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Sample records for 4d photoionization states

  1. Quasibound continuum states in SiF4 (D~ 2A1) photoionization: Photoelectron-vibrational coupling

    NASA Astrophysics Data System (ADS)

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

    2007-06-01

    The authors report a fully vibrationally resolved photoelectron spectroscopy investigation of a nonplanar molecule studied over a range of excitation energies. Experimental results for all four fundamental vibrational modes are presented. In each case significant non-Franck-Condon effects are seen. The vibrational branching ratio for the totally symmetric mode ν1+ is found to be strongly affected by resonant excitation in the SiF4+ (D˜A12) photoionization channel. This is shown to be the result of two distinct shape resonances, which for the first time have been both confirmed by theoretical calculations. Vibrationally resolved Schwinger photoionization calculations are used to understand the vibronic coupling for the photoelectrons, both using ab initio and harmonic vibrational wave functions.

  2. 4d Photoionization of Free Singly Charged Xenon Ions

    NASA Astrophysics Data System (ADS)

    Gottwald, A.; Gerth, Ch.; Richter, M.

    1999-03-01

    Electron spectroscopy in direct 4d photoionization of free Xe+ ions has been realized for the first time, applying various timing and coincidence techniques to suppress and to monitor on line the strong fluctuating background. The ionization energies of 4d5/2 and 4d3/2 electrons of Xe+\\(5p5 2P3/2\\) and Xe+\\(5p5 2P1/2\\) were determined and compared to calculated RHF(CI) values and to corresponding results of neutral Xe\\(5p6 1S0\\) atoms to study the influence of the outer-shell electron occupation on the 4d-1 inner-shell process.

  3. Valence photoionization and resonant Auger decay of Sb{sub 4} clusters at resonances below the 4d ionization threshold

    SciTech Connect

    Urpelainen, S.; Niskanen, J.; Kettunen, J. A.; Huttula, M.; Aksela, H.

    2011-01-15

    The valence photoionization and resonant Auger decay at 4d resonances below the 4d ionization threshold in Sb{sub 4} clusters have been studied experimentally by means of photoelectron spectroscopy. The 4d absorption spectrum in the photon energy region from 30 to 36 eV has been recorded using the constant ionic state (CIS) partial electron yield (PEY), and the CIS spectra for various ionic states are presented. The photoelectron spectra at various resonant positions are recorded, and the results and their interpretation are presented. The findings provide experimental proof of the previous assignment of the various structures of the inner valence photoelectron spectrum.

  4. Double Photoionization into Double Core-Hole States in Xe

    SciTech Connect

    Hikosaka, Y.; Kaneyasu, T.; Shigemasa, E.; Lablanquie, P.; Penent, F.; Eland, J. H. D.; Aoto, T.; Ito, K.

    2007-05-04

    Double photoionization (DPI) leading to double core-hole states of Xe{sup 2+} 4d{sup -2} has been studied using a magnetic bottle time-of-flight spectrometer. The assignments of the Xe{sup 2+} 4d{sup -2} states are confirmed by the Auger lines extracted from fourfold coincidences including two photoelectrons and two Auger electrons. It is estimated that the core-core DPI into Xe{sup 2+} 4d{sup -2} at a photon energy of 301.6 eV has a favored cross section of about 0.3 MB. The intense core-core DPI is due to mixing of the 4d{sup -2} continuum with the 4p single photoionization, which is manifested in the relative intensities of the Xe{sup 2+} 4d{sup -2} components.

  5. 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.

  6. Photoionization of aligned molecular excited states

    NASA Astrophysics Data System (ADS)

    Appling, J. R.; White, M. G.; Kessler, W. J.; Fernandez, R.; Poliakoff, E. D.

    1988-02-01

    Photoelectron angular distributions of several excited states of NO have been measured in an effort to better elucidate the role of alignment in resonant multiphoton excitation processes of molecules. In contrast to previous molecular REMPI measurements on NO, (2+1) angular distributions taken for low rotational levels of the E 2Σ+ (4sσ) Rydberg state of NO exhibit complex angular behavior which is characteristic of strong spatial alignment of the optically prepared levels. Photoelectron angular distributions were also found to be strongly branch and J dependent with the lowest rotational levels of the R21+S11 branch exhibiting the full anisotropy expected for an overall three-photon process. Fluorescence anisotropies extracted from complementary two-photon fluorescence angular distribution measurements reveal small, but nonzero alignment in all rotational levels with J>1/2, in contrast to the photoelectron results. Additional photoelectron angular distributions taken for (1+1) REMPI via the A 2Σ+ (3sσ), v=0 state exhibit near ``cos2θ'' distributions characteristic of photoionization of unaligned target states. The observed photoelectron data are qualitatively interpreted on the basis of the angular momentum constraints of the excitation-induced alignment and photoionization dynamics which determine the observable moments in the angular distribution.

  7. A theoretical CMS-X α treatment of CH 3I photoionization dynamics: outer valence shell and iodine 4d levels

    NASA Astrophysics Data System (ADS)

    Powis, Ivan

    1995-12-01

    Continuum multiple scattering (CMS-X α) calculations are used to investigate methyl iodide photoionization dynamics. The validity of atomic versus molecular models of behaviour for the localised iodine 4d and 5p (lone pair) electrons, where conflicting experimental interpretations have been offered, is examined. A good account of all the available experimental data is obtained. While the calculations provide some limited support for an atomic-like description of the iodine 4d -1 phenomenological cross-section, the atomic picture has little validity for the 5p -1 ionization. Variations in both cross-section and β parameter which were previously ascribed to the Cooper minimum are identified to be more likely a core-valence shell interaction, opening above the 4d -1 threshold. The other valence shell channels are similarly affected. Significant l-wave mixing, induced by the molecular anisotropy, is found to result in the creation of mixed parity final states, contrary to the atomic model. In these circumstances odd and even harmonic components can interfere to create orientation (odd harmonic terms) in the photoelectron angular distribution (PAD). Molecule frame PADs are calculated and compared to experimental data for the ionization of oriented molecules, confirming an intuitive expectation of asymmetric electron emission from an asymmetric molecule. The CH 3 group therefore acts as a non-negligible perturbation, even on quite localised iodine 5p electrons, and the molecular environment is a paramount factor.

  8. 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.

  9. Photoionization spectrum of the B2A' state of HCO

    NASA Astrophysics Data System (ADS)

    Foltynowicz, Robert J.; Rupp, Wolfgang; Hedderich, Hartmut G.; Grant, Edward R.

    1999-12-01

    Formyl radicals, excited to specific rovibrational levels of the strongly bent B2A' state are photoionized to form vibrationally excited states of the linear cation by the absorption of a tunable pulse of ultraviolet light from a second laser. Strong and essentially continuous photoionization spectra, which appear at intervals lying 7000 and 12 000 cm -1 above the adiabatic threshold, establish that formyl radicals can be efficiently ionized with a large geometry change at both energies. Non-Franck-Condon intensities suggest multiquantum pathways for vibrational autoionization.

  10. On the electron wavepacket dynamics of photoionizing states

    NASA Astrophysics Data System (ADS)

    Takatsuka, Kazuo

    2014-06-01

    To study electron wavepacket dynamics of photoionizing states in polyatomic molecules, we discuss two crucial issues to be overcome in the theory of molecular electronic wavepacket dynamics in an intense laser field (Takatsuka and Yonehara 2011 Phys. Chem. Chem. Phys. 13 4987). One is about the description of the ionization process from electronically excited states composed of many multiply excited configuration-state functions. The other is how to reconstruct the electronic states remaining in the molecular site while electrons are flowing out of the molecular bounds. These are both critical to extend the realm of the theories of electron dynamics based on the so-called expansion (algebraic) method in terms of basis functions. To calculate the photoionization amplitude and thereby to estimate the time-dependent amount of electron loss from a molecule, we extract the electron flux (probability current density) from the electron wavepackets without use of scattering theory. This is justified by the success of the recent works by Bandrauk’s group for attosecond photoionization dynamics from the hydrogen molecule ion, who performed numerical integration of the relevant Schrödinger equation (Yuan et al 2013 J. Chem. Phys. 138 134316). A key feature in the present study, on the other hand, is to calculate the electron flux in terms of complex-valued NOs, which arise from the complex electronic wavepackets. Through the change of these NOs, we reconstruct the involved electronic configurations during the flow of electrons out of molecular regions. These repopulated electronic wavefunctions are (non-adiabatically) evolved in time under laser fields.

  11. State-resolved molecular photoionization dynamics of polyatomic systems: Effects of non-linear changes in molecular geometry

    NASA Astrophysics Data System (ADS)

    Miller, James Scott

    An important topic in the absorption of vacuum ultraviolet photons by molecules is the correlation between electronic and nuclear degrees of freedom during photoionization. However, no previous investigations have probed the correlation between bending excitation and photoejection dynamics over a wide spectral range. We present the first such studies by reporting the influence of bending excitation following CO2 3σu -1 and N2O 7σ-1 photoionization over the photon energy range (15 eV < hvexc < 200 eV). Using dispersed fluorescence spectroscopy in conjunction with synchrotron radiation, we determine the vibrational branching ratio v+ = (0,1,0)( 0,0,0) for the CO2+ (B 2Σu+) and N2O+ (A 2Σ+) electronic states. The relative rate of production of the υ2 = 1 upper vibrational state varies over a broad ionization energy range, and in ways that are largely unanticipated. These branching ratios exhibit a strong thermal dependence, and we are able to separate out effects due to hot-band excitation from those that are due to vibronic coupling. The data indicate that the continuum electron is responsible for the observed energy dependence in CO2 3σ u-1 photoionization. This is a previously unobserved result. Additional studies examine the influence of simultaneous excitation in the bending and symmetric stretching modes in N2O+ [A 2Σ+, v + = (1,1,0)] to determine the effect of changing the energy separation of vibronically coupled potential surfaces. Finally, the CF4 + [D 2A1, v+ = (1,0,0,0)/(0,0,0,0)] branching ratio is studied, which provides the first experimental observation of a predicted low-energy shape resonance in this photoionization pathway.

  12. Photoionization cross sections of the excited 3s3p 3Po state for atomic Mg

    NASA Astrophysics Data System (ADS)

    Wang, Guoli; Wan, Jianjie; Zhou, Xiaoxin

    2017-01-01

    The photoionization cross sections of the excited levels (3s3p 0,1,2,o 3P) of atomic Mg have been studied theoretically using both the nonrelativistic and fully relativistic R-matrix method. For the threshold cross sections, as previous nonrelativistic studies, present calculations show significant differences (a factor of 3) from former experimental values. Large discrepancies with experiment calls for additional measurements of the photoionization cross sections from the excited states of Mg.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Measurement of photoionization cross sections of the excited states of titanium, cobalt, and nickel

    SciTech Connect

    Cong Ran; Cheng Yi; Yang Jiajun; Fan Jianmei; Yao Guanxin; Ji Xuehan; Zheng Xianfeng; Cui Zhifeng

    2009-07-01

    Resonance-enhanced multiphoton ionization (REMPI) of Ti, Co, and Ni atoms has been investigated in the 285-320 nm region. We couple a laser-ablated metal target into a molecular beam to produce atoms. Ions produced from photoionization of the neutral atoms are monitored by a home-built time-of-flight mass spectrometer. Photoionization cross sections of the excited states of Ti, Co, and Ni were deduced from the dependence of the ion signal intensity on the laser intensity for photon energies close to the ionization threshold. The values obtained range from 0.2 to 6.0 Mb. No significant isotope dependence was found from measurements of the photoionization cross sections of {sup 46}Ti, {sup 47}Ti, {sup 48}Ti, {sup 58}Ni, and {sup 60}Ni.

  18. Trauma-related altered states of consciousness: exploring the 4-D model.

    PubMed

    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.

  19. Using vibrational branching ratios to probe initial and final state effects in molecular photoionization

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

    Recent computed and experimental results for ICN, BF3 and C6F6 will be presented. In ICN we consider the ionization leading to the X2 Π1/2,3/2 states of ICN+. We show how the geometry dependence of the initial state orbital can be studied using vibrational branching ratios. In C6F6, we consider the excitation of the effects of two prominent shape resonances on the symmetric stretching modes in the photoionization leading to the C 3B2u state of the ion. In BF3, the excitation of both the symmetric stretching and the degenerate asymmetric stretching modes are considered in the photoionization leading to the E2A1' state of the ion.

  20. 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.

  1. 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

  2. Vertical D4-D2-D0 Bound States on K3 Fibrations and Modularity

    NASA Astrophysics Data System (ADS)

    Bouchard, Vincent; Creutzig, Thomas; Diaconescu, Duiliu-Emanuel; Doran, Charles; Quigley, Callum; Sheshmani, Artan

    2017-03-01

    An explicit formula is derived for the generating function of vertical D4-D2-D0 bound states on smooth K3 fibered Calabi-Yau threefolds, generalizing previous results of Gholampour and Sheshmani. It is also shown that this formula satisfies strong modularity properties, as predicted by string theory. This leads to a new construction of vector valued modular forms which exhibit some of the features of a generalized Hecke transform.

  3. Bacteriophage Tail-Tube Assembly Studied by Proton-Detected 4D Solid-State NMR

    DOE PAGES

    Zinke, Maximilian; Fricke, Pascal; Samson, Camille; ...

    2017-07-07

    Obtaining unambiguous resonance assignments remains a major bottleneck in solid-state NMR studies of protein structure and dynamics. Particularly for supramolecular assemblies with large subunits (>150 residues), the analysis of crowded spectral data presents a challenge, even if three-dimensional (3D) spectra are used. Here, we present a proton-detected 4D solid-state NMR assignment procedure that is tailored for large assemblies. The key to recording 4D spectra with three indirect carbon or nitrogen dimensions with their inherently large chemical shift dispersion lies in the use of sparse non-uniform sampling (as low as 2 %). As a proof of principle, we acquired 4D (H)COCANH,more » (H)CACONH, and (H)CBCANH spectra of the 20 kDa bacteriophage tail-tube protein gp17.1 in a total time of two and a half weeks. These spectra were sufficient to obtain complete resonance assignments in a straightforward manner without use of previous solution NMR data.« less

  4. 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.

  5. Competition between ultrafast relaxation and photoionization in excited prefluorescent states of tryptophan and indole

    NASA Astrophysics Data System (ADS)

    Sherin, P. S.; Snytnikova, O. A.; Tsentalovich, Yu. P.; Sagdeev, R. Z.

    2006-10-01

    The quantum yield of photoionization of TrpH and IndH from the nonrelaxed prefluorescent state S* increases with the temperature decrease. This effect is attributed to the competition between temperature independent ionization and ultrafast thermal relaxation S*→S1. The rate constant of the relaxation does not depend on the solvent and on the presence of the amino acid side chain: the temperature dependences of photoionization quantum yield, obtained for TrpH and IndH in different solvents, practically coincide. The activation energy for the relaxation rate constant Er≈4.5kJ/mol probably corresponds to intramolecular process or to the formation of the vibronically excited transient complex between photoexcited molecule and solvent molecules.

  6. 3D and 4D Seismic Imaging in the Oilfield; the state of the art

    NASA Astrophysics Data System (ADS)

    Strudley, A.

    2005-05-01

    Seismic imaging in the oilfield context has seen enormous changes over the last 20 years driven by a combination of improved subsurface illumination (2D to 3D), increased computational power and improved physical understanding. Today Kirchhoff Pre-stack migration (in time or depth) is the norm with anisotropic parameterisation and finite difference methods being increasingly employed. In the production context Time-Lapse (4D) Seismic is of growing importance as a tool for monitoring reservoir changes to facilitate increased productivity and recovery. In this paper we present an overview of state of the art technology in 3D and 4D seismic and look at future trends. Pre-stack Kirchhoff migration in time or depth is the imaging tool of choice for the majority of contemporary 3D datasets. Recent developments in 3D pre-stack imaging have been focussed around finite difference solutions to the acoustic wave equation, the so-called Wave Equation Migration methods (WEM). Application of finite difference solutions to imaging is certainly not new, however 3D pre-stack migration using these schemes is a relatively recent development driven by the need for imaging complex geologic structures such as sub salt, and facilitated by increased computational resources. Finally there are a class of imaging methods referred to as beam migration. These methods may be based on either the wave equation or rays, but all operate on a localised (in space and direction) part of the wavefield. These methods offer a bridge between the computational efficiency of Kirchhoff schemes and the improved image quality of WEM methods. Just as 3D seismic has had a radical impact on the quality of the static model of the reservoir, 4D seismic is having a dramatic impact on the dynamic model. Repeat shooting of seismic surveys after a period of production (typically one to several years) reveals changes in pressure and saturation through changes in the seismic response. The growth in interest in 4D seismic

  7. 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.

  8. Charge state distributions after K-shell photoionization of K and Ar atoms

    NASA Astrophysics Data System (ADS)

    Hertlein, Marcus; Belkacem, Ali; Cole, Kyra; Feinberg, Benedict; Maddi, Jason; Prior, Michael; Schriel, Ralf

    2003-05-01

    We have investigated K-shell photoionization of Ar and K at the Advanced Light Source to unravel the effect of the 4s electron of K on the relaxation of the K-shell hole. We measured the charge state distribution as a function of photon energy as it is varied across the respective K-edges of both atoms. Both Ar and K exhibit a very similar mean charge state after the interaction with the photons, with 4+ being the most probable charge state. However our first analysis shows a markedly different envelope of the charge state distribution. We will present the ratio of probabilities Ar(q+)/K(q+) for each charge state q as a function of the x-ray energy normalized to the K-edge energy of each atom.

  9. 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.

  10. State-To Dynamics of Photoionization and Charge Transfer Reactions Involving Hydrogen Bromide.

    NASA Astrophysics Data System (ADS)

    Xie, Jinchun

    The selection rules for electric-dipole-allowed photoionization of diatomic molecule are derived. From a single rotational level of neutral molecules, the final rotational levels of the ions can be accessed only when their angular momentum, parity, spin, and other quantum numbers satisfy certain relations concerning photoelectron partial waves. Furthermore, under irreducible tensor treatment photoionization probability is simply expressed by three factors: the geometrical coefficient C^ {k}_{p} the rotational linestrength S^{k}_{p } and the square of the tensor moment < {bf T}^{k} _{p}>. This method makes photoionization and electron impact induced transitions as easy to interpret as the well known multiphoton transition. The photoionization HBr^*(nu,J) + hnu to HBr ^+(^2Pi_{i},nu ^+,J^+) + e^- has been studied experimentally. The HBr^*(nu,J) is prepared in three 5ppi Rydberg states: f ^3Delta_2, g ^3Sigma^-_0 ^+ and F ^1Delta _2 via 2-photon excitation, and the product HBr^+(^2Pi_{i} ,nu^+,J^+ ) is probed in a quantum state specific manner using laser induced fluorescence (LIF). Distributions of the HBr^+ product show very strong parity propensities for the type of transition (+/- )-(mp), and also rotational propensities: Delta J = +/-1.5, +/-0.5 for the type of transition (+/-)-( mp) and Delta J = +/-2.5, +/-1.5, +/-0.5 for (+/-)-( +/-). These results are able to be described by using selection rules and irreducible moment presentation. The charge-transfer reaction DBr^+( ^2Pi_{i},nu^+,J ^+) + HBr to HBr ^+(^2Pi_{i^{ '}},nu^{'+ },J^{'+}) + DBr is studied under thermal conditions in a flowing gas mixture of HBr and DBr. The DBr^+(^2Pi _{i},nu^+,J^+) reagent is prepared by using (2 + 1) resonance enhanced multiphoton ionization and the HBr^+(^2 Pi_{i^{'+} },nu^{'+},J^ {'+}) product is detected using LIF. From the measurements of the molecular density and the populations of both HBr^+ and DBr^+, the absolute rate constants k(i,nu^+to i^', nu^{'+}) are determined for

  11. Molecular Structure and Dynamics Probed by Photoionization Out of Rydberg States

    NASA Astrophysics Data System (ADS)

    Rudakov, Fedor

    2017-06-01

    Probing the structure of a molecule as a chemical reaction unfolds has been a long standing goal in chemical physics. Most spectroscopic and diffraction techniques work well when the molecules are cold and thus vibrational motion is minimized. Yet, the very ability of a molecule to undergo structural changes implies that a significant amount of energy resides within the molecule. In order to probe structures of even medium sized molecules on an ultrafast time scale a technique that is sensitive to the molecular structure, yet insensitive to the vibrational motion is required. In our research we demonstrated that Rydberg electrons are remarkably sensitive to the molecular structure. Photoionization of a molecule out of Rydberg states reveals a purely electronic spectrum which is largely insensitive to vibrational motion. The talk illustrates how Rydberg electrons can serve as a probe for ultrafast structural dynamics in polyatomic molecules. The talk also demonstrates that photoionization through Rydberg states can be utilized for non-intrusive detection of polyatomic combustion intermediates in flames.

  12. 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})

  13. 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

    2014-09-07

    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.

  14. Controlling Two-Electron Threshold Dynamics in Double Photoionization of Lithium by Initial-State Preparation

    NASA Astrophysics Data System (ADS)

    Zhu, G.; Schuricke, M.; Steinmann, J.; Albrecht, J.; Ullrich, J.; Ben-Itzhak, I.; Zouros, T. J. M.; Colgan, J.; Pindzola, M. S.; Dorn, A.

    2009-09-01

    Double photoionization (DPI) and ionization-excitation (IE) of Li(2s) and Li(2p), state-prepared and aligned in a magneto-optical trap, were explored in a reaction microscope at the free-electron laser in Hamburg (FLASH). From 6 to 12 eV above threshold (ℏω=85, 91 eV), total as well as differential DPI cross sections were observed to critically depend on the initial state and, in particular, on the alignment of the 2p orbital with respect to the VUV-light polarization, whereas no effect is seen for IE. The alignment sensitivity is traced back to dynamical electron correlation at threshold.

  15. Controlling Two-Electron Threshold Dynamics in Double Photoionization of Lithium by Initial-State Preparation

    SciTech Connect

    Zhu, G.; Schuricke, M.; Steinmann, J.; Albrecht, J.; Dorn, A.; Ullrich, J.; Ben-Itzhak, I.; Zouros, T. J. M.; Colgan, J.; Pindzola, M. S.

    2009-09-04

    Double photoionization (DPI) and ionization-excitation (IE) of Li(2s) and Li(2p), state-prepared and aligned in a magneto-optical trap, were explored in a reaction microscope at the free-electron laser in Hamburg (FLASH). From 6 to 12 eV above threshold ((Planck constant/2pi)omega=85, 91 eV), total as well as differential DPI cross sections were observed to critically depend on the initial state and, in particular, on the alignment of the 2p orbital with respect to the VUV-light polarization, whereas no effect is seen for IE. The alignment sensitivity is traced back to dynamical electron correlation at threshold.

  16. A dissociative photoionization study of the c4Σu- state in O+2 using the TPEPICO technique

    NASA Astrophysics Data System (ADS)

    Padmanabhan, A.; MacDonald, M. A.; Ryan, C. H.; Zuin, L.; Reddish, T. J.

    2012-11-01

    In the dissociative photoionization (DPI) process, hν + O2 → O + O+ + e-, ionisation and dissociation both occur (either as a direct or indirect process) following photoabsorption. The Threshold Photoelectron Photoion Coincidence (TPEPICO) technique, i.e. measuring the coincidence yield between threshold photoelec-trons and photoions is a powerful way of studying the dynamics involved. The c4Σu- state in O+2 at ~ 24.56 eV has a shallow minimum in its potential that supports two distinct quasi-bound vibrational levels (v = 0, 1). We have investigated the angular distributions of 2 eV O+(4S) ions produced from DPI of O +2 c4Σu- (v = 0, 1) using the TPEPICO technique.

  17. 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.

  18. Photoionization of the cerium isonuclear sequence and cerium endohedral fullerene

    NASA Astrophysics Data System (ADS)

    Habibi, Mustapha

    This dissertation presents an experimental photoionization study of the cerium isonuclear sequence ions in the energy range of the 4d inner-shell giant resonance. In addition, single and double photoionization and photofragmentation cross sections of the cerium endohedral ion Ce C+82 were also measured and studied in the 4d excitation-ionization energy range of cerium. Relative and absolute cross-section measurements were performed at undulator beamline 10.0.1 of the Advanced Light Source (ALS) for nine parent cerium ions: Ce+ - Ce9+. Double-to-single ionization cross-section ratios were measured for photoionization of the endohedral Ce C+82 and empty fullerene C C+82 molecular ions. The merged ion and photon beams technique was used to conduct the experiments. Multiconfiguration Hartree-Fock calculations were performed as an aid to interpret the experimental data. Four Rydberg series for 4d → nf (n ≥ 4) and 4d → np (n ≥ 6) autoionizing excitations were assigned using the quantum defect theory for the Ce3+ photoionization cross section. The experimental data show the collapse of the nf wavefunctions (n ≥ 4) with increasing ionization stage as outer-shell electrons are stripped from the parent ion. The nf orbital collapse occurs partially for Ce2+ and Ce3+ ion and completely for Ce4+, where these wavefunctions penetrate the core region of the ion. A strong contribution to the total oscillator strength was observed in the double and triple photoionization channels for low charge states (Ce +, Ce2+, and Ce3+), whereas most of the 4d excitations of the higher charge states decay by ejection of one electron.

  19. 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.

  20. 4 d -inner-shell ionization of X e+ ions and subsequent Auger decay

    NASA Astrophysics Data System (ADS)

    Khalal, M. A.; Lablanquie, P.; Andric, L.; Palaudoux, J.; Penent, F.; Bučar, K.; Žitnik, M.; Püttner, R.; Jänkälä, K.; Cubaynes, D.; Guilbaud, S.; Bizau, J.-M.

    2017-07-01

    We have studied X e+4 d inner-shell photoionization in a direct experiment on X e+ ions, merging an ion and a photon beam and detecting the ejected electrons with a cylindrical mirror analyzer. The measured 4 d photoelectron spectrum is compared to the 4 d core valence double ionization spectrum of the neutral Xe atom, obtained with a magnetic bottle spectrometer. This multicoincidence experiment gives access to the spectroscopy of the individual X e2 +4 d-15 p-1 states and to their respective Auger decays, which are found to present a strong selectivity. The experimental results are interpreted with the help of ab initio calculations.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    Here, we extend the L2 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, N2, and H2O 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. Total photoionization cross-sections of excited electronic states by the algebraic diagrammatic construction-Stieltjes-Lanczos method.

    PubMed

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

    2014-05-14

    Here, we extend the L2 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, N2, and H2O 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.

  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. 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.

  6. 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.

  7. Ultrafast Elemental and Oxidation-State Mapping of Hematite by 4D Electron Microscopy.

    PubMed

    Su, Zixue; Baskin, J Spencer; Zhou, Wuzong; Thomas, John M; Zewail, Ahmed H

    2017-04-05

    We describe a new methodology that sheds light on the fundamental electronic processes that occur at the subsurface regions of inorganic solid photocatalysts. Three distinct kinds of microscopic imaging are used that yield spatial, temporal, and energy-resolved information. We also carefully consider the effect of photon-induced near-field electron microscopy (PINEM), first reported by Zewail et al. in 2009. The value of this methodology is illustrated by studying afresh a popular and viable photocatalyst, hematite, α-Fe2O3 that exhibits most of the properties required in a practical application. By employing high-energy electron-loss signals (of several hundred eV), coupled to femtosecond temporal resolution as well as ultrafast energy-filtered transmission electron microscopy in 4D, we have, inter alia, identified Fe(4+) ions that have a lifetime of a few picoseconds, as well as associated photoinduced electronic transitions and charge transfer processes.

  8. Dynamics of photoionization from molecular electronic wavepacket states in intense pulse laser fields: A nonadiabatic electron wavepacket study

    NASA Astrophysics Data System (ADS)

    Matsuoka, Takahide; Takatsuka, Kazuo

    2017-04-01

    A theory for dynamics of molecular photoionization from nonadiabatic electron wavepackets driven by intense pulse lasers is proposed. Time evolution of photoelectron distribution is evaluated in terms of out-going electron flux (current of the probability density of electrons) that has kinetic energy high enough to recede from the molecular system. The relevant electron flux is in turn evaluated with the complex-valued electronic wavefunctions that are time evolved in nonadiabatic electron wavepacket dynamics in laser fields. To uniquely rebuild such wavefunctions with its electronic population being lost by ionization, we adopt the complex-valued natural orbitals emerging from the electron density as building blocks of the total wavefunction. The method has been implemented into a quantum chemistry code, which is based on configuration state mixing for polyatomic molecules. Some of the practical aspects needed for its application will be presented. As a first illustrative example, we show the results of hydrogen molecule and its isotope substitutes (HD and DD), which are photoionized by a two-cycle pulse laser. Photon emission spectrum associated with above threshold ionization is also shown. Another example is taken from photoionization dynamics from an excited state of a water molecule. Qualitatively significant effects of nonadiabatic interaction on the photoelectron spectrum are demonstrated.

  9. Improved efficiency of selective photoionization of palladium isotopes via autoionizing Rydberg states

    NASA Astrophysics Data System (ADS)

    Locke, Clayton R.; Kobayashi, Tohru; Midorikawa, Katsumi

    2017-01-01

    Odd-mass-selective ionization of palladium for purposes of resource recycling and management of long-lived fission products can be achieved by exploiting transition selection rules in a well-established three-step excitation process. In this conventional scheme, circularly polarized lasers of the same handedness excite isotopes via two intermediate 2D5/2 core states, and a third laser is then used for ionization via autoionizing Rydberg states. We propose an alternative excitation scheme via intermediate 2D3/2 core states before the autoionizing Rydberg state, improving ionization efficiency by over 130 times. We confirm high selectivity and measure odd-mass isotopes of >99.7(3)% of the total ionized product. We have identified and measured the relative ionization efficiency of the series of Rydberg states that converge to upper ionization limit of the 4 d 9(2D3/2) level, and identify the most efficient excitation is via the Rydberg state at 67668.18(10) cm-1.

  10. Direct experimental evidence for dissociative photoionization of oxygen molecule via 2Σ(u)(-) ionic "optical dark" state.

    PubMed

    Tang, Xiaofeng; Zhou, Xiaoguo; Wu, Manman; Cai, Yu; Liu, Shilin; Sheng, Liusi

    2012-09-27

    Direct experimental evidence for dissociative photoionization of oxygen molecule via the (2)Σ(u)(-) ionic optical dark state is presented by an investigation using the method of threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging. Besides vibrational progress of the B(2)Σ(g)(-) state, several weak vibrational bands of the (2)Σ(u)(-) ionic optical dark state are observed concomitantly in an excitation energy range of 20.2-21.1 eV. Only O(+) fragments are detected in the whole excitation energy range; therefore, all vibrational bands are completely predissociative. TPEPICO three-dimensional time-sliced velocity images of O(+) fragments dissociated from vibrational state-selected O(2)(+)((2)Σ(u)(-),v(+)) ions are recorded. For the (2)Σ(u)(-)(v(+)=0-3) vibrational states, only the lowest dissociation channel of O(+)((4)S) + O((3)P) is observed. Once the photon energy is slightly increased to the (2)Σ(u)(-)(v(+)=4) level, a new concentric doughnut appears in the image, indicating that the second dissociation channel of O(+)((4)S) + O((1)D) is identified indeed. With the aid of potential energy curves, the dissociative mechanism of O(2)(+) in the (2)Σ(u)(-)(v(+)) state is proposed.

  11. Non-adiabatic molecular dynamics investigation of photoionization state formation and lifetime in Mn²⁺-doped ZnO quantum dots.

    PubMed

    Fischer, Sean A; Lingerfelt, David B; May, Joseph W; Li, Xiaosong

    2014-09-07

    The unique electronic structure of Mn(2+)-doped ZnO quantum dots gives rise to photoionization states that can be used to manipulate the magnetic state of the material and to generate zero-reabsorption luminescence. Fast formation and long non-radiative decay of this photoionization state is a necessary requirement for these important applications. In this work, surface hopping based non-adiabatic molecular dynamics are used to demonstrate the fast formation of a metal-to-ligand charge transfer state in a Mn(2+)-doped ZnO quantum dot. The formation occurs on an ultrafast timescale and is aided by the large density of states and significant mixing of the dopant Mn(2+) 3dt2 levels with the valence-band levels of the ZnO lattice. The non-radiative lifetime of the photoionization states is also investigated.

  12. Electron correlation in beryllium: Effects in the ground state, short-pulse photoionization, and time-delay studies

    NASA Astrophysics Data System (ADS)

    Omiste, Juan J.; Li, Wenliang; Madsen, Lars Bojer

    2017-05-01

    We apply a three-dimensional implementation of the time-dependent restricted-active-space self-consistent-field (TD-RASSCF) method to investigate effects of electron correlation in the ground state of Be as well as in its photoionization dynamics by short XUV pulses, including time delay in photoionization. First, we obtain the ground state by propagation in imaginary time. We show that the flexibility of the TD-RASSCF on the choice of the active orbital space makes it possible to consider only relevant active space orbitals, facilitating the convergence to the ground state compared to the multiconfigurational time-dependent Hartree-Fock method, used as a benchmark to show the accuracy and efficiency of TD-RASSCF. Second, we solve the equations of motion to compute photoelectron spectra of Be after interacting with a short linearly polarized XUV laser pulse. We compare the spectra for different RAS schemes, and in this way we identify the orbital spaces that are relevant for an accurate description of the photoelectron spectra. Finally, we investigate the effects of electron correlation on the magnitude of the relative Eisenbud-Wigner-Smith (EWS) time delay in the photoionization process into two different ionic channels. One channel, the ground-state channel in the ion, is accessible without electron correlation. The other channel is only accessible when including electron correlation. For theory beyond the mean-field time-dependent Hartree-Fock, the EWS time delay for the photon energy analyzed is quite insensitive to the considered active orbital spaces.

  13. Adaptive Ensemble Covariance Localization in Ensemble 4D-VAR State Estimation

    DTIC Science & Technology

    2011-04-01

    Tposterr (t)] 2 give the global average of the square of the posterior error of the state estimate in the tropo - sphere of zonal wind u, meridional...decreases with the cosine of latitude. To make sure that the errors pertained primarily to the tropo - sphere, only the lower 23 model levels

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

    DOE PAGES

    Calder, S.; Li, Ling; Okamoto, Satoshi; ...

    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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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 ({tildeB})1B1/(Ã)1A2, 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 ({tildeB})1B1 diabatic state is presented. Signatures of the oscillatory motion on the ({tildeB})1B1/(Ã)1A2 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 ({tildec})3B2 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.

  16. 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.

  17. Flash-photoionized nebulae

    NASA Technical Reports Server (NTRS)

    Katz, J. I.

    1989-01-01

    Under conditions of high radiation intensity and low gas density, recombination may be neglected in determining the ionization state of a photoionized gas. Calculations of the ionization structure of nebulae in this 'flash-photoionized' regime are reported. Very hard spectra of ionizing ultraviolet radiation may be produced by filtration of the ionizing flux through a neutral hydrogen layer which preferentially absorbs photons just above the hydrogen photoionization threshold. Fluxes with these hard spectra produce gas layer in which helium is largely doubly ionized while hydrogen is largely neutral. Such a layer leads to anomalously high ratios of He II to H I recombination line strengths. These results are applied to the problem of the spectrum of the arc in the cluster of galaxies A370. It is found that the spectrum may possibly be reconciled with the light echo model.

  18. Flash-photoionized nebulae

    SciTech Connect

    Katz, J.I.

    1989-05-01

    Under conditions of high radiation intensity and low gas density, recombination may be neglected in determining the ionization state of a photoionized gas. Calculations of the ionization structure of nebulae in this 'flash-photoionized' regime are reported. Very hard spectra of ionizing ultraviolet radiation may be produced by filtration of the ionizing flux through a neutral hydrogen layer which preferentially absorbs photons just above the hydrogen photoionization threshold. Fluxes with these hard spectra produce gas layer in which helium is largely doubly ionized while hydrogen is largely neutral. Such a layer leads to anomalously high ratios of He II to H I recombination line strengths. These results are applied to the problem of the spectrum of the arc in the cluster of galaxies A370. It is found that the spectrum may possibly be reconciled with the light echo model. 25 refs.

  19. 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.

  20. Single and double K-shell resonant photoionization and Auger decay of 1s → 2p excited states of O+-O4+

    NASA Astrophysics Data System (ADS)

    Zeng, Jiaolong; Li, Yongjun; Liu, Pengfei; Gao, Cheng; Yuan, Jianmin

    2017-09-01

    In this work, single and double photoionization cross sections in the vicinity of 1s → 2p resonances are investigated theoretically for quantum states belonging to the ground and first excited configurations of O+-O4+. R-matrix method has been employed to obtain the single ionization cross section, whereas the double ionization cross sections are obtained by the branching ratios of the direct double Auger decay to the total Auger decay. By analyzing possible double ionization pathways, we conclude that the double photoionization originates predominately from the direct double Auger decay of the K-shell resonant states. Our theoretical work diagnosed the population fraction of the quantum state prepared in a recent experiment and successfully interpreted the experimental observations on both single and double photoionization cross sections.

  1. Excited-state decay of hydrocarbon radicals, investigated by femtosecond time-resolved photoionization: Ethyl, propargyl, and benzyl

    NASA Astrophysics Data System (ADS)

    Zierhut, Matthias; Noller, Bastian; Schultz, Thomas; Fischer, Ingo

    2005-03-01

    The excited state decay of the hydrocarbon radicals ethyl, C2H5; propargyl, C3H3; and benzyl, C7H7 was investigated by femtosecond time-resolved photoionization. Radicals were generated by flash pyrolysis of n-propyl nitrite, propargyl bromide, and toluene, respectively. It is shown that the 2A'2(3s) Rydberg state of ethyl excited at 250nm decays with a time constant of 20fs. No residual signal was observed at longer delay times. For the 3B12 state of propargyl excited at 255nm a slower decay with a time constant 50±10fs was determined. The 4B22 state of benzyl excited at 255nm decays within 150±30fs.

  2. How Evenly Can Approximate Density Functionals Treat the Different Multiplicities and Ionization States of 4d Transition Metal Atoms?

    PubMed

    Luo, Sijie; Truhlar, Donald G

    2012-11-13

    The ability of density functional theory to predict the relative energies of different spin states, especially for systems containing transition metal atoms, is of great importance for many applications. Here, in order to sort out the key factors determining accuracy, we compare the predictions of 60 density functional approximations of 10 different types [local spin density approximation, generalized gradient approximation (GGA), nonseparable gradient approximation (NGA), global-hybrid GGA, range-separated hybrid GGA, range-separated hybrid GGA plus molecular mechanics, meta-GGA, meta-NGA, global-hybrid meta-GGA, and range-separated hybrid meta-GGA] for their ability to represent the spin-flip transitions of all 4d transition metal atoms of groups 3-10 (Y through Pd) and their singly positive cations. We consider all 16 excitation energies connecting the ground states (of the neutral atoms and the cations) to their first excited states of different multiplicities, and we also consider all eight ionization potentials. We also test the Hartree-Fock method. All density functional and Hartree-Fock calculations are converged to a stable solution, in which the spatial symmetry is allowed to be completely broken to achieve the lowest possible energy solution. By analyzing the fractional subshell occupancies and spin contaminations, we are able to sort out the effects of s orbital vs d orbital bias and high-spin vs low-spin bias. A reliable functional should have little or no bias of either type rather than succeeding for a limited subset of cases by cancellation of errors. We find that the widely used correlations of spin splittings to percentage of Hartree-Fock exchange are not borne out by the data, and the correlation functionals also play a significant role. We eventually conclude that SOGGA11-X, B1LYP, B3V5LYP, and MPW3LYP are the most consistently reliable functionals for balanced treatments of 4d transition metal atoms and their cations.

  3. 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.

  4. 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.

  5. Observation of even-parity autoionization states of uranium by three-colour photoionization optogalvanic spectroscopy in U-Ne hollow cathode discharges

    NASA Astrophysics Data System (ADS)

    Mandal, P. K.; Seema, A. U.; Das, R. C.; Shah, M. L.; Dev, Vas; Suri, B. M.

    2013-07-01

    Three-colour three-step photoionization spectroscopy of uranium has been performed in a U-Ne hollow cathode discharge tube by temporally resolving three-colour photoionization optogalvanic (PIOG) signal from the normal optogalvanic (OG) signal using three tunable pulsed dye lasers. U-Ne hollow cathode discharge tube has been used as a source of uranium atomic vapours and photoionization detector. Using this technique, photoionization spectra of uranium have been investigated systematically in the energy region 52,150-52,590cm-1, through three different excitation pathways, originating from its ground state, 0cm-1(5Lo6). By analysing the three-colour photoionization spectra sixty new even-parity autoionization resonances of uranium have been identified and their probable total angular momentum (J) values have been assigned according to the J-momentum selection rule. The J-value of five autoionization resonances, which have been observed either through all three excitation pathways or through two different excitation pathways where J-value of the second excited levels differs by two, has been assigned uniquely.

  6. High-efficiency photoionization detector

    SciTech Connect

    Anderson, D.F.

    1981-05-12

    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/sup 0/C.

  7. 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.

  8. 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.

  9. 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.

  10. Vacuum Ultraviolet Laser Photoion and Pulsed Field Ionization-Photoion Study of Rydberg Series of Chlorine Atoms Prepared in the 2PJ (J = 3/2 and 1/2) Fine-structure States

    NASA Astrophysics Data System (ADS)

    Yang, Lei; Gao, Hong; Zhou, Jingang; Ng, C. Y.

    2015-09-01

    We have measured the high-resolution vacuum ultraviolet (VUV) photoion (VUV-PI) and VUV pulsed-field ionization-photoion (VUV-PFI-PI) spectra of chlorine atoms (Cl) in the VUV energy range 103,580-105,600 cm-1 (12.842-13.093 eV) using a tunable VUV laser as the photoexcitation and photoionization source. Here, Cl atoms are prepared in the Cl(2P3/2) and Cl(2P1/2) fine-structure states by 193.3 nm laser photodissociation of chlorobenzene. The employment of VUV-PFI-PI detection has allowed the identification of Rydberg transitions that are not observed in VUV-PI measurements. More than 180 new Rydberg transition lines with principal quantum number up to n = 61 have been identified and assigned to members of nine Rydberg series originating from the neutral Cl(2P3/2) and Cl(2P1/2) fine-structure states. Two of these Rydberg series are found to converge to the Cl+(3P2), four to the Cl+(3P1), and three to the Cl+(3P0) ionization limits. Based on the convergence limits determined by least-squares fits of the observed Rydberg transitions to the modified Ritz formula, we have obtained a more precise ionization energy (IE) for the formation of the ionic Cl+(3P2) from the ground Cl(2P3/2) state to be 104,591.01 ± 0.13 cm-1. This is consistent with previous IE measurements, but has a smaller uncertainty. The analysis of the quantum defects obtained for the Rydberg transitions reveals that many high-n Rydberg transitions are perturbed.

  11. 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.

  12. 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.

  13. Solid-State NMR Structure Determination from Diagonal-Compensated, Sparsely Nonuniform-Sampled 4D Proton–Proton Restraints

    PubMed Central

    2015-01-01

    We report acquisition of diagonal-compensated protein structural restraints from four-dimensional solid-state NMR spectra on extensively deuterated and 1H back-exchanged proteins. To achieve this, we use homonuclear 1H–1H correlations with diagonal suppression and nonuniform sampling (NUS). Suppression of the diagonal allows the accurate identification of cross-peaks which are otherwise obscured by the strong autocorrelation or whose intensity is biased due to partial overlap with the diagonal. The approach results in unambiguous spectral interpretation and relatively few but reliable restraints for structure calculation. In addition, the diagonal suppression produces a spectrum with low dynamic range for which ultrasparse NUS data sets can be readily reconstructed, allowing straightforward application of NUS with only 2% sampling density with the advantage of more heavily sampling time-domain regions of high signal intensity. The method is demonstrated here for two proteins, α-spectrin SH3 microcrystals and hydrophobin functional amyloids. For the case of SH3, suppression of the diagonal results in facilitated identification of unambiguous restraints and improvement of the quality of the calculated structural ensemble compared to nondiagonal-suppressed 4D spectra. For the only partly assigned hydrophobin rodlets, the structure is yet unknown. Applied to this protein of biological significance with large inhomogeneous broadening, the method allows identification of unambiguous crosspeaks that are otherwise obscured by the diagonal. PMID:24988008

  14. The study of state-selected ion-molecule reactions using the vacuum ultraviolet pulsed field ionization-photoion technique.

    PubMed

    Dressler, Rainer A; Chiu, Y; Levandier, D J; Tang, X N; Hou, Y; Chang, C; Houchins, C; Xu, H; Ng, Cheuk-Yiu

    2006-10-07

    This paper presents the methodology to generate beams of ions in single quantum states for bimolecular ion-molecule reaction dynamics studies using pulsed field ionization (PFI) of atoms or molecules in high-n Rydberg states produced by vacuum ultraviolet (VUV) synchrotron or laser photoexcitation. Employing the pseudocontinuum high-resolution VUV synchrotron radiation at the Advanced Light Source as the photoionization source, PFI photoions (PFI-PIs) in selected rovibrational states have been generated for ion-molecule reaction studies using a fast-ion gate to pass the PFI-PIs at a fixed delay with respect to the detection of the PFI photoelectrons (PFI-PEs). The fast ion gate provided by a novel interleaved comb wire gate lens is the key for achieving the optimal signal-to-noise ratio in state-selected ion-molecule collision studies using the VUV synchrotron based PFI-PE secondary ion coincidence (PFI-PESICO) method. The most recent development of the VUV laser PFI-PI scheme for state-selected ion-molecule collision studies is also described. Absolute integral cross sections for state-selected H2+ ions ranging from v+ = 0 to 17 in collisions with Ar, Ne, and He at controlled translational energies have been obtained by employing the VUV synchrotron based PFI-PESICO scheme. The comparison between PFI-PESICO cross sections for the H2+(HD+)+Ne and H2+(HD+)+He proton-transfer reactions and theoretical cross sections based on quasiclassical trajectory (QCT) calculations and three-dimensional quantum scattering calculations performed on the most recently available ab initio potential energy surfaces is highlighted. In both reaction systems, quantum scattering resonances enhance the integral cross sections significantly above QCT predictions at low translational and vibrational energies. At higher energies, the agreement between experiment and quasiclassical theory is very good. The profile and magnitude of the kinetic energy dependence of the absolute integral cross

  15. 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.

  16. The effect of vibrational motion on the dynamics of shape resonant photoionization of BF3 leading to the ? state of ?

    NASA Astrophysics Data System (ADS)

    Lucchese, Robert R.; Montuoro, Raffaele; Kotsis, Konstantinos; Tashiro, Motomichi; Ehara, Masahiro; Bozek, John D.; Das, Aloke; Landry, April; Rathbone, Jeff; Poliakoff, E. D.

    2010-04-01

    We present the results of an experimental and theoretical investigation of vibrationally resolved valence shell photoionization of BF3 leading to the ? state of ? , where vibronic coupling and shape resonances are known to be important. The experimental vibrational branching ratios for multiple quantum excitations of the symmetric stretching mode of the ion ? as well as for the single vibrational excitation of the asymmetric stretching mode ? are compared with the predictions of single-channel Schwinger variational calculations performed within the Chase adiabatic approximation to obtain vibrational-state specific cross sections. The presence of a shape resonance in the continuum of ? symmetry is seen to lead to significant non-Franck-Condon intrachannel vibronic coupling effects. The breakdown in the Franck-Condon approximation is due to the sensitivity to the asymmetric stretching mode of the energy of the resonance and the magnitude of the transition moment for exciting the resonance. However, there are indications that interchannel vibronic coupling effects may also be significant in this system.

  17. Effect of electron correlation and shape resonance on photoionization from the S1 and S2 states of pyrazine.

    PubMed

    Suzuki, Yoshi-Ichi; Suzuki, Toshinori

    2012-11-21

    In a previous study [T. Horio, T. Fuji, Y.-I. Suzuki, and T. Suzuki, J. Am. Chem. Soc. 131, 10392 (2009)], we demonstrated that the time-energy map of photoelectron angular anisotropy enables unambiguous identification of ultrafast S(2)(ππ*)-S(1)(nπ*) internal conversion in pyrazine. A notable characteristic of this map is that the forbidden ionization process of D(0)(n(-1)) ← S(2)(ππ*) gives a negative photoelectron anisotropy parameter. In the present study, we elucidate the mechanism of this process by calculating the photoionization transition dipole moments and photoelectron angular distribution using the first-order configuration interaction method and the continuum multiple scattering Xα approximation; these calculations at the S(0) equilibrium geometry reproduce the observed anisotropy parameters for D(0) ← S(2) and D(0) ← S(1) ionizations, respectively. On the other hand, they do not reproduce the small difference in the photoelectron anisotropy parameters for the D(1)(π(-1)) ← S(2) and D(0) ← S(1) ionizations, both of which correspond to removal of an electron from the same π* orbital in the excited states. We show that these ionizations are affected by the ka(g) shape resonance and that the difference between their photoelectron anisotropy parameters originates from the difference in the molecular geometry in D(1) ← S(2) and D(0) ← S(1).

  18. Role of excited state photoionization in the 852.1 nm Cs laser pumped by Cs-Ar photoassociation

    SciTech Connect

    Hewitt, J. D.; Houlahan, T. J. Jr.; Eden, J. G.; Gallagher, J. E.; Perram, G. P.; Carroll, D. L.; Palla, A. D.; Verdeyen, J. T.

    2013-03-18

    Photoionization of Cs (6p {sup 2}P{sub 3/2}) atoms during the operation of a Cs D{sub 2} line (852.1 nm: 6p {sup 2}P{sub 3/2}{yields}6s {sup 2}S{sub 1/2}) laser, pumped by free{yields}free transitions of thermal Cs-Ar ground state pairs, has been investigated experimentally and computationally. Photoexcitation of Cs vapor/Ar mixtures through the blue satellite of the D{sub 2} transition (peaking at 836.7 nm) selectively populates the {sup 2}P{sub 3/2} upper laser level by the dissociation of the CsAr excited complex. Comparison of laser output energy data, for instantaneous pump powers up to 3 MW, with the predictions of a numerical model sets an upper bound of 8 Multiplication-Sign 10{sup -26} cm{sup 4} W{sup -1} on the Cs (6p {sup 2}P{sub 3/2}) two photon ionization cross-section at 836.7 nm which corresponds to a single photon cross-section of 2.4 Multiplication-Sign 10{sup -19} cm{sup 2} for a peak pump intensity of 3 MW cm{sup -2}.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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(3Π1) ← TiC(X3Σ+) and TiC(3Σ+) ← TiC(X3Σ+) transition bands. This assignment supports that the electronic configuration and term symmetry for the neutral TiC ground state are …7σ28σ19σ13π4 (X3Σ+). The rotational constant and the corresponding bond distance of TiC(X3Σ+; 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 …7σ28σ13π4 (X2Σ+) with the v+ = 0 → 1 vibrational spacing of 870.0(8) cm-1 and the rotational constants of Be+ = 0.6322(28) cm-1, and αe+ = 0.0085(28) cm-1. The latter rotational constants yield the equilibrium bond distance of re+ = 1.667(4) Å for TiC+(X2Σ+). 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+(X2Σ+) and that of TiC(X3Σ+) 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+(X2Σ+; v+ = 0 and 1, N+) ← TiC(3Π1; v', J'), reveals a strong decreasing trend for the photoionization cross section as |ΔN+| = |N+ - J'| is increased. The maximum |ΔN+| change of 7 observed here is also consistent with the previous

  1. 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

  2. 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.

  3. 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.

  4. The Study of State-Selected Ion-Molecule Reactions using the Vacuum Ultraviolet Pulsed Field Ionization-Photoion Technique

    DTIC Science & Technology

    2006-01-01

    reactant ion preparation is the photoelectron-photoion coin- spheric, industrial, and aerospace plasmas .17-21 It is known cidence technique, which...Phys. 34, 43 (1999). 55 K. Norwood and C. Y. Ng. Chem. Phys. Lett. 156, 145 (1989). 16R. A. Dressier and A. A. Viggiano , in The Encyclopedia of Mass

  5. 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.

  6. Vibrationally resolved photoionization dynamics of CF4 in the D 2A1 state

    NASA Astrophysics Data System (ADS)

    Das, Aloke; Scott Miller, J.; Poliakoff, E. D.; Lucchese, R. R.; Bozek, John D.

    2007-07-01

    Vibrationally resolved photoelectron spectroscopy of the CF4+ (DA12) state is studied for the first time over an extended energy range, 26.5⩽hν ⩽50eV. It is found that the energy dependence of the totally symmetric stretching vibration is qualitatively different from all of the other vibrational modes. Moreover, the vibrational branching ratio curves for all of the symmetry forbidden vibrations are nearly identical. Qualitative arguments are used to show that it is likely that at least two shape resonances are present in the continuum, and that their characteristics, such as energy dependence and spatial localization, are distinctly different.

  7. Dissociation of vibrational state-selected O2(+) Ions in the B(2)Σ(g)¯ state using threshold photoelectron-photoion coincidence velocity imaging.

    PubMed

    Tang, Xiaofeng; Zhou, Xiaoguo; Niu, Mingli; Liu, Shilin; Sheng, Liusi

    2011-06-23

    Using the recently developed threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging mass spectrometer (Tang et al. Rev. Sci. Instrum.2009, 80, 113101), dissociation of vibrational state-selected O(2)(+)(B(2)Σ(g)(¯), v(+) = 0-6) ions was investigated. Both the speed and angular distributions of the O(+) fragments dissociated from individually vibronic levels of the B(2)Σ(g)(¯) state were obtained directly from the three-dimensional time-sliced TPEPICO velocity images. Two dissociation channels, O(+)((4)S) + O((3)P) and O(+)((4)S) + O((1)D), were respectively observed, and their branching ratios were found to be heavily dependent on the vibrational states. A new intersection mechanism was suggested for the predissociation of O(2)(+)(B(2)Σ(g)(¯)) ions, especially for dissociation at the energy of the v(+) = 4 level. In addition, the anisotropic parameters for O(+) fragments from different dissociative pathways were determined to be close to zero, indicating that the v(+) = 0-6 levels of B(2)Σ(g)(¯) predissociate on a time scale that is much slower than that of molecular rotation.

  8. 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.

  9. 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.

  10. Polarization analysis of fluorescence probing the alignment of Xe+ ions in the resonant Auger decay of the Xe* 4d-15/26p photoexcited state

    NASA Astrophysics Data System (ADS)

    Meyer, M.; Marquette, A.; Grum-Grzhimailo, A. N.; Kleiman, U.; Lohmann, B.

    2001-08-01

    Xe II fluorescence, following the resonant Auger decay of the Xe* 4d-15/26p photoexcited state, has been measured in the wavelength region 400 nm <=λ (fluo) <=610 nm by means of dispersed fluorescence spectroscopy, and the degree of linear polarization of the emitted light has been analyzed. From these data, the alignment of the ionic 5p46p states produced by the Auger decay has been determined by taking into account the depolarization of the radiatively decaying Xe II multiplet due to cascade population and hyperfine interactions. Calculations of the alignment are performed in a multiconfigurational Dirac-Fock approach and compared with the experiment. Good agreement between experiment and theory has been obtained for almost all fine-structure components of the Xe II 5p46p multiplet, providing reliable alignment parameters of the ionic states produced upon resonant Auger decay.

  11. Photoionization of molecular clusters

    NASA Astrophysics Data System (ADS)

    Andres, R. P.; Calo, J. M.

    1981-12-01

    An experimental apparatus consisting of a novel multiple expansion cluster source coupled with a molecular beam system and photoionization mass spectrometer has been designed and constructed. This apparatus has been thoroughly tested and preliminary measurements of the growth kinetics of water clusters and the photoionization cross section of the water dimer have been carried out.

  12. 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

  13. 4-D photoacoustic tomography.

    PubMed

    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.

  14. 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.

  15. K-shell photoionization of ground-state Li-like carbon ions [C3+]: experiment, theory and comparison with time-reversed photorecombination

    NASA Astrophysics Data System (ADS)

    Müller, A.; Schippers, S.; Phaneuf, R. A.; Scully, S. W. J.; Aguilar, A.; Covington, A. M.; Álvarez, I.; Cisneros, C.; Emmons, E. D.; Gharaibeh, M. F.; Hinojosa, G.; Schlachter, A. S.; McLaughlin, B. M.

    2009-12-01

    Absolute cross sections for the K-shell photoionization of ground-state Li-like carbon [C3+(1s22s 2S)] ions were measured by employing the ion-photon merged-beams technique at the Advanced Light Source. The energy ranges 299.8-300.15 eV, 303.29-303.58 eV and 335.61-337.57 eV of the [1s(2s2p)3P]2P, [1s(2s2p)1P]2P and [(1s2s)3S 3p]2P resonances, respectively, were investigated using resolving powers of up to 6000. The autoionization linewidth of the [1s(2s2p)1P]2P resonance was measured to be 27 ± 5 meV and compares favourably with a theoretical result of 26 meV obtained from the intermediate coupling R-matrix method. The present photoionization cross section results are compared with the outcome from photorecombination measurements by employing the principle of detailed balance.

  16. Experimental generation of 8.4 dB entangled state with an optical cavity involving a wedged type-II nonlinear crystal.

    PubMed

    Zhou, Yaoyao; Jia, Xiaojun; Li, Fang; Xie, Changde; Peng, Kunchi

    2015-02-23

    Entangled state of light is one of the essential quantum resources in quantum information science and technology. Especially, when the fundamental principle experiments have been achieved in labs and the applications of continuous variable quantum information in the real world are considered, it is crucial to design and construct the generation devices of entangled states with high entanglement and compact configuration. We have designed and built an efficient and compact light source of entangled state, which is a non-degenerate optical parametric amplifier (NOPA) with the triple resonance of the pump and two subharmonic modes. A wedged type-II KTP crystal inside the NOPA is used for implementing frequency-down-conversion of the pump field to generate the optical entangled state and achieving the dispersion compensation between the pump and the subharmonic waves. The EPR entangled state of light with quantum correlations of 8.4 dB for both amplitude and phase quadratures are experimentally produced by a single NOPA under the pump power of 75 mW.

  17. Photoionization of Ar VIII

    NASA Astrophysics Data System (ADS)

    Liang, Liang; Jiang, Wen-xian; Zhou, Chao

    2017-01-01

    The photoionization cross section, energy levels and widths of 22 Rydberg series (in the autoionization region) for Na-like Ar VIII were investigated by using of R-matrix method. The relativistic distorted-wave method is used to calculate the radial functions, and QB method of Quigly-Berrington [Quigley et al. 1998] is employed to calculate the resonance levels and widths. We have identified the formant in the figure of the photoionization cross section.

  18. 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

  19. 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.

  20. 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.

  1. The 4D nucleome project.

    PubMed

    Dekker, Job; Belmont, Andrew S; Guttman, Mitchell; Leshyk, Victor O; Lis, John T; Lomvardas, Stavros; Mirny, Leonid A; O'Shea, Clodagh C; Park, Peter J; Ren, Bing; Politz, Joan C Ritland; Shendure, Jay; Zhong, Sheng

    2017-09-13

    The 4D Nucleome Network aims to develop and apply approaches to map the structure and dynamics of the human and mouse genomes in space and time with the goal of gaining deeper mechanistic insights into how the nucleus is organized and functions. The project will develop and benchmark experimental and computational approaches for measuring genome conformation and nuclear organization, and investigate how these contribute to gene regulation and other genome functions. Validated experimental technologies will be combined with biophysical approaches to generate quantitative models of spatial genome organization in different biological states, both in cell populations and in single cells.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Photoionization studies of oxygen and hydrogen

    NASA Astrophysics Data System (ADS)

    Padmanabhan, Arathi

    A toroidal spectrometer designed to perform (gamma, 2e) studies, was for the first time employed for Threshold Photoelectron Photoion Coincidence (TPEPICO) study. The angular distributions of O+(4S) ions produced from dissociative photoionization (DPI) of O2 + c4Sigma-u(nu =0,1) using the TPEPICO technique, i.e. by measuring the coincidence yield between threshold photoelectrons and photoions have been investigated. The results for lifetimes, taunu, corresponding to the vibrational levels nu = 0,1, along with the value obtained for inherent anisotropic photoion angular distribution betaO+, are presented. Recently, Fernandez and Martin (New J Phys 11 34 (2009)), have performed an extensive ab initio study of DPI in H2, in which large oscillatory behaviour in the electron angular distribution, as a function of electron energy, has been predicted. The result of their ab anitio calculations reveal that the electron angular, theta, distributions oscillate between a cos2theta pattern and isotropic with less than a 1 eV.change in electron energy. Due to the very low cross section and the requirement for high energy resolution in the electron detection system, these measurements require sensitive instrumentation that is now available at the Canadian Light Source. For this particular H 2 study, the electron angular distributions as a function of electron energy are the signature of quantum mechanical interference between, essentially, two specific doubly excited states (namely, 1Q11Sigma u+ and 1Q21piu) decaying at different internuclear distances. While interference between 'direct' photoionization and autoionization is well-known, the first unambiguous observation of interference between two autoionization processes, occurring on the femtosecond timescale is presented. A simple semi-classical model captures the essence of both our experimental observations and the results of full ab initio calculations. It does this through explicitly linking the electron angular

  8. Photoionization of the Buckminsterfullerene Cation.

    PubMed

    Douix, Suzie; Duflot, Denis; Cubaynes, Denis; Bizau, Jean-Marc; Giuliani, Alexandre

    2017-01-05

    Photoionization of a buckminsterfullerene ion is investigated using an ion trap and a merged beam setup coupled to synchrotron radiation beamlines and compared to theoretical calculations. Absolute measurements derived from the ion trap experiment allow discrepancies concerning the photoionization cross section of C60(+) to be solved.

  9. Double Photoionization of Atomic Beryllium

    NASA Astrophysics Data System (ADS)

    Yip, Frank L.; McCurdy, C. William; Rescigno, Thomas N.

    2010-03-01

    One-photon double ionization (DPI) of beryllium represents the next step in the evolution of DPI investigations that began with helium in order to sensitively probe electron correlation. Beryllium is the simplest atomic species of the alkaline earth elements which, in general, possess two electrons outside of a fully occupied inner shell that spherically screens the nucleus. This provides a natural basis for comparison to 1s^2 helium DPI. However, the valence state of beryllium has n=2, thus making the valence excited target 2s2p more accessible relative to the 2s^2 ground state as compared to ground-state and metastable helium. Also, the symmetry of photoionizing from either the ^1S or ^1P initial state will have consequences for the angular distributions for double ionization. Triply differential cross sections (TDCS) are presented for DPI from both ground state 2s^2 and excited state 2s2p beryllium calculated using exterior complex scaling (ECS) for the valence electrons.

  10. Time-dependent Cooling in Photoionized Plasma

    NASA Astrophysics Data System (ADS)

    Gnat, Orly

    2017-02-01

    I explore the thermal evolution and ionization states in gas cooling from an initially hot state in the presence of external photoionizing radiation. I compute the equilibrium and nonequilibrium cooling efficiencies, heating rates, and ion fractions for low-density gas cooling while exposed to the ionizing metagalactic background radiation at various redshifts (z = 0 ‑ 3), for a range of temperatures (108–104 K), densities (10‑7–103 cm‑3), and metallicities (10‑3–2 times solar). The results indicate the existence of a threshold ionization parameter, above which the cooling efficiencies are very close to those in photoionization equilibrium (so that departures from equilibrium may be neglected), and below which the cooling efficiencies resemble those in collisional time-dependent gas cooling with no external radiation (and are thus independent of density).

  11. Photoionization cross sections, electron-impact inverse mean free paths, and stopping powers for each subshell of silvera)

    NASA Astrophysics Data System (ADS)

    Lin, D. L.; Strickland, D. J.

    1980-03-01

    Using the Herman-Skillman potentials and bound wave functions for each subshell of silver, we have computed the continuum wave functions, and subshell-by-subshell photoionization cross sections with photoelectron energies up to 10 keV. Applying a relationship between photoionization and electron impact ionization, we have obtained inverse mean free paths and stopping powers, again by subshell, for electrons penetrating through silver. The maximum electron energy considered is 100 keV. For the total photoionization cross section, comparison of our work with experiment shows excellent agreement for photon energies down to 100 eV, below which solid-state effects should be included. Theoretical total inverse mean free paths, being strongly dominated by contributions from 4d electrons, are in good agreement with data around 1 keV, but about a factor of 2 larger at energies below 100eV. Our stopping power is in good agreement with other theoretical work above 400 eV and approaches the relativistic Bethe formula above 10 keV. Range is also computed and is in good agreement with other theoretical work.

  12. 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.

  13. Photoionization of P+: Experiment and theory

    NASA Astrophysics Data System (ADS)

    Nahar, S. N.; Hernández, E. M.; Hernández, L.; Antillón, A.; Morales-Mori, A.; González, O.; Covington, A. M.; Chartkunchand, K. C.; Hanstorp, D.; Juárez, A. M.; Hinojosa, G.

    2017-01-01

    An experimental and theoretical study of the single photoionization cross section of the P+ cation of phosphorus is presented. Photoionization (PI) cross sections are instrumental for the determination of abundances in the interstellar medium. The experiment was performed by merging an ion beam with a photon beam. The photon beam was nearly monochromatic and had an energy resolution of 24 meV. Calculations were carried out using the Breit-Pauli R-matrix method. The combined study was developed in the photon energy interval from 18 eV (68.9 nm) to 50 eV (24.8 nm). Comparison between the measured and the calculated cross section shows good agreement in general and identifies features of the process and existence of states in the experimental beam. The present results should provide for more accurate modeling of P+.

  14. Photoionization of sodium clusters

    SciTech Connect

    Peterson, K.I.; Dao, P.D.; Farley, R.W.; Castleman, A.W. Jr.

    1984-03-01

    Sodium clusters, Na/sub x/ (2< or =x< or =8), were produced in a supersonic jet by coexpansion with argon and subjected to analysis via photoionization coupled with mass spectrometry. The present measurements, made at somewhat higher resolution than earlier literature studies, yield ionization potentials in excellent agreement for x = 1 to 4 and x = 7, and reveal heretofore unreported structure in the post-threshold spectra. The present measurements enable a more definitive assignment of the ionization potentials, giving a lower value for x = 6 and pointing to lower ones for x = 5 and 8. The frequently discussed odd--even alternation in ionization potentials is no longer evident beyond the pentamer. Values for the binding energies of Na to Na/sup +//sub x/ (3< or =x< or =8) are deduced.

  15. 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

  16. 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.

  17. Spectra of resonance surface photoionization

    SciTech Connect

    Antsiferov, V.V.; Smirnov, G.I.; Telegin, G.G.

    1995-09-01

    The theory of nonactivated electron transfer between atoms interacting reasonantly with coherent radiation and a metal surface is developed. The spectral resonances in photoabsorption and surface photoionization are found to be related to nonlinear interference effects in the interaction between discrete atomic levels and the continuum formed by the quasi-continuous electron spectrum of a normal metal. The asymmetry in the resonance surface photoionization spectrum is shown to have a shape typical of the Fano autoionization resonances. 18 refs.

  18. Neon photoionized plasma experiment at Z

    NASA Astrophysics Data System (ADS)

    Mayes, D. C.; Mancini, R. C.; Bailey, J. E.; Loisel, G. P.; Rochau, G. A.

    2016-10-01

    We discuss an experimental effort to study the atomic kinetics in neon photoionized plasmas via K-shell line absorption spectroscopy. The experiment employs the intense x-ray flux emitted at the collapse of a Z-pinch to heat and backlight a photoionized plasma contained within a cm-scale gas cell placed at various distances from the Z-pinch and filled with neon gas pressures in the range from 3.5 to 30 torr. The experimental platform affords an order of magnitude range in the ionization parameter characterizing the photoionized plasma from about 3 to 80 erg*cm/s. An x-ray crystal spectrometer capable of collecting both time-integrated and time-gated spectra is used to collect absorption spectra. A suite of IDL programs has been developed to process the experimental data to produce transmission spectra. The spectra show line absorption by several ionization stages of neon, including Be-, Li-, He-, and H-like ions. Analysis of these spectra yields ion areal-densities and charge state distributions, which can be compared with results from atomic kinetics codes. In addition, the electron temperature is extracted from level population ratios of nearby energy levels in Li- and Be-like ions, which can be used to test heating models of photoionized plasmas. This work was sponsored in part by the DOE National Nuclear Security Administration Grant DE-FG52-09NA29551, DOE Office of Science Grant DE-SC0014451, and the Z Facility Fundamental Science Program of SNL.

  19. Dynamics of photoionization of hydrogenlike ions in Debye plasmas

    SciTech Connect

    Qi, Y. Y.; Wang, J. G.; Janev, R. K.

    2009-12-15

    Photoionization processes for the ground state and n<=3 excited states of hydrogenlike ions embedded in a weakly coupled plasma are investigated in the entire energy range of a nonrelativistic regime. The plasma screening of the Coulomb interaction between charged particles is described by the Debye-Hueckel model. The energy levels and wave functions for both the bound and continuum states are calculated by solving the Schroedinger equation numerically by the symplectic integrator. The screening of Coulomb interactions reduces the number of bound electron states, decreases their binding energies, broadens the radial distribution of electron wave functions of these states, and changes significantly the phases and the amplitudes of continuum wave functions. These changes strongly affect the dipole matrix elements between the bound and continuum states and, hence, the photoionization cross sections. The most significant effects of the screened Coulomb interactions on the energy behavior of photoionization cross sections are manifested in its low-energy behavior (Wigner threshold law), the appearance of multiple shape and virtual-state resonances when the energy levels of upper bound states enter the continuum after certain critical strength of the screening, and in the (slight) reduction of the cross section at high photon energies. All these features of the photoionization cross section are related to the short-range character of the Debye-Hueckel potential. The effects of the potential screening on the Combet-Farnoux and Cooper minima in the photoionization cross section are also investigated. Comparison of calculated photoionization cross sections with the results of other authors, when available, is made.

  20. Self-gated 4D multiphase, steady-state imaging with contrast enhancement (MUSIC) using rotating cartesian K-space (ROCK): Validation in children with congenital heart disease.

    PubMed

    Han, Fei; Zhou, Ziwu; Han, Eric; Gao, Yu; Nguyen, Kim-Lien; Finn, J Paul; Hu, Peng

    2017-08-01

    To develop and validate a cardiac-respiratory self-gating strategy for the recently proposed multiphase steady-state imaging with contrast enhancement (MUSIC) technique. The proposed SG strategy uses the ROtating Cartesian K-space (ROCK) sampling, which allows for retrospective k-space binning based on motion surrogates derived from k-space center line. The k-space bins are reconstructed using a compressed sensing algorithm. Ten pediatric patients underwent cardiac MRI for clinical reasons. The original MUSIC and 2D-CINE images were acquired as a part of the clinical protocol, followed by the ROCK-MUSIC acquisition, all under steady-state intravascular distribution of ferumoxytol. Subjective scores and image sharpness were used to compare the images of ROCK-MUSIC and original MUSIC. All scans were completed successfully without complications. The ROCK-MUSIC acquisition took 5 ± 1 min, compared to 8 ± 2 min for the original MUSIC. Image scores of ROCK-MUSIC were significantly better than original MUSIC at the ventricular outflow tracts (3.9 ± 0.3 vs. 3.3 ± 0.6, P < 0.05). There was a strong trend toward superior image scores for ROCK-MUSIC in the other anatomic locations. ROCK-MUSIC provided images of equal or superior image quality compared to original MUSIC, and this was achievable with 40% savings in scan time and without the need for physiologic signal. Magn Reson Med 78:472-483, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  1. Double K-shell photoionization and universal scaling laws

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

    The photon energy dependence of the double K-shell ionization cross sections for light atoms and He-like ions is reported. The K-shell double photoionization DPI cross-sections for hollow atom production are compared to those of the corresponding He-like counterparts. The relative contribution of the initial-state correlations and final-state electron-electron interactions to the K-shell DPI is addressed. A semiempirical universal scaling of the double photoionization cross sections with the effective nuclear charge for neutral atoms in the range 2 <= Z <= 47 is established.

  2. Helium 23S photoionization up to the N = 5 threshold

    NASA Astrophysics Data System (ADS)

    Argenti, Luca; Moccia, Roberto

    2008-02-01

    We present the results of an accurate B-spline K-matrix calculation of total and partial cross sections and asymmetry parameters for the photoionization of the metastable 23Se state of helium up to the N = 5 threshold. The effect of the [040]+5 intruder state below N = 4 is shown.

  3. Absolute measurements of chlorine Cl+ cation single photoionization cross section

    NASA Astrophysics Data System (ADS)

    Hernández, E. M.; Juárez, A. M.; Kilcoyne, A. L. D.; Aguilar, A.; Hernández, L.; Antillón, A.; Macaluso, D.; Morales-Mori, A.; González-Magaña, O.; Hanstorp, D.; Covington, A. M.; Davis, V.; Calabrese, D.; Hinojosa, G.

    2015-01-01

    The photoionization of Cl+ leading to Cl2+ was measured in the photon energy range of 19.5-28.0 eV. A spectrum with a photon energy resolution of 15 meV normalized to absolute cross-section measurements is presented. The measurements were carried out by merging a Cl+ ion beam with a photon beam of highly monochromatic synchrotron radiation at the Advanced Light Source at Lawrence Berkeley National Laboratory. The measured photoionization of Cl+ consists of several autoionization resonances surperimposed on the direct photoionization signal. Most of the prominent resonances are assigned to members of Rydberg series originating from the singlet ground state and from metastable triplet levels within the ground-state configuration of Cl+. The direct ionization cross section is no larger than 12 Mb.

  4. 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.

  5. 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.

  6. 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.

  7. Photoionization of zinc by TDLDA calculations

    NASA Astrophysics Data System (ADS)

    Stener, M.; Decleva, P.

    1997-10-01

    Absolute photoionization cross section profiles of Zn have been calculated at TDLDA and LDA level, employing a very accurate B-spline basis set and the modified Sternheimer approach. The van Leeuwen - Baerends exchange correlation potential has been used, since its correct asymptotic behaviour is able to support virtual states and describe core-excited resonances. A comparison with available theoretical and experimental data has been performed when possible. The present method has been proven to be robust to analyse wide photon energy regions (from threshold up to 200 eV) and discuss the various shapes of one-electron resonances.

  8. 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.

  9. 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

  10. Photoionization of hydrogen-like ions in dense quantum plasmas

    NASA Astrophysics Data System (ADS)

    Qi, Y. Y.; Wang, J. G.; Janev, R. K.

    2017-06-01

    The photoionization of hydrogen-like ions in n ≤ 3 bound states, embedded in cold, dense quantum plasmas, is investigated in detail. The electron energies and wave functions for the bound and continuum states are determined by numerically solving the scaled Schrödinger equation by the fourth-order symplectic integration scheme. The monotonic behavior of the photoionization cross section for a pure Coulomb potential is dramatically changed due to the plasma screening effects described by the cosine-Debye-Hückel potential. In the region of low photoelectron energies, the photoionization cross section, besides the usual Wigner-law threshold behavior, exhibits a rich structure of shape and virtual-state resonances when the plasma screening parameter takes values around the critical screening parameter for which a bound state enters the continuum. It is observed that a shape resonance is followed by a Cooper minimum in the photoionization cross section when the principal quantum number of continuum quasi-bound state is equal to the one of the initial bound states.

  11. Photoionization of Ca XV with high energy features

    NASA Astrophysics Data System (ADS)

    Nahar, Sultana N.

    2017-02-01

    Photoionization cross sections of (Ca XV + hν → Ca XVI + e), with high energy resonant photo-absorption phenomena, of a large number of bound states, 701 in total with n ≤ 10 and l ≤ 9, are reported. They are obtained using the R-matrix method with a close coupling (CC) wavefunction expansion of 29 states of n = 2,3 complexes of the core ion Ca XVI. Characteristic features found in photoionization of the ion are illustrated with examples. The cross section (σPI) of the ground 2s22p2(3P) state is found to be unaffected by the size of the wavefunction expansion except for weak sparse resonances in high energy region. However, effects on excited states are considerable as the core excitations to n = 3 states are manifested in huge resonant absorption in high energy photoionization. They show existence of prominent high peak resonant features and enhancement in the background that were not studied before for Ca XV. In addition photoionization of the excited states with a single valence electron is dominated by Seaton resonant structures formed by the photo-excitation-of-core in the high energy region. These features will impact other quantities, such as the opacity, electron-ion recombination in high temperature plasmas where the ion exists, and hence will play important role in determination of elemental abundances in the astronomical objects.

  12. 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

  13. Relativistic theory of the double photoionization of heliumlike atoms

    SciTech Connect

    Yerokhin, Vladimir A.; Surzhykov, Andrey

    2011-09-15

    A fully relativistic calculation of the double photoionization of heliumlike atoms is presented. The approach is based on the partial-wave representation of the Dirac continuum states and accounts for the retardation in the electron-electron interaction as well as the higher-order multipoles of the absorbed photon. The electron-electron interaction is taken into account to the leading order of the perturbation theory. The relativistic effects are shown to become prominent already for the medium-Z ions, changing the shape and the asymptotic behavior of the photon energy dependence of the ratio of the double-to-single photoionization cross section.

  14. E4D_RT

    SciTech Connect

    2016-03-22

    Time-lapse ERT imaging for monitoring both natural and engineered subsurface processes has advanced rapidly over the past 15-20 years. However, imaging results generally required a significant amount of manual and computational effort, and therefore were not available while the process was occurring. Although the value of real-time imaging was recognized, several obstacles prevented it's implementation. E4D_RT addresses these obstacles by 1) providing specialized algorithms that negate the need for user intervention, thereby automating the time-lapse data processing steps, 2) linking field data collection systems with parallel supercomputing systems via wireless data transfer link, and 3) addressing the computational burdens by utilizing distributed memory supercomputing resources, thereby enabling rapid data processing and imaging results.

  15. 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)

  16. 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)

  17. Jet-cooled fluorescence excitation spectra and carbonyl wagging and ring-puckering potential energy functions of cyclobutanone and its 2,2,4,4-d4 isotopomer in the S1(n,π*) electronic excited state

    NASA Astrophysics Data System (ADS)

    Zhang, Jian; Chiang, Whe-Yi; Laane, Jaan

    1994-03-01

    The jet-cooled fluorescence excitation spectra of cyclobutanone and its 2,2,4,4-d4 isotopomer have been recorded in the 305-335 nm region. The electronic band origin of the d0 molecule for the S1(n,π*) state of A2 symmetry occurs at 30 292 cm-1 (30 265 cm-1 for the d4 molecule). The observed spectra consisting of more than 50 bands for each isotopomer involve ν7, ν8, and ν9 (the three A1 ring vibrations) as well as ν20(C=O in-plane wag), ν26 (C=O out-of-plane wag), and ν27 (ring puckering). Five bands associated with the excited vibrational states of ν26 in the S1(n,π*) electronic state were observed for each isotopic species, and these were used to determine the one-dimensional potential energy functions for the C=O out-of-plane wagging. The C=O wagging angle was determined to be 39° and the barrier to inversion is 2149 cm-1 (2188 cm-1 for the deuteride). For the ring-puckering in the S1 state the lowest three vibrational energy spacings were found to be 106, 166, and 185 cm-1 as compared to values of 35, 57, and 65 cm-1 in the S0 ground state. Several ring-puckering potential energy functions with varying degrees of asymmetry are capable of reproducing the observed results. In all cases, however, the v=0 puckering state lies above any barrier to planarity. A two-dimensional potential function which fits the observed data was also determined in terms of the wagging and puckering coordinates.

  18. Structural and functional state of heart left ventricle depending on polymorphism rs966221 phosphodiesterase 4D gene in emergency workers of the Chornobyl NPP suffering from coronary heart disease.

    PubMed

    Nastina, O; Pleskach, G; Kursina, N; Bazyka, O; Makarevich, O; Abramenko, I; Chumak, A; Belyi, D

    2016-12-01

    This study consisted in examination the features of structural and functional state of the cardiovascular system in emergency workers (EW) of the Chernobyl nuclear power plant (ChNPP) who suffered from coronary heart disease (CHD) and having different genotypes due to polymorphism rs966221 phosphodiesterase 4D (PDE4D) gene. The study involved 121 EW and 63 non irradiated patients with CHD. Standardized survey included echo doppler cardiography (EchoCG) that was done by Diagnostic Ultrasound System DS N3 (Mindray). Polymorphism rs966221 PDE4D determined by polymerase chain reaction followed by restriction reaction products. The distribution of genotypes PDE4D in EW was as follows: CC - 42, CT - 49 and TT - 30 patients. In the con trol group, carriers of the same genotypes were 27, 21 and 15 persons respectively. All echocardiographic parame ters in EW workers and non irradiated patients did not differ significantly. Amongst TT genotype carriers of both groups the proportion of patients with increased myocardial mass index was the highest (82.9%) compared to CC genotype (78.4%) and CT (71.4%). The concentric type of left ventricular (LV) hypertrophy was found in 54.9% of patients with CC genotype, in 51.8% with CT genotype and 45.7% with TT genotype, while the eccentric type in 23.5, 21.4 and 37.1% respectively. The relative number of people with high LV end diastolic volume (EDV) normalized by body surface area (BSA) was 27.5% in CC genotype carriers, 26.8% in CT genotype and 40% in TT genotype carriers (p > 0.05). The increase of BSA indexed LV end systolic volume (ESV) was found in 27.5, 30.4 and 28.6%, and the ejection fraction in 15.7, 23.2 and 22.9% respectively. The largest number of CHD patients with inadequate dias tolic function was in carriers of TT genotype (75%) compared with the data in CC (66.7%) and CT genotypes (42.9%) carriers. In patients with the same genotype, both EW and non irradiated persons there were virtually no dif ferences in indicators

  19. Photoionization of oxidized metal clusters

    SciTech Connect

    Dao, P.D.; Peterson, K.I.; Castleman, A.W. Jr.

    1984-01-01

    Oxidized metal clusters (Na/sub x/O and K/sub x/O for 2< or =x< or =4) were formed in a gas phase reaction between metal clusters and an oxidizing gas using a double expansion technique. Their appearance potentials were measured using a molecular beam-photoionization mass spectrometer system. These first photoionization data for oxidized clusters provide information on trends of ionization potentials as a function of the degree of aggregation. The ionization potentials do not differ greatly from the analogous metallic species, but in the case of the sodium tetramer the value does fall below that of the bare metal cluster. This finding is in accord with what has been observed as an influence of impurities on the work function of the bulk sodium. The results are also of interest concerning questions of octet rule violations and hypervalency.

  20. Measurement of the partial photoionization cross sections and asymmetry parameters of S atoms in the photon energy range 10.0-30.0 eV using constant-ionic-state spectroscopy

    SciTech Connect

    Innocenti, Fabrizio; Zuin, Lucia; Costa, Maria L.; Dias, Antonio A.; Morris, Alan; Stranges, Stefano; Dyke, John M.

    2007-04-21

    The partial photoionization cross sections and asymmetry parameters of S atoms have been measured using constant-ionic-state (CIS) spectroscopy in the photon energy range 10.0-30.0 eV. The ionizations investigated in these CIS experiments are the (3p){sup -1} ionizations S{sup +}({sup 4}S)(leftarrow)S({sup 3}P), S{sup +}({sup 2}D)(leftarrow)S({sup 3}P), and S{sup +}({sup 2}P)(leftarrow)S({sup 3}P). For the first time Rydberg series which converge to the fourth ionization limit have been observed and assignments of these series have been proposed. These correspond to excitations to Rydberg states that are parts of series which converge to the fourth ionization limit, S{sup +}({sup 4}P)(leftarrow)S({sup 3}P) (3s){sup -1}, and autoionize to the lower S{sup +}({sup 4}S), S{sup +}({sup 2}D), or S{sup +}({sup 2}P) states. For each series observed in the CIS spectra photoelectron angular distribution studies, combined with other evidence, has allowed the angular momentum character of the free electron on autoionization to be determined.

  1. Investigation of fragmentation processes following core photoionization of organometallic molecules in the vapor phase

    NASA Astrophysics Data System (ADS)

    Nagaoka, Shin-ichi; Suzuki, Shinzo; Koyano, Inosuke

    1988-04-01

    Ionic fragmentation processes following ( n - 1)d core level photoionization of organometallic molecules have been studied in the vapor phase using synchrotron radiation. Results on tetramethyllead, tetramethyltin and tetramethylgermanium are reported. The threshold electron spectra and the photoionization efficiency curves of these molecules are presented and discussed. It is concluded that the ( n - 1)d 9 core-hole state of M(CH 3) 4 (M  Pb, Sn or Ge) is split into five sublevels owing to both the spin-orbi and the electrostatic perturbations by the methyl groups, and that the M + ions are predominantly produced following ( n - 1)d photoionization.

  2. Decoherence in Attosecond Photoionization

    SciTech Connect

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

    2011-02-04

    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.

  3. Decoherence in attosecond photoionization.

    PubMed

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

    2011-02-04

    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.

  4. Atomic kinetics of a neon photoionized plasma experiment at Z

    NASA Astrophysics Data System (ADS)

    Mayes, Daniel C.; Mancini, Roberto; E Bailey, James; Loisel, Guillaume; Rochau, Gregory

    2017-06-01

    We discuss an experimental effort to study the atomic kinetics in neon photoionized plasmas via K-shell line absorption spectroscopy. The experiment employs the intense x-ray flux emitted at the collapse of a Z-pinch to heat and backlight a photoionized plasma contained within a cm-scale gas cell placed at various distances from the Z-pinch and filled with neon gas pressures in the range from 3.5 to 30 torr. The experimental platform affords an order of magnitude range in the ionization parameter characterizing the photoionized plasma from about 3 to 80 erg*cm/s. Thus, the experiment allows for the study of trends in ionization distribution as a function of the ionization parameter. An x-ray crystal spectrometer capable of collecting both time-integrated and time-gated spectra is used to collect absorption spectra. A suite of IDL programs has been developed to process the experimental data to produce transmission spectra. The spectra show line absorption by several ionization stages of neon, including Be-, Li-, He-, and H-like ions. Analysis of these spectra yields ion areal-densities and charge state distributions, which can be compared with results from atomic kinetics codes. In addition, the electron temperature is extracted from level population ratios of nearby energy levels in Li- and Be-like ions, which can be used to test heating models of photoionized plasmas.

  5. 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.

  6. Nondipole Effects in Double Photoionization of He

    SciTech Connect

    Istomin, A. Y.; Starace, A. F.; Manakov, N. L.; Meremianin, A. V.

    2006-01-09

    Lowest-order nondipole effects are studied in double photoionization (DPI) of the He atom. Ab initio parametrizations of the quadrupole transition amplitude for DPI from the 1S0-state are presented in terms of the exact two-electron reduced matrix elements. Parametrizations for the dipole-quadrupole triply differential cross section (TDCS) and doubly differential cross section (DDCS) are presented in terms of polarization-independent amplitudes for the case of an elliptically polarized photon. Expressions for the DDCS in terms of the reduced two-electron matrix elements are also given. A general analysis of retardation-induced asymmetries of the TDCS including the circular dichroism effect at equal energy sharing is presented. Our numerical results exhibit a nondipole forward-backward asymmetry in the TDCS for DPI of He at an excess energy of 450 eV that is in qualitative agreement with existing experimental data.

  7. 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.

  8. Electron localization following attosecond molecular photoionization.

    PubMed

    Sansone, G; Kelkensberg, F; Pérez-Torres, J F; Morales, F; Kling, M F; Siu, W; Ghafur, O; Johnsson, P; Swoboda, M; Benedetti, E; Ferrari, F; Lépine, F; Sanz-Vicario, J L; Zherebtsov, S; Znakovskaya, I; L'huillier, A; Ivanov, M Yu; Nisoli, M; Martín, F; Vrakking, M J J

    2010-06-10

    For the past several decades, we have been able to directly probe the motion of atoms that is associated with chemical transformations and which occurs on the femtosecond (10(-15)-s) timescale. However, studying the inner workings of atoms and molecules on the electronic timescale has become possible only with the recent development of isolated attosecond (10(-18)-s) laser pulses. Such pulses have been used to investigate atomic photoexcitation and photoionization and electron dynamics in solids, and in molecules could help explore the prompt charge redistribution and localization that accompany photoexcitation processes. In recent work, the dissociative ionization of H(2) and D(2) was monitored on femtosecond timescales and controlled using few-cycle near-infrared laser pulses. Here we report a molecular attosecond pump-probe experiment based on that work: H(2) and D(2) are dissociatively ionized by a sequence comprising an isolated attosecond ultraviolet pulse and an intense few-cycle infrared pulse, and a localization of the electronic charge distribution within the molecule is measured that depends-with attosecond time resolution-on the delay between the pump and probe pulses. The localization occurs by means of two mechanisms, where the infrared laser influences the photoionization or the dissociation of the molecular ion. In the first case, charge localization arises from quantum mechanical interference involving autoionizing states and the laser-altered wavefunction of the departing electron. In the second case, charge localization arises owing to laser-driven population transfer between different electronic states of the molecular ion. These results establish attosecond pump-probe strategies as a powerful tool for investigating the complex molecular dynamics that result from the coupling between electronic and nuclear motions beyond the usual Born-Oppenheimer approximation.

  9. Photoionization Spectroscopy of Clusters

    NASA Astrophysics Data System (ADS)

    Dao, Phan Danh

    Studies of the electronic energies in van der Waals molecules (sometimes referred to as clusters or complexes) help one unravel the microscopic details of the condensed state. Furthermore, they provide the connection between gas-phase and condensed-phase sciences. To achieve this goal, we undertake (1) the spectroscopic studies of van der Waals complexes; (2) the determination of the ionization energies of van der Waals complexes, as well as of mixed alkali metal clusters (e.g., K(,n)O); and (3) the studies of processes that occur upon and after the ionization of van der Waals molecules (namely, dissociation and intracluster reactions). A brief discussion of the non-equilibrium synthesis of weakly bound molecules is given. The operation and performance of the pulsed supersonic jet are described along with some theoretical considerations. The characteristic features of the technique of laser ionization are presented with emphasis on its performance as a spectroscopic tool. Resonance two-photon ionization and time-of-flight mass spectrometry provide us with the tool to measure the perturbed electronic excited state of van der Waals complexes. In these studies, the chromophore species is an aromatic molecule having a single ring (phenylacetylene and para-xylene); and the "solvent" species are rare gas atoms, as well as a variey of molecules. In the case of chromophore-rare gas complexes, the S(,1) excited state is red-shifted, with respect to the nascent chromophore, and the magnitude of the shift shows a definite dependence on the atomic polarizability. Other salient trends of the measured spectral shifts are also discussed. In the measurement of complex ionization energies, the use of two tunable UV lasers is required. With p-xylene(.)Ar(,n) complexes (n = 1-6), these energies vary almost linearly with the number of atoms. Also discussed in the text are the effects of ionization in a weak DC field. A simple hydrogenic model of field-ionization is experimentally

  10. Photoionization of Synchrotron-Radiation-Excited Atoms: Separating Partial Cross Sections by Full Polarization Control

    SciTech Connect

    Aloiese, S.; Meyer, M.; Cubaynes, D.; Grum-Grzhimailo, A. N.

    2005-06-10

    Resonant atomic excitation by synchrotron radiation and subsequent ionization by a tunable dye laser is used to study the photoionization of short-lived Rydberg states in Xe. By combining circular and linear polarization of the synchrotron as well as of the laser photons the partial photoionization cross sections were separated in the region of overlapping autoionizing resonances of different symmetry and the parameters of the resonances were extracted.

  11. 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.

  12. Photoionization of methanol and formaldehyde

    NASA Technical Reports Server (NTRS)

    Warneck, P.

    1971-01-01

    Photoions produced in methanol and formaldehyde by radiation in the spectral region 450-1150 A were analyzed mass spectrometrically, and their relative yields were determined as a function of wavelength. First ionization potentials were determined, and the ion yield curves were interpreted in terms of ionization processes in conjunction with other data. Fragment ions were detected on mass numbers of 31, 30, 29, 15, and 14 for methanol, and 29, 2, and 1 for formaldehyde. The associated appearance potentials were determined and were used to calculate heats of formation of the ions CH2OH(+) and HCO(+), and the radicals CH3, CH2, and HCO.

  13. Photoionization Efficiencies of Five Polycyclic Aromatic Hydrocarbons.

    PubMed

    Johansson, K Olof; Campbell, Matthew F; Elvati, Paolo; Schrader, Paul E; Zádor, Judit; Richards-Henderson, Nicole K; Wilson, Kevin R; Violi, Angela; Michelsen, Hope A

    2017-06-15

    We have measured photoionization-efficiency curves for pyrene, fluoranthene, chrysene, perylene, and coronene in the photon energy range of 7.5-10.2 eV and derived their photoionization cross-section curves in this energy range. All measurements were performed using tunable vacuum ultraviolet (VUV) radiation generated at the Advanced Light Source synchrotron at Lawrence Berkeley National Laboratory. The VUV radiation was used for photoionization, and detection was performed using a time-of-flight mass spectrometer. We measured the photoionization efficiency of 2,5-dimethylfuran simultaneously with those of pyrene, fluoranthene, chrysene, perylene, and coronene to obtain references of the photon flux during each measurement from the known photoionization cross-section curve of 2,5-dimethylfuran.

  14. Photoionization Efficiencies of Five Polycyclic Aromatic Hydrocarbons

    DOE PAGES

    Johansson, K. Olof; Campbell, Matthew F.; Elvati, Paolo; ...

    2017-05-18

    We have measured photoionization-efficiency curves for pyrene, fluoranthene, chrysene, perylene, and coronene in the photon energy range of 7.5-10.2 eV and derived their photoionization cross-section curves in this energy range. All measurements were performed using tunable vacuum ultraviolet (VUV) radiation generated at the Advanced Light Source synchrotron at Lawrence Berkeley National Laboratory. The VUV radiation was used for photoionization, and detection was performed using a time-of-flight mass spectrometer. We measured the photoionization efficiency of 2,5-dimethylfuran simultaneously with those of pyrene, fluoranthene, chrysene, perylene, and coronene to obtain references of the photon flux during each measurement from the known photoionization cross-sectionmore » curve of 2,5- dimethylfuran.« less

  15. 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.

  16. 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.

  17. Nonperturbative theory of double photoionization of the hydrogen molecule

    SciTech Connect

    Vanroose, W.; Martin, F.; Rescigno, T.N.; McCurdy, C.W.

    2004-10-01

    We present completely ab initio nonperturbative calculations of the integral and single differential cross sections for double photoionization of H2 for photon energies from 53.9 to 75.7 eV. The method of exterior complex scaling, implemented with B-splines, is used to solve the Schrodinger equation for a correlated continuum wave function corresponding to a single photon having been absorbed by a correlated initial state. The results are in good agreement with experimental integral cross sections.

  18. 2s photoionization and subsequent Auger cascade in atomic Si

    SciTech Connect

    Partanen, L.; Fritzsche, S.; Jaenkaelae, K.; Huttula, M.; Osmekhin, S.; Aksela, H.; Aksela, S.; Urpelainen, S.

    2010-06-15

    The 2s photoionization and subsequent Auger transition cascade in atomic Si were studied by means of synchrotron-radiation-induced electron spectroscopy. After the 2s photoionization, the core hole states decay predominantly by a two-step Auger transition cascade into the triply ionized [Ne]nl states. The ionization channels of the 2s core-ionized Si{sup +} atoms to Si{sup 3+} ions were observed by measuring the conventional Auger electron spectra of the L{sub 1}-L{sub 2,3}M Coster-Kronig transitions and the L{sub 2,3}M-MMM Auger transitions. The observed L{sub 1}-L{sub 2,3}M and L{sub 2,3}M-MMM Auger spectra were analyzed by means of extensive multiconfiguration Dirac-Fock computations. We found that the electron correlation plays a prominent role in the Auger cascade, especially for the final-step Auger L{sub 2,3}M-MMM spectrum. Additionally, it was seen that the L{sub 2,3}M-MMM Auger spectrum of Si includes more Auger groups than the isoelectronic L{sub 2,3}-MM Auger spectrum of Al. Thus, more information on the intermediate ionic states is obtained if they are produced by Auger cascade rather than by direct photoionization.

  19. 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.

  20. Multichannel interactions in the resonant photoionization of HCl

    NASA Astrophysics Data System (ADS)

    White, M. G.; Leroi, G. E.; Ho, M.-H.; Poliakoff, E. D.

    1987-12-01

    Vibrational state distributions of the A 2Σ+ excited state of HCl+ were measured by dispersed fluorescence following resonant photoionization. Autoionization of levels excited at the NeI resonance line strongly influence the vibrational branching ratios of the A 2Σ+ state although not in accord with the propensity rule expected for vibrational autoionization. Other measurements utilizing total fluorescence yields and synchrotron radiation confirm the presence of competing dissociation channels for autoionizing Rydberg states converging to the A 2Σ+ limit. These results are discussed in terms of the multichannel interactions responsible for determining the observed ion and fragment product distributions.

  1. Photoionization of rare gas clusters

    NASA Astrophysics Data System (ADS)

    Zhang, Huaizhen

    This thesis concentrates on the study of photoionization of van der Waals clusters with different cluster sizes. The goal of the experimental investigation is to understand the electronic structure of van der Waals clusters and the electronic dynamics. These studies are fundamental to understand the interaction between UV-X rays and clusters. The experiments were performed at the Advanced Light Source at Lawrence Berkeley National Laboratory. The experimental method employs angle-resolved time-of-flight photoelectron spectrometry, one of the most powerful methods for probing the electronic structure of atoms, molecules, clusters and solids. The van der Waals cluster photoionization studies are focused on probing the evolution of the photoelectron angular distribution parameter as a function of photon energy and cluster size. The angular distribution has been known to be a sensitive probe of the electronic structure in atoms and molecules. However, it has not been used in the case of van der Waals clusters. We carried out outer-valence levels, inner-valence levels and core-levels cluster photoionization experiments. Specifically, this work reports on the first quantitative measurements of the angular distribution parameters of rare gas clusters as a function of average cluster sizes. Our findings for xenon clusters is that the overall photon-energy-dependent behavior of the photoelectrons from the clusters is very similar to that of the corresponding free atoms. However, distinct differences in the angular distribution point at cluster-size-dependent effects were found. For krypton clusters, in the photon energy range where atomic photoelectrons have a high angular anisotropy, our measurements show considerably more isotropic angular distributions for the cluster photoelectrons, especially right above the 3d and 4p thresholds. For the valence electrons, a surprising difference between the two spin-orbit components was found. For argon clusters, we found that the

  2. Photoionization of Cl+ from the 3s23p4 3P2,1,0 and the 3s23p4 1D2,1S0 states in the energy range 19-28 eV

    NASA Astrophysics Data System (ADS)

    McLaughlin, Brendan M.

    2017-01-01

    Absolute photoionization cross-sections for the Cl+ ion in its ground and the metastable states, 3s23p4 3P2,1,0 and 3s23p4 1D2,1S0, were measured recently at the Advanced Light Source at Lawrence Berkeley National Laboratory using the merged beams photon-ion technique at a photon energy resolution of 15 meV in the energy range 19-28 eV. These measurements are compared with large-scale Dirac-Coulomb R-matrix calculations in the same energy range. Photoionization of this sulphur-like chlorine ion is characterized by multiple Rydberg series of auto-ionizing resonances superimposed on a direct photoionization continuum. A wealth of resonance features observed in the experimental spectra is spectroscopically assigned, and their resonance parameters are tabulated and compared with the recent measurements. Metastable fractions in the parent ion beam are determined from this study. Theoretical resonance energies and quantum defects of the prominent Rydberg series 3s23p3nd, identified in the spectra as 3p → nd transitions, are compared with the available measurements made on this element. Weaker Rydberg series 3s23p3ns, identified as 3p → ns transitions and window resonances 3s3p4(4P)np features, due to 3s → np transitions, are also found in the spectra.

  3. Optimized PET imaging for 4D treatment planning in radiotherapy: the virtual 4D PET strategy.

    PubMed

    Gianoli, Chiara; Riboldi, Marco; Fontana, Giulia; Giri, Maria G; Grigolato, Daniela; Ferdeghini, Marco; Cavedon, Carlo; Baroni, Guido

    2015-02-01

    The purpose of the study is to evaluate the performance of a novel strategy, referred to as "virtual 4D PET", aiming at the optimization of hybrid 4D CT-PET scan for radiotherapy treatment planning. The virtual 4D PET strategy applies 4D CT motion modeling to avoid time-resolved PET image acquisition. This leads to a reduction of radioactive tracer administered to the patient and to a total acquisition time comparable to free-breathing PET studies. The proposed method exploits a motion model derived from 4D CT, which is applied to the free-breathing PET to recover respiratory motion and motion blur. The free-breathing PET is warped according to the motion model, in order to generate the virtual 4D PET. The virtual 4D PET strategy was tested on images obtained from a 4D computational anthropomorphic phantom. The performance was compared to conventional motion compensated 4D PET. Tests were also carried out on clinical 4D CT-PET scans coming from seven lung and liver cancer patients. The virtual 4D PET strategy was able to recover lesion motion, with comparable performance with respect to the motion compensated 4D PET. The compensation of the activity blurring due to motion was successfully achieved in terms of spill out removal. Specific limitations were highlighted in terms of partial volume compensation. Results on clinical 4D CT-PET scans confirmed the efficacy in 4D PET count statistics optimization, as equal to the free-breathing PET, and recovery of lesion motion. Compared to conventional motion compensation strategies that explicitly require 4D PET imaging, the virtual 4D PET strategy reduces clinical workload and computational costs, resulting in significant advantages for radiotherapy treatment planning.

  4. K -shell double photoionization of Be, Mg, and Ca

    NASA Astrophysics Data System (ADS)

    Kheifets, A. S.; Bray, Igor; Hoszowska, J.

    2009-04-01

    We perform convergent close-coupling calculations of double photoionization (DPI) of the K -shell of alkaline-earth metal atoms (Be, Mg, and Ca) from the threshold to the nonrelativistic limit of infinite photon energy. Theoretical double-to-single photoionization cross-section ratios for Mg and Ca are compared with experimental values derived from high-resolution x-ray spectra following the radiative decay of the K -shell double vacancy. We investigate the role of many-electron correlations in the ground and doubly-ionized final states played in the DPI process. Universal scaling of DPI cross section with an effective nuclear charge is examined in neutral atoms in comparison with corresponding heliumlike ions.

  5. Double photoionization of halogenated benzene

    SciTech Connect

    AlKhaldi, Mashaal Q.; Wehlitz, Ralf

    2016-01-28

    We have experimentally investigated the double-photoionization process in C{sub 6}BrF{sub 5} using monochromatized synchrotron radiation. We compare our results with previously published data for partially deuterated benzene (C{sub 6}H{sub 3}D{sub 3}) over a wide range of photon energies from threshold to 270 eV. A broad resonance in the ratio of doubly to singly charged parent ions at about 65 eV appears shifted in energy compared to benzene data. This shift is due to the difference in the bond lengths in two molecules. A simple model can explain the shape of this resonance. At higher photon energies, we observe another broad resonance that can be explained as a second harmonic of the first resonance.

  6. Nondipole effects in helium photoionization

    NASA Astrophysics Data System (ADS)

    Argenti, Luca; Moccia, Roberto

    2010-12-01

    An accurate calculation of the nondipole anisotropy parameter γ in the photoionization of helium below the N = 2 threshold is presented. The calculated results are in fairly good agreement with the experimental results of Krässig et al (2002 Phys. Rev. Lett. 88 203002), but not as good as the accuracy of the calculation should have warranted. A careful examination of the possible causes for the observed discrepancies between theory and experiment seems to rule out any role either of the multipolar terms higher than the electric quadrupole, or of the singlet-triplet spin-orbit mixing. It is argued that such discrepancies might have an instrumental origin, due to the difficulty of measuring vanishingly small total cross sections σtot with the required accuracy. In such eventuality, it might be more appropriate to use a parameter other than γ, such as for instance the drag current, to measure the nondipole anisotropy of the photoelectron angular distribution.

  7. Photoionization of ClII

    NASA Astrophysics Data System (ADS)

    Nahar, Sultana; Hernández, E.; Antillón, A.; Morales, A.; González, O.; Macaluso, D.; Hanstorp, D.; Aguilar, A.; Juárez, A.; Hinojosa, G.

    2014-05-01

    The cross section and spectrum for the process of single photoionization of the chlorine cation was measured in the energy range of 19.5 to 28.0 eV with a photon energy resolution of 20 meV. Over a non resonant cross section, resonant structures originated from initinal Cl+ 3P(J=0,1,2) manifold converging mainly to 2P(J=3/2) and 2D(J=5/2) are identified. A theoretical calculation based on the close coupling R-matrix is under progress. CONACYT CB-2011 167631. US National Science Fundation, DGAPA IN106813, The ALS is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. DOE Cntrct. DE-AC02-05CH11231. Montana Space Grant Consortium, Swedish Research Council.

  8. 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.

  9. 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!

  10. Excitation of the symmetry forbidden bending mode in molecular photoionization

    NASA Astrophysics Data System (ADS)

    Miller, J. Scott; Poliakoff, E. D.; Miller, Thomas F.; Natalense, Alexandra P. P.; Lucchese, Robert R.

    2001-03-01

    We present results on the energy dependence of the vibrational branching ratio for the bending mode in CO2 3σu-1 photoionization. Specifically, we determine the v+=(0,1,0)/v+=(0,0,0) intensity ratio by detecting dispersed fluorescence from the electronically excited photoions. The results exhibit large deviations over a very wide energy range, 18state is forbidden by symmetry, and while observations of such features are well established in photoelectron spectroscopy, their appearance is normally ascribed to vibronic coupling in the ionic hole state. In this case, we find that such explanations fail to account for the energy dependence of the branching ratio. These deviations indicate that the continuum photoelectron participates in transferring oscillator strength to the nominally forbidden vibrational transition. A theoretical framework is developed for interpreting the experimental data, and Schwinger variational calculations are performed. These calculations demonstrate that the continuum electron is responsible for the observation of the excited bending mode as well as its energy dependence. This is an intrachannel effect that is best described as photoelectron-induced vibronic symmetry breaking. This appears to be a general phenomenon, and it may be useful in illuminating connections between bond angle and photoionization spectroscopies. The magnitude of these deviations display the utility of vibrationally resolved studies, and the extent over which these changes occur underscores the necessity of broad range studies to elucidate slowly varying characteristics in photoionization continua.

  11. Femtosecond pump-probe photoionization-photofragmentation spectroscopy: Photoionization-induced twisting and coherent vibrational motion of azobenzene cation

    NASA Astrophysics Data System (ADS)

    Ho-Wei, Jr.; Chen, Wei-Kan; Cheng, Po-Yuan

    2009-10-01

    We report studies of ultrafast dynamics of azobenzene cation using femtosecond photoionization-photofragmentation spectroscopy. In our experiments, a femtosecond pump pulse first produces an ensemble of azobenzene cations via photoionization of the neutrals. A delayed probe pulse then brings the evolving ionic system to excited states that ultimately undergo ion fragmentation. The dynamics is followed by monitoring either the parent-ion depletion or fragment-ion formation as a function of the pump-probe delay time. The observed transients for azobenzene cation are characterized by a constant ion depletion modulated by a rapidly damped oscillatory signal with a period of about 1 ps. Theoretical calculations suggest that the oscillation arises from a vibration motion along the twisting inversion coordinate involving displacements in CNNC and phenyl-ring torsions. The oscillation is damped rapidly with a time constant of about 1.2 ps, suggesting that energy dissipation from the active mode to bath modes takes place in this time scale.

  12. High-Resolution Photoelectron and Photoionization Spectroscopy

    NASA Astrophysics Data System (ADS)

    Merkt, F.

    2012-06-01

    Since its development in the late 1950s and early 1960s, photoelectron spectroscopy has established itself as an important method to study the electronic structure of molecules, their photoionization dynamics, and the structure and dynamics of molecular cations. In recent years, and particularly since the development of pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy, considerable progress has been made in the resolution that can be achieved by photoelectron spectroscopy. This progress relies on the systematic exploitation of the unusual physical properties of high Rydberg states and enables one today to resolve the rotational structure in the photoelectron spectra of even large molecules and the hyperfine structure in the photoelectron spectra of small molecules. This talk will begin with a brief historical review of photoelectron spectroscopy. Then, the relationship between photoelectron spectroscopy, photoionization spectroscopy and the spectroscopy of high Rydberg states will be discussed. It will be explained how this relationship is currently exploited to improve the resolution achievable by PFI-ZEKE photoelectron spectroscopy. Then, the physical principles that are at the heart of the latest methods related to high-resolution photoelectron spectroscopy will be described together with their fundamental limitations. Depending on the resolution and the spectral range needed to address a specific scientific problem, a choice can be made between several different methods with spectral resolutions ranging from 30 GHz to better than 1 MHz. The talk will summarize the current state of the art in gas-phase photoelectron spectroscopy and be illustrated by several examples, primarily taken from the research in my group, in which photoelectron spectroscopy has contributed to answer questions concerning the structure and dynamics of small-sized molecular cations. F. I. Vilesov, B. C. Kurbatov, and N. Terrenin, Soviet Phys. (Doklady) 6

  13. 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.

  14. 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.

  15. Alignment of photoions far from threshold

    NASA Astrophysics Data System (ADS)

    Das, Romith; Wu, Chuanyong; Mihill, A. G.; Poliakoff, E. D.; Wang, Kwanghsi; McKoy, V.

    1994-09-01

    We present results of measurements and calculations of the alignment for CO+(B 2Σ+) photoions over an extended energy range (0≤Ek≤210 eV). The polarization of CO+(B 2Σ+→X 2Σ+) fluorescence indicates that the photoions retain significant alignment even at high energies. Agreement between the measured and calculated polarization of the fluorescence is excellent.

  16. 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

  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. 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.

  19. Photoionization sensors for non-invasive medical diagnostics

    NASA Astrophysics Data System (ADS)

    Mustafaev, Aleksandr; Rastvorova, Iuliia; Khobnya, Kristina; Podenko, Sofia

    2016-09-01

    The analysis of biomarkers can help to identify the significant number of diseases: lung cancer, tuberculosis, diabetes, high levels of stress, psychosomatic disorders etc. To implement continuous monitoring of the state of human health, compact VUV photoionization detector with current-voltage measurement is designed by Saint-Petersburg Mining University Plasma Research Group. This sensor is based on the patented method of stabilization of electric parameters - CES (Collisional Electron Spectroscopy). During the operation at atmospheric pressure VUV photoionization sensor measures the energy of electrons, produced in the ionization with the resonance photons, whose wavelength situated in the vacuum ultraviolet (VUV). A special software was developed to obtain the second-order derivative of the I-U characteristics, taken by the VUV sensor, to construct the energy spectra of the characteristic electrons. VUV photoionization detector has an unique set of parameters: small size (10*10*1 mm), low cost, wide range of recognizable molecules, as well as accuracy, sufficient for using this instrument for the medical purposes. This device can be used for non-invasive medical diagnostics without compromising the quality of life, for control of environment and human life. Work supported by Foundation for Assistance to Small Innovative Enterprises in Science and Technology.

  20. Excitons in Cuprous Oxide: Photoionization and Other Multiphoton Processes

    NASA Astrophysics Data System (ADS)

    Frazer, Nicholas Laszlo

    In cuprous oxide (Cu2O), momentum from the absorption of two infrared photons to make an orthoexciton is conserved and detected through the photon component of a resulting mixed exciton/photon (quadrupole exciton polariton) state. I demonstrated that this process, which actually makes the photon momentum more precisely defined, is disrupted by photoionization of excitons. Some processes are known to affect exciton propagation in both the pump and exciton stages, such as phonon emission, exciton-exciton (Auger) scattering, and third harmonic generation. These processes alone were not able to explain all observed losses of excitons or all detected scattering products, which lead me to design an optical pump-probe experiment to measure the exciton photoionization cross section, which is (3.9+/-0.2) x 10-22 m2. This dissertation describes the synthesis of cuprous oxide crystals using oxidation of copper, crystallization from melt with the optical floating zone method, and annealing. The cuprous oxide crystals were characterized using time and space resolved luminescence, leading to the discovery of new defect properties. Selection rules and overall efficiency of third harmonic generation in these crystals were characterized. Exciton photoionization was demonstrated through the depletion of polariton luminescence by an optical probe, the production of phonon linked luminescence as a scattering product, temporal delay of the probe, and time resolved luminescence. The results are integrated with the traditional dynamical model of exciton densities. An additional investigation of copper/cuprous oxide/gold photovoltaic devices is appended.

  1. 4D DSA reconstruction using tomosynthesis projections

    NASA Astrophysics Data System (ADS)

    Buehler, Marc; Slagowski, Jordan M.; Mistretta, Charles A.; Strother, Charles M.; Speidel, Michael A.

    2017-03-01

    We investigate the use of tomosynthesis in 4D DSA to improve the accuracy of reconstructed vessel time-attenuation curves (TACs). It is hypothesized that a narrow-angle tomosynthesis dataset for each time point can be exploited to reduce artifacts caused by vessel overlap in individual projections. 4D DSA reconstructs time-resolved 3D angiographic volumes from a typical 3D DSA scan consisting of mask and iodine-enhanced C-arm rotations. Tomosynthesis projections are obtained either from a conventional C-arm rotation, or from an inverse geometry scanning-beam digital x-ray (SBDX) system. In the proposed method, rays of the tomosynthesis dataset which pass through multiple vessels can be ignored, allowing the non-overlapped rays to impart temporal information to the 4D DSA. The technique was tested in simulated scans of 2 mm diameter vessels separated by 2 to 5 cm, with TACs following either early or late enhancement. In standard 4D DSA, overlap artifacts were clearly present. Use of tomosynthesis projections in 4D DSA reduced TAC artifacts caused by vessel overlap, when a sufficient fraction of non-overlapped rays was available in each time frame. In cases where full overlap between vessels occurred, information could be recovered via a proposed image space interpolation technique. SBDX provides a tomosynthesis scan for each frame period in a rotational acquisition, whereas a standard C-arm geometry requires the grouping of multiple frames.

  2. GL4D: a GPU-based architecture for interactive 4D visualization.

    PubMed

    Chu, Alan; Fu, Chi-Wing; Hanson, Andrew J; Heng, Pheng-Ann

    2009-01-01

    This paper describes GL4D, an interactive system for visualizing 2-manifolds and 3-manifolds embedded in four Euclidean dimensions and illuminated by 4D light sources. It is a tetrahedron-based rendering pipeline that projects geometry into volume images, an exact parallel to the conventional triangle-based rendering pipeline for 3D graphics. Novel features include GPU-based algorithms for real-time 4D occlusion handling and transparency compositing; we thus enable a previously impossible level of quality and interactivity for exploring lit 4D objects. The 4D tetrahedrons are stored in GPU memory as vertex buffer objects, and the vertex shader is used to perform per-vertex 4D modelview transformations and 4D-to-3D projection. The geometry shader extension is utilized to slice the projected tetrahedrons and rasterize the slices into individual 2D layers of voxel fragments. Finally, the fragment shader performs per-voxel operations such as lighting and alpha blending with previously computed layers. We account for 4D voxel occlusion along the 4D-to-3D projection ray by supporting a multi-pass back-to-front fragment composition along the projection ray; to accomplish this, we exploit a new adaptation of the dual depth peeling technique to produce correct volume image data and to simultaneously render the resulting volume data using 3D transfer functions into the final 2D image. Previous CPU implementations of the rendering of 4D-embedded 3-manifolds could not perform either the 4D depth-buffered projection or manipulation of the volume-rendered image in real-time; in particular, the dual depth peeling algorithm is a novel GPU-based solution to the real-time 4D depth-buffering problem. GL4D is implemented as an integrated OpenGL-style API library, so that the underlying shader operations are as transparent as possible to the user.

  3. Photoelectron wave function in photoionization: Plane wave or Coulomb wave? [Does photoionization of neutral targets produce Coulomb or plane waves?

    DOE PAGES

    Gozem, Samer; Gunina, Anastasia O.; Ichino, Takatoshi; ...

    2015-10-28

    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 photoelectronmore » 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. Finally, 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.« less

  4. 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.

  5. 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.

  6. Photoionized Plasmas in the Z Facility and in Astrophysics

    NASA Astrophysics Data System (ADS)

    Mancini, Roberto

    2013-06-01

    Many astrophysical environments such as x-ray binaries, active galactic nuclei, and accretion disks of compact objects have photoionized plasmas. Detailed x-ray spectral observations performed with the Chandra and XMM-Newton orbiting telescopes provide critical information on the state of photoionized plasmas. However, the complexity of the astrophysical environment makes the spectral analysis challenging, and thus laboratory experiments are important for data interpretation and testing of modeling codes. The Z facility at Sandia National Laboratories is a powerful source of x-rays to produce and study in the laboratory photoionized plasmas relevant for astrophysics under well characterized conditions. We discuss an experimental and theory/modeling effort in which the intense x-ray flux emitted at the collapse of a z-pinch implosion conducted at the Z pulsed-power machine is employed to produce a neon photoionized plasma. The broadband x-ray radiation flux from the z-pinch is used to both create the photoionized plasma and provide a source of backlighting photons to study the atomic kinetics through K-shell line absorption spectroscopy. The plasma is contained in a cm-scale gas cell that can be located at different distances from the z-pinch, thus effectively controlling the x-ray flux producing the plasma. Time-integrated and gated transmission spectra are recorded with a spectrometer equipped with two elliptically-bent KAP crystals and a set of slits to record up to six spatially-resolved spectra per crystal in the same shot. The transmission data shows a rich line absorption spectrum that spans over several ionization stages of neon including Be-, Li-, He- and H-like ions. Modeling calculations are used to interpret the transmission spectra recorded in the Z experiments with the goal of extracting the charge- state distribution, electron temperature and the radiation flux driving the plasma, as well as to determine the ionization parameter of the plasma. This

  7. Photoionization and absorption spectrum of formaldehyde in the vacuum ultraviolet.

    NASA Technical Reports Server (NTRS)

    Mentall, J. E.; Gentieu, E. P.; Krauss, M.; Neumann, D.

    1971-01-01

    The measurements have been conducted in the spectral range from 600 to 2000 A. Integrated oscillator strengths were determined for a number of strong Rydberg transitions above 1200 A. From the photoionization curve the first adiabatic ionization potential was found to be 10.87 plus or minus 0.01 eV. As an aid in interpreting the absorption spectrum, theoretical calculations were made using a single-configuration self-consistent field procedure for the Rydberg states and a model which included mixing between the Rydberg and valence states.

  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. 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.

  10. Attosecond study of confinement in photoionization of xenon caged in C60

    NASA Astrophysics Data System (ADS)

    Magrakvelidze, Maia; Dixit, Gopal; Madjet, Mohamed; Chakraborty, Himadri

    2015-05-01

    Effects of atom-fullerene orbital hybridization and C60 cavity on the attosecond time delay of the photoionization of Xe in the Xe@C60 endohedral molecule are investigated using time dependent local density approximation (TDLDA) augmented by the Leeuwen and Baerends exchange-correlation functional. TDLDA Wigner-Smith delay is found to modify via three distinct mechanisms: (i) Screening (or anti-screening) of the atomic valence emission due to the plasmonic motions of C60 charge cloud; (ii) dynamical interactions between Xe Cooper minima and C60 cavity minima; and (iii) confinement oscillations in the photoionization of inner 4d shell of Xe from the resonant formation of standing waves inside the cavity. The effects may be experimentally accessible by the so called RABITT metrology. This work was supported by the U.S. National Science Foundation.

  11. Study of X-ray photoionized Fe plasma and comparisons with astrophysical modeling codes

    SciTech Connect

    Foord, M E; Heeter, R F; Chung, H; vanHoof, P M; Bailey, J E; Cuneo, M E; Liedahl, D A; Fournier, K B; Jonauskas, V; Kisielius, R; Ramsbottom, C; Springer, P T; Keenan, K P; Rose, S J; Goldstein, W H

    2005-04-29

    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 the ionization parameter {zeta} in the plasma reaches values {zeta} = 20-25 erg cm s{sup -1} under near steady-state conditions. A curve-of-growth analysis, which includes the effects of velocity gradients in a one-dimensional expanding plasma, fits the observed line opacities. Absorption lines are tabulated in the wavelength region 8-17 {angstrom}. Initial comparisons with a number of astrophysical x-ray photoionization models show reasonable agreement.

  12. Experimental absolute cross section for photoionization of Xe^7+

    NASA Astrophysics Data System (ADS)

    Schippers, S.; Müller, A.; Esteves, D.; Habibi, M.; Aguilar, A.; Kilcoyne, A. L. D.

    2010-03-01

    Collision processes with highly charged xenon ions are of interest for UV-radiation generation in plasma discharges, for fusion research and for space craft propulsion. Here we report results for the photoionization of Xe^7+ ionsootnotetextS. Schippers et al., J. Phys.: Conf. Ser. (in print) which were measured at the photon-ion end station of ALS beamline 10.0.1. As compared with the only previous experimental studyootnotetextJ. M. Bizau et al., Phys. Rev. Lett. 84, 435 (2000) of this reaction, the present cross sections were obtained at higher energy resolution (50--80 meV vs. 200--500 meV) and on an absolute cross section scale. In the experimental photon energy range of 95--145 eV the cross section is dominated by resonances associated with 4d->5f excitation and subsequent autoionization. The most prominent feature in the measured spectrum is the 4d^9,s,f, resonance at 121.14±0.02 eV which reaches a peak cross section of 1.2 Gb at 50 meV photon energy spread. The experimental resonance strength of 160 Mb eV (corresponding to an absorption oscillator strength of 1.46) is in fair agreement with the theoretical result^2.

  13. 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.

  14. Theory of attosecond delays in molecular photoionization

    NASA Astrophysics Data System (ADS)

    Baykusheva, Denitsa; Wörner, Hans Jakob

    2017-03-01

    We present a theoretical formalism for the calculation of attosecond delays in molecular photoionization. It is shown how delays relevant to one-photon-ionization, also known as Eisenbud-Wigner-Smith delays, can be obtained from the complex dipole matrix elements provided by molecular quantum scattering theory. These results are used to derive formulae for the delays measured by two-photon attosecond interferometry based on an attosecond pulse train and a dressing femtosecond infrared pulse. These effective delays are first expressed in the molecular frame where maximal information about the molecular photoionization dynamics is available. The effects of averaging over the emission direction of the electron and the molecular orientation are introduced analytically. We illustrate this general formalism for the case of two polyatomic molecules. N2O serves as an example of a polar linear molecule characterized by complex photoionization dynamics resulting from the presence of molecular shape resonances. H2O illustrates the case of a non-linear molecule with comparably simple photoionization dynamics resulting from a flat continuum. Our theory establishes the foundation for interpreting measurements of the photoionization dynamics of all molecules by attosecond metrology.

  15. Digit ratio (2D:4D) in homosexual and heterosexual men from Austria.

    PubMed

    Voracek, Martin; Manning, John T; Ponocny, Ivo

    2005-06-01

    Neurohormonal theories of sexual orientation emphasize the organizational effects of testosterone on the developing brain. A recent suggestion, that the ratio of the length of the 2nd and 4th digits (2D:4D) is negatively correlated with prenatal testosterone, has led to a number of studies of 2D:4D in homosexual and heterosexual men and women. The results have been mixed. In comparison to heterosexual men, mean 2D:4D in gay men has been reported to be hypermasculinized (lower 2D:4D), hypomasculinized (higher 2D:4D), or to show no significant difference. Here, we report mean 2D:4D in Austrian homosexual and heterosexual men. We found no significant difference between means for homosexual and heterosexual 2D:4D, with values for both falling between 0.96 to 0.97. There are now 6 reports of 2D:4D in heterosexual and homosexual men. Considering Caucasian men, the studies from the United States show low heterosexual mean 2D:4D, and homosexual mean 2D:4D is higher or similar to that of heterosexuals. The European studies show high heterosexual mean 2D:4D, and comparisons with homosexuals reveal the latter to have lower or similar mean 2D:4D to that of heterosexuals. We discuss these results in relation to the suggestion that mean 2D:4D in heterosexual men differs across populations but mean 2D:4D in homosexuals shows less geographical variation (the "uniform mean hypothesis"). It is concluded that more data are required to clarify whether or not there is a 2D:4D effect for sexual orientation in men.

  16. Energies and Spectral Lines for the States of 4 s 24 p 2, 4 s4 p 3, and 4 s 24 p4 d Configurations in Ge-Like Te, Xe, and Ba Ions

    NASA Astrophysics Data System (ADS)

    Hao, L. H.; Kang, X. P.; Liu, J. J.

    2017-05-01

    The energy levels, wavelengths, transition rates, and line strengths have been calculated for the 4 s 24 p 2-4 s4 p 3 and 4 s 24 p 2-4 s 24 p4 d allowed transitions occurring within the ground configuration (4 s 24 p 2) in the heavy Ge-like Te, Xe, and Ba ions. The fully relativistic multiconfiguration Dirac-Hartree-Fock method taking into account both correlations within the n = 5 complex and the QED effects has been used in the calculations. The calculation results are found to agree well with the data obtained on the TFR tokamak and by recent EBIT measurements in Xe. The isoelectronic sequence of the Ge-like ions is important in nuclear fusion research as their spectra may provide diagnostic information on magnetically confined plasmas.

  17. 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.

  18. Photo-ionization rate coefficients for the rare gases

    NASA Astrophysics Data System (ADS)

    Pang, Xuexia

    2005-01-01

    By introducing the converting method from electron-impact ionization cross sections to rate coefficients through using a semi-experiential formula, we try to probe a semi-experiential formula for converting the photo-ionization cross sections into photo-ionization rate coefficient. It"s found that photo-ionization rate coefficient is direct proportion to photo-ionization cross sections, the rate S is related with light resource.

  19. 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.

  20. 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.

  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.

  2. Interference effects in L-shell atomic double photoionization

    NASA Astrophysics Data System (ADS)

    Kheifets, A. S.; Bray, I.; Colgan, J.; Pindzola, M. S.

    2011-01-01

    Angular correlation pattern in two-electron continuum is very similar in double photoionization (DPI) of a neutral atom γ + A → A2 + + 2e- and electron-impact ionization of the corresponding singly charged ion e- + A+ → A2 + + 2e-. This allows us to identify and interpret interference effects in DPI of various L-shell atomic targets such as the metastable He* 1s 2s 1S and the ground state Li 1s22s and Be 1s22s2.

  3. Correspondence of electron spectra from photoionization and nuclear internal conversion

    SciTech Connect

    Wark, D.L.; Bartlett, R.; Bowles, T.J.; Robertson, R.G.H.; Sivia, D.S.; Trela, W.; Wilkerson, J.F. ); Brown, G.S. ); Crasemann, B.; Sorensen, S.L.; Schaphorst, S.J. ); Knapp, D.A.; Henderson, J. ); Tulkki, J.; Aberg, T. )

    1991-10-21

    Electron energy spectra have been measured that result from {ital K}-shell ionization of Kr by two different mechanisms: (1) photoionization and (2) internal conversion in the decay of the isomeric state of {sup 83}Kr. It is demonstrated experimentally that these spectra, including satellites on the low-energy side of the primary 1{ital s}-electron peak, are identical. A theoretical interpretation of the identity of the spectra is given. The spectra agree well with a relativistic many-electron calculation in which the satellites are attributed to excitation and ionization of {ital M} and {ital N} electrons during the {ital K}-ionization process.

  4. Double Photoionization of Helium Atom using effective Charges

    NASA Astrophysics Data System (ADS)

    Saha, Hari P.

    2012-06-01

    We will report the results of our investigation on double photoionization of helium atom using the recently extended MCHF method [1] for double photoionization of atoms. Calculation will be performed using wave functions for the initial and the final states with and without the electron correlation. The initial state wave function will be calculated using both the HF and MCHF methods The final state wave functions will be obtained using the asymptotic effective charge [2,3] to represent the electron correlation between the two final state continuum electrons. Using these wave functions, the triple differential cross sections will be calculated for 30 eV excess photon energy. The single and total integral cross sections will be obtained for photon energies from threshold to 300 eV. The results will be compared with the available experimental and the theoretical data. [4pt] [1] Hari P. Saha, J.Phys. B (submitted) [0pt] [2] M.R.H. Rudge, Rev. Mod. Phys. 40, 564 (1968) [0pt] [3] C.Pan and A.F Starace, Phys. Rev. Lett. 67, 185 (1991); Phys. Rev. A45, 4588 (1992)

  5. Respiratory gating and 4-D tomotherapy

    SciTech Connect

    Zhang Tiezhi

    2004-12-01

    Helical tomotherapy is a new intensity-modulated radiotherapy (IMRT) delivery process developed at the University of Wisconsin and TomoTherapy Inc. Tomotherapy may be of advantage in lung cancer treatment due to its rotational delivery mode. As with conventional IMRT delivery, however, intrafraction respiratory motion during a tomotherapy treatment causes unnecessary radiation to the healthy tissue. Possible solutions to these problems associated with intrafraction motion have been studied in this thesis. A spirometer is useful for monitoring breathing because of its direct correlation with lung volume changes. However, its inherent drift prevents its application in long-term breathing monitoring. With calibration and stabilization algorithms, a spirometer is able to provide accurate, long-term lung volume change measurements. Such a spirometer system is most suited for deep inspiration breath-hold (DIBH) treatments. An improved laser-spirometer combined system has also been developed for target tracking in 4-D treatment. Spirometer signals are used to calibrate the displacement measurements into lung volume changes, thereby eliminating scaling errors from daily setup variations. The laser displacement signals may also be used to correct spirometer drifts during operation. A new 4-D treatment technique has been developed to account for intrafraction motion in treatment planning. The patient's breathing and the beam delivery are synchronized, and the target motion/deformation is incorporated into treatment plan optimization. Results show that this new 4D treatment technique significantly reduces motion effects and provides improved patient tolerance.

  6. Double photoionization of hydrocarbons and aromatic molecules

    NASA Astrophysics Data System (ADS)

    Wehlitz, R.

    2016-11-01

    This article reviews the recent progress in the field of double photoionization of hydrocarbons and aromatic molecules using synchrotron radiation. First I will describe the importance of carbon-based molecules, which are all around us and are literally part of our life. They exhibit intriguing properties some of which can be probed via double photoionization, i.e., the simultaneous emission of two electrons. Furthermore, I will discuss the different mechanisms that can lead to a doubly charged organic molecule and will highlight those findings by comparing them with the results for atoms and other (simple) molecules. Finally, I will give an outlook on future directions on this subject.

  7. 4D CT lung ventilation images are affected by the 4D CT sorting method

    PubMed Central

    Yamamoto, Tokihiro; Kabus, Sven; Lorenz, Cristian; Johnston, Eric; Maxim, Peter G.; Diehn, Maximilian; Eclov, Neville; Barquero, Cristian; Loo, Billy W.; Keall, Paul J.

    2013-01-01

    Purpose: Four-dimensional (4D) computed tomography (CT) ventilation imaging is a novel promising technique for lung functional imaging. The current standard 4D CT technique using phase-based sorting frequently results in artifacts, which may deteriorate the accuracy of ventilation imaging. The purpose of this study was to quantify the variability of 4D CT ventilation imaging due to 4D CT sorting. Methods: 4D CT image sets from nine lung cancer patients were each sorted by the phase-based method and anatomic similarity-based method, designed to reduce artifacts, with corresponding ventilation images created for each method. Artifacts in the resulting 4D CT images were quantified with the artifact score which was defined based on the difference between the normalized cross correlation for CT slices within a CT data segment and that for CT slices bordering the interface between adjacent CT data segments. The ventilation variation was quantified using voxel-based Spearman rank correlation coefficients for all lung voxels, and Dice similarity coefficients (DSC) for the spatial overlap of low-functional lung volumes. Furthermore, the correlations with matching single-photon emission CT (SPECT) ventilation images (assumed ground truth) were evaluated for three patients to investigate which sorting method provides higher physiologic accuracy. Results: Anatomic similarity-based sorting reduced 4D CT artifacts compared to phase-based sorting (artifact score, 0.45 ± 0.14 vs 0.58 ± 0.24, p = 0.10 at peak-exhale; 0.63 ± 0.19 vs 0.71 ± 0.31, p = 0.25 at peak-inhale). The voxel-based correlation between the two ventilation images was 0.69 ± 0.26 on average, ranging from 0.03 to 0.85. The DSC was 0.71 ± 0.13 on average. Anatomic similarity-based sorting yielded significantly fewer lung voxels with paradoxical negative ventilation values than phase-based sorting (5.0 ± 2.6% vs 9.7 ± 8.4%, p = 0.05), and improved the correlation with SPECT ventilation regionally. Conclusions

  8. Vacuum ultraviolet photoionization mass spectrometric study of cyclohexene.

    PubMed

    Chen, Jun; Cao, Maoqi; Wei, Bin; Ding, Mengmeng; Shan, Xiaobin; Liu, Fuyi; Sheng, Liusi

    2016-02-01

    In this work, photoionization and dissociation of cyclohexene have been studied by means of coupling a reflectron time-of-flight mass spectrometer with the tunable vacuum ultraviolet (VUV) synchrotron radiation. The adiabatic ionization energy of cyclohexene as well as the appearance energies of its fragment ions C6 H9 (+) , C6 H7 (+) , C5 H7 (+) , C5 H5 (+) , C4 H6 (+) , C4 H5 (+) , C3 H5 (+) and C3 H3 (+) were derived from the onset of the photoionization efficiency (PIE) curves. The optimized structures for the transition states and intermediates on the ground state potential energy surfaces related to photodissociation of cyclohexene were characterized at the ωB97X-D/6-31+g(d,p) level. The coupled cluster method, CCSD(T)/cc-pVTZ, was employed to calculate the corresponding energies with the zero-point energy corrections by the ωB97X-D/6-31+g(d,p) approach. Combining experimental and theoretical results, possible formation pathways of the fragment ions were proposed and discussed in detail. The retro-Cope rearrangement was found to play a crucial role in the formation of C4 H6 (+) , C4 H5 (+) and C3 H5 (+) . Intramolecular hydrogen migrations were observed as dominant processes in most of the fragmentation pathways of cyclohexene. The present research provides a clear picture of the photoionization and dissociation processes of cyclohexene in the 8- to 15.5-eV photon energy region. Copyright © 2016 John Wiley & Sons, Ltd.

  9. 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.

  10. 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.

  11. 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.

  12. Rotational distributions of molecular photoions following resonant excitation

    NASA Astrophysics Data System (ADS)

    Poliakoff, E. D.; Chan, Jeffrey C. K.; White, M. G.

    1986-11-01

    We demonstrate that the photoelectron energy mediates the rotational energy distribution of N+2 ions created by photoionization, and conversely, that rotational energy determinations probe resonant excitation in molecular photoionization. Experimentally, this is accomplished by monitoring the dispersed fluorescence from N+2 (B 2Σ+u) photoions to determine their rotational energy distribution. These results demonstrate that while dipole selection rules constrain the total angular momentum of the electron-ion complex, the partitioning of angular momentum between the photoelectron and photoion depends on the photoejection dynamics. Implications for photoionization and electron impact ionizatin studies are discussed.

  13. Problems with vector confinement in 4d QCD

    NASA Astrophysics Data System (ADS)

    Simonov, Yu. A.

    2017-07-01

    It is shown that vector confinement does not support bound state spectrum in the 4d Dirac equation. The same property is confirmed in the heavy-light and light-light QCD systems. This situation is compared with the confinement in the 2d system, which is generated by the gluon exchange. Considering the existing theories of confinement, it is shown that both the field correlator approach and the dual superconductor model ensure the scalar confinement in contrast to the Gribov-Zwanziger model, where the confning Coulomb potential does not support bound states in the Dirac equation..

  14. 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.

  15. Absolute single-photoionization cross sections of Se2 +: Experiment and theory

    NASA Astrophysics Data System (ADS)

    Macaluso, D. A.; Aguilar, A.; Kilcoyne, A. L. D.; Red, E. C.; Bilodeau, R. C.; Phaneuf, R. A.; Sterling, N. C.; McLaughlin, B. M.

    2015-12-01

    Absolute single-photoionization cross-section measurements for Se2 + ions were performed at the Advanced Light Source at Lawrence Berkeley National Laboratory using the merged-beams photo-ion technique. Measurements were made at a photon energy resolution of 24 ±3 meV in the photon energy range 23.5-42.5 eV, spanning the ground state and low-lying metastable state ionization thresholds. To clearly resolve the resonant structure near the ground-state threshold, high-resolution measurements were made from 30.0 to 31.9 eV at a photon energy resolution of 6.7 ±0.7 meV. Numerous resonance features observed in the experimental spectra are assigned and their energies and quantum defects tabulated. The high-resolution cross-section measurements are compared with large-scale, state-of-the-art theoretical cross-section calculations obtained from the Dirac Coulomb R -matrix method. Suitable agreement is obtained over the entire photon energy range investigated. These results are an experimental determination of the absolute photoionization cross section of doubly ionized selenium and include a detailed analysis of the photoionization resonance spectrum of this ion.

  16. Time-energy mapping of photoelectron angular distribution: application to photoionization stereodynamics of nitric oxide.

    PubMed

    Suzuki, Yoshi-Ichi; Tang, Ying; Suzuki, Toshinori

    2012-05-28

    The time-energy mapping of the photoionization integral cross section and laboratory-frame photoelectron angular distribution is used to study photoionization stereodynamics of a diatomic molecule. The general theoretical formalism [Y. Suzuki and T. Suzuki, Mol. Phys., 2007, 105, 1675] is simplified for application to a diatomic molecule, and a high-resolution photoelectron imaging apparatus is used to determine the transition dipole moments and phase shifts of photoelectron partial waves in near-threshold and non-dissociative photoionization of NO from the A(2)Σ(+) state. The transition dipoles and phase shifts thus determined are in reasonable agreement with those by state-to-state photoionization experiment and Schwinger variational calculations. The difference of the phase shifts from those expected from the quantum defects of Rydberg states suggests occurrence of weak hybridization of different l-waves, in addition to the well-known s-d super complex. The circular dichroism in photoelectron angular distribution is also simulated from our results.

  17. Molecular photoionization as a probe of vibrational-rotational-electronic correlations

    NASA Astrophysics Data System (ADS)

    Rao, R. M.; Poliakoff, E. D.; Wang, Kwanghsi; McKoy, V.

    1996-06-01

    We determine the rotationally state-resolved 2σu-1 photoionization of N2 into alternative vibrational channels as a function of energy over a 200 eV range. Experiment and theory reveal that Cooper minima highlight the coupling between electronic, vibrational, and rotational degrees of freedom over this very wide range.

  18. Photoionization research on atomic radiation. 3: The ionization cross section of atomic nitrogen

    NASA Astrophysics Data System (ADS)

    Comes, F. J.; Elzer, A.

    1982-08-01

    The photoionization cross section of atomic nitrogen was measured between the ionization limit and 432 A. The experimental values are well fitted by those from a calculation of HENRY due to the dipole velocity approximation. A Rydberg series converging to the 5S-state of the ion is clearly identified from the ionization measurements and is shown to ionize.

  19. 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.

  20. Supercurrent anomalies in 4d SCFTs

    NASA Astrophysics Data System (ADS)

    Papadimitriou, Ioannis

    2017-07-01

    We use holographic renormalization of minimal N=2 gauged supergravity in order to derive the general form of the quantum Ward identities for 3d N=2 and 4d N=1 superconformal theories on general curved backgrounds, including an arbitrary fermionic source for the supercurrent. The Ward identities for 4d N=1 theories contain both bosonic and fermionic global anomalies, which we determine explicitly up to quadratic order in the supercurrent source. The Ward identities we derive apply to any superconformal theory, independently of whether it admits a holographic dual, except for the specific values of the a and c anomaly coefficients, which are equal due to our starting point of a two-derivative bulk supergravity theory. We show that the fermionic anomalies lead to an anomalous transformation of the supercurrent under rigid supersymmetry on backgrounds admitting Killing spinors, even if all superconformal anomalies are numerically zero on such backgrounds. The anomalous transformation of the supercurrent under rigid supersymmetry leads to an obstruction to the Q-exactness of the stress tensor in supersymmetric vacua, and may have implications for the applicability of localization techniques. We use this obstruction to the Q-exactness of the stress tensor, together with the Ward identities, in order to determine the general form of the stress tensor and R-current one-point functions in supersymmetric vacua, which allows us to obtain general expressions for the supersymmetric Casimir charges and partition function.

  1. 4D geomorphological evolution of intertropical islands

    NASA Astrophysics Data System (ADS)

    Pastier, Anne-Morwenn; Bezos, Antoine; Husson, Laurent; Pedoja, Kevin; Arias, Camilo; Elliot, Mary; Lacroix, Pascal; Imran, Andi Muhammad

    2017-04-01

    Coral reef terraces record joint variations of sea level and surface elevation. U/Th ratings on corals along with topographic/bathymetric profiles and eustatic reconstitutions allow to locally determine the vertical rate of ground motion, while numerical modelling of reef sequences allows to unravel the processes controlling the architecture of sequences, and high-resolution DEMs facilitates the detailed mapping of the sequences of reef terraces. Alltogether, these methods allow to extrapolate the local vertical rates towards an unprecedented resolution for 4D kinematics. We applied our method to uplifting islands of the tectonically active Buton Archipelago, SE Sulawesi, Indonesia. The area undergoes a general uplift revealed by the ubiquitous occurrence of uplifted and folded reef sequences. We dated some 40 samples using U/Th, acquired sonar and dGPS profiles, and constructed high-res DEMs (Pleiades). Local vertical rates (from 0.2 to 0.28 mm/yr) were determined. Detailed geomorphological mapping of the lateral variations of the terraces are converted into time and space variations of uplift rates. Extrapolating the higher, undated terraces permits to reconstruct the overall 4D geomorphology history over the last Ma. In turns, these results give a unique view on the structural kinematics.

  2. 4d Spectra from BPS Quiver Dualities

    NASA Astrophysics Data System (ADS)

    Espahbodi, Sam

    We attack the question of BPS occupancy in a wide class of 4d N = 2 quantum field theories. We first review the Seiberg-Witten approach to finding the low energy Wilsonian effective action actions of such theories. In particular, we analyze the case of Gaiotto theories, which provide a large number of non-trivial examples in a unified framework. We then turn to understanding the massive BPS spectrum of such theories, and in particular their relation to BPS quivers. We present a purely 4d characterization of BPS quivers, and explain how a quiver's representation theory encodes the solution to the BPS occupancy problem. Next, we derive a so called mutation method, based on exploiting quiver dualities, to solve the quiver's representation theory. This method makes previously intractable calculations nearly trivial in many examples. As a particular highlight, we apply our methods to understand strongly coupled chambers in ADE SYM gauge theories with matter. Following this, we turn to the general story of quivers for theories of the Gaiotto class. We present a geometric approach to attaining quivers for the rank 2 theories, leading to a very elegant solution which includes a specification of quiver superpotentials. Finally, we solve these theories by an unrelated method based on gauging flavor symmetries in their various dual weakly coupled Lagrangian descriptions. After seeing that this method agrees in the rank 2 case, we will apply our new approach to the case of rank n.

  3. Photoionization dynamics of pure helium droplets: exciton formation vs autoionization

    NASA Astrophysics Data System (ADS)

    Kornilov, Oleg; Gessner, Oliver; Buennermann, Oliver; Wang, Chia; Leone, Steve; Neumark, Daniel

    2010-03-01

    ^4He droplets possess unique properties. In addition to fundamental quantum effects of superfluidity the droplets show ability to efficiently pick-up foreign atoms, molecules and complexes, which is used in a number of matrix isolation spectroscopies in energy domain. Complementary to these studies, novel time-domain experiments will be presented emphasizing dynamics of photoionization of pure helium droplets. The experiments follow up on a recent observation of ultraslow (E<1 meV) photoelectrons emitted from droplets upon ionization by synchrotron radiation. The dynamics of photoionization is studied by exciting droplets with a pulsed VUV radiation generated using the high-order harmonic generation technique. The droplets subsequently interact with an IR pulse, which probes transient electronic states before droplet autoionization. Femtosecond and picosecond relaxation dynamics and competition between droplet ionization and formation of a long-lived excited state are observed. Probe pulse leads to droplet ``re-excitation'' and production of even more ultraslow electrons. The results will be extended to doped droplets anticipating indirect dopant ionization dynamics.

  4. 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.

  5. Valence-electron correlation in the double K -shell photoionization of atomic beryllium

    NASA Astrophysics Data System (ADS)

    Saha, Hari P.

    2017-06-01

    We extended the multiconfiguration Hartree-Fock (MCHF) + effective charge (EFC) method for double photoionization of atoms and investigated the effect of valence-electron correlation in the double K -shell photoionization of atomic beryllium. We used the MCHF method, which accounts for electron correlations, to calculate the initial-state wave function. The wave functions for the two continuum electrons in the final state are calculated in the angle-dependent EFC approximation. The actual interaction potential between the two final-state continuum electrons is approximated by the EFC, which is determined variationally. We studied the effect of valence shell electron correlation on the K -shell double photoionization of beryllium for both equal and unequal sharing of excess photon energies at four fixed scattered electron directions in order to study the effects near the double K -shell ionization threshold. We found considerable effect of valence shell correlation in the triple-differential cross section for double photoionization of the beryllium atom at each of the excess photon energies.

  6. Double K-shell photoionization and hypersatellite x-ray transitions of 12{<=}Z{<=}23 atoms

    SciTech Connect

    Hoszowska, J.; Dousse, J.-Cl.; Cao, W.; Fennane, K.; Kayser, Y.; Szlachetko, M.; Szlachetko, J.; Kavcic, M.

    2010-12-15

    Single-photon double K-shell ionization of low-Z neutral atoms in the range 12{<=}Z{<=}23 is investigated. The experimental method was based on measurements of the high-resolution K{alpha}{sup h} hypersatellite x-ray spectra following the radiative decay of the K-shell double-vacancy states excited by monochromatic synchrotron radiation. The photon energy dependence of the double K-shell ionization was measured over a wide range of photon energies from threshold up to and beyond the maximum of the double-to-single photoionization cross section ratios. From the high-resolution x-ray emission spectra the energies and linewidths of the hypersatellite transitions, as well as the K{alpha}{sub 1}{sup h}:K{alpha}{sub 2}{sup h} intensity ratios, were determined. The relative importance of the initial-state and final-state electron-electron interactions to the K-shell double photoionization is addressed. Physical mechanisms and scaling laws of the K-shell double photoionization are examined. A semiempirical universal scaling of the double-photoionization cross sections with the effective nuclear charge for neutral atoms in the range 2{<=}Z{<=}47 is established.

  7. Analysis of 4D Var Data Assimilation Application Issues

    NASA Astrophysics Data System (ADS)

    Trailovic, L.; Etherton, B.; Harrop, C.; Govett, M.

    2016-12-01

    This paper summarizes the challenges encountered with our ongoing development and use of a software system designed to facilitate exploration of computational optimizations and strategies for Data Assimilation (DA). The software system is designed and constructed from scratch using modern software development methods and tools, though it incorporates components of pre-existing systems where appropriate. We present results of experiments that employ this system to test approaches for assimilation of observations using a four-dimensional variational (4D Var) scheme. We propose a modular DA system software architecture and demonstrate its utility using a set of models of varying realism and complexity. The software system design and implementation was initially tested and validated using a simple chaotic atmospheric model. A Quasi-Geostrophic (QG) atmospheric model was used to conduct DA experiments of increased difficulty and to validate the software design at larger scales of model complexity. Our QG DA study focused on 2016 winter weather data where a Nature run was used to represent the "true" state of the atmosphere and observations, whereas observation error covariance and observation operator were adapted from pre-existing DA systems. To increase performance, a parallel-in-time algorithm was applied to solve the proposed 4D Var data assimilation problem. That is, the assimilation window was divided into multiple sub-intervals, which allowed for parallelization of the cost function and gradient computations. Continuity equations of the solution were added as constraints across interval boundaries. This approach produced a different formulation of the variational data assimilation problem than weakly constrained 4D Var. We explored a combination of serial and parallel 4D Var algorithms to increase performance.

  8. Photoionizing Trapped Highly Charged Ions with Synchrotron Radiation

    SciTech Connect

    Crespo, J R; Simon, M; Beilmann, C; Rudolph, J; Steinbruegge, R; Eberle, S; Schwarz, M; Baumann, T; Schmitt, B; Brunner, F; Ginzel, R; Klawitter, R; Kubicek, K; Epp, S; Mokler, P; Maeckel, V; Ullrich, J; Brown, G V; Graf, A; Leutenegger, M; Beiersdorfer, P; Behar, E; Follath, R; Reichardt, G; Schwarzkopf, O

    2011-09-12

    Photoabsorption by highly charged ions plays an essential role in astrophysical plasmas. Diagnostics of photoionized plasmas surrounding binary systems rely heavily on precise identification of absorption lines and on the knowledge of their cross sections and widths. Novel experiments using an electron beam ion trap, FLASH EBIT, in combination with monochromatic synchrotron radiation allow us to investigate ions in charge states hitherto out of reach. Trapped ions can be prepared in any charge state at target densities sufficient to measure absorption cross sections below 0.1 Mb. The results benchmark state-of-the-art predictions of the transitions wavelengths, widths, and absolute cross sections. Recent high resolution results on Fe{sup 14+}, Fe{sup 15+}, and Ar{sup 12+} at photon energies up to 1 keV are presented.

  9. 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.

  10. Controlled Source 4D Seismic Imaging

    NASA Astrophysics Data System (ADS)

    Luo, Y.; Morency, C.; Tromp, J.

    2009-12-01

    Earth's material properties may change after significant tectonic events, e.g., volcanic eruptions, earthquake ruptures, landslides, and hydrocarbon migration. While many studies focus on how to interpret observations in terms of changes in wavespeeds and attenuation, the oil industry is more interested in how we can identify and locate such temporal changes using seismic waves generated by controlled sources. 4D seismic analysis is indeed an important tool to monitor fluid movement in hydrocarbon reservoirs during production, improving fields management. Classic 4D seismic imaging involves comparing images obtained from two subsequent seismic surveys. Differences between the two images tell us where temporal changes occurred. However, when the temporal changes are small, it may be quite hard to reliably identify and characterize the differences between the two images. We propose to back-project residual seismograms between two subsequent surveys using adjoint methods, which results in images highlighting temporal changes. We use the SEG/EAGE salt dome model to illustrate our approach. In two subsequent surveys, the wavespeeds and density within a target region are changed, mimicking possible fluid migration. Due to changes in material properties induced by fluid migration, seismograms recorded in the two surveys differ. By back propagating these residuals, the adjoint images identify the location of the affected region. An important issue involves the nature of model. For instance, are we characterizing only changes in wavespeed, or do we also consider density and attenuation? How many model parameters characterize the model, e.g., is our model isotropic or anisotropic? Is acoustic wave propagation accurate enough or do we need to consider elastic or poroelastic effects? We will investigate how imaging strategies based upon acoustic, elastic and poroelastic simulations affect our imaging capabilities.

  11. Photoionization and Dissociative Photoionization Study of Cholesterol by IR Laser Desorption/Tunable Synchrotron VUV Photoionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Pan, Yang; Zhang, Li-dong; Guo, Hui-jun; Yin, Hao; Qi, Fei

    2009-04-01

    Elementary cholesterol was analyzed with IR laser desorption/tunable synchrotron vacuum ultraviolet photoionization mass spectrometry. An exclusive molecular ion of cholesterol is observed by near threshold single-photon ionization with high efficiency. Fragments are yielded with the increase of photon energy. The structures of various fragments are determined with commercial electron ionization time-of-flight mass spectrometry. Dominant fragmentation pathways are discussed in detail with the aid of ab initio calculations.

  12. 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.

  13. Photoionization of the hydrogen atom in strong magnetic fields

    NASA Technical Reports Server (NTRS)

    Potekhin, Aleksandr IU.; Pavlov, George G.

    1993-01-01

    The photoionization of the hydrogen atom in magnetic fields B about 10 exp 11 - 10 exp 13 G typical of the surface layers of neutron stars is investigated analytically and numerically. We consider the photoionization from various tightly bound and hydrogen-like states of the atom for photons with arbitrary polarizations and wave-vector directions. It is shown that the length form of the interaction matrix elements is more appropriate in the adiabatic approximation than the velocity form, at least in the most important frequency range omega much less than omega(B), where omega(B) is the electron cyclotron frequency. Use of the length form yields nonzero cross sections for photon polarizations perpendicular to the magnetic field at omega less than omega(B); these cross sections are the ones that most strongly affect the properties of the radiation escaping from an optically thick medium, e.g., from the atmosphere of a neutron star. The results of the numerical calculations are fitted by simple analytical formulas.

  14. Laser isotope separation of lithium by two-step photoionization

    SciTech Connect

    Saleem, M.; Hussain, Shahid; Rafiq, M.; Baig, M. A.

    2006-09-01

    Lithium isotope separation has been achieved employing the two-step photoionization technique along with a narrow band dye laser in conjunction with a time of flight mass spectrometer. The demonstrated method yields a high degree of selectivity by tuning the dye laser at the resonance levels of Li{sup 6} and Li{sup 7}. It is inferred that the concentration of the natural abundance of the Li{sup 6} isotope gets enhanced up to over 47% as the exciter dye laser is tuned to the {sup 2}P{sub 1/2} of Li{sup 6} even if the linewidth of the exciter laser is not sufficiently narrow to excite the isotopic level. It is also noticed that the much higher energy density of the exciter laser limits the resolution of the fine structure levels of the lithium isotopes that leads to a loss in the enrichment of Li{sup 6} due to the power-broadening effect. Measurements of the photoionization cross section of the lithium isotopes from the 2p {sup 2}P{sub 1/2,3/2}, excited states for Li{sup 6} and Li{sup 7} and the corresponding number densities are reported.

  15. Design of laboratory experiments to study photoionization fronts

    NASA Astrophysics Data System (ADS)

    Drake, R. P.; Hazak, G.; Keiter, P. A.; Davis, J. S.; Patterson, C. R.; Frank, A.; Blackman, E.; Busquet, M.

    2016-10-01

    This paper analyzes the requirements of a photoionization-front experiment that could be driven in the laboratory, using thermal sources to produce the necessary flux of ionizing photons. It reports several associated conclusions. Such experiments will need to employ the largest available facilities, capable of delivering many kJ to MJ of energy to an x-ray source. They will use this source to irradiate a volume of neutral gas, likely of N, on a scale of a few mm to a few cm, increasing with source energy. For a gas pressure of several to ten atmospheres at room temperature, and a source temperature near 100 eV, one will be able to drive a photoionization front through a system of tens to hundreds of photon mean free paths. The front should make the familiar transition from the so-called R-Type to D-Type as the radiation flux diminishes with distance. The N is likely to reach the He-like state. Preheating from the energetic photons appears unlikely to become large enough to alter the essential dynamics of the front beyond some layer near the surface. For well-chosen experimental conditions, competing energy transport mechanisms are small. Supported by the U.S. DOE by NNSA Grants DE-NA0002956 (SSAA) and DE-NA0002719 (NLUF), by LLE, and by LLNL.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. Emission spectra of photoionized plasmas induced by intense EUV pulses: Experimental and theoretical investigations

    NASA Astrophysics Data System (ADS)

    Saber, Ismail; Bartnik, Andrzej; Skrzeczanowski, Wojciech; Wachulak, Przemysław; Jarocki, Roman; Fiedorowicz, Henryk

    2017-03-01

    Experimental measurements and numerical modeling of emission spectra in photoionized plasma in the ultraviolet and visible light (UV/Vis) range for noble gases have been investigated. The photoionized plasmas were created using laser-produced plasma (LPP) extreme ultraviolet (EUV) source. The source was based on a gas puff target; irradiated with 10ns/10J/10Hz Nd:YAG laser. The EUV radiation pulses were collected and focused using grazing incidence multifoil EUV collector. The laser pulses were focused on a gas stream, injected into a vacuum chamber synchronously with the EUV pulses. Irradiation of gases resulted in a formation of low temperature photoionized plasmas emitting radiation in the UV/Vis spectral range. Atomic photoionized plasmas produced this way consisted of atomic and ionic with various ionization states. The most dominated observed spectral lines originated from radiative transitions in singly charged ions. To assist in a theoretical interpretation of the measured spectra, an atomic code based on Cowan's programs and a collisional-radiative PrismSPECT code have been used to calculate the theoretical spectra. A comparison of the calculated spectral lines with experimentally obtained results is presented. Electron temperature in plasma is estimated using the Boltzmann plot method, by an assumption that a local thermodynamic equilibrium (LTE) condition in the plasma is validated in the first few ionization states. A brief discussion for the measured and computed spectra is given.

  1. 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.

  2. Photoionization of atomic hydrogen in electric field

    SciTech Connect

    Gorlov, Timofey V; Danilov, Viatcheslav V

    2010-01-01

    Laser assisted ionization of high energy hydrogen beams in magnetic fields opens wide application possibilities in accelerator physics and other fields. The key theoretical problem of the method is the calculation of the ionization probability of a hydrogen atom affected by laser and static electric fields in the particle rest frame. A method of solving this problem with the temporal Schr dinger equation including a continuum spectrum is presented in this paper in accurate form for the first time. This method allows finding the temporal evolution of the wave function of the hydrogen atom as a function of laser and static electric fields. Solving the problem of photoionization reveals quantum effects that cannot be described by the cross sectional approach. The effects play a key role in the problems of photoionization of H0 beams with the large angular or energy spread.

  3. 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…

  4. 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…

  5. Intermanifold similarities in partial photoionization cross sections of helium

    NASA Astrophysics Data System (ADS)

    Schneider, Tobias; Liu, Chien-Nan; Rost, Jan-Michael

    2002-04-01

    Using the eigenchannel R-matrix method we calculate partial photoionization cross sections from the ground state of the helium atom for incident photon energies up to the N=9 manifold. The wide energy range covered by our calculations permits a thorough investigation of general patterns in the cross sections which were first discussed by Menzel and coworkers [Phys. Rev. A 54, 2080 (1996)]. The existence of these patterns can easily be understood in terms of propensity rules for autoionization. As the photon energy is increased the regular patterns are locally interrupted by perturber states until they fade out indicating the progressive breakdown of the propensity rules and the underlying approximate quantum numbers. We demonstrate that the destructive influence of isolated perturbers can be compensated with an energy-dependent quantum defect.

  6. Spatiotemporal directional analysis of 4D echocardiography

    NASA Astrophysics Data System (ADS)

    Angelini-Casadevall, Elsa D.; Laine, Andrew F.; Takuma, Shin; Homma, Shunichi

    2000-12-01

    Speckle noise corrupts ultrasonic data by introducing sharp changes in an echocardiographic image intensity profile, while attenuation alters the intensity of equally significant cardiac structures. These properties introduce inhomogeneity in the spatial domain and suggests that measures based on phase information rather than intensity are more appropriate for denoising and cardiac border detection. The present analysis method relies on the expansion of temporal ultrasonic volume data on complex exponential wavelet-like basis functions called Brushlets. These basis functions decompose a signal into distinct patterns of oriented textures. Projected coefficients are associated with distinct 'brush strokes' of a particular size and orientation. 4D overcomplete brushlet analysis is applied to temporal echocardiographic values. We show that adding the time dimension in the analysis dramatically improves the quality and robustness of the method without adding complexity in the design of a segmentation tool. We have investigated mathematical and empirical methods for identifying the most 'efficient' brush stroke sizes and orientations for decomposition and reconstruction on both phantom and clinical data. In order to determine the 'best tiling' or equivalently, the 'best brushlet basis', we use an entorpy-based information cost metric function. Quantitative validation and clinical applications of this new spatio-temporal analysis tool are reported for balloon phantoms and clinical data sets.

  7. Photoionization Cross Section of Xe{sup +} Ion in the Pure 5p{sup 5} {sup 2}P{sub 3/2} Ground Level

    SciTech Connect

    Thissen, R.; Bizau, J. M.; Blancard, C.; Coreno, M.; Franceschi, P.; Giuliani, A.; Nicolas, C.

    2008-06-06

    Coupling an ion trap with synchrotron radiation is shown here to be a powerful approach to measure photoionization cross sections on ionic species relaxed in their ground state. The photoionization efficiency curve of Xe{sup +} ions stored in a Fourier transform ion cyclotron resonance ion trap was recorded at ELETTRA in the 20-23 eV photon energy range. Absolute cross sections were derived by comparison of the photoionization yield of Xe{sup +} with measurements from the ASTRID merged-beam experiment. Multiconfiguration Dirac-Fock calculations were performed for the interpretation of these new data.

  8. Positive energy conditions in 4D conformal field theory

    DOE PAGES

    Farnsworth, Kara; Luty, Markus A.; Prilepina, Valentina

    2016-10-03

    Here, we argue that all consistent 4D quantum field theories obey a spacetime-averaged weak energy inequality < T00 > ≥ –C/L4, where L is the size of the smearing region, and C is a positive constant that depends on the theory. If this condition is violated, the theory has states that are indistinguishable from states of negative total energy by any local measurement, and we expect instabilities or other inconsistencies. We apply this condition to 4D conformal field theories, and find that it places constraints on the OPE coefficients of the theory. The constraints we find are weaker than themore » “conformal collider” constraints of Hofman and Maldacena. In 3D CFTs, the only constraint we find is equivalent to the positivity of 2-point function of the energy-momentum tensor, which follows from unitarity. Our calculations are performed using momentum-space Wightman functions, which are remarkably simple functions of momenta, and may be of interest in their own right.« less

  9. Positive energy conditions in 4D conformal field theory

    SciTech Connect

    Farnsworth, Kara; Luty, Markus A.; Prilepina, Valentina

    2016-10-03

    Here, we argue that all consistent 4D quantum field theories obey a spacetime-averaged weak energy inequality < T00 > ≥ –C/L4, where L is the size of the smearing region, and C is a positive constant that depends on the theory. If this condition is violated, the theory has states that are indistinguishable from states of negative total energy by any local measurement, and we expect instabilities or other inconsistencies. We apply this condition to 4D conformal field theories, and find that it places constraints on the OPE coefficients of the theory. The constraints we find are weaker than the “conformal collider” constraints of Hofman and Maldacena. In 3D CFTs, the only constraint we find is equivalent to the positivity of 2-point function of the energy-momentum tensor, which follows from unitarity. Our calculations are performed using momentum-space Wightman functions, which are remarkably simple functions of momenta, and may be of interest in their own right.

  10. Positive Energy Conditions in 4D Conformal Field Theory

    NASA Astrophysics Data System (ADS)

    Farnsworth, Kara; Luty, Markus; Prilepina, Valentina

    2016-03-01

    We argue that all consistent 4D quantum field theories obey a spacetime-averaged weak energy inequality avgT00 >= - C /L4 , where L is the size of the smearing region, and C is a positive constant that depends on the theory. If this condition is violated, the theory has states that are indistinguishable from states of negative total energy by any local measurement, and we expect instabilities or other inconsistencies. We apply this condition to 4D conformal field theories, and find that it places constraints on the OPE coefficients of the theory. The constraints we find are weaker than the ``conformal collider'' constraints of Hofman and Maldacena. We speculate that there may be theories that violate the Hofman-Maldacena bounds, but satisfy our bounds. In 3D CFTs, the only constraint we find is equivalent to the positivity of 2-point function of the energy-momentum tensor, which follows from unitarity. Our calculations are performed using momentum-space Wightman functions, which are remarkably simple functions of momenta, and may be of interest in their own right.

  11. Positive energy conditions in 4D conformal field theory

    NASA Astrophysics Data System (ADS)

    Farnsworth, Kara; Luty, Markus A.; Prilepina, Valentina

    2016-10-01

    We argue that all consistent 4D quantum field theories obey a spacetime-averaged weak energy inequality < T 00> ≥ - C/L 4, where L is the size of the smearing region, and C is a positive constant that depends on the theory. If this condition is violated, the theory has states that are indistinguishable from states of negative total energy by any local measurement, and we expect instabilities or other inconsistencies. We apply this condition to 4D conformal field theories, and find that it places constraints on the OPE coefficients of the theory. The constraints we find are weaker than the "conformal collider" constraints of Hofman and Maldacena. In 3D CFTs, the only constraint we find is equivalent to the positivity of 2-point function of the energy-momentum tensor, which follows from unitarity. Our calculations are performed using momentum-space Wightman functions, which are remarkably simple functions of momenta, and may be of interest in their own right.

  12. Excitation energies, photoionization cross sections, and asymmetry parameters of the methyl and silyl radicals

    SciTech Connect

    Velasco, A. M.; Lavín, C.; Dolgounitcheva, O.; Ortiz, J. V.

    2014-08-21

    Vertical excitation energies of the methyl and silyl radicals were inferred from ab initio electron propagator calculations on the electron affinities of CH{sub 3}{sup +} and SiH{sub 3}{sup +}. Photoionization cross sections and angular distribution of photoelectrons for the outermost orbitals of both CH{sub 3} and SiH{sub 3} radicals have been obtained with the Molecular Quantum Defect Orbital method. The individual ionization cross sections corresponding to the Rydberg channels to which the excitation of the ground state's outermost electron gives rise are reported. Despite the relevance of methyl radical in atmospheric chemistry and combustion processes, only data for the photon energy range of 10–11 eV seem to be available. Good agreement has been found with experiment for photoionization cross section of this radical. To our knowledge, predictions of the above mentioned photoionization parameters on silyl radical are made here for the first time, and we are not aware of any reported experimental measurements. An analysis of our results reveals the presence of a Cooper minimum in the photoionization of the silyl radical. The adequacy of the two theoretical procedures employed in the present work is discussed.

  13. Electron correlations in the L-shell photoionization of heavy elements

    NASA Astrophysics Data System (ADS)

    Jitschin, W.; Werner, U.; Materlik, G.; Doolen, G. D.

    1987-06-01

    The photoionization of the individual L subshells of 72Hf, 74W, 78Pt, 79Au, and 82Pb in the energy regime of the L edges has been studied in detail. Experimentally, the x-ray absorption spectra of thin sample foils were recorded using monochromatized synchrotron radiation. The energy dependence of the absorption is governed in its gross structure by the atomic photoionization with some superimposed oscillatory structure due to solid-state effects. The experimental data are compared to various theoretical predictions for atomic photoionization. Calculations in the framework of an independent-electron approach predict a smooth, power-law-like energy dependence. In contrast, the experimental data show small but significant deviations from such a behavior. The dispersionlike deviations are attributed to electron-correlation effects, as is confirmed by comparative calculations of photoionization with inclusion or omission of the correlations using the computer code of Liberman and Zangwill [Comput. Phys. Commun. 32, 75 (1984)]. The main influence of the correlation effects on the subshell ionization cross sections originates from the dielectric (anti-) screening of the external radiation field. Calculations in the local-density approximation for the response of the atom to the radiation field yield an even quantitative description of the experimental data in a large fraction of the investigated energy range.

  14. 17 CFR 260.4d-8 - Content.

    Code of Federal Regulations, 2010 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)...

  15. 17 CFR 260.4d-8 - Content.

    Code of Federal Regulations, 2010 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)...

  16. 17 CFR 260.4d-8 - Content.

    Code of Federal Regulations, 2010 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)...

  17. 17 CFR 260.4d-8 - Content.

    Code of Federal Regulations, 2010 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)...

  18. Relative Photoionization Cross Sections of Super-Atom Molecular Orbitals (SAMOs) in C60.

    PubMed

    Bohl, Elvira; Sokół, Katarzyna P; Mignolet, Benoit; Thompson, James O F; Johansson, J Olof; Remacle, Francoise; Campbell, Eleanor E B

    2015-11-25

    The electronic structure and photoinduced dynamics of fullerenes, especially C60, is of great interest because these molecules are model systems for more complex molecules and nanomaterials. In this work we have used Rydberg Fingerprint Spectroscopy to determine the relative ionization intensities from excited SAMO (Rydberg-like) states in C60 as a function of laser wavelength. The relative ionization intensities are then compared to the ratio of the photoionization widths of the Rydberg-like states, computed in time-dependent density functional theory (TD-DFT). The agreement is remarkably good when the same photon order is required to energetically access the excited states. This illustrates the predictive potential of quantum chemistry for studying photoionization of large, complex molecules as well as confirming the assumption that is often made concerning the multiphoton excitation and rapid energy redistribution in the fullerenes.

  19. 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.

  20. Absolute single photoionization cross-section measurements of Rb2+ ions: experiment and theory

    NASA Astrophysics Data System (ADS)

    Macaluso, D. A.; Bogolub, K.; Johnson, A.; Aguilar, A.; Kilcoyne, A. L. D.; Bilodeau, R. C.; Bautista, M.; Kerlin, A. B.; Sterling, N. C.

    2016-12-01

    Absolute single photoionization cross-section measurements of Rb2+ ions were performed using synchrotron radiation and the photo-ion, merged-beams technique at the Advanced Light Source at Lawrence Berkeley National Laboratory. Measurements were made at a photon energy resolution of 13.5 ± 2.5 meV from 37.31 to 44.08 eV spanning the 2P{}3/2o ground state and 2P{}1/2o metastable state ionization thresholds. Multiple autoionizing resonance series arising from each initial state are identified using quantum defect theory. The measurements are compared to Breit-Pauli R-matrix calculations with excellent agreement between theory and experiment.

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

    DOE PAGES

    Mazza, T.; Karamatskou, A.; Ilchen, M.; ...

    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. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

    2015-04-01

    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.

  5. 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

    2015-04-09

    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.

  6. Photoionization and photoelectric loading of barium ion traps

    SciTech Connect

    Steele, A. V.; Churchill, L. R.; Griffin, P. F.; Chapman, M. S.

    2007-05-15

    Simple and effective techniques for loading barium ions into linear Paul traps are demonstrated. Two-step photoionization of neutral barium is achieved using a weak intercombination line (6s{sup 2} {sup 1}S{sub 0}{r_reversible}6s6p {sup 3}P{sub 1}, {lambda}=791 nm) followed by excitation above the ionization threshold using a nitrogen gas laser ({lambda}=337 nm). Isotopic selectivity is achieved by using a near Doppler-free geometry for excitation of the triplet 6s6p {sup 3}P{sub 1} state. Additionally, we report a particularly simple and efficient trap loading technique that employs an inexpensive uv epoxy curing lamp to generate photoelectrons.

  7. Cancer Incidence of 2,4-D Production Workers

    PubMed Central

    Burns, Carol; Bodner, Kenneth; Swaen, Gerard; Collins, James; Beard, Kathy; Lee, Marcia

    2011-01-01

    Despite showing no evidence of carcinogenicity in laboratory animals, the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has been associated with non-Hodgkin lymphoma (NHL) in some human epidemiology studies, albeit inconsistently. We matched an existing cohort of 2,4-D manufacturing employees with cancer registries in three US states resulting in 244 cancers compared to 276 expected cases. The Standardized Incidence Ratio (SIR) for the 14 NHL cases was 1.36 (95% Confidence Interval (CI) 0.74–2.29). Risk estimates were higher in the upper cumulative exposure and duration subgroups, yet not statistically significant. There were no clear patterns of NHL risk with period of hire and histology subtypes. Statistically significant results were observed for prostate cancer (SIR = 0.74, 95% CI 0.57–0.94), and “other respiratory” cancers (SIR = 3.79, 95% CI 1.22–8.84; 4 of 5 cases were mesotheliomas). Overall, we observed fewer cancer cases than expected, and a non statistically significant increase in the number of NHL cases. PMID:22016704

  8. 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.

  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. Auger decay of 4 d inner-shell holes in atomic Hg leading to triple ionization

    NASA Astrophysics Data System (ADS)

    Andersson, J.; Beerwerth, R.; Roos, A. Hult; Squibb, R. J.; Singh, R.; Zagorodskikh, S.; Talaee, O.; Koulentianos, D.; Eland, J. H. D.; Fritzsche, S.; Feifel, R.

    2017-07-01

    Formation of triply ionized states upon the creation of 4 d inner-shell holes in atomic Hg is investigated by using synchrotron radiation of 730 eV photon energy and a versatile multielectron coincidence detection technique in combination with multiconfiguration Dirac-Fock calculations. By carefully selecting Coster-Kronig electrons detected only in coincidence with a 4 d photoelectron, the Coster-Kronig spectrum has been extracted and the corresponding branching ratios of the 4 d hole have been determined. The results are found to differ from previously established experimental ratios based on electron impact ionization but to agree now better with theory. We also present an Auger cascade analysis of pathways leading to triply ionized states of atomic Hg upon removal of a 4 d inner-shell electron.

  11. Complete characterization of double photoionization processes

    NASA Astrophysics Data System (ADS)

    Ivanov, I. A.; Kheifets, A. S.

    2011-06-01

    We analyze correlated photoelectron spectra of single-photon two-electron ionization [double photoionization (DPI)] of helium to reconstruct the phase of the spectral amplitude of this process. The phase can be reconstructed reliably in a wide range of photoelectron momenta, thus allowing one to retrieve information about the wave function of the DPI process and its temporal evolution. Our simulation indicates that the proposed phase reconstruction technique can be applied in experiment to trace dynamics of the DPI process with attosecond precision.

  12. Spin effects in double photoionization of lithium

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

    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.

  13. 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.

  14. Complete characterization of double photoionization processes

    SciTech Connect

    Ivanov, I. A.; Kheifets, A. S.

    2011-06-15

    We analyze correlated photoelectron spectra of single-photon two-electron ionization [double photoionization (DPI)] of helium to reconstruct the phase of the spectral amplitude of this process. The phase can be reconstructed reliably in a wide range of photoelectron momenta, thus allowing one to retrieve information about the wave function of the DPI process and its temporal evolution. Our simulation indicates that the proposed phase reconstruction technique can be applied in experiment to trace dynamics of the DPI process with attosecond precision.

  15. K-shell photoionization cross-sections.

    NASA Technical Reports Server (NTRS)

    Daltabuit, E.; Cox, D. P.

    1972-01-01

    Approximate values for the threshold energies, threshold cross sections, and energy dependence of the cross sections for K-shell photoionization are tabulated for H, He, C, N, O, Ne, Mg, Si, and S in all stages of ionization. The approximation of these data is based on the assumptions that the threshold energy is a simple function of the nuclear charge and the number of electrons present in the atom, and that the threshold values and energy dependence of the cross sections are determined only by the threshold energy.

  16. Atomic photoionization experiment by harmonic-generation spectroscopy

    NASA Astrophysics Data System (ADS)

    Frolov, M. V.; Sarantseva, T. S.; Manakov, N. L.; Fulfer, K. D.; Wilson, B. P.; Troß, J.; Ren, X.; Poliakoff, E. D.; Silaev, A. A.; Vvedenskii, N. V.; Starace, Anthony F.; Trallero-Herrero, C. A.

    2016-03-01

    Measurements of the high-order-harmonic generation yield of the argon (Ar) atom driven by a strong elliptically polarized laser field are shown to completely determine the field-free differential photoionization cross section of Ar, i.e., the energy dependence of both the angle-integrated photoionization cross section and the angular distribution asymmetry parameter.

  17. Calculated photoionization cross sections using Quantemol-N

    NASA Astrophysics Data System (ADS)

    Brigg, Will J.; Harvey, Alex G.; Dzarasova, Anna; Mohr, Sebastian; Brambila, Danilo S.; Morales, Felipe; Smirnova, Olga; Tennyson, Jonathan

    2015-06-01

    Quantemol-N is an expert system designed to run the widely used UK Molecular R-matrix code (UKRMol). Originally designed to consider electron-molecule collision problems, here we present an extension to treat molecular photoionization. Sample results are given for the photoionization of molecular nitrogen and methane. Comparisons are made with experimental results showing good agreement.

  18. Holography and Emergent 4d Gravity

    NASA Astrophysics Data System (ADS)

    Nitti, Francesco

    We review recent work toward constructing, via five-dimensional holographic duals, four-dimensional theories in which spin-2 states (gravitons) are emergent. The basic idea is to extend to gravity model-building the applications of holographic duality to phenomenology construction.

  19. Determining the partial photoionization cross-sections of ethyl radicals.

    PubMed

    FitzPatrick, B L; Maienschein-Cline, M; Butler, L J; Lee, S-H; Lin, J J

    2007-12-13

    Using a crossed laser-molecular beam scattering apparatus, these experiments photodissociate ethyl chloride at 193 nm and detect the Cl and ethyl products, resolved by their center-of-mass recoil velocities, with vacuum ultraviolet photoionization. The data determine the relative partial cross-sections for the photoionization of ethyl radicals to form C2H5+, C2H4+, and C2H3+ at 12.1 and 13.8 eV. The data also determine the internal energy distribution of the ethyl radical prior to photoionization, so we can assess the internal energy dependence of the photoionization cross-sections. The results show that the C2H4++H and C2H3++H2 dissociative photoionization cross-sections strongly depend on the photoionization energy. Calibrating the ethyl radical partial photoionization cross-sections relative to the bandwidth-averaged photoionization cross-section of Cl atoms near 13.8 eV allows us to use these data in conjunction with literature estimates of the Cl atom photoionization cross-sections to put the present bandwidth-averaged cross-sections on an absolute scale. The resulting bandwidth-averaged cross-section for the photoionization of ethyl radicals to C2H5+ near 13.8 eV is 8+/-2 Mb. Comparison of our 12.1 eV data with high-resolution ethyl radical photoionization spectra allows us to roughly put the high-resolution spectrum on the same absolute scale. Thus, one obtains the photoionization cross-section of ethyl radicals to C2H5+ from threshold to 12.1 eV. The data show that the onset of the C2H4++H dissociative photoionization channel is above 12.1 eV; this result offers a simple way to determine whether the signal observed in photoionization experiments on complex mixtures is due to ethyl radicals. We discuss an application of the results for resolving the product branching in the O+allyl bimolecular reaction.

  20. 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.

  1. 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.

  2. 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

  3. High-intensity photoionization of H sub 2

    SciTech Connect

    Allendorf, S.W.; Szoeke, A.

    1991-05-01

    A tunable, high-intensity picosecond dye laser system has been employed with electron energy analysis to investigate the dynamics of (3+1) resonance-enhanced multiphoton ionization of H{sub 2} via different vibrational levels of its B{sub 1}{Sigma}{sub u}{sup +} and C{sup 1}{Pi}{sub u} electronic states. We observe production of molecular ions in various vibrational levels, with a shift to increased population of lower vibrational states of H{sub 2}{sup +} consistent with the a.c. Stark shift of the correspondingly lower vibrational levels of the C state into resonance with the three- photon energy of the laser. Clear evidence of direct dissociation of H{sub 2} followed by single-photon ionization of the excited H atom is observed as well. Above threshold ionization of these two processes occurs readily. We also find that dissociative ionization is an increasingly important ionization pathway as the wavelength is increased. Finally, we see evidence of a new ionization pathway, which we assign to photoionization into a transient bound state created by the avoided crossing of the first repulsive electronic state of H{sub 2}{sup +}, {vert bar}2p{sigma}{sub u}, n{r angle}, with the single-photon-dressed ground state of H{sub 2}{sup +}, {vert bar}1s{sigma}{sub g},n + 1{r angle}. 6 refs., 2 figs.

  4. Deformable registration of 4D computed tomography data.

    PubMed

    Rietzel, Eike; Chen, George T Y

    2006-11-01

    Four-dimensional radiotherapy requires deformable registration to track delivered dose across varying anatomical states. Deformable registration based on B-splines was implemented to register 4D computed tomography data to a reference respiratory phase. To assess registration performance, anatomical landmarks were selected across ten respiratory phases in five patients. These point landmarks were transformed according to global registration parameters between different respiratory phases. Registration uncertainties were computed by subtraction of transformed and reference landmark positions. The selection of appropriate registration masks to separate independently moving anatomical subunits is crucial to registration performance. The average registration error for five landmarks for each of five patients was 2.1 mm. This level of accuracy is acceptable for most radiotherapy applications.

  5. Using vibrational branching ratios to probe shape resonances in molecular photoionization

    NASA Astrophysics Data System (ADS)

    Lucchese, Robert; Das, Aloke; Poliakoff, Erwin; Bozek, John

    2009-05-01

    The measurement of vibrational branching ratios in molecular photoionization can be used as a probe of the nature of resonant states, since such states are often sensitive to the geometry of the molecule. Recent computed results for BF3 and C6F6 will be presented. In C6F6, we consider the excitation of the two symmetric stretching modes in the photoionization leading to the C ^3B2u state of the ion. Two prominent shape resonances at photon energies between 18 and 20 eV respond quite differently to the excitation of the symmetric ring-breathing mode and to the symmetric C-F stretching mode. In BF3, the excitation of both the symmetric stretching and the degenerate asymmetric stretching modes are considered in the photoionization leading to the E ^2A1' state of the ion. The symmetric stretching mode shows a relatively weak resonant enhancement in the branching ratio, whereas the asymmetric stretching mode has a much more prominent feature.

  6. Relativistic R-Matrix Close-Coupling Calculations for Photoionization of Si-Like Ni XV

    NASA Astrophysics Data System (ADS)

    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 23p 2(3 P 0) and the lowest four 3s 23p 2 (3 P 1,2, 1 D 2, 1 S 0) excited states. A multiconfiguration eigenfunction expansion of the core Ni XVI is employed with configurations 3s 23p, 3s3p 2, 3s 23d, 3p 3, 3s3p3d, 3p 23d, 3s3d 2, 3p3d 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.

  7. 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.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

    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.

  10. Identification and Chemistry of Phenylnitrene in Premixed Pyridine/Oxygen/Argon Flame with Tunable Synchrotron Photoionization

    NASA Astrophysics Data System (ADS)

    Tian, Zhen-yu; Yuan, Tao; Wang, Jing; Li, Yu-yang; Zhang, Tai-chang; Zhu, Ai-guo; Qi, Fei

    2007-08-01

    The triplet state phenylnitrene (PhN) species generated from the low-pressure (4.0 kPa) premixed laminar pyridine/oxygen/argon flame was detected and identified using tunable synchrotron vacuum ultraviolet photoionization and molecular-beam mass spectrometry techniques. The ionization energies of PhN were determined experimentally by photoionization efficiency spectra and theoretically by calculations. The results indicate that PhN has a 3A2 ground state and its first and second adiabatic ionization energies are 8.04 and 9.15±0.05 eV, respectively. Furthermore, the formation and consumption pathways of PhN are proposed according to the species detected in the present work. PhN is the first nitrogen-containing diradical detected in combustion chemistry, and so it should be added to the kinetic model of pyridine flames.

  11. 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.

  12. Shining a light on galactic outflows: photoionized outflows

    NASA Astrophysics Data System (ADS)

    Chisholm, John; Tremonti, Christy A.; Leitherer, Claus; Chen, Yanmei; Wofford, Aida

    2016-04-01

    We study the ionization structure of galactic outflows in 37 nearby, star-forming galaxies with the Cosmic Origins Spectrograph on the Hubble Space Telescope. We use the O I, Si II, Si III, and Si IV ultraviolet absorption lines to characterize the different ionization states of outflowing gas. We measure the equivalent widths, line widths, and outflow velocities of the four transitions, and find shallow scaling relations between them and galactic stellar mass and star formation rate. Regardless of the ionization potential, lines of similar strength have similar velocities and line widths, indicating that the four transitions can be modelled as a comoving phase. The Si equivalent width ratios (e.g. Si IV/Si II) have low dispersion, and little variation with stellar mass; while ratios with O I and Si vary by a factor of 2 for a given stellar mass. Photoionization models reproduce these equivalent width ratios, while shock models under predict the relative amount of high ionization gas. The photoionization models constrain the ionization parameter (U) between -2.25 < log (U) < -1.5, and require that the outflow metallicities are greater than 0.5 Z⊙. We derive ionization fractions for the transitions, and show that the range of ionization parameters and stellar metallicities leads to a factor of 1.15-10 variation in the ionization fractions. Historically, mass outflow rates are calculated by converting a column density measurement from a single metal ion into a total hydrogen column density using an ionization fraction, thus mass outflow rates are sensitive to the assumed ionization structure of the outflow.

  13. Gas-Phase Photoionization Of A Protein

    NASA Astrophysics Data System (ADS)

    Milosavljevic, A. R.; Giuliani, A.; Nicolas, C.; Gil, J.-F.; Lemaire, J.; Refregiers, M.; Nahon, L.

    2010-07-01

    We present preliminary results on gas phase photoionization of electrosprayproduced multiply protonated cytochrome c protein (104 amino acids; ˜12.4 kDa), which has been achieved with a newly developed experimental system for spectroscopy of electrosprayed ions in a linear quadrupole ion trap using a monochromatized vacuum ultraviolet (VUV) synchrotron radiation and tandem mass spectrometry method. The investigation of proteins in the gas phase, where they are free of the influence of counterions and solvent molecules, offer a possibility to understand their intrinsic molecular properties. However, due to limited both ion densities and available number of photons, the use of synchrotron radiation for the trapped ions spectroscopy is a rather challenging task. The feasibility of coupling a Fourier transform ion cyclotron resonance ion trap with soft x-ray synchrotron beamline and the first successful use of synchrotron radiation for spectroscopy of electrosprayed negative ions stored in a three-dimensional quadrupole ion trap have been demonstrated only recently (R. Thissen et al., 2008, Phys. Rev. Lett., 100, 223001; A. Giulliani et al., Proc. 57th ASMS Conf., Philadelphia, 2009). The present results are the first reported on photoionization of kDa species in the gas phase and are valuable regarding both a fundamental interest of accessing physical properties of large biological ions isolated in vacuo and potential development of a new technique for proteomics.

  14. Mode specific photoionization dynamics in polyatomic molecules

    NASA Astrophysics Data System (ADS)

    Rathbone, Gerald Jeffery

    2002-11-01

    The work presented in this dissertation presents new work on polyatomic photoionization. In these investigations, the broad range behavior of both allowed and forbidden vibrational modes in linear triatomic systems were studied to understand mode specific aspects of photoionization. The current study is made possible by the experimental strategy of exploiting high resolution photoelectron spectroscopy and the high brightness of third generation synchrotron radiation sources. The data is taken typically tens of eV's past the ionization potential. The strategy that I employ is to probe alternative vibrational modes which are frequently affected differently following resonant ionization. Such vibrationally resolved data can be used to understand how the correlation between vibration and electron energy reveals microscopic insights into the photoelectron scattering process. Moreover, the mode specific behavior contains a wealth of information not only regarding allowed transitions, but also contains information on how forbidden transitions gain surprising amounts of intensity. A previously overlooked mechanism for the appearance of forbidden nontotally symmetric vibrations was discovered---resonantly amplified vibronic symmetry breaking. The photoelectron the culprit for the symmetry breaking which induces the excitation of nominally forbidden vibrational excitations. In a more general sense, these results will demonstrate that some fundamental spectroscopic approximations are not always valid, and can lead to surprising consequences.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 4f photoionization and subsequent Auger decay in atomic Pb: Relativistic effects

    SciTech Connect

    Patanen, M.; Kantia, T.; Heinaesmaeki, S.; Aksela, S.; Aksela, H.; Urpelainen, S.

    2011-05-15

    High-resolution 4f photoelectron and subsequent Auger-electron spectra have been measured from free Pb atoms using synchrotron radiation. The fine structure of the spectra has been investigated theoretically by calculating the energies and intensities for 4f photoionization and Auger decay processes using the multiconfigurational Dirac-Fock approach. The role of the relativistic effects in the ground and singly and doubly ionized states has been studied on the basis of computed results and their comparison with experiment.

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

    PubMed

    Bodi, Andras

    2013-10-14

    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.

  1. Photoionization and electrostatic multipoles properties of spherical core/shell/shell quantum nanolayer with off-center impurity

    NASA Astrophysics Data System (ADS)

    Baghdasaryan, D. A.; Kazaryan, E. M.; Sarkisyan, H. A.

    2017-04-01

    The electronic, optical and electrostatic properties of the spherical core/shell/shell quantum nanolayer with an off-centered impurity have been studied. Spherical nanolayers of both "small" and "large" radii have been considered in the framework of perturbation theory and the variational method. Photoionization cross-section that corresponds to the electron transitions from the impurity ground state to the size-quantized levels have been studied. The dependence of the photoionization cross section on the photon energy, impurity position and the geometrical parameters of the spherical nanolayer have been obtained. The electrostatic multipoles of the considered system have been investigated.

  2. A photoionization study of the formation of NO2/+/ by reaction of excited O2/+/ ions with NO

    NASA Technical Reports Server (NTRS)

    Ajello, J. M.; Rayermann, P.

    1977-01-01

    Photoionization mass spectrometer results are presented for the first observation of the ion-molecule reaction in which O2(+) + NO yields NO2(+) + O. The reaction is energetically possible for ground state O2(+) ions in the lowest vibrational level. Photoionization efficiency curves for NO(+), O2(+), and NO2(+) are presented and compared, with special emphasis on autoionization features. In addition to the production of NO2(+) by the cited reaction, there is also a possibility for NO2(+) formation by the process O2 + NO(+) yielding NO2(+) + O. This reaction is calculated to be exothermic for incident photon energies of 11.73 eV.

  3. 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.

  4. Exploring the universe in the laboratory: photoionized plasma experiments at Z relevant to astrophysics

    NASA Astrophysics Data System (ADS)

    Mancini, Roberto

    2014-08-01

    Many astrophysical environments such as x-ray binaries, active galactic nuclei, and accretion disks of compact objects have photoionized plasmas. Detailed x-ray spectral observations performed with the Chandra and XMM-Newton orbiting telescopes provide critical information on the state of photoionized plasmas. However, the complexity of the astrophysical environment makes the spectral analysis challenging, and thus laboratory experiments are important for data interpretation and testing of modeling codes. The Z facility at Sandia National Laboratories is a powerful source of x-rays to produce and study in the laboratory photoionized plasmas relevant for astrophysics. We discuss an experimental and theory/modeling effort in which the intense x-ray flux emitted at the collapse of a z-pinch implosion conducted at the Z pulsed-power machine is employed to produce a neon photoionized plasma. The broadband x-ray radiation flux from the z-pinch is used to both create the photoionized plasma and provide a source of backlighting photons to study the atomic kinetics through K-shell line absorption spectroscopy. The plasma is contained in a cm-scale gas cell that can be located at different distances from the z-pinch, thus effectively controlling the x-ray flux producing the plasma. Time-integrated transmission spectra have been observed with a spectrometer equipped with two elliptically-bent KAP crystals from photoionized plasmas covering an order of magnitude range in ionization parameter. The transmission data shows a rich line absorption spectrum that spans over several ionization stages of neon including Be-, Li-, He- and H-like ions. Modeling calculations are used to interpret the transmission spectra recorded in the Z experiments with the goal of extracting the charge- state distribution, electron temperature and the radiation flux driving the plasma, as well as to determine the ionization parameter of the plasma. This work is sponsored in part by the National Nuclear

  5. 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) Each application for an order under section 304(d)...

  6. 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) Each application for an order under section 304(d)...

  7. 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) Each application for an order under section 304(d)...

  8. 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…

  9. 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.

  10. 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…

  11. Pros and cons for C4d as a biomarker

    PubMed Central

    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.

    2013-01-01

    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

  12. The 2.5-Dimensional Photoionization Code ``PAN'' for Modeling of Axially Symmetric Nebulae: The Distinctive Features

    NASA Astrophysics Data System (ADS)

    Rokach, Oleg V.

    2005-11-01

    A multi-purpose spectrum synthesis code ``PAN'' (``Photoionized Axisymmetric Nebula'') is presented. The code allows computing of self-consistent steady-state models of morphologically-realistic axisymmetric gaseous, dust or gas+dust envelopes. Only the main features of the code ``PAN'' are enumerated here.

  13. 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.

  14. 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.

  15. 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.

  16. A High-resolution Vacuum Ultraviolet Laser Photoionization and Photoelectron Study of the Co Atom

    NASA Astrophysics Data System (ADS)

    Huang, Huang; Wang, Hailing; Luo, Zhihong; Shi, Xiaoyu; Chang, Yih-Chung; Ng, C. Y.

    2016-12-01

    We have measured the vacuum ultraviolet-photoionization efficiency (VUV-PIE) spectrum of Co in the energy range of 63,500-67,000 cm-1, which covers the photoionization transitions of Co(3d74s2 4F9/2) \\to Co+(3d8 3F4), Co(3d74s2 4F7/2) \\to Co+(3d8 3F3), Co(3d74s2 4F9/2) \\to Co+(3d8 3F3), Co(3d74s2 4F9/2) \\to Co+(3d8 3F2), and Co(3d74s2 4F9/2) \\to Co+(3d74s1 5F5). We have also recorded the pulsed field ionization photoelectron spectrum of Co in the same energy range, allowing accurate determinations of ionization energies (IEs) for the photoionization transitions from the Co(3d74s2 4F9/2) ground neutral state to the Co+(3F J ) (J = 4 and 3) and Co+(5F5) ionic states, as well as from the Co(3d74s2 4F7/2) excited neural state to the Co+(3d8 3F3) ionic state. The high-resolution nature of the VUV laser used has allowed the observation of many well-resolved autoionizing resonances in the VUV-PIE spectrum, among which an autoionizing Rydberg series, 3d74s1(5F5)np (n = 19-38), converging to the Co+(3d74s1 5F5) ionic state from the Co(3d74s2 4F9/2) ground neutral state is identified. The fact that no discernible step-like structures are present at these ionization thresholds in the VUV-PIE spectrum indicates that direct photoionization of Co is minor compared to autoionization in this energy range. The IE values, the autoionizing Rydberg series, and the photoionization cross sections obtained in this experiment are valuable for understanding the VUV opacity and abundance measurement of the Co atom in stars and solar atmospheres, as well as for benchmarking the theoretical results calculated in the Opacity Project and the IRON Project, and thus are of relevance to astrophysics.

  17. 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.

  18. Influence of uniaxial pressure on the photoionization of h-centers in semiconductors

    NASA Astrophysics Data System (ADS)

    Abramov, A. A.; Akimov, V. I.; Dalakyan, A. T.; Firsov, D. A.; Tulupenko, Victor N.; Vasko, Fedir T.

    1999-11-01

    Photoionization cross section of holes localization on deep centers with short distance potential at their transitions to the valence band of the uniaxially deformed semiconductor like Ge has been calculated. Because of splitting both acceptor level and extremum of hole subbands, photoionization threshold splits also - four kinds of such transitions appear. While growing temperature, the alteration of population of splitted impurity states occurs. It result in changing contribution of each kind of transitions to the absorption coefficient. As deformation disturbs spherical symmetry of the problem, appreciable polarization dependence of absorption coefficient appears. The calculation is based on the general quantum mechanic formula with transition matrix element using wave function of impurity center under deformation.

  19. 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.

  20. Inner-shell photoionization and core-hole decay of Xe and XeF2.

    PubMed

    Southworth, Stephen H; Wehlitz, Ralf; Picón, Antonio; Lehmann, C Stefan; Cheng, Lan; Stanton, John F

    2015-06-14

    Photoionization cross sections and partial ion yields of Xe and XeF2 from Xe 3d(5/2), Xe 3d(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 XeF2 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(+) and F(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(+) and F(+) 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.

  1. Direct identification of propargyl radical in combustion flames by vacuum ultraviolet photoionization mass spectrometry.

    PubMed

    Zhang, T; Tang, X N; Lau, K-C; Ng, C Y; Nicolas, C; Peterka, D S; Ahmed, M; Morton, Melita L; Ruscic, Branko; Yang, R; Wei, L X; Huang, C Q; Yang, B; Wang, J; Sheng, L S; Zhang, Y W; Qi, F

    2006-02-21

    We have developed an effusive laser photodissociation radical source, aiming for the production of vibrationally relaxed radicals. Employing this radical source, we have measured the vacuum ultraviolet (VUV) photoionization efficiency (PIE) spectrum of the propargyl radical (C(3)H(3)) formed by the 193 nm excimer laser photodissociation of propargyl chloride in the energy range of 8.5-9.9 eV using high-resolution (energy bandwidth = 1 meV) multibunch synchrotron radiation. The VUV-PIE spectrum of C(3)H(3) thus obtained is found to exhibit pronounced autoionization features, which are tentatively assigned as members of two vibrational progressions of C(3)H(3) in excited autoionizing Rydberg states. The ionization energy (IE = 8.674 +/- 0.001 eV) of C(3)H(3) determined by a small steplike feature resolved at the photoionization onset of the VUV-PIE spectrum is in excellent agreement with the IE value reported in a previous pulsed field ionization-photoelectron study. We have also calculated the Franck-Condon factors (FCFs) for the photoionization transitions C(3)H(3) (+)(X;nu(i),i = 1-12)<--C(3)H(3)(X). The comparison between the pattern of FCFs and the autoionization peaks resolved in the VUV-PIE spectrum of C(3)H(3) points to the conclusion that the resonance-enhanced autoionization mechanism is most likely responsible for the observation of pronounced autoionization features. We also present here the VUV-PIE spectra for the mass 39 ions observed in the VUV synchrotron-based photoionization mass spectrometric sampling of several premixed flames. The excellent agreement of the IE value and the pattern of autoionizing features of the VUV-PIE spectra observed in the photodissociation and flames studies has provided an unambiguous identification of the propargyl radical as an important intermediate in the premixed combustion flames. The discrepancy found between the PIE spectra obtained in flames and photodissociation at energies above the IE(C(3)H(3)) suggests that

  2. Biokinetic Analysis and Metabolic Fate of 2,4-D in 2,4-D-Resistant Soybean (Glycine max).

    PubMed

    Skelton, Joshua J; Simpson, David M; Peterson, Mark A; Riechers, Dean E

    2017-07-26

    The Enlist weed control system allows the use of 2,4-D in soybean but slight necrosis in treated leaves may be observed in the field. The objectives of this research were to measure and compare uptake, translocation, and metabolism of 2,4-D in Enlist (E, resistant) and non-AAD-12 transformed (NT, sensitive) soybeans. The adjuvant from the Enlist Duo herbicide formulation (ADJ) increased 2,4-D uptake (36%) and displayed the fastest rate of uptake (U50= 0.2 h) among treatments. E soybean demonstrated a faster rate of 2,4-D metabolism (M50= 0.2 h) compared to NT soybean, but glyphosate did not affect 2,4-D metabolism. Metabolites of 2,4-D in E soybean were qualitatively different than NT. Applying 2,4-D-ethylhexyl ester instead of 2,4-D choline (a quaternary ammonium salt) eliminated visual injury to E soybean, likely due to the time required for initial de-esterification and bioactivation. Excessive 2,4-D acid concentrations in E soybean resulting from ADJ-increased uptake may significantly contribute to foliar injury.

  3. Photodetachment and photoionization rainbows and glories

    NASA Astrophysics Data System (ADS)

    Cohen, S.; Kalaitzis, P.; Danakas, S.; Lépine, F.; Bordas, C.

    2017-03-01

    Quantum scattering has many similarities with the physics of the atmospheric rainbow. Diffraction effects, including rainbows and glories, have long been introduced in the physics of scattering, and particularly in nuclear, atomic and molecular physics. In this paper we describe the striking similarity between the optics of the primary rainbow and supernumerary bows and photodetachment microscopy, with the latter term referring to the photodetachment of a structureless anion in the presence of a static electric field. Further, we extend the aforementioned analogy to the more complex and fertile case of photoionization microscopy. Despite the fact that in the latter situation the analogy is only approximate, we demonstrate the emergence of additional features that are also found in classical optics, like higher-order bows and glories. Finally, based on the conclusions drawn from the above analyses, we discuss the significant contribution of glories in threshold photoelectron spectroscopy.

  4. Double photoionization of tropone and cyclooctatetraene

    NASA Astrophysics Data System (ADS)

    Hartman, Tim; Wehlitz, Ralf

    2017-05-01

    We have studied the double-photoionization process of tropone (C7H6O) and cyclooctatetraene (C8H8) as a function of photon energy using monochromatized synchrotron radiation between 18 and 270 eV. We compare our results with previously published data for partially deuterated benzene (C6H3D3), which exhibits three distinct features in the ratio of doubly to singly charged parent ions, whereas pyrrole (C4H4N) exhibits only two of these features. The question that we address in this paper is how molecules with different molecular structures (pentagonal, hexagonal, heptagonal, and octagonal carbon rings) affect the photon-energy dependence of this ratio.

  5. Isomer-dependent fragmentation dynamics of inner-shell photoionized difluoroiodobenzene

    DOE PAGES

    Ablikim, Utuq; Bomme, Cédric; Savelyev, Evgeny; ...

    2017-05-11

    The fragmentation dynamics of 2,6- and 3,5-difluoroiodobenzene after iodine 4d inner-shell photoionization with soft X-rays are studied using coincident electron and ion momentum imaging. By analyzing the momentum correlation between iodine and fluorine cations in three-fold ion coincidence events, we can distinguish the two isomers experimentally. Classical Coulomb explosion simulations are in overall agreement with the experimentally determined fragment ion kinetic energies and momentum correlations and point toward different fragmentation mechanisms and time scales. Finally, while most three-body fragmentation channels show clear evidence for sequential fragmentation on a time scale larger than the rotational period of the fragments, the breakupmore » into iodine and fluorine cations and a third charged co-fragment appears to occur within several hundred femtoseconds.« less

  6. Spectral dependence of nanocrystal photoionization probability: the role of hot-carrier transfer.

    PubMed

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

    2011-06-28

    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 (E(g)) and scale as ∼1.5E(g) and ∼3E(g), 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.

  7. 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 or...

  8. 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 or...

  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, 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 or...

  11. 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 or...

  12. 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 or...

  13. Digit ratio (2D:4D) in Klinefelter's syndrome.

    PubMed

    Manning, J T; Kilduff, L P; Trivers, R

    2013-01-01

    The ratio of second to fourth digit length (2D:4D) is a correlate of prenatal testosterone. High 2D:4D is associated with low prenatal testosterone, and reduced sensitivity to testosterone. Klinefelter's syndrome (KS; 47 XXY) affects the endocrine system, such that low testosterone levels are found in KS foetuses, new-borns and adults. To date, there are no published data regarding the pattern of 2D:4D in KS males. Here we consider 2D:4D in KS individuals (n = 51), their relatives (16 fathers and 15 mothers) and an unaffected control sample of 153 men and 153 women. Adult KS individuals were taller than their fathers and had shorter fingers than fathers and male controls. Compared with fathers, male controls and mothers, KS males had shorter fingers relative to height. With regard to 2D:4D, KS individuals had higher 2D:4D than fathers (right and left hands), male controls (right and left hands) and mothers (left hands). Among KS males older than 13 years there were 34 individuals currently prescribed testosterone and nine not prescribed. In comparison to the former, the latter individuals had higher right 2D:4D and higher right-left 2D:4D. We conclude that KS males have mean 2D:4D values similar to those found in female population norms. In addition, testosterone supplementation in KS males may be most common for individuals with low right 2D:4D. © 2012 American Society of Andrology and European Academy of Andrology.

  14. Photoionization of psoralen derivatives in micelles: Imperatorin and alloimperatorin

    NASA Astrophysics Data System (ADS)

    El-Gogary, Sameh R.

    2010-11-01

    The fluorescence properties of psoralen derivatives, 8-methoxypsoralen (8-MOP), imperatorin (IMP) and alloimperatorin (ALLOI), were investigated in various solvent and micellar solutions. The variation in intensity and maxima of the fluorescence in micellar solutions suggest that psoralens are located in the micelle-water interface region. Radical cations and hydrated electrons were generated by photoionization in micellar solution upon excitation at 266 nm. A nonlinear relationship between transient yield and photon fluency was obtained for each compound, indicating that a two-photon mechanism is predominant in the photoionization of the sensitizers. The photoionization efficiencies are significantly higher in anionic sodium dodecyl sulfate (SDS) than in cationic cetyltrimethylammonium bromide (CTAB) micelles, reflecting the influence of micelle charge on the efficiency of the separation of the photoproduced charge carriers. The photoionization efficiencies of IMP and ALLOI are similar.

  15. 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.

  16. 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.

  17. An Atomic Photoionization Experiment by Harmonic Generation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Trallero, Carlos; Frolov, Mikhail; Sarantseva, Tatiana S.; Manakov, Nikolay; Fulfer, Kristen D.; Wilson, Benjamin; Troß, Jan; Ren, Xiaoming; Poliakoff, Erwin; Silaev, Alexander A.; Vvedenskii, Nikolay; Starace, Anthony

    2016-05-01

    Measurements of the high-order harmonic generation yield of the argon (Ar) atom driven by a strong elliptically polarized laser field are shown to completely determine the field-free differential photoionization cross section of Ar, i.e., the energy dependence of both the angle-integrated photoionization cross section and the angular distribution asymmetry parameter. NSF EPSCoR Track II Nebraska-Kansas Awards No. 1430519 and No. 1430493.

  18. 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.

  19. 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

  20. 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.

  1. Vibrationally resolved cross sections for the photoionization of CS2

    NASA Astrophysics Data System (ADS)

    Stratmann, R. E.; Lucchese, Robert R.

    1994-12-01

    We have performed vibrationally resolved calculations of the excitation of the symmetric stretch in the photoionization of CS2 leading to the X 2Πg, A 2Πu, B 2Σ+u, and C 2Σ+g states of CS+2. Previous theoretical work has determined that the kπg shape resonance in the (5σu)-1 channel consists mainly of a linear combination of low lying virtual d orbitals on sulfur and is thus essentially atomic in nature. This conclusion was primarily based on the shape of the resonant wave function and the insensitivity of the energy of the resonance to bond stretching. Here, we have determined that the energies of the kπ shape resonances located well above threshold and the σ bound states just below threshold are insensitive to bond length. We have also found nearly constant vibrational branching ratios in all channels and polarization components. This is in qualitative agreement with experimental vibrationally resolved cross sections [S. Kakar, H. C. Choi, and E. D. Poliakoff, J. Chem. Phys. 97, 4690 (1992)] which show nearly constant vibrational branching ratios. Our present results indicate that caution must be exercised when using bond length sensitivity as an exclusive means to determine the existence of shape resonances.

  2. Sturmian approach to the study of photoionization of atoms and molecules

    NASA Astrophysics Data System (ADS)

    Granados Castro, Carlos Mario; Ancarani, Lorenzo Ugo; Gasaneo, Gustavo; Mitnik, Dario M.

    2013-09-01

    In this presentation we study the photoionization of atoms and molecules using ultrashort laser pulses, solving the time-independent Schrödinger equation (TISE) in a first order perturbation theory. The interaction laser-matter is described with the dipolar operator in the velocity gauge. Generalized Sturmian functions are used to solve the driven equation for a scattering wave function which includes all the information about the ionization problem. For the atomic case, we study the photoionization of He atom using the Hermann-Skillman potential together with the one-active electron approximation. For molecular systems (CH4 in this work), we use first a spherically symmetric potential Ui(r), and then a more realistic potential that includes all the nuclei and other electrons interaction, as in. For each molecular orbital we use Moccia's wave functions, solve the TISE with an initial molecular orbital i of the ground state and extract the corresponding photoionization cross sections. For both atomic and molecular systems we compare our results with previous calculations and available experimental data.

  3. Molecular Frame Photoemission: Probe of the Photoionization Dynamics for Molecules in the Gas Phase

    NASA Astrophysics Data System (ADS)

    Dowek, D.; Picard, Y. J.; Billaud, P.; Elkharrat, C.; Houver, J. C.

    2009-04-01

    Molecular frame photoemission is a very sensitive probe of the photoionization (PI) dynamics of molecules. This paper reports a comparative study of non-resonant and resonant photoionization of D2 induced by VUV circularly polarized synchrotron radiation at SOLEIL at the level of the molecular frame photoelectron angular distributions (MFPADs). We use the vector correlation method which combines imaging and time-of-flight resolved electron-ion coincidence techniques, and a generalized formalism for the expression of the I(χ, θe, varphie) MFPADs, where χ is the orientation of the molecular axis with respect to the light quantization axis and (θe, varphie) the electron emission direction in the molecular frame. Selected MFPADs for a molecule aligned parallel or perpendicular to linearly polarized light, or perpendicular to the propagation axis of circularly polarized light, are presented for dissociative photoionization (DPI) of D2 at two photon excitation energies, hν = 19 eV, where direct PI is the only channel opened, and hν = 32.5 eV, i.e. in the region involving resonant excitation of Q1 and Q2 doubly excited state series. We discuss in particular the properties of the circular dichroism characterizing photoemission in the molecular frame for direct and resonant PI. In the latter case, a remarkable behavior is observed which may be attributed to the interference occurring between undistinguishable autoionization decay channels.

  4. TPCI: the PLUTO-CLOUDY Interface . A versatile coupled photoionization hydrodynamics code

    NASA Astrophysics Data System (ADS)

    Salz, M.; Banerjee, R.; Mignone, A.; Schneider, P. C.; Czesla, S.; Schmitt, J. H. M. M.

    2015-04-01

    We present an interface between the (magneto-) hydrodynamics code PLUTO and the plasma simulation and spectral synthesis code CLOUDY. By combining these codes, we constructed a new photoionization hydrodynamics solver: the PLUTO-CLOUDY Interface (TPCI), which is well suited to simulate photoevaporative flows under strong irradiation. The code includes the electromagnetic spectrum from X-rays to the radio range and solves the photoionization and chemical network of the 30 lightest elements. TPCI follows an iterative numerical scheme: first, the equilibrium state of the medium is solved for a given radiation field by CLOUDY, resulting in a net radiative heating or cooling. In the second step, the latter influences the (magneto-) hydrodynamic evolution calculated by PLUTO. Here, we validated the one-dimensional version of the code on the basis of four test problems: photoevaporation of a cool hydrogen cloud, cooling of coronal plasma, formation of a Strömgren sphere, and the evaporating atmosphere of a hot Jupiter. This combination of an equilibrium photoionization solver with a general MHD code provides an advanced simulation tool applicable to a variety of astrophysical problems. A copy of the code is available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/576/A21

  5. Laboratory study of K-shell photoionization of oxygen and oxygen hydrides ions

    NASA Astrophysics Data System (ADS)

    Bizau, Jean-Marc

    2016-05-01

    The interpretation of the spectra sent by satellites required the knowledge of many atomic data, including photoionization cross sections or energy and oscillator strength of bound-bound transitions for many ions, over a broad photon energy range going from infra-red to x-rays. These data are mainly provided by theoretical results using state-of-the-art methods like R-matrix. Recently, discrepancies have been observed between the calculated energy of the Kα transitions in atomic oxygen and its ions and those determined from the satellites observations. The results of the experimental studies of K-shell photoionization of oxygen ions performed at the French synchrotron radiation center SOLEIL will be presented. A merged-beam setup installed on the PLEIADES beam line allows for the determination of absolute photoionization cross sections and transitions energy on singly- and multiply-charged ions in the 10-1000 eV photon energy range. The first results obtained with this setup on oxygen hydrides will be also presented.

  6. X-ray emissions in 3d, 4d, and 5d ranges for uranium ions

    SciTech Connect

    Bonnelle, C.; Jonnard, P.; Barre, C.; Giorgi, G.; Bruneau, J.

    1997-05-01

    Radiative decay of nd{sup {minus}1}5f{sup m+1} excited states in UO{sub 2} induced by electron collisions is studied theoretically and experimentally. Energies, transition probabilities, and photoexcitation cross sections for the relevant configurations of U{sup 4+} are calculated by using the multiconfiguration Dirac-Fock method. Experimental observations are made in the 4d range. Direct recombination of the excited 5f electron to the 4d hole and 4d-6p emission in the presence of the spectator excited 5f electron are observed. From the theoretical results, the spectra are simulated and compared to the observed spectra in the three nd regions. The agreement is correct and describes the evolution of the coupling scheme in the nd{sup {minus}1}5f{sup 3} excited states from n=3 to n=5. {copyright} {ital 1997} {ital The American Physical Society}

  7. Anomalous Abundances in Gaseous Nebulae From Recombination and Collisional Lines: Improved Photoionization and Recombination Studies

    NASA Astrophysics Data System (ADS)

    Pradhan, Anil Kumar; Nahar, S. N.; Eissner, W. B.; Montenegro, M.

    2011-01-01

    A perplexing anomaly arises in the determination of abundances of common elements in gaseous nebulae, as derived from collisionally excited lines (CEL) as opposed to those from Recombination Lines (RCL). The "abundance discrepancy factors" can range from a factor of 2 to an order of magnitude or more. That has led to quite different interpretation of the physical structure and processes in gaseous nebulae, such as temperature fluctuations across the object, or metal-rich concentrations leading to a dual-abundnace scenario. We show that the problem may lie in inaccuracies in photoionization and recombination models neglecting low-energy resonance phenomena due to fine structure. Whereas the atomic physics of electron impact excitation of forbidden lines is well understood, and accurate collision strengths have long been available, that is not generally the case for electron-ion recombination cross sections. A major problem is the inclusion of relativisitic effects as it pertains to the existence of very low-energy fine structure resonances in photoionization cross sections. We carry out new relativistic calculations for photoionization and recombination cross sections using a recently extended version of the Breit-Pauli R-matrix codes, and the unified electron-ion recombination method that subsumes both the radiative and the dielectronic recombination (RR and DR) processes in an ab initio and self-consistent manner. We find that near-thresold resonances manifest themselves within fine structure levels of the ground state of ions, enhancing low-temperature recombination rate coefficients at 1000-10,000 K. The resulting enahncement in level-specific and total recombination rate coefficients should therefore lead to reduced abundances derived from RCL, and in accordance with those from CEL. We present results for photoionization of O II into, and recombination from, O III. Theoretical cross sections are benchmarked against high-resolution measurements from synchrotron

  8. Photoionization and photofragmentation of SF6 in helium nanodroplets.

    PubMed

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

    2006-10-12

    The photoionization of He droplets doped with SF6 was investigated using tunable vacuum ultraviolet (VUV) synchrotron radiation from the Advanced Light Source (ALS). The resulting ionization and photofragmentation dynamics were characterized using time-of-flight mass spectrometry combined with photofragment and photoelectron imaging. Results are compared to those of gas-phase SF6 molecules. We find dissociative photoionization to SF5+ to be the dominant channel, in agreement with previous results. Key new findings are that (a) the photoelectron spectrum of the SF6 in the droplet is similar but not identical to that of the gas-phase species, (b) the SF5+ photofragment velocity distribution is considerably slower upon droplet photoionization, and (c) fragmentation to SF4+ and SF3+ is much less than in the photoionization of bare SF6. From these measurements we obtain new insights into the mechanism of SF6 photoionization within the droplet and the cooling of the hot photofragment ions produced by dissociative photoionization.

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

    SciTech Connect

    Hudson, Eric Allen

    1993-08-01

    Near-edge soft x-ray photoionization spectra were measured for CO, SF6, H2S, and D2S 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 H2CO and D2CO 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 L2,3 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 H2S and D2S molecules were also measured near the sulfur L2,3 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.

  10. Photoionization of chlorine-like potassium and calcium ions

    NASA Astrophysics Data System (ADS)

    Alna'Washi, Ghassan A.

    Absolute photoionization cross-section measurements were performed for a mixture of 2Po 3/2 ground state and 2Po 1/2 metastable state Cl-like K2+ and Ca3+ ions over the photon energy range 44.240-69.741 eV for K2+ and 65.7-104.6 eV for Ca3+. The measurements were performed by merging an ion beam with a beam of synchrotron radiation from an undulator magnet using the ion-photon merged-beams endstation on beamline 10.0.1 of the Advanced Light Source (ALS) at Lawrence Berkley National Laboratory. High resolution measurements were performed near the 2P o 3/2 ground-state ionization threshold for both ions. The ground-state ionization thresholds of K2+ and Ca 3+ was measured to be 45.740 +/- 0.015 eV and 67.070 +/- 0.018 eV, respectively. These energies are respectively 0.066 eV and 0.200 eV lower than the tabulated values in the NIST database. These data are compared to previous measurements for Cl-like Ar+. Most of the observed resonance features belong to multiple Rydberg series of transitions to autoionizing states. These features were assigned spectroscopically using the quantum defect form of the Rydberg formula, guided by calculations of the energies and oscillator strengths of transitions to autoionizing states performed using the pseudo-relativistic Cowan Hartree-Fock atomic structure code. The measurements for Ca3+ compare favorably with recent unpublished R-matrix calculations performed by McLaughlin in a close-coupling expansion within the semi-relativistic Breit-Pauli approximation. This includes the energy positions of the calculated resonances and the magnitudes of the resonant and nonresonant components of the cross section.

  11. Experimental validation of a 4D elastic registration algorithm.

    PubMed

    Leung, Corina; Hashtrudi-Zaad, Keyvan; Foroughi, Pezhman; Abolmaesumi, Purang

    2008-01-01

    This paper presents an extensive validation study of an elastic registration algorithm for dynamic 3D ultrasound images (also known as a 4D image). The registration algorithm uses attribute vectors from both a fixed and previous moving images to perform feature-based alignment of a series of images. The 4D method reduces computational requirements and increases the effective search space for the location of corresponding features, resulting in enhanced registration speed when compared to a static 3D registration technique. Experimental analysis revealed up to 32% improvement in speed when using the 4D method, which makes the algorithm attractive for real-time applications.

  12. A 4D representation of DNA sequences and its application

    NASA Astrophysics Data System (ADS)

    Liao, Bo; Tan, Mingshu; Ding, Kequan

    2005-02-01

    A 4D representation of DNA sequences has been derived for mathematical denotation of DNA sequence. The 4D representation also avoids loss of information accompanying alternative 2D and 3D representation. The geometrical centers of the 4D graph of DNA sequences indicate the distribution of base frequencies. A interesting phenomenon is observed for Goat and Gallus β-globin genomes with high G + C content. The examination of similarities/dissimilarities among the coding sequences of the first exon of β-globin gene of different species illustrates the utility of the approach.

  13. Resonant ionization spectroscopy of autoionizing Rydberg states in cobalt and redetermination of its ionization potential

    DOE PAGES

    Liu, Yuan; Gottwald, T.; Mattolat, C.; ...

    2017-03-20

    We obtained multi-step resonance ionization spectroscopy of cobalt using a hot-cavity laser ion source and three Ti:Sapphire lasers. Furthermore, the photoionization spectra revealed members of five new autoionizing Rydberg series that originate from three different lower levels of 3d74s5s h4F9/2, 3d74s4d f4G11/2, and 3d74s4d f4H13/2 and converge to the first four excited states of singly ionized Co. Our analyses of the Rydberg series yield 63564.689 0.036 cm-1 as the first ionization potential of Co, which is an order of magnitude more accurate than the previous estimation. Using a three-step resonance ionization scheme that employs an autoinizing Rydberg state in themore » last transition, we obtained an overall ionization efficiency of about 18% for Co.« less

  14. Resonant ionization spectroscopy of autoionizing Rydberg states in cobalt and redetermination of its ionization potential

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Gottwald, T.; Mattolat, C.; Wendt, K.

    2017-04-01

    Multi-step resonance ionization spectroscopy of cobalt has been performed using a hot-cavity laser ion source and three Ti:Sapphire lasers. The photoionization spectra revealed members of five new autoionizing Rydberg series that originate from three different lower levels of 3d 74s5s h 4F9/2, 3d 74s4d f 4G11/2, and 3d 74s4d f 4H13/2 and converge to the first four excited states of singly ionized Co. The analyses of the Rydberg series yield 63 564.689 ± 0.036 cm‑1 as the first ionization potential of Co, which is an order of magnitude more accurate than the previous estimation. Using a three-step resonance ionization scheme that employs an autoinizing Rydberg state in the last transition, we obtained an overall ionization efficiency of about 18% for Co. ).

  15. SU-D-BRB-01: 4D-CT Lung Ventilation Images Vary with 4D-CT Sorting Techniques.

    PubMed

    Yamamoto, T; Kabus, S; Lorenz, C; Johnston, E; Maxim, P; Loo, B; Keall, P

    2012-06-01

    4D-CT ventilation imaging is a novel promising technique for lung functional imaging and has potential as a biomarker for radiation pneumonitis, but has not been validated in human subjects. The current 4D- CT technique with phase-based sorting results in artifacts at an alarmingly high frequency (90%), which may introduce variations into ventilation calculations. The purpose of this study was to quantify the variability of 4D- CT ventilation imaging to 4D-CT sorting techniques. Two 4D-CT images were generated from the same data set by: (1) phase-based; (2) anatomic similarity- and abdominal displacement-based sorting for five patients. Two ventilation image sets (V_phase and V_anat) were then calculated by deformable image registration of peak-exhale and peak-inhale4D-CT images and quantification of regional volume change based on Hounsfield unit change. The variability of 4D-CT ventilation imaging wasquantified using the voxel-based Spearman rank correlation coefficients and Dice similarity coefficients (DSC) for the spatial overlap of segmented low- functional lung regions. The relationship between the abdominal motionrange variation and ventilation variation was also assessed using linearregression. Furthermore, the correlations between V_phase or V_anat and SPECT ventilation images (assumed ground-truth) were compared. In general, displacement- and anatomic similarity-based sorting reduced 4D- CT artifacts compared to phase-based sorting. The voxel-based correlationsbetween V_phase and V_anat were only moderate (range, 0.57-0.77). The DSCs for the low-functional lung regions were moderate to substantial (0.58-0.70). The relationship between the motion range variation and ventilation variation was strong on average (R2=0.79±0.25), suggesting that ventilation variations are related to 4D-CT artifacts. Vanat was found to improve correlations with SPECT ventilation images compared to V_phase. 4D-CT ventilation images vary markedly with 4D-CT sorting techniques. 4

  16. Photoionization studies of intramolecular dynamics: A closer look

    NASA Astrophysics Data System (ADS)

    Wu, Chuanyong

    Using synchrotron radiation as an excitation source, dispersed fluorescence measurements of two different molecular systems are presented in this dissertation with the intention to study the two fundamental aspects of shape resonances-complexity and completeness. C6F6 is a relative large and complex molecule in the sense that nonradiative transitions can take place unimolecularly in the free species. The elucidation of the ionization dynamics of this molecule helps to bridge the gap from simple molecules to matter in condensed phases. In the 2a2u-1 photoionization study of C6F6, the non-Franck-Condon behavior of the vibrational distributions at around 20 eV indicates the existence of shape resonances in this energy range. This is the first time a shape resonance of such a complex molecule is characterized with vibrational resolution detail over such a broad energy range. While the study of C6F6 is to disentangle the complexity aspect of shape resonance, the investigation of CO is an attempt to carry the shape resonant study to its completeness. The original goal of the 4σ- 1 photoionization study of CO was to investigate the vibrational-rotational-electronic (V-R-E) coupling. To be specific, we intended to study the shape resonant effects on the rotational population distributions for alternative vibrational levels. While the 4/sigma/to k/sigma shape resonance influences do not seem to be very significant, the results brought to attention another issue-continuum-continuum channel coupling. The study shows that the R-dependent aspects of shape- resonance-induced continuum coupling affects rotational population distributions for alternative vibrational states differently. In modern scientific researches, the development of instruments plays a critical role. The trend today is for computers to serve as the engine for instrumentation- virtual instruments. By walking through the development processes of a real-time instrument control and data acquisition system, the

  17. 4d N =2 theories with disconnected gauge groups

    NASA Astrophysics Data System (ADS)

    Argyres, Philip C.; Martone, Mario

    2017-03-01

    In this paper we present a beautifully consistent web of evidence for the existence of interacting 4d rank-1 N = 2 SCFTs obtained from gauging discrete subgroups of global symmetries of other existing 4d rank-1 N = 2 SCFTs. The global symmetries that can be gauged involve a non-trivial combination of discrete subgroups of the U(1) R , low-energy EM duality group SL(2,Z), and the outer automorphism group of the flavor symmetry algebra, Out( F ).

  18. Analysis of 3d photoionization and subsequent Auger decay of atomic germanium

    SciTech Connect

    Jaenkaelae, K.; Anin, D.; Huttula, S.-M.; Heinaesmaeki, S.; Huttula, M.; Urpelainen, S.

    2011-11-15

    Experimental and theoretical study of the 3d photoionization and subsequent Auger decay of initially neutral atomic germanium is presented. The features of the high-resolution photoelectron and Auger electron spectra are interpreted with the aid of multiconfiguration calculations. The binding energies and relative cross sections of the 3d ionized fine-structure states of Ge are given. The complete M{sub 4,5}NN Auger electron spectrum to doubly ionized final states of the Ge ion is interpreted and discussed.

  19. 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.

  20. [2D:4D finger ratio and language development].

    PubMed

    Albores-Gallo, L; Fernández-Guasti, A; Hernández-Guzmán, L; List-Hilton, C

    A possible hormonal influence in language development has been suggested in the recent years. The 2D:4D finger ratio is an indirect measure for prenatal androgen exposure. It is negatively related to prenatal testosterone and positively related to prenatal estrogen, resulting in a lower ratio for men and a larger ratio for women. It can be explored in children as young as 2 years old. To study if an association exists between the 2D:4D finger ratio and language development (vocabulary) and/or language problems. The lengths of the second digit (index finger) (2D) and the fourth digit (ring finger) (4D) were measured in 97 preschoolers and the Language Development Survey was administered to the parents. A weak negative correlation between language development (vocabulary) and right 2D:4D ratio was found in both sexes for children aged 4 or less years, significant only in boys. A strong negative correlation between language articulation problems and right 2D:4D ratio in both sexes for children aged 3 or less years, and a lower negative correlation between articulation problems and right 2D:4D ratio were found for boys aged 4 or less years. Findings suggest an important role for testosterone in language development (vocabulary) and a possible influence on articulation problems, probably through higher testosterone levels.

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

    PubMed

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

    2010-08-07

    We have performed a two-color laser photoionization and photoelectron study of nickel carbide (NiC) and its cation (NiC(+)). 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(+)(X (2)Sigma(+);v(+)=0-3). We have also obtained well-resolved rotational transitions for the v(+)=0 and 1 vibrational bands of the NiC(+)(X (2)Sigma(+)) ground state. The assignment of rotational transitions observed between the neutral NiC intermediate state and the NiC(+) 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(-1) (8.372 05+/-0.000 06 eV). This experiment also provides reliable values for the vibrational spacing [DeltaG(1/2)=859.5+/-0.5 cm(-1)], rotational constants (B(e)(+)=0.6395+/-0.0018 cm(-1) and alpha(e)(+)=0.0097+/-0.0009 cm(-1)), and equilibrium bond distance (r(e)(+)=1.628 A) for the NiC(+)(X (2)Sigma(+)) 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

    We have performed a two-color laser photoionization and photoelectron study of nickel carbide (NiC) and its cation (NiC+). 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+(X Σ2+;v+=0-3). We have also obtained well-resolved rotational transitions for the v+=0 and 1 vibrational bands of the NiC+(X Σ2+) ground state. The assignment of rotational transitions observed between the neutral NiC intermediate state and the NiC+ 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-1 (8.372 05±0.000 06 eV). This experiment also provides reliable values for the vibrational spacing [ΔG(1/2)=859.5±0.5 cm-1], rotational constants (Be+=0.6395±0.0018 cm-1 and αe+=0.0097±0.0009 cm-1), and equilibrium bond distance (re+=1.628 Å) for the NiC+(X Σ2+) 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.

  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. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Absolute Total Photoionization Cross Section of C60 in the Range of 25-120 eV: Revisited

    NASA Astrophysics Data System (ADS)

    Kafle, Bhim P.; Katayanagi, Hideki; Prodhan, Md. Serajul I.; Yagi, Hajime; Huang, Chaoqun; Mitsuke, Koichiro

    2008-01-01

    The absolute total photoionization cross section σabs,I of gaseous C60 is measured in the photon energy hν range from 25 to 120 eV by photoionization mass spectrometry with synchrotron radiation. The absolute detection efficiencies of photoions in different charge states are evaluated. The present σabs,I curve is combined with the photoabsorption cross section curves of C60 at hν=3.5--26 eV in the literature, after appropriate alterations of the vapor pressure are taken into account. The oscillator strengths are computed from the composite curve to be 178.5 and 230.5 for the hν ranges from 3.5 to 40.8 eV and from 3.5 to 119 eV, respectively. These oscillator strengths agree well with those expected from the Thomas-Kuhn-Reiche sum rule and 60 times the photoabsorption cross section of a carbon atom. Moreover, the present σabs,I curve behaves similarly to the relative photoionization cross section curve reported by Reinköster et al.

  9. Recent development of the photoionization / PDR code Cloudy

    NASA Astrophysics Data System (ADS)

    van Hoof, P. A. M.; Porter, R. L.; Ferland, G. J.

    2011-05-01

    Cloudy is a widely used open-source modeling tool for photoionized and PDR/XDR environments. It was the first code that could produce a unified and fully self-consistent model of both the ionized region and the PDR surrounding a central source. Such an environment can e.g. be found in massive star forming regions, in planetary nebulae or around AGN. The code is also capable of producing "classical" PDR models that do not include an ionized region. The emphasis of the code is on detailed and state-of-the-art treatment of micro-physical processes. Cloudy is continually being updated to improve this treatment and to add more and newer atomic and molecular data. On this poster we will discuss some of these developments, including the addition of the LAMDA, CDMS and JPL molecular line databases. These will allow us to make NLTE predictions for the molecular line emission, but the accuracy of those predictions will be limited by the quality (or even absence) of collision strength data. We will discuss the impact this has on the accuracy of the predicted spectra in typical ISM conditions.

  10. Vibrationally mode-specific excitation in molecular photoionization

    NASA Astrophysics Data System (ADS)

    Poliakoff, Erwin

    2003-05-01

    Recent measurements on the photoionization of polyatomic molecules demonstrate that excitations of nominally forbidden vibrations are surprisingly intense, and that their energy dependences elucidate why they are occurring. The unifying theme underscored by these results is that the continuum photoelectron exerts tremendous influence on which vibrations are excited and the degree of excitation. These data are generated via high resolution photoelectron spectroscopy coupled with high brightness synchrotron radiation. Results are presented on the linear triatomic systems CO_2, CS_2, and N_2O. For these molecules, all vibrational modes are excited. Moreover, the energy dependences for the alternative vibrational modes exhibit dramatic differences, which are attributed to the degree and type of localization experienced by the continuum photoelectron in the molecular framework. And while the electronic structures of these molecules are very similar, they behave very differently from each other, even over a very broad energy range. Theoretical results by Prof. R.R. Lucchese will be discussed, and the comparison with experiment helps to illustrate the state of our understanding of these phenomena. In addition to the linear triatomics, preliminary results will be reported on BF_3, as well as a van der Waals dimer, Ar_2.

  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. Oscillator strengths and branching fractions of 4d75p-4d75s Rh II transitions

    NASA Astrophysics Data System (ADS)

    Bouazza, Safa

    2017-01-01

    This work reports semi-empirical determination of oscillator strengths, transition probabilities and branching fractions for Rh II 4d75p-4d75s transitions in a wide wavelength range. The angular coefficients of the transition matrix, beforehand obtained in pure SL coupling with help of Racah algebra are transformed into intermediate coupling using eigenvector amplitudes of these two configuration levels determined for this purpose; The transition integral was treated as free parameter in the least squares fit to experimental oscillator strength (gf) values found in literature. The extracted value: <4d75s|r1|4d75p> =2.7426 ± 0.0007 is slightly smaller than that computed by means of ab-initio method. Subsequently to oscillator strength evaluations, transition probabilities and branching fractions were deduced and compared to those obtained experimentally or through another approach like pseudo-relativistic Hartree-Fock model including core-polarization effects.

  13. Magnetic dipole transitions in 4d{sup N} configurations of tungsten ions

    SciTech Connect

    Jonauskas, V.; Kisielius, R.; Kyniene, A.; Kucas, S.; Norrington, P. H.

    2010-01-15

    Magnetic dipole transitions between the levels of ground 4d{sup N} configurations of tungsten ions were analyzed by employing a large basis of interacting configurations. Previously introduced configuration interaction strength between two configurations was used to determine the configurations with the largest contribution to wave functions of atomic states for the considered configurations. Collisional-radiative modeling was performed for the levels of the ground configuration coupled through electric dipole transitions with 4p{sup 5}4d{sup N+1} and 4d{sup N-1}4f configurations. New identification of some lines observed in the electron-beam ion trap plasma was proposed based on calculations in which wavelength convergence was reached.

  14. 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.

  15. 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

  16. Digit ratio (2D:4D) and postoperative pain perception.

    PubMed

    Kasielska-Trojan, Anna; Stabryła, Piotr; Antoszewski, Bogusław

    2017-07-01

    It has not been established whether sex differences in pain perception are influenced by prenatal sex hormones. Digit ratio as an indicator of prenatal hormone exposure can be used as a simple measure of the influence of prenatal hormones on pain sensitivity or perception in adulthood. The aim of this study was to determine a correlation between the 2D:4D ratio and pain perception in the postoperative period after rhinoplasty. A prospective cohort study of 100 patients (50 women of the mean age of 30.74±8.09years and 50 men of the mean age of 30.98±10.86years) who underwent posttraumatic rhinoplasty due to the nose trauma in Plastic, Reconstructive and Aesthetic Surgery Clinic. The following measurements were taken the day before a surgery: body height, waist and hip circumference, II and IV digits' lengths and body weight. All subjects filled in a questionnaire including 0-10-point VAS scales to assess postoperative pain 1h after an operation (AO), 6h AO, 12h AO, 24h AO and 48h AO. Women with low 2D:4D reported significantly more pain 1h after an operation than women with high 2D:4D. Similar correlation was observed for low 2D:4D in women 48h AO. In men, low 2D:4D was associated with lower postoperative pain 12h AO (p=0.029). In conclusion, we showed that low 2D:4D in women was associated with high postoperative pain, and low right 2D:4D in men was associated with low postoperative pain. This may suggest that intrauterine estrogen exposure makes women more resistant to pain. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. 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.

  18. 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.

  19. Photoionization thresholds of rare-earth impurity ions. EuS :CaF2, CeT :YAG, and SmS :CaF2

    SciTech Connect

    Pedrini, C.; Rogemond, F.; McClure, D.S.

    1986-02-15

    The spectral dependence of the photoionization energy of EuS :CaF2, CeT :YAG, and SmS :CaF2 systems have been measured and thresholds experimentally determined and compared with theoretical values calculated from electrostatic models. It is shown that the excited state absorption transitions or the persistent hole burning observed by other authors occur above the threshold energy of photoionization of the impurities and that the states of the crystal which form the bottom of the conduction band may play an important role in the strong probability of these processes. A review of thresholds now known is also given.

  20. CaH Rydberg series, oscillator strengths and photoionization cross sections from Molecular Quantum Defect and Dyson Orbital theories

    NASA Astrophysics Data System (ADS)

    Velasco, A. M.; Lavín, C.; Díaz-Tinoco, Manuel; Ortiz, J. V.

    2017-01-01

    In this work, electron-propagator methods are applied to the calculation of the ionization potential and vertical excitation energies for several Rydberg series of the CaH molecule. The present calculations cover more highly excited states than those previously reported. In particular, excitation energies for ns (n>5), np (n>5), nd (n>4) and nf Rydberg states are given. Oscillator strengths for electronic transitions involving Rydberg states of CaH, as well as photoionization cross sections for Rydberg channels, also have been determined by using the Molecular Quantum Defect Orbital approach. Good agreement has been found with the scarce comparative data that are available for oscillator strengths. To our knowledge, predictions of photoionization cross sections from the outermost orbital of CaH are made here for the first time. A Cooper minimum and mixed atomic orbital character in some of the Dyson orbitals are among the novel features of these present calculations.

  1. 4D cone beam CT via spatiotemporal tensor framelet

    SciTech Connect

    Gao, Hao; Li, Ruijiang; Xing, Lei; Lin, Yuting

    2012-11-15

    Purpose: On-board 4D cone beam CT (4DCBCT) offers respiratory phase-resolved volumetric imaging, and improves the accuracy of target localization in image guided radiation therapy. However, the clinical utility of this technique has been greatly impeded by its degraded image quality, prolonged imaging time, and increased imaging dose. The purpose of this letter is to develop a novel iterative 4DCBCT reconstruction method for improved image quality, increased imaging speed, and reduced imaging dose. Methods: The essence of this work is to introduce the spatiotemporal tensor framelet (STF), a high-dimensional tensor generalization of the 1D framelet for 4DCBCT, to effectively take into account of highly correlated and redundant features of the patient anatomy during respiration, in a multilevel fashion with multibasis sparsifying transform. The STF-based algorithm is implemented on a GPU platform for improved computational efficiency. To evaluate the method, 4DCBCT full-fan scans were acquired within 30 s, with a gantry rotation of 200°; STF is also compared with a state-of-art reconstruction method via spatiotemporal total variation regularization. Results: Both the simulation and experimental results demonstrate that STF-based reconstruction achieved superior image quality. The reconstruction of 20 respiratory phases took less than 10 min on an NVIDIA Tesla C2070 GPU card. The STF codes are available at https://sites.google.com/site/spatiotemporaltensorframelet . Conclusions: By effectively utilizing the spatiotemporal coherence of the patient anatomy among different respiratory phases in a multilevel fashion with multibasis sparsifying transform, the proposed STF method potentially enables fast and low-dose 4DCBCT with improved image quality.

  2. 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

  3. Galaxy formation with local photoionization feedback - I. Methods

    NASA Astrophysics Data System (ADS)

    Kannan, R.; Stinson, G. S.; Macciò, A. V.; Hennawi, J. F.; Woods, R.; Wadsley, J.; Shen, S.; Robitaille, T.; Cantalupo, S.; Quinn, T. R.; Christensen, C.

    2014-01-01

    We present a first study of the effect of local photoionizing radiation on gas cooling in smoothed particle hydrodynamics simulations of galaxy formation. We explore the combined effect of ionizing radiation from young and old stellar populations. The method computes the effect of multiple radiative sources using the same tree algorithm as used for gravity, so it is computationally efficient and well resolved. The method foregoes calculating absorption and scattering in favour of a constant escape fraction for young stars to keep the calculation efficient enough to simulate the entire evolution of a galaxy in a cosmological context to the present day. This allows us to quantify the effect of the local photoionization feedback through the whole history of a galaxy's formation. The simulation of a Milky Way-like galaxy using the local photoionization model forms ˜40 per cent less stars than a simulation that only includes a standard uniform background UV field. The local photoionization model decreases star formation by increasing the cooling time of the gas in the halo and increasing the equilibrium temperature of dense gas in the disc. Coupling the local radiation field to gas cooling from the halo provides a preventive feedback mechanism which keeps the central disc light and produces slowly rising rotation curves without resorting to extreme feedback mechanisms. These preliminary results indicate that the effect of local photoionizing sources is significant and should not be ignored in models of galaxy formation.

  4. True 4D Image Denoising on the GPU

    PubMed Central

    Eklund, Anders; Andersson, Mats; Knutsson, Hans

    2011-01-01

    The use of image denoising techniques is an important part of many medical imaging applications. One common application is to improve the image quality of low-dose (noisy) computed tomography (CT) data. While 3D image denoising previously has been applied to several volumes independently, there has not been much work done on true 4D image denoising, where the algorithm considers several volumes at the same time. The problem with 4D image denoising, compared to 2D and 3D denoising, is that the computational complexity increases exponentially. In this paper we describe a novel algorithm for true 4D image denoising, based on local adaptive filtering, and how to implement it on the graphics processing unit (GPU). The algorithm was applied to a 4D CT heart dataset of the resolution 512  × 512  × 445  × 20. The result is that the GPU can complete the denoising in about 25 minutes if spatial filtering is used and in about 8 minutes if FFT-based filtering is used. The CPU implementation requires several days of processing time for spatial filtering and about 50 minutes for FFT-based filtering. The short processing time increases the clinical value of true 4D image denoising significantly. PMID:21977020

  5. True 4D Image Denoising on the GPU.

    PubMed

    Eklund, Anders; Andersson, Mats; Knutsson, Hans

    2011-01-01

    The use of image denoising techniques is an important part of many medical imaging applications. One common application is to improve the image quality of low-dose (noisy) computed tomography (CT) data. While 3D image denoising previously has been applied to several volumes independently, there has not been much work done on true 4D image denoising, where the algorithm considers several volumes at the same time. The problem with 4D image denoising, compared to 2D and 3D denoising, is that the computational complexity increases exponentially. In this paper we describe a novel algorithm for true 4D image denoising, based on local adaptive filtering, and how to implement it on the graphics processing unit (GPU). The algorithm was applied to a 4D CT heart dataset of the resolution 512  × 512  × 445  × 20. The result is that the GPU can complete the denoising in about 25 minutes if spatial filtering is used and in about 8 minutes if FFT-based filtering is used. The CPU implementation requires several days of processing time for spatial filtering and about 50 minutes for FFT-based filtering. The short processing time increases the clinical value of true 4D image denoising significantly.

  6. 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

  7. Systematic Comparison of Photoionized Plasma Codes with Application to Spectroscopic Studies of AGN in X-Rays

    NASA Technical Reports Server (NTRS)

    Mehdipour, M.; Kaastra, J. S.; Kallman, T.

    2016-01-01

    Atomic data and plasma models play a crucial role in the diagnosis and interpretation of astrophysical spectra, thus influencing our understanding of the Universe. In this investigation we present a systematic comparison of the leading photoionization codes to determine how much their intrinsic differences impact X-ray spectroscopic studies of hot plasmas in photoionization equilibrium. We carry out our computations using the Cloudy, SPEX, and XSTAR photoionization codes, and compare their derived thermal and ionization states for various ionizing spectral energy distributions. We examine the resulting absorption-line spectra from these codes for the case of ionized outflows in active galactic nuclei. By comparing the ionic abundances as a function of ionization parameter, we find that on average there is about 30 deviation between the codes in where ionic abundances peak. For H-like to B-like sequence ions alone, this deviation in is smaller at about 10 on average. The comparison of the absorption-line spectra in the X-ray band shows that there is on average about 30 deviation between the codes in the optical depth of the lines produced at log 1 to 2, reducing to about 20 deviation at log 3. We also simulate spectra of the ionized outflows with the current and upcoming high-resolution X-ray spectrometers, on board XMM-Newton, Chandra, Hitomi, and Athena. From these simulations we obtain the deviation on the best-fit model parameters, arising from the use of different photoionization codes, which is about 10 to40. We compare the modeling uncertainties with the observational uncertainties from the simulations. The results highlight the importance of continuous development and enhancement of photoionization codes for the upcoming era of X-ray astronomy with Athena.

  8. 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.

  9. Bootstrapping mixed correlators in 4D N = 1 SCFTs

    NASA Astrophysics Data System (ADS)

    Li, Daliang; Meltzer, David; Stergiou, Andreas

    2017-07-01

    The numerical conformal bootstrap is used to study mixed correlators in N = 1 superconformal field theories (SCFTs) in d = 4 spacetime dimensions. Systems of fourpoint functions involving scalar chiral and real operators are analyzed, including the case where the scalar real operator is the zero component of a global conserved current multiplet. New results on superconformal blocks as well as universal constraints on the space of 4D N = 1 SCFTs with chiral operators are presented. At the level of precision used, the conditions under which the putative "minimal" 4D N = 1 SCFT may be isolated into a disconnected allowed region remain elusive. Nevertheless, new features of the bounds are found that provide further evidence for the presence of a special solution to crossing symmetry corresponding to the "minimal" 4D N = 1 SCFT.

  10. 2D:4D Ratio and its Implications in Medicine.

    PubMed

    Jeevanandam, Saravanakumar; Muthu, Prathibha K

    2016-12-01

    Digit ratios, especially 2D:4D ratio, a potential proxy marker for prenatal androgen exposure shows sexual dimorphism. Existing literature and recent research show accumulating evidence on 2D:4D ratio showing correlations with various phenotypic traits in humans. Ratio of 2D:4D is found to correlate negatively to testosterone and positively to oestrogen in the foetus. Interestingly, it is constant since birth and not influenced by the adult hormone levels. Usually, males have lower ratios when compared to females. Prenatal androgen exposure and therefore, digit ratios have been reported to be associated with numerical competencies, spatial skills, handedness, cognitive abilities, academic performance, sperm counts, personalities and prevalence of obesity, migraine, eating disorders, depression, myopia, autism etc. The authors have attempted to write a brief account on the digit ratios and the dimorphism observed in various physiological, psychological and behavioural traits. Also, the authors have discussed the relevant molecular basics and the methods of measurement of digit ratios.

  11. 3D/4D sonography - any safety problem.

    PubMed

    Pooh, Ritsuko K; Maeda, Kazuo; Kurjak, Asim; Sen, Cihat; Ebrashy, Alaa; Adra, Abdallah; Dayyabu, Aliyu Labaran; Wataganara, Tuangsit; de Sá, Renato Augusto Moreira; Stanojevic, Milan

    2016-03-01

    Gray-scale image data are processed in 3D ultrasound by repeated scans of multiple planes within a few seconds to achieve one surface rendering image and three perpendicular plane images. The 4D image is achieved by repeating 3D images in short intervals, i.e. 3D and 4D ultrasound are based on simple B-mode images. During 3D/4D acquisition, a fetus in utero is exposed by ultrasound beam for only a few seconds, and it is as short as real-time B-mode scanning. Therefore, simple 3D imaging is as safe as a simple B-mode scan. The 4D ultrasound is also as safe as a simple B-mode scan, but the ultrasound exposure should be shorter than 30 min. The thermal index (TI) and mechanical index (MI) should both be lower than 1.0, and the ultrasound study is regulated by the Doppler ultrasound if it is combined with simple 3D or 4D ultrasound. Recently, some articles have reported the functional changes of animal fetal brain neuronal cells and liver cell apoptosis with Doppler ultrasound. We discuss cell apoptosis by ultrasound in this report. Diagnostic ultrasound safety is achieved by controlling the output pulse and continuous ultrasound waves using thermal and mechanical indices, which should be <1.0 in abdominal and transvaginal scan, pulsed Doppler, as well as 3D and 4D ultrasound. The lowest spatial peak temporal average (SPTA) intensity of the ultrasound to suppress cultured cell growth is 240 mW/cm2, below which no ultrasound effect has been reported. An ultrasound user must be trained to recognize the ultrasound bioeffects; thermal and mechanical indices, and how to reduce these when they are higher than 1.0 on the monitor display; and guide the proper use of the ultrasound under the ALARA principle, because the user is responsible for ensuring ultrasound safety.

  12. 4D imaging of protein aggregation in live cells.

    PubMed

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

    2013-04-05

    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.

  13. 4D Imaging of Protein Aggregation in Live Cells

    PubMed Central

    Kaganovich, Daniel

    2013-01-01

    proteins that are not 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 protein10-12 (Ubc9ts) is extremely effective both as a sensor of cellular proteostasis, and a physiological model for tracking aggregation quality control. As with most ts proteins, Ubc9ts is fully folded and functional at permissive temperatures due to active cellular chaperones. Above 30 °C, or when the cell faces misfolding stress, Ubc9ts 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

  14. 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.

  15. Design of Laboratory Experiments to Study Photoionization Fronts

    NASA Astrophysics Data System (ADS)

    Gray, William James; Davis, Josh; Drake, R. Paul

    2017-06-01

    Here we present the theoretical foundation for a laboratory experiment to study photoionization fronts. Photoionization fronts play important roles in the formation and evolution of structure in the Universe. A properly designed experiment will have to control the recombination rate, electron impact ionization rate, and the initial thermal spectrum. We show that such an experiment can be designed, but requires the use of the largest high-energy-density laser facilities, such as Omega, Z, and NIF. We also show that prior experiments do not actually generate photoionization fronts, rather a heat front is produced by heat conductions. We show some initial simulation results of the current experimental design and characterize the ionization front.

  16. Depth-resolved subcycle dynamics of photoionization in solids

    NASA Astrophysics Data System (ADS)

    Zhokhov, P. A.; Zheltikov, A. M.

    2017-09-01

    We develop a theoretical framework for the analysis of ultrafast dynamics of photoionization in solids that treats the electron density buildup resolved within the field cycle jointly with the propagation dynamics of the laser driver. We show that while the standard, cycle-averaging photoionization models predict a monotonic buildup of the electron density within the driver pulse, the cycle-resolved photoionization model used in this work reveals a subcycle modulation of optical properties of a solid, giving rise to complex patterns of reflected and transmitted fields and providing a source for optical harmonic generation. Propagation effects are shown to heavily distort the spectra of high-order harmonics. Still, the analysis of harmonic spectra and the temporal structure of the harmonic field reveals physically significant properties of the nonlinear-optical response, suggesting the existence of attosecond bursts of interband optical-harmonic emission.

  17. 4D ultrasound imaging - ethically justifiable in India?

    PubMed

    Indiran, Venkatraman

    2017-01-01

    Four-dimensional (4D) ultrasound (real-time volume sonography), which has been used in the West since the last decade for the determination of gender as well as for bonding and entertainment of the parents, has become widely available in India in this decade. Here, I would like to discuss the ethical issues associated with 4D ultrasonography in India. These are self-referral, the use of the technology for non-medical indications, a higher possibility of the disclosure of the foetus' gender and safety concerns.

  18. 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

  19. 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.

  20. 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.

  1. Application of sampling theory in modelling of continuum processes: photoionization cross-sections of atoms

    NASA Astrophysics Data System (ADS)

    Kozlov, A.; Saha, S.; Quiney, H. M.

    2017-01-01

    We describe a method for the calculation of photoionization cross-sections using square-integrable amplitudes obtained from the diagonalization of finite-basis set representations of the electronic Hamiltonian. Three examples are considered: a model example in which the final state is a free particle, the hydrogen atom and neutral atomic sodium. The method exploits the Whittaker-Shannon-Kotel’nikov sampling theorem, which is widely used in digital signal sampling and reconstruction. The approach reproduces known data with very good accuracy and converges to the exact solution with increase of the basis set size.

  2. Resonant and Near-Threshold Photoionization Cross Sections of Fe{sup 14+}

    SciTech Connect

    Simon, M. C.; Crespo Lopez-Urrutia, J. R.; Beilmann, C.; Schwarz, M.; Epp, S. W.; Schmitt, B. L.; Baumann, T. M.; Bernitt, S.; Ginzel, R.; Keitel, C. H.; Klawitter, R.; Kubicek, K.; Maeckel, V.; Mokler, P. H.; Ullrich, J.; Harman, Z.; Behar, E.; Follath, R.; Reichardt, G.; Schwarzkopf, O.

    2010-10-29

    Photoionization (PI) of Fe{sup 14+} in the range from 450 to 1100 eV was measured at the BESSY II storage ring using an electron beam ion trap achieving high target-ion area densities of 10{sup 10} cm{sup -2}. Photoabsorption by this ion is observed in astrophysical spectra and plasmas, but until now cross sections and resonance energies could only be provided by calculations. We reach a resolving power E/{Delta}E of at least 6500, outstanding in the present energy range, which enables benchmarking and improving the most advanced theories for PI of ions in high charge states.

  3. Total and dissociative photoionization cross sections of N2 from threshold to 107 eV

    NASA Technical Reports Server (NTRS)

    Samson, James A. R.; Masuoka, T.; Pareek, P. N.; Angel, G. C.

    1986-01-01

    The absolute cross sections for the production of N(+) and N2(+) were measured from the dissociative ionization threshold of 115 A. In addition, the absolute photoabsorption and photoionization cross sections were tabulated between 114 and 796 A. The ionization efficiencies were also given at several discrete wave lengths between 660 and 790 A. The production of N(+) fragment ions are discussed in terms of the doubly excited N2(+) states with binding energies in the range of 24 to 44 eV.

  4. Electronic decoherence following photoionization: Full quantum-dynamical treatment of the influence of nuclear motion

    NASA Astrophysics Data System (ADS)

    Arnold, Caroline; Vendrell, Oriol; Santra, Robin

    2017-03-01

    Photoionization using attosecond pulses can lead to the formation of coherent superpositions of the electronic states of the parent ion. However, ultrafast electron ejection triggers not only electronic but also nuclear dynamics—leading to electronic decoherence, which is typically neglected on time scales up to tens of femtoseconds. We propose a full quantum-dynamical treatment of nuclear motion in an adiabatic framework, where nuclear wave packets move on adiabatic potential energy surfaces expanded up to second order at the Franck-Condon point. We show that electronic decoherence is caused by the interplay of a large number of nuclear degrees of freedom and by the relative topology of the potential energy surfaces. Application to H2O , paraxylene, and phenylalanine shows that an initially coherent state evolves to an electronically mixed state within just a few femtoseconds. In these examples the fast vibrations involving hydrogen atoms do not affect electronic coherence at short times. Conversely, vibrational modes involving the whole molecular skeleton, which are slow in the ground electronic state, quickly destroy it upon photoionization.

  5. Vibrationally Resolved B 1s Photoionization Cross Section of BF3.

    PubMed

    Ayuso, D; Kimura, M; Kooser, K; Patanen, M; Plésiat, E; Argenti, L; Mondal, S; Travnikova, O; Sakai, K; Palacios, A; Kukk, E; Decleva, P; Ueda, K; Martín, F; Miron, C

    2015-06-11

    Photoelectron diffraction is a well-established technique for structural characterization of solids, based on the interference of the native photoelectron wave with those scattered from the neighboring atoms. For isolated systems in the gas phase similar studies suffer from orders of magnitude lower signals due to the very small sample density. Here we present a detailed study of the vibrationally resolved B 1s photoionization cross section of BF3 molecule. A combination of high-resolution photoelectron spectroscopy measurements and of state-of-the-art static-exchange and time-dependent DFT calculations shows the evolution of the photon energy dependence of the cross section from a complete trapping of the photoelectron wave (low energies) to oscillations due to photoelectron diffraction phenomena. The diffraction pattern allows one to access structural information both for the ground neutral state of the molecule and for the core-ionized cation. Due to a significant change in geometry between the ground and the B 1s(-1) core-ionized state in the BF3 molecule, several vibrational final states of the cation are populated, allowing investigation of eight different relative vibrationally resolved photoionization cross sections. Effects due to recoil induced by the photoelectron emission are also discussed.

  6. Vibrational branching ratios in the (b2u)-1 photoionization of C6F6

    NASA Astrophysics Data System (ADS)

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

    2009-07-01

    The vibrational branching ratios in the photoionization of C6F6 leading to the CB22u state of C6F6+ 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 σ 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.

  7. Experimental study of the degradation of 2,4-D induced by vacuum-UV radiation.

    PubMed

    Imoberdorf, G E; Mohseni, M

    2011-01-01

    Vacuum-UV (VUV) photoinduced degradation of the herbicide 2,4-D was studied. A flow-through VUV photoreactor was used (i) in batch mode to study the kinetics of degradation and (ii) in continuous mode under steady state to analyze the potential utilization of this process in commercial applications. In both cases, the reactants were recycled to minimize diffusive resistances. Experimental results from the batch studies showed that the initial degradation rate of 2,4-D in ultrapure water was independent of the initial concentration of the herbicide. However, a reduction in the reaction rate was obtained over the course of the treatment, largely due to the formation of 2,4-D partial oxidation by-products which compete with 2,4-D molecules for HO (scavenging effect). Increases in water alkalinity reduced 2,4-D degradation rate as a consequence of the scavenging of HO by carbonates and bicarbonates. The degradation of 2,4-D in raw surface waters was also investigated. A noticeable reduction in the degradation rate was observed because of the presence of NOM and alkalinity, both being known HO scavengers. Additionally, the presence of inorganic species/ions that absorb VUV may also have contributed to the reduction of the overall degradation rate. High conversions were obtained in the continuous system. At a residence time of 25 seconds, conversions of 97% and 65% were achieved for inlet herbicide concentrations of 1 and 10 mg L(-1), respectively. Under these conditions, the received dose of 185 nm radiation was 44.8 mJ cm(-2).

  8. Absolute Photoionization Cross Sections of Two Cyclic Ketones: Cyclopentanone & Cyclohexanone.

    PubMed

    Price, Chelsea; Fathi, Yasmin; Meloni, Giovanni

    2017-02-23

    Absolute photoionization cross sections for cyclopentanone and cyclohexanone, as well as partial ionization cross sections for the dissociative ionized fragments, are presented in this investigation. Experiments are performed via a multiplexed photoionization mass spectrometer utilizing VUV synchrotron radiation supplied by the Advanced Light Source of Lawrence Berkeley National Laboratory. These results allow the quantification of these species that is relevant to investigate the kinetics and combustion reactions of potential biofuels. The CBS-QB3 calculated values for the adiabatic ionization energies agree well with the experimental values and the identification of possible dissociative fragments is discussed for both systems.

  9. Atmospheric pressure photoionization using tunable VUV synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Giuliani, A.; Giorgetta, J.-L.; Ricaud, J.-P.; Jamme, F.; Rouam, V.; Wien, F.; Laprévote, O.; Réfrégiers, M.

    2012-05-01

    We report here the first coupling of an atmospheric pressure photoionization (APPI) source with a synchrotron radiation beamline in the vacuum ultra-violet (VUV). A commercial APPI source of a QStar Pulsar i from AB Sciex was modified to receive photons from the DISCO beamline at the SOLEIL synchrotron radiation facility. Photons are delivered at atmospheric pressure in the 4-20 eV range. The advantages of this new set up, termed SR-APPI, over classical APPI are spectral purity and continuous tunability. The technique may also be used to perform tunable photoionization mass spectrometry on fragile compounds difficult to vaporize by classical methods.

  10. 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

  11. The technology and performance of 4D ultrasound.

    PubMed

    Obruchkov, Sergei

    2008-01-01

    Recent developments in 4D ultrasound imaging technology allow clinicians to obtain not only rich visual information but also quantitative data that can be used for diagnosis and treatment. Some argue that the extension of 2D ultrasound is unnecessary and does not offer any benefits to diagnosis, while others argue that it is possible to better assess an abnormality in 3D than 2D. Anatomy can be reconstructed in perspectives that were never seen with conventional 2D US imaging. Advanced rendering techniques in three dimensions can be customized to be sensitive to specific pathology, thus making diagnosis more accurate. Volume and function of certain anatomical components can be measured with greater accuracy. This article reviews physical principles behind the ultrasound technology, how they are applied to advance the field of ultrasound imaging, and maybe reach its limits. Advances in ultrasound technology make 4D ultrasound imaging faster and less dependent on the operator's expertise, thus opening up more research possibilities in the fields of data processing and visualization. Currently, 4D ultrasound is extensively used in the field of obstetrics and interven-tional radiology. The goal of 4D ultrasound is to overcome the limitations posed by its predecessor technology and to be more clinically useful as an imaging tool.

  12. 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.

  13. 76 FR 55814 - 2,4-D; Pesticide Tolerances

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-09

    ...: Final rule. SUMMARY: This regulation establishes tolerances for residues of 2,4-D in or on teff, bran; teff, forage; teff, grain; and teff, straw. Interregional Research Project Number 4 (IR-4) requested...-dichlorophenoxyacetic acid), both free and conjugated, determined as the acid, in or on teff, bran at 4.0 parts per...

  14. 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

  15. Cotton stage of growth determines sensitivityto 2,4-D

    USDA-ARS?s Scientific Manuscript database

    The impending release of EnlistTM cotton and soybean cultivars likely will increase the use of 2,4-D, which has raised concerns over potential injury to susceptible cotton. An experiment was conducted at 12 locations across the cotton belt during 2013 and 2014 to determine the impact of a simulated...

  16. 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

  17. A quantum-rovibrational-state-selected study of the proton-transfer reaction H2(+)(X(2)Σ: v(+) = 1-3; N(+) = 0-3) + Ne → NeH(+) + H using the pulsed field ionization-photoion method: observation of the rotational effect near the reaction threshold.

    PubMed

    Xiong, Bo; Chang, Yih-Chung; Ng, Cheuk-Yiu

    2017-07-19

    Using the sequential electric field pulsing scheme for vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) detection, we have successfully prepared H2(+)(X(2)Σ: v(+) = 1-3; N(+) = 0-5) ions in the form of an ion beam in single quantum-rovibrational-states with high purity, high intensity, and narrow laboratory kinetic energy spread (ΔElab ≈ 0.05 eV). This VUV-PFI-PI ion source, when coupled with the double-quadrupole double-octupole ion-molecule reaction apparatus, has made possible a systematic examination of the vibrational- as well as rotational-state effects on the proton transfer reaction of H2(+)(X(2)Σ: v(+); N(+)) + Ne. Here, we present the integral cross sections [σ(v(+); N(+))'s] for the H2(+)(v(+) = 1-3; N(+) = 0-3) + Ne → NeH(+) + H reaction observed in the center-of-mass kinetic energy (Ecm) range of 0.05-2.00 eV. The σ(v(+) = 1, N(+) = 1) exhibits a distinct Ecm onset, which is found to agree with the endothermicity of 0.27 eV for the proton transfer process after taking into account of experimental uncertainties. Strong v(+)-vibrational enhancements are observed for σ(v(+) = 1-3, N(+)) in the Ecm range of 0.05-2.00 eV. While rotational excitations appear to have little effect on σ(v(+) = 3, N(+)), a careful search leads to the observation of moderate N(+)-rotational enhancements at v(+) = 2: σ(v(+) = 2; N(+) = 0) < σ(v(+) = 2; N(+) = 1) < σ(v(+) = 2; N(+) = 2) < σ(v(+) = 2; N(+) = 3), where the formation of NeH(+) is near thermal-neutral. The σ(v(+) = 1-3, N(+) = 0-3) values obtained here are compared with previous experimental results and the most recent state-of-the-art quantum dynamics predictions. We hope that these new experimental results would further motivate more rigorous theoretical calculations on the dynamics of this prototypical ion-molecule reaction.

  18. 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

  19. Registration of 4D cardiac CT sequences under trajectory constraints with multichannel diffeomorphic demons.

    PubMed

    Peyrat, Jean-Marc; Delingette, Hervé; Sermesant, Maxime; Xu, Chenyang; Ayache, Nicholas

    2010-07-01

    We propose a framework for the nonlinear spatiotemporal registration of 4D time-series of images based on the Diffeomorphic Demons (DD) algorithm. In this framework, the 4D spatiotemporal registration is decoupled into a 4D temporal registration, defined as mapping physiological states, and a 4D spatial registration, defined as mapping trajectories of physical points. Our contribution focuses more specifically on the 4D spatial registration that should be consistent over time as opposed to 3D registration that solely aims at mapping homologous points at a given time-point. First, we estimate in each sequence the motion displacement field, which is a dense representation of the point trajectories we want to register. Then, we perform simultaneously 3D registrations of corresponding time-points with the constraints to map the same physical points over time called the trajectory constraints. Under these constraints, we show that the 4D spatial registration can be formulated as a multichannel registration of 3D images. To solve it, we propose a novel version of the Diffeomorphic Demons (DD) algorithm extended to vector-valued 3D images, the Multichannel Diffeomorphic Demons (MDD). For evaluation, this framework is applied to the registration of 4D cardiac computed tomography (CT) sequences and compared to other standard methods with real patient data and synthetic data simulated from a physiologically realistic electromechanical cardiac model. Results show that the trajectory constraints act as a temporal regularization consistent with motion whereas the multichannel registration acts as a spatial regularization. Finally, using these trajectory constraints with multichannel registration yields the best compromise between registration accuracy, temporal and spatial smoothness, and computation times. A prospective example of application is also presented with the spatiotemporal registration of 4D cardiac CT sequences of the same patient before and after radiofrequency

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. Combined convective and diffusive simulations: VERB-4D comparison with 17 March 2013 Van Allen Probes observations: VERB-4D

    DOE PAGES

    Shprits, Yuri Y.; Kellerman, Adam C.; Drozdov, Alexander Y.; ...

    2015-11-19

    Our study focused on understanding the coupling between different electron populations in the inner magnetosphere and the various physical processes that determine evolution of electron fluxes at different energies. Observations during the 17 March 2013 storm and simulations with a newly developed Versatile Electron Radiation Belt-4D (VERB-4D) are presented. This analysis of the drift trajectories of the energetic and relativistic electrons shows that electron trajectories at transitional energies with a first invariant on the scale of ~100 MeV/G may resemble ring current or relativistic electron trajectories depending on the level of geomagnetic activity. Simulations with the VERB-4D code including convection,more » radial diffusion, and energy diffusion are presented. Sensitivity simulations including various physical processes show how different acceleration mechanisms contribute to the energization of energetic electrons at transitional energies. In particular, the range of energies where inward transport is strongly influenced by both convection and radial diffusion are studied. Our results of the 4-D simulations are compared to Van Allen Probes observations at a range of energies including source, seed, and core populations of the energetic and relativistic electrons in the inner magnetosphere.« less

  6. Combined convective and diffusive simulations: VERB-4D comparison with 17 March 2013 Van Allen Probes observations: VERB-4D

    SciTech Connect

    Shprits, Yuri Y.; Kellerman, Adam C.; Drozdov, Alexander Y.; Spence, Harlan E.; Reeves, Geoffrey D.; Baker, Daniel N.

    2015-11-19

    Our study focused on understanding the coupling between different electron populations in the inner magnetosphere and the various physical processes that determine evolution of electron fluxes at different energies. Observations during the 17 March 2013 storm and simulations with a newly developed Versatile Electron Radiation Belt-4D (VERB-4D) are presented. This analysis of the drift trajectories of the energetic and relativistic electrons shows that electron trajectories at transitional energies with a first invariant on the scale of ~100 MeV/G may resemble ring current or relativistic electron trajectories depending on the level of geomagnetic activity. Simulations with the VERB-4D code including convection, radial diffusion, and energy diffusion are presented. Sensitivity simulations including various physical processes show how different acceleration mechanisms contribute to the energization of energetic electrons at transitional energies. In particular, the range of energies where inward transport is strongly influenced by both convection and radial diffusion are studied. Our results of the 4-D simulations are compared to Van Allen Probes observations at a range of energies including source, seed, and core populations of the energetic and relativistic electrons in the inner magnetosphere.

  7. 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

  8. SU-E-T-790: Validation of 4D Measurement-Guided Dose Reconstruction (MGDR) with OCTAVIUS 4D System

    SciTech Connect

    Lee, V; Leung, R; Wong, M; Law, G; Lee, K; Tung, S; Chan, M; Blanck, O

    2015-06-15

    Purpose: To validate the MGDR of OCTAVIUS 4D system (PTW, Freiburg, Germany) for quality assurance (QA) of volumetric-modulated arc radiotherapy (VMAT). Methods: 4D-MGDR measurements were divided into two parts: 1) square fields from 2×2 to 25×25 cm{sup 2} at 0°, 10° and 45° gantry, and 2) 8 VMAT plans (5 nasopharyngeal and 3 prostate) collapsed to gantry 40° in QA mode in Monaco v5.0 (Elekta, CMS, Maryland Heights, MO) were delivered on the OCTAVIUS 4D phantom with the OCTAVIUS 1500 detector plane perpendicular to either the incident beam to obtain the reconstructed dose (OCTA4D) or the 0° gantry axis to obtain the raw doses (OCTA3D) in Verisoft 6.1 (PTW, Freiburg, Germany). Raw measurements of OCTA3D were limited to < 45° gantry to avoid >0.5% variation of detector angular response with respect to 0° gantry as determined previously. Reconstructed OCTA4D and raw OCTA3D doses for all plans were compared at the same detector plane using γ criteria of 2% (local dose)/2mm and 3%/3mm criteria. Results: At gantry 0° and 10°, the γ results for all OCTA4D on detector plane coinciding with OCTA3D were over 90% at 2%/2mm except for the largest field (25×25 cm{sup 2} ) showing >88%. For square field at 45° gantry, γ passing rate is > 90% for fields smaller than 15x 15cm2 but < 80% for field size of 20 x20 cm{sup 2} upward. For VMAT, γ results showed 94% and 99% passing rate at 2%/2mm and 3%/3mm, respectively. Conclusion: OCTAVIUS 4D system has compromised accuracy in reconstructing dose away from the central beam axis, possibly due to the off-axis softening correction and errors of the percent depth dose data necessary as input for MGDR. Good results in VMAT delivery suggested that the system is relatively reliable for VMAT with small segments.

  9. Improved Respiratory Navigator Gating for Thoracic 4D flow MRI

    PubMed Central

    van Ooij, Pim; Semaan, Edouard; Schnell, Susanne; Giri, Shivraman; Stankovic, Zoran; Carr, James; Barker, Alex J.; Markl, Michael

    2016-01-01

    Background Thoracic and abdominal 4D flow MRI is typically acquired in combination with navigator respiration control which can result in highly variable scan efficiency (Seff) and thus total scan time due to inter-individual variability in breathing patterns. The aim of this study was to test the feasibility of an improved respiratory control strategy based on diaphragm navigator gating with fixed Seff, respiratory driven phase encoding, and a navigator training phase. Methods 4D flow MRI of the thoracic aorta was performed in 10 healthy subjects at 1.5T and 3T systems for the in-vivo assessment of aortic time-resolved 3D blood flow velocities. For each subject, four 4D flow scans (1: conventional navigator gating, 2–4: new implementation with fixed Seff =60%, 80% and 100%) were acquired. Data analysis included semi-quantitative evaluation of image quality of the 4D flow magnitude images (image quality grading on a four point scale), 3D segmentation of the thoracic aorta, and voxel-by-voxel comparisons of systolic 3D flow velocity vector fields between scans. Results Conventional navigator gating resulted in variable Seff = 74±13% (range = 56% – 100%) due to inter-individual variability of respiration patterns. For scans 2–4, the the new navigator implementation was able to achieve predictable total scan times with stable Seff, only depending on heart rate. Semi- and fully quantitative analysis of image quality in 4D flow magnitude images was similar for the new navigator scheme compared to conventional navigator gating. For aortic systolic 3D velocities, good agreement was found between all new navigator settings (scan 2–4) with the conventional navigator gating (scan 1) with best performance for Seff = 80% (mean difference = −0.01; limits od agreement = 0.23, Pearson’s ρ=0.89, p <0.001). No significant differences for image quality or 3D systolic velocities were found for 1.5T compared to 3T. Conclusions The findings of this study demonstrate the

  10. 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

  11. 4D CT sorting based on patient internal anatomy

    NASA Astrophysics Data System (ADS)

    Li, Ruijiang; Lewis, John H.; Cerviño, Laura I.; Jiang, Steve B.

    2009-08-01

    Respiratory motion during free-breathing computed tomography (CT) scan may cause significant errors in target definition for tumors in the thorax and upper abdomen. A four-dimensional (4D) CT technique has been widely used for treatment simulation of thoracic and abdominal cancer radiotherapy. The current 4D CT techniques require retrospective sorting of the reconstructed CT slices oversampled at the same couch position. Most sorting methods depend on external surrogates of respiratory motion recorded by extra instruments. However, respiratory signals obtained from these external surrogates may not always accurately represent the internal target motion, especially when irregular breathing patterns occur. We have proposed a new sorting method based on multiple internal anatomical features for multi-slice CT scan acquired in the cine mode. Four features are analyzed in this study, including the air content, lung area, lung density and body area. We use a measure called spatial coherence to select the optimal internal feature at each couch position and to generate the respiratory signals for 4D CT sorting. The proposed method has been evaluated for ten cancer patients (eight with thoracic cancer and two with abdominal cancer). For nine patients, the respiratory signals generated from the combined internal features are well correlated to those from external surrogates recorded by the real-time position management (RPM) system (average correlation: 0.95 ± 0.02), which is better than any individual internal measures at 95% confidence level. For these nine patients, the 4D CT images sorted by the combined internal features are almost identical to those sorted by the RPM signal. For one patient with an irregular breathing pattern, the respiratory signals given by the combined internal features do not correlate well with those from RPM (correlation: 0.68 ± 0.42). In this case, the 4D CT image sorted by our method presents fewer artifacts than that from the RPM signal. Our

  12. Protonation enhancement by dichloromethane doping in low-pressure photoionization

    NASA Astrophysics Data System (ADS)

    Shu, Jinian; Zou, Yao; Xu, Ce; Li, Zhen; Sun, Wanqi; Yang, Bo; Zhang, Haixu; Zhang, Peng; Ma, Pengkun

    2016-12-01

    Doping has been used to enhance the ionization efficiency of analytes in atmospheric pressure photoionization, which is based on charge exchange. Compounds with excellent ionization efficiencies are usually chosen as dopants. In this paper, we report a new phenomenon observed in low-pressure photoionization: Protonation enhancement by dichloromethane (CH2Cl2) doping. CH2Cl2 is not a common dopant due to its high ionization energy (11.33 eV). The low-pressure photoionization source was built using a krypton VUV lamp that emits photons with energies of 10.0 and 10.6 eV and was operated at ~500–1000 Pa. Protonation of water, methanol, ethanol, and acetaldehyde was respectively enhanced by 481.7 ± 122.4, 197.8 ± 18.8, 87.3 ± 7.8, and 93.5 ± 35.5 times after doping 291 ppmv CH2Cl2, meanwhile CH2Cl2 almost does not generate noticeable ions itself. This phenomenon has not been documented in the literature. A new protonation process involving in ion-pair and H-bond formations was proposed to expound the phenomenon. The observed phenomenon opens a new prospect for the improvement of the detection efficiency of VUV photoionization.

  13. Protonation enhancement by dichloromethane doping in low-pressure photoionization

    PubMed Central

    Shu, Jinian; Zou, Yao; Xu, Ce; Li, Zhen; Sun, Wanqi; Yang, Bo; Zhang, Haixu; Zhang, Peng; Ma, Pengkun

    2016-01-01

    Doping has been used to enhance the ionization efficiency of analytes in atmospheric pressure photoionization, which is based on charge exchange. Compounds with excellent ionization efficiencies are usually chosen as dopants. In this paper, we report a new phenomenon observed in low-pressure photoionization: Protonation enhancement by dichloromethane (CH2Cl2) doping. CH2Cl2 is not a common dopant due to its high ionization energy (11.33 eV). The low-pressure photoionization source was built using a krypton VUV lamp that emits photons with energies of 10.0 and 10.6 eV and was operated at ~500–1000 Pa. Protonation of water, methanol, ethanol, and acetaldehyde was respectively enhanced by 481.7 ± 122.4, 197.8 ± 18.8, 87.3 ± 7.8, and 93.5 ± 35.5 times after doping 291 ppmv CH2Cl2, meanwhile CH2Cl2 almost does not generate noticeable ions itself. This phenomenon has not been documented in the literature. A new protonation process involving in ion-pair and H-bond formations was proposed to expound the phenomenon. The observed phenomenon opens a new prospect for the improvement of the detection efficiency of VUV photoionization. PMID:27905552

  14. Photodissociation of Acetaldehyde and the Photoionization Cross Section of HCO

    NASA Astrophysics Data System (ADS)

    Shubert, V. Alvin; Pratt, Stephen T.

    2010-06-01

    Acetaldehyde was photodissociated with near UV laser light, and the methyl (CH_3) and formyl (HCO) radical fragments were photoionized with vacuum ultraviolet (VUV) light. The fragments were detected by using both time of flight mass spectrometry and velocity ion map imaging. With the former technique, simultaneous detection of both fragments provided the intensity of HCO+ relative to CH_3+ with I(HCO+)/I(CH_3+) ≈ 0.8. Because the absolute photoionization cross section of the CH_3 radical has been characterized (≈ 5 Mb) at the VUV energies of interest, the absolute photoionization cross section of HCO could be determined from the intensity ratio, yielding an HCO cross section of ≈ 4 Mb at 10.3 eV. However, because some of the HCO fragments could be formed with enough internal energy to undergo secondary dissociation, velocity ion map imaging was employed to determine the extent of any secondary dissociation that occurred. The translational energy distributions obtained for both the CH_3 and HCO fragments are nearly identical, indicating that no HCO fragments underwent secondary dissociation. A surprising result was the smaller photoionization cross section of HCO relative to CH_3. Comparison to the isoelectronic species of NO will be discussed and a potential explanation will be offered for this observation. This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under contract No. DE-AC02-06CH11357.

  15. Dissociative photoionization of ethyl acrylate: Theoretical and experimental insights

    NASA Astrophysics Data System (ADS)

    Song, Yanlin; Chen, Jun; Ding, Mengmeng; Wei, Bin; Cao, Maoqi; Shan, Xiaobin; Zhao, Yujie; Huang, Chaoqun; Sheng, Liusi; Liu, Fuyi

    2015-08-01

    The photoionization and dissociation of ethyl acrylate have been investigated by time-of-flight mass spectrometer with tunable vacuum ultraviolet (VUV) source in the range of 9.0-20.0 eV. The photoionization mass spectrum (PIMS) for ethyl acrylate and photoionization efficiency (PIE) curves for its major fragment ions: C5H7O2+, C4H5O2+, C3H5O2+, C3H4O+, C3H3O+, C2H5O+, C2H3O+, C2H5+ and C2H4+ have been obtained. The formation channels of main fragments are predicted by Gaussian 09 program at G3B3 level and examined via their dissociation energies from experimental results. Based on our analysis, nine main dissociative photoionization channels are proposed: C5H7O2+ + H, C4H5O2+ + CH3, C3H5O2+ + C2H3, C3H4O+ + C2H4O, C3H3O+ + C2H5O, C2H5O+ + C3H3O, C2H3O+ + C3H5O, C2H5+ + C3H3O2, C2H4+ + C3H4O2, respectively. The results of this work lead to a better understanding of photochemistry in the environment.

  16. Electron scattering from and photoionization of open- shell atoms

    NASA Astrophysics Data System (ADS)

    Lin, Dong

    1999-09-01

    The multiconfiguration Hartree-Fock (MCHF) approach, developed by Dr. H. P. Saha et al, has been proved to be extremely successful in the past few years in reproducing experimental results at a very high level of accuracy. The research projects we are interested consist of two areas. In the first area we performed ab initio calculations on elastic scattering of electrons from open-shell sulfur atoms. In the second area, in order to understand the electronic dynamics in photoionization of atoms, we carried out accurate calculations on valence and K-shell photoionization of three-electron systems from lithium through neon for photon energies from threshold to very high energies; to further identify the autoionization resonances which were observed near threshold and to understand the dynamics, we modifies the MCHF method to include relativistic effects and performed calculation on partial photoionization cross section, resonance structure and effect of spin-orbit interaction in photoionization of atomic bromine. The calculated results obtained in each of these investigations are compared with available experimental and theoretical data and are found to be in very good agreement. The research contribution made for the fulfillment of the degree, we understand, will be a valuable addition towards a better understanding of the open-shell systems.

  17. Correlation Effects in the Photoionization of Confined Calcium and Zinc

    NASA Astrophysics Data System (ADS)

    Varma, R. Hari; Manson, S. T.

    2005-05-01

    Studies of atoms confined in an endohedral environment have aroused significant recent interest [1]. In this work, the photoionization @Ca and @Zn have been studied using the Relativistic-Random-Phase Approximation, modified to include the confinement potential. Photoionization of the 4s and 3p subshells of free and confined atomic calcium, along with the 4s, 3d, 3p and 3s subshells of free and confined atomic zinc, have been studied. The photoionization parameters of confined atoms differ significantly from those of their ``free'' counterparts. The dipole cross sections and angular distribution asymmetry parameters exhibit oscillations with energy arising from the back scattering of the escaping electron by the confining potential, i.e., ``confinement resonances'' [2]. These oscillations persist when nondipole matrix elements are also included as is reflected in the nondipole cross section and angular distribution asymmetry parameters [3]; the relative strengths of the oscillations due to back-scattering in the E1 and E2 photoionization parameters have qualitatively different profiles as a function of photon energy. [1] V. K. Dolmatov, A. S. Baltenkov, J.-P. Connerade and S. T. Manson, Radiation Phys. Chem. 70, 417 (2004). [2] M. Ya. Amusia, A. S. Baltenkov, V. K. Dolmatov, S. T. Manson and A. Z. Msezane, Phys. Rev. A 70, 023201 (2004). [3] P.C. Deshmukh, Tanima Banerjee, K. P. Sunanda and R. Hari Varma, Radiation Phys. and Chem (submitted).

  18. Protonation enhancement by dichloromethane doping in low-pressure photoionization.

    PubMed

    Shu, Jinian; Zou, Yao; Xu, Ce; Li, Zhen; Sun, Wanqi; Yang, Bo; Zhang, Haixu; Zhang, Peng; Ma, Pengkun

    2016-12-01

    Doping has been used to enhance the ionization efficiency of analytes in atmospheric pressure photoionization, which is based on charge exchange. Compounds with excellent ionization efficiencies are usually chosen as dopants. In this paper, we report a new phenomenon observed in low-pressure photoionization: Protonation enhancement by dichloromethane (CH2Cl2) doping. CH2Cl2 is not a common dopant due to its high ionization energy (11.33 eV). The low-pressure photoionization source was built using a krypton VUV lamp that emits photons with energies of 10.0 and 10.6 eV and was operated at ~500-1000 Pa. Protonation of water, methanol, ethanol, and acetaldehyde was respectively enhanced by 481.7 ± 122.4, 197.8 ± 18.8, 87.3 ± 7.8, and 93.5 ± 35.5 times after doping 291 ppmv CH2Cl2, meanwhile CH2Cl2 almost does not generate noticeable ions itself. This phenomenon has not been documented in the literature. A new protonation process involving in ion-pair and H-bond formations was proposed to expound the phenomenon. The observed phenomenon opens a new prospect for the improvement of the detection efficiency of VUV photoionization.

  19. High-gain inner-shell photoionization laser in Cd vapor pumped by soft-x-ray radiation from a laser-produced plasma source.

    PubMed

    Silfvast, W T; Macklin, J J; Ii, O R

    1983-11-01

    A soft-x-ray-pumped inner-shell photoionization laser has been produced in Cd vapor at 4416 and 3250 A. A gain of 5.6 cm(-1) has been measured at 4416 A, and a reasonably high-energy storage of 0.2 mJ/cm(3) in the upper laser states has been obtained.

  20. 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.

  1. Total molecular photoionization cross-sections by algebraic diagrammatic construction-Stieltjes-Lanczos method: Benchmark calculations

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    In [K. Gokhberg, V. Vysotskiy, L. S. Cederbaum, L. Storchi, F. Tarantelli, and V. Averbukh, J. Chem. Phys. 130, 064104 (2009)] we introduced a new {L}2ab initio method for the calculation of total molecular photoionization cross-sections. The method is based on the ab initio description of discretized photoionized molecular 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. Here we establish the accuracy of the new technique by comparing the ADC-Lanczos-Stieltjes cross-sections in the valence ionization region to the experimental ones for a series of eight molecules of first row elements: HF, NH3, H2O, CO2, H2CO, CH4, C2H2, and C2H4. We find that the use of the second-order ADC technique [ADC(2)] that includes double electronic excitations leads to a substantial systematic improvement over the first-order method [ADC(1)] and to a good agreement with experiment for photon energies below 80 eV. The use of extended second-order ADC theory [ADC(2)x] leads to a smaller further improvement. Above 80 eV photon energy all three methods lead to significant deviations from the experimental values which we attribute to the use of Gaussian single-electron bases. Our calculations show that the ADC(2)-Lanczos-Stieltjes technique is a reliable and efficient ab initio tool for theoretical prediction of total molecular photo-ionization cross-sections in the valence region.

  2. Total molecular photoionization cross-sections by algebraic diagrammatic construction-Stieltjes-Lanczos method: benchmark calculations.

    PubMed

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

    2013-10-14

    In [K. Gokhberg, V. Vysotskiy, L. S. Cederbaum, L. Storchi, F. Tarantelli, and V. Averbukh, J. Chem. Phys. 130, 064104 (2009)] we introduced a new L(2) ab initio method for the calculation of total molecular photoionization cross-sections. The method is based on the ab initio description of discretized photoionized molecular 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. Here we establish the accuracy of the new technique by comparing the ADC-Lanczos-Stieltjes cross-sections in the valence ionization region to the experimental ones for a series of eight molecules of first row elements: HF, NH3, H2O, CO2, H2CO, CH4, C2H2, and C2H4. We find that the use of the second-order ADC technique [ADC(2)] that includes double electronic excitations leads to a substantial systematic improvement over the first-order method [ADC(1)] and to a good agreement with experiment for photon energies below 80 eV. The use of extended second-order ADC theory [ADC(2)x] leads to a smaller further improvement. Above 80 eV photon energy all three methods lead to significant deviations from the experimental values which we attribute to the use of Gaussian single-electron bases. Our calculations show that the ADC(2)-Lanczos-Stieltjes technique is a reliable and efficient ab initio tool for theoretical prediction of total molecular photo-ionization cross-sections in the valence region.

  3. Time-reversal Studies in Photorecombination and Photoionization Experiments with Ion Beams

    NASA Astrophysics Data System (ADS)

    Müller, A.; Schippers, S.; Aguilar, A.; Alvarez, I.; Bannister, M. E.; Bozek, J.; Cisneros, C.; Covington, A. M.; Dunn, G. H.; Gharaibeh, M. F.; Hinojosa, G.; Ricz, S.; Schlachter, A. S.; Phaneuf, R. A.

    2003-08-01

    The principle of detailed balance relates the cross sections σPR for photorecombination (PR) and σPI for photoionization (PI) of ions on a state-to-state level. Measuring one or the other of the two cross sections provides direct information about the time-reversed process. Measurements carried out at the Advanced Light Source, Berkeley, for PI of C2+ and Sc2+ are compared with experimental results from the heavy-ion storage ring TSR, Heidelberg, on PR of C3+ and Sc3+, respectively. From that comparison, state selective cross sections can be inferred both for PR and PI. Both experimental approaches provide possibilities for high-resolution spectroscopy of multiply excited states.

  4. 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.

  5. 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.

  6. A new spin foam model for 4D gravity

    NASA Astrophysics Data System (ADS)

    Freidel, Laurent; Krasnov, Kirill

    2008-06-01

    Starting from Plebanski formulation of gravity as a constrained BF theory we propose a new spin foam model for 4D Riemannian quantum gravity that generalizes the well-known Barrett Crane model and resolves the inherent to it ultra-locality problem. The BF formulation of 4D gravity possesses two sectors: gravitational and topological ones. The model presented here is shown to give a quantization of the gravitational sector, and is dual to the recently proposed spin foam model of Engle et al which, we show, corresponds to the topological sector. Our methods allow us to introduce the Immirzi parameter into the framework of spin foam quantization. We generalize some of our considerations to the Lorentzian setting and obtain a new spin foam model in that context as well.

  7. 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.

  8. Quantication and analysis of respiratory motion from 4D MRI

    NASA Astrophysics Data System (ADS)

    Aizzuddin Abd Rahni, Ashrani; Lewis, Emma; Wells, Kevin

    2014-11-01

    It is well known that respiratory motion affects image acquisition and also external beam radiotherapy (EBRT) treatment planning and delivery. However often the existing approaches for respiratory motion management are based on a generic view of respiratory motion such as the general movement of organ, tissue or fiducials. This paper thus aims to present a more in depth analysis of respiratory motion based on 4D MRI for further integration into motion correction in image acquisition or image based EBRT. Internal and external motion was first analysed separately, on a per-organ basis for internal motion. Principal component analysis (PCA) was then performed on the internal and external motion vectors separately and the relationship between the two PCA spaces was analysed. The motion extracted from 4D MRI on general was found to be consistent with what has been reported in literature.

  9. Photoionization of ground and excited levels of P II

    NASA Astrophysics Data System (ADS)

    Nahar, Sultana N.

    2017-01-01

    Photoionization cross section (σPI) of P II, (hν + P II → P III + e), from ground and a large number of excited levels are presented. The study includes the resonant structures and the characteristics of the background in photoionization cross sections. The present calculations were carried out in the Breit-Pauli R-matrix (BPRM) method that includes relativistic effects. The autoionizing resonances are delineated with a fine energy mesh to observe the fine structure effects. A singular resonance, formed by the coupling of channels in fine structure but not allowed in LS coupling, is seen at the ionization threshold of photoionization for the ground and many excited levels. The background cross section is seen enhanced compared to smooth decay for the excited levels. Examples are presented to illustrate the enhanced background cross sections at the energies of the core levels, 4P3/2 and 2D3/2, that are allowed for electric dipole transitions by the core ground level 2 P1/2o. In addition strong Seaton or photo-excitation-of-core (PEC) resonances are found in the photoionization of single valence electron excited levels. Calculations used a close coupling wave function expansion that included 18 fine structure levels of core P III from configurations 3s23p, 3s3p2, 3s23d, 3s24s, 3s24p and 3p3. Photoionization cross sections are presented for all 475 fine structure levels of P II found with n ≤ 10 and l ≤ 9. The present results will provide high precision parameters of various applications involving this less studied ion.

  10. Photodissociation and photoionization of organosulfur radicals

    SciTech Connect

    Hsu, Chia-Wei

    1994-05-27

    The dynamics of S(3P2,1,0, 1D2) production from the 193 nm photodissociation of CH3SCH3, H2S and CH3SH have been studied using 2 + 1 resonance-enhanced multiphoton ionization (REMPI) techniques. The 193 nm photodissociation cross sections for the formation of S from CH3S and HS initially prepared in the photodissociation of CH3SCH3 and H2S are estimated to be 1 x 10-18 and 1.1 x 10-18 cm2, respectively. The dominant product from CH3S is S(1D), while that from SH is S(3P). Possible potential energy surfaces involved in the 193 nm photodissociation of CH3S($\\tilde{X}$) and SH(X) have been also examined. Threshold photoelectron (PE) spectra for SH and CH3S formed in the ultraviolet photodissociation of H2S and CH3SH, 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 ΔN < 0 with the ΔN value up to -3, an observation similar to that found in the PFI-PE spectra of OH (OD) and NO. The ionization energies for SH(X2Π3,2) and CH3S($\\tilde{X}$2E3/2) are determined to be 84,057.5 ± 3 cm-1 and 74,726 ± 8 cm-1 respectively. The spin-orbit splittings for SH(X2Π3/2, 1/2) and CH3S($\\tilde{X}$2E3/2, 1/2) are found to be 377 ± 2 and 257 ± 5 cm-1, respectively, in agreement with previous measurements. The C-S stretching frequency for CH3S+($\\tilde{X}$3A2) is 733 ± 5 cm-1. This study illustrates that the PFI-PE detection method can be a

  11. Real-time 4D ultrasound mosaicing and visualization.

    PubMed

    Brattain, Laura J; Howe, Robert D

    2011-01-01

    Intra-cardiac 3D ultrasound imaging has enabled new minimally invasive procedures. Its narrow field of view, however, limits its efficacy in guiding beating heart procedures where geometrically complex and spatially extended moving anatomic structures are often involved. In this paper, we present a system that performs electrocardiograph gated 4D mosaicing and visualization of 3DUS volumes. Real-time operation is enabled by GPU implementation. The method is validated on phantom and porcine heart data.

  12. Digital-micromirror-device-based confocal 4D microscopy

    NASA Astrophysics Data System (ADS)

    Schellenberg, M.; Kloster, M.; Napier, J.; Peev, E.; Neu, W.

    2012-03-01

    Digital Micromirror Device based microscopy combines fast confocal 4D-microscopy along with conventional methods for light microscopy and new technological approaches to a versatile tool for the observation of in vivo processes in living biological cells and measurement of technical surfaces. Due to the use of variable size pinholes and adjustable scan patterns conditions for confocal measurement can easily be optimized to the prerequisites of the sample "on the fly".

  13. 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.

  14. 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

    2015-08-10

    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.

  15. Repairing Stevenson's step in the 4d Ising model

    NASA Astrophysics Data System (ADS)

    Balog, Janos; Niedermayer, Ferenc; Weisz, Peter

    2006-05-01

    In a recent paper Stevenson claimed that analysis of the data on the wave function renormalization constant near the critical point of the 4d Ising model is not consistent with analytical expectations. Here we present data with improved statistics and show that the results are indeed consistent with conventional wisdom once one takes into account the uncertainty of lattice artifacts in the analytical computations.

  16. Interference in the molecular photoionization and Young's double-slit experiment

    NASA Astrophysics Data System (ADS)

    Baltenkov, A. S.; Becker, U.; Manson, S. T.; Msezane, A. Z.

    2012-02-01

    The photoabsorption by an electron bound by a two-centre potential has been investigated within the framework of the zero-range potential model. Expressions for total photoabsorption cross sections and for the photoelectron angular distributions have been derived for fixed-in-space and randomly oriented targets. The analytical formulae for gerade and ungerade molecular states have been used to analyse separately the molecular effects due to the two-centre ground state of quasi-molecule and diffraction effects that are connected with the spherical waves in the molecular continuum. It is shown that the interference of these waves significantly influences the magnitude of the cross sections near threshold but does not significantly distort the shape of the photoelectron angular distribution and it depends rather weakly on the character of the forces acting between the electron and molecular residue: Coulomb forces for neutral molecular photoionization or the short-range forces in the case of photodetachment of molecular negative ions. It is shown that despite the fact that the photoionization of diatomic molecules is reminiscent of Young's double-slit experiment, the similarity between these processes has been grossly exaggerated. This is confirmed by comparing the results of the classical interference of an electron scattered by two spatially separated centres with molecular photoelectron angular distributions.

  17. 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.

  18. 2D:4D Ratio and its Implications in Medicine

    PubMed Central

    Jeevanandam, Saravanakumar

    2016-01-01

    Digit ratios, especially 2D:4D ratio, a potential proxy marker for prenatal androgen exposure shows sexual dimorphism. Existing literature and recent research show accumulating evidence on 2D:4D ratio showing correlations with various phenotypic traits in humans. Ratio of 2D:4D is found to correlate negatively to testosterone and positively to oestrogen in the foetus. Interestingly, it is constant since birth and not influenced by the adult hormone levels. Usually, males have lower ratios when compared to females. Prenatal androgen exposure and therefore, digit ratios have been reported to be associated with numerical competencies, spatial skills, handedness, cognitive abilities, academic performance, sperm counts, personalities and prevalence of obesity, migraine, eating disorders, depression, myopia, autism etc. The authors have attempted to write a brief account on the digit ratios and the dimorphism observed in various physiological, psychological and behavioural traits. Also, the authors have discussed the relevant molecular basics and the methods of measurement of digit ratios. PMID:28208851

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Photoionization of Sc 2+: Experimental link with photorecombination of Sc 3+ by application of detailed balance

    NASA Astrophysics Data System (ADS)

    Schippers, S.; Müller, A.; Ricz, S.; Bannister, M. E.; Dunn, G. H.; Bozek, J.; Schlachter, A. S.; Hinojosa, G.; Cisneros, C.; Aguilar, A.; Covington, A. M.; Gharaibeh, M. F.; Phaneuf, R. A.

    2003-05-01

    The principle of microscopic time-reversal of physical processes, detailed balance, is widely used and depended upon in the theoretical community as a connection between the inverse processes of photorecombination (PR) and photoionization (PI). This paper reports on a novel use of detailed balance and the comparison of experimental results obtained by two very distinct techniques to determine both the metastable fraction of an ion beam and partial Sc3+ PR cross sections and partial Sc2+ PI cross sections for the ground state and for two metastable states. The Sc2+ to Sc3+ system presents a unique opportunity to obtain comprehensive state-selective information by combining results from PR and PI experiments.

  4. 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.

  5. Fast GPU based adaptive filtering of 4D echocardiography.

    PubMed

    Broxvall, Mathias; Emilsson, Kent; Thunberg, Per

    2012-06-01

    Time resolved three-dimensional (3D) echocardiography generates four-dimensional (3D+time) data sets that bring new possibilities in clinical practice. Image quality of four-dimensional (4D) echocardiography is however regarded as poorer compared to conventional echocardiography where time-resolved 2D imaging is used. Advanced image processing filtering methods can be used to achieve image improvements but to the cost of heavy data processing. The recent development of graphics processing unit (GPUs) enables highly parallel general purpose computations, that considerably reduces the computational time of advanced image filtering methods. In this study multidimensional adaptive filtering of 4D echocardiography was performed using GPUs. Filtering was done using multiple kernels implemented in OpenCL (open computing language) working on multiple subsets of the data. Our results show a substantial speed increase of up to 74 times, resulting in a total filtering time less than 30 s on a common desktop. This implies that advanced adaptive image processing can be accomplished in conjunction with a clinical examination. Since the presented GPU processor method scales linearly with the number of processing elements, we expect it to continue scaling with the expected future increases in number of processing elements. This should be contrasted with the increases in data set sizes in the near future following the further improvements in ultrasound probes and measuring devices. It is concluded that GPUs facilitate the use of demanding adaptive image filtering techniques that in turn enhance 4D echocardiographic data sets. The presented general methodology of implementing parallelism using GPUs is also applicable for other medical modalities that generate multidimensional data.

  6. 4D seismic data acquisition method during coal mining

    NASA Astrophysics Data System (ADS)

    Du, Wen-Feng; Peng, Su-Ping

    2014-06-01

    In order to observe overburden media changes caused by mining processing, we take the fully-mechanized working face of the BLT coal mine in Shendong mine district as an example to develop a 4D seismic data acquisition methodology during coal mining. The 4D seismic data acquisition is implemented to collect 3D seismic data four times in different periods, such as before mining, during the mining process and after mining to observe the changes of the overburden layer during coal mining. The seismic data in the research area demonstrates that seismic waves are stronger in energy, higher in frequency and have better continuous reflectors before coal mining. However, all this is reversed after coal mining because the overburden layer has been mined, the seismic energy and frequency decrease, and reflections have more discontinuities. Comparing the records collected in the survey with those from newly mined areas and other records acquired in the same survey with the same geometry and with a long time for settling after mining, it clearly shows that the seismic reflections have stronger amplitudes and are more continuous because the media have recovered by overburden layer compaction after a long time of settling after mining. By 4D seismic acquisition, the original background investigation of the coal layers can be derived from the first records, then the layer structure changes can be monitored through the records of mining action and compaction action after mining. This method has laid the foundation for further research into the variation principles of the overburden layer under modern coal-mining conditions.

  7. Digit ratio (2D:4D), salivary testosterone, and handedness.

    PubMed

    Beaton, Alan A; Rudling, Nick; Kissling, Christian; Taurines, Regine; Thome, Johannes

    2011-03-01

    The length of the index finger relative to that of the ring finger, the 2D:4D ratio, has been taken to be a marker of the amount of testosterone (T) that was present in the foetal environment (Manning, Scutt, Wilson, & Lewis-Jones, 1998). It has also been suggested (Geschwind & Galaburda, 1987) that elevated levels of foetal T are associated with left-handedness and that adult levels of circulating T might relate to foetal levels (Jamison, Meier, & Campbell, 1993). We used multiple regression analyses to investigate whether there is any relationship between either left or right hand 2D:4D ratio and handedness. We also examined whether adult levels of salivary T (or cortisol, used as a control hormone) predict digit ratio and/or handedness. Although the 2D:4D ratio of neither the left nor the right hand was related to handedness, the difference between the digit ratios of the right and left hands, D(R-L), was a significant predictor of handedness and of the performance difference between the hands on a peg-moving task, supporting previous findings (Manning & Peters, 2009; Manning et al., 1998; Manning, Trivers, Thornhill, & Singh, 2000; Stoyanov, Marinov, & Pashalieva, 2009). Adult circulating T levels did not predict the digit ratio of the left or right hand; nor was there a significant relationship between concentrations of salivary T (or cortisol) and either hand preference or asymmetry in manual skill. We suggest that the association between D(R-L) and hand preference arises because D(R-L) is a correlate of sensitivity to T in the developing foetus.

  8. Parametrizations and dynamical analysis of angle-integrated cross sections for double photoionization including nondipole effects

    SciTech Connect

    Istomin, Andrei Y.; Starace, Anthony F.; Manakov, N. L.; Meremianin, A. V.; Kheifets, A. S.; Bray, Igor

    2005-11-15

    Similarly to differential cross sections for one-electron photoionization, the doubly differential cross section for double photoionization (DPI) may be conveniently described by four parameters: the singly differential (with respect to energy sharing) cross section ({sigma}{sub 0}), the dipole asymmetry parameter ({beta}), and two nondipole asymmetry parameters ({gamma} and {delta}). Here we derive two model-independent representations for these parameters for DPI from a {sup 1}S{sub 0} atomic bound state: (i) in terms of one-dimensional integrals of the polarization-invariant DPI amplitudes and (ii) in terms of the exact two-electron reduced matrix elements. For DPI of He at excess energies, E{sub exc}, of 100 eV, 450 eV, and 1 keV, we present numerical results for the asymmetry parameters within the framework of the convergent close-coupling theory and compare them with results of lowest-order (in the interelectron interaction) perturbation theory (LOPT). The results for E{sub exc}=1 keV exhibit a nondipole asymmetry that is large enough to be easily measured experimentally. We find excellent agreement between our LOPT results and other theoretical predictions and experimental data for total cross sections and ratios of double to single ionization cross sections for K-shell DPI from several multielectron atoms.

  9. Design of laboratory experiments to study photoionization fronts driven by thermal sources

    SciTech Connect

    Drake, R. P.; Hazak, G.; Keiter, P. A.; Davis, J. S.; Patterson, C. R.; Frank, A.; Blackman, E. G.; Busquet, Michel

    2016-12-20

    This study analyzes the requirements of a photoionization-front experiment that could be driven in the laboratory, using thermal sources to produce the necessary flux of ionizing photons. It reports several associated conclusions. Such experiments will need to employ the largest available facilities, capable of delivering many kJ to MJ of energy to an x-ray source. They will use this source to irradiate a volume of neutral gas, likely of N, on a scale of a few mm to a few cm, increasing with source energy. For a gas pressure of several to ten atmospheres at room temperature, and a source temperature near 100 eV, one will be able to drive a photoionization front through a system of tens to hundreds of photon mean free paths. The front should make the familiar transition from the so-called R-Type to D-Type as the radiation flux diminishes with distance. The N is likely to reach the He-like state. Preheating from the energetic photons appears unlikely to become large enough to alter the essential dynamics of the front beyond some layer near the surface. For well-chosen experimental conditions, competing energy transport mechanisms are small.

  10. Low-energy fine-structure resonances in photoionization of O ii

    NASA Astrophysics Data System (ADS)

    Nahar, Sultana N.; Montenegro, Maximiliano; Eissner, Werner; Pradhan, Anil K.

    2010-12-01

    Resonant features in low-energy photoionization cross sections are reported in coupled-channel calculations for O ii including relativistic fine structure. The calculations reveal extensive near-threshold resonant structures in the small energy region between the fine structure levels of the ground state 2p2(3P0,1,2) of the residual ion O iii. Although the resonances have not yet been observed, they are similar to other experimentally observed features. They are expected to significantly enhance the very-low-temperature dielectronic recombination rates, potentially leading to the resolution of an outstanding nebular abundances anomaly. Higher energy partial and total photoionization cross sections of the ground configuration levels 2p3(4S3/2o,2D3/2,5/2o,2P1/2,3/2o) are found to be in agreement with experimental measurements on synchrotron-based photon sources [1-3], thereby identifying the excited O iii levels present in the ion beams. These are also the first results from a recently developed version of Breit-Pauli R-matrix (BPRM) codes, with inclusion of two-body magnetic interaction terms. The improved relativistic treatment could be important for other astrophysical applications and for more precise benchmarking of experimental measurements.

  11. 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.

  12. 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.

  13. Design of laboratory experiments to study photoionization fronts driven by thermal sources

    DOE PAGES

    Drake, R. P.; Hazak, G.; Keiter, P. A.; ...

    2016-12-20

    This study analyzes the requirements of a photoionization-front experiment that could be driven in the laboratory, using thermal sources to produce the necessary flux of ionizing photons. It reports several associated conclusions. Such experiments will need to employ the largest available facilities, capable of delivering many kJ to MJ of energy to an x-ray source. They will use this source to irradiate a volume of neutral gas, likely of N, on a scale of a few mm to a few cm, increasing with source energy. For a gas pressure of several to ten atmospheres at room temperature, and a sourcemore » temperature near 100 eV, one will be able to drive a photoionization front through a system of tens to hundreds of photon mean free paths. The front should make the familiar transition from the so-called R-Type to D-Type as the radiation flux diminishes with distance. The N is likely to reach the He-like state. Preheating from the energetic photons appears unlikely to become large enough to alter the essential dynamics of the front beyond some layer near the surface. For well-chosen experimental conditions, competing energy transport mechanisms are small.« less

  14. Design of Laboratory Experiments to Study Photoionization Fronts Driven by Thermal Sources

    NASA Astrophysics Data System (ADS)

    Drake, R. P.; Hazak, G.; Keiter, P. A.; Davis, J. S.; Patterson, C. R.; Frank, A.; Blackman, E. G.; Busquet, Michel

    2016-12-01

    This paper analyzes the requirements of a photoionization-front experiment that could be driven in the laboratory, using thermal sources to produce the necessary flux of ionizing photons. It reports several associated conclusions. Such experiments will need to employ the largest available facilities, capable of delivering many kJ to MJ of energy to an X-ray source. They will use this source to irradiate a volume of neutral gas, likely of N, on a scale of a few mm to a few cm, increasing with source energy. For a gas pressure of several to ten atmospheres at room temperature, and a source temperature near 100 eV, one will be able to drive a photoionization front through a system of tens to hundreds of photon mean free paths. The front should make the familiar transition from the so-called R-Type to D-Type as the radiation flux diminishes with distance. The N is likely to reach the He-like state. Preheating from the energetic photons appears unlikely to become large enough to alter the essential dynamics of the front beyond some layer near the surface. For well-chosen experimental conditions, competing energy transport mechanisms are small.

  15. Overlapping photo-ionized doubly excited resonance series for Li+ ion

    NASA Astrophysics Data System (ADS)

    Fang, T. K.; Gao, X.; Chang, T. N.

    2017-06-01

    Based on two different approaches, the B-spline-based K-matrix method and the eigenchannel R-matrix method, we present a detailed theoretical study on the photoionization from the ground and bound excited 1s2s{}1S and 1s2p{}1P states of an Li+ ion to continua between the N = 2 and N = 3 thresholds, dominated by overlapping doubly excited resonance series embedded in multiple singly ionized channels. The nearly identical theoretical spectra from these two different calculations, together with the excellent agreement between the length and velocity results, suggests that our study has successfully led to a reliable estimate of the Li+ photoionization spectra. In addition to identifying all overlapping doubly excited autoionization series, our calculated spectrum is in good agreement with the only observed data for two broad resonances. Our study has also shown that the strong interaction between neighboring resonances from different resonance series, which is responsible for the level crossing for in the He atom, is substantially smaller due to a stronger nuclear attraction to atomic electrons for the two-electron ions.

  16. 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.

  17. Low-energy fine-structure resonances in photoionization of O ii

    SciTech Connect

    Nahar, Sultana N.; Pradhan, Anil K.; Montenegro, Maximiliano; Eissner, Werner

    2010-12-15

    Resonant features in low-energy photoionization cross sections are reported in coupled-channel calculations for O ii including relativistic fine structure. The calculations reveal extensive near-threshold resonant structures in the small energy region between the fine structure levels of the ground state 2p{sup 2}({sup 3}P{sub 0,1,2}) of the residual ion O iii. Although the resonances have not yet been observed, they are similar to other experimentally observed features. They are expected to significantly enhance the very-low-temperature dielectronic recombination rates, potentially leading to the resolution of an outstanding nebular abundances anomaly. Higher energy partial and total photoionization cross sections of the ground configuration levels 2p{sup 3}({sup 4}S{sub 3/2}{sup o},{sup 2}D{sub 3/2,5/2}{sup o},{sup 2}P{sub 1/2,3/2}{sup o}) are found to be in agreement with experimental measurements on synchrotron-based photon sources [1-3], thereby identifying the excited O iii levels present in the ion beams. These are also the first results from a recently developed version of Breit-Pauli R-matrix (BPRM) codes, with inclusion of two-body magnetic interaction terms. The improved relativistic treatment could be important for other astrophysical applications and for more precise benchmarking of experimental measurements.

  18. 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.

  19. 4D micro-CT using fast prospective gating.

    PubMed

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

    2012-01-07

    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

  20. 4D Flow MRI in Neuroradiology: Techniques and Applications.

    PubMed

    Pereira, Vitor Mendes; Delattre, Benedicte; Brina, Olivier; Bouillot, Pierre; Vargas, Maria Isabel

    2016-04-01

    Assessment of the intracranial flow is important for the understanding and management of cerebral vascular diseases. From brain aneurysms and arteriovenous malformations lesions to intracranial and cervical stenosis, the appraisal of the blood flow can be crucial and influence positively on patients' management. The determination of the intracranial hemodynamics and the collateral pattern seems to play to a major role in the management of these lesions. 4D flow magnetic resonance imaging is a noninvasive phase contrast derived method that has been developed and applied in neurovascular diseases. It has a great potential if followed by further technical improvements and comprehensive and systematic clinical studies.

  1. Realistic CT simulation using the 4D XCAT phantom

    PubMed Central

    Segars, W. P.; Mahesh, M.; Beck, T. J.; Frey, E. C.; Tsui, B. M. W.

    2008-01-01

    The authors develop a unique CT simulation tool based on the 4D extended cardiac-torso (XCAT) phantom, a whole-body computer model of the human anatomy and physiology based on NURBS surfaces. Unlike current phantoms in CT based on simple mathematical primitives, the 4D XCAT provides an accurate representation of the complex human anatomy and has the advantage, due to its design, that its organ shapes can be changed to realistically model anatomical variations and patient motion. A disadvantage to the NURBS basis of the XCAT, however, is that the mathematical complexity of the surfaces makes the calculation of line integrals through the phantom difficult. They have to be calculated using iterative procedures; therefore, the calculation of CT projections is much slower than for simpler mathematical phantoms. To overcome this limitation, the authors used efficient ray tracing techniques from computer graphics, to develop a fast analytic projection algorithm to accurately calculate CT projections directly from the surface definition of the XCAT phantom given parameters defining the CT scanner and geometry. Using this tool, realistic high-resolution 3D and 4D projection images can be simulated and reconstructed from the XCAT within a reasonable amount of time. In comparison with other simulators with geometrically defined organs, the XCAT-based algorithm was found to be only three times slower in generating a projection data set of the same anatomical structures using a single 3.2 GHz processor. To overcome this decrease in speed would, therefore, only require running the projection algorithm in parallel over three processors. With the ever decreasing cost of computers and the rise of faster processors and multi-processor systems and clusters, this slowdown is basically inconsequential, especially given the vast improvement the XCAT offers in terms of realism and the ability to generate 3D and 4D data from anatomically diverse patients. As such, the authors conclude

  2. 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.

  3. 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

  4. 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

  5. Multielectron spectroscopy: the xenon 4d hole double auger decay.

    PubMed

    Penent, F; Palaudoux, J; Lablanquie, P; Andric, L; Feifel, R; Eland, J H D

    2005-08-19

    A magnetic bottle spectrometer of the type recently developed by Eland et al. [Phys. Rev. Lett. 90, 053003 (2003).] has been implemented for use with synchrotron radiation, allowing multidimensional electron spectroscopy. Its application to the Xe 4d double Auger decay reveals all the energy pathways involved. The dominant path is a cascade process with a rapid (6 fs) ejection of a first Auger electron followed by the slower (>23 fs) emission of a second Auger electron. Weaker processes implying 3 electron processes are also revealed, namely, direct double Auger and associated Rydberg series.

  6. 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.

  7. Realistic CT simulation using the 4D XCAT phantom.

    PubMed

    Segars, W P; Mahesh, M; Beck, T J; Frey, E C; Tsui, B M W

    2008-08-01

    The authors develop a unique CT simulation tool based on the 4D extended cardiac-torso (XCAT) phantom, a whole-body computer model of the human anatomy and physiology based on NURBS surfaces. Unlike current phantoms in CT based on simple mathematical primitives, the 4D XCAT provides an accurate representation of the complex human anatomy and has the advantage, due to its design, that its organ shapes can be changed to realistically model anatomical variations and patient motion. A disadvantage to the NURBS basis of the XCAT, however, is that the mathematical complexity of the surfaces makes the calculation of line integrals through the phantom difficult. They have to be calculated using iterative procedures; therefore, the calculation of CT projections is much slower than for simpler mathematical phantoms. To overcome this limitation, the authors used efficient ray tracing techniques from computer graphics, to develop a fast analytic projection algorithm to accurately calculate CT projections directly from the surface definition of the XCAT phantom given parameters defining the CT scanner and geometry. Using this tool, realistic high-resolution 3D and 4D projection images can be simulated and reconstructed from the XCAT within a reasonable amount of time. In comparison with other simulators with geometrically defined organs, the XCAT-based algorithm was found to be only three times slower in generating a projection data set of the same anatomical structures using a single 3.2 GHz processor. To overcome this decrease in speed would, therefore, only require running the projection algorithm in parallel over three processors. With the ever decreasing cost of computers and the rise of faster processors and multi-processor systems and clusters, this slowdown is basically inconsequential, especially given the vast improvement the XCAT offers in terms of realism and the ability to generate 3D and 4D data from anatomically diverse patients. As such, the authors conclude

  8. 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.

  9. Loop-corrected Virasoro symmetry of 4D quantum gravity

    NASA Astrophysics Data System (ADS)

    He, T.; Kapec, D.; Raclariu, A.; Strominger, A.

    2017-08-01

    Recently a boundary energy-momentum tensor T zz has been constructed from the soft graviton operator for any 4D quantum theory of gravity in asymptotically flat space. Up to an "anomaly" which is one-loop exact, T zz generates a Virasoro action on the 2D celestial sphere at null infinity. Here we show by explicit construction that the effects of the IR divergent part of the anomaly can be eliminated by a one-loop renormalization that shifts T zz .

  10. Multiconfigurational Hartree-Fock close-coupling ansatz: Application to the argon photoionization cross section and delays

    NASA Astrophysics Data System (ADS)

    Carette, T.; Dahlström, J. M.; Argenti, L.; Lindroth, E.

    2013-02-01

    We present a robust, ab initio method for addressing atom-light interactions and apply it to photoionization of argon. We use a close-coupling ansatz constructed on a multiconfigurational Hartree-Fock description of localized states and B-spline expansions of the electron radial wave functions. In this implementation, the general many-electron problem can be tackled thanks to the use of the atsp2k libraries [C. Froese Fischer , Comput. Phys. Commun.CPHCBZ0010-465510.1016/j.cpc.2007.01.006 176, 559 (2007)]. In the present contribution, we combine this method with exterior complex scaling, thereby allowing for the computation of the complex partial amplitudes that encode the whole dynamics of the photoionization process. The method is validated on the 3s3p6np series of resonances converging to the 3s extraction. Then, it is used for computing the energy dependent differential atomic delay between 3p and 3s photoemission, and agreement is found with the measurements of Guénot [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.85.053424 85, 053424 (2012)]. The effect of the presence of resonances in the one-photon spectrum on photoionization delay measurements is studied.

  11. Time-Dependent Photoionization of Gas Outflows in AGN

    NASA Astrophysics Data System (ADS)

    Elhoussieny, Ehab E.; Bautista, M.; Garcia, J.; Kallman, T. R.

    2013-01-01

    Gas outflows are fundamental components of Active Galactic Nuclei (AGN) activity. Time-variability of ionizing radiation, which is characteristic of AGN in various different time scales, may produce non-equilibrium photoionization conditions over a significant fraction of the flow and yields supersonically moving cooling/heating fronts. These fast fronts create pressure imbalances that can only be resolved by fragmentation of the flow and acceleration of such fragments. This mechanism can explain the kinematic structure of low ionization BAL systems (FeLoBAL). This mechanism may also have significant effects on other types of outflows given the wide range of variability time scales in AGN. We will study these effects in detail by constructing time-dependent photoionization models of the outflows and incorporating these models into radiative-hydrodynamic simulations.

  12. Photoionization of Endohedral Atoms: Collective, Reflective and Collateral Emissions

    NASA Astrophysics Data System (ADS)

    Chakraborty, Himadri S.; McCune, Matthew A.; Madjet, Mohamed E.; Hopper, Dale E.; Manson, Steven T.

    2009-12-01

    The photoionization properties of a fullerene-confined atom differ dramatically from that of an isolated atom. In the low energy region, where the fullerene plasmons are active, the electrons of the confined atom emerge through a collective channel carrying a significant chunk of plasmon with it. The photoelectron angular distribution of the confined atom however shows far lesser impact of the effect. At higher energies, the interference between two single-electron ionization channels, one directly from the atom and another reflected off the fullerene cage, producuces oscillatory cross sections. But for the outermost atomic level, which transfers some electrons to the cage, oscillations are further modulated by the collateral emission from the part of the atomic charge density transferred to the cage. These various modes of emissions are studied for the photoionization of Ar endohedrally confined in C60.

  13. Vibrationally resolved shape resonant photoionization of SiF4

    NASA Astrophysics Data System (ADS)

    Kakar, Sandeep; Poliakoff, E. D.; Rosenberg, R. A.

    1992-01-01

    We have measured vibrationally resolved fluorescence from SiF+4(D˜ 2A1) photoions to determine the vibrational branching ratio σ[v=(1,0,0,0)]/σ[v=(0,0,0,0)] in the excitation energy range 22photoionization are discussed.

  14. Fluorescence probes of spectroscopic and dynamical aspects of molecular photoionization

    NASA Astrophysics Data System (ADS)

    Poliakoff, Erwin D.

    1988-11-01

    Studies were made of vibrationally resolved aspects of shape resonant excitation in the photoionization of N(2)0. This experiment was performed by generating dispersed fluorescence spectra from electronically excited photoions. These results are the first vibrationally resolved results on a polyatomic shape resonance. In vibrationally resolved measurements, different internuclear configurations are probed by sampling alternative vibrational levels of the ion. As a result, the continuum electron behavior can be mapped out most clearly, and the qualitative aspects of the electron ejection can be understood clearly. A central motivation for studying polyatomic shape resonances is that alternative vibrational modes may be explored, revealing facets that are nonexistent for diatomic systems, which are the only systems that have been characterized previously.

  15. 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.

  16. 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.

  17. Photoionization of Endohedral Atoms: Collective, Reflective and Collateral Emissions

    SciTech Connect

    Chakraborty, Himadri S.; McCune, Matthew A.; Hopper, Dale E.; Madjet, Mohamed E.; Manson, Steven T.

    2009-12-03

    The photoionization properties of a fullerene-confined atom differ dramatically from that of an isolated atom. In the low energy region, where the fullerene plasmons are active, the electrons of the confined atom emerge through a collective channel carrying a significant chunk of plasmon with it. The photoelectron angular distribution of the confined atom however shows far lesser impact of the effect. At higher energies, the interference between two single-electron ionization channels, one directly from the atom and another reflected off the fullerene cage, producuces oscillatory cross sections. But for the outermost atomic level, which transfers some electrons to the cage, oscillations are further modulated by the collateral emission from the part of the atomic charge density transferred to the cage. These various modes of emissions are studied for the photoionization of Ar endohedrally confined in C{sub 60}.

  18. 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.

  19. 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.

  20. Segmentation of 4D echocardiography using stochastic online dictionary learning.

    PubMed

    Huang, Xiaojie; Dione, Donald P; Lin, Ben A; Bregasi, Alda; Sinusas, Albert J; Duncan, James S

    2013-01-01

    Dictionary learning has been shown to be effective in exploiting spatiotemporal coherence for echocardiographic segmentation. To overcome the limitations of previous methods, we present a stochastic online dictionary learning approach for segmenting left ventricular borders from 4D echocardiography. It is based on stochastic approximations and processes a mini-batch of samples at a time, which results in lower memory consumption and lower computational cost than classical batch algorithms. In contrast to the previous methods, where dictionaries and their weights are optimized only on the most recently segmented frame, our stochastic online learning procedure optimizes the dictionaries and the corresponding weights by aggregating all the past information while adapting them to the dynamically changing data. The rate of updating the past information is controlled and varied according to the appearance scale to seek a balance between old and new information. Results on 26 4D echocardiographic images show the proposed method is more accurate, more robust, and faster than the previous batch algorithm.