisms by which E. faecalis accounts for the bone destruction in periapical periodontitis in vitro. Osteoclast precursor RAW264.7 cells were treated with E. faecalis ATCC 29212 and a wild strain of E. faecalis derived clinically from an infected root canal. The results showed that, to some extent, E. faecalis induced the RAW264.7 cells to form tartrate-resistant acid phosphatase (TRAP)-positive multinucleated osteoclast-like cells. This pathogen markedly stimulated RAW264.7 cells to express semaphorin 4D (Sema4D), which inhibits bone formation. Once RAW264.7 cells were primed by low-dose receptor activator of nuclear factor-kappa B ligand (RANKL), E. faecalis could significantly increase the production of TRAP-positive multinucleated cells and up-regulate the expression of osteoclast-specific markers, including NFATc1, TRAP and cathepsin K. Both p38 and ERK1/2 MAPK signaling pathways were activated by E. faecalis in RANKL-primed RAW264.7 cells, and meanwhile the expression of Sema4D was highly increased. In conclusion, E. faecalis may greatly contribute to the bone resorption in periapical periodontitis by promoting RANKL-dependent osteoclastogenesis and expression of Sema4D through activation of p38 and ERK1/2 MAPK signaling pathways.

  15. 4D flow mri post-processing strategies for neuropathologies

    NASA Astrophysics Data System (ADS)

    Schrauben, Eric Mathew

    4D flow MRI allows for the measurement of a dynamic 3D velocity vector field. Blood flow velocities in large vascular territories can be qualitatively visualized with the added benefit of quantitative probing. Within cranial pathologies theorized to have vascular-based contributions or effects, 4D flow MRI provides a unique platform for comprehensive assessment of hemodynamic parameters. Targeted blood flow derived measurements, such as flow rate, pulsatility, retrograde flow, or wall shear stress may provide insight into the onset or characterization of more complex neuropathologies. Therefore, the thorough assessment of each parameter within the context of a given disease has important medical implications. Not surprisingly, the last decade has seen rapid growth in the use of 4D flow MRI. Data acquisition sequences are available to researchers on all major scanner platforms. However, the use has been limited mostly to small research trials. One major reason that has hindered the more widespread use and application in larger clinical trials is the complexity of the post-processing tasks and the lack of adequate tools for these tasks. Post-processing of 4D flow MRI must be semi-automated, fast, user-independent, robust, and reliably consistent for use in a clinical setting, within large patient studies, or across a multicenter trial. Development of proper post-processing methods coupled with systematic investigation in normal and patient populations pushes 4D flow MRI closer to clinical realization while elucidating potential underlying neuropathological origins. Within this framework, the work in this thesis assesses venous flow reproducibility and internal consistency in a healthy population. A preliminary analysis of venous flow parameters in healthy controls and multiple sclerosis patients is performed in a large study employing 4D flow MRI. These studies are performed in the context of the chronic cerebrospinal venous insufficiency hypothesis. Additionally, a

  16. Absolute photoionization cross-section of the methyl radical.

    SciTech Connect

    Taatjes, C. A.; Osborn, D. L.; Selby, T.; Meloni, G.; Fan, H.; Pratt, S. T.; Chemical Sciences and Engineering Division; SNL

    2008-01-01

    The absolute photoionization cross-section of the methyl radical has been measured using two completely independent methods. The CH{sub 3} photoionization cross-section was determined relative to that of acetone and methyl vinyl ketone at photon energies of 10.2 and 11.0 eV by using a pulsed laser-photolysis/time-resolved synchrotron photoionization mass spectrometry method. The time-resolved depletion of the acetone or methyl vinyl ketone precursor and the production of methyl radicals following 193 nm photolysis are monitored simultaneously by using time-resolved synchrotron photoionization mass spectrometry. Comparison of the initial methyl signal with the decrease in precursor signal, in combination with previously measured absolute photoionization cross-sections of the precursors, yields the absolute photoionization cross-section of the methyl radical; {sigma}{sub CH}(10.2 eV) = (5.7 {+-} 0.9) x 10{sup -18} cm{sup 2} and {sigma}{sub CH{sub 3}}(11.0 eV) = (6.0 {+-} 2.0) x 10{sup -18} cm{sup 2}. The photoionization cross-section for vinyl radical determined by photolysis of methyl vinyl ketone is in good agreement with previous measurements. The methyl radical photoionization cross-section was also independently measured relative to that of the iodine atom by comparison of ionization signals from CH{sub 3} and I fragments following 266 nm photolysis of methyl iodide in a molecular-beam ion-imaging apparatus. These measurements gave a cross-section of (5.4 {+-} 2.0) x 10{sup -18} cm{sup 2} at 10.460 eV, (5.5 {+-} 2.0) x 10{sup -18} cm{sup 2} at 10.466 eV, and (4.9 {+-} 2.0) x 10{sup -18} cm{sup 2} at 10.471 eV. The measurements allow relative photoionization efficiency spectra of methyl radical to be placed on an absolute scale and will facilitate quantitative measurements of methyl concentrations by photoionization mass spectrometry.

  17. 4D MR imaging using robust internal respiratory signal

    NASA Astrophysics Data System (ADS)

    Hui, CheukKai; Wen, Zhifei; Stemkens, Bjorn; Tijssen, R. H. N.; van den Berg, C. A. T.; Hwang, Ken-Pin; Beddar, Sam

    2016-05-01

    The purpose of this study is to investigate the feasibility of using internal respiratory (IR) surrogates to sort four-dimensional (4D) magnetic resonance (MR) images. The 4D MR images were constructed by acquiring fast 2D cine MR images sequentially, with each slice scanned for more than one breathing cycle. The 4D volume was then sorted retrospectively using the IR signal. In this study, we propose to use multiple low-frequency components in the Fourier space as well as the anterior body boundary as potential IR surrogates. From these potential IR surrogates, we used a clustering algorithm to identify those that best represented the respiratory pattern to derive the IR signal. A study with healthy volunteers was performed to assess the feasibility of the proposed IR signal. We compared this proposed IR signal with the respiratory signal obtained using respiratory bellows. Overall, 99% of the IR signals matched the bellows signals. The average difference between the end inspiration times in the IR signal and bellows signal was 0.18 s in this cohort of matching signals. For the acquired images corresponding to the other 1% of non-matching signal pairs, the respiratory motion shown in the images was coherent with the respiratory phases determined by the IR signal, but not the bellows signal. This suggested that the IR signal determined by the proposed method could potentially correct the faulty bellows signal. The sorted 4D images showed minimal mismatched artefacts and potential clinical applicability. The proposed IR signal therefore provides a feasible alternative to effectively sort MR images in 4D.

  18. 4d → 4f resonance in photoabsorption of cerium ion Ce3+ and endohedral cerium in fullerene complex {\\rm{Ce}}@{{{\\rm{C}}}_{82}}^{+}

    NASA Astrophysics Data System (ADS)

    Schrange-Kashenock, G.

    2016-09-01

    The theoretical investigation of the single-photoionization spectra in the 4d-resonance region (120-150 eV) for the ionic cerium Ce3+ and cerium in the endohedral complex {{Ce}}@{{{{C}}}82}+ (in practice, {{{Ce}}}3+@{{{{C}}}82}2-) is presented. The fullerene cage is modeled by ab initio spherical jellium shell with an accurate account for the real distribution of carbon electron density. The oscillator strengths are calculated within the multiconfiguration Dirac-Fock (MCDF) approach for phototransitions from the outermost shells of the ion Ce3+ with and without the influence of the potential generated by a fullerene cage. It is shown that the integrated oscillator strengths have the main contribution from the Ce3+ 4d → 4f (ten possible from the phototransitions {}2F{7/2,5/2}\\to {}2D{3/2,5/2},{}2F{5/2,7/2},{}2G{5/2,7/2}) resonance photoexcitations. The corresponding precise MCDF values for the oscillator strengths and the transition energies are presented for the first time. It is demonstrated that the resonance {f}4d\\to 4f oscillator strengths are slightly affected by the presence of the cage potential, despite the fact that the spectral levels structure is changed when the effect of this potential is included. The Auger 4d -1 decay from the cerium free ion Ce3+ and the encapsulated endohedral ion Ce3+@ are considered within the two-step model and the corresponding Lorentzian profiles are presented. This model clearly reveals the correspondence of the complex resonance profile in the Ce3+ photoabsorption to the fine structure of ion energy levels. The smoothing of the resonance profile in the photoabsorption of the endohedral system {{Ce}}@{{{{C}}}82}+ compared with the free ion Ce3+ is attributed to increasing the linewidths of the Auger transitions. This increase is estimated from the relevant experiment (Müller et al 2008 Phys. Rev. Lett. 101 133001) to be strong; as at least three times the value for an isolated ion. The presence of the confining fullerene

  19. 4d → 4f resonance in photoabsorption of cerium ion Ce3+ and endohedral cerium in fullerene complex {\\rm{Ce}}@{{{\\rm{C}}}_{82}}^{+}

    NASA Astrophysics Data System (ADS)

    Schrange-Kashenock, G.

    2016-09-01

    The theoretical investigation of the single-photoionization spectra in the 4d-resonance region (120–150 eV) for the ionic cerium Ce3+ and cerium in the endohedral complex {{Ce}}@{{{{C}}}82}+ (in practice, {{{Ce}}}3+@{{{{C}}}82}2-) is presented. The fullerene cage is modeled by ab initio spherical jellium shell with an accurate account for the real distribution of carbon electron density. The oscillator strengths are calculated within the multiconfiguration Dirac–Fock (MCDF) approach for phototransitions from the outermost shells of the ion Ce3+ with and without the influence of the potential generated by a fullerene cage. It is shown that the integrated oscillator strengths have the main contribution from the Ce3+ 4d → 4f (ten possible from the phototransitions {}2F{7/2,5/2}\\to {}2D{3/2,5/2},{}2F{5/2,7/2},{}2G{5/2,7/2}) resonance photoexcitations. The corresponding precise MCDF values for the oscillator strengths and the transition energies are presented for the first time. It is demonstrated that the resonance {f}4d\\to 4f oscillator strengths are slightly affected by the presence of the cage potential, despite the fact that the spectral levels structure is changed when the effect of this potential is included. The Auger 4d ‑1 decay from the cerium free ion Ce3+ and the encapsulated endohedral ion Ce3+@ are considered within the two-step model and the corresponding Lorentzian profiles are presented. This model clearly reveals the correspondence of the complex resonance profile in the Ce3+ photoabsorption to the fine structure of ion energy levels. The smoothing of the resonance profile in the photoabsorption of the endohedral system {{Ce}}@{{{{C}}}82}+ compared with the free ion Ce3+ is attributed to increasing the linewidths of the Auger transitions. This increase is estimated from the relevant experiment (Müller et al 2008 Phys. Rev. Lett. 101 133001) to be strong; as at least three times the value for an isolated ion. The presence of the confining

  20. Radiative recombination and photoionization cross sections for heavy element impurities in plasmas: II. Ions of Si, Cl, Ar, Ti, Cr, Kr, and Xe

    SciTech Connect

    Trzhaskovskaya, M.B. Nikulin, V.K.; Clark, R.E.H.

    2009-11-15

    Total cross sections for radiative recombination with an electron for 36 ions of Si, Cl, Ar, Ti, Cr, Kr, and Xe as well as subshell photoionization cross sections are presented. The electron kinetic energy is {<=}50 keV. The calculations were performed using the relativistic Dirac-Fock method and the results have been included in a database of radiative recombination and photoionization cross sections for the heavy element impurity ions occurring in plasmas. The data are required for modelling fusion and astrophysical plasmas. To obtain the total radiative recombination cross section, calculations have been carried out for ground and all excited electron states up to states with the principal quantum number n = 20. The subshell photoionization cross sections for all states with n {<=} 12 and orbital momenta l {<=} 6 have been fitted by an analytical expression with five fit parameters which are tabulated.

  1. Intergalactic magnetogenesis at Cosmic Dawn by photoionization

    NASA Astrophysics Data System (ADS)

    Durrive, J.-B.; Langer, M.

    2015-10-01

    We present a detailed analysis of an astrophysical mechanism that generates cosmological magnetic fields during the Epoch of Reionization. It is based on the photoionization of the intergalactic medium by the first sources formed in the Universe. First the induction equation is derived, then the characteristic length and time-scales of the mechanism are identified, and finally numerical applications are carried out for first stars, primordial galaxies and distant powerful quasars. In these simple examples, the strength of the generated magnetic fields varies between the order of 10-23 G on hundreds of kiloparsecs and 10-19 G on hundreds of parsecs in the neutral intergalactic medium between the Strömgren spheres of the sources. Thus, this mechanism contributes to the premagnetization of the whole Universe before large-scale structures are in place. It operates with any ionizing source, at any time during the Epoch of Reionization. Finally, the generated fields possess a characteristic spatial configuration which may help discriminate these seeds from those produced by different mechanisms.

  2. Vacuum ultraviolet photoionization of carbohydrates and nucleotides.

    PubMed

    Shin, Joong-Won; Bernstein, Elliot R

    2014-01-28

    Carbohydrates (2-deoxyribose, ribose, and xylose) and nucleotides (adenosine-, cytidine-, guanosine-, and uridine-5(')-monophosphate) are generated in the gas phase, and ionized with vacuum ultraviolet photons (VUV, 118.2 nm). The observed time of flight mass spectra of the carbohydrate fragmentation are similar to those observed [J.-W. Shin, F. Dong, M. Grisham, J. J. Rocca, and E. R. Bernstein, Chem. Phys. Lett. 506, 161 (2011)] for 46.9 nm photon ionization, but with more intensity in higher mass fragment ions. The tendency of carbohydrate ions to fragment extensively following ionization seemingly suggests that nucleic acids might undergo radiation damage as a result of carbohydrate, rather than nucleobase fragmentation. VUV photoionization of nucleotides (monophosphate-carbohydrate-nucleobase), however, shows that the carbohydrate-nucleobase bond is the primary fragmentation site for these species. Density functional theory (DFT) calculations indicate that the removed carbohydrate electrons by the 118.2 nm photons are associated with endocyclic C-C and C-O ring centered orbitals: loss of electron density in the ring bonds of the nascent ion can thus account for the observed fragmentation patterns following carbohydrate ionization. DFT calculations also indicate that electrons removed from nucleotides under these same conditions are associated with orbitals involved with the nucleobase-saccharide linkage electron density. The calculations give a general mechanism and explanation of the experimental results. PMID:25669546

  3. Vacuum ultraviolet photoionization of carbohydrates and nucleotides

    SciTech Connect

    Shin, Joong-Won; Bernstein, Elliot R.

    2014-01-28

    Carbohydrates (2-deoxyribose, ribose, and xylose) and nucleotides (adenosine-, cytidine-, guanosine-, and uridine-5{sup ′}-monophosphate) are generated in the gas phase, and ionized with vacuum ultraviolet photons (VUV, 118.2 nm). The observed time of flight mass spectra of the carbohydrate fragmentation are similar to those observed [J.-W. Shin, F. Dong, M. Grisham, J. J. Rocca, and E. R. Bernstein, Chem. Phys. Lett. 506, 161 (2011)] for 46.9 nm photon ionization, but with more intensity in higher mass fragment ions. The tendency of carbohydrate ions to fragment extensively following ionization seemingly suggests that nucleic acids might undergo radiation damage as a result of carbohydrate, rather than nucleobase fragmentation. VUV photoionization of nucleotides (monophosphate-carbohydrate-nucleobase), however, shows that the carbohydrate-nucleobase bond is the primary fragmentation site for these species. Density functional theory (DFT) calculations indicate that the removed carbohydrate electrons by the 118.2 nm photons are associated with endocyclic C–C and C–O ring centered orbitals: loss of electron density in the ring bonds of the nascent ion can thus account for the observed fragmentation patterns following carbohydrate ionization. DFT calculations also indicate that electrons removed from nucleotides under these same conditions are associated with orbitals involved with the nucleobase-saccharide linkage electron density. The calculations give a general mechanism and explanation of the experimental results.

  4. Vacuum ultraviolet photoionization of carbohydrates and nucleotides.

    PubMed

    Shin, Joong-Won; Bernstein, Elliot R

    2014-01-28

    Carbohydrates (2-deoxyribose, ribose, and xylose) and nucleotides (adenosine-, cytidine-, guanosine-, and uridine-5(')-monophosphate) are generated in the gas phase, and ionized with vacuum ultraviolet photons (VUV, 118.2 nm). The observed time of flight mass spectra of the carbohydrate fragmentation are similar to those observed [J.-W. Shin, F. Dong, M. Grisham, J. J. Rocca, and E. R. Bernstein, Chem. Phys. Lett. 506, 161 (2011)] for 46.9 nm photon ionization, but with more intensity in higher mass fragment ions. The tendency of carbohydrate ions to fragment extensively following ionization seemingly suggests that nucleic acids might undergo radiation damage as a result of carbohydrate, rather than nucleobase fragmentation. VUV photoionization of nucleotides (monophosphate-carbohydrate-nucleobase), however, shows that the carbohydrate-nucleobase bond is the primary fragmentation site for these species. Density functional theory (DFT) calculations indicate that the removed carbohydrate electrons by the 118.2 nm photons are associated with endocyclic C-C and C-O ring centered orbitals: loss of electron density in the ring bonds of the nascent ion can thus account for the observed fragmentation patterns following carbohydrate ionization. DFT calculations also indicate that electrons removed from nucleotides under these same conditions are associated with orbitals involved with the nucleobase-saccharide linkage electron density. The calculations give a general mechanism and explanation of the experimental results.

  5. Vacuum ultraviolet photoionization of carbohydrates and nucleotides

    NASA Astrophysics Data System (ADS)

    Shin, Joong-Won; Bernstein, Elliot R.

    2014-01-01

    Carbohydrates (2-deoxyribose, ribose, and xylose) and nucleotides (adenosine-, cytidine-, guanosine-, and uridine-5'-monophosphate) are generated in the gas phase, and ionized with vacuum ultraviolet photons (VUV, 118.2 nm). The observed time of flight mass spectra of the carbohydrate fragmentation are similar to those observed [J.-W. Shin, F. Dong, M. Grisham, J. J. Rocca, and E. R. Bernstein, Chem. Phys. Lett. 506, 161 (2011)] for 46.9 nm photon ionization, but with more intensity in higher mass fragment ions. The tendency of carbohydrate ions to fragment extensively following ionization seemingly suggests that nucleic acids might undergo radiation damage as a result of carbohydrate, rather than nucleobase fragmentation. VUV photoionization of nucleotides (monophosphate-carbohydrate-nucleobase), however, shows that the carbohydrate-nucleobase bond is the primary fragmentation site for these species. Density functional theory (DFT) calculations indicate that the removed carbohydrate electrons by the 118.2 nm photons are associated with endocyclic C-C and C-O ring centered orbitals: loss of electron density in the ring bonds of the nascent ion can thus account for the observed fragmentation patterns following carbohydrate ionization. DFT calculations also indicate that electrons removed from nucleotides under these same conditions are associated with orbitals involved with the nucleobase-saccharide linkage electron density. The calculations give a general mechanism and explanation of the experimental results.

  6. Extreme ultraviolet-induced photoionized plasmas

    NASA Astrophysics Data System (ADS)

    Bartnik, Andrzej; Wachulak, Przemyslaw; Fiedorowicz, Henryk; Fok, Tomasz; Jarocki, Roman; Szczurek, Miroslaw

    2014-05-01

    In this work photoionized plasmas were created by irradiation of He or Ne gases with a focused extreme ultraviolet (EUV) beam from one of two laser-plasma sources employing Nd:YAG laser systems. The first of them was a 10 Hz laser-plasma EUV source, based on a double-stream gas-puff target, irradiated with a 3 ns per 0.8 J laser pulse. EUV radiation in this case was focused using a gold-plated grazing incidence ellipsoidal collector. The second source was based on a 10 ns per 10 J per 10 Hz laser system. In this case EUV radiation was focused using a gold-plated grazing incidence multifoil collector. Gases were injected into the interaction region, perpendicularly to an optical axis of the irradiation system, using an auxiliary gas puff valve. Spectral measurements in the EUV range were performed. In all cases the most intense emission lines were assigned to singly charged ions. The other emission lines belong to atoms or doubly charged ions.

  7. Cooling and Heating Functions of Photoionized Gas

    NASA Astrophysics Data System (ADS)

    Gnedin, Nickolay Y.; Hollon, Nicholas

    2012-10-01

    Cooling and heating functions of cosmic gas are crucial ingredients for any study of gas dynamics and thermodynamics in the interstellar and intergalactic media. As such, they have been studied extensively in the past under the assumption of collisional ionization equilibrium. However, for a wide range of applications, the local radiation field introduces a non-negligible, often dominant, modification to the cooling and heating functions. In the most general case, these modifications cannot be described in simple terms and would require a detailed calculation with a large set of chemical species using a radiative transfer code (the well-known code Cloudy, for example). We show, however, that for a sufficiently general variation in the spectral shape and intensity of the incident radiation field, the cooling and heating functions can be approximated as depending only on several photoionization rates, which can be thought of as representative samples of the overall radiation field. This dependence is easy to tabulate and implement in cosmological or galactic-scale simulations, thus economically accounting for an important but rarely included factor in the evolution of cosmic gas. We also show a few examples where the radiation environment has a large effect, the most spectacular of which is a quasar that suppresses gas cooling in its host halo without any mechanical or non-radiative thermal feedback.

  8. Rovibronically selected and resolved two-color laser photoionization and photoelectron study of nickel carbide cation

    SciTech Connect

    Chang, Yih Chung; Shi Xiaoyu; Ng, C. Y.; Lau, Kai-Chung; Yin Qingzhu; Liou, H. T.

    2010-08-07

    We have performed a two-color laser photoionization and photoelectron study of nickel carbide (NiC) and its cation (NiC{sup +}). By preparing NiC in a single rovibronic level of an intermediate vibronic state via visible laser excitation prior to ultraviolet laser photoionization, we have measured the photoionization efficiency spectrum of NiC near its ionization threshold, covering the formation of NiC{sup +}(X {sup 2}{Sigma}{sup +};v{sup +}=0-3). We have also obtained well-resolved rotational transitions for the v{sup +}=0 and 1 vibrational bands of the NiC{sup +}(X {sup 2}{Sigma}{sup +}) ground state. The assignment of rotational transitions observed between the neutral NiC intermediate state and the NiC{sup +} ion ground state has allowed the direct determination of a highly precise value for the ionization energy of NiC, IE(NiC)=67 525.1{+-}0.5 cm{sup -1} (8.372 05{+-}0.000 06 eV). This experiment also provides reliable values for the vibrational spacing [{Delta}G(1/2)=859.5{+-}0.5 cm{sup -1}], rotational constants (B{sub e}{sup +}=0.6395{+-}0.0018 cm{sup -1} and {alpha}{sub e}{sup +}=0.0097{+-}0.0009 cm{sup -1}), and equilibrium bond distance (r{sub e}{sup +}=1.628 A) for the NiC{sup +}(X {sup 2}{Sigma}{sup +}) ground state. The experimental results presented here are valuable for benchmarking the development of more reliable ab initio quantum computation procedures for energetic and spectroscopic calculations of transition metal-containing molecules.

  9. 4D motion animation of coronary arteries from rotational angiography

    NASA Astrophysics Data System (ADS)

    Holub, Wolfgang; Rohkohl, Christopher; Schuldhaus, Dominik; Prümmer, Marcus; Lauritsch, Günter; Hornegger, Joachim

    2011-03-01

    Time-resolved 3-D imaging of the heart is a major research topic in the medical imaging community. Recent advances in the interventional cardiac 3-D imaging from rotational angiography (C-arm CT) are now also making 4-D imaging feasible during procedures in the catheter laboratory. State-of-the-art reconstruction algorithms try to estimate the cardiac motion and utilize the motion field to enhance the reconstruction of a stable cardiac phase (diastole). The available data offers a handful of opportunities during interventional procedures, e.g. the ECG-synchronized dynamic roadmapping or the computation and analysis of functional parameters. In this paper we will demonstrate that the motion vector field (MVF) that is output by motion compensated image reconstruction algorithms is in general not directly usable for animation and motion analysis. Dependent on the algorithm different defects are investigated. A primary issue is that the MVF needs to be inverted, i.e. the wrong direction of motion is provided. A second major issue is the non-periodicity of cardiac motion. In algorithms which compute a non-periodic motion field from a single rotation the in depth motion information along viewing direction is missing, since this cannot be measured in the projections. As a result, while the MVF improves reconstruction quality, it is insufficient for motion animation and analysis. We propose an algorithm to solve both problems, i.e. inversion and missing in-depth information in a unified framework. A periodic version of the MVF is approximated. The task is formulated as a linear optimization problem where a parametric smooth motion model based on B-splines is estimated from the MVF. It is shown that the problem can be solved using a sparse QR factorization within a clinical feasible time of less than one minute. In a phantom experiment using the publicly available CAVAREV platform, the average quality of a non-periodic animation could be increased by 39% by applying the

  10. Nonvanishing high energy correlation corrections to the photoionization cross section

    NASA Astrophysics Data System (ADS)

    Amusia, Miron Ya

    2000-06-01

    Recently a prominent discrepancy was observed (see D. L. Hansen et al., Phys.. Rev.A, 60, R2641-44, 1999) between the experimental data and the results of RPAE calculations for Ar 3s-electron photoionization cross section at relatively high frequencies, from 500 eV up to 1KeV. This finding confirms the prediction (M.Ya. Amusia, in: Adv. At. Mol. Opt. Phys., ed. Bates, Academic Press, 17, 1-54, 1981), that it exists a correlation correction, whose relative role does not decrease with the photon energy growth. It appears due to strong mixing of pure "one-vacancy" and "two vacancy-one excited electron" states. Because of this correction the observed cross section differs from obtained in HF or RPAE approximations by a factor, which is photon frequency independent . This factor can be accurately enough calculated in the second order of the Many Body Perturbation Theory, giving the result of 0.75 for 3s-electrons. Similar factor for 3p-electrons is close to 1. These results are in reasonable agreement with the measured data.

  11. Fine-structure resolved photoionization of metastable Be-like ionsC III, N IV, and O V

    SciTech Connect

    Muller, A.; Schippers, S.; Phaneuf, R.A.; Kilcoyne, A.L.D.; Brauning, H.; Schlachter, A.S.; McLaughlin, B.M.

    2006-09-01

    High-resolution photoionization experiments were carried outwith beams of C III, N IV, and O V containing roughly equal amounts ofground-state and metastable ions. The energy scales of the experimentsare calibrated with uncertainties of 1 to 10 meV depending on photonenergy. These data favorably compare with state-of-the-art R-matrixcalculations carried out on an energy grid with a spacing of 13.6 mueV.

  12. VUV photoionization and dissociative photoionization spectroscopy of the interstellar molecule aminoacetonitrile: Theory and experiment

    NASA Astrophysics Data System (ADS)

    Bellili, A.; Schwell, M.; Bénilan, Y.; Fray, N.; Gazeau, M.-C.; Mogren Al-Mogren, M.; Guillemin, J.-C.; Poisson, L.; Hochlaf, M.

    2015-09-01

    Aminoacetonitrile (AAN) is a key compound in astrochemistry and astrobiology. We present a combined theoretical and experimental investigation concerning the single photoionization of gas-phase AAN and the fragmentation pathways of the resulting cation. At present, we measured photoelectron photoion coincidence (PEPICO) spectra in the 9.8-13.6 eV energy regime using synchrotron radiation as exciting light source. In order to interpret the VUV experimental data obtained, we explored the ground potential energy surface (PES) of AAN and of its cation using standard and explicitly correlated quantum chemical methodologies. This allowed us to deduce accurate thermochemical data for this molecule. We also determined, for the first time, the adiabatic ionization energy of AAN to lie at AIE = (10.085 ± 0.03) eV. The unimolecular decomposition pathways of the resulting AAN+ parent cation are also investigated. The appearance energies of five fragments are determined for the first time, with 30 meV accuracy. Interestingly, our work shows the possibility of the formation of both HCN and HNC isomeric forms. The implications for the evolution of prebiotic molecules under VUV irradiation are briefly discussed.

  13. Impact of incorporating visual biofeedback in 4D MRI.

    PubMed

    To, David T; Kim, Joshua P; Price, Ryan G; Chetty, Indrin J; Glide-Hurst, Carri K

    2016-05-08

    Precise radiation therapy (RT) for abdominal lesions is complicated by respiratory motion and suboptimal soft tissue contrast in 4D CT. 4D MRI offers improved con-trast although long scan times and irregular breathing patterns can be limiting. To address this, visual biofeedback (VBF) was introduced into 4D MRI. Ten volunteers were consented to an IRB-approved protocol. Prospective respiratory-triggered, T2-weighted, coronal 4D MRIs were acquired on an open 1.0T MR-SIM. VBF was integrated using an MR-compatible interactive breath-hold control system. Subjects visually monitored their breathing patterns to stay within predetermined tolerances. 4D MRIs were acquired with and without VBF for 2- and 8-phase acquisitions. Normalized respiratory waveforms were evaluated for scan time, duty cycle (programmed/acquisition time), breathing period, and breathing regularity (end-inhale coefficient of variation, EI-COV). Three reviewers performed image quality assessment to compare artifacts with and without VBF. Respiration-induced liver motion was calculated via centroid difference analysis of end-exhale (EE) and EI liver contours. Incorporating VBF reduced 2-phase acquisition time (4.7 ± 1.0 and 5.4 ± 1.5 min with and without VBF, respectively) while reducing EI-COV by 43.8% ± 16.6%. For 8-phase acquisitions, VBF reduced acquisition time by 1.9 ± 1.6 min and EI-COVs by 38.8% ± 25.7% despite breathing rate remaining similar (11.1 ± 3.8 breaths/min with vs. 10.5 ± 2.9 without). Using VBF yielded higher duty cycles than unguided free breathing (34.4% ± 5.8% vs. 28.1% ± 6.6%, respectively). Image grading showed that out of 40 paired evaluations, 20 cases had equivalent and 17 had improved image quality scores with VBF, particularly for mid-exhale and EI. Increased liver excursion was observed with VBF, where superior-inferior, anterior-posterior, and left-right EE-EI displacements were 14.1± 5.8, 4.9 ± 2.1, and 1.5 ± 1.0 mm, respectively, with VBF compared to 11.9

  14. 4D/RCS: a reference model architecture for intelligent unmanned ground vehicles

    NASA Astrophysics Data System (ADS)

    Albus, James S.

    2002-07-01

    4D/RCS consists of a multi-layered multi-resolutional hierarchy of computational nodes each containing elements of sensory processing (SP), world modeling (WM), value judgment (VJ), and behavior generation (BG). At the lower levels, these elements generate goal-seeking reactive behavior. At higher levels, they enable goal-defining deliberative behavior. At low levels, range in space and time is short and resolution is high. At high levels, distance and time are long and resolution is low. This enables high-precision fast-action response over short intervals of time and space at low levels, while long-range plans and abstract concepts are being formulated over broad regions of time and space at high levels. 4D/RCS closes feedback loops at every level. SP processes focus attention (i.e., window regions of space or time), group (i.e., segment regions into entities), compute entity attributes, estimate entity state, and assign entities to classes at every level. WM processes maintain a rich and dynamic database of knowledge about the world in the form of images, maps, entities, events, and relationships at every level. Other WM processes use that knowledge to generate estimates and predictions that support perception, reasoning, and planning at every level. 4D/RCS was developed for the Army Research Laboratory Demo III program. To date, only the lower levels of the 4D/RCS architecture have been fully implemented, but the results have been extremely positive. It seems clear that the theoretical basis of 4D/RCS is sound and the architecture is capable of being extended to support much higher levels of performance.

  15. Exome sequencing identifies PDE4D mutations in acrodysostosis.

    PubMed

    Lee, Hane; Graham, John M; Rimoin, David L; Lachman, Ralph S; Krejci, Pavel; Tompson, Stuart W; Nelson, Stanley F; Krakow, Deborah; Cohn, Daniel H

    2012-04-01

    Acrodysostosis is a dominantly-inherited, multisystem disorder characterized by skeletal, endocrine, and neurological abnormalities. To identify the molecular basis of acrodysostosis, we performed exome sequencing on five genetically independent cases. Three different missense mutations in PDE4D, which encodes cyclic AMP (cAMP)-specific phosphodiesterase 4D, were found to be heterozygous in three of the cases. Two of the mutations were demonstrated to have occurred de novo, providing strong genetic evidence of causation. Two additional cases were heterozygous for de novo missense mutations in PRKAR1A, which encodes the cAMP-dependent regulatory subunit of protein kinase A and which has been recently reported to be the cause of a form of acrodysostosis resistant to multiple hormones. These findings demonstrate that acrodysostosis is genetically heterogeneous and underscore the exquisite sensitivity of many tissues to alterations in cAMP homeostasis. PMID:22464252

  16. Intelligent Vehicle Systems: A 4D/RCS Approach

    SciTech Connect

    Madhavan, Raj

    2007-04-01

    This book presents new research on autonomous mobility capabilities and shows how technological advances can be anticipated in the coming two decades. An in-depth description is presented on the theoretical foundations and engineering approaches that enable these capabilities. Chapter 1 provides a brief introduction to the 4D/RCS reference model architecture and design methodology that has proven successful in guiding the development of autonomous mobility systems. Chapters 2 through 7 provide more detailed descriptions of research that has been conducted and algorithms that have been developed to implement the various aspects of the 4D/RCS reference model architecture and design methodology. Chapters 8 and 9 discuss applications, performance measures, and standards. Chapter 10 provides a history of Army and DARPA research in autonomous ground mobility. Chapter 11 provides a perspective on the potential future developments in autonomous mobility.

  17. Brain tissue segmentation in 4D CT using voxel classification

    NASA Astrophysics Data System (ADS)

    van den Boom, R.; Oei, M. T. H.; Lafebre, S.; Oostveen, L. J.; Meijer, F. J. A.; Steens, S. C. A.; Prokop, M.; van Ginneken, B.; Manniesing, R.

    2012-02-01

    A method is proposed to segment anatomical regions of the brain from 4D computer tomography (CT) patient data. The method consists of a three step voxel classification scheme, each step focusing on structures that are increasingly difficult to segment. The first step classifies air and bone, the second step classifies vessels and the third step classifies white matter, gray matter and cerebrospinal fluid. As features the time averaged intensity value and the temporal intensity change value were used. In each step, a k-Nearest-Neighbor classifier was used to classify the voxels. Training data was obtained by placing regions of interest in reconstructed 3D image data. The method has been applied to ten 4D CT cerebral patient data. A leave-one-out experiment showed consistent and accurate segmentation results.

  18. 4D embryonic cardiography using gated optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Jenkins, M. W.; Rothenberg, F.; Roy, D.; Nikolski, V. P.; Hu, Z.; Watanabe, M.; Wilson, D. L.; Efimov, I. R.; Rollins, A. M.

    2006-01-01

    Simultaneous imaging of very early embryonic heart structure and function has technical limitations of spatial and temporal resolution. We have developed a gated technique using optical coherence tomography (OCT) that can rapidly image beating embryonic hearts in four-dimensions (4D), at high spatial resolution (10-15 μm), and with a depth penetration of 1.5 - 2.0 mm that is suitable for the study of early embryonic hearts. We acquired data from paced, excised, embryonic chicken and mouse hearts using gated sampling and employed image processing techniques to visualize the hearts in 4D and measure physiologic parameters such as cardiac volume, ejection fraction, and wall thickness. This technique is being developed to longitudinally investigate the physiology of intact embryonic hearts and events that lead to congenital heart defects.

  19. Photoionization of Highly Charged Argon Ions and Their Diagnostic Lines

    NASA Astrophysics Data System (ADS)

    Nahar, Sultana N.

    2012-06-01

    %TEXT OF YOUR ABSTRACT Lines of highly charged He-like and Li-like ions in the ultraviolet and X-ray regions provide useful diagnostics for the physical and chemical conditions of the astrophysical as well as fusion plasmas. For example, Ar XVII lines in a Syfert galaxy have been measured by the X-ray space observatory Chandra. Results on photoionization of Ar XVI and Ar XVII obtained from relativistic Breit-Pauli R-matrix method and close-coupling approximation will be presented. Important features for level-specific photoionization for the diagnostic w, x, y, z lines of He-like Ar XVII in the ultraviolet region will be illustrated. Although monotonous decay dominates the low energy photoionization for these ions, strong resonances appear in the high energy region indicating higher recombination, inverse process of photoionization, at high temperature. The spectra of the well known 22 diagnostics dielectronic satellite lines of Li-like Ar XVI will be shown produced from the the KLL resonances in photoionization. Acknowledgement: Partially supported by DOE, NSF; Computational work was carried out at the Ohio Supercomputer Center

  20. 4D flow cardiovascular magnetic resonance consensus statement.

    PubMed

    Dyverfeldt, Petter; Bissell, Malenka; Barker, Alex J; Bolger, Ann F; Carlhäll, Carl-Johan; Ebbers, Tino; Francios, Christopher J; Frydrychowicz, Alex; Geiger, Julia; Giese, Daniel; Hope, Michael D; Kilner, Philip J; Kozerke, Sebastian; Myerson, Saul; Neubauer, Stefan; Wieben, Oliver; Markl, Michael

    2015-01-01

    Pulsatile blood flow through the cavities of the heart and great vessels is time-varying and multidirectional. Access to all regions, phases and directions of cardiovascular flows has formerly been limited. Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) has enabled more comprehensive access to such flows, with typical spatial resolution of 1.5×1.5×1.5 - 3×3×3 mm(3), typical temporal resolution of 30-40 ms, and acquisition times in the order of 5 to 25 min. This consensus paper is the work of physicists, physicians and biomedical engineers, active in the development and implementation of 4D Flow CMR, who have repeatedly met to share experience and ideas. The paper aims to assist understanding of acquisition and analysis methods, and their potential clinical applications with a focus on the heart and greater vessels. We describe that 4D Flow CMR can be clinically advantageous because placement of a single acquisition volume is straightforward and enables flow through any plane across it to be calculated retrospectively and with good accuracy. We also specify research and development goals that have yet to be satisfactorily achieved. Derived flow parameters, generally needing further development or validation for clinical use, include measurements of wall shear stress, pressure difference, turbulent kinetic energy, and intracardiac flow components. The dependence of measurement accuracy on acquisition parameters is considered, as are the uses of different visualization strategies for appropriate representation of time-varying multidirectional flow fields. Finally, we offer suggestions for more consistent, user-friendly implementation of 4D Flow CMR acquisition and data handling with a view to multicenter studies and more widespread adoption of the approach in routine clinical investigations. PMID:26257141

  1. Phosphodiesterase 4D gene polymorphisms in sudden sensorineural hearing loss.

    PubMed

    Chien, Chen-Yu; Tai, Shu-Yu; Wang, Ling-Feng; Hsi, Edward; Chang, Ning-Chia; Wang, Hsun-Mo; Wu, Ming-Tsang; Ho, Kuen-Yao

    2016-09-01

    The phosphodiesterase 4D (PDE4D) gene has been reported as a risk gene for ischemic stroke. The vascular factors are between the hypothesized etiologies of sudden sensorineural hearing loss (SSNHL), and this genetic effect might be attributed for its role in SSNHL. We hypothesized that genetic variants of the PDE4D gene are associated with susceptibility to SSNHL. We conducted a case-control study with 362 SSNHL cases and 209 controls. Three single nucleotide polymorphisms (SNPs) were selected. The genotypes were determined using TaqMan technology. Hardy-Weinberg equilibrium (HWE) was tested for each SNP, and genetic effects were evaluated according to three inheritance modes. We carried out sex-specific analysis to analyze the overall data. All three SNPs were in HWE. When subjects were stratified by sex, the genetic effect was only evident in females but not in males. The TT genotype of rs702553 exhibited an adjusted odds ratio (OR) of 3.83 (95 % confidence interval = 1.46-11.18) (p = 0.006) in female SSNHL. The TT genotype of SNP rs702553 was associated with female SSNHL under the recessive model (p = 0.004, OR 3.70). In multivariate logistic regression analysis, TT genotype of rs702553 was significantly associated with female SSNHL (p = 0.0043, OR 3.70). These results suggest that PDE4D gene polymorphisms influence the susceptibility for the development of SSNHL in the southern Taiwanese female population.

  2. A 4D Hyperspherical Interpretation of q-Space

    PubMed Central

    Hosseinbor, A. Pasha; Chung, Moo K.; Wu, Yu-Chien; Bendlin, Barbara B.; Alexander, Andrew L.

    2015-01-01

    3D q-space can be viewed as the surface of a 4D hypersphere. In this paper, we seek to develop a 4D hyperspherical interpretation of q-space by projecting it onto a hypersphere and subsequently modeling the q-space signal via 4D hyperspherical harmonics (HSH). Using this orthonormal basis, we derive several well-established q-space indices and numerically estimate the diffusion orientation distribution function (dODF). We also derive the integral transform describing the relationship between the diffusion signal and propagator on a hypersphere. Most importantly, we will demonstrate that for hybrid diffusion imaging (HYDI) acquisitions low order linear expansion of the HSH basis is sufficient to characterize diffusion in neural tissue. In fact, the HSH basis achieves comparable signal and better dODF reconstructions than other well-established methods, such as Bessel Fourier orientation reconstruction (BFOR), using fewer fitting parameters. All in all, this work provides a new way of looking at q-space. PMID:25624043

  3. 4D-Flow validation, numerical and experimental framework

    NASA Astrophysics Data System (ADS)

    Sansom, Kurt; Liu, Haining; Canton, Gador; Aliseda, Alberto; Yuan, Chun

    2015-11-01

    This work presents a group of assessment metrics of new 4D MRI flow sequences, an imaging modality that allows for visualization of three-dimensional pulsatile flow in the cardiovascular anatomy through time-resolved three-dimensional blood velocity measurements from cardiac-cycle synchronized MRI acquisition. This is a promising tool for clinical assessment but lacks a robust validation framework. First, 4D-MRI flow in a subject's stenotic carotid bifurcation is compared with a patient-specific CFD model using two different boundary condition methods. Second, Particle Image Velocimetry in a patient-specific phantom is used as a benchmark to compare the 4D-MRI in vivo measurements and CFD simulations under the same conditions. Comparison of estimated and measureable flow parameters such as wall shear stress, fluctuating velocity rms, Lagrangian particle residence time, will be discussed, with justification for their biomechanics relevance and the insights they can provide on the pathophysiology of arterial disease: atherosclerosis and intimal hyperplasia. Lastly, the framework is applied to a new sequence to provide a quantitative assessment. A parametric analysis on the carotid bifurcation pulsatile flow conditions will be presented and an accuracy assessment provided.

  4. Advances Toward Inner-Shell Photo-Ionization X-Ray Lasing at 45 (Angstrom)

    SciTech Connect

    Moon, S J; Weber, F A; Celliers, P M; Eder, D C

    2002-07-18

    The inner-shell photo-ionization (ISPI) scheme requires photon energies at least high enough to photo-ionize the K-shell. {approx}286 eV, in the case of carbon. As a consequence of the higher cross-section, the inner-shell are selectively knocked out, leaving a hole state 1s2s{sup 2}2p{sup 2} in the singly charged carbon ion. This generates a population inversion to the radiatively connected state 1s{sup 2}2s{sup 2}2p in C+, leading to gain on the 1s-2p transition at 45 {angstrom}. The resonant character of the lasing transition in the single ionization state intrinsically allows much higher quantum efficiency compared to other schemes. Competing processes that deplete the population inversion include auto-ionization, Auger decay, and in particular collisional ionization of the outer-shell electrons by electrons generated during photo-ionization. These competing processes rapidly quench the gain. Consequently, the pump method must be capable of populating the inversion at a rate faster than the competing processes. This can be achieved by an ultra-fast, high intensity laser that is able to generate an ultra-fast, bright x-ray source. With current advances in the development of high-power, ultra-short pulse lasers it is possible to realize fast x-ray sources based that can deliver powerful pulses of light in the multiple hundred terawatt regime and beyond. They will discuss in greater detail concept, target design and a series of x-ray spectroscopy investigations they have conducted in order to optimize the absorber/x-ray converter--filter package.

  5. Atomic Data for Neutron-capture Elements I. Photoionization and Recombination Properties of Low-charge Selenium Ions

    NASA Technical Reports Server (NTRS)

    Sterling, N. C.; Witthoeft, Michael

    2011-01-01

    We present multi-configuration Breit-Pauli AUTOSTRUCTURE calculations of distorted-wave photoionization (PI) cross sections. and total and partial final-state resolved radiative recombination (RR) and dielectronic recombination (DR) rate coefficients for the first six ions of the trans-iron element Se. These calculations were motivated by the recent detection of Se emission lines in a large number of planetary nebulae. Se is a potentially useful tracer of neutron-capture nucleosynthesis. but accurate determinations of its abundance in photoionized nebulae have been hindered by the lack of atomic data governing its ionization balance. Our calculations were carried out in intermediate coupling with semi re1ativistic radial wavefunctions. PI and recombination data were determined for levels within the ground configuration of each ion, and experimental PI cross-section measurements were used to benchmark our results. For DR, we allowed (Delta)n = 0 core excitations, which are important at photoionized plasma temperatures. We find that DR is the dominant recombination process for each of these Se ions at temperatures representative of photoionized nebulae (approx.10(exp 4) K). In order to estimate the uncertainties of these data, we compared results from three different configuration-interaction expansions for each ion, and also tested the sensitivity of the results to the radial scaling factors in the structure calculations. We find that the internal uncertainties are typically 30-50% for the direct PI cross sections and approx.10% for the computed RR rate coefficients, while those for low-temperature DR can be considerably larger (from 15-30% up to two orders of magnitude) due to the unknown energies of near-threshold autoionization resonances. These data are available at the CDS, and fitting coefficients to the total RR and DR rate coefficients are presented. The results are suitable for incorporation into photoionization codes used to numerically simulate

  6. Interchannel coupling effects in the valence photoionization of SF6

    NASA Astrophysics Data System (ADS)

    Jose, Jobin; Lucchese, Robert; Rescigno, Tom

    2014-05-01

    The complex Kohn and polyatomic Schwinger variational techniques have been employed to illustrate the interchannel coupling correlation effects in the valence photoionization dynamics of SF6. Partial photoionization cross sections and asymmetry parameters of six valence subshells (1t1 g, 5t1 u, 1t2 u, 3eg, 1t2 g, 4t1 u) are discussed in the framework of several theoretical and experimental studies. The complex Kohn results are in rather good agreement with experimental results, indicative of the fact that the interchannel coupling effects alter the photoionization dynamics significantly. We find that the dominant effect of interchannel coupling is to reduce the magnitude of shape resonant cross sections near threshold and to induce resonant features in other channels to which resonances are coupled.

  7. Triggering Excimer Lasers by Photoionization from Corona Discharges

    NASA Astrophysics Data System (ADS)

    Xiong, Zhongmin; Duffey, Thomas; Brown, Daniel; Kushner, Mark

    2009-10-01

    High repetition rate ArF (192 nm) excimer lasers are used for photolithography sources in microelectronics fabrication. In highly attaching gas mixtures, preionization is critical to obtaining stable, reproducible glow discharges. Photoionization from a separate corona discharge is one technique for preionization which triggers the subsequent electron avalanche between the main electrodes. Photoionization triggering of an ArF excimer laser sustained in multi-atmosphere Ne/Ar/F2/Xe gas mixtures has been investigated using a 2-dimensional plasma hydrodynamics model including radiation transport. Continuity equations for charged and neutral species, and Poisson's equation are solved coincident with the electron temperature with transport coefficients obtained from solutions of Boltzmann's equation. Photoionizing radiation is produced by a surface discharge which propagates along a corona-bar located adjacent to the discharge electrodes. The consequences of pulse power waveform, corona bar location, capacitance and gas mixture on uniformity, symmetry and gain of the avalanche discharge will be discussed.

  8. Kinetic energies of fragment ions produced by dissociative photoionization of NO

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Angel, G. C.; Rstgi, O. P.

    1985-01-01

    The kinetic energies of ions produced by dissociative photoionization of NO have been measured at the discrete resonance lines of He (584A) and Ne (736A), and with undispersed synchrotron radiation. O sup + ions were identified with energies from 0 to approximately 0.5 eV and two groups of N sup + ions one with energy of 0.36 eV and another with energies between 0.9 and 1.5 eV, apparently produced by predissociation of the C sup 3 P 1 and B'1 sigma states respectively.

  9. First Principles Study of Double Photoionization of H2 UsingExterior Complex Scaling

    SciTech Connect

    Rescigno, Thomas N.; Vanroose, Wim; Horner, Daniel A.; Martin,Fernando; McCurdy, C. William

    2006-07-21

    Exterior complex scaling provides a practical path forfirst-principles studies of atomic and molecular ionizationproblemssince it avoids explicit enforcement of asymptotic boundary conditionsfor 3-body Coulomb breakup. We have used the method of exterior complexscaling, implemented with both the discrete variable representation andB-splines, to obtain the first-order wave function for molecular hydrogencorresponding to a single photon having been absorbed by a correlatedinitial state. These wave functions are used to construct convergedtriple differential cross sections for double photoionization of alignedH2 molecules.

  10. Ultrafast Dynamics in Postcollision Interaction after Multiple Auger Decays in Argon 1s Photoionization

    NASA Astrophysics Data System (ADS)

    Guillemin, R.; Sheinerman, S.; Bomme, C.; Journel, L.; Marin, T.; Marchenko, T.; Kushawaha, R. K.; Trcera, N.; Piancastelli, M. N.; Simon, M.

    2012-07-01

    Argon 1s photoionization followed by multiple Auger decays is investigated both experimentally, by means of photoelectron-ion coincidences, and theoretically. A strong influence of the different Auger decays on the photoelectron spectra is observed through postcollision interaction which shifts the maximum of the energy distribution and distorts the spectral shape. A good agreement between the calculated and measured spectra for selected Arn+ ions (n=1-5) allows one to estimate the widths (lifetimes) of the intermediate states for each specific decay pathway.

  11. Vibrational branching ratios in the (b(2u))(-1) photoionization of C6F6.

    PubMed

    Lucchese, Robert R; Bozek, John D; Das, Aloke; Poliakoff, E D

    2009-07-28

    The vibrational branching ratios in the photoionization of C(6)F(6) leading to the C (2)B(2u) state of C(6)F(6)(+) are considered. Computational and experimental data are compared for the excitation of two totally symmetric modes. Resonant features at photon energies near 19 and 21 eV are found. A detailed analysis of the computed results shows that the two resonance states have different responses to changes in the C-C and C-F bond lengths. We find that the energies of both of the resonant states decrease with increasing bond lengths. In contrast to the energy positions, however, the resonant widths and the integrated oscillator strength of the resonances can either increase or decrease with increasing bond length depending on the nature and location of the resonant state and the location of the bond under consideration. With increasing C-F bond length, we find that the energy of the antibonding sigma resonance localized on the ring has a decreasing resonance energy and also a decreasing lifetime. This behavior is in contrast to the usual behavior of shape resonance energies where increasing a bond length leads to decreasing resonance energies and increasing resonance lifetimes. Finally, for the first time, we examine the effect of simultaneously occurring multiple vibrations on the resonance profile for valence photoionization, and we find that the inclusion of more than a single vibrational mode substantially attenuates the strength of resonance.

  12. Photoionization of sodium atoms and electron scattering from ionized sodium

    NASA Technical Reports Server (NTRS)

    Dasgupta, A.; Bhatia, A. K.

    1985-01-01

    The polarized-orbital method of Temkin (1957) is applied using polarized orbitals determined from Sternheimer's equation to compute the photoionization cross sections of Na atoms from threshold to about 60 eV. The approximations involved in the analysis are explained in detail; the explicit forms of the integrals and matrix expressions are given in appendices; and the results are presented in tables and graphs. Good agreement is found with the results of Chang and Kelly (1975), and the possibility that small amounts of molecular vapor in Na-photoionization experiments are responsible for the discrepancies between calculated and measured cross sections is considered.

  13. A photoionization study of the formation of CO2/+/ by reaction of excited O2/+/ ions with CO

    NASA Technical Reports Server (NTRS)

    Ajello, J. M.

    1975-01-01

    The production of CO2(+) by the ion-molecule reaction O2(+) + CO yields CO2(+) + O has been investigated using a photoionization mass spectrometer. The photoionization efficiency for production of CO2(+) by this reaction was measured from threshold at 924 A (13.42 eV) to 650 A (19.07 eV). The appearance potential corresponds to reaction of ground vibronic O2(+) ions formed in the nu-prime = 6 level. The high-vibrational-level ions of the ground ionic state are most likely produced by autoionization of O2. At wavelengths shorter than 760 A, there is a large increase in the reaction cross section associated with formation of ions in the metastable state. The peak reaction cross section occurs at 720 A.

  14. 4D Proton treatment planning strategy for mobile lung tumors

    SciTech Connect

    Kang Yixiu; Zhang Xiaodong; Chang, Joe Y.; Wang He; Wei Xiong; Liao Zhongxing; Komaki, Ritsuko; Cox, James D.; Balter, Peter A.; Liu, Helen; Zhu, X. Ronald; Mohan, Radhe; Dong Lei . E-mail: ldong@mdanderson.org

    2007-03-01

    Purpose: To investigate strategies for designing compensator-based 3D proton treatment plans for mobile lung tumors using four-dimensional computed tomography (4DCT) images. Methods and Materials: Four-dimensional CT sets for 10 lung cancer patients were used in this study. The internal gross tumor volume (IGTV) was obtained by combining the tumor volumes at different phases of the respiratory cycle. For each patient, we evaluated four planning strategies based on the following dose calculations: (1) the average (AVE) CT; (2) the free-breathing (FB) CT; (3) the maximum intensity projection (MIP) CT; and (4) the AVE CT in which the CT voxel values inside the IGTV were replaced by a constant density (AVE{sub R}IGTV). For each strategy, the resulting cumulative dose distribution in a respiratory cycle was determined using a deformable image registration method. Results: There were dosimetric differences between the apparent dose distribution, calculated on a single CT dataset, and the motion-corrected 4D dose distribution, calculated by combining dose distributions delivered to each phase of the 4DCT. The AVE{sub R}IGTV plan using a 1-cm smearing parameter had the best overall target coverage and critical structure sparing. The MIP plan approach resulted in an unnecessarily large treatment volume. The AVE and FB plans using 1-cm smearing did not provide adequate 4D target coverage in all patients. By using a larger smearing value, adequate 4D target coverage could be achieved; however, critical organ doses were increased. Conclusion: The AVE{sub R}IGTV approach is an effective strategy for designing proton treatment plans for mobile lung tumors.

  15. Phase and amplitude binning for 4D-CT imaging

    NASA Astrophysics Data System (ADS)

    Abdelnour, A. F.; Nehmeh, S. A.; Pan, T.; Humm, J. L.; Vernon, P.; Schöder, H.; Rosenzweig, K. E.; Mageras, G. S.; Yorke, E.; Larson, S. M.; Erdi, Y. E.

    2007-07-01

    We compare the consistency and accuracy of two image binning approaches used in 4D-CT imaging. One approach, phase binning (PB), assigns each breathing cycle 2π rad, within which the images are grouped. In amplitude binning (AB), the images are assigned bins according to the breathing signal's full amplitude. To quantitate both approaches we used a NEMA NU2-2001 IEC phantom oscillating in the axial direction and at random frequencies and amplitudes, approximately simulating a patient's breathing. 4D-CT images were obtained using a four-slice GE Lightspeed CT scanner operating in cine mode. We define consistency error as a measure of ability to correctly bin over repeated cycles in the same field of view. Average consistency error μe ± σe in PB ranged from 18% ± 20% to 30% ± 35%, while in AB the error ranged from 11% ± 14% to 20% ± 24%. In PB nearly all bins contained sphere slices. AB was more accurate, revealing empty bins where no sphere slices existed. As a proof of principle, we present examples of two non-small cell lung carcinoma patients' 4D-CT lung images binned by both approaches. While AB can lead to gaps in the coronal images, depending on the patient's breathing pattern, PB exhibits no gaps but suffers visible artifacts due to misbinning, yielding images that cover a relatively large amplitude range. AB was more consistent, though often resulted in gaps when no data existed due to patients' breathing pattern. We conclude AB is more accurate than PB. This has important consequences to treatment planning and diagnosis.

  16. Non-spherical particle generation from 4D optofluidic fabrication.

    PubMed

    Paulsen, Kevin S; Chung, Aram J

    2016-08-01

    Particles with non-spherical shapes can exhibit properties which are not available from spherical shaped particles. Complex shaped particles can provide unique benefits for areas such as drug delivery, tissue engineering, structural materials, and self-assembly building blocks. Current methods of creating complex shaped particles such as 3D printing, photolithography, and imprint lithography are limited by either slow speeds, shape limitations, or expensive processes. Previously, we presented a novel microfluidic flow lithography fabrication scheme combined with fluid inertia called optofluidic fabrication for the creation of complex shaped three-dimensional (3D) particles. This process was able to address the aforementioned limits and overcome two-dimensional shape limitations faced by traditional flow lithography methods; however, all of the created 3D particle shapes displayed top-down symmetry. Here, by introducing the time dimension into our existing optofluidic fabrication process, we break this top-down symmetry, generating fully asymmetric 3D particles where we termed the process: four-dimensional (4D) optofluidic fabrication. This 4D optofluidic fabrication is comprised of three sequential procedures. First, density mismatched precursor fluids flow past pillars within fluidic channels to manipulate the flow cross sections via fluid inertia. Next, the time dimension is incorporated by stopping the flow and allowing the denser fluids to settle by gravity to create asymmetric flow cross sections. Finally, the fluids are exposed to patterned ultraviolet (UV) light in order to polymerize fully asymmetric 3D-shaped particles. By varying inertial flow shaping, gravity-induced flow shaping, and UV light patterns, 4D optofluidic fabrication can create an infinite set of complex shaped asymmetric particles. PMID:27092661

  17. Non-spherical particle generation from 4D optofluidic fabrication.

    PubMed

    Paulsen, Kevin S; Chung, Aram J

    2016-08-01

    Particles with non-spherical shapes can exhibit properties which are not available from spherical shaped particles. Complex shaped particles can provide unique benefits for areas such as drug delivery, tissue engineering, structural materials, and self-assembly building blocks. Current methods of creating complex shaped particles such as 3D printing, photolithography, and imprint lithography are limited by either slow speeds, shape limitations, or expensive processes. Previously, we presented a novel microfluidic flow lithography fabrication scheme combined with fluid inertia called optofluidic fabrication for the creation of complex shaped three-dimensional (3D) particles. This process was able to address the aforementioned limits and overcome two-dimensional shape limitations faced by traditional flow lithography methods; however, all of the created 3D particle shapes displayed top-down symmetry. Here, by introducing the time dimension into our existing optofluidic fabrication process, we break this top-down symmetry, generating fully asymmetric 3D particles where we termed the process: four-dimensional (4D) optofluidic fabrication. This 4D optofluidic fabrication is comprised of three sequential procedures. First, density mismatched precursor fluids flow past pillars within fluidic channels to manipulate the flow cross sections via fluid inertia. Next, the time dimension is incorporated by stopping the flow and allowing the denser fluids to settle by gravity to create asymmetric flow cross sections. Finally, the fluids are exposed to patterned ultraviolet (UV) light in order to polymerize fully asymmetric 3D-shaped particles. By varying inertial flow shaping, gravity-induced flow shaping, and UV light patterns, 4D optofluidic fabrication can create an infinite set of complex shaped asymmetric particles.

  18. Founding Gravitation in 4D Euclidean Space-Time Geometry

    SciTech Connect

    Winkler, Franz-Guenter

    2010-11-24

    The Euclidean interpretation of special relativity which has been suggested by the author is a formulation of special relativity in ordinary 4D Euclidean space-time geometry. The natural and geometrically intuitive generalization of this view involves variations of the speed of light (depending on location and direction) and a Euclidean principle of general covariance. In this article, a gravitation model by Jan Broekaert, which implements a view of relativity theory in the spirit of Lorentz and Poincare, is reconstructed and shown to fulfill the principles of the Euclidean approach after an appropriate reinterpretation.

  19. CMT4D (NDRG1 mutation): genotype-phenotype correlations.

    PubMed

    Ricard, Emilie; Mathis, Stéphane; Magdelaine, Corinne; Delisle, Marie-Bernadette; Magy, Laurent; Funalot, Benoît; Vallat, Jean-Michel

    2013-09-01

    Charcot-Marie-Tooth (CMT) disease is a heterogeneous condition with a large number of clinical, electrophysiological and pathological phenotypes. More than 40 genes are involved. We report a child of gypsy origin with an autosomal recessive demyelinating phenotype. Clinical data, familial history, and electrophysiological studies were in favor of a CMT4 sub-type. The characteristic N-Myc downstream-regulated gene 1 (NDRG1) mutation responsible for this CMT4D phenotype was confirmed: p.R148X. The exact molecular function of the NDRG1 protein has yet to be elucidated.

  20. Multicolor 4D Fluorescence Microscopy using Ultrathin Bessel Light Sheets.

    PubMed

    Zhao, Teng; Lau, Sze Cheung; Wang, Ying; Su, Yumian; Wang, Hao; Cheng, Aifang; Herrup, Karl; Ip, Nancy Y; Du, Shengwang; Loy, M M T

    2016-01-01

    We demonstrate a simple and efficient method for producing ultrathin Bessel ('non-diffracting') light sheets of any color using a line-shaped beam and an annulus filter. With this robust and cost-effective technology, we obtained two-color, 3D images of biological samples with lateral/axial resolution of 250 nm/400 nm, and high-speed, 4D volume imaging of 20 μm sized live sample at 1 Hz temporal resolution. PMID:27189786

  1. Oblique sounding using the DPS-4D stations in Europe

    NASA Astrophysics Data System (ADS)

    Mosna, Zbysek; Kouba, Daniel; Koucka Knizova, Petra; Arikan, Feza; Arikan, Orhan; Gok, Gokhan; Rejfek, Lubos

    2016-07-01

    The DPS-4D Digisondes are capable of detection of echoes from neighbouring European stations. Currently, a campaign with high-temporal resolution of 5 min is being run. Further, ionograms from regular vertical sounding with 15 min resolution provide us with oblique reflections together with vertical reflections. We analyzed profiles of electron concentration and basic ionospheric parameters derived from the ionograms. We compared results derived from reflections from the ionosphere above the stations (vertical sounding) with information derived from oblique reflections between the stations. This study is supported by the Joint TUBITAK 114E092 and AS CR 14/001 projects.

  2. Lagrangian constraints and renormalization of 4D gravity

    NASA Astrophysics Data System (ADS)

    Park, I. Y.

    2015-04-01

    It has been proposed in [21] that 4D Einstein gravity becomes effectively reduced to 3D after solving the Lagrangian analogues of the Hamiltonian and momentum constraints of the Hamiltonian quantization. The analysis in [21] was carried out at the classical/operator level. We review the proposal and make a transition to the path integral account. We then set the stage for explicitly carrying out the two-loop renormalization procedure of the resulting 3D action. We also address a potentially subtle issue in the gravity context concerning whether renormalizability does not depend on the background around which the original action is expanded.

  3. Multicolor 4D Fluorescence Microscopy using Ultrathin Bessel Light Sheets

    PubMed Central

    Zhao, Teng; Lau, Sze Cheung; Wang, Ying; Su, Yumian; Wang, Hao; Cheng, Aifang; Herrup, Karl; Ip, Nancy Y.; Du, Shengwang; Loy, M. M. T.

    2016-01-01

    We demonstrate a simple and efficient method for producing ultrathin Bessel (‘non-diffracting’) light sheets of any color using a line-shaped beam and an annulus filter. With this robust and cost-effective technology, we obtained two-color, 3D images of biological samples with lateral/axial resolution of 250 nm/400 nm, and high-speed, 4D volume imaging of 20 μm sized live sample at 1 Hz temporal resolution. PMID:27189786

  4. All the supersymmetric configurations of N=4, d=4 supergravity

    NASA Astrophysics Data System (ADS)

    Bellorín, Jorge; Ortín, Tomás

    2005-10-01

    All the supersymmetric configurations of pure, ungauged, N=4, d=4 supergravity are classified in a formalism that keeps manifest the S and T dualities of the theory. We also find simple equations that need to be satisfied by the configurations to be classical solutions of the theory. While the solutions associated to null Killing vectors were essentially classified by Tod (a classification that we refine), we find new configurations and solutions associated to timelike Killing vectors that do not satisfy Tod's rigidity hypothesis (hence, they have a nontrivial U(1) connection) and whose supersymmetry projector is associated to 1-dimensional objects (strings), although they have a trivial axion field.

  5. Actively triggered 4d cone-beam CT acquisition

    SciTech Connect

    Fast, Martin F.; Wisotzky, Eric; Oelfke, Uwe; Nill, Simeon

    2013-09-15

    Purpose: 4d cone-beam computed tomography (CBCT) scans are usually reconstructed by extracting the motion information from the 2d projections or an external surrogate signal, and binning the individual projections into multiple respiratory phases. In this “after-the-fact” binning approach, however, projections are unevenly distributed over respiratory phases resulting in inefficient utilization of imaging dose. To avoid excess dose in certain respiratory phases, and poor image quality due to a lack of projections in others, the authors have developed a novel 4d CBCT acquisition framework which actively triggers 2d projections based on the forward-predicted position of the tumor.Methods: The forward-prediction of the tumor position was independently established using either (i) an electromagnetic (EM) tracking system based on implanted EM-transponders which act as a surrogate for the tumor position, or (ii) an external motion sensor measuring the chest-wall displacement and correlating this external motion to the phase-shifted diaphragm motion derived from the acquired images. In order to avoid EM-induced artifacts in the imaging detector, the authors devised a simple but effective “Faraday” shielding cage. The authors demonstrated the feasibility of their acquisition strategy by scanning an anthropomorphic lung phantom moving on 1d or 2d sinusoidal trajectories.Results: With both tumor position devices, the authors were able to acquire 4d CBCTs free of motion blurring. For scans based on the EM tracking system, reconstruction artifacts stemming from the presence of the EM-array and the EM-transponders were greatly reduced using newly developed correction algorithms. By tuning the imaging frequency independently for each respiratory phase prior to acquisition, it was possible to harmonize the number of projections over respiratory phases. Depending on the breathing period (3.5 or 5 s) and the gantry rotation time (4 or 5 min), between ∼90 and 145

  6. 4D micro-CT using fast prospective gating

    NASA Astrophysics Data System (ADS)

    Guo, Xiaolian; Johnston, Samuel M.; Qi, Yi; Johnson, G. Allan; Badea, Cristian T.

    2012-01-01

    Micro-CT is currently used in preclinical studies to provide anatomical information. But, there is also significant interest in using this technology to obtain functional information. We report here a new sampling strategy for 4D micro-CT for functional cardiac and pulmonary imaging. Rapid scanning of free-breathing mice is achieved with fast prospective gating (FPG) implemented on a field programmable gate array. The method entails on-the-fly computation of delays from the R peaks of the ECG signals or the peaks of the respiratory signals for the triggering pulses. Projection images are acquired for all cardiac or respiratory phases at each angle before rotating to the next angle. FPG can deliver the faster scan time of retrospective gating (RG) with the regular angular distribution of conventional prospective gating for cardiac or respiratory gating. Simultaneous cardio-respiratory gating is also possible with FPG in a hybrid retrospective/prospective approach. We have performed phantom experiments to validate the new sampling protocol and compared the results from FPG and RG in cardiac imaging of a mouse. Additionally, we have evaluated the utility of incorporating respiratory information in 4D cardiac micro-CT studies with FPG. A dual-source micro-CT system was used for image acquisition with pulsed x-ray exposures (80 kVp, 100 mA, 10 ms). The cardiac micro-CT protocol involves the use of a liposomal blood pool contrast agent containing 123 mg I ml-1 delivered via a tail vein catheter in a dose of 0.01 ml g-1 body weight. The phantom experiment demonstrates that FPG can distinguish the successive phases of phantom motion with minimal motion blur, and the animal study demonstrates that respiratory FPG can distinguish inspiration and expiration. 4D cardiac micro-CT imaging with FPG provides image quality superior to RG at an isotropic voxel size of 88 µm and 10 ms temporal resolution. The acquisition time for either sampling approach is less than 5 min. The

  7. Resolution enhancement of lung 4D-CT via group-sparsity

    SciTech Connect

    Bhavsar, Arnav; Wu, Guorong; Shen, Dinggang; Lian, Jun

    2013-12-15

    quantitatively, the ability of their approach to achieve more accurate and better localized results over bicubic interpolation as well as a related state-of-the-art approach. The authors also show results on some datasets with tumor, to further emphasize the clinical importance of their method.Conclusions: The authors have proposed to improve the superior-inferior resolution of 4D-CT by estimating intermediate slices. The authors’ approach exploits neighboring constraints in the group-sparsity framework, toward the goal of achieving better localization and noise robustness. The authors’ results are encouraging, and positively demonstrate the role of group-sparsity for 4D-CT resolution enhancement.

  8. Valence and L-shell photoionization of Cl-like argon using R-matrix techniques

    NASA Astrophysics Data System (ADS)

    Tyndall, N. B.; Ramsbottom, C. A.; Ballance, C. P.; Hibbert, A.

    2016-02-01

    Photoionization cross-sections are obtained using the relativistic Dirac Atomic R-matrix Codes (DARC) for all valence and L-shell energy ranges between 27 and 270 eV. A total of 557 levels arising from the dominant configurations 3s23p4, 3s3p5, 3p6, 3s23p3[3d, 4s, 4p], 3p53d, 3s23p23d2, 3s3p43d, 3s3p33d2 and 2s22p53s23p5 have been included in the target wavefunction representation of the Ar III ion, including up to 4p in the orbital basis. We also performed a smaller Breit-Pauli (BP) calculation containing the lowest 124 levels. Direct comparisons are made with previous theoretical and experimental work for both valence shell and L-shell photoionization. Excellent agreement was found for transitions involving the 2Po initial state to all allowed final states for both calculations across a range of photon energies. A number of resonant states have been identified to help analyse and explain the nature of the spectra at photon energies between 250 and 270 eV.

  9. Photoionization of Li and radiative recombination of Li{sup +} in Debye plasmas

    SciTech Connect

    Qi, Y. Y.; Wu, Y.; Wang, J. G.

    2009-03-15

    The photoionization cross sections in the photoelectron energy below 2 Ry are calculated for the ground and n{<=}4 excited states of Li embedded in plasma environments and the radiative-recombination (RR) rate coefficients for Li{sup +} were presented for temperature T=100-32 000 K in a wide range of plasma parameters. The plasma screening interaction is described by the Debye-Hueckel model and the energy levels and wave functions including both the bound and continuum states are calculated by solving the Schroedinger equation numerically in a symplectic integration scheme. The screening of Coulomb interactions remarkably changes the photoionization cross sections near the ionization threshold, and especially for the ns states, the Cooper minimum is uncovered and shifted to the higher energy as the screening interaction increases. The RR rate coefficients at low temperature have a complex variation on the Debye lengths; whereas at higher temperature the RR rate coefficients decrease with the increasing of screening effects. Comparison of present results with those of other authors when available is made.

  10. Functional organization of the human 4D Nucleome

    PubMed Central

    Chen, Haiming; Chen, Jie; Muir, Lindsey A.; Ronquist, Scott; Meixner, Walter; Ljungman, Mats; Ried, Thomas; Smale, Stephen; Rajapakse, Indika

    2015-01-01

    The 4D organization of the interphase nucleus, or the 4D Nucleome (4DN), reflects a dynamical interaction between 3D genome structure and function and its relationship to phenotype. We present initial analyses of the human 4DN, capturing genome-wide structure using chromosome conformation capture and 3D imaging, and function using RNA-sequencing. We introduce a quantitative index that measures underlying topological stability of a genomic region. Our results show that structural features of genomic regions correlate with function with surprising persistence over time. Furthermore, constructing genome-wide gene-level contact maps aided in identifying gene pairs with high potential for coregulation and colocalization in a manner consistent with expression via transcription factories. We additionally use 2D phase planes to visualize patterns in 4DN data. Finally, we evaluated gene pairs within a circadian gene module using 3D imaging, and found periodicity in the movement of clock circadian regulator and period circadian clock 2 relative to each other that followed a circadian rhythm and entrained with their expression. PMID:26080430

  11. Atlas construction for dynamic (4D) PET using diffeomorphic transformations.

    PubMed

    Bieth, Marie; Lombaert, Hervé; Reader, Andrew J; Siddiqi, Kaleem

    2013-01-01

    A novel dynamic (4D) PET to PET image registration procedure is proposed and applied to multiple PET scans acquired with the high resolution research tomograph (HRRT), the highest resolution human brain PET scanner available in the world. By extending the recent diffeomorphic log-demons (DLD) method and applying it to multiple dynamic [11C]raclopride scans from the HRRT, an important step towards construction of a PET atlas of unprecedented quality for [11C]raclopride imaging of the human brain has been achieved. Accounting for the temporal dimension in PET data improves registration accuracy when compared to registration of 3D to 3D time-averaged PET images. The DLD approach was chosen for its ease in providing both an intensity and shape template, through iterative sequential pair-wise registrations with fast convergence. The proposed method is applicable to any PET radiotracer, providing 4D atlases with useful applications in high accuracy PET data simulations and automated PET image analysis. PMID:24579121

  12. 488-4D ASH LANDFILL CLOSURE CAP HELP MODELING

    SciTech Connect

    Phifer, M.

    2014-11-17

    At the request of Area Completion Projects (ACP) in support of the 488-4D Landfill closure, the Savannah River National Laboratory (SRNL) has performed Hydrologic Evaluation of Landfill Performance (HELP) modeling of the planned 488-4D Ash Landfill closure cap to ensure that the South Carolina Department of Health and Environmental Control (SCDHEC) limit of no more than 12 inches of head on top of the barrier layer (saturated hydraulic conductivity of no more than 1.0E-05 cm/s) in association with a 25-year, 24-hour storm event is not projected to be exceeded. Based upon Weber 1998 a 25-year, 24-hour storm event at the Savannah River Site (SRS) is 6.1 inches. The results of the HELP modeling indicate that the greatest peak daily head on top of the barrier layer (i.e. geosynthetic clay liner (GCL) or high density polyethylene (HDPE) geomembrane) for any of the runs made was 0.079 inches associated with a peak daily precipitation of 6.16 inches. This is well below the SCDHEC limit of 12 inches.

  13. 4D Dynamic Required Navigation Performance Final Report

    NASA Technical Reports Server (NTRS)

    Finkelsztein, Daniel M.; Sturdy, James L.; Alaverdi, Omeed; Hochwarth, Joachim K.

    2011-01-01

    New advanced four dimensional trajectory (4DT) procedures under consideration for the Next Generation Air Transportation System (NextGen) require an aircraft to precisely navigate relative to a moving reference such as another aircraft. Examples are Self-Separation for enroute operations and Interval Management for in-trail and merging operations. The current construct of Required Navigation Performance (RNP), defined for fixed-reference-frame navigation, is not sufficiently specified to be applicable to defining performance levels of such air-to-air procedures. An extension of RNP to air-to-air navigation would enable these advanced procedures to be implemented with a specified level of performance. The objective of this research effort was to propose new 4D Dynamic RNP constructs that account for the dynamic spatial and temporal nature of Interval Management and Self-Separation, develop mathematical models of the Dynamic RNP constructs, "Required Self-Separation Performance" and "Required Interval Management Performance," and to analyze the performance characteristics of these air-to-air procedures using the newly developed models. This final report summarizes the activities led by Raytheon, in collaboration with GE Aviation and SAIC, and presents the results from this research effort to expand the RNP concept to a dynamic 4D frame of reference.

  14. Complete valvular heart apparatus model from 4D cardiac CT.

    PubMed

    Grbic, Sasa; Ionasec, Razvan; Vitanovski, Dime; Voigt, Ingmar; Wang, Yang; Georgescu, Bogdan; Navab, Nassir; Comaniciu, Dorin

    2012-07-01

    The cardiac valvular apparatus, composed of the aortic, mitral, pulmonary and tricuspid valves, is an essential part of the anatomical, functional and hemodynamic characteristics of the heart and the cardiovascular system as a whole. Valvular heart diseases often involve multiple dysfunctions and require joint assessment and therapy of the valves. In this paper, we propose a complete and modular patient-specific model of the cardiac valvular apparatus estimated from 4D cardiac CT data. A new constrained Multi-linear Shape Model (cMSM), conditioned by anatomical measurements, is introduced to represent the complex spatio-temporal variation of the heart valves. The cMSM is exploited within a learning-based framework to efficiently estimate the patient-specific valve parameters from cine images. Experiments on 64 4D cardiac CT studies demonstrate the performance and clinical potential of the proposed method. Our method enables automatic quantitative evaluation of the complete valvular apparatus based on non-invasive imaging techniques. In conjunction with existent patient-specific chamber models, the presented valvular model enables personalized computation modeling and realistic simulation of the entire cardiac system.

  15. A VUV photoionization measurement and ab-initio calculation of the ionization energy of gas phase SiO2

    SciTech Connect

    Kostko, Oleg; Ahmed, Musahid; Metz, Ricardo B.

    2008-12-05

    In this work we report on the detection and vacuum-ultraviolet (VUV) photoionization of gas phase SiO2 generated in situ via laser ablation of silicon in a CO2 molecular beam. The resulting species are investigated by single photon ionization with tunable VUV synchrotron radiation and mass analyzed using reflectron mass spectrometry. Photoionization efficiency (PIE) curves are recorded for SiO and SiO2 and ionization energy estimates are revealed from such measurements. A state-to-state ionizationenergy of 12.60 (+-0.05) eV is recorded by fitting two prominent peaks in the PIE curve for the following process: 1SUM O-Si-O --> 2PRODg [O-Si-O]+. Electronic structure calculations aid in the interpretation of the photoionization process and allow for identification of the symmetric stretch of 2PRODg [O-Si-O]+ which is observed in the PIE spectrum to be 0.11 eV (890 cm-1) above the ground state of the cation and agrees with the 892 cm-1 symmetric stretch frequency calculated at the CCSD(T)/aug-cc-pVTZ level.

  16. The Iron Project & Iron Opacity Project: Updates on Photoionization, Electron-Ion Recombination of Fe XVII and Ca XV

    NASA Astrophysics Data System (ADS)

    Eissner, W.; Nahar, S.; Pradhan, A.; Hala, H.; Zhao, L.; Bailey, J.

    2016-05-01

    We have carried out converged close coupling (CCC) calculations for photoionization of Ne-like Fe XVII and demonstrate orders-of-magnitude enhancements in cross section due to successive core excitations. Convergence criteria are: (i) inclusion of sufficient number of residual ion Fe XVIII core states and (ii) high-resolution of myriad autoionizing resonances. We discuss verification of the conventional oscillator strength sum-rule in limited energy regions for bound-free plasma opacity. We will also report preliminary results from a larger R-matrix calculations of photoionization cross sections and electron-ion recombination rates of Ca XV where Rydberg series of resonances are included for core excitations to 28 states of n=2,3 complexes in contrast to previous 7 states of n=2 complex. The new results show existence of high-peak resonances of n=3 complex and enhanced background in high energy photoionization and a corresponding enhancement in the recombination in the high temperature region. Partial support: NSF, DOE, Ohio Supercomputer Center.

  17. Highly excited core resonances in photoionization of Fe xvii: Implications for plasma opacities

    SciTech Connect

    Nahar, Sultana N.; Pradhan, Anil K.; Chen Guoxin; Eissner, Werner

    2011-05-15

    A comprehensive study of high-accuracy photoionization cross sections is carried out using the relativistic Breit-Pauli R-matrix (BPRM) method for (h{nu}+Fe xvii {yields} Fe xviii +e). Owing to its importance in high-temperature plasmas, the calculations cover a large energy range, particularly the myriad photoexcitation-of-core (PEC) resonances including the n=3 levels not heretofore considered. The calculations employ a close-coupling wave-function expansion of 60 levels of the core ion Fe xviii ranging over a wide energy range of nearly 900 eV between the n=2 and n=3 levels. Strong-coupling effects due to dipole transition arrays 2p{sup 5}{yields}2p{sup 4}(3s,3d) manifest themselves as large PEC resonances throughout this range and enhance the effective photoionization cross sections orders of magnitude above the background. Comparisons with the erstwhile Opacity Project (OP) and other previous calculations show that the currently available cross sections considerably underestimate the bound-free cross sections. A level-identification scheme is used for spectroscopic designation of the 454 bound fine structure levels of Fe xvii, with n{<=}10, l{<=}9, and 0{<=}J{<=}8 of even and odd parities, obtained using the ab initio BPRM method (compared to 181 LS bound states in the OP work). The calculated energies are compared with those available from the National Institute for Standards and Technology database, which lists 63 levels with very good agreement. Level-specific photoionization cross sections are computed for all levels. In addition, partial cross sections for leaving the core ion Fe xvii in the ground state are also obtained. These results should be relevant to modeling of astrophysical and laboratory plasma sources requiring (i) photoionization rates, (ii) extensive nonlocal-thermodynamic-equilibrium models, (iii) total unified electron-ion recombination rates including radiative and dielectronic recombination, and (iv) plasma opacities. We particularly

  18. Modeling the heating and atomic kinetics of a photoionized neon plasma experiment

    NASA Astrophysics Data System (ADS)

    Lockard, Tom E.

    Motivated by gas cell photoionized plasma experiments performed by our group at the Z facility of Sandia National Laboratories, we discuss in this dissertation a modeling study of the heating and ionization of the plasma for conditions characteristic of these experiments. Photoionized plasmas are non-equilibrium systems driven by a broadband x-ray radiation flux. They are commonly found in astrophysics but rarely seen in the laboratory. Several modeling tools have been employed: (1) a view-factor computer code constrained with side x-ray power and gated monochromatic image measurements of the z-pinch radiation, to model the time-history of the photon-energy resolved x-ray flux driving the photoionized plasma, (2) a Boltzmann self-consistent electron and atomic kinetics model to simulate the electron distribution function and configuration-averaged atomic kinetics, (3) a radiation-hydrodynamics code with inline non-equilibrium atomic kinetics to perform a comprehensive numerical simulation of the experiment and plasma heating, and (4) steady-state and time-dependent collisional-radiative atomic kinetics calculations with fine-structure energy level description to assess transient effects in the ionization and charge state distribution of the plasma. The results indicate that the photon-energy resolved x-ray flux impinging on the front window of the gas cell is very well approximated by a linear combination of three geometrically-diluted Planckian distributions. Knowledge of the spectral details of the x-ray drive turned out to be important for the heating and ionization of the plasma. The free electrons in the plasma thermalize quickly relative to the timescales associated with the time-history of the x-ray drive and the plasma atomic kinetics. Hence, electrons are well described by a Maxwellian energy distribution of a single temperature. This finding is important to support the application of a radiation-hydrodynamic model to simulate the experiment. It is found

  19. Improved design for the atmospheric pressure photoionization source.

    PubMed

    Tabrizchi, Mahmoud; Bahrami, Hamed

    2011-12-01

    A different design for the atmospheric pressure photoionization (APPI) source, other than commercially available sources, such as PhotoSpray and PhotoMate, has been proposed. Unlike PhotoSpray, this design applies an electric field to separate photoions and electrons. In addition, the UV radiation is parallel to the gas stream toward the mass spectrometer sampling aperture. The total ion current obtained using this geometry, for dopant only, could be an order of magnitude larger than that obtained using the PhotoSpray design. Additionally, to prevent the negative effect of solvent on the photoionization yield, a curtain electrode was mounted in front of the UV lamp to divide the ionization zone into two distinct regions: the dopant and the solvent regions. Dopant was introduced in the vicinity of the lamp, and vaporized solvent was introduced into the solvent region. The curtain electrode prevented the solvent from entering the dopant region where dopant was directly photoionized. This design consumes much less dopant (approximately 1/10 less) than the conventional source, which minimizes the presence of photofragmented radicals and dopant trace contaminants in the ionization region. As a result, unlike PhotoSpray, the mass spectra contained mainly the analyte and solvent peaks. Additionally, the source was tested using an ion mobility spectrometer (IMS). The effect of the curtain electrode on signal intensity and performance of the source using IMS was also proved to be positive. PMID:22017507

  20. Model-driven physiological assessment of the mitral valve from 4D TEE

    NASA Astrophysics Data System (ADS)

    Voigt, Ingmar; Ionasec, Razvan Ioan; Georgescu, Bogdan; Houle, Helene; Huber, Martin; Hornegger, Joachim; Comaniciu, Dorin

    2009-02-01

    Disorders of the mitral valve are second most frequent, cumulating 14 percent of total number of deaths caused by Valvular Heart Disease each year in the United States and require elaborate clinical management. Visual and quantitative evaluation of the valve is an important step in the clinical workflow according to experts as knowledge about mitral morphology and dynamics is crucial for interventional planning. Traditionally this involves examination and metric analysis of 2D images comprising potential errors being intrinsic to the method. Recent commercial solutions are limited to specific anatomic components, pathologies and a single phase of cardiac 4D acquisitions only. This paper introduces a novel approach for morphological and functional quantification of the mitral valve based on a 4D model estimated from ultrasound data. A physiological model of the mitral valve, covering the complete anatomy and eventual shape variations, is generated utilizing parametric spline surfaces constrained by topological and geometrical prior knowledge. The 4D model's parameters are estimated for each patient using the latest discriminative learning and incremental searching techniques. Precise evaluation of the anatomy using model-based dynamic measurements and advanced visualization are enabled through the proposed approach in a reliable, repeatable and reproducible manner. The efficiency and accuracy of the method is demonstrated through experiments and an initial validation based on clinical research results. To the best of our knowledge this is the first time such a patient specific 4D mitral valve model is proposed, covering all of the relevant anatomies and enabling to model the common pathologies at once.

  1. The fingerprints of photoionization and shock-ionization in two CSS sources

    NASA Astrophysics Data System (ADS)

    Reynaldi, Victoria; Feinstein, Carlos

    2016-01-01

    We investigate the ionization state of the extended emission-line regions (EELRs) around two compact steep-spectrum (CSS) radio galaxies, 3C 268.3 and 3C 303.1, in order to identify the contribution of photoionization and shock-ionization. We perform a new spectroscopical (long-slit) analysis with GMOS/Gemini with the slit oriented in the radio-jet direction, where outflows are known to exist. The [Ne V] λ3426 emission is the most interesting feature of the spectra and the one key to breaking the degeneracy between the models: since this emission-line is more extended than He II, it challenges the ionization structure proposed by any photoionization model, also its intensity relative to H β does not behave as expected with respect to the ionization parameter U in the same scenario. On the contrary, when it is compared to the intensity of [O II] λ3727/H β and all these results are joined, the whole scenario is plausible to be explained as emission coming from the hot, compressed, shocked gas in shock-ionization models. Although the model fitting is strongly sensitive to the chosen line ratios, it argues for the presence of external and strong ionizing fields, such as the precursor field created by the shock or/and the AGN radiation field. In this paper, we show how AGN photoionization and shock-ionization triggered by jet-cloud interaction work together in these EELRs in order to explain the observed trends and line-ratio behaviours in a kinematically acceptable way.

  2. Photodissociation and photoionization of organosulfur radicals

    SciTech Connect

    Hsu, Chia-Wei

    1994-05-27

    The dynamics of S({sup 3}P{sub 2,1,0}, {sup 1}D{sub 2}) production from the 193 nm photodissociation of CH{sub 3}SCH{sub 3}, H{sub 2}S and CH{sub 3}SH have been studied using 2 + 1 resonance-enhanced multiphoton ionization (REMPI) techniques. The 193 nm photodissociation cross sections for the formation of S from CH{sub 3}S and HS initially prepared in the photodissociation of CH{sub 3}SCH{sub 3} and H{sub 2}S are estimated to be 1 {times} 10{sup {minus}18} and 1.1 {times} 10{sup {minus}18} cm{sup 2}, respectively. The dominant product from CH{sub 3}S is S({sup 1}D), while that from SH is S({sup 3}P). Possible potential energy surfaces involved in the 193 nm photodissociation of CH{sub 3}S({tilde X}) and SH(X) have been also examined. Threshold photoelectron (PE) spectra for SH and CH{sub 3}S formed in the ultraviolet photodissociation of H{sub 2}S and CH{sub 3}SH, respectively, have been measured using the nonresonant two-photon pulsed field ionization (N2P-PFI) technique. The rotationally resolved N2P-PFI-PE spectrum obtained for SH indicates that photoionization dynamics favors the rotational angular momentum change {Delta}N < 0 with the {Delta}N value up to {minus}3, an observation similar to that found in the PFI-PE spectra of OH (OD) and NO. The ionization energies for SH(X{sup 2}{product}{sub 3,2}) and CH{sub 3}S({tilde X}{sup 2}E{sub 3/2}) are determined to be 84,057.5 {plus_minus} 3 cm{sup {minus}1} and 74,726 {plus_minus} 8 cm{sup {minus}1} respectively. The spin-orbit splittings for SH(X{sup 2}{product}{sub 3/2,1/2}) and CH{sub 3}S({tilde X}{sup 2}E{sub 3/2,1/2}) are found to be 377 {plus_minus} 2 and 257 {plus_minus} 5 cm{sup {minus}1}, respectively, in agreement with previous measurements. The C-S stretching frequency for CH{sub 3}S{sup +}({tilde X}{sup 3}A{sub 2}) is 733 {plus_minus} 5 cm{sup {minus}1}. This study illustrates that the PFI-PE detection method can be a sensitive probe for the nascent internal energy distribution of photoproducts.

  3. 4D XCAT phantom for multimodality imaging research

    SciTech Connect

    Segars, W. P.; Sturgeon, G.; Mendonca, S.; Grimes, Jason; Tsui, B. M. W.

    2010-09-15

    Purpose: The authors develop the 4D extended cardiac-torso (XCAT) phantom for multimodality imaging research. Methods: Highly detailed whole-body anatomies for the adult male and female were defined in the XCAT using nonuniform rational B-spline (NURBS) and subdivision surfaces based on segmentation of the Visible Male and Female anatomical datasets from the National Library of Medicine as well as patient datasets. Using the flexibility of these surfaces, the Visible Human anatomies were transformed to match body measurements and organ volumes for a 50th percentile (height and weight) male and female. The desired body measurements for the models were obtained using the PEOPLESIZE program that contains anthropometric dimensions categorized from 1st to the 99th percentile for US adults. The desired organ volumes were determined from ICRP Publication 89 [ICRP, ''Basic anatomical and physiological data for use in radiological protection: reference values,'' ICRP Publication 89 (International Commission on Radiological Protection, New York, NY, 2002)]. The male and female anatomies serve as standard templates upon which anatomical variations may be modeled in the XCAT through user-defined parameters. Parametrized models for the cardiac and respiratory motions were also incorporated into the XCAT based on high-resolution cardiac- and respiratory-gated multislice CT data. To demonstrate the usefulness of the phantom, the authors show example simulation studies in PET, SPECT, and CT using publicly available simulation packages. Results: As demonstrated in the pilot studies, the 4D XCAT (which includes thousands of anatomical structures) can produce realistic imaging data when combined with accurate models of the imaging process. With the flexibility of the NURBS surface primitives, any number of different anatomies, cardiac or respiratory motions or patterns, and spatial resolutions can be simulated to perform imaging research. Conclusions: With the ability to produce

  4. 4D Light Field Imaging System Using Programmable Aperture

    NASA Technical Reports Server (NTRS)

    Bae, Youngsam

    2012-01-01

    Complete depth information can be extracted from analyzing all angles of light rays emanated from a source. However, this angular information is lost in a typical 2D imaging system. In order to record this information, a standard stereo imaging system uses two cameras to obtain information from two view angles. Sometimes, more cameras are used to obtain information from more angles. However, a 4D light field imaging technique can achieve this multiple-camera effect through a single-lens camera. Two methods are available for this: one using a microlens array, and the other using a moving aperture. The moving-aperture method can obtain more complete stereo information. The existing literature suggests a modified liquid crystal panel [LC (liquid crystal) panel, similar to ones commonly used in the display industry] to achieve a moving aperture. However, LC panels cannot withstand harsh environments and are not qualified for spaceflight. In this regard, different hardware is proposed for the moving aperture. A digital micromirror device (DMD) will replace the liquid crystal. This will be qualified for harsh environments for the 4D light field imaging. This will enable an imager to record near-complete stereo information. The approach to building a proof-ofconcept is using existing, or slightly modified, off-the-shelf components. An SLR (single-lens reflex) lens system, which typically has a large aperture for fast imaging, will be modified. The lens system will be arranged so that DMD can be integrated. The shape of aperture will be programmed for single-viewpoint imaging, multiple-viewpoint imaging, and coded aperture imaging. The novelty lies in using a DMD instead of a LC panel to move the apertures for 4D light field imaging. The DMD uses reflecting mirrors, so any light transmission lost (which would be expected from the LC panel) will be minimal. Also, the MEMS-based DMD can withstand higher temperature and pressure fluctuation than a LC panel can. Robotics need

  5. 4D XCAT phantom for multimodality imaging research

    PubMed Central

    Segars, W. P.; Sturgeon, G.; Mendonca, S.; Grimes, Jason; Tsui, B. M. W.

    2010-01-01

    Purpose: The authors develop the 4D extended cardiac-torso (XCAT) phantom for multimodality imaging research. Methods: Highly detailed whole-body anatomies for the adult male and female were defined in the XCAT using nonuniform rational B-spline (NURBS) and subdivision surfaces based on segmentation of the Visible Male and Female anatomical datasets from the National Library of Medicine as well as patient datasets. Using the flexibility of these surfaces, the Visible Human anatomies were transformed to match body measurements and organ volumes for a 50th percentile (height and weight) male and female. The desired body measurements for the models were obtained using the PEOPLESIZE program that contains anthropometric dimensions categorized from 1st to the 99th percentile for US adults. The desired organ volumes were determined from ICRP Publication 89 [ICRP, ‘‘Basic anatomical and physiological data for use in radiological protection: reference values,” ICRP Publication 89 (International Commission on Radiological Protection, New York, NY, 2002)]. The male and female anatomies serve as standard templates upon which anatomical variations may be modeled in the XCAT through user-defined parameters. Parametrized models for the cardiac and respiratory motions were also incorporated into the XCAT based on high-resolution cardiac- and respiratory-gated multislice CT data. To demonstrate the usefulness of the phantom, the authors show example simulation studies in PET, SPECT, and CT using publicly available simulation packages. Results: As demonstrated in the pilot studies, the 4D XCAT (which includes thousands of anatomical structures) can produce realistic imaging data when combined with accurate models of the imaging process. With the flexibility of the NURBS surface primitives, any number of different anatomies, cardiac or respiratory motions or patterns, and spatial resolutions can be simulated to perform imaging research. Conclusions: With the ability to produce

  6. Semaphorin 4D Contributes to Rheumatoid Arthritis by Inducing Inflammatory Cytokine Production: Pathogenic and Therapeutic Implications

    PubMed Central

    Yoshida, Yuji; Kang, Sujin; Ebina, Kousuke; Shi, Kenrin; Nojima, Satoshi; Kimura, Tetsuya; Ito, Daisuke; Morimoto, Keiko; Nishide, Masayuki; Hosokawa, Takashi; Hirano, Toru; Shima, Yoshihito; Narazaki, Masashi; Tsuboi, Hideki; Saeki, Yukihiko; Tomita, Tetsuya; Tanaka, Toshio; Kumanogoh, Atsushi

    2015-01-01

    Objective Semaphorin 4D (Sema4D)/CD100 has pleiotropic roles in immune activation, angiogenesis, bone metabolism, and neural development. We undertook this study to investigate the role of Sema4D in rheumatoid arthritis (RA). Methods Soluble Sema4D (sSema4D) levels in serum and synovial fluid were analyzed by enzyme‐linked immunosorbent assay. Cell surface expression and transcripts of Sema4D were analyzed in peripheral blood cells from RA patients, and immunohistochemical staining of Sema4D was performed in RA synovium. Generation of sSema4D was evaluated in an ADAMTS‐4–treated monocytic cell line (THP‐1 cells). The efficacy of anti‐Sema4D antibody was evaluated in mice with collagen‐induced arthritis (CIA). Results Levels of sSema4D were elevated in both serum and synovial fluid from RA patients, and disease activity markers were correlated with serum sSema4D levels. Sema4D‐expressing cells also accumulated in RA synovium. Cell surface levels of Sema4D on CD3+ and CD14+ cells from RA patients were reduced, although levels of Sema4D transcripts were unchanged. In addition, ADAMTS‐4 cleaved cell surface Sema4D to generate sSema4D in THP‐1 cells. Soluble Sema4D induced tumor necrosis factor α (TNFα) and interleukin‐6 (IL‐6) production from CD14+ monocytes. IL‐6 and TNFα induced ADAMTS‐4 expression in synovial cells. Treatment with an anti‐Sema4D antibody suppressed arthritis and reduced proinflammatory cytokine production in CIA. Conclusion A positive feedback loop involving sSema4D/IL‐6 and TNFα/ADAMTS‐4 may contribute to the pathogenesis of RA. The inhibition of arthritis by anti‐Sema4D antibody suggests that Sema4D represents a potential therapeutic target for RA. PMID:25707877

  7. R-matrix calculations of the photoionization cross-sections of Ti2+

    NASA Astrophysics Data System (ADS)

    Gao, J. W.; Han, X. Y.; Wang, J. G.; Li, J. M.

    2015-11-01

    The photoionization cross-sections of Ti2+ in the ground state ([Ne]3s23p63d2 3Fe) are calculated using both non-relativistic (LS-coupling) and relativistic (Breit-Pauli) R-matrix methods for the photon energy from 27.49 eV (I.P.) to 48.00 eV. The results show that, in this energy range, the photoionization cross-sections are dominated by resonances 3p53d3, 3p53d24d and 3p53d24s, which are labelled by LS-terms by combining with the multiconfiguration Dirac-Fock calculations. Moreover, from the fractional parentage coefficients and the percentages (the square of the configuration interaction expansion coefficients) of the LS-terms involved in the final resonance states, the relative strength of the resonances have been explained qualitatively in a general way. The present results should be of great help in the modelling and diagnostic of astrophysical plasmas as well as laboratory plasmas.

  8. Mapping motion from 4D-MRI to 3D-CT for use in 4D dose calculations: A technical feasibility study

    SciTech Connect

    Boye, Dirk; Lomax, Tony; Knopf, Antje

    2013-06-15

    Purpose: Target sites affected by organ motion require a time resolved (4D) dose calculation. Typical 4D dose calculations use 4D-CT as a basis. Unfortunately, 4D-CT images have the disadvantage of being a 'snap-shot' of the motion during acquisition and of assuming regularity of breathing. In addition, 4D-CT acquisitions involve a substantial additional dose burden to the patient making many, repeated 4D-CT acquisitions undesirable. Here the authors test the feasibility of an alternative approach to generate patient specific 4D-CT data sets. Methods: In this approach motion information is extracted from 4D-MRI. Simulated 4D-CT data sets [which the authors call 4D-CT(MRI)] are created by warping extracted deformation fields to a static 3D-CT data set. The employment of 4D-MRI sequences for this has the advantage that no assumptions on breathing regularity are made, irregularities in breathing can be studied and, if necessary, many repeat imaging studies (and consequently simulated 4D-CT data sets) can be performed on patients and/or volunteers. The accuracy of 4D-CT(MRI)s has been validated by 4D proton dose calculations. Our 4D dose algorithm takes into account displacements as well as deformations on the originating 4D-CT/4D-CT(MRI) by calculating the dose of each pencil beam based on an individual time stamp of when that pencil beam is applied. According to corresponding displacement and density-variation-maps the position and the water equivalent range of the dose grid points is adjusted at each time instance. Results: 4D dose distributions, using 4D-CT(MRI) data sets as input were compared to results based on a reference conventional 4D-CT data set capturing similar motion characteristics. Almost identical 4D dose distributions could be achieved, even though scanned proton beams are very sensitive to small differences in the patient geometry. In addition, 4D dose calculations have been performed on the same patient, but using 4D-CT(MRI) data sets based on

  9. Biomechanics of DNA structures visualized by 4D electron microscopy

    PubMed Central

    Lorenz, Ulrich J.; Zewail, Ahmed H.

    2013-01-01

    We present a technique for in situ visualization of the biomechanics of DNA structural networks using 4D electron microscopy. Vibrational oscillations of the DNA structure are excited mechanically through a short burst of substrate vibrations triggered by a laser pulse. Subsequently, the motion is probed with electron pulses to observe the impulse response of the specimen in space and time. From the frequency and amplitude of the observed oscillations, we determine the normal modes and eigenfrequencies of the structures involved. Moreover, by selective “nano-cutting” at a given point in the network, it was possible to obtain Young’s modulus, and hence the stiffness, of the DNA filament at that position. This experimental approach enables nanoscale mechanics studies of macromolecules and should find applications in other domains of biological networks such as origamis. PMID:23382239

  10. Myocardial motion and function assessment using 4D images

    NASA Astrophysics Data System (ADS)

    Shi, Peng-Cheng; Robinson, Glynn P.; Duncan, James S.

    1994-09-01

    This paper describes efforts aimed at more objectively and accurately quantifying the local, regional and global function of the left ventricle (LV) of the heart from 4D image data. Using our shape-based image analysis methods, point-wise myocardial motion vector fields between successive image frames through the entire cardiac cycle will be computed. Quantitative LV motion, thickening, and strain measurements will then be established from the point correspondence maps. In the paper, we will also briefly describe an in vivo experimental model which uses implanted imaging-opaque markers to validate the results of our image analysis methods. Finally, initial experimental results using image sequences from two different modalities will be presented.

  11. 4D GPR Experiments--Towards the Virtual Lysimeter

    NASA Astrophysics Data System (ADS)

    Grasmueck, M.; Viggiano, D. A.; Day-Lewis, F. D.; Drasdis, J. B.; Kruse, S. E.; Or, D.

    2006-05-01

    In-situ monitoring of infiltration, water flow and retention in the vadose zone currently rely primarily on invasive methods, which irreversibly disturb original soil structure and alter its hydrologic behavior in the vicinity of the measurement. For example, use of lysimeters requires extraction and repacking of soil samples, and time- domain reflectometry (TDR) requires insertion of probes into the soil profile. This study investigates the use of repeated high-density 3D ground penetrating radar surveys (also known as 4D GPR) as a non-invasive alternative for detailed visualization and quantification of water flow in the vadose zone. Evaluation of the 4D GPR method was based on a series of controlled point-source water injection experiments into undisturbed beach sand deposits at Crandon Park in Miami, Florida. The goal of the GPR surveys was to image the shape and evolution of a wet-bulb as it propagates from the injection points (~0.5 m) towards the water table at 2.2 m depth. The experimental design was guided by predictive modeling using Hydrus 2D and finite-difference GPR waveform codes. Input parameters for the modeling were derived from hydrologic and electromagnetic characterization of representative sand samples. Guided by modeling results, we injected 30 to 40 liters of tap water through plastic-cased boreholes with slotted bottom sections (0.1 m) located 0.4 to 0.6 m below the surface. During and after injection, an area of 25 m2 was surveyed every 20 minutes using 250 and 500 MHz antennas with a grid spacing of 0.05 x 0.025 m. A total of 20 3D GPR surveys were completed over 3 infiltration sites. To confirm wet-bulb shapes measured by GPR, we injected 2 liters of "brilliant blue" dye (~100 mg/l) along with a saline water tracer towards the end of one experiment. After completion of GPR scanning, a trench was excavated to examine the distribution of the saltwater and dye using TDR and visual inspection, respectively. Preliminary analysis of the 4D GPR

  12. Chaos in a 4D dissipative nonlinear fermionic model

    NASA Astrophysics Data System (ADS)

    Aydogmus, Fatma

    2015-12-01

    Gursey Model is the only possible 4D conformally invariant pure fermionic model with a nonlinear self-coupled spinor term. It has been assumed to be similar to the Heisenberg's nonlinear generalization of Dirac's equation, as a possible basis for a unitary description of elementary particles. Gursey Model admits particle-like solutions for the derived classical field equations and these solutions are instantonic in character. In this paper, the dynamical nature of damped and forced Gursey Nonlinear Differential Equations System (GNDES) are studied in order to get more information on spinor type instantons. Bifurcation and chaos in the system are observed by constructing the bifurcation diagrams and Poincaré sections. Lyapunov exponent and power spectrum graphs of GNDES are also constructed to characterize the chaotic behavior.

  13. Determination of photoionization branching ratios and total photoionization cross sections at 304 A from experimental ionospheric photoelectron fluxes

    NASA Technical Reports Server (NTRS)

    Richards, P. G.; Torr, D. G.; Espy, P. J.

    1982-01-01

    High-resolution measurements of the ionospheric photoelectron spectrum are used to derive photoionization cross sections and branching ratios for N2 and O at 304 A, the wavelength of the intense He II solar radiation. Based on a theory in which the measured fluxes at energies 22.5, 24.5, 25.5 and 27.5 eV are determined by the ratio of the production rate and the loss rate coefficient, values are obtained for the ratio of molecular nitrogen density to atomic oxygen density as a function of altitude, the sum of the total photoionization cross sections, the 2P/4S and 2D/4S branching ratios for O and the B/X and A/X branching ratios for N2 photoionization and the ratios and the interspecies cross section ratios 2D/A, 4S/X and 2P/B. The values obtained are in accord with the photoionization cross sections of Kirby et al. (1979).

  14. Photoionization of rotationally cooled H2O and D2O in the region 650-990 A

    NASA Astrophysics Data System (ADS)

    Dehmer, P. M.; Holland, D. M. P.

    1991-03-01

    Room temperature and rotationally cooled relative photoionization cross sections for H2O and D2O were determined in the wavelength region 650-990 A with a wavelength resolution of 0.06-0.11 A. The spectra were normalized to the absolute photoionization cross sections determined by Katayama et al. (1973) with lower resolution. A rotational analysis of the Pi subbands in the (0,6,0) and (0,8,0) bands of a Rydberg transition determined the symmetry of the upper state; in addition, the series was extended to higher principal quantum numbers. The analysis of these and other bands was made difficult both by the large natural linewidths of the rotational transitions and by the absence of transitions to rotational levels with N-prime above 3.

  15. Parallel Wavefront Analysis for a 4D Interferometer

    NASA Technical Reports Server (NTRS)

    Rao, Shanti R.

    2011-01-01

    This software provides a programming interface for automating data collection with a PhaseCam interferometer from 4D Technology, and distributing the image-processing algorithm across a cluster of general-purpose computers. Multiple instances of 4Sight (4D Technology s proprietary software) run on a networked cluster of computers. Each connects to a single server (the controller) and waits for instructions. The controller directs the interferometer to several images, then assigns each image to a different computer for processing. When the image processing is finished, the server directs one of the computers to collate and combine the processed images, saving the resulting measurement in a file on a disk. The available software captures approximately 100 images and analyzes them immediately. This software separates the capture and analysis processes, so that analysis can be done at a different time and faster by running the algorithm in parallel across several processors. The PhaseCam family of interferometers can measure an optical system in milliseconds, but it takes many seconds to process the data so that it is usable. In characterizing an adaptive optics system, like the next generation of astronomical observatories, thousands of measurements are required, and the processing time quickly becomes excessive. A programming interface distributes data processing for a PhaseCam interferometer across a Windows computing cluster. A scriptable controller program coordinates data acquisition from the interferometer, storage on networked hard disks, and parallel processing. Idle time of the interferometer is minimized. This architecture is implemented in Python and JavaScript, and may be altered to fit a customer s needs.

  16. Inner-shell photoionization and core-hole decay of Xe and XeF{sub 2}

    SciTech Connect

    Southworth, Stephen H.; Picón, Antonio; Lehmann, C. Stefan; Wehlitz, Ralf; Cheng, Lan; Stanton, John F.

    2015-06-14

    Photoionization cross sections and partial ion yields of Xe and XeF{sub 2} from Xe 3d{sub 5/2}, Xe 3d{sub 3/2}, and F 1s subshells in the 660–740 eV range are compared to explore effects of the F ligands. The Xe 3d-ϵf continuum shape resonances dominate the photoionization cross sections of both the atom and molecule, but prominent resonances appear in the XeF{sub 2} cross section due to nominal excitation of Xe 3d and F 1s electrons to the lowest unoccupied molecular orbital (LUMO), a delocalized anti-bonding MO. Comparisons of the ion products from the atom and molecule following Xe 3d photoionization show that the charge-state distribution of Xe ions is shifted to lower charge states in the molecule along with production of energetic F{sup +} and F{sup 2+} ions. This suggests that, in decay of a Xe 3d core hole, charge is redistributed to the F ligands and the system dissociates due to Coulomb repulsion. The ion products from excitation of the F 1s-LUMO resonance are different and show strong increases in the yields of Xe{sup +} and F{sup +} ions. The subshell ionization thresholds, the LUMO resonance energies, and their oscillator strengths are calculated by relativistic coupled-cluster methods and agree well with measurements.

  17. VUV photoionization and dissociative photoionization of the prebiotic molecule acetyl cyanide: theory and experiment.

    PubMed

    Bellili, A; Schwell, M; Bénilan, Y; Fray, N; Gazeau, M-C; Mogren Al-Mogren, M; Guillemin, J-C; Poisson, L; Hochlaf, M

    2014-10-01

    The present combined theoretical and experimental investigation concerns the single photoionization of gas-phase acetyl cyanide and the fragmentation pathways of the resulting cation. Acetyl cyanide (AC) is inspired from both the chemistry of cyanoacetylene and the Strecker reaction which are thought to be at the origin of medium sized prebiotic molecules in the interstellar medium. AC can be formed by reaction from cyanoacetylene and water but also from acetaldehyde and HCN or the corresponding radicals. In view of the interpretation of vacuum ultraviolet (VUV) experimental data obtained using synchrotron radiation, we explored the ground potential energy surface (PES) of acetyl cyanide and of its cation using standard and recently implemented explicitly correlated methodologies. Our PES covers the regions of tautomerism (between keto and enol forms) and of the lowest fragmentation channels. This allowed us to deduce accurate thermochemical data for this astrobiologically relevant molecule. Unimolecular decomposition of the AC cation turns out to be very complex. The implications for the evolution of prebiotic molecules under VUV irradiation are discussed.

  18. VUV photoionization and dissociative photoionization of the prebiotic molecule acetyl cyanide: Theory and experiment

    NASA Astrophysics Data System (ADS)

    Bellili, A.; Schwell, M.; Bénilan, Y.; Fray, N.; Gazeau, M.-C.; Mogren Al-Mogren, M.; Guillemin, J.-C.; Poisson, L.; Hochlaf, M.

    2014-10-01

    The present combined theoretical and experimental investigation concerns the single photoionization of gas-phase acetyl cyanide and the fragmentation pathways of the resulting cation. Acetyl cyanide (AC) is inspired from both the chemistry of cyanoacetylene and the Strecker reaction which are thought to be at the origin of medium sized prebiotic molecules in the interstellar medium. AC can be formed by reaction from cyanoacetylene and water but also from acetaldehyde and HCN or the corresponding radicals. In view of the interpretation of vacuum ultraviolet (VUV) experimental data obtained using synchrotron radiation, we explored the ground potential energy surface (PES) of acetyl cyanide and of its cation using standard and recently implemented explicitly correlated methodologies. Our PES covers the regions of tautomerism (between keto and enol forms) and of the lowest fragmentation channels. This allowed us to deduce accurate thermochemical data for this astrobiologically relevant molecule. Unimolecular decomposition of the AC cation turns out to be very complex. The implications for the evolution of prebiotic molecules under VUV irradiation are discussed.

  19. VUV photoionization and dissociative photoionization of the prebiotic molecule acetyl cyanide: Theory and experiment

    SciTech Connect

    Bellili, A.; Hochlaf, M. E-mail: martin.schwell@lisa.u-pec.fr; Schwell, M. E-mail: martin.schwell@lisa.u-pec.fr; Bénilan, Y.; Fray, N.; Gazeau, M.-C.; Mogren Al-Mogren, M.; Guillemin, J.-C.; Poisson, L.

    2014-10-07

    The present combined theoretical and experimental investigation concerns the single photoionization of gas-phase acetyl cyanide and the fragmentation pathways of the resulting cation. Acetyl cyanide (AC) is inspired from both the chemistry of cyanoacetylene and the Strecker reaction which are thought to be at the origin of medium sized prebiotic molecules in the interstellar medium. AC can be formed by reaction from cyanoacetylene and water but also from acetaldehyde and HCN or the corresponding radicals. In view of the interpretation of vacuum ultraviolet (VUV) experimental data obtained using synchrotron radiation, we explored the ground potential energy surface (PES) of acetyl cyanide and of its cation using standard and recently implemented explicitly correlated methodologies. Our PES covers the regions of tautomerism (between keto and enol forms) and of the lowest fragmentation channels. This allowed us to deduce accurate thermochemical data for this astrobiologically relevant molecule. Unimolecular decomposition of the AC cation turns out to be very complex. The implications for the evolution of prebiotic molecules under VUV irradiation are discussed.

  20. Multiyear climate prediction with initialization based on 4D-Var data assimilation

    NASA Astrophysics Data System (ADS)

    Mochizuki, Takashi; Masuda, Shuhei; Ishikawa, Yoichi; Awaji, Toshiyuki

    2016-04-01

    An initialization relevant to interannual-to-decadal climate prediction has usually used a simple restoring approach for oceanic variables. Here we demonstrate the potential use of four-dimensional variational (4D-Var) data assimilation on the leading edge of initialization approach particularly in multiyear (5 year long) climate prediction. We perform full-field initialization rather than anomaly initialization and assimilate the atmosphere states together with the ocean states to an atmosphere-ocean coupled climate model. In particular, it is noteworthy that ensembles of multiyear hindcasts using our assimilation results as initial conditions exhibit an improved skill in hindcasting the multiyear changes of the upper ocean heat content (OHC) over the central North Pacific. The 4D-Var approach enables us to directly assimilate a time trajectory of slow changes of the Aleutian Low that are compatible with the sea surface height and the OHC. Consequently, we can estimate a coupled climate state suitable for hindcasting dynamical changes over the extratropical North Pacific as observed.

  1. Near-threshold photoelectron angular distributions from two-photon resonant photoionization of He

    NASA Astrophysics Data System (ADS)

    O'Keeffe, P.; Mihelič, A.; Bolognesi, P.; Žitnik, M.; Moise, A.; Richter, R.; Avaldi, L.

    2013-01-01

    Two-photon resonant photoionization of helium is investigated both experimentally and theoretically. Ground state helium atoms are excited to the 1s4p, 1s5p and 1s6p 1P states by synchrotron radiation and ionized by a synchronized infrared pulsed picosecond laser. The photoelectron angular distributions of the emitted electrons are measured using a velocity map imaging (VMI) spectrometer. The measured asymmetry parameters of the angular distribution allow the phase differences and the ratios of the dipole matrix elements of the 1sɛs and 1sɛd channels to be determined. The experimental results agree with the calculated values obtained in a configuration-interaction calculation with a Coulomb-Sturmian basis set. The effects of the radiative decay of the intermediate state and the static electric field of the VMI spectrometer on the measurements are discussed.

  2. Respiratory triggered 4D cone-beam computed tomography: A novel method to reduce imaging dose

    PubMed Central

    Cooper, Benjamin J.; O’Brien, Ricky T.; Balik, Salim; Hugo, Geoffrey D.; Keall, Paul J.

    2013-01-01

    Purpose: A novel method called respiratory triggered 4D cone-beam computed tomography (RT 4D CBCT) is described whereby imaging dose can be reduced without degrading image quality. RT 4D CBCT utilizes a respiratory signal to trigger projections such that only a single projection is assigned to a given respiratory bin for each breathing cycle. In contrast, commercial 4D CBCT does not actively use the respiratory signal to minimize image dose. Methods: To compare RT 4D CBCT with conventional 4D CBCT, 3600 CBCT projections of a thorax phantom were gathered and reconstructed to generate a ground truth CBCT dataset. Simulation pairs of conventional 4D CBCT acquisitions and RT 4D CBCT acquisitions were developed assuming a sinusoidal respiratory signal which governs the selection of projections from the pool of 3600 original projections. The RT 4D CBCT acquisition triggers a single projection when the respiratory signal enters a desired acquisition bin; the conventional acquisition does not use a respiratory trigger and projections are acquired at a constant frequency. Acquisition parameters studied were breathing period, acquisition time, and imager frequency. The performance of RT 4D CBCT using phase based and displacement based sorting was also studied. Image quality was quantified by calculating difference images of the test dataset from the ground truth dataset. Imaging dose was calculated by counting projections. Results: Using phase based sorting RT 4D CBCT results in 47% less imaging dose on average compared to conventional 4D CBCT. Image quality differences were less than 4% at worst. Using displacement based sorting RT 4D CBCT results in 57% less imaging dose on average, than conventional 4D CBCT methods; however, image quality was 26% worse with RT 4D CBCT. Conclusions: Simulation studies have shown that RT 4D CBCT reduces imaging dose while maintaining comparable image quality for phase based 4D CBCT; image quality is degraded for displacement based RT 4D

  3. Parallel Infrastructure Modeling and Inversion Module for E4D

    SciTech Connect

    2014-10-09

    Electrical resistivity tomography ERT is a method of imaging the electrical conductivity of the subsurface. Electrical conductivity is a useful metric for understanding the subsurface because it is governed by geomechanical and geochemical properties that drive subsurface systems. ERT works by injecting current into the subsurface across a pair of electrodes, and measuring the corresponding electrical potential response across another pair of electrodes. Many such measurements are strategically taken across an array of electrodes to produce an ERT data set. These data are then processed through a computationally demanding process known as inversion to produce an image of the subsurface conductivity structure that gave rise to the measurements. Data can be inverted to provide 2D images, 3D images, or in the case of time-lapse 3D imaging, 4D images. ERT is generally not well suited for environments with buried electrically conductive infrastructure such as pipes, tanks, or well casings, because these features tend to dominate and degrade ERT images. This reduces or eliminates the utility of ERT imaging where it would otherwise be highly useful for, for example, imaging fluid migration from leaking pipes, imaging soil contamination beneath leaking subusurface tanks, and monitoring contaminant migration in locations with dense network of metal cased monitoring wells. The location and dimension of buried metallic infrastructure is often known. If so, then the effects of the infrastructure can be explicitly modeled within the ERT imaging algorithm, and thereby removed from the corresponding ERT image. However,there are a number of obstacles limiting this application. 1) Metallic infrastructure cannot be accurately modeled with standard codes because of the large contrast in conductivity between the metal and host material. 2) Modeling infrastructure in true dimension requires the computational mesh to be highly refined near the metal inclusions, which increases

  4. Comment on "Test of the Stark-effect theory using photoionization microscopy"

    NASA Astrophysics Data System (ADS)

    Giannakeas, P.; Robicheaux, F.; Greene, Chris H.

    2015-06-01

    An article by Zhao et al. [Phys. Rev. A 86, 053413 (2012), 10.1103/PhysRevA.86.053413] tests the local frame transformation (LFT) theory by comparing it with benchmark coupled-channel calculations. The system under consideration is an alkali-metal atom that is two-photon ionized in the presence of a static external electric field. Zhao et al. state that the differential cross sections computed in the LFT theory disagree with their supposedly more accurate coupled-channel calculations. They went on to diagnose the discrepancy and claimed that it originates in an inaccurate correspondence between the irregular functions in spherical and parabolic-cylindrical coordinates, a correspondence that lies at the heart of LFT theory. We have repeated the same tests and find that our calculations rule out the discrepancies that were claimed in Zhao et al. [Phys. Rev. A 86, 053413 (2012), 10.1103/PhysRevA.86.053413] to exist between the LFT approximation and the exact calculations. This Comment thus helps to clarify the accuracy of the Harmin-Fano theory and demonstrates that it is in fact remarkably accurate not only for the total photoionization cross section in the Stark effect, but also for the differential cross section in photoionization microscopy.

  5. Valence photoionization of small alkaline earth atoms endohedrally confined in C60

    NASA Astrophysics Data System (ADS)

    Javani, M. H.; McCreary, M. R.; Patel, A. B.; Madjet, M. E.; Chakraborty, H. S.; Manson, S. T.

    2012-07-01

    A theoretical study of photoionization from the outermost orbitals of Be, Mg and Ca atoms endohedrally confined in C60 is reported. The fullerene ion core, comprised of sixty C4+, is smudged into a continuous jellium charge distribution, while the delocalized cloud of carbon valence electrons plus the encaged atom are treated in the time-dependent local density approximation (TDLDA). Systematic evolution of the mixing of outer atomic level with states of the C60 valence band is found along the sequence. This is found to influence the plasmonic enhancement of atomic photoionization at low energies and the geometry-revealing confinement oscillations at high energies in significantly different ways: (a) the extent of enhancement is mainly determined by the strength of atomic ionization, giving the strongest enhancement for Be even though Ca suffers the largest mixing. But (b) strongest collateral oscillations are uncovered for Ca, since, relative to Be and Mg, the mixing causes the highest photoelectron production at confining boundaries of Ca. The study paints the first comparative picture of the atomic valence photospectra for alkaline earth metallofullerenes in a dynamical many-electron framework.

  6. VUV photodynamics and chiral asymmetry in the photoionization of gas phase alanine enantiomers.

    PubMed

    Tia, Maurice; Cunha de Miranda, Barbara; Daly, Steven; Gaie-Levrel, François; Garcia, Gustavo A; Nahon, Laurent; Powis, Ivan

    2014-04-17

    The valence shell photoionization of the simplest proteinaceous chiral amino acid, alanine, is investigated over the vacuum ultraviolet region from its ionization threshold up to 18 eV. Tunable and variable polarization synchrotron radiation was coupled to a double imaging photoelectron/photoion coincidence (i(2)PEPICO) spectrometer to produce mass-selected threshold photoelectron spectra and derive the state-selected fragmentation channels. The photoelectron circular dichroism (PECD), an orbital-sensitive, conformer-dependent chiroptical effect, was also recorded at various photon energies and compared to continuum multiple scattering calculations. Two complementary vaporization methods-aerosol thermodesorption and a resistively heated sample oven coupled to an adiabatic expansion-were applied to promote pure enantiomers of alanine into the gas phase, yielding neutral alanine with different internal energy distributions. A comparison of the photoelectron spectroscopy, fragmentation, and dichroism measured for each of the vaporization methods was rationalized in terms of internal energy and conformer populations and supported by theoretical calculations. The analytical potential of the so-called PECD-PICO detection technique-where the electron spectroscopy and circular dichroism can be obtained as a function of mass and ion translational energy-is underlined and applied to characterize the origin of the various species found in the experimental mass spectra. Finally, the PECD findings are discussed within an astrochemical context, and possible implications regarding the origin of biomolecular asymmetry are identified.

  7. Disentangling Multichannel Photodissociation Dynamics in Acetone by Time-Resolved Photoelectron-Photoion Coincidence Spectroscopy.

    PubMed

    Maierhofer, Paul; Bainschab, Markus; Thaler, Bernhard; Heim, Pascal; Ernst, Wolfgang E; Koch, Markus

    2016-08-18

    For the investigation of photoinduced dynamics in molecules with time-resolved pump-probe photoionization spectroscopy, it is essential to obtain unequivocal information about the fragmentation behavior induced by the laser pulses. We present time-resolved photoelectron-photoion coincidence (PEPICO) experiments to investigate the excited-state dynamics of isolated acetone molecules triggered by two-photon (269 nm) excitation. In the complex situation of different relaxation pathways, we unambiguously identify three distinct pump-probe ionization channels. The high selectivity of PEPICO detection allows us to observe the fragmentation behavior and to follow the time evolution of each channel separately. For channels leading to fragment ions, we quantitatively obtain the fragment-to-parent branching ratio and are able to determine experimentally whether dissociation occurs in the neutral molecule or in the parent ion. These results highlight the importance of coincidence detection for the interpretation of time-resolved photochemical relaxation and dissociation studies if multiple pathways are present. PMID:27459051

  8. Photoionization of phenothiazine: EPR detection of reactions of the polarized solvated electron

    SciTech Connect

    Turro, N.J.; Khudyakov, I.V.; Willigen, H. van

    1995-12-13

    Photoionization of phenothiazine (PTH) and reactions of the solvated electron with some electron acceptors were studied with steady state and time-resolved EPR and transient optical absorption techniques. Time-resolved EPR spectra from the phenothiazine cation radical (PTH{sup .+}) and hydrated electron (e{sub aq}{sup -}) formed in sodium 1-dodecylsulfate (SDS) micellar solution were observed in emission. By contrast, PTH{sup .+} formed by photoionization of PTH in alcohols gives absorptive EPR signals. The spin polarization carried by the hydrated electron in SDS solutions can be transferred effectively to a stable nitroxyl free radical 3-carboxy-2,2,5, 5-tetramethyl-1-pyrrolidinyloxyl (N{sup .-}) present in the bulk aqueous phase. EPR and flash photolysis measurements show that this electron spin polarization transfer process proceeds with a rate which is approximately five times faster than the chemical reaction between e{sub aq}{sup -} and N{sup .-}. The marked difference in rates is attributed to differences in spin-statistical factors and difference in reaction radii for spin exchange compared to reaction. In alcohol solutions of PTH and a nitroxyl stable radical (2,2,6, 6-tetramethylpyperidin-1-oxyl, TEMPO), excitation of PTH also results in emissive polarization of the EPR spectrum of the stable radical. 46 refs., 12 figs.

  9. Dissociative photoionization of β-pinene: an experimental and theoretical study.

    PubMed

    Sheng, Liusi; Cao, Maoqi; Chen, Jun; Fang, Wenzhen; Li, Yuquan; Ge, Shaolin; Shan, Xiaobin; Liu, Fuyi; Zhao, Yujie; Zhenya Wang, Zhenya Wang

    2014-01-01

    We investigated the photoionization and dissociation photoionization of the β-pinene molecular using time-of-flight mass spectrometry with a tunable vacuum ultraviolet source in the region from 8.00eV to 15.50eV. The experimental ionization energy (IE) value is 8.60eV using electron impact as the ionization source which is not in good agreement with theoretical value (8.41 eV) with a G3MP2 method. We obtained the accurate IE of β-pinene (8.45 ± 0.03eV) derived from the efficiency spectrum which is in good agreement with the theoretical value (8.38eV) of the CBS-QB3 method. We elucidated the dissociation pathways of primary fragment ions from the β-pinene cation on the basis of experimental observations in combination with theoretical calculations. Most of the dissociation pathways occur via a rearrangement reaction prior to dissociation. We also determined the structures of the transition states and intermediates for those isomerization processes.

  10. Multimaterial 4D Printing with Tailorable Shape Memory Polymers.

    PubMed

    Ge, Qi; Sakhaei, Amir Hosein; Lee, Howon; Dunn, Conner K; Fang, Nicholas X; Dunn, Martin L

    2016-08-08

    We present a new 4D printing approach that can create high resolution (up to a few microns), multimaterial shape memory polymer (SMP) architectures. The approach is based on high resolution projection microstereolithography (PμSL) and uses a family of photo-curable methacrylate based copolymer networks. We designed the constituents and compositions to exhibit desired thermomechanical behavior (including rubbery modulus, glass transition temperature and failure strain which is more than 300% and larger than any existing printable materials) to enable controlled shape memory behavior. We used a high resolution, high contrast digital micro display to ensure high resolution of photo-curing methacrylate based SMPs that requires higher exposure energy than more common acrylate based polymers. An automated material exchange process enables the manufacture of 3D composite architectures from multiple photo-curable SMPs. In order to understand the behavior of the 3D composite microarchitectures, we carry out high fidelity computational simulations of their complex nonlinear, time-dependent behavior and study important design considerations including local deformation, shape fixity and free recovery rate. Simulations are in good agreement with experiments for a series of single and multimaterial components and can be used to facilitate the design of SMP 3D structures.

  11. Multimaterial 4D Printing with Tailorable Shape Memory Polymers

    NASA Astrophysics Data System (ADS)

    Ge, Qi; Sakhaei, Amir Hosein; Lee, Howon; Dunn, Conner K.; Fang, Nicholas X.; Dunn, Martin L.

    2016-08-01

    We present a new 4D printing approach that can create high resolution (up to a few microns), multimaterial shape memory polymer (SMP) architectures. The approach is based on high resolution projection microstereolithography (PμSL) and uses a family of photo-curable methacrylate based copolymer networks. We designed the constituents and compositions to exhibit desired thermomechanical behavior (including rubbery modulus, glass transition temperature and failure strain which is more than 300% and larger than any existing printable materials) to enable controlled shape memory behavior. We used a high resolution, high contrast digital micro display to ensure high resolution of photo-curing methacrylate based SMPs that requires higher exposure energy than more common acrylate based polymers. An automated material exchange process enables the manufacture of 3D composite architectures from multiple photo-curable SMPs. In order to understand the behavior of the 3D composite microarchitectures, we carry out high fidelity computational simulations of their complex nonlinear, time-dependent behavior and study important design considerations including local deformation, shape fixity and free recovery rate. Simulations are in good agreement with experiments for a series of single and multimaterial components and can be used to facilitate the design of SMP 3D structures.

  12. Multimaterial 4D Printing with Tailorable Shape Memory Polymers

    PubMed Central

    Ge, Qi; Sakhaei, Amir Hosein; Lee, Howon; Dunn, Conner K.; Fang, Nicholas X.; Dunn, Martin L.

    2016-01-01

    We present a new 4D printing approach that can create high resolution (up to a few microns), multimaterial shape memory polymer (SMP) architectures. The approach is based on high resolution projection microstereolithography (PμSL) and uses a family of photo-curable methacrylate based copolymer networks. We designed the constituents and compositions to exhibit desired thermomechanical behavior (including rubbery modulus, glass transition temperature and failure strain which is more than 300% and larger than any existing printable materials) to enable controlled shape memory behavior. We used a high resolution, high contrast digital micro display to ensure high resolution of photo-curing methacrylate based SMPs that requires higher exposure energy than more common acrylate based polymers. An automated material exchange process enables the manufacture of 3D composite architectures from multiple photo-curable SMPs. In order to understand the behavior of the 3D composite microarchitectures, we carry out high fidelity computational simulations of their complex nonlinear, time-dependent behavior and study important design considerations including local deformation, shape fixity and free recovery rate. Simulations are in good agreement with experiments for a series of single and multimaterial components and can be used to facilitate the design of SMP 3D structures. PMID:27499417

  13. Effortless assignment with 4D covariance sequential correlation maps.

    PubMed

    Harden, Bradley J; Mishra, Subrata H; Frueh, Dominique P

    2015-11-01

    Traditional Nuclear Magnetic Resonance (NMR) assignment procedures for proteins rely on preliminary peak-picking to identify and label NMR signals. However, such an approach has severe limitations when signals are erroneously labeled or completely neglected. The consequences are especially grave for proteins with substantial peak overlap, and mistakes can often thwart entire projects. To overcome these limitations, we previously introduced an assignment technique that bypasses traditional pick peaking altogether. Covariance Sequential Correlation Maps (COSCOMs) transform the indirect connectivity information provided by multiple 3D backbone spectra into direct (H, N) to (H, N) correlations. Here, we present an updated method that utilizes a single four-dimensional spectrum rather than a suite of three-dimensional spectra. We demonstrate the advantages of 4D-COSCOMs relative to their 3D counterparts. We introduce improvements accelerating their calculation. We discuss practical considerations affecting their quality. And finally we showcase their utility in the context of a 52 kDa cyclization domain from a non-ribosomal peptide synthetase.

  14. Multimaterial 4D Printing with Tailorable Shape Memory Polymers.

    PubMed

    Ge, Qi; Sakhaei, Amir Hosein; Lee, Howon; Dunn, Conner K; Fang, Nicholas X; Dunn, Martin L

    2016-01-01

    We present a new 4D printing approach that can create high resolution (up to a few microns), multimaterial shape memory polymer (SMP) architectures. The approach is based on high resolution projection microstereolithography (PμSL) and uses a family of photo-curable methacrylate based copolymer networks. We designed the constituents and compositions to exhibit desired thermomechanical behavior (including rubbery modulus, glass transition temperature and failure strain which is more than 300% and larger than any existing printable materials) to enable controlled shape memory behavior. We used a high resolution, high contrast digital micro display to ensure high resolution of photo-curing methacrylate based SMPs that requires higher exposure energy than more common acrylate based polymers. An automated material exchange process enables the manufacture of 3D composite architectures from multiple photo-curable SMPs. In order to understand the behavior of the 3D composite microarchitectures, we carry out high fidelity computational simulations of their complex nonlinear, time-dependent behavior and study important design considerations including local deformation, shape fixity and free recovery rate. Simulations are in good agreement with experiments for a series of single and multimaterial components and can be used to facilitate the design of SMP 3D structures. PMID:27499417

  15. Effortless assignment with 4D covariance sequential correlation maps

    NASA Astrophysics Data System (ADS)

    Harden, Bradley J.; Mishra, Subrata H.; Frueh, Dominique P.

    2015-11-01

    Traditional Nuclear Magnetic Resonance (NMR) assignment procedures for proteins rely on preliminary peak-picking to identify and label NMR signals. However, such an approach has severe limitations when signals are erroneously labeled or completely neglected. The consequences are especially grave for proteins with substantial peak overlap, and mistakes can often thwart entire projects. To overcome these limitations, we previously introduced an assignment technique that bypasses traditional pick peaking altogether. Covariance Sequential Correlation Maps (COSCOMs) transform the indirect connectivity information provided by multiple 3D backbone spectra into direct (H, N) to (H, N) correlations. Here, we present an updated method that utilizes a single four-dimensional spectrum rather than a suite of three-dimensional spectra. We demonstrate the advantages of 4D-COSCOMs relative to their 3D counterparts. We introduce improvements accelerating their calculation. We discuss practical considerations affecting their quality. And finally we showcase their utility in the context of a 52 kDa cyclization domain from a non-ribosomal peptide synthetase.

  16. Attosecond time delay in the photoionization of Mn in the region of the 3 p →3 d giant resonance

    NASA Astrophysics Data System (ADS)

    Dolmatov, V. K.; Kheifets, A. S.; Deshmukh, P. C.; Manson, S. T.

    2015-05-01

    Initial insight into time delay in Mn photoionization in the region of the 3 p →,3 d giant autoionization resonance is gained in the framework of the "spin-polarized" random-phase approximation with exchange. The dramatic effect of the giant autoionization resonance on the time delay of photoemission from the 3 d and 4 s valence subshells of the Mn atom is unraveled. Strong sensitivity of the time delay of the 4 s photoemission to the final-state term of the ion remainder [Mn+(4 s1,5S ) vs Mn+(4 s1,7S ) ] is discovered. It is shown that photoionization time delay in the autoionizing resonance region is explicitly associated with the resonance lifetime, which can thus be directly measured in attosecond time-delay experiments. Similar features are expected to emerge in photoionization time delays of other transition-metal and rare-earth atoms with half-filled subshells that possess giant autoionization resonances as well.

  17. 2,4-D and IAA Amino Acid Conjugates Show Distinct Metabolism in Arabidopsis

    PubMed Central

    Eyer, Luděk; Vain, Thomas; Pařízková, Barbora; Oklestkova, Jana; Barbez, Elke; Kozubíková, Hana; Pospíšil, Tomáš; Wierzbicka, Roksana; Kleine-Vehn, Jürgen; Fránek, Milan; Strnad, Miroslav; Robert, Stéphanie

    2016-01-01

    The herbicide 2,4-D exhibits an auxinic activity and therefore can be used as a synthetic and traceable analog to study auxin-related responses. Here we identified that not only exogenous 2,4-D but also its amide-linked metabolite 2,4-D-Glu displayed an inhibitory effect on plant growth via the TIR1/AFB auxin-mediated signaling pathway. To further investigate 2,4-D metabolite conversion, identity and activity, we have developed a novel purification procedure based on the combination of ion exchange and immuno-specific sorbents combined with a sensitive liquid chromatography-mass spectrometry method. In 2,4-D treated samples, 2,4-D-Glu and 2,4-D-Asp were detected at 100-fold lower concentrations compared to 2,4-D levels, showing that 2,4-D can be metabolized in the plant. Moreover, 2,4-D-Asp and 2,4-D-Glu were identified as reversible forms of 2,4-D homeostasis that can be converted to free 2,4-D. This work paves the way to new studies of auxin action in plant development. PMID:27434212

  18. 2,4-D and IAA Amino Acid Conjugates Show Distinct Metabolism in Arabidopsis.

    PubMed

    Eyer, Luděk; Vain, Thomas; Pařízková, Barbora; Oklestkova, Jana; Barbez, Elke; Kozubíková, Hana; Pospíšil, Tomáš; Wierzbicka, Roksana; Kleine-Vehn, Jürgen; Fránek, Milan; Strnad, Miroslav; Robert, Stéphanie; Novak, Ondrej

    2016-01-01

    The herbicide 2,4-D exhibits an auxinic activity and therefore can be used as a synthetic and traceable analog to study auxin-related responses. Here we identified that not only exogenous 2,4-D but also its amide-linked metabolite 2,4-D-Glu displayed an inhibitory effect on plant growth via the TIR1/AFB auxin-mediated signaling pathway. To further investigate 2,4-D metabolite conversion, identity and activity, we have developed a novel purification procedure based on the combination of ion exchange and immuno-specific sorbents combined with a sensitive liquid chromatography-mass spectrometry method. In 2,4-D treated samples, 2,4-D-Glu and 2,4-D-Asp were detected at 100-fold lower concentrations compared to 2,4-D levels, showing that 2,4-D can be metabolized in the plant. Moreover, 2,4-D-Asp and 2,4-D-Glu were identified as reversible forms of 2,4-D homeostasis that can be converted to free 2,4-D. This work paves the way to new studies of auxin action in plant development. PMID:27434212

  19. Digit ratio (2D:4D) and hand preference for writing in the BBC Internet Study.

    PubMed

    Manning, J T; Peters, M

    2009-09-01

    The ratio of the length of the second to the fourth digit (2D:4D) may be negatively correlated with prenatal testosterone. Hand preference has been linked with prenatal testosterone and 2D:4D. Here we show that 2D:4D is associated with hand preference for writing in a large internet sample (n>170,000) in which participants self-reported their finger lengths. We replicated a significant association between right 2D:4D and writing hand preference (low right 2D:4D associated with left hand preference) as well as a significant correlation between writing hand preference and the difference between left and right 2D:4D or Dr-l (low Dr-l associated with left hand preference). A new significant correlation between left 2D:4D and writing hand preference was also shown (high left 2D:4D associated with left hand preference). There was a clear interaction between writing hand preference and 2D:4D: The left 2D:4D was significantly larger than the right 2D:4D in male and female left-handed writers, and the right hand 2D:4D was significantly larger than the left hand 2D:4D in male and female right-handed writers.

  20. Double Photoionization of excited Lithium and Beryllium

    SciTech Connect

    Yip, Frank L.; McCurdy, C. William; Rescigno, Thomas N.

    2010-05-20

    We present total, energy-sharing and triple differential cross sections for one-photon, double ionization of lithium and beryllium starting from aligned, excited P states. We employ a recently developed hybrid atomic orbital/ numerical grid method based on the finite-element discrete-variable representation and exterior complex scaling. Comparisons with calculated results for the ground-state atoms, as well as analogous results for ground-state and excited helium, serve to highlight important selection rules and show some interesting effects that relate to differences between inter- and intra-shell electron correlation.

  1. Double-photoionization of helium including quadrupole radiation effects

    SciTech Connect

    Colgan, James; Ludlow, J A; Lee, Teck - Ghee; Pindzola, M S; Robicheaux, F

    2009-01-01

    Non-perturbative time-dependent close-coupling calculations are carried out for the double photoionization of helium including both dipole and quadrupole radiation effects. At a photon energy of 800 eV, accessible at CUlTent synchrotron light sources, the quadrupole interaction contributes around 6% to the total integral double photoionization cross section. The pure quadrupole single energy differential cross section shows a local maxima at equal energy sharing, as opposed to the minimum found in the pure dipole single energy differential cross section. The sum of the pure dipole and pure quadrupole single energy differentials is insensitive to non-dipole effects at 800 eV. However, the triple differential cross section at equal energy sharing of the two ejected electrons shows strong non-dipole effects due to the quadrupole interaction that may be experimentally observable.

  2. A non-invasive online photoionization spectrometer for FLASH2

    PubMed Central

    Braune, Markus; Brenner, Günter; Dziarzhytski, Siarhei; Juranić, Pavle; Sorokin, Andrey; Tiedtke, Kai

    2016-01-01

    The stochastic nature of the self-amplified spontaneous emission (SASE) process of free-electron lasers (FELs) effects pulse-to-pulse fluctuations of the radiation properties, such as the photon energy, which are determinative for processes of photon–matter interactions. Hence, SASE FEL sources pose a great challenge for scientific investigations, since experimenters need to obtain precise real-time feedback of these properties for each individual photon bunch for interpretation of the experimental data. Furthermore, any device developed to deliver the according information should not significantly interfere with or degrade the FEL beam. Regarding the spectral properties, a device for online monitoring of FEL wavelengths has been developed for FLASH2, which is based on photoionization of gaseous targets and the measurements of the corresponding electron and ion time-of-flight spectra. This paper presents experimental studies and cross-calibration measurements demonstrating the viability of this online photoionization spectrometer. PMID:26698040

  3. A non-invasive online photoionization spectrometer for FLASH2.

    PubMed

    Braune, Markus; Brenner, Günter; Dziarzhytski, Siarhei; Juranić, Pavle; Sorokin, Andrey; Tiedtke, Kai

    2016-01-01

    The stochastic nature of the self-amplified spontaneous emission (SASE) process of free-electron lasers (FELs) effects pulse-to-pulse fluctuations of the radiation properties, such as the photon energy, which are determinative for processes of photon-matter interactions. Hence, SASE FEL sources pose a great challenge for scientific investigations, since experimenters need to obtain precise real-time feedback of these properties for each individual photon bunch for interpretation of the experimental data. Furthermore, any device developed to deliver the according information should not significantly interfere with or degrade the FEL beam. Regarding the spectral properties, a device for online monitoring of FEL wavelengths has been developed for FLASH2, which is based on photoionization of gaseous targets and the measurements of the corresponding electron and ion time-of-flight spectra. This paper presents experimental studies and cross-calibration measurements demonstrating the viability of this online photoionization spectrometer. PMID:26698040

  4. Spatially resolved photoionization of ultracold atoms on an atom chip

    SciTech Connect

    Kraft, S.; Guenther, A.; Fortagh, J.; Zimmermann, C.

    2007-06-15

    We report on photoionization of ultracold magnetically trapped Rb atoms on an atom chip. The atoms are trapped at 5 {mu}K in a strongly anisotropic trap. Through a hole in the chip with a diameter of 150 {mu}m, two laser beams are focused onto a fraction of the atomic cloud. A first laser beam with a wavelength of 778 nm excites the atoms via a two-photon transition to the 5D level. With a fiber laser at 1080 nm the excited atoms are photoionized. Ionization leads to depletion of the atomic density distribution observed by absorption imaging. The resonant ionization spectrum is reported. The setup used in this experiment is suitable not only to investigate mixtures of Bose-Einstein condensates and ions but also for single-atom detection on an atom chip.

  5. Precision measurements on the photoionization of neutral atomic species

    NASA Astrophysics Data System (ADS)

    Stolte, Wayne

    2016-05-01

    In contrast to studies on rare gas atoms, experimental studies of open-shell atoms offers very challenging problems, such as creation of the atom, low signal, purity and stability. Because of this, studies of inner-shell excitations for open shell atoms are limited. In this talk I will discuss precision experimental measurements for photoionization of atomic oxygen, nitrogen, and chlorine over the last two decades on various beamlines at Lawrence Berkeley National Laboratories, Advanced Light Source.

  6. Differential cross sections of double photoionization of lithium

    SciTech Connect

    Kheifets, A. S.; Fursa, D. V.; Bray, I.; Colgan, J.; Pindzola, M. S.

    2010-08-15

    We extend our previous application of the convergent close-coupling (CCC) and time-dependent close-coupling (TDCC) methods [Phys. Rev. A 81, 023418 (2010)] to describe energy and angular resolved double photoionization (DPI) of lithium at arbitrary energy sharing. By doing so, we are able to evaluate the recoil ion momentum distribution of DPI of Li and make a comparison with recent measurements of Zhu et al. [Phys. Rev. Lett. 103, 103008 (2009)].

  7. Double Photoionization in Ring Molecules: Search of the Cooper Pair Formation

    NASA Astrophysics Data System (ADS)

    Jänkälä, K.; Lablanquie, P.; Penent, F.; Palaudoux, J.; Andric, L.; Huttula, M.

    2014-04-01

    We provide a final state selective experimental study on the direct double photoionization of the valence states of benzene and pyrrole. The experiment is carried out using a magnetic-bottle electron time-of-flight coincidence setup at the incident photon energy region of 25-120 eV. We discuss on the recently discovered phenomenon of so-called Cooper pair formation [R. Wehlitz et al., Phys. Rev. Lett. 109, 193001 (2012)] and show that our experiment provides contradicting evidence on its existence in the proposed form. We confirm the finding of a new two-electron continuum resonance structure observed at about 30-70 eV above the double ionization threshold in benzene, provide further information from it, and suggest an alternative explanation.

  8. Photoionization of He above the N =2 threshold. II. Angular distribution of photoelectrons and asymmetry parameter

    SciTech Connect

    Sanchez, I.; Martin, F. )

    1992-04-01

    We report theoretical calculations for the {beta}{sub 2{ital p}}-asymmetry parameter in the photoionization of He(1{ital s}{sup 2}) above the {ital N}=2 ionization threshold. We use an extension of a method recently proposed (I. Sanchez and F. Martin, Phys. Rev. A 44, 7318 (1991)) that makes use of a Feshbach partitioning of the final-state wave function and an {ital L}{sup 2} representation of the coupled continuum states. Partial differential cross sections at emission angles 0{degree} and 90{degree} are also provided. Our results are in good agreement with the experimental data, thus showing the accuracy of the present method to study electron angular-distribution properties.

  9. Solvent jet desorption capillary photoionization-mass spectrometry.

    PubMed

    Haapala, Markus; Teppo, Jaakko; Ollikainen, Elisa; Kiiski, Iiro; Vaikkinen, Anu; Kauppila, Tiina J; Kostiainen, Risto

    2015-03-17

    A new ambient mass spectrometry method, solvent jet desorption capillary photoionization (DCPI), is described. The method uses a solvent jet generated by a coaxial nebulizer operated at ambient conditions with nitrogen as nebulizer gas. The solvent jet is directed onto a sample surface, from which analytes are extracted into the solvent and ejected from the surface in secondary droplets formed in collisions between the jet and the sample surface. The secondary droplets are directed into the heated capillary photoionization (CPI) device, where the droplets are vaporized and the gaseous analytes are ionized by 10 eV photons generated by a vacuum ultraviolet (VUV) krypton discharge lamp. As the CPI device is directly connected to the extended capillary inlet of the MS, high ion transfer efficiency to the vacuum of MS is achieved. The solvent jet DCPI provides several advantages: high sensitivity for nonpolar and polar compounds with limit of detection down to low fmol levels, capability of analyzing small and large molecules, and good spatial resolution (250 μm). Two ionization mechanisms are involved in DCPI: atmospheric pressure photoionization, capable of ionizing polar and nonpolar compounds, and solvent assisted inlet ionization capable of ionizing larger molecules like peptides. The feasibility of DCPI was successfully tested in the analysis of polar and nonpolar compounds in sage leaves and chili pepper. PMID:25715054

  10. Interchannel coupling effects in the valence photoionization of SF6

    NASA Astrophysics Data System (ADS)

    Jose, J.; Lucchese, R. R.; Rescigno, T. N.

    2014-05-01

    The complex Kohn and polyatomic Schwinger variational techniques have been employed to illustrate the interchannel coupling correlation effects in the valence photoionization dynamics of SF6. Partial photoionization cross sections and asymmetry parameters of six valence subshells (1t1g, 5t1u, 1t2u, 3eg, 1t2g, 4t1u) are discussed in the framework of several theoretical and experimental studies. The complex Kohn results are in rather good agreement with experimental results, indicative of the fact that the interchannel coupling effects alter the photoionization dynamics significantly. We find that the dominant effect of interchannel coupling is to reduce the magnitude of shape resonant cross sections near the threshold and to induce resonant features in other channels to which resonances are coupled. The long-standing issue concerning ordering of the valence orbitals is addressed and confirmed 4t1u61t2g63eg4(5t1u6+1t2u6) 1t1g6 as the most likely ordering.

  11. Absolute photoionization cross-section of the propargyl radical

    SciTech Connect

    Savee, John D.; Welz, Oliver; Taatjes, Craig A.; Osborn, David L.; Soorkia, Satchin; Selby, Talitha M.

    2012-04-07

    Using synchrotron-generated vacuum-ultraviolet radiation and multiplexed time-resolved photoionization mass spectrometry we have measured the absolute photoionization cross-section for the propargyl (C{sub 3}H{sub 3}) radical, {sigma}{sub propargyl}{sup ion}(E), relative to the known absolute cross-section of the methyl (CH{sub 3}) radical. We generated a stoichiometric 1:1 ratio of C{sub 3}H{sub 3} : CH{sub 3} from 193 nm photolysis of two different C{sub 4}H{sub 6} isomers (1-butyne and 1,3-butadiene). Photolysis of 1-butyne yielded values of {sigma}{sub propargyl}{sup ion}(10.213 eV)=(26.1{+-}4.2) Mb and {sigma}{sub propargyl}{sup ion}(10.413 eV)=(23.4{+-}3.2) Mb, whereas photolysis of 1,3-butadiene yielded values of {sigma}{sub propargyl}{sup ion}(10.213 eV)=(23.6{+-}3.6) Mb and {sigma}{sub propargyl}{sup ion}(10.413 eV)=(25.1{+-}3.5) Mb. These measurements place our relative photoionization cross-section spectrum for propargyl on an absolute scale between 8.6 and 10.5 eV. The cross-section derived from our results is approximately a factor of three larger than previous determinations.

  12. Photoionization Modeling and the K Lines of Iron

    NASA Technical Reports Server (NTRS)

    Kallman, T. R.; Palmeri, P.; Bautista, M. A.; Mendoza, C.; Krolik, J. H.

    2004-01-01

    We calculate the efficiency of iron K line emission and iron K absorption in photoionized models using a new set of atomic data. These data are more comprehensive than those previously applied to the modeling of iron K lines from photoionized gases, and allow us to systematically examine the behavior of the properties of line emission and absorption as a function of the ionization parameter, density and column density of model constant density clouds. We show that, for example, the net fluorescence yield for the highly charged ions is sensitive to the level population distribution produced by photoionization, and these yields are generally smaller than those predicted assuming the population is according to statistical weight. We demonstrate that the effects of the many strongly damped resonances below the K ionization thresholds conspire to smear the edge, thereby potentially affecting the astrophysical interpretation of absorption features in the 7-9 keV energy band. We show that the centroid of the ensemble of K(alpha) lines, the K(beta) energy, and the ratio of the K(alpha(sub 1)) to K(alpha(sub 2)) components are all diagnostics of the ionization parameter of our model slabs.

  13. An ecological risk assessment of the exposure and effects of 2,4-D acid to rainbow trout (Onchorhyncus mykiss)

    USGS Publications Warehouse

    Fairchild, J.F.; Feltz, K.P.; Allert, A.L.; Sappington, L.C.; Nelson, K.J.; Valle, J.A.

    2009-01-01

    Numerous state and federal agencies are increasingly concerned with the rapid expansion of invasive, noxious weeds across the United States. Herbicides are frequently applied as weed control measures in forest and rangeland ecosystems that frequently overlap with critical habitats of threatened and endangered fish species. However, there is little published chronic toxicity data for herbicides and fish that can be used to assess ecological risk of herbicides in aquatic environments. We conducted 96-h flowthrough acute and 30-day chronic toxicity studies with swim-up larvae and juvenile rainbow trout (Onchorhyncus mykiss) exposed to the free acid form of 2,4-D. Juvenile rainbow trout were acutely sensitive to 2,4-D acid equivalent at 494 mg/L (95% confidence interval [CI] 334-668 mg/L; 96-h ALC50). Accelerated life-testing procedures, used to estimate chronic mortality from acute data, predicted that a 30-day exposure of juvenile rainbow trout to 2,4-D would result in 1% and 10% mortality at 260 and 343 mg/L, respectively. Swim-up larvae were chronically more sensitive than juveniles using growth as the measurement end point. The 30-day lowest observable effect concentration (LOEC) of 2,4-D on growth of swim-up larvae was 108 mg/L, whereas the 30-day no observable effect concentration (NOEC) was 54 mg/L. The 30-day maximum acceptable toxicant concentration (MATC) of 2,4-D for rainbow trout, determined as the geometric mean of the NOEC and the LOEC, was 76 mg/L. The acute:chronic ratio was 6.5 (i.e., 494/76). We observed no chronic effects on growth of juvenile rainbow trout at the highest concentration tested (108 mg/L). Worst-case aquatic exposures to 2,4-D (4 mg/L) occur when the herbicide is directly applied to aquatic ecosystems for aquatic weed control and resulted in a 30-day safety factor of 19 based on the MATC for growth (i.e., 76/4). Highest nontarget aquatic exposures to 2,4-D applied following terrestrial use is calculated at 0.136 mg/L and resulted in a

  14. GRAM 88 - 4D GLOBAL REFERENCE ATMOSPHERE MODEL-1988

    NASA Technical Reports Server (NTRS)

    Johnson, D. L.

    1994-01-01

    the Jacchia values. Below 25km the atmospheric parameters are computed by the 4-D worldwide atmospheric model of Spiegler and Fowler (1972). This data set is not included. GRAM-88 incorporates a hydrostatic/gas law check in the 0-30 km altitude range to flag and change any bad data points. Between 5km and 30km, an interpolation scheme is used between the 4-D results and the modified Groves values. The output parameters consist of components for: (1) latitude, longitude, and altitude dependent monthly and annual means, (2) quasi-biennial oscillations (QBO), and (3) random perturbations to partially simulate the variability due to synoptic, diurnal, planetary wave, and gravity wave variations. Quasi-biennial and random variation perturbations are computed from parameters determined by various empirical studies and are added to the monthly mean values. The GRAM-88 program is for batch execution on the IBM 3084. It is written in STANDARD FORTRAN 77 under the MVS/XA operating system. The IBM DISPLA graphics routines are necessary for graphical output. The program was developed in 1988.

  15. Communication: Imaging wavefunctions in dissociative photoionization

    NASA Astrophysics Data System (ADS)

    Scott Hopkins, W.; Mackenzie, Stuart R.

    2011-08-01

    The dissociative ionization dynamics of excited electronic states of the xenon dimer, Xe2, have been studied using velocity map ion imaging (VMI). A one-colour, (2+1) resonant excitation scheme was employed to first excite and then ionize selected vibrational levels of the Xe2 6p 2[1/2]0 0_g^ + Rydberg state. Cationic fragments were then detected by the VMI. The data provide an outstanding example of the reflection principle in photodissociation with the full nodal structure of the Rydberg state wavefunctions clearly observed in the final Xe+ kinetic energy distributions without the need for scanning the excitation energy. Fitting of the observed distributions provides detailed and precise information on the form of the Xe2+ I(1/2g) potential energy curve involved which is in excellent agreement with the results of photoelectron imaging studies [Shubert and Pratt, J. Chem. Phys. 134, 044315 (2011), 10.1063/1.3533361]. Furthermore, the anisotropy of the product angular distributions yields information on the evolution of the electronic character of the ionic state with internuclear separation, R. The combination of the nature of dissociative ionization and the extent of the bound state wavefunctions provide information over an unusually wide range of internuclear separation R (ΔR > 0.75 Å). This would normally require scanning over a considerable energy region but is obtained in these studies at a fixed excitation energy.

  16. 4D measurement system for automatic location of anatomical structures

    NASA Astrophysics Data System (ADS)

    Witkowski, Marcin; Sitnik, Robert; Kujawińska, Małgorzata; Rapp, Walter; Kowalski, Marcin; Haex, Bart; Mooshake, Sven

    2006-04-01

    Orthopedics and neurosciences are fields of medicine where the analysis of objective movement parameters is extremely important for clinical diagnosis. Moreover, as there are significant differences between static and dynamic parameters, there is a strong need of analyzing the anatomical structures under functional conditions. In clinical gait analysis the benefits of kinematical methods are undoubted. In this paper we present a 4D (3D + time) measurement system capable of automatic location of selected anatomical structures by locating and tracing the structures' position and orientation in time. The presented system is designed to help a general practitioner in diagnosing selected lower limbs' dysfunctions (e.g. knee injuries) and also determine if a patient should be directed for further examination (e.g. x-ray or MRI). The measurement system components are hardware and software. For the hardware part we adapt the laser triangulation method. In this way we can evaluate functional and dynamic movements in a contact-free, non-invasive way, without the use of potentially harmful radiation. Furthermore, opposite to marker-based video-tracking systems, no preparation time is required. The software part consists of a data acquisition module, an image processing and point clouds (point cloud, set of points described by coordinates (x, y, z)) calculation module, a preliminary processing module, a feature-searching module and an external biomechanical module. The paper briefly presents the modules mentioned above with the focus on the feature-searching module. Also we present some measurement and analysis results. These include: parameters maps, landmarks trajectories in time sequence and animation of a simplified model of lower limbs.

  17. Infrared PINEM developed by diffraction in 4D UEM

    PubMed Central

    Liu, Haihua; Baskin, John Spencer; Zewail, Ahmed H.

    2016-01-01

    The development of four-dimensional ultrafast electron microscopy (4D UEM) has enabled not only observations of the ultrafast dynamics of photon–matter interactions at the atomic scale with ultrafast resolution in image, diffraction, and energy space, but photon–electron interactions in the field of nanoplasmonics and nanophotonics also have been captured by the related technique of photon-induced near-field electron microscopy (PINEM) in image and energy space. Here we report a further extension in the ongoing development of PINEM using a focused, nanometer-scale, electron beam in diffraction space for measurements of infrared-light-induced PINEM. The energy resolution in diffraction mode is unprecedented, reaching 0.63 eV under the 200-keV electron beam illumination, and separated peaks of the PINEM electron-energy spectrum induced by infrared light of wavelength 1,038 nm (photon energy 1.2 eV) have been well resolved for the first time, to our knowledge. In a comparison with excitation by green (519-nm) pulses, similar first-order PINEM peak amplitudes were obtained for optical fluence differing by a factor of more than 60 at the interface of copper metal and vacuum. Under high fluence, the nonlinear regime of IR PINEM was observed, and its spatial dependence was studied. In combination with PINEM temporal gating and low-fluence infrared excitation, the PINEM diffraction method paves the way for studies of structural dynamics in reciprocal space and energy space with high temporal resolution. PMID:26848135

  18. Binary 4D seismic history matching, a metric study

    NASA Astrophysics Data System (ADS)

    Chassagne, Romain; Obidegwu, Dennis; Dambrine, Julien; MacBeth, Colin

    2016-11-01

    This paper explores 4D seismic history matching and it specifically focuses on the objective function used during the optimisation with seismic data. The objective function is calculated by using binary maps, where one map is obtained from the observed seismic data and the other is from one realisation of the optimisation algorithm from the simulation model. In order to decide which set of parameters is a relevant update for the simulation model, an efficient way is required to measure how similar these two binary images are, during their evaluation within the objective function. Behind this aspect of quantification of the similarities or dissimilarities lies the metric notion, or the art of measuring distances. Four metrics are proposed with this study, the well-known Hamming distance, two widely used metrics, the Hausdorff distance and Mutual Information and a recent metric, called the Current Measure Metric. These metrics will be tested and compared on different case scenarios, designed in accordance to a real field case (gas exsolution) before being used in the second part of the paper. Despite its simplicity, the Hamming distance gives positive results, but the Current Measure Metric appears to be a more efficient choice to cover a wider range of scenarios, these conclusions remain true when tested on synthetic and real dataset in a history matching exercise. Some practical aspects of binary map processes will be examined through the paper, as it is shown that it is more proper to use a derivative free optimisation algorithm and a proper metric should be more inclined to capture global features than local features.

  19. Fast interactive exploration of 4D MRI flow data

    NASA Astrophysics Data System (ADS)

    Hennemuth, A.; Friman, O.; Schumann, C.; Bock, J.; Drexl, J.; Huellebrand, M.; Markl, M.; Peitgen, H.-O.

    2011-03-01

    1- or 2-directional MRI blood flow mapping sequences are an integral part of standard MR protocols for diagnosis and therapy control in heart diseases. Recent progress in rapid MRI has made it possible to acquire volumetric, 3-directional cine images in reasonable scan time. In addition to flow and velocity measurements relative to arbitrarily oriented image planes, the analysis of 3-dimensional trajectories enables the visualization of flow patterns, local features of flow trajectories or possible paths into specific regions. The anatomical and functional information allows for advanced hemodynamic analysis in different application areas like stroke risk assessment, congenital and acquired heart disease, aneurysms or abdominal collaterals and cranial blood flow. The complexity of the 4D MRI flow datasets and the flow related image analysis tasks makes the development of fast comprehensive data exploration software for advanced flow analysis a challenging task. Most existing tools address only individual aspects of the analysis pipeline such as pre-processing, quantification or visualization, or are difficult to use for clinicians. The goal of the presented work is to provide a software solution that supports the whole image analysis pipeline and enables data exploration with fast intuitive interaction and visualization methods. The implemented methods facilitate the segmentation and inspection of different vascular systems. Arbitrary 2- or 3-dimensional regions for quantitative analysis and particle tracing can be defined interactively. Synchronized views of animated 3D path lines, 2D velocity or flow overlays and flow curves offer a detailed insight into local hemodynamics. The application of the analysis pipeline is shown for 6 cases from clinical practice, illustrating the usefulness for different clinical questions. Initial user tests show that the software is intuitive to learn and even inexperienced users achieve good results within reasonable processing

  20. Vessels as 4-D curves: global minimal 4-D paths to extract 3-D tubular surfaces and centerlines.

    PubMed

    Li, Hua; Yezzi, Anthony

    2007-09-01

    In this paper, we propose an innovative approach to the segmentation of tubular structures. This approach combines all of the benefits of minimal path techniques such as global minimizers, fast computation, and powerful incorporation of user input, while also having the capability to represent and detect vessel surfaces directly which so far has been a feature restricted to active contour and surface techniques. The key is to represent the trajectory of a tubular structure not as a 3-D curve but to go up a dimension and represent the entire structure as a 4-D curve. Then we are able to fully exploit minimal path techniques to obtain global minimizing trajectories between two user supplied endpoints in order to reconstruct tubular structures from noisy or low contrast 3-D data without the sensitivity to local minima inherent in most active surface techniques. In contrast to standard purely spatial 3-D minimal path techniques, however, we are able to represent a full tubular surface rather than just a curve which runs through its interior. Our representation also yields a natural notion of a tube's "central curve." We demonstrate and validate the utility of this approach on magnetic resonance (MR) angiography and computed tomography (CT) images of coronary arteries. PMID:17896594

  1. 32 CFR 1630.43 - Class 4-D: Minister of religion.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 32 National Defense 6 2010-07-01 2010-07-01 false Class 4-D: Minister of religion. 1630.43 Section... CLASSIFICATION RULES § 1630.43 Class 4-D: Minister of religion. In accord with part 1645 of this chapter any registrant shall be placed in Class 4-D who is a: (a) Duly ordained minister of religion; or (b)...

  2. 32 CFR 1630.43 - Class 4-D: Minister of religion.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 32 National Defense 6 2013-07-01 2013-07-01 false Class 4-D: Minister of religion. 1630.43 Section... CLASSIFICATION RULES § 1630.43 Class 4-D: Minister of religion. In accord with part 1645 of this chapter any registrant shall be placed in Class 4-D who is a: (a) Duly ordained minister of religion; or (b)...

  3. 32 CFR 1630.43 - Class 4-D: Minister of religion.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 32 National Defense 6 2014-07-01 2014-07-01 false Class 4-D: Minister of religion. 1630.43 Section... CLASSIFICATION RULES § 1630.43 Class 4-D: Minister of religion. In accord with part 1645 of this chapter any registrant shall be placed in Class 4-D who is a: (a) Duly ordained minister of religion; or (b)...

  4. 32 CFR 1630.43 - Class 4-D: Minister of religion.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 32 National Defense 6 2011-07-01 2011-07-01 false Class 4-D: Minister of religion. 1630.43 Section... CLASSIFICATION RULES § 1630.43 Class 4-D: Minister of religion. In accord with part 1645 of this chapter any registrant shall be placed in Class 4-D who is a: (a) Duly ordained minister of religion; or (b)...

  5. 32 CFR 1630.43 - Class 4-D: Minister of religion.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 32 National Defense 6 2012-07-01 2012-07-01 false Class 4-D: Minister of religion. 1630.43 Section... CLASSIFICATION RULES § 1630.43 Class 4-D: Minister of religion. In accord with part 1645 of this chapter any registrant shall be placed in Class 4-D who is a: (a) Duly ordained minister of religion; or (b)...

  6. 40 CFR 180.142 - 2,4-D; tolerances for residues.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 24 2014-07-01 2014-07-01 false 2,4-D; tolerances for residues. 180..., plant regulator, and fungicide 2,4-D, including its metabolites and degradates, in or on the commodities... 2,4-D (2,4-dichlorophenoxyacetic acid), both free and conjugated, determined as the acid, in or...

  7. Photoionization branching ratios and vibrational intensity distribution for N2, CO; and CO2 between 53 and 75 nm

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Gardner, J. L.

    1973-01-01

    The probability of radiation producing ions in specific electronic and vibrational levels was documented. For example, when a narrow band-pass of solar ionizing photons is incident on an atmospheric species it is now possible to describe, accurately, how the radiant energy is shared among the various electronic states of the ions produced. The molecules studied were N2, CO, and CO2. These molecules were photoionized by radiation between 53 and 75 nm. The effects of autoionization are discussed and continuum vibrational intensities are tabulated and compared with theoretical Franck-Condon factors where available. The branching ratios and partial cross sections for ionization into various electronic states are tabulated.

  8. Rovibronically selected and resolved two-color laser photoionization and photoelectron study of cobalt carbide cation

    NASA Astrophysics Data System (ADS)

    Huang, Huang; Chang, Yih Chung; Luo, Zhihong; Shi, Xiaoyu; Lam, Chow-Shing; Lau, Kai-Chung; Ng, C. Y.

    2013-03-01

    We have conducted a two-color visible-ultraviolet (VIS-UV) resonance-enhanced laser photoionization efficiency and pulsed field ionization-photoelectron (PFI-PE) study of gaseous cobalt carbide (CoC) near its ionization onset in the total energy range of 61 200-64 510 cm-1. The cold gaseous CoC sample was prepared by a laser ablation supersonically cooled beam source. By exciting CoC molecules thus generated to single N' rotational levels of the intermediate CoC*(2Σ+; v') state using a VIS dye laser prior to UV laser photoionization, we have obtained N+ rotationally resolved PFI-PE spectra for the CoC+(X1Σ+; v+ = 0 and 1) ion vibrational bands free from interference by impurity species except Co atoms produced in the ablation source. The rotationally selected and resolved PFI-PE spectra have made possible unambiguous rotational assignments, yielding accurate values for the adiabatic ionization energy of CoC(X2Σ+), IE(CoC) = 62 384.3 ± 0.6 cm-1 (7.73467 ± 0.00007 eV), the vibrational frequency ωe+ = 985.6 ± 0.6 cm-1, the anharmonicity constant ωe+χe+ = 6.3 ± 0.6 cm-1, the rotational constants (Be+ = 0.7196 ± 0.0005 cm-1, αe+ = 0.0056 ± 0.0008 cm-1), and the equilibrium bond length re+ = 1.534 Å for CoC+(X1Σ+). The observation of the N+ = 0 level in the PFI-PE measurement indicates that the CoC+ ground state is of 1Σ+ symmetry. Large ΔN+ = N+ - N' changes up to 6 are observed for the photoionization transitions CoC+(X1Σ+; v+ = 0-2; N+) ← CoC*(2Σ+; v'; N' = 6, 7, 8, and 9). The highly precise energetic and spectroscopic data obtained in the present study have served as a benchmark for testing theoretical predictions based on state-of-the-art ab initio quantum calculations at the CCSDTQ/CBS level of theory as presented in the companion article.

  9. Mineralization of 2,4-dichlorophenoxyacetic acid (2,4-D) and mixtures of 2,4-D and 2,4,5-trichlorophenoxyacetic acid by Phanerochaete chrysosporium

    SciTech Connect

    Yadav, J.S.; Reddy, C.A. )

    1993-09-01

    2,4-dichloropheonxyacetic Acid (2,4-D) is one of the most commonly used phenoxyalkanoic herbicides for selective control of weeds and for defoliation. Since these toxic chemical are manufactured and used each year in massive quantities, effective handling of their production wastes and the contaminated environment is needed. A number of bacterial general are known to degrade 2,4-D, but no naturally occuring bacterium is know to be capable of mineralizing 2,4,5-trichlorophenoxyacetic acid. Mutual inhibition of degradation has been reported when 2,4-D and 2,4,5-T are presented in a mixture to degrading bacteria. This paper investigates the ability of Pseudomonas chrysosporium to mineralize 2,4-D individually and in combination with 2,4,5-T. Results indicate that P. chrysosporium effectively mineralizes 2,4-D alone as well as in combination with 2,4,5-T. 31 refs., 4 figs., 1 tab.

  10. Theoretical Modeling of Radiation-driven Atomic Kinetics of a Neon Photoionized Plasma

    NASA Astrophysics Data System (ADS)

    Durmaz, Tunay

    We report on a theoretical study on atomic kinetics modeling of a photoionized neon plasma at conditions relevant to laboratory experiments performed at the Z-machine in Sandia National Laboratories. We describe an atomic kinetics model and code, ATOKIN, that was developed and used to compute the atomic level population distribution. The study includes atomic level sensitivity with respect to energy level structure, radiation and transient effects, electron temperature and x-ray drive sensitivity and an idea for electron temperature extraction from a level population ratio. The neon atomic model considers several ionization stages of highly-charged neon ions as well as a detailed structure of non-autoionizing and autoionizing energy levels in each ion. In the energy level sensitivity study, the atomic model was changed by adding certain types of energy levels such as singly-excited, auto-ionizing doubly-excited states. Furthermore, these levels were added ion by ion for the most populated ions. Atomic processes populating and de-populating the energy levels consider photoexcitation and photoionization due to the external radiation flux, and spontaneous and collisional atomic processes including plasma radiation trapping. Relevant atomic cross sections and rates were computed with the atomic structure and scattering FAC code. The calculations were performed at constant particle number density and driven by the time-histories of temperature and external radiation flux. These conditions were selected in order to resemble those achieved in photoionized plasma experiments at the Z facility of Sandia National Laboratories. For the same set of time histories, calculations were done in a full time-dependent mode and also as a sequence of instantaneous, steady states. Differences between both calculations are useful to identify transient effects in the ionization and atomic kinetics of the photoionized plasma, and its dependence on the atomic model and plasma environmental

  11. 4D tumor centroid tracking using orthogonal 2D dynamic MRI: Implications for radiotherapy planning

    SciTech Connect

    Tryggestad, Erik; Flammang, Aaron; Shea, Steven M.; Hales, Russell; Herman, Joseph; Lee, Junghoon; McNutt, Todd; Roland, Teboh; Wong, John

    2013-09-15

    Purpose: Current pretreatment, 4D imaging techniques are suboptimal in that they sample breathing motion over a very limited “snapshot” in time. Heretofore, long-duration, 4D motion characterization for radiotherapy planning, margin optimization, and validation have been impractical for safety reasons, requiring invasive markers imaged under x-ray fluoroscopy. To characterize 3D tumor motion and associated variability over durations more consistent with treatments, the authors have developed a practical dynamic MRI (dMRI) technique employing two orthogonal planes acquired in a continuous, interleaved fashion.Methods: 2D balanced steady-state free precession MRI was acquired continuously over 9–14 min at approximately 4 Hz in three healthy volunteers using a commercial 1.5 T system; alternating orthogonal imaging planes (sagittal, coronal, sagittal, etc.) were employed. The 2D in-plane pixel resolution was 2 × 2 mm{sup 2} with a 5 mm slice profile. Simultaneous with image acquisition, the authors monitored a 1D surrogate respiratory signal using a device available with the MRI system. 2D template matching-based anatomic feature registration, or tracking, was performed independently in each orientation. 4D feature tracking at the raw frame rate was derived using spline interpolation.Results: Tracking vascular features in the lung for two volunteers and pancreatic features in one volunteer, the authors have successfully demonstrated this method. Registration error, defined here as the difference between the sagittal and coronal tracking result in the SI direction, ranged from 0.7 to 1.6 mm (1σ) which was less than the acquired image resolution. Although the healthy volunteers were instructed to relax and breathe normally, significantly variable respiration was observed. To demonstrate potential applications of this technique, the authors subsequently explored the intrafraction stability of hypothetical tumoral internal target volumes and 3D spatial probability

  12. Photoionization and predissociation of H3

    NASA Astrophysics Data System (ADS)

    Helm, H.; Lembo, L. J.; Cosby, P. C.; Huestis, D. L.

    1990-04-01

    Triatomic hydrogen in the lowest rotational level of the 2p2A2` state is long-lived (˜80 μs). This molecule is readily formed in charge transfer of H+3 in cesium. Laser excitation of the molecule allows study of electric field induced ionization as well as autoionization of the Rydberg series of H3. Two photon ionization and double resonance techniques are applied to determine vibrational frequencies of trihydrogen. Experimental analysis of the electron-core interaction shows that selective optical excitation of core rotation and core vibration can be achieved concurrent with excitation of the Rydberg electron. Predissociation of Rydberg states is observed to lead to the formation of both H2+H as well as H+H+H fragments.

  13. Semantic World Modelling and Data Management in a 4d Forest Simulation and Information System

    NASA Astrophysics Data System (ADS)

    Roßmann, J.; Hoppen, M.; Bücken, A.

    2013-08-01

    Various types of 3D simulation applications benefit from realistic forest models. They range from flight simulators for entertainment to harvester simulators for training and tree growth simulations for research and planning. Our 4D forest simulation and information system integrates the necessary methods for data extraction, modelling and management. Using modern methods of semantic world modelling, tree data can efficiently be extracted from remote sensing data. The derived forest models contain position, height, crown volume, type and diameter of each tree. This data is modelled using GML-based data models to assure compatibility and exchangeability. A flexible approach for database synchronization is used to manage the data and provide caching, persistence, a central communication hub for change distribution, and a versioning mechanism. Combining various simulation techniques and data versioning, the 4D forest simulation and information system can provide applications with "both directions" of the fourth dimension. Our paper outlines the current state, new developments, and integration of tree extraction, data modelling, and data management. It also shows several applications realized with the system.

  14. Experimenting with the GMAO 4D Data Assimilation

    NASA Technical Reports Server (NTRS)

    Todling, R.; El Akkraoui, A.; Errico, R. M.; Guo, J.; Kim, J.; Kliest, D.; Parrish, D. F.; Suarez, M.; Trayanov, A.; Tremolet, Yannick; Whitaker, J.

    2012-01-01

    The Global Modeling and Assimilation Office (GMAO) has been working to promote its prototype four-dimensional variational (4DVAR) system to a version that can be exercised at operationally desirable configurations. Beyond a general circulation model (GeM) and an analysis system, traditional 4DV AR requires availability of tangent linear (TL) and adjoint (AD) models of the corresponding GeM. The GMAO prototype 4DVAR uses the finite-volume-based GEOS GeM and the Grid-point Statistical Interpolation (GSI) system for the first two, and TL and AD models derived ITom an early version of the finite-volume hydrodynamics that is scientifically equivalent to the present GEOS nonlinear GeM but computationally rather outdated. Specifically, the TL and AD models hydrodynamics uses a simple (I-dimensional) latitudinal MPI domain decomposition, which has consequent low scalability and prevents the prototype 4DV AR ITom being used in realistic applications. In the near future, GMAO will be upgrading its operational GEOS GCM (and assimilation system) to use a cubed-sphere-based hydrodynamics. This versions of the dynamics scales to thousands of processes and has led to a decision to re-derive the TL and AD models for this more modern dynamics, thus taking advantage of a two-dimensional MPI decomposition and improved scalability properties. With the aid of the Transformation of Algorithms in FORTRAN (l'AF) automatic adjoint generation tool and some hand-coding, a version of the cubed-sphere-based TL and AD models, with a simplified vertical diffusion scheme, is now available, enabling multiple configurations of standard implementations of 4DV AR in GEOS. Concurrent to this development, collaboration with the National Centers for Environmental Prediction (NCEP) and the Earth System Research Laboratory (ESRL) has allowed GMAO to implement a hybrid-ensemble capability within the GEOS data assimilation system. Both 3Dand 4D-ensemble capabilities are presently available thus allowing

  15. A dose error evaluation study for 4D dose calculations

    NASA Astrophysics Data System (ADS)

    Milz, Stefan; Wilkens, Jan J.; Ullrich, Wolfgang

    2014-10-01

    Previous studies have shown that respiration induced motion is not negligible for Stereotactic Body Radiation Therapy. The intrafractional breathing induced motion influences the delivered dose distribution on the underlying patient geometry such as the lung or the abdomen. If a static geometry is used, a planning process for these indications does not represent the entire dynamic process. The quality of a full 4D dose calculation approach depends on the dose coordinate transformation process between deformable geometries. This article provides an evaluation study that introduces an advanced method to verify the quality of numerical dose transformation generated by four different algorithms. The used transformation metric value is based on the deviation of the dose mass histogram (DMH) and the mean dose throughout dose transformation. The study compares the results of four algorithms. In general, two elementary approaches are used: dose mapping and energy transformation. Dose interpolation (DIM) and an advanced concept, so called divergent dose mapping model (dDMM), are used for dose mapping. The algorithms are compared to the basic energy transformation model (bETM) and the energy mass congruent mapping (EMCM). For evaluation 900 small sample regions of interest (ROI) are generated inside an exemplary lung geometry (4DCT). A homogeneous fluence distribution is assumed for dose calculation inside the ROIs. The dose transformations are performed with the four different algorithms. The study investigates the DMH-metric and the mean dose metric for different scenarios (voxel sizes: 8 mm, 4 mm, 2 mm, 1 mm 9 different breathing phases). dDMM achieves the best transformation accuracy in all measured test cases with 3-5% lower errors than the other models. The results of dDMM are reasonable and most efficient in this study, although the model is simple and easy to implement. The EMCM model also achieved suitable results, but the approach requires a more complex

  16. Predicting lower mantle heterogeneity from 4-D Earth models

    NASA Astrophysics Data System (ADS)

    Flament, Nicolas; Williams, Simon; Müller, Dietmar; Gurnis, Michael; Bower, Dan J.

    2016-04-01

    basal layer ˜ 4% denser than ambient mantle. Increasing convective vigour (Ra ≈ 5 x 108) or decreasing the density of the basal layer decreases both the accuracy and sensitivity of the predicted lower mantle structure. References: D. J. Bower, M. Gurnis, N. Flament, Assimilating lithosphere and slab history in 4-D Earth models. Phys. Earth Planet. Inter. 238, 8-22 (2015). V. Lekic, S. Cottaar, A. Dziewonski, B. Romanowicz, Cluster analysis of global lower mantle tomography: A new class of structure and implications for chemical heterogeneity. Earth Planet. Sci. Lett. 357, 68-77 (2012).

  17. 4D Visualization of Experimental Procedures in Rock Physics

    NASA Astrophysics Data System (ADS)

    Vanorio, T.; di Bonito, C.

    2010-12-01

    Engaging students in laboratory classes in geophysics is becoming more and more difficult. This is primarily because of an ever-widening gap between the less appealing aspects that characterize these courses (e.g., lengthiness of the experimental operations, high student/instrument ratio, limited time associated with lack of previous hands-on experiences, and logistical and safety concerns) and the life style of the 21st century generations (i.e., extensive practice to high-tech tools, high-speed communications and computing, 3D graphics and HD videos). To bridge the gap and enhance the teaching strategy of laboratory courses in geophysics, we have created simulator-training tools for use in preparation for the actual experimental phase. We are using a modeling, animation, and rendering package to create (a) 3D models that accurately reproduce actual scenarios and instruments used for the measurement of rock physics properties and (b) 4D interactive animations that simulate hands-on demonstrations of the experimental procedures. We present here a prototype describing step-by-step the experimental protocol and the principles behind the measurement of rock porosity. The tool reproduces an actual helium porosimeter and makes use of interactive animations, guided text, and a narrative voice guiding the audience through the different phases of the experimental process. Our strategy is to make the most of new technologies while preserving the accuracy of classical laboratory methods and practices. These simulations are not intended to replace traditional lab work; rather they provide students with the opportunity for review and repetition. The primary goal is thus to help students familiarize themselves during their earlier curricula with lab methodologies, thus minimizing apparent hesitation and frustration in later classes. This may also increase the level of interest and involvement of undergraduate students and, in turn, enhance their keenness to pursue their

  18. Interactive 4D Visualization of Sediment Transport Models

    NASA Astrophysics Data System (ADS)

    Butkiewicz, T.; Englert, C. M.

    2013-12-01

    Coastal sediment transport models simulate the effects that waves, currents, and tides have on near-shore bathymetry and features such as beaches and barrier islands. Understanding these dynamic processes is integral to the study of coastline stability, beach erosion, and environmental contamination. Furthermore, analyzing the results of these simulations is a critical task in the design, placement, and engineering of coastal structures such as seawalls, jetties, support pilings for wind turbines, etc. Despite the importance of these models, there is a lack of available visualization software that allows users to explore and perform analysis on these datasets in an intuitive and effective manner. Existing visualization interfaces for these datasets often present only one variable at a time, using two dimensional plan or cross-sectional views. These visual restrictions limit the ability to observe the contents in the proper overall context, both in spatial and multi-dimensional terms. To improve upon these limitations, we use 3D rendering and particle system based illustration techniques to show water column/flow data across all depths simultaneously. We can also encode multiple variables across different perceptual channels (color, texture, motion, etc.) to enrich surfaces with multi-dimensional information. Interactive tools are provided, which can be used to explore the dataset and find regions-of-interest for further investigation. Our visualization package provides an intuitive 4D (3D, time-varying) visualization of sediment transport model output. In addition, we are also integrating real world observations with the simulated data to support analysis of the impact from major sediment transport events. In particular, we have been focusing on the effects of Superstorm Sandy on the Redbird Artificial Reef Site, offshore of Delaware Bay. Based on our pre- and post-storm high-resolution sonar surveys, there has significant scour and bedform migration around the

  19. Double photoionization of molecular hydrogen: A theoretical study including the nuclear dissociation

    NASA Astrophysics Data System (ADS)

    Le Rouzo, H.

    1988-03-01

    The double photoionization of molecular hydrogen is theoretically investigated in the 40-100-eV photon energy range. The calculation is ab initio and rests first on the Born-Oppenheimer separation. The exact nuclear wave functions have been used for both (bound) initial and (dissociative) final two-proton states and the Franck-Condon approximation is not invoked. The electronic part of the initial ground state of H2 is highly correlated while the final one is simply a symmetrized product of uncorrelated Coulomb wave functions. Within this framework, the total cross sections obtained in the dipole-velocity formulation agree well with very recent experimental results. In addition, the method is able to provide the kinetic-energy distributions of the fragments (electrons and protons) as functions of the photon energy. The energy distributions of the ejected protons, produced by 60-100-eV impacting photons, are similar in shape to those resulting from electron or proton impact on H2. In contrast, it is found that the most probable two-proton kinetic energy is significantly lowered in the threshold region. On the other hand, the differential electron spectrum gives some insights into the sharing of energy between the s, p, and d ejected electrons. Within the δ approximation, which is shown to be very accurate over the whole photon energy range, the threshold law for the double photoionization of diatomic molecules is derived. It is found that the cross section can be represented, up to 10 eV above threshold, as the convolution of the density probability in the initial vibrational ground state with a series of linear thresholds, similar to those derived in the Wannier-Rau-Peterkop theory for atoms.

  20. Bonding characteristics of the. sqrt. 3-script. sqrt. 3 Ag/Si interface identified by the energy dependence of the photoionization cross section

    SciTech Connect

    Yeh, J.; Bertness, K.A.; Cao, R.; Hwang, J.; Lindau, I.

    1987-02-15

    Synchrotron-radiation photoemission of the metal-semiconductor interface has a unique advantage in identifying the bonding characteristics of the rehybridized orbitals between the metal and the semiconductor. By varying the photon energy and measuring the magnitude of the photoionization cross section, the bonding peak at the metal-semiconductor interface can be identified as being formed with or without hybridization with the metal's d orbitals. The latter case is clearly illustrated by the annealed Ag/Si(111) interface. A sharp structure at 3.8 eV below the Fermi level grows as a result of annealing of the Ag/Si(111) interface. This structure is also accompanied by the formation of the ..sqrt..3 x ..sqrt..3 (R30/sup 0/) low-energy electron diffraction pattern and the narrowing of the Ag 4d band signal. Since the so-called Cooper-minimum effect is not observed for this annealing-induced peak, it is concluded that the structure does not have 4d-orbital characteristics within the regime of the theory of linear combination of atomic orbitals. This is the direct evidence to show that the Ag 4d band does not hybridize with the substrate Si sp/sup 3/ orbitals in forming Ag: Si bonds after high-temperature annealing. Judging from the photoionization cross-section variation, it can instead be inferred that the sharp structure has mostly Ag 5s or 5p and Si sp characteristics. The methodology shown here can be extended to other metal-semiconductor interfaces and can provide information on the bonding formation of the metal atoms and the semiconductor substrate.

  1. Bonding characteristics of the √3°√3 Ag/Si interface identified by the energy dependence of the photoionization cross section

    NASA Astrophysics Data System (ADS)

    Yeh, J.-J.; Bertness, K. A.; Cao, R.; Hwang, J.; Lindau, I.

    1987-02-01

    Synchrotron-radiation photoemission of the metal-semiconductor interface has a unique advantage in identifying the bonding characteristics of the rehybridized orbitals between the metal and the semiconductor. By varying the photon energy and measuring the magnitude of the photoionization cross section, the bonding peak at the metal-semiconductor interface can be identified as being formed with or without hybridization with the metal's d orbitals. The latter case is clearly illustrated by the annealed Ag/Si(111) interface. A sharp structure at 3.8 eV below the Fermi level grows as a result of annealing of the Ag/Si(111) interface. This structure is also accompanied by the formation of the √3 × √3 (R30°) low-energy electron diffraction pattern and the narrowing of the Ag 4d band signal. Since the so-called Cooper-minimum effect is not observed for this annealing-induced peak, it is concluded that the structure does not have 4d-orbital characteristics within the regime of the theory of linear combination of atomic orbitals. This is the direct evidence to show that the Ag 4d band does not hybridize with the substrate Si sp3 orbitals in forming Ag-Si bonds after high-temperature annealing. Judging from the photoionization cross-section variation, it can instead be inferred that the sharp structure has mostly Ag 5s or 5p and Si sp characteristics. The methodology shown here can be extended to other metal-semiconductor interfaces and can provide information on the bonding formation of the metal atoms and the semiconductor substrate. This is important in discussing metal-semiconductor interfaces but difficult to obtain unambiguously with other techniques and in theoretical predictions.

  2. Characteristics of potential repository wastes: Volume 4, Appendix 4A, Nuclear reactors at educational institutions of the United States; Appendix 4B, Data sheets for nuclear reactors at educational institutions; Appendix 4C, Supplemental data for Fort St. Vrain spent fuel; Appendix 4D, Supplemental data for Peach Bottom 1 spent fuel; Appendix 4E, Supplemental data for Fast Flux Test Facility

    SciTech Connect

    Not Available

    1992-07-01

    Volume 4 contains the following appendices: nuclear reactors at educational institutions in the United States; data sheets for nuclear reactors at educational institutions in the United States(operational reactors and shut-down reactors); supplemental data for Fort St. Vrain spent fuel; supplemental data for Peach Bottom 1 spent fuel; and supplemental data for Fast Flux Test Facility.

  3. Photoionization of highly charged ions from ultra-intense, ultraviolet and near-infrared radiation fields

    NASA Astrophysics Data System (ADS)

    Ekanayake, Nagitha

    High intensity laser light was instrumental for notable advances across an exceptional range of disciplines including plasma physics, quantum control, attosecond science, molecular dynamics, inertial confinement fusion, and optical science. Current laser technology has brought about the next generation of ultra-high intensities (1019 W/cm2). Our common understanding of light-matter interactions breaks down at these extreme intensities, especially when the liberated photoelectron becomes relativistic and the effect of the laser magnetic field is no longer negligible. As the ultrastrong laser science frontier involves unprecedented energy scales from 1 keV to 1 MeV and opens up an abundance of new high energy atomic and molecular processes, photoionization dynamics of atoms and molecules in super- and ultra-high intensity fields become an area of interest. The work presented in this dissertation is carried out to provide a better answer to the fundamental question "How atoms and molecules interact with super- and ultra-intense light fields?" In particular, the presented work will cover quantitative measurements of ionization products, ions and photoelectrons, from strong- (1013 -- 1016 W/cm2) to ultra-strong (10 16 -- 1019 W/cm2) field ionization of noble gas atoms (Ne, Kr, and Xe) and hydrocarbon molecules (CH4). In order to understand the molecular ionization processes at extreme intensities the ellipticity dependence of the ultrafast photoionization for Cn+ fragments from methane is investigated. The study extends from the strong field (C+, C2+) at 10 14 W/cm2 to the ultrastrong field (C5+) at 1018 W/cm2. The first precision measurements of ionization of Ne and Kr at 400 nm are presented from 1013 to 1017 W/cm2 for charge states up to Kr 8+. The findings indicate that ultraviolet to vacuum ultraviolet wavelengths can give the largest recollision for higher charge states. Experimental photoelectron measurements from single atom photoionization of noble gases

  4. Atomic data for neutron-capture elements. I. Photoionization and recombination properties of low-charge selenium ions

    NASA Astrophysics Data System (ADS)

    Sterling, N. C.; Witthoeft, M. C.

    2011-05-01

    We present multi-configuration Breit-Pauli AUTOSTRUCTURE calculations of distorted-wave photoionization (PI) cross sections, and total and partial final-state resolved radiative recombination (RR) and dielectronic recombination (DR) rate coefficients for the first six ions of the trans-iron element Se. These calculations were motivated by the recent detection of Se emission lines in a large number of planetary nebulae. Se is a potentially useful tracer of neutron-capture nucleosynthesis, but accurate determinations of its abundance in photoionized nebulae have been hindered by the lack of atomic data governing its ionization balance. Our calculations were carried out in intermediate coupling with semi-relativistic radial wavefunctions. PI and recombination data were determined for levels within the ground configuration of each ion, and experimental PI cross-section measurements were used to benchmark our results. For DR, we allowed Δn = 0 core excitations, which are important at photoionized plasma temperatures. We find that DR is the dominant recombination process for each of these Se ions at temperatures representative of photoionized nebulae (~104 K). In order to estimate the uncertainties of these data, we compared results from three different configuration-interaction expansions for each ion, and also tested the sensitivity of the results to the radial scaling factors in the structure calculations. We find that the internal uncertainties are typically 30-50% for the direct PI cross sections and ~10% for the computed RR rate coefficients, while those for low-temperature DR can be considerably larger (from 15-30% up to two orders of magnitude) due to the unknown energies of near-threshold autoionization resonances. These data are available at the CDS, and fitting coefficients to the total RR and DR rate coefficients are presented. The results are suitable for incorporation into photoionization codes used to numerically simulate astrophysical nebulae, and will

  5. Ig-like transcript 4 as a cellular receptor for soluble complement fragment C4d.

    PubMed

    Hofer, Johannes; Forster, Florian; Isenman, David E; Wahrmann, Markus; Leitner, Judith; Hölzl, Markus A; Kovarik, Johannes J; Stockinger, Hannes; Böhmig, Georg A; Steinberger, Peter; Zlabinger, Gerhard J

    2016-04-01

    Complement regulation leads to the generation of complement split products (CSPs) such as complement component (C)4d, a marker for disease activity in autoimmune syndromes or antibody-mediated allograft rejection. However, the physiologic role of C4d has been unknown. By screening murine thymoma BW5147 cells expressing a cDNA library generated from human monocyte-derived dendritic cells with recombinant human C4d, we identified Ig-like transcript (ILT)4 and ILT5v2 as cellular receptors for C4d. Both receptors, expressed on monocytes, macrophages, and dendritic cells, also interacted with the CSPs C3d, C4b, C3b, and iC3b. However, C4d did not bind to classic complement receptors (CRs). Interaction between cell surface-resident ILT4 and soluble monomeric C4d resulted in endocytosis of C4d. Surprisingly, binding of soluble ILT4 to C4d covalently immobilized to a cellular surface following classic complement activation could not be detected. Remarkably, C4d immobilized to a solid phaseviaits intrinsic thioester conferred a dose-dependent inhibition of TNF-α and IL-6 secretion in monocytes activatedviaFc-cross-linking of up to 50% as compared to baseline. Similarly, C4d conferred an attenuation of intracellular Ca(2+)flux in monocytes activatedviaFc-cross-linking. In conclusion, ILT4 represents a scavenger-type endocytotic CR for soluble monomeric C4d, whereas attenuation of monocyte activation by physiologically oriented C4d on a surface appears to be dependent on a yet to be identified C4d receptor.-Hofer, J., Forster, F., Isenman, D. E., Wahrmann, M., Leitner, J., Hölzl, M. A., Kovarik, J. K., Stockinger, H., Böhmig, G. A., Steinberger, P., Zlabinger, G. J. Ig-like transcript 4 as a cellular receptor for soluble complement fragment C4d.

  6. Angular anisotropy in valence photoionization of Na clusters: theoretical investigation using jellium model

    NASA Astrophysics Data System (ADS)

    Jänkälä, Kari

    2013-03-01

    Calculation of the behaviour of photoelectron angular anisotropy in valence ionization of initially neutral NaX (X = 34-58) clusters is provided. The calculations are carried out for 1p, 1d and 1g jellium orbitals as a function of photon energy. The adapted theoretical framework is spherical jellium model using Woods-Saxon potential, which is modified to account for the long-range Coulomb tail in the final state. We discuss on the observed dramatic variations of the angular anisotropy parameter β as a function incident photon energy. It is shown that the behaviour is connected to the oscillation of the valence photoionization cross sections, that is a specific interference property of such metallic clusters whose valence structure can be described using the jellium model. ISSPIC 16 - 16th International Symposium on Small Particles and Inorganic Clusters, edited by Kristiaan Temst, Margriet J. Van Bael, Ewald Janssens, H.-G. Boyen and Françoise Remacle.

  7. Characterization of the transient species generated by the photoionization of Berberine: A laser flash photolysis study

    NASA Astrophysics Data System (ADS)

    Cheng, Ling-Li; Wang, Mei; Zhu, Hui; Li, Kun; Zhu, Rong-Rong; Sun, Xiao-Yu; Yao, Si-De; Wu, Qing-Sheng; Wang, Shi-Long

    2009-09-01

    Using 266 nm laser flash photolysis it has been demonstrated that Berberine (BBR) in aqueous solution is ionized via a mono-photonic process giving a hydrated electron, anion radical that formed by hydrated electron react with steady state of BBR, and neutral radical that formed from rapid deprotonation of the radical cation of BBR. The quantum yield of photoionization is determined to be 0.03 at room temperature with KI solution used as a reference. Furthermore utilizing pH changing method and the SO 4rad - radical oxidation method, the assignment of radical cation of BBR was further confirmed, the p Ka value of it was calculated, and the related set up rate constant was also determined.

  8. Data for First Responder Use of Photoionization Detectors for Vapor Chemical Constituents

    SciTech Connect

    Keith A. Daum; Matthew G. Watrous; M. Dean Neptune; Daniel I. Michael; Kevin J. Hull; Joseph D. Evans

    2006-11-01

    First responders need appropriate measurement technologies for evaluating incident scenes. This report provides information about photoionization detectors (PIDs), obtained from manufacturers and independent laboratory tests, and the use of PIDs by first responders, obtained from incident commanders in the United States and Canada. PIDs are valued for their relatively low cost, light weight, rapid detection response, and ease of use. However, it is clear that further efforts are needed to provide suitable instruments and decision tools to incident commanders and first responders for assessing potential hazardous chemical releases. Information provided in this report indicates that PIDs should always be part of a decision-making context in which other qualitative and more definitive tests and instruments are used to confirm a finding. Possible amelioratory actions ranging from quick and relatively easy fixes to those requiring significant additional effort are outlined in the report.

  9. Large Enhancement in High-Energy Photoionization of Fe XVII and Missing Continuum Plasma Opacity.

    PubMed

    Nahar, Sultana N; Pradhan, Anil K

    2016-06-10

    Aimed at solving the outstanding problem of solar opacity, and radiation transport plasma models in general, we report substantial photoabsorption in the high-energy regime due to atomic core photoexcitations not heretofore considered. In extensive R-matrix calculations of unprecedented complexity for an important iron ion Fe xvii (Fe^{16+}), with a wave function expansion of 99 Fe xviii (Fe^{17+}) LS core states from n≤4 complexes (equivalent to 218 fine structure levels), we find (i) up to orders of magnitude enhancement in background photoionization cross sections, in addition to strongly peaked photo-excitation-of-core resonances not considered in current opacity models, and ii) demonstrate convergence with respect to successive core excitations. The resulting increase in the monochromatic continuum, and 35% in the Rosseland mean opacity, are compared with the "higher-than-predicted" iron opacity measured at the Sandia Z-pinch fusion device at solar interior conditions. PMID:27341239

  10. Large Enhancement in High-Energy Photoionization of Fe XVII and Missing Continuum Plasma Opacity

    NASA Astrophysics Data System (ADS)

    Nahar, Sultana N.; Pradhan, Anil K.

    2016-06-01

    Aimed at solving the outstanding problem of solar opacity, and radiation transport plasma models in general, we report substantial photoabsorption in the high-energy regime due to atomic core photoexcitations not heretofore considered. In extensive R -matrix calculations of unprecedented complexity for an important iron ion Fe xvii (Fe16 + ), with a wave function expansion of 99 Fe xviii (Fe17 + ) LS core states from n ≤4 complexes (equivalent to 218 fine structure levels), we find (i) up to orders of magnitude enhancement in background photoionization cross sections, in addition to strongly peaked photo-excitation-of-core resonances not considered in current opacity models, and ii) demonstrate convergence with respect to successive core excitations. The resulting increase in the monochromatic continuum, and 35% in the Rosseland mean opacity, are compared with the "higher-than-predicted" iron opacity measured at the Sandia Z -pinch fusion device at solar interior conditions.

  11. Electron recombination, photoionization, and scattering via many-electron compound resonances

    NASA Astrophysics Data System (ADS)

    Dzuba, V. A.; Flambaum, V. V.; Gribakin, G. F.; Harabati, C.; Kozlov, M. G.

    2013-12-01

    Highly excited eigenstates of atoms and ions with open f shell are chaotic superpositions of thousands, or even millions, of Hartree-Fock determinant states. The interaction between dielectronic and multielectronic configurations leads to the broadening of dielectronic recombination resonances and relative enhancement of photon emission due to opening of thousands of radiative decay channels. The radiative yield is close to 100% for electron energy ≲1 eV and rapidly decreases for higher energies due to opening of many autoionization channels. The same mechanism predicts suppression of photoionization and relative enhancement of the Raman scattering. Results of our calculations of the recombination rate are in agreement with the experimental data for W20+ and Au25+.

  12. Fast acquisition of high resolution 4-D amide-amide NOESY with diagonal suppression, sparse sampling and FFT-CLEAN.

    PubMed

    Werner-Allen, Jon W; Coggins, Brian E; Zhou, Pei

    2010-05-01

    Amide-amide NOESY provides important distance constraints for calculating global folds of large proteins, especially integral membrane proteins with beta-barrel folds. Here, we describe a diagonal-suppressed 4-D NH-NH TROSY-NOESY-TROSY (ds-TNT) experiment for NMR studies of large proteins. The ds-TNT experiment employs a spin state selective transfer scheme that suppresses diagonal signals while providing TROSY optimization in all four dimensions. Active suppression of the strong diagonal peaks greatly reduces the dynamic range of observable signals, making this experiment particularly suitable for use with sparse sampling techniques. To demonstrate the utility of this method, we collected a high resolution 4-D ds-TNT spectrum of a 23kDa protein using randomized concentric shell sampling (RCSS), and we used FFT-CLEAN processing for further reduction of aliasing artifacts - the first application of these techniques to a NOESY experiment. A comparison of peak parameters in the high resolution 4-D dataset with those from a conventionally-sampled 3-D control spectrum shows an accurate reproduction of NOE crosspeaks in addition to a significant reduction in resonance overlap, which largely eliminates assignment ambiguity. Likewise, a comparison of 4-D peak intensities and volumes before and after application of the CLEAN procedure demonstrates that the reduction of aliasing artifacts by CLEAN does not systematically distort NMR signals.

  13. Coherence and Intramolecular Scattering in Molecular Photoionization

    NASA Astrophysics Data System (ADS)

    Becker, U.

    2006-11-01

    In something akin to a double-slit experiment, it could be shown for the first time that electrons display characteristics of both waves- and particles at the same time and, with virtually the push of a button, can be switched back and forth between these states. The experiments provides evidence that disruption of the reflective symmetry of these molecules by introducing two different heavy isotopes, in this case N-14 and N-15, leads to a partial loss of coherence. The electrons begin to partially localise on one of the two, now distinguishable, atoms. The results could have implications for the building and control of "artificial molecules", which are made of semiconductor quantum dots and are a possible component of quantum computers.

  14. Targeted disruption of the heat shock protein 20–phosphodiesterase 4D (PDE4D) interaction protects against pathological cardiac remodelling in a mouse model of hypertrophy

    PubMed Central

    Martin, Tamara P.; Hortigon-Vinagre, Maria P.; Findlay, Jane E.; Elliott, Christina; Currie, Susan; Baillie, George S.

    2014-01-01

    Phosphorylated heat shock protein 20 (HSP20) is cardioprotective. Using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and a mouse model of pressure overload mediated hypertrophy, we show that peptide disruption of the HSP20–phosphodiesterase 4D (PDE4D) complex results in attenuation of action potential prolongation and protection against adverse cardiac remodelling. The later was evidenced by improved contractility, decreased heart weight to body weight ratio, and reduced interstitial and perivascular fibrosis. This study demonstrates that disruption of the specific HSP20–PDE4D interaction leads to attenuation of pathological cardiac remodelling. PMID:25426411

  15. Quantitative airway analysis in longitudinal studies using groupwise registration and 4D optimal surfaces.

    PubMed

    Petersen, Jens; Modat, Marc; Cardoso, Manuel Jorge; Dirksen, Asger; Ourselin, Sebastien; de Bruijne, Marleen

    2013-01-01

    Quantifying local changes to the airway wall surfaces from computed tomography images is important in the study of diseases such as chronic obstructive pulmonary disease. Current approaches segment the airways in the individual time point images and subsequently aggregate per airway generation or perform branch matching to assess regional changes. In contrast, we propose an integrated approach analysing the time points simultaneously using a subject-specific groupwise space and 4D optimal surface segmentation. The method combines information from all time points and measurements are matched locally at any position on the resulting surfaces. Visual inspection of the scans of 10 subjects showed increased tree length compared to the state of the art with little change in the amount of false positives. A large scale analysis of the airways of 374 subjects including a total of 1870 images showed significant correlation with lung function and high reproducibility of the measurements. PMID:24579152

  16. Photoionization mass spectrometric study of the prebiotic species formamide in the 10-20 eV photon energy range.

    PubMed

    Leach, Sydney; Jochims, Hans-Werner; Baumgärtel, Helmut

    2010-04-15

    A photoion mass spectrometry study of the prebiotic species formamide was carried out using synchrotron radiation over the photon energy range 10-20 eV. Photoion yield curves were measured for the parent ion and seven fragment ions. The ionization energy of formamide was determined as IE (1(2)A') = 10.220 +/- 0.005 eV, in agreement with a value obtained by high resolution photoelectron spectroscopy. The adiabatic energy of the first excited state of the ion, 1(2)A'', was revised to 10.55 eV. A comparison of the ionization energies of related formamides, amino acids, and polypeptides provides useful information on the varied effects of methylation and shows that polymerization does not substantially alter the ionization properties of the amino acid monomer units. Assignments of the fragment ions and the pathways of their formation by dissociative photoionization were made on the basis of ion appearance energies in conjunction with thermochemical data and the results of earlier electron impact mass spectral studies. Some of the dissociation pathways are considered to involve coupling between the 1(2)A' ground state and the low-lying 1(2)A'' excited state of the cation. Heats of formation are derived for all ions detected and are compared with literature values where they exist. Formation of the HNCO(+) ion occurs by two separate paths, one involving H(2) loss, the other H + H. In the conclusion a brief discussion is given of some astrophysical implications of these results. PMID:20085361

  17. Influence of the core hole on Kβ emission following photoionization or orbital electron capture: A comparison using MnO and 55Fe2O3

    NASA Astrophysics Data System (ADS)

    Glatzel, P.; Bergmann, U.; de Groot, F. M.; Cramer, S. P.

    2001-07-01

    The Mn Kβ fluorescence emission in MnO after photoionization and in 55Fe2O3 after radioactive electron capture decay from the K shell have been measured using a crystal array spectrometer with an instrumental energy bandwidth of 0.7 eV (full width at half maximum). Both compounds have a 3d5 valence electron configuration in the ionic approximation. It is found that the spectral features after K capture in 55Fe2O3 are shifted in emission energy and are sharper, compared to the spectra following photoionization in MnO, i.e., the spectra exhibit a dependence on the mode of excitation. Crystal-field multiplet calculations including ligand-to-metal charge transfer have been carried out for the 1s intermediate states as well as for the 3p to 1s (Kβ) radiative transition. The populated 1s intermediate states after photoionization are found to be spread over several eV. In comparison, only the lowest-lying 1s intermediate states split by the weak (1s,3d) exchange interaction are populated after K capture. It is proposed that the differences in population of the 1s intermediate states together with a term-dependent final-state lifetime broadening can account for the changes in the spectral shapes due to the different modes of excitation.

  18. SEMA4D compromises blood-brain barrier, activates microglia, and inhibits remyelination in neurodegenerative disease.

    PubMed

    Smith, Ernest S; Jonason, Alan; Reilly, Christine; Veeraraghavan, Janaki; Fisher, Terrence; Doherty, Michael; Klimatcheva, Ekaterina; Mallow, Crystal; Cornelius, Chad; Leonard, John E; Marchi, Nicola; Janigro, Damir; Argaw, Azeb Tadesse; Pham, Trinh; Seils, Jennifer; Bussler, Holm; Torno, Sebold; Kirk, Renee; Howell, Alan; Evans, Elizabeth E; Paris, Mark; Bowers, William J; John, Gareth; Zauderer, Maurice

    2015-01-01

    Multiple sclerosis (MS) is a chronic neuroinflammatory disease characterized by immune cell infiltration of CNS, blood-brain barrier (BBB) breakdown, localized myelin destruction, and progressive neuronal degeneration. There exists a significant need to identify novel therapeutic targets and strategies that effectively and safely disrupt and even reverse disease pathophysiology. Signaling cascades initiated by semaphorin 4D (SEMA4D) induce glial activation, neuronal process collapse, inhibit migration and differentiation of oligodendrocyte precursor cells (OPCs), and disrupt endothelial tight junctions forming the BBB. To target SEMA4D, we generated a monoclonal antibody that recognizes mouse, rat, monkey and human SEMA4D with high affinity and blocks interaction between SEMA4D and its cognate receptors. In vitro, anti-SEMA4D reverses the inhibitory effects of recombinant SEMA4D on OPC survival and differentiation. In vivo, anti-SEMA4D significantly attenuates experimental autoimmune encephalomyelitis in multiple rodent models by preserving BBB integrity and axonal myelination and can be shown to promote migration of OPC to the site of lesions and improve myelin status following chemically-induced demyelination. Our study underscores SEMA4D as a key factor in CNS disease and supports the further development of antibody-based inhibition of SEMA4D as a novel therapeutic strategy for MS and other neurologic diseases with evidence of demyelination and/or compromise to the neurovascular unit. PMID:25461192

  19. The Rab GTPase RabA4d regulates pollen tube tip growth in Arabidopsis thaliana.

    PubMed

    Szumlanski, Amy L; Nielsen, Erik

    2009-02-01

    During reproduction in flowering plants, pollen grains form a tube that grows in a polarized fashion through the female tissues to eventually fertilize the egg cell. These highly polarized pollen tubes have a rapid rate of growth that is supported by a tip-focused delivery of membrane and cell wall components. To gain a better understanding of how this growth is regulated, we investigated the function RABA4D, a member of the Arabidopsis thaliana RabA4 subfamily of Rab GTPase proteins. Here, we show that RABA4D was expressed in a pollen-specific manner and that enhanced yellow fluorescent protein (EYFP)-RabA4d-labeled membrane compartments localized to the tips of growing pollen tubes. Mutant pollen in which the RABA4D gene was disrupted displayed bulged pollen tubes with a reduced rate of growth in vitro and displayed altered deposition of some cell wall components. Expression of EYFP-RabA4d restored wild-type phenotypes to the raba4d mutant pollen tubes, while expression of EYFP-RabA4b did not rescue the raba4d phenotype. In vivo, disruption of RABA4D resulted in a male-specific transmission defect with mutant raba4d pollen tubes displaying aberrant growth in the ovary and reduced guidance at the micropyle. We propose that RabA4d plays an important role in the regulation of pollen tube tip growth.

  20. SEMA4D compromises blood-brain barrier, activates microglia, and inhibits remyelination in neurodegenerative disease.

    PubMed

    Smith, Ernest S; Jonason, Alan; Reilly, Christine; Veeraraghavan, Janaki; Fisher, Terrence; Doherty, Michael; Klimatcheva, Ekaterina; Mallow, Crystal; Cornelius, Chad; Leonard, John E; Marchi, Nicola; Janigro, Damir; Argaw, Azeb Tadesse; Pham, Trinh; Seils, Jennifer; Bussler, Holm; Torno, Sebold; Kirk, Renee; Howell, Alan; Evans, Elizabeth E; Paris, Mark; Bowers, William J; John, Gareth; Zauderer, Maurice

    2015-01-01

    Multiple sclerosis (MS) is a chronic neuroinflammatory disease characterized by immune cell infiltration of CNS, blood-brain barrier (BBB) breakdown, localized myelin destruction, and progressive neuronal degeneration. There exists a significant need to identify novel therapeutic targets and strategies that effectively and safely disrupt and even reverse disease pathophysiology. Signaling cascades initiated by semaphorin 4D (SEMA4D) induce glial activation, neuronal process collapse, inhibit migration and differentiation of oligodendrocyte precursor cells (OPCs), and disrupt endothelial tight junctions forming the BBB. To target SEMA4D, we generated a monoclonal antibody that recognizes mouse, rat, monkey and human SEMA4D with high affinity and blocks interaction between SEMA4D and its cognate receptors. In vitro, anti-SEMA4D reverses the inhibitory effects of recombinant SEMA4D on OPC survival and differentiation. In vivo, anti-SEMA4D significantly attenuates experimental autoimmune encephalomyelitis in multiple rodent models by preserving BBB integrity and axonal myelination and can be shown to promote migration of OPC to the site of lesions and improve myelin status following chemically-induced demyelination. Our study underscores SEMA4D as a key factor in CNS disease and supports the further development of antibody-based inhibition of SEMA4D as a novel therapeutic strategy for MS and other neurologic diseases with evidence of demyelination and/or compromise to the neurovascular unit.

  1. X-Ray Spectral Study of the Photoionized Stellar Wind in Vela X-1

    SciTech Connect

    Watanabe, Shin; Sako, Masao; Ishida, Manabu; Ishisaki, Yoshitaka; Kahn, Steven M.; Kohmura, Takayoshi; Nagase, Fumiaki; Paerels, Frederik; Takahashi, Tadayuki; /JAXA, Sagamihara /KIPAC, Menlo Park /Tokyo Metropolitan U. /Kogakuin U. /Columbia U., Astron. Astrophys.

    2006-07-10

    We present results from quantitative modeling and spectral analysis of the high mass X-ray binary system Vela X-1 obtained with the Chandra High Energy Transmission Grating Spectrometer. The observations cover three orbital phase ranges within a single binary orbit. The spectra exhibit emission lines from H-like and He-like ions driven by photoionization, as well as fluorescent emission lines from several elements in lower charge states. The properties of these X-ray lines are measured with the highest accuracy to date. In order to interpret and make full use of the high-quality data, we have developed a simulator, which calculates the ionization and thermal structure of a stellar wind photoionized by an X-ray source, and performs Monte Carlo simulations of X-ray photons propagating through the wind. The emergent spectra are then computed as a function of the viewing angle accurately accounting for photon transport in three dimensions including dynamics. From comparisons of the observed spectra with results from the simulator, we are able to find the ionization structure and the geometrical distribution of material in the stellar wind of Vela X-1 that can reproduce the observed spectral line intensities and continuum shapes at different orbital phases remarkably well. We find that the stellar wind profile can be represented by a CAK-model with a star mass loss rate of (1.5-2.0) x 10{sup -6} M{sub {circle_dot}} yr{sup -1}, assuming a terminal velocity of 1100 km s{sup -1}. It is found that a large fraction of X-ray emission lines from highly ionized ions are formed in the region between the neutron star and the companion star. We also find that the fluorescent X-ray lines must be produced in at least three distinct regions: (1) the extended stellar wind, (2) reflection off the stellar photosphere, and (3) in a distribution of dense material partially covering and possibly trailing the neutron star, which may be associated with an accretion wake. Finally, from

  2. Photoionization of Phosphorus cation induced by synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Juárez, Antonio; Aguilar, Alejandro; González, Olmo; Macaluso, David; Antillón, Armando; Morales, Alejandro; Hanstorp, Dag; Covington, Aaron; Chartkunchand, Kiattichart; Hinojosa, Guillermo; Nahar, Sultana; Hernández, Edgar

    2013-09-01

    The photoionization of Phosphorus cation has been measured in the photon energy range of 18 eV to 50 eV with 40 meV resolution. A theoretical investigation is being conducted while more experimentation is being planned. The ALS is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. DOE Contract No. DE-AC02-05CH11231. AMC acknowledges financial support from the US DOE NNSA through Cooperative Agreement DE-FC52-06NA27616. DGAPA IN 113010, IN106813 and CONACYT CB-2011/167631. GH thanks technical support of ALS staff.

  3. Experimental observation of guanine tautomers with VUV photoionization

    SciTech Connect

    Zhou, Jia; Kostko, Oleg; Nicolas, Christophe; Tang, Xiaonan; Belau, Leonid; de Vries, Mattanjah S.; Ahmed, Musahid

    2008-12-01

    Two methods of preparing guanine in the gas phase, thermal vaporization and laser desorption, have been investigated. The guanine generated by each method is entrained in a molecular beam, single photon ionized with tunable VUV synchrotron radiation, and analyzed using reflectron mass spectrometry. The recorded photoionization efficiency (PIE) curves show a dramatic difference for experiments performed via thermal vaporization compared to laser desorption. The calculated vertical and adiabatic ionization energies for the eight lowest lying tautomers of guanine suggest the experimental observations arise from different tautomers being populated in the two different experimental methods.

  4. Molecular photoionization studies of nucleobases and correlated systems

    SciTech Connect

    Poliakoff, Erwin D.

    2015-03-11

    We proposed molecular photoionization studies in order to probe correlated events in fundamental scattering phenomena. In particular, we suggested that joint theoretical-experimental studies would provide a window into the microscopic aspects that are of central importance in AMO and chemical physics generally, and would generate useful data for wide array of important DOE topics, such as ultrafast dynamics, high harmonic generation, and probes of nonadiabatic processes. The unifying theme is that correlations between electron scattering dynamics and molecular geometry highlight inherently molecular aspects of the photoelectron behavior.

  5. A simple photoionization scheme for characterizing electron and ion spectrometers

    NASA Astrophysics Data System (ADS)

    Wituschek, A.; von Vangerow, J.; Grzesiak, J.; Stienkemeier, F.; Mudrich, M.

    2016-08-01

    We present a simple diode laser-based photoionization scheme for generating electrons and ions with well-defined spatial and energetic (≲2 eV) structures. This scheme can easily be implemented in ion or electron imaging spectrometers for the purpose of off-line characterization and calibration. The low laser power ˜1 mW needed from a passively stabilized diode laser and the low flux of potassium atoms in an effusive beam make our scheme a versatile source of ions and electrons for applications in research and education.

  6. The photoionization spectrum of neutral aluminium, Al I

    NASA Technical Reports Server (NTRS)

    Roig, R. A.

    1975-01-01

    The absorption spectrum of Al I has been studied for the wavelength range 1160 to 2000 A by the flash pyrolysis technique. Wavelengths and derived energy levels are reported for 70 new lines converging on the 3s3p(3)P(0) limits of Al II. The autoionization parameters of the 3p(2)P(0)-3p(2)(2)S doublet have been measured. Good agreement is obtained with the experiment of Kohl and Parkinson and the recent calculation of Le Dourneuf et al. The relative photoionization cross section has been measured in the wavelength region 1200 A to 2000 A.

  7. Ab initio calculations of the photoionization of diatomic molecules

    NASA Astrophysics Data System (ADS)

    Lefebvre-Brion, Helene; Raşeev, Georges

    2003-01-01

    A review is presented of the calculation of photoionization spectra, particularly in the spectral range where electron autoionization of diatomic molecules takes place. In addition to some interesting results obtained over years that compare favourably with experiment, the emphasis here is put on the relation between the methods developed for the calculation of observables associated with the continuum energy spectrum of the electrons and the Alchemy system of programs. This system of programs serves as a basis for initial and intermediate calculations. The examples presented show that diatomic molecules not only in gas phase but also oriented in space or physisorbed at surfaces may be studied readily.

  8. Photo-ionization and residual electron effects in guided streamers

    NASA Astrophysics Data System (ADS)

    Wu, S.; Lu, X.; Liu, D.; Yang, Y.; Pan, Y.; Ostrikov, K.

    2014-10-01

    Complementary experiments and numerical modeling reveal the important role of photo-ionization in the guided streamer propagation in helium-air gas mixtures. It is shown that the minimum electron concentration ˜108 cm-3 is required for the regular, repeated propagation of the plasma bullets, while the streamers propagate in the stochastic mode below this threshold. The stochastic-to-regular mode transition is related to the higher background electron density in front of the propagating streamers. These findings help improving control of guided streamer propagation in applications from health care to nanotechnology and improve understanding of generic pre-breakdown phenomena.

  9. A simple photoionization scheme for characterizing electron and ion spectrometers.

    PubMed

    Wituschek, A; von Vangerow, J; Grzesiak, J; Stienkemeier, F; Mudrich, M

    2016-08-01

    We present a simple diode laser-based photoionization scheme for generating electrons and ions with well-defined spatial and energetic (≲2 eV) structures. This scheme can easily be implemented in ion or electron imaging spectrometers for the purpose of off-line characterization and calibration. The low laser power ∼1 mW needed from a passively stabilized diode laser and the low flux of potassium atoms in an effusive beam make our scheme a versatile source of ions and electrons for applications in research and education. PMID:27587098

  10. Short-time Chebyshev wave packet method for molecular photoionization

    NASA Astrophysics Data System (ADS)

    Sun, Zhaopeng; Zheng, Yujun

    2016-08-01

    In this letter we present the extended usage of short-time Chebyshev wave packet method in the laser induced molecular photoionization dynamics. In our extension, the polynomial expansion of the exponential in the time evolution operator, the Hamiltonian operator can act on the wave packet directly which neatly avoids the matrix diagonalization. This propagation scheme is of obvious advantages when the dynamical system has large Hamiltonian matrix. Computational simulations are performed for the calculation of photoelectronic distributions from intense short pulse ionization of K2 and NaI which represent the Born-Oppenheimer (BO) model and Non-BO one, respectively.

  11. Photoionization and fragmentaton of (N2O)n clusters

    NASA Astrophysics Data System (ADS)

    Kamke, W.; Kamke, B.; Kiefl, H. U.; Hertel, I. V.

    1986-02-01

    A supersonic molecular beam and monochromatized synchrotron radiation are presently used to measure photoionization efficiency curves for (N2O)n, at n = 1-6, in the 55-110 nm wavelength region. By measuring the energy loss of cluster ions which fragment in a field free drift region of the ion source, it becomes possible to detect delayed unimolecular and collision-induced fragmentations of the cluster ions. From a study of the dependence of the 'metastable' signals on background pressure, it appears that only the removal of a single N2O molecule at a time can occur by unimolecular decay.

  12. Photo-ionization and residual electron effects in guided streamers

    SciTech Connect

    Wu, S.; Lu, X. Liu, D.; Yang, Y.; Pan, Y.; Ostrikov, K.

    2014-10-15

    Complementary experiments and numerical modeling reveal the important role of photo-ionization in the guided streamer propagation in helium-air gas mixtures. It is shown that the minimum electron concentration ∼10{sup 8 }cm{sup −3} is required for the regular, repeated propagation of the plasma bullets, while the streamers propagate in the stochastic mode below this threshold. The stochastic-to-regular mode transition is related to the higher background electron density in front of the propagating streamers. These findings help improving control of guided streamer propagation in applications from health care to nanotechnology and improve understanding of generic pre-breakdown phenomena.

  13. Geometric validation of self-gating k-space-sorted 4D-MRI vs 4D-CT using a respiratory motion phantom

    SciTech Connect

    Yue, Yong Yang, Wensha; McKenzie, Elizabeth; Tuli, Richard; Wallace, Robert; Fraass, Benedick; Fan, Zhaoyang; Pang, Jianing; Deng, Zixin; Li, Debiao

    2015-10-15

    Purpose: MRI is increasingly being used for radiotherapy planning, simulation, and in-treatment-room motion monitoring. To provide more detailed temporal and spatial MR data for these tasks, we have recently developed a novel self-gated (SG) MRI technique with advantage of k-space phase sorting, high isotropic spatial resolution, and high temporal resolution. The current work describes the validation of this 4D-MRI technique using a MRI- and CT-compatible respiratory motion phantom and comparison to 4D-CT. Methods: The 4D-MRI sequence is based on a spoiled gradient echo-based 3D projection reconstruction sequence with self-gating for 4D-MRI at 3 T. Respiratory phase is resolved by using SG k-space lines as the motion surrogate. 4D-MRI images are reconstructed into ten temporal bins with spatial resolution 1.56 × 1.56 × 1.56 mm{sup 3}. A MRI-CT compatible phantom was designed to validate the performance of the 4D-MRI sequence and 4D-CT imaging. A spherical target (diameter 23 mm, volume 6.37 ml) filled with high-concentration gadolinium (Gd) gel is embedded into a plastic box (35 × 40 × 63 mm{sup 3}) and stabilized with low-concentration Gd gel. The phantom, driven by an air pump, is able to produce human-type breathing patterns between 4 and 30 respiratory cycles/min. 4D-CT of the phantom has been acquired in cine mode, and reconstructed into ten phases with slice thickness 1.25 mm. The 4D images sets were imported into a treatment planning software for target contouring. The geometrical accuracy of the 4D MRI and CT images has been quantified using target volume, flattening, and eccentricity. The target motion was measured by tracking the centroids of the spheres in each individual phase. Motion ground-truth was obtained from input signals and real-time video recordings. Results: The dynamic phantom has been operated in four respiratory rate (RR) settings, 6, 10, 15, and 20/min, and was scanned with 4D-MRI and 4D-CT. 4D-CT images have target

  14. Research on fluorescence from photoionization, photodissociation, and vacuum, along with bending quantrum study

    NASA Technical Reports Server (NTRS)

    Judge, D. L.

    1975-01-01

    Reports of research concerning the fluorescence of CS2 are presented. Fluorescence from fragments of CS2 vapor produced by vacuum ultraviolet radiation, and fluorescence from photoionization of CS2 vapor are discussed along with fluorescence produced by photodissociation of CS2, and fluorescence from photoionization of OCS.

  15. Stringy origin of 4d black hole microstates

    NASA Astrophysics Data System (ADS)

    Bianchi, M.; Morales, J. F.; Pieri, L.

    2016-06-01

    We derive a precise dictionary between micro-state geometries and open string condensates for a large class of excitations of four dimensional BPS black holes realised in terms of D3-branes intersecting on a six-torus. The complete multipole expansion of the supergravity solutions at weak coupling is extracted from string amplitudes involving one massless closed string and multiple open strings insertions on disks with mixed boundary conditions.

  16. The role of semaphorin 4D in tumor development and angiogenesis in human breast cancer

    PubMed Central

    Jiang, Hongchao; Chen, Ceshi; Sun, Qiangming; Wu, Jing; Qiu, Lijuan; Gao, Change; Liu, Weiqing; Yang, Jun; Jun, Nie; Dong, Jian

    2016-01-01

    Background Semaphorin 4D (Sema4D) is highly expressed in certain types of tumors and functions in the regulation of tumor angiogenesis and growth. However, it is still not clear regarding the roles of Sema4D in breast cancer. This study was designed to explore the effects of Sema4D on proliferation, cell cycle progression, apoptosis, invasion, migration, tumor growth, and angiogenesis in breast cancer. Materials and methods The expression level of Sema4D was investigated in MCF10A, 184A1, HCC1937, MDA-MB-468, MDA-MB-231, Hs578T, BT474, MCF-7, and T47D breast cancer cell lines by Western blotting analysis. Sema4D downregulation or overexpression was established by infection with lentiviruses-encoding Sema4D short hairpin RNA (shRNA) or Sema4D. To evaluate the effects of Sema4D on cell proliferation, cell cycle progression, apoptosis, invasion, and migration of MDA-MB-231 and MDA-MB-468 cells, methods including MTT assay, flow cytometry, wound healing assay, and transwell experiments were applied. BALB/c nude mice were injected with MDA-MB-231 cells, which were respectively infected with lentiviruses-encoding Sema4D, Sema4D shRNA, and GFP, followed by tumor angiogenesis assay. Results Sema4D was expressed at higher levels in breast cancer cell lines compared with the normal human breast epithelial cell lines, especially in MDA-MB-231 and MDA-MB-468 cells. Cell proliferation ability was remarkably inhibited in Sema4D downregulated condition, whereas the proportions of cells in the G0/G1 phase and apoptosis increased in MDA-MB-231 and MDA-MB-468 cells. In addition, the invasion and migration abilities of these cells were obviously reduced. Xenograft growth as well as angiogenesis was inhibited when infected with lentiviruses-encoding Sema4D shRNA in vivo. Conclusion Downregulation of Sema4D had notable influence on cell proliferation ability, invasion, migration, and apoptosis of both MDA-MB-231 and MDA-MB-468 cells. Furthermore, infection with lentiviruses

  17. IMRT treatment planning on 4D geometries for the era of dynamic MLC tracking.

    PubMed

    Suh, Yelin; Murray, Walter; Keall, Paul J

    2014-12-01

    The problem addressed here was to obtain optimal and deliverable dynamic multileaf collimator (MLC) leaf sequences from four-dimensional (4D) geometries for dynamic MLC tracking delivery. The envisaged scenario was where respiratory phase and position information of the target was available during treatment, from which the optimal treatment plan could be further adapted in real time. A tool for 4D treatment plan optimization was developed that integrates a commercially available treatment planning system and a general-purpose optimization system. The 4D planning method was applied to the 4D computed tomography planning scans of three lung cancer patients. The optimization variables were MLC leaf positions as a function of monitor units and respiratory phase. The objective function was the deformable dose-summed 4D treatment plan score. MLC leaf motion was constrained by the maximum leaf velocity between control points in terms of monitor units for tumor motion parallel to the leaf travel direction and between phases for tumor motion parallel to the leaf travel direction. For comparison and a starting point for the 4D optimization, three-dimensional (3D) optimization was performed on each of the phases. The output of the 4D IMRT planning process is a leaf sequence which is a function of both monitor unit and phase, which can be delivered to a patient whose breathing may vary between the imaging and treatment sessions. The 4D treatment plan score improved during 4D optimization by 34%, 4%, and 50% for Patients A, B, and C, respectively, indicating 4D optimization generated a better 4D treatment plan than the deformable sum of individually optimized phase plans. The dose-volume histograms for each phase remained similar, indicating robustness of the 4D treatment plan to respiratory variations expected during treatment delivery. In summary, 4D optimization for respiratory phase-dependent treatment planning with dynamic MLC motion tracking improved the 4D treatment plan

  18. 2D:4D digit ratio predicts delay of gratification in preschoolers.

    PubMed

    Da Silva, Sergio; Moreira, Bruno; Da Costa, Newton

    2014-01-01

    We replicate the Stanford marshmallow experiment with a sample of 141 preschoolers and find a correlation between lack of self-control and 2D:4D digit ratio. Children with low 2D:4D digit ratio are less likely to delay gratification. Low 2D:4D digit ratio may indicate high fetal testosterone. If this hypothesis is true, our finding means high fetal testosterone children are less likely to delay gratification.

  19. 2D:4D Digit Ratio Predicts Delay of Gratification in Preschoolers

    PubMed Central

    Da Silva, Sergio; Moreira, Bruno; Da Costa, Newton

    2014-01-01

    We replicate the Stanford marshmallow experiment with a sample of 141 preschoolers and find a correlation between lack of self-control and 2D:4D digit ratio. Children with low 2D:4D digit ratio are less likely to delay gratification. Low 2D:4D digit ratio may indicate high fetal testosterone. If this hypothesis is true, our finding means high fetal testosterone children are less likely to delay gratification. PMID:25490040

  20. Photoionization cross sections for O-like S IX: a Breit-Pauli R-matrix calculation

    NASA Astrophysics Data System (ADS)

    Tyndall, N. B.; Ramsbottom, C. A.; Hibbert, A.; Ferland, G.

    2015-08-01

    In this paper we present photoionization cross sections for the lowest five states of O-like S IX (1s22s22p4 3P0,1,2, 1D2, 1S0). The relativistic Breit-Pauli R-matrix codes were utilized including all terms of the 2s22p3, 2s2p4, 2p5, 2s22p23s, 3p, 3d and 2s2p33s, 3p, 3d configurations in the expansion of the collision wavefunction for S X. It was also found that to achieve convergence of the low-lying energy separations of the target levels, an additional 21 configuration functions needed to be included in the configuration interaction expansion, incorporating two-electron excitations from the 2s and 2p shells to the 3s, 3p and 3d shells. The present work thus constitutes the most sophisticated photoionization evaluation for ground and metastable levels of the S IX ion. Direct comparisons have been made with the only available data found on the OPEN-ADAS database between level resolved contributions of the spectrum. This comparison for the background cross section exhibits excellent agreement at all photon energies for each partial photoionization cross section contribution investigated. Finally, the autoionizing bound states arising from numerous open channels have also been investigated and identified using the QB approach, a procedure for analyzing resonances in atomic and molecular collision theory which exploits the analytic properties of R-matrix theory. Major Rydberg resonance series are also presented and tabulated for the dominant linewidths considered.

  1. Resonance behavior of atomic and molecular photoionization amplitudes

    SciTech Connect

    Cherepkov, N. A.; Kuznetsov, V. V.; Semenov, S. K.

    2007-07-15

    The behavior of the partial photoionization amplitudes with a given orbital angular momentum l in the complex plane in resonances is studied. In the autoionization resonances the trajectory of the amplitude in the complex plane corresponds to a circle. With increasing photoelectron energy the amplitude moves about a circle in the counterclockwise direction. The new expressions for the partial amplitudes in the resonance are proposed which are similar to the Fano form but contain the 'partial' profile parameters which are connected with the Fano parameter q by a simple relation. In the giant dipole resonances the amplitudes in the complex plane also move about a circle in the counterclockwise direction provided the Coulomb phase is excluded from the amplitude. In the correlational resonances created by channel interactions with the giant dipole resonance the trajectories of the amplitudes acquire a loop about which the amplitudes move in the counterclockwise direction. Very similar behavior of partial photoionization amplitudes in the complex plane is demonstrated also for the dipole transitions from the K shells of the N{sub 2} molecule in the {sigma}* shape resonance.

  2. Relativistic Effects in the Photoionization of Very Heavy Atoms

    NASA Astrophysics Data System (ADS)

    Keating, David A.; Manson, Steven T.; Deshmukh, Pranawa C.

    2015-05-01

    At very high Z relativistic interactions become important contributors to even the qualitative nature of atomic properties. To explore the extent of relativistic interactions in the photoionization of a very heavy atom, a theoretical study of nobelium (Z = 102) has been performed using the relativistic random phase approximation (RRPA) methodology. In order to determine which features in the photoionization cross section are due to relativity, calculations using the (nonrelativistic) random phase approximation with exchange method (RPAE) are performed for comparison. With the inclusion of inter-channel coupling some relativistic effects are amplified or diminished. To distinguish which relativistic effects are native to the orbital of interest or a product of inter-channel coupling, calculations have been performed with and without coupling for comparison. Aside from significant splitting and shifts of threshold, induced effects on subshells not strongly affected by relativity directly, e.g. outer shells, by inner subshells that are strongly affected, occur via changes in screening and inter-channel coupling.

  3. Kr photoionized plasma induced by intense extreme ultraviolet pulses

    NASA Astrophysics Data System (ADS)

    Bartnik, A.; Wachulak, P.; Fiedorowicz, H.; Skrzeczanowski, W.

    2016-04-01

    Irradiation of any gas with an intense EUV (extreme ultraviolet) radiation beam can result in creation of photoionized plasmas. The parameters of such plasmas can be significantly different when compared with those of the laser produced plasmas (LPP) or discharge plasmas. In this work, the photoionized plasmas were created in a krypton gas irradiated using an LPP EUV source operating at a 10 Hz repetition rate. The Kr gas was injected into the vacuum chamber synchronously with the EUV radiation pulses. The EUV beam was focused onto a Kr gas stream using an axisymmetrical ellipsoidal collector. The resulting low temperature Kr plasmas emitted electromagnetic radiation in the wide spectral range. The emission spectra were measured either in the EUV or an optical range. The EUV spectrum was dominated by emission lines originating from Kr III and Kr IV ions, and the UV/VIS spectra were composed from Kr II and Kr I lines. The spectral lines recorded in EUV, UV, and VIS ranges were used for the construction of Boltzmann plots to be used for the estimation of the electron temperature. It was shown that for the lowest Kr III and Kr IV levels, the local thermodynamic equilibrium (LTE) conditions were not fulfilled. The electron temperature was thus estimated based on Kr II and Kr I species where the partial LTE conditions could be expected.

  4. Photoionization mass spectrometry of combustion radicals. Final technical report

    SciTech Connect

    Cool, T.A.

    1998-12-31

    Fundamental research on the combustion of halogenated organic compounds with emphasis on reaction pathways leading to the formation of chlorinated organic compounds and the development of continuous emission monitoring methods will assist in DOE efforts in the management and control of hazardous chemical wastes. Selective laser ionization techniques are used in the laboratory for the measurement of concentration profiles of radical intermediates in chlorinated hydrocarbon flames. A novel flame-sampling VUV laser photoionization mass spectrometer, constructed with DOE funding, is in use for these studies. Progress is reported here on the use of this new facility in the development, refinement, and verification of chemical kinetic models describing the thermal destruction of toxic chlorocarbons commonly found in chemical wastes. In the past two years the author has used the flame sampling VUV laser ionization mass spectrometer system for studies of chlorocarbon-doped methane/oxygen flames. Relative concentration profiles and photoionization efficiency curves have been measured for over two-dozen key reaction intermediates. Preliminary kinetic models have been developed that promise an improved understanding of chlorocarbon chemistry under laboratory flame conditions.

  5. Attosecond delays in photoionization: time and quantum mechanics

    NASA Astrophysics Data System (ADS)

    Maquet, Alfred; Caillat, Jérémie; Taïeb, Richard

    2014-10-01

    This article addresses topics regarding time measurements performed on quantum systems. The motivation is linked to the advent of ‘attophysics’ which makes feasible to follow the motion of electrons in atoms and molecules, with time resolution at the attosecond (1 as = 10-18 s) level, i.e. at the natural scale for electronic processes in these systems. In this context, attosecond ‘time-delays’ have been recently measured in experiments on photoionization and the question arises if such advances could cast a new light on the still active discussion on the status of the time variable in quantum mechanics. One issue still debatable is how to decide whether one can define a quantum time operator with eigenvalues associated to measurable ‘time-delays’, or time is a parameter, as it is implicit in the Newtonian classical mechanics. One objective of this paper is to investigate if the recent attophysics-based measurements could shed light on this parameter-operator conundrum. To this end, we present here the main features of the theory background, followed by an analysis of the experimental schemes that have been used to evidence attosecond ‘time-delays’ in photoionization. Our conclusion is that these results reinforce the view that time is a parameter which cannot be defined without reference to classical mechanics.

  6. Efficient photoheating algorithms in time-dependent photoionization simulations

    NASA Astrophysics Data System (ADS)

    Lee, Kai-Yan; Mellema, Garrelt; Lundqvist, Peter

    2016-02-01

    We present an extension to the time-dependent photoionization code C2-RAY to calculate photoheating in an efficient and accurate way. In C2-RAY, the thermal calculation demands relatively small time-steps for accurate results. We describe two novel methods to reduce the computational cost associated with small time-steps, namely, an adaptive time-step algorithm and an asynchronous evolution approach. The adaptive time-step algorithm determines an optimal time-step for the next computational step. It uses a fast ray-tracing scheme to quickly locate the relevant cells for this determination and only use these cells for the calculation of the time-step. Asynchronous evolution allows different cells to evolve with different time-steps. The asynchronized clocks of the cells are synchronized at the times where outputs are produced. By only evolving cells which may require short time-steps with these short time-steps instead of imposing them to the whole grid, the computational cost of the calculation can be substantially reduced. We show that our methods work well for several cosmologically relevant test problems and validate our results by comparing to the results of another time-dependent photoionization code.

  7. Photoionization and photofragmentation of the C60+ molecular ion

    NASA Astrophysics Data System (ADS)

    Baral, K. K.; Aryal, N. B.; Esteves-Macaluso, D. A.; Thomas, C. M.; Hellhund, J.; Lomsadze, R.; Kilcoyne, A. L. D.; Müller, A.; Schippers, S.; Phaneuf, R. A.

    2016-03-01

    Cross-section measurements are reported for single and double photoionization of C60+ ions in the photon energy range 18-150 eV accompanied by the loss of zero to seven pairs of carbon atoms, as well as for fragmentation without ionization resulting in loss of two to eight pairs of C atoms in the photon energy range 18-65 eV. Absolute measurements were performed by merging a beam of C60+ molecular ions with a beam of monochromatized synchrotron radiation. Product channels involving dissociation yielding smaller fullerene fragment ions account for nearly half of the total measured oscillator strength in this energy range. The sum of cross sections for the measured product channels is compared to a published calculation of the total photoabsorption cross section of neutral C60 based on time-dependent density-functional theory. This comparison and an accounting of oscillator strengths indicate that with the exception of C58+, the most important product channels resulting from photoabsorption were accounted for in the experiment. Threshold energies for the successive removal of carbon atom pairs accompanying photoionization are also determined from the measurements.

  8. Heterozygous mutations in cyclic AMP phosphodiesterase-4D (PDE4D) and protein kinase A (PKA) provide new insights into the molecular pathology of acrodysostosis.

    PubMed

    Kaname, Tadashi; Ki, Chang-Seok; Niikawa, Norio; Baillie, George S; Day, Jonathan P; Yamamura, Ken-Ichi; Ohta, Tohru; Nishimura, Gen; Mastuura, Nobuo; Kim, Ok-Hwa; Sohn, Young Bae; Kim, Hyun Woo; Cho, Sung Yoon; Ko, Ah-Ra; Lee, Jin Young; Kim, Hyun Wook; Ryu, Sung Ho; Rhee, Hwanseok; Yang, Kap-Seok; Joo, Keehyoung; Lee, Jooyoung; Kim, Chi Hwa; Cho, Kwang-Hyun; Kim, Dongsan; Yanagi, Kumiko; Naritomi, Kenji; Yoshiura, Ko-Ichiro; Kondoh, Tatsuro; Nii, Eiji; Tonoki, Hidefumi; Houslay, Miles D; Jin, Dong-Kyu

    2014-11-01

    Acrodysostosis without hormone resistance is a rare skeletal disorder characterized by brachydactyly, nasal hypoplasia, mental retardation and occasionally developmental delay. Recently, loss-of-function mutations in the gene encoding cAMP-hydrolyzing phosphodiesterase-4D (PDE4D) have been reported to cause this rare condition but the pathomechanism has not been fully elucidated. To understand the pathogenetic mechanism of PDE4D mutations, we conducted 3D modeling studies to predict changes in the binding efficacy of cAMP to the catalytic pocket in PDE4D mutants. Our results indicated diminished enzyme activity in the two mutants we analyzed (Gly673Asp and Ile678Thr; based on PDE4D4 residue numbering). Ectopic expression of PDE4D mutants in HEK293 cells demonstrated this reduction in activity, which was identified by increased cAMP levels. However, the cells from an acrodysostosis patient showed low cAMP accumulation, which resulted in a decrease in the phosphorylated cAMP Response Element-Binding Protein (pCREB)/CREB ratio. The reason for this discrepancy was due to a compensatory increase in expression levels of PDE4A and PDE4B isoforms, which accounted for the paradoxical decrease in cAMP levels in the patient cells expressing mutant isoforms with a lowered PDE4D activity. Skeletal radiographs of 10-week-old knockout (KO) rats showed that the distal part of the forelimb was shorter than in wild-type (WT) rats and that all the metacarpals and phalanges were also shorter in KO, as the name acrodysostosis implies. Like the G-protein α-stimulatory subunit and PRKAR1A, PDE4D critically regulates the cAMP signal transduction pathway and influences bone formation in a way that activity-compromising PDE4D mutations can result in skeletal dysplasia. We propose that specific inhibitory PDE4D mutations can lead to the molecular pathology of acrodysostosis without hormone resistance but that the pathological phenotype may well be dependent on an over-compensatory induction

  9. 4D VMAT, gated VMAT, and 3D VMAT for stereotactic body radiation therapy in lung.

    PubMed

    Chin, E; Loewen, S K; Nichol, A; Otto, K

    2013-02-21

    Four-dimensional volumetric modulated arc therapy (4D VMAT) is a treatment strategy for lung cancers that aims to exploit relative target and tissue motion to improve organ at risk (OAR) sparing. The algorithm incorporates the entire patient respiratory cycle using 4D CT data into the optimization process. Resulting treatment plans synchronize the delivery of each beam aperture to a specific phase of target motion. Stereotactic body radiation therapy treatment plans for 4D VMAT, gated VMAT, and 3D VMAT were generated on three patients with non-small cell lung cancer. Tumour motion ranged from 1.4-3.4 cm. The dose and fractionation scheme was 48 Gy in four fractions. A B-spline transformation model registered the 4D CT images. 4D dose volume histograms (4D DVH) were calculated from total dose accumulated at the maximum exhalation. For the majority of OARs, gated VMAT achieved the most radiation sparing but treatment times were 77-148% longer than 3D VMAT. 4D VMAT plan qualities were comparable to gated VMAT, but treatment times were only 11-25% longer than 3D VMAT. 4D VMAT's improvement of healthy tissue sparing can allow for further dose escalation. Future study could potentially adapt 4D VMAT to irregular patient breathing patterns.

  10. 4D VMAT, gated VMAT, and 3D VMAT for stereotactic body radiation therapy in lung

    NASA Astrophysics Data System (ADS)

    Chin, E.; Loewen, S. K.; Nichol, A.; Otto, K.

    2013-02-01

    Four-dimensional volumetric modulated arc therapy (4D VMAT) is a treatment strategy for lung cancers that aims to exploit relative target and tissue motion to improve organ at risk (OAR) sparing. The algorithm incorporates the entire patient respiratory cycle using 4D CT data into the optimization process. Resulting treatment plans synchronize the delivery of each beam aperture to a specific phase of target motion. Stereotactic body radiation therapy treatment plans for 4D VMAT, gated VMAT, and 3D VMAT were generated on three patients with non-small cell lung cancer. Tumour motion ranged from 1.4-3.4 cm. The dose and fractionation scheme was 48 Gy in four fractions. A B-spline transformation model registered the 4D CT images. 4D dose volume histograms (4D DVH) were calculated from total dose accumulated at the maximum exhalation. For the majority of OARs, gated VMAT achieved the most radiation sparing but treatment times were 77-148% longer than 3D VMAT. 4D VMAT plan qualities were comparable to gated VMAT, but treatment times were only 11-25% longer than 3D VMAT. 4D VMAT's improvement of healthy tissue sparing can allow for further dose escalation. Future study could potentially adapt 4D VMAT to irregular patient breathing patterns.

  11. Dynamics of electron emission in double photoionization processes near the krypton 3d threshold

    NASA Astrophysics Data System (ADS)

    Penent, F.; Sheinerman, S.; Andric, L.; Lablanquie, P.; Palaudoux, J.; Becker, U.; Braune, M.; Viefhaus, J.; Eland, J. H. D.

    2008-02-01

    Two-electron emission following photoabsorption near the Kr 3d threshold is investigated both experimentally and theoretically. On the experimental side, electron/electron coincidences using a magnetic bottle time-of-flight spectrometer allow us to observe the complete double photo ionization (DPI) continua of selected Kr2+ final states, and to see how these continua are affected by resonant processes in the vicinity of the Kr 3d threshold. The analysis is based on a quantum mechanical approach that takes into account the contribution of three different processes: (A) Auger decay of the inner 3d vacancy with the associated post-collision interaction (PCI) effects, (B) capture of slow photoelectrons into discrete states followed by valence multiplet decay (VMD) of the excited ionic states and (C) valence shell DPI. The dominant process for each Kr2+(4p-2) final state is the photoionization of the inner shell followed by Auger decay of the 3d vacancies. Moreover, for the 4p-2(3P) and 4p-2(1D) final ionic states an important contribution comes from the processes of slow photoelectron capture followed by VMD as well as from double ionization of the outer shell involving also VMD.

  12. Photoionization of atoms and molecules studied by the Crank-Nicolson method

    NASA Astrophysics Data System (ADS)

    Bian, Xue-Bin

    2014-09-01

    The Crank-Nicolson (C-N) method combined with a B-spline basis set can be used in both time-dependent and time-independent calculations of the photoionization cross sections of atoms and molecules. For time-independent systems, the imaginary-time propagation (ITP) method can usually only converge an arbitrary initial state to the ground state directly. Contrary to existing methods, it is found that the C-N method can converge an arbitrary initial state directly to not only the ground state but also excited and continuum states by controlling the time-step size. It is very useful if one is interested in only part of the spectral information since the computation is relatively cheap. The C-N method can also be directly applied in time-dependent calculations. During the time evolution, the spectral information, such as energy and momentum, can be retrieved by projecting the wave function on the eigenstates obtained using the ITP method. Both time-dependent and time-independent calculations agree very well with previous results. This method can also be extended to two-electron systems directly.

  13. One-electron and multi-electron transitions observed in the excitation function of the dissociative photoionization excitation of ?

    NASA Astrophysics Data System (ADS)

    Kitajima, Masashi; Ukai, Masatoshi; Machida, Shuntaro; Kameta, Kosei; Ehresmann, Arno; Kouchi, Noriyuki; Hatano, Yoshihiko; Hayaishi, Tatsuji; Shigemasa, Eiji; Ito, Kenji

    1996-05-01

    The excitation function of the dissociative photoionization excitation ( DIE) of 0953-4075/29/9/017/img14 has been measured with the detection technique of coincidence between photoion 0953-4075/29/9/017/img15 and a fluorescence photon emitted from an excited atom N* using extreme- UV synchrotron radiation ( SR) as an excitation source in the energy region of 35 - 65 eV. The axis of the detection system was set at two angles, parallel or perpendicular with respect to the major axis of the elliptically polarized SR, in the present measurement. The coincidence spectra obtained in this energy region show at least two qualitatively different structures originating from two different DIE processes. The major components of the DIE in the present energy region are ascribed to the dissociation of the 0953-4075/29/9/017/img16 state which is strongly coupled with correlation states in the 0953-4075/29/9/017/img17 symmetry. In addition, DIE from other precursor states in the 0953-4075/29/9/017/img18 symmetry or dissociative photo-double ionization excitation ( DDIE) was also observed.

  14. Complex interactions between diapirs and 4-D subduction driven mantle wedge circulation.

    NASA Astrophysics Data System (ADS)

    Sylvia, R. T.; Kincaid, C. R.

    2015-12-01

    upon 2-D, steady-state thermal and flow regimes. We reiterate the importance of 4-D time evolution in subduction models. Analogue experiments allow added feedbacks and complexity improving intuition and providing insight for further investigation.

  15. Attempt of UAV oblique images and MLS point clouds for 4D modelling of roadside pole-like objects

    NASA Astrophysics Data System (ADS)

    Lin, Yi; West, Geoff

    2014-11-01

    The state-of-the-art remote sensing technologies, namely Unmanned Aerial Vehicle (UAV) based oblique imaging and Mobile Laser Scanning (MLS) show great potential for spatial information acquisition. This study investigated the combination of the two data sources for 4D modelling of roadside pole-like objects. The data for the analysis were collected by the Microdrone md4-200 UAV imaging system and the Sensei MLS system developed by the Finnish Geodetic Institute. Pole extraction, 3D structural parameter derivation and texture segmentation were deployed on the oblique images and point clouds, and their results were fused to yield the 4D models for one example of pole-like objects, namely lighting poles. The combination techniques proved promising.

  16. Estimate of Low/Mid-Latitude Conductances, Electric Potential and Neutral Winds using IDA4D and EMPIRE

    NASA Astrophysics Data System (ADS)

    Bust, G. S.; Makela, J. J.; Harding, B. J.; Heelis, R. A.; Bishop, R. L.

    2015-12-01

    In this talk we will focus on the current ability of the ionosphere-thermosphere data assimilative models, Ionospheric Data Assimilation Four Dimensional (IDA4D) and Estimating Model Parameters from Ionospheric Reverse Engineering (EMPIRE), to estimate low and mid latitude ionosphere-thermosphere (IT) state variables at altitudes of 200 km and less. In particular we focus on the estimation of Pederson and Hall conductances, equatorial electric potential, and neutral winds. We will characterize the current state of IDA4D and EMPIRE in terms of data available to be assimilated and geophysical conditions. We will discuss the accuracy expected for given conditions, current limitations, and to what degree data assimilative models can be used to advance our understanding of the low/mid latitude physics at 200 km and below. We will use three case study events to help elucidate the current capabilities of IDA4D and EMPIRE: The March, 2013 storm, the March 2015 storm, and the March 2014 time period, which was relatively quiet. In additional to the normal data sets ingested by IDA4D and EMPIRE we intend to ingest observation from the C/NOFS satellite including radio occultations, in-situ measurements of plasma density and ion drifts. We will also ingest other measurements related to electric fields from coherent scatter radars and magnetometers when available. Finally, we will ingest neutral wind measurements from FPI's. We will conclude with a discussion of the future of IT data assimilation algorithms, the advantages of coupling to first principle models, and what future satellite missions such as ICON, GOLD and COSMIC 2 will contribute to improved IT data assimilation estimates.

  17. Photoionization dynamics of glycine adsorbed on a silicon cluster: ''On-the-fly'' simulations

    SciTech Connect

    Shemesh, Dorit; Baer, Roi; Seideman, Tamar; Gerber, R. Benny

    2005-05-08

    Dynamics of glycine chemisorbed on the surface of a silicon cluster is studied for a process that involves single-photon ionization, followed by recombination with the electron after a selected time delay. The process is studied by ''on-the-fly'' molecular dynamics simulations, using the semiempirical parametric method number 3 (PM3) potential energy surface. The system is taken to be in the ground state prior to photoionization, and time delays from 5 to 50 fs before the recombination are considered. The time evolution is computed over 10 ps. The main findings are (1) the positive charge after ionization is initially mostly distributed on the silicon cluster. (2) After ionization the major structural changes are on the silicon cluster. These include Si-Si bond breaking and formation and hydrogen transfer between different silicon atoms. (3) The transient ionization event gives rise to dynamical behavior that depends sensitively on the ion state lifetime. Subsequent to 45 fs evolution in the charged state, the glycine molecule starts to rotate on the silicon cluster. Implications of the results to various processes that are induced by transient transition to a charged state are discussed. These include inelastic tunneling in molecular devices, photochemistry on conducting surfaces, and electron-molecule scattering.

  18. Teaching Tip: Managing Software Engineering Student Teams Using Pellerin's 4-D System

    ERIC Educational Resources Information Center

    Doman, Marguerite; Besmer, Andrew; Olsen, Anne

    2015-01-01

    In this article, we discuss the use of Pellerin's Four Dimension Leadership System (4-D) as a way to manage teams in a classroom setting. Over a 5-year period, we used a modified version of the 4-D model to manage teams within a senior level Software Engineering capstone course. We found that this approach for team management in a classroom…

  19. Elite collegiate tennis athletes have lower 2D: 4D ratios than those of nonathlete controls.

    PubMed

    Hsu, Cheng-Chen; Su, Borcherng; Kan, Nai-Wen; Lai, Su-Ling; Fong, Tsorng-Harn; Chi, Chung-Pu; Chang, Ching-Chyuan; Hsu, Mei-Chich

    2015-03-01

    The ratio of the length of the second finger (index finger) to the fourth finger (ring finger) (2D:4D ratio) is a putative marker for prenatal hormones. Physiological research has suggested a low 2D:4D ratio correlates with high athletic ability. Athletes of specific sports (e.g., American football) have lower 2D:4D ratios than those of nonathletes, whereas athletes of some sports (e.g., rowing, gymnastics, and soccer) do not. This study investigated the 2D:4D ratios among collegiate tennis athletes, elite collegiate tennis athletes, and nonelite collegiate tennis athletes and compared them with nonathletes of both sexes. The participants included 43 elite collegiate tennis athletes (Level I intercollegiate athletes in Taiwan; 27 males and 16 females), 107 nonelite collegiate tennis athletes (Level II athletes; 55 males and 52 females), and 166 nonathlete college students (80 males and 86 females). The principle findings suggest that (a) regardless of sex, collegiate tennis athletes have lower 2D:4D values than those of nonathletes; (b) elite collegiate tennis athletes have lower 2D:4D values than those of nonathletes; (c) among females but not males, athletes and nonelite athletes have lower 2D:4D values than those of nonathletes; and (d) males have lower 2D:4D values than those of females. PMID:25226321

  20. Elite collegiate tennis athletes have lower 2D: 4D ratios than those of nonathlete controls.

    PubMed

    Hsu, Cheng-Chen; Su, Borcherng; Kan, Nai-Wen; Lai, Su-Ling; Fong, Tsorng-Harn; Chi, Chung-Pu; Chang, Ching-Chyuan; Hsu, Mei-Chich

    2015-03-01

    The ratio of the length of the second finger (index finger) to the fourth finger (ring finger) (2D:4D ratio) is a putative marker for prenatal hormones. Physiological research has suggested a low 2D:4D ratio correlates with high athletic ability. Athletes of specific sports (e.g., American football) have lower 2D:4D ratios than those of nonathletes, whereas athletes of some sports (e.g., rowing, gymnastics, and soccer) do not. This study investigated the 2D:4D ratios among collegiate tennis athletes, elite collegiate tennis athletes, and nonelite collegiate tennis athletes and compared them with nonathletes of both sexes. The participants included 43 elite collegiate tennis athletes (Level I intercollegiate athletes in Taiwan; 27 males and 16 females), 107 nonelite collegiate tennis athletes (Level II athletes; 55 males and 52 females), and 166 nonathlete college students (80 males and 86 females). The principle findings suggest that (a) regardless of sex, collegiate tennis athletes have lower 2D:4D values than those of nonathletes; (b) elite collegiate tennis athletes have lower 2D:4D values than those of nonathletes; (c) among females but not males, athletes and nonelite athletes have lower 2D:4D values than those of nonathletes; and (d) males have lower 2D:4D values than those of females.