WorldWideScience

Sample records for autoionization

  1. 5. International workshop on autoionization phenomena in atoms. Abstracts

    International Nuclear Information System (INIS)

    Summaries of the reports presented at the 5 International Workshop on Autoionization Phenomena in Atoms (Dubna, 12-14 December 1995). The main topics of these 53 reports are the following ones: photoexcitation of autoionizing states in atoms and ions, autoionization in electron-atom collisions, autoionization in heavy particle collisions, coincidence experiments in autoionization studies, investigations of autoionizing states with lasers and wave functions and decay characteristics of autoionizing states

  2. Autoionization in a strong magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Lemoigne, J.P.; Grandin, J.P.; Husson, X.; Kucal, H. (Institut des Sciences de la Matiere du Rayonnement, 14 - Caen (FR) Caen Univ., 14 (FR)); Zakrzewski, J.; Dohnalik, T. (Uniwersytet Jagiellonski, Krakow, (PL). Inst. Fizyki); Marcinek, R. (Wyzsza Szkola Pedagogiczna, Cracow (PL))

    1991-04-15

    The autoionization in the presence of a strong magnetic field is studied experimentally for 11s'(1/2) 1 argon level. It is shown that autoionizing resonance properties are strongly affected by the magnetic-field-induced modification of the continuum in which the resonance is embedded. A simple theoretical model explains essential features of the phenomenon.

  3. [Observation of autoionization levels in uranium I].

    Science.gov (United States)

    Jin, C; Wang, X

    1999-02-01

    A number of Rydberg and autoionization levels of U I have been studied using three-step resonant ionization methods with three pulsed tunable dye lasers. Energy levels of uranium atom have been measured, which were located in the 49898-50880 cm(-1) energy interval. PMID:15818900

  4. Auto-ionizing states in MgI

    International Nuclear Information System (INIS)

    Hartree-Fock calculations have been performed for the auto-ionizing levels of the 3pns, 3pnp, 4snp (n=4 to 7) and 3pnd (n=3 to 7) series in MgI. The calculated energies of the auto-ionizing states are compared with the available results from photo-absorption measurements and ejected-electron experiments. (author)

  5. Autoionization of helium following excitation by fast, multiply charged ions

    International Nuclear Information System (INIS)

    Using two parallel plate electrostatic spectrometers, the authors have measured the autoionization spectra of doubly-excited helium, following excitation by charged, 700 to 3500 KeV lithium ions produced by the Dynamitron. In particular, they studied the effect of projectile nuclear charge on the helium autoionization profiles and the continuum in which they are embedded

  6. Attosecond Time-Resolved Autoionization of Argon

    International Nuclear Information System (INIS)

    Autoionization of argon atoms was studied experimentally by transient absorption spectroscopy with isolated attosecond pulses. The peak position, intensity, linewidth, and shape of the 3s3p6np 1P Fano resonance series (26.6-29.2 eV) were modified by intense few-cycle near infrared laser pulses, while the delay between the attosecond pulse and the laser pulse was changed by a few femtoseconds. Numerical simulations revealed that the experimentally observed splitting of the 3s3p64p 1P line is caused by the coupling between two short-lived highly excited states in the strong laser field.

  7. Autoionizing States of Atoms Calculated Using Generalized Sturmians

    DEFF Research Database (Denmark)

    Avery, James Emil; Avery, John Scales

    2005-01-01

    The generalized Sturmian method is applied to autoionizing states of atoms and ions. If the Goscinskian basis sets allow for a sufficient amount of angular correletion, the calculated energies of doubly-excited (autoionizing) states are found to agree well with the few available experimental...... energies. A large-Z approximation is discussed, and simple formulas are derived which are valid not only for autoionizing states, but for all states of an isoelectronic atomic series. Diagonalization of a small block of the interelectron repulsion matrix yields roots that can be used for a wide range of Z...

  8. Polarization of fluorescence: a probe of molecular autoionization

    Energy Technology Data Exchange (ETDEWEB)

    Leroi, G. E. [Michigan State Univ., East Lansing, MI (United States); Dehmer, Joseph L. [Argonne National Laboratory (ANL), Argonne, IL (United States); Parr, Albert C. [National Bureau of Standards, Washington, DC (United States); Poliakoff, E. D. [Boston Univ., MA (United States)

    1983-01-01

    The polarization of fluorescence from excited-state molecular photoions provides a direct probe of the photoionization dynamics and the symmetry signatures of autoionizing resonances. Measurements on CO₂ and CS₂ are presented as examples.

  9. Relativistic Multichannel Theory: Theoretical Study of C+ Autoionization States

    Institute of Scientific and Technical Information of China (English)

    XIA Dan; ZHANG Shi-Zhong; PENG Yong-Lun; LI Jia-Ming

    2003-01-01

    Based on relativistic multichannel theory, the autoionization states of C+ are studied. We calculate all the autoionization states in the energy region of 193900 ~ 231700cm"1, and the results are in good agreement with the experimental data. The energy structure we obtain will be important in the dielectronic recombination processes, which plays a key role in determining the abundance of carbon in a nebula.

  10. Autoionization rate constants of zero electron kinetic energy Rydberg states

    International Nuclear Information System (INIS)

    Highlights: ► Rovibrational autoionization rate constants for diatomic molecules. ► Density matrix formulation based on the model of IBOA. ► Quantum number and energy dependences are studied. - Abstract: We have calculated the vibrational and rotational autoionization rate constants for diatomic molecules H2, N2, and HCl in high Rydberg states by employing the density matrix formulation with the inverse Born–Oppenheimer approximation basis set. The purpose is to simulate the main radiationless processes occurring in zero electron kinetic energy (ZEKE) spectroscopy. The quantum numbers and the energy dependences of the calculated autoionization rate constants are represented as the scaling laws via nonlinear regression. These data provide a suitable starting point for quantitative study of the intricate dynamics involved in ZEKE Rydberg states.

  11. Double-resonance spectroscopy of autoionizing states of ammonia

    Science.gov (United States)

    Raptis, C. A.; Bacon, J. A.; Pratt, S. T.

    2000-02-01

    New double-resonance ionization data are presented on the autoionizing Rydberg states of NH3 excited via selected rotational levels of the C˜' 1A1(0100) and (0200) states. Extrapolation of the Rydberg series provides a determination of the adiabatic ionization energy of NH3 that is in excellent agreement with that obtained by using zero kinetic energy photoelectron spectroscopy (ZEKE-PES). A comparison is presented between the field-free spectrum obtained by using a time-of-flight mass spectrometer and the 1-Tesla-spectrum obtained by using a magnetic-bottle electron spectrometer. Finally, the rotational and vibrational autoionization mechanisms are discussed.

  12. Multiphoton ionization of magnesium via an autoionizing state

    NARCIS (Netherlands)

    N.J. van Druten; R. Trainham; H.G. Muller

    1994-01-01

    Multiphoton single and double ionization of magnesium was studied by measuring electron energy spectra and ion mass spectra using 1-ps laser pulses in the 580-595-nm wavelength and 1012-1013-W/cm2 intensity range. In single ionization the (3p)2 1S doubly excited autoionizing state, resonant at the f

  13. (Studies of autoionizing states relevant to dielectronic recombination. Final report)

    International Nuclear Information System (INIS)

    Laser spectroscopy experiments on autoionizing states of alkaline earth atoms allow the inverse process, dielectronic recombination, to be studied in great detail under controlled and variable conditions. The research is also relevant to problems in physical chemistry involving excited molecules, and it has helped to clarify the physical processes of zero kinetic energy electron spectroscopy and coherent control

  14. Isotope shift measurement of autoionization Rydberg states of Sm

    International Nuclear Information System (INIS)

    The observation and measurement of isotope shift of autoionization Rydberg states 8G1/2 of Sm was reported. The isotope shift of the first excited state of Sm was also measured. Results were compared with that in Ref. 5

  15. Isotope shift measurement of autoionization Rydberg states of Sm

    International Nuclear Information System (INIS)

    The observation and measurement of isotope shift of autoionization Rydberg states 8G1/2 of Sm was reported. The isotope shift of the first excited state of Sm was also measured. Results were compared with that in Ref. 5. copyright 1997 American Institute of Physics

  16. Precision angle-resolved autoionization resonances in Ar and Ne

    Energy Technology Data Exchange (ETDEWEB)

    Berrah, N.; Langer, B.; Gorczyca, T.W. [Western Michigan Univ., Kalamazoo, MI (United States)] [and others

    1997-04-01

    Theoretical work has shown that the electron angular distribution and the shape of the autoionization resonances are crucial to the understanding of certain types of electron-electron correlation. Autoionization resonances in Ne (Ar) result from the decay of the excited discrete state Ne{sup *} 2s2p{sup 6} np (Ar{sup *} 3s3p{sup 6} np) into the continuum state Ne{sup +} 2s{sup 2}2p{sup 5} + e{sup {minus}} (ks,kd) (Ar{sup +} 3s{sup 2}3p{sup 5} + e{sup {minus}} (ks,kd)). Since the continuum can also be reached by direct photoionization, both paths add coherently, giving rise to interferences that produce the characteristic Beutler-Fano line shape. In this work, the authors report on quantitative angle-resolved electron spectrometry studies of (a) the Ne 2s{sup 2}2p{sup 6} {r_arrow} 2s2p{sup 6} np (n=3-5) autoionizing resonances and the 2s{sup 2}2p{sup 6} {r_arrow} 2p{sup 4}3s3p doubly excited resonance, (b) the Ar 3s{sup 2}3p{sup 6} {r_arrow} 3s3p{sup 6} np (n=4-9) autoionization resonances and extended R-matrix calculations of the angular-distribution parameters for both Ne and Ar measurements. Their results are compared with previous theoretical work by Taylor.

  17. Dual Fano and Lorentzian line profile properties of autoionizing states

    Science.gov (United States)

    Tu, B.; Xiao, J.; Yao, K.; Shen, Y.; Yang, Y.; Lu, D.; Li, W. X.; Qiu, M. L.; Wang, X.; Chen, C. Y.; Fu, Y.; Wei, B.; Zheng, C.; Huang, L. Y.; Zhang, B. H.; Tang, Y. J.; Hutton, R.; Zou, Y.

    2015-06-01

    Photon absorption spectroscopy is a powerful tool for uncovering the structure of atoms, molecules, and solids. Symmetric Lorentzian and asymmetric Fano line shapes are fundamental spectroscopic signatures related to the structural and dynamical properties. Recently, Ott et al. [Science 340, 716 (2013), 10.1126/science.1234407] successfully transferred Fano profile into Lorentzian line shape using an intense infrared laser, after excitation of autoionizing states in helium by attosecond XUV pulse. This is a very important step forward in quantum phase control. However, here we show experimentally that an autoionizing state can have both Fano and Lorentzian behavior naturally, depending on the process involved. This study utilized the inverse process of photon absorption ionization, i.e., electron ion recombination with photon emission, making sure the resonant autoionizing state is not modified or decorated by the laser fields. Our result implies that excitation of the state through different paths—for example, one photon versus multiphoton excitation, or even one step versus multistep excitation—can lead to different Fano profiles for the same resonant state. We also report an experimental determination of the energy shifts in the recombination photon-intensity peaks due to the interference between the resonant and nonresonant processes.

  18. Vibrational autoionization in PF3: Doing violence to the propensity rule

    International Nuclear Information System (INIS)

    The photoionization spectrum of PF+3 in its threshold region displays two prominent progressions of autoionization peaks. When these are analyzed, together with earlier photoabsorption studies and a photoelectron spectrum, they lead to the conclusion that vibrational autoionization is occurring, with Δν< or =-13. This conclusion stands in sharp contrast with the current theory of vibrational autoionization, which predicts a propensity rule Δν = -1. Other examples from the recent literature are summarized, to suggest that a more general theory of vibrational autoionization is required

  19. Electron capture to autoionizing states of multiply charged ions

    International Nuclear Information System (INIS)

    The present thesis investigates electron capture reactions resulting from slow collisions (V q+) and neutral gas targets (B). The energy spectra of the emitted electrons are measured; detection angle is 500. Mainly, autoionizing double capture resulting from collisions with two-electron targets (He, H2) is studied; then, the emitted electrons stem from doubly excited projectile states. The projectiles used are bare C6+, the H-like and He-like ions of C, N and O, He-like Ne8+ and Ne-like Ar8+. Excited metastable projectiles used are C5+(2s), He-like projectiles Aq+(1s2s3S) and Ar8+(...2p53s). Comparison is made with the predictions of a recently proposed extended classical barrier model, that was developed in connection with the work. This model assumes sequential capture of the electrons ('two-step' process); it predicts the realized binding enegies of the captured electrons - which may be directly determined from the autoionization spectra using only the projectile charge, the ionization potentials of the target and the collision velocity as parameters. No adjustable parameter enters into the calculations. The term energies and decay modes of the highly excited product ions themselves are studied. Generally, the autoionizing decay of these states is found to proceed preferentially to the directly adjacent lower singly excited state. Experimental evidence is presented, that triply excited states decay by successive emission of two electrons, whenever this is energetically possible. Finally, the L-MM decay in few-electron systems is considered. 314 refs.; 96 figs.; 29 tabs

  20. Multiphoton ionization of magnesium via an autoionizing state

    OpenAIRE

    Druten, van, N.J.; Trainham, R.; Muller, H.G.

    1994-01-01

    Multiphoton single and double ionization of magnesium was studied by measuring electron energy spectra and ion mass spectra using 1-ps laser pulses in the 580-595-nm wavelength and 1012-1013-W/cm2 intensity range. In single ionization the (3p)2 1S doubly excited autoionizing state, resonant at the four-photon level, is found to play an important role. Single ionization leaving the Mg+ ion in the 3p excited state is strongly enhanced when resonant with the (3p)2 1S state. The amount of above t...

  1. Predissociation and autoionization of triplet Rydberg states in molecular hydrogen

    OpenAIRE

    Dinu, L.; Picard, Y. J.; Van Der Zande, W. J.

    2004-01-01

    We present single-photon spectroscopy in molecular hydrogen starting from the metastable c(3)Pi(u)(-) state to a number of triplet nd-Rydberg states (v=0-4, n=12-20). Using fast beam spectroscopy both the autoionization channel and the predissociation channel are quantified, field free, as well as with small electric fields. Coupling with the i(3)Pi(g) state is assumed to be responsible for field-free predissociation of the v=0 Rydberg levels. The stronger observed predissociation channel of ...

  2. Theory of ultrafast autoionization dynamics of Fano resonances

    International Nuclear Information System (INIS)

    We study atomic autoionization processes in the time domain. With the emerging attosecond extreme vacuum ultraviolet and soft x-ray pulses, we first address how to characterize the time evolution of the decay of a discrete state into a degenerate continuum. A short pump beam generates a number of resonance states in a series and the nearby background continuum, and the resultant wave packet evolves with time until the full decay of the bound states. Taking the 2pns(1Po) resonance series embedded in the 2sεp(1Po) continuum in a beryllium atom as an example, the time evolution of the autoionizing wave packet in the energy domain and in coordinate space is calculated and analyzed, where Fano profiles build up in the photoelectron energy during the process. A proposed pump-probe scheme assumes that the probe beam ionizes the 2s inner electron in the wave packet. The lifetimes of the resonances and the photoelectron energy distribution can be obtained from the ionization yield vs. the time delay of the probe.

  3. Resonance-enhanced photon excitation spectroscopy of the even-parity autoionizing Rydberg states of Kr

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Kr atoms were produced in their metastable states 4p55s [3/2]2 and 4p55s’ [1/2]0 in a pulsed DC dis-charge in a beam,and subsequently excited to the even-parity autoionizing Rydberg states 4p5np’ [3/2]1,2,[1/2]1 and 4p5nf’ [5/2]3 using single photon excitation.The excitation spectra of the even-parity autoionizing resonance series from the metastable Kr were obtained by recording the autoionized Kr+ ions with time-of-flight ion detection in the photon energy range of 29000-40000 cm1.A wealth of autoionizing resonances were newly observed,from which more precise and more systematic spec-troscopic data of the level energy and quantum defects were derived.

  4. Studies of autoionizing states relevant to dielectronic recombination. Progress report, July 1, 1991--June 30, 1994

    International Nuclear Information System (INIS)

    The goal of this research program supported by grant DE-FG05-85-ER13394 is to study the properties of autoionizing states to understand in detail dielectronic recombination of ions and electrons. During the period of the present grant, July 1, 1991--June 30, 1994, we have put substantial effort into the study of autoionizing states in Mg. The first topic we have investigated is the angular distribution of electrons ejected from the autoionizing Mg 3pns and 3pnd states. Both of these sets of measurements provide more stringent tests of the K matrix calculations than do measurements of total cross sections. The second topic is the effect of static and microwave electric fields on autoionizing states. Our previous measurements in Ba have shown the profound influence of electric fields on autoionization rates and we have made extensive new measurements in both Ba and Mg. Electric fields are of real importance for dielectronic recombination, since they are present as macroscopic fields in beam experiments and as microfields in plasmas. Finally, we have begun time resolved measurements. We have set up a picosecond laser system, and we have just finished the first experiment with it. Specifically we have used picosecond excitation from a bound Mg 3pnd Rydberg wave packet to the autoionizing 3pnd states to show explicitly the correlation between the spatial location of the Rydberg electron and the frequency of the exciting light

  5. Autoionizing resonances 4d→nl in cadmium

    International Nuclear Information System (INIS)

    We measured the relative cross section and angular distribution parameter for 5s photoelectron emission in atomic cadmium across the region of the 4d→nl autoionizing resonances between 11.70 and 18.05 eV. Our results for the oscillator strengths agree with Hartree-Fock calculations, and are higher than the values reported by other experiments. Strong departure from the direct-process value of 2.0 was observed for the angular distribution parameter β, indicating singlet-to-triplet mixing in the wave functions. The mixing varies in the np resonance series, while it remains almost constant throughout the nf series. In the region of the 5p resonances there is good agreement with a semiempirical calculation of the asymmetry parameter. A number of double-electron excitations were investigated and the value of β was used to give the correct assignment to a transition at 12.856 eV. A previously unobserved transition corresponding to the promotion of a 4d electron to the 5d orbit was detected by the change in the value of β

  6. Proceedings of the workshop on some aspects of autoionization in atoms and small molecules

    Energy Technology Data Exchange (ETDEWEB)

    Berkowitz, J.; Berry, H.G.; Berry, R.S. (eds.)

    1985-11-01

    Do we really understand the phenomenon of autoionization in atoms sufficiently well to consider it a ''mature'' topic. Can we generalize our understanding to predict behavior in systems not yet studied. Can we extract physical understanding from the encouraging results of the ''many-body calculations''. Or must we still try to understand one atom at a time. Molecular autoionization is clearly more difficult. Not only must we content with ''vibrational autoionization'' as well as ''electronic autoionization'', but the competing process of predissociation must also be taken into account. In this molecular domain, we have many experiments and many phenomena. The extant theories only deal with some cases, and are not yet able to explain some prominent observations. A group consisting of theorists and experimentalists active in the field of autoionization assembled at Argonne National Laboratory for a two-day Workshop on May 2-3, 1985, to try to provide some consensus of our present understanding and to point out the most promising direction for progress in the near future. Abstracts of individual items from the workshop were prepared separately for the data base.

  7. Proceedings of the workshop on some aspects of autoionization in atoms and small molecules

    International Nuclear Information System (INIS)

    Do we really understand the phenomenon of autoionization in atoms sufficiently well to consider it a ''mature'' topic. Can we generalize our understanding to predict behavior in systems not yet studied. Can we extract physical understanding from the encouraging results of the ''many-body calculations''. Or must we still try to understand one atom at a time. Molecular autoionization is clearly more difficult. Not only must we content with ''vibrational autoionization'' as well as ''electronic autoionization'', but the competing process of predissociation must also be taken into account. In this molecular domain, we have many experiments and many phenomena. The extant theories only deal with some cases, and are not yet able to explain some prominent observations. A group consisting of theorists and experimentalists active in the field of autoionization assembled at Argonne National Laboratory for a two-day Workshop on May 2-3, 1985, to try to provide some consensus of our present understanding and to point out the most promising direction for progress in the near future. Abstracts of individual items from the workshop were prepared separately for the data base

  8. Investigation of autoionization spectra of Sm atoms using an isolated-core excitation method

    Institute of Scientific and Technical Information of China (English)

    Qin Wen-Jie; Dai Chang-Jian; Xiao Ying; Zhao Hong-Ying

    2009-01-01

    Using the isolated-core-excitation scheme and three-step laser resonance ionization spectroscopy approach, this paper, for the first time, has systematically investigated the autoionization spectra of atomic Sm, belonging to the 4f66pn/ and 4f55d6snl (l=0, 2) configurations. In the experiment, the first two tunable dye lasers are employed to excite the Srn atom from its initial state to the differcnt 4f66snl bound Rydberg states, then the third dye laser is scanned to drive the atom to the doubly-excited autoionizing states. With the above excitation scheme, the measured transition profiles of the autoionizing states are nearly symmetric, from which the level energies and widths can be easily obtained.

  9. Investigation of autoionization spectra of Sm atoms using an isolated-core excitation method

    Science.gov (United States)

    Qin, Wen-Jie; Dai, Chang-Jian; Xiao, Ying; Zhao, Hong-Ying

    2009-05-01

    Using the isolated-core-excitation scheme and three-step laser resonance ionization spectroscopy approach, this paper, for the first time, has systematically investigated the autoionization spectra of atomic Sm, belonging to the 4f66pnl and 4f55d6snl (l = 0,2) configurations. In the experiment, the first two tunable dye lasers are employed to excite the Sm atom from its initial state to the different 4f66snl bound Rydberg states, then the third dye laser is scanned to drive the atom to the doubly-excited autoionizing states. With the above excitation scheme, the measured transition profiles of the autoionizing states are nearly symmetric, from which the level energies and widths can be easily obtained.

  10. The dynamics of high autoionizing Rydberg states of Ar

    Science.gov (United States)

    Bixon, M.; Jortner, Joshua

    1995-09-01

    In this paper we present a theoretical study of the autoionization dynamics of high 2P1/2np'[3/2]1 Rydbergs (with the principal quantum numbers n=100-280) of Ar in weak homogeneous electric fields (F=0.01-1.0 V/cm), which were experimentally interrogated by time-resolved zero-electron kinetic energy (ZEKE) spectroscopy [M. Mühlpfordt and U. Even, J. Chem. Phys. 103, 4427 (1995)], and which exhibit a marked dilution (i.e., ˜2 orders of magnitude lengthening) of the lifetimes relative to those inferred on the basis of the n3 scaling law for the spectral linewidths of the np' (n=12-24) Rydbergs. The multichannel effective Hamiltonian (Heff) with several doorway state(s) (for excitation and decay) and pure escape states (for decay) was advanced and utilized to treat the dynamics of the mixed Stark manifold of the ZEKE Rydbergs. Heff of dimension 2n-1 is then constructed for a n Rydberg manifold using independent experimental information on the (l dependent) quantum defects δ(l) and the (l, K, J dependent) decay widths, which are of the form Γ0(lKJ)/(n-δ(l))3, with Γ0(lKJ) being the decay widths constants. Here, l, K, and J are the azimuthal, the electronic and the total electronic angular momentum quantum numbers, respectively. Two coupling ranges are distinguished according to the strength of the reduced electric field F¯(n,p')=(F/V cm-1)n5/ 3.4×109[δ(p')(mod1)]. Range (A); The onset of the effective coupling of the doorway and escape states, i.e., 0.7≤F¯(n,p')≤2. Range (B); The strong mixing domain F¯(n,p')≥3. The lifetimes in range (B) can be well represented by a nearly democratic mixing of all the doorway and escape states (lKJ), with the average value ≂= 2n4ℏ/[J(lJK)Γ0(lJK)]. In range (B) increases with increasing n and is only weakly F dependent. Range (A) is characterized by a hierarchy of two time scales for the decay, with a short decay component, which manifests the residue of the doorway state, and a distribution of very long lifetimes

  11. [Laser resonance ionization spectroscopy of even-parity autoionization states of cerium atom].

    Science.gov (United States)

    Li, Zhi-ming; Zhu, Feng-rong; Zhang, Zi-bin; Ren, Xiang-jun; Deng, Hu; Zhai, Li-hua; Zhang, Li-xing

    2004-12-01

    This paper describes the investigation of even-parity autoionization states of cerium atoms by three-step three-color resonance ionization spectroscopy (RIS). Twenty-seven odd-parity highly excited levels, whose transition probability is high, were used in this research. One hundred and forty-one autoionization states were found by these channels with the third-step laser scanning in the wavelength range of 634-670 nm. The ionization probabilities of different channels, which had higher cross sections, were compared. On the basis of this, eight optimal photoionization schemes of cerium atom have been given. PMID:15828309

  12. Studies of autoionizing states relevant to dielectronic recombination: Progress report, July 1, 1986-June 30, 1987

    International Nuclear Information System (INIS)

    Systematic studies of the Sr 5pns and 5pnd autoionizing states are described. Specifically the experimental determination of energy levels and autoionization rates and interchannel interaction from the total excitation spectra is described as well as the quantum defect theory analysis of these diverse data leading to the determination of a few physically significant parameters. In addition measurements of the angular and energy distributions of the ejected electrons using a recently constructed energy analyzer are described. Finally, the development of the theoretical framework to analyze these data is described

  13. Laser two-photon ionization and autoionization spectroscopy of molecules in the liquid phase

    International Nuclear Information System (INIS)

    The observation of autoionizing states of molecules in the liquid phase together with one- and two-photon ionization threshold measurements obtained using a laser conductivity technique are reported. Coherent versus resonant (stepwise) two-photon excitation in the photoionization process in solutions is discussed

  14. Electromagnetically induced transparency in systems with degenerate autoionizing levels in Λ-configuration

    Czech Academy of Sciences Publication Activity Database

    Dinh, T.B.; Leoński, W.; Long, V.C.; Peřina ml., Jan

    2013-01-01

    Roč. 43, č. 3 (2013), s. 471-484. ISSN 0078-5466 Institutional support: RVO:68378271 Keywords : electromagnetically induced transparency (EIT) * lambda configuration * autoionizing states * double Fano profile Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.643, year: 2013

  15. Decay of autoionizing states in time-dependent density functional and reduced density matrix functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Kapoor, Varun; Brics, Martins; Bauer, Dieter [Institut fuer Physik, Universitaet Rostock, 18051 Rostock (Germany)

    2013-07-01

    Autoionizing states are inaccessible to time-dependent density functional theory (TDDFT) using known, adiabatic Kohn-Sham (KS) potentials. We determine the exact KS potential for a numerically exactly solvable model Helium atom interacting with a laser field that is populating an autoionizing state. The exact single-particle density of the population in the autoionizing state corresponds to that of the energetically lowest quasi-stationary state in the exact KS potential. We describe how this exact potential controls the decay by a barrier whose height and width allows for the density to tunnel out and decay with the same rate as in the ab initio time-dependent Schroedinger calculation. However, devising a useful exchange-correlation potential that is capable of governing such a scenario in general and in more complex systems is hopeless. As an improvement over TDDFT, time-dependent reduced density matrix functional theory has been proposed. We are able to obtain for the above described autoionization process the exact time-dependent natural orbitals (i.e., the eigenfunctions of the exact, time-dependent one-body reduced density matrix) and study the potentials that appear in the equations of motion for the natural orbitals and the structure of the two-body density matrix expanded in them.

  16. Phase-controlled stair-step decay of autoionizing radial wave packets

    International Nuclear Information System (INIS)

    The time-dependent survival probabilities of autoionizing 4pNd wave packets in calcium have been measured. Femtosecond laser pulses induce sequential isolated-core excitations of singly excited 4sNd radial wave packets to create and probe the nonstationary doubly excited states. Stair step rather than exponential decay of the wave packets is observed. Moreover, we show that the autoionization lifetime can be varied by a factor of five by adjusting the relative phases of the constituent eigenstates in the packet. The stair-step decay structure and its dependence on the wave packet phase is interpreted using an intuitive time-domain picture. The experimental results are in excellent agreement with a K-matrix based, 28-channel quantum-defect theory calculation as well as with an approximate two-channel formulation

  17. Transitions from autoionized states of Sb, Te and I in the 100-260 A region

    International Nuclear Information System (INIS)

    The spectra of antimony, tellurium and iodine were photographed in the 100-200 A region on a 2 m grazing incidence spectrograph at the Antigonish laboratory. 10, 16 and 4 transitions from the autoionized states of Sb, Te and I ions, respectively, belonging to Sb IV, V, VI; Te VI and VII, and I VI, VII and VIII have been classified. Hartree-Fock (HF) calculations were used to interpret the classifications and the line widths. (orig.)

  18. Experimental study of bound and autoionizing Rydberg states of the europium atom

    Science.gov (United States)

    Xiao, Ying; Dai, Chang-Jian; Qin, Wen-Jie

    2010-06-01

    An isolated-core-excitation (ICE) scheme and stepwise excitation are employed to study the highly excited states of the europium atom. The bound europium spectrum with odd parity in a region of 42400-43500 cm-1 is measured, from which spectral information on 38 transitions, such as level position and relative intensity, can be deduced. Combined with information about excitation calibration and the error estimation process, the selection rules enable us to determine the possible values of total angular momentum J for the observed states. The autoionization spectra of atomic europium, belonging to the 4f76pnl (l = 0, 2) configurations, are systematically investigated by using the three-step laser resonance ionization spectroscopy (RIS) approach. With the ICE scheme, all the experimental spectra of the autoionizing states have nearly symmetric profiles whose peak positions and widths can be easily obtained. A comparison between our results and those from the relevant literature shows that our work not only confirms many reported states, but also discovers 14 bound states and 16 autoionizing states.

  19. Polarized electron correlations near auto-ionizing states of zinc atoms

    Science.gov (United States)

    Williams, James; Pravica, Luka; Samarin, Sergey

    2015-09-01

    Multi-electron metal atoms find new applications in diverse structures with spin and momentum-dependent properties having significance in determining material functionalities. Electron correlations effects are determined from scattering kinematics of spin-polarized electrons exciting zinc atoms near autoionizing states up to 16 eV. Previous studies of the 4p 3 , 1P1 , 4 d,5 d,6d3D1 , 2 , 3 and 4 d,5d1D1 excited states observed photon decay intensities and scattered electron energies and angles in the energy region of the 3d94s24 p autoionizing states up to 12 eV. Strong electron correlations and active roles of 3 d electrons were evident. Our observations of the 53S excited state for electron energies up to 16 eV show dominant 3 d core-excited negative-ion resonances and strong Post-Collision Interaction (PCI). For low energies of scattered and ejected electrons, after near-threshold excitation of the 3d94s24 p autoionizing states, a large transfer of orbital angular momentum is evident. Results include angular differential elastic scattering and excitation functions, ``integrated'' Stokes polarization parameters and spin up/down asymmetries indicating spin-orbit interaction and electron exchange effects. School of Physics

  20. Resonance enhanced multiphoton ionization photoelectron spectra of CO2. III. Autoionization dominates direct ionization

    International Nuclear Information System (INIS)

    In (3+1) resonance enhanced multiphoton ionization photoelectron spectra (REMPI-PES) of CO2, photoionization competes with dissociation. In addition to direct photoionization, autoionization is possible through accidental resonances embedded in the continuum at the four-photon level. Photoabsorption from these long-lived autoionizing states leads to resonance enhanced above threshold absorption (REATA). REATA produces photoelectron terminations on the C state of CO2+. Previous experiments did not indicate whether the dissociation occurred at the three-photon level or four-photon level. REMPI-PES of CO2 via several Rydberg states have been collected at a number of laser intensities, and it was found that the photoelectron spectra terminating on each individual ionic state do not change over the range of experimentally available laser intensities. This indicates that the dissociation of CO2 occurs at the four-photon level. The long vibrational progressions in the PES indicate that the dominant ionization process is autoionization rather than direct ionization. Relative intensities of the X and C state components of the PES do change with intensity, confirming the C state assignment and its five-photon mechanism

  1. Competition among autoionization, predissociation, and ion-pair formation in molecular hydrogen

    International Nuclear Information System (INIS)

    We have investigated autoionization, predissociation, and ion-pair formation highly excited states of molecular hydrogen by using double-resonance excitation via the E,F 1Σg+, v=6 level. The energetic threshold for ion-pair formation occurs just below the H2+ x 2Σg+, v+=9 ionization threshold. The spectrum in this region was studied by using conventional and constant-ionic-state photoelectron spectroscopy, by monitoring the H- production, and by detecting dissociation products by ionization with a third laser. The decay dynamics in this region are extremely rich, because the excited levels may decay by rotational and vibrational autoionization, by predissociation to neutral H + H* (n=2,3,4), by predissociation to the ion pair H+ + H-, and by fluorescence. In addition, the dissociative potential curve of the 2pσu3sσg1Σu+ doubly excited electronic state crosses the H2+ x 2Σg+ potential curve in the same energy ion, and the electronic autoionization of this state is found to significantly influence these decay processes

  2. An experimental study of the role of autoionizing states of H2 (D2) in the production of energetic protons (deuterons) by electron impact

    International Nuclear Information System (INIS)

    The autoionizing state study seemed interesting to be taken up again in energy ranges corresponding to formation thresholds, a device well adapted to this range was available concerning electron measurements. Among other things, the overlapping autoionizing states have been displayed; proton kinetic energy distribution appropriate to each state at its formation threshold have been got. The whole of these results represents a proton (and D+) production mechanism study contribution via autoionizing states. The theory used to describe autoionization cross-section calculations are recalled. Experimental results are presented, discussed, compared to experimental results and theoretical predictions

  3. Calculation of autoionization positions and widths with applications to Penning ionization reactions. [Miller golden rule formula

    Energy Technology Data Exchange (ETDEWEB)

    Isaacson, A.D.

    1978-08-01

    Using an approximate evaluation of Miller's golden rule formula to calculate autoionization widths which allows for the consideration only of L/sup 2/ functions, the positions and lifetimes of the lowest /sup 1/,/sup 3/P autoionizing states of He have been obtained to reasonable accuracy. This method has been extended to molecular problems, and the ab initio configuration interaction potential energy and width surfaces for the He(2/sup 3/S) + H/sub 2/ system have been obtained. Quantum mechanical close-coupling calculations of ionization cross sections using the complex V* - (i/2) GAMMA-potential have yielded rate constants in good agreement with the experimental results of Lindinger, et al. The potential energy surface of the He(2/sup 1/S) + H/sub 2/ system has also been obtained and exhibits not only a high degree of anisotropy, but also contains a relative maximum for a perpendicular (C/sub 2//sub v/) approach which appears to arise from s-p hybridization of the outer He orbital. However, similar ab initio calculations on the He(2/sup 1/S) + Ar system do not show such anomalous structure. In addition, the complex poles of the S-matrix (Siegert eigenvalues) were calculated for several autoionizing states of He and H/sup -/, with encouraging results even for quite modest basis sets. This method was extended to molecular problems, and results obtained for the He(2/sup 3/S) + H and He(2/sup 1/S) + H systems. 75 references.

  4. Spectroscopy of autoionizing states contributing to electron-impact ionization of ions

    International Nuclear Information System (INIS)

    In electron-ion crossed-beam experiments we have used a fast electron-energy scanning technique to detect fine details in ionization cross sections. We obtained data with a relative point to point uncertainty of less than 0.1%. The electron energy spread at 100 eV (15 mA beam current) is 0.4 eV. Thus we were able to measure state-resolved excitation-autoionization contributions and to demonstrate new ionization mechanisms involving dielectric capture of the projectile electron with subsequent emission of several electrons. (orig.)

  5. Two-step two-photon-resonant three-photon autoionization of a divalent atomic system

    International Nuclear Information System (INIS)

    We theoretically examine the situation in which a divalent atom or atomic ion, resonantly excited via absorption of two photons of a laser with intensity I1 and ω1, is ionized with subsequent absorption of another photon of either the same laser or a second laser with intensity I2 and frequency ω2 through autoionizing resonances. The relevant atomic parameters are calculated from wave functions obtained with finite B-spline bases for two-electron configurations, and the density matrix equations are numerically solved for the two-step ionization scheme.

  6. Observation of autoionization resonances in uranium by step-wise laser photoionization

    International Nuclear Information System (INIS)

    A large number of autoionization resonances have been observed in uranium in the energy range 50,590-51,560 cm-1 by two-step three-photon ionization technique, using two copper vapor laser pumped dye lasers. A Rydberg series converging to the ionization limit of UII at 1749 cm-1 (6L13/2) has been identified. Some of these resonances are very narrow with a fwhm of 0.1 cm-1. Possible origins of these are discussed. (orig.)

  7. Non-LTE profiles of the Al I autoionization lines. [for solar model atmospheres

    Science.gov (United States)

    Finn, G. D.; Jefferies, J. T.

    1974-01-01

    A non-LTE formulation is given for the transfer of radiation in the autoionizing lines of neutral aluminum at 1932 and 1936 A through both the Bilderberg and Harvard-Smithsonian model atmospheres. Numerical solutions for the common source function of these lines and their theoretical line profiles are calculated and compared with the corresponding LTE profiles. The results show that the non-LTE profiles provide a better match with the observations. They also indicate that the continuous opacity of the standard solar models should be increased in this wavelength region if the center-limb variations of observed and theoretical profiles of these lines are to be in reasonable agreement.

  8. Observation of autoionizing states of beryllium by resonance ionization mass spectrometry

    International Nuclear Information System (INIS)

    We have made the first observations of the Be 2p21S state, and of high-lying members of the Rydberg series 2pnd 1P0 (n less than or equal to 16), by resonance ionization mass spectrometry (RIMS). The energy of the 1S state agrees well with theoretical predictions, if corrections are made for intershell electron correlations. These results show that precision specroscopy can be performed by RIMS with samples of a few hundred atoms, and that direct multiphoton excitation of autoionizing states may be a useful new addition to the existing catalogue of resonance ionization schemes

  9. Laser-assisted-autoionization dynamics of helium resonances with single attosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Wei-Chun; Lin, C. D. [J. R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States); Zhao Songfeng [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China)

    2011-09-15

    The strong coupling between two autoionizing states in helium is studied theoretically with the pump-probe scheme. An isolated 100-as XUV pulse is used to excite helium near the 2s2p({sup 1} P) resonance state in the presence of an intense infrared (IR) laser. The laser field introduces strong coupling between 2s2p({sup 1} P) and 2p{sup 2}({sup 1} S) states. The IR also can ionize helium from both autoionizing states. By changing the time delay between the XUV and the IR pulses, we investigated the photoelectron spectra near the two resonances. The results are used to explain the recent experiment by Gilbertson et al.[Phys. Rev. Lett. 105, 263003 (2010)]. Using the same isolated attosecond pulse and a 540-nm laser, we also investigate the strong coupling between 2s2p({sup 1} P) and 2s{sup 2}({sup 1} S) by examining how the photoelectron spectra are modified versus the time delay and the possibility of observing Autler-Townes doublet in such experiments.

  10. Laser optogalvanic observations and MQDT analysis of mp5nd J = 3 autoionizing resonances in Ar, Kr and Xe

    International Nuclear Information System (INIS)

    We report new measurements of the spectra of argon, krypton and xenon in the autoionization region using a two-step resonant laser excitation and optogalvanic detection technique. By selecting (m)p5(m + 1)p'[3/2]2 as an intermediate state (m = 4, 5 and 6 for Ar, Kr and Xe, respectively), we have been able to single out the (m)p5nd[5/2]3 autoionizing resonances in their spectra. The MQDT parameters have been derived from the analysis of the series perturbations among the (m)p5nd[5/2]3 (m)p5nd[7/2]3 and (m)p5nd'[5/2]3 series in the discrete region using the phase shifted formulation of the three-channel quantum defect theory and from the line profile analysis of the autoionizing resonances above the first ionization threshold. The predicted reduced widths for the autoionizing resonances based on the series perturbation analysis show good agreement with those of the experimentally observed profiles. Accurate values of the resonance energies, quantum defects and reduced widths are reported

  11. Long-time joint spectra and entanglement of two photoelectrons originating in interacting auto-ionization systems

    Czech Academy of Sciences Publication Activity Database

    Peřina ml., Jan; Lukš, A.; Leoński, W.

    2015-01-01

    Roč. 48, č. 11 (2015), s. 115007. ISSN 0953-4075 Institutional support: RVO:68378271 Keywords : two-electron ionization spectra * auto-ionization * dipole-dipole interaction * Fano model * bipartite entanglement * quadratic negativity Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.975, year: 2014

  12. The 4p6 autoionization cross section of Rb atoms excited by low-energy electron impact

    International Nuclear Information System (INIS)

    The autoionization cross section of rubidium atoms was obtained by measuring the total normalized intensities of ejected-electron spectra arising from the decay of the 4p5n1l1n2l2 autoionizing levels. The electron impact energy range from the 4p6 excitation threshold at 15.31 up to 50 eV was investigated. The cross section reaches the maximum value of (2.9 ± 0.6) × 10−16 cm2 at 21.8 eV impact energy. The general behaviours of the cross section and the role of particular autoionizing configurations in its formation were considered on the basis of large-scale configuration interaction calculations of energies, cross sections, autoionization probabilities in 5snl(n ⩽ 7; l ⩽ 4) and 4d nl(n ⩽ 5; l ⩽ 2) configurations as well as the measured excitation functions for the lowest levels in 5s2 and 4d5s configurations. The resonance behaviour of the cross section between 15.3 and 18.5 eV impact energy is caused exclusively by the negative-ion resonances present close to the excitation thresholds of the (5s2)2P and (4d5s)4P autoionizing levels. At higher impact energies, the autoionization cross section is composed of contributions from the high-lying quartet and doublet levels in 4d5s, 5p and 5s5p, 5d, 6s, 6p configurations. From the comparison of the present data with available experimental and calculated ionization cross sections, the 5s + 4p6 direct ionization cross section of rubidium atoms was determined with the maximum value of (7.2 ± 2.2) × 10−16 cm2 at 36 eV. It was also found that the 4p6 excitation–autoionization is the dominant indirect ionization process contributing over 30% of the total single ionization of rubidium atoms by electron impact in the 15.3–50 eV energy range. (paper)

  13. Autoionization of spin-polarized metastable helium in tight anisotropic harmonic traps

    CERN Document Server

    Beams, Timothy J; Peach, Gillian

    2007-01-01

    Spin-dipole mediated interactions between tightly confined metastable helium atoms couple the spin-polarized quintet ${}^{5}\\Sigma^{+}_{g}$ state to the singlet ${}^{1}\\Sigma^{+}_{g}$ state from which autoionization is highly probable, resulting in finite lifetimes for the trap eigenstates. We extend our earlier study on spherically symmetric harmonic traps to the interesting cases of axially symmetric anisotropic harmonic traps and report results for the lowest 10 states in "cigar-like" and "pancake-like" traps with average frequencies of 100 kHz and 1 MHz. We find that there is a significant suppression of ionization, and subsequent increase in lifetimes, at trap aspect ratios $A=p/q$, where $p$ and $q$ are integers, for those states that are degenerate in the absence of collisions or spin-dipole interactions.

  14. Calculation of dissociating autoionizing states using the block diagonalization method: Application to N2H

    International Nuclear Information System (INIS)

    We report the calculation of preliminary potential surfaces necessary to treat dissociative recombination (DR) of electrons with N2H+. We performed multi-reference, configuration interaction calculations with a large active space for N2H+ and N2H, using the GAMESS electronic structure code. Rydberg-valence coupling is strong in N2H, and a systematic procedure is desirable to isolate the appropriate dissociating, autoionizing states. We used the block diagonalization method, which requires only modest additional effort beyond the standard methodology. We treated both linear and bent geometries of the molecules, with N2 fixed at its equilibrium separation. The results indicate that the crossing between the dissociating neutral curve and the initial ion potential is not favorably located, suggesting that the direct mechanism for DR will be small. Dynamics calculations using the multi-configuration, time-dependent Hartree (MCTDH) method confirm this conclusion.

  15. Auto-ionic - microscopy analysis of radiation defects in Y-Ba-Cu-O monocrystals

    International Nuclear Information System (INIS)

    Defective structure of YBa2Cu3O7-x monocrystal samples with 1-2-3-type structure, irradiated by Ar+ ions with 35 keV energy, is studied. All samples were observed during the first stage by means of ion microscope, whereat their apexes were formed through the field evaporation. Thereafter the samples were irradiated at a facility for ion implantation by Ar+ ions. This was followed by repeated analysis of samples in auto-ion microscope, whereby the obtained microscopic images were registered by photographing from fluorescent screen as well as by means of television camera, connected with the IBM-type computer. Program package was applied for further machine processing. 21 refs., 2 figs

  16. Collective Autoionization in Multiply-Excited Systems: A novel ionization process observed in Helium Nanodroplets

    CERN Document Server

    LaForge, A C; Brauer, N; Coreno, M; Devetta, M; Di Fraia, M; Finetti, P; Grazioli, C; Katzy, R; Lyamayev, V; Mazza, T; Mudrich, M; OKeeffe, P; Ovcharenko, Y; Piseri, P; Plekan, O; Prince, K C; Richter, R; Stranges, S; Callegari, C; Moeller, T; Stienkemeier, F

    2013-01-01

    Free electron lasers (FELs) offer the unprecedented capability to study reaction dynamics and image the structure of complex systems. When multiple photons are absorbed in complex systems, a plasma-like state is formed where many atoms are ionized on a femtosecond timescale. If multiphoton absorption is resonantly-enhanced, the system becomes electronically-excited prior to plasma formation, with subsequent decay paths which have been scarcely investigated to date. Here, we show using helium nanodroplets as an example that these systems can decay by a new type of process, named collective autoionization. In addition, we show that this process is surprisingly efficient, leading to ion abundances much greater than that of direct single-photon ionization. This novel collective ionization process is expected to be important in many other complex systems, e.g. macromolecules and nanoparticles, exposed to high intensity radiation fields.

  17. Recent (e,2e) studies: laser excited atoms, autoionization, Auger processes, and thin films

    International Nuclear Information System (INIS)

    The (e,2e) process, in which the kinematics of the electrons involved in an ionizing collision are completely determined, is capable of revealing a rich variety of information. Depending on the kinematics employed, it is possible to investigate in detail either the ionization mechanism itself or to use the reaction to elucidate the structure of the target system and the ion. When used to investigate structure, the technique is now generally known as electron momentum spectroscopy (EMS). The results of various recent (e,2e) measurements carried out at Flinders University are reported. These include the first measurements of the electron momentum distributions of excited target state, the first measurements of the momentum distributions from an oriented target atom, the detailed measurements of correlations in the autoionizing region of helium, correlations in the inner shell ionization of argon, and finally the measurement of spectral momentum densities for amorphous carbon. 21 refs., 11 figs

  18. Interference stabilization of autoionizing states in molecular $N_2$ studied by time- and angular-resolved photoelectron spectroscopy

    CERN Document Server

    Eckstein, Martin; Yang, Chung-Hsin; Sansone, Giuseppe; Vrakking, Marc J J; Ivanov, Misha; Kornilov, Oleg

    2016-01-01

    An autoionizing resonance in molecular N$_2$ is excited by an ultrashort XUV pulse and probed by a subsequent weak IR pulse, which ionizes the contributing Rydberg states. Time- and angular-resolved photoelectron spectra recorded with a velocity map imaging spectrometer reveal two electronic contributions with different angular distributions. One of them has an exponential decay rate of $20\\pm5$ fs, while the other one is shorter than 10 fs. This observation is interpreted as a manifestation of interference stabilization involving the two overlapping discrete Rydberg states. A formalism of interference stabilization for molecular ionization is developed and applied to describe the autoionizing resonance. The results of calculations reveal, that the effect of the interference stabilization is facilitated by rotationally-induced couplings of electronic states with different symmetry.

  19. Theoretical investigation of the hypothesized crossing between the Penning and atomic autoionizing states of He+K

    Energy Technology Data Exchange (ETDEWEB)

    Padial, N.T.; Martin, R.L.; Cohen, J.S.; Lane, N.F.

    1989-03-01

    The Penning ionization interaction He(12s/sup 3/S)+K(3p/sup 6/4s) and the atomic autoionizing state interaction He(1s/sup 2/)+K(3p/sup 5/4s/sup 2/) have been determined in a configuration-interaction calculation utilizing a basis set designed to treat these two states equitably. In contrast to an earlier calculation, the corresponding two potential curves are found not to cross. This finding puts in question the original speculation that the observed large He/sup */+K ionization cross section is due partially to collisional excitation of atomic states that subsequently autoionize. However, the calculated Penning ionization cross section is still in agreement with the experimental measurement.

  20. Identification of autoionizing states of atomic chromium for resonance photo-ionization at the ISOLDE-RILIS

    OpenAIRE

    Goodacre, T Day; Chrysalidis, K; Fedorovc, D; Fedosseev, V. N.; Marsh, B A; Molkanov, P; Rossel, R.E.; Rothe, S.; Seiffert, C.

    2015-01-01

    The resonance ionization laser ion source (RILIS) is the principal ion source of the ISOLDE radioactive beam facility based at CERN. Using the method of in-source resonance ionization spectroscopy, an optimal three-step, three-resonance photo-ionization scheme has been developed for chromium. The scheme uses an ionizing transition to one of the 14 newly observed autoionizing states. This work increases the range of ISOLDE-RILIS ionized beams to 32 chemical elements. Details of the spectroscop...

  1. Atomic-number dependence of the magnetic-sublevel population in the autoionization state formed in dielectronic recombination

    OpenAIRE

    Hu, Zhimin; Li, Yueming; Han, Xiaoying; Kato, Daiji; Tong, Xiaomin; Watanabe, Hirofumi; Nakamura, Nobuyuki

    2014-01-01

    The magnetic-sublevel population of the autoionization state formed in dielectronic recombination (DR) of highly charged heavy ions has been experimentally investigated by combining two types of measurements with an electron beam ion trap. The two different measurements are the differential x-ray measurement at 90∘ with respect to the electron beam and the integral resonance-strength measurement. The alignment parameter, which denotes the magnetic-sublevel population distribution, has been ob...

  2. Enhanced asymmetry in few-cycle attosecond pulse ionization of He in the vicinity of autoionizing resonances

    International Nuclear Information System (INIS)

    By solving the two-active-electron, time-dependent Schrödinger equation in its full dimensionality, we investigate the carrier-envelope phase (CEP) dependence of single ionization of He to the He+(1s) state triggered by an intense few-cycle attosecond pulse with carrier frequency ω corresponding to the energy ℏω = 36 eV. Effects of electron correlations are probed by comparing projections of the final state of the two-electron wave packet onto field-free highly correlated Jacobi matrix wave functions with projections onto uncorrelated Coulomb wave functions. Significant differences are found in the vicinity of autoionizing resonances. Owing to the broad bandwidths of our 115 and 230 as pulses and their high intensities (1–2 PW cm−2), asymmetries are found in the differential probability for ionization of electrons parallel and antiparallel to the linear polarization axis of the laser pulse. These asymmetries stem from interference of the one- and two-photon ionization amplitudes for producing electrons with the same momentum along the linear polarization axis. Whereas these asymmetries generally decrease with increasing ionized electron kinetic energy, we find a large enhancement of the asymmetry in the vicinity of two-electron doubly excited (autoionizing) states on an energy scale comparable to the widths of the autoionizing states. The CEP dependence of the energy-integrated asymmetry agrees very well with the predictions of time-dependent perturbation theory (Pronin et al 2009 Phys. Rev. A 80 063403). (paper)

  3. Observation of autoionization dynamics and sub-cycle quantum beating in electronic molecular wave packets

    Science.gov (United States)

    Reduzzi, M.; Chu, W.-C.; Feng, C.; Dubrouil, A.; Hummert, J.; Calegari, F.; Frassetto, F.; Poletto, L.; Kornilov, O.; Nisoli, M.; Lin, C.-D.; Sansone, G.

    2016-03-01

    The coherent interaction with ultrashort light pulses is a powerful strategy for monitoring and controlling the dynamics of wave packets in all states of matter. As light presents an oscillation period of a few femtoseconds (T = 2.6 fs in the near infrared spectral range), an external optical field can induce changes in a medium on the sub-cycle timescale, i.e. in a few hundred attoseconds. In this work, we resolve the dynamics of autoionizing states on the femtosecond timescale and observe the sub-cycle evolution of a coherent electronic wave packet in a diatomic molecule, exploiting a tunable ultrashort extreme ultraviolet pulse and a synchronized infrared field. The experimental observations are based on measuring the variations of the extreme ultraviolet radiation transmitted through the molecular gas. The different mechanisms contributing to the wave packet dynamics are investigated through theoretical simulations and a simple three level model. The method is general and can be extended to the investigation of more complex systems.

  4. Identification of weak autoionizing resonances observed through fluorescence from the satellite states of Ar{sup +}

    Energy Technology Data Exchange (ETDEWEB)

    McLaughlin, K.W.; Yenen, O.; Samson, J.A.R. [Univ. of Nebraska, Lincoln, NE (United States)] [and others

    1997-04-01

    Photoionization accompanied by excitation of the residual ionic state violates an independent electron model since, according to QED, photons interact only with individual electrons. By allowing measurements at a threshold event with high resolution, the observation of the fluorescence from the decay of these excited states (satellite states) is a sensitive method in the study of electron-electron interactions, providing complementary information to photoelectron spectroscopy. In the measurements reported here, an atomic beam of argon has been photoionized with 34 to 39 eV synchrotron radiation at beamline 9.0.1 of the Advanced Light Source. This energy range encompasses the 3p{sup 4} [{sup 3}P] 4p {sup 4}P, {sup 2}P, and {sup 2}D as well as the [{sup 1}D]4p {sup 2}F satellite states of Ar{sup +}. By observing the fine-structure resolved fluorescence from these satellite states, new Rydberg series and extensions of previously known series have been resolved with an energy resolution of 3 meV. With the high photon flux available from the high resolution monochromator of beamline 9.0.1, even the weakly excited [{sup 3}P] 4p ({sup 2}S) ns,d autoionizing structure has been observed for the first time.

  5. The VMI study on angular distribution of ejected electrons from Eu 4f76p1/26d autoionizing states

    Institute of Scientific and Technical Information of China (English)

    张开; 沈礼; 董程; 戴长建

    2015-01-01

    The combination of a velocity mapping imaging technique and mathematical transformation is adopted to study the angular distribution of electrons ejected from the Eu 4f76p1/26d autoionizing states, which are excited with a three-step excitation scheme via different Eu 4f76s6d 8DJ (J=5/2, 7/2, and 9/2) intermediate states. In order to determine the energy dependence of angular distribution of the ejected electrons, the anisotropic parameters are measured in the spectral profile of the 6p1/26d autoionizing states by tuning the wavelength of the third-step laser across the ionic resonance lines of the Eu 6s+→ 6p+. The configuration interaction is discussed by comparing the angular distributions of ejected electrons from the different states. The present study reveals the profound variations of anisotropic parameters in the entire region of autoionization resonance, highlighting the complicated nature of the autoionization process for the lowest member of 6p1/26d autoionization series.

  6. Charge-exchange-induced two-electron satellite transitions from autoionizing levels in dense plasmas.

    Science.gov (United States)

    Rosmej, F B; Griem, H R; Elton, R C; Jacobs, V L; Cobble, J A; Faenov, A Ya; Pikuz, T A; Geissel, M; Hoffmann, D H H; Süss, W; Uskov, D B; Shevelko, V P; Mancini, R C

    2002-11-01

    Order-of-magnitude anomalously high intensities for two-electron (dielectronic) satellite transitions, originating from the He-like 2s(2) 1S0 and Li-like 1s2s(2) (2)S(1/2) autoionizing states of silicon, have been observed in dense laser-produced plasmas at different laboratories. Spatially resolved, high-resolution spectra and plasma images show that these effects are correlated with an intense emission of the He-like 1s3p 1P-1s(2) 1S lines, as well as the K(alpha) lines. A time-dependent, collisional-radiative model, allowing for non-Maxwellian electron-energy distributions, has been developed for the determination of the relevant nonequilibrium level populations of the silicon ions, and a detailed analysis of the experimental data has been carried out. Taking into account electron density and temperature variations, plasma optical-depth effects, and hot-electron distributions, the spectral simulations are found to be not in agreement with the observations. We propose that highly stripped target ions (e.g., bare nuclei or H-like 1s ground-state ions) are transported into the dense, cold plasma (predominantly consisting of L- and M-shell ions) near the target surface and undergo single- and double-electron charge-transfer processes. The spectral simulations indicate that, in dense and optically thick plasmas, these charge-transfer processes may lead to an enhancement of the intensities of the two-electron transitions by up to a factor of 10 relative to those of the other emission lines, in agreement with the spectral observations. PMID:12513602

  7. Theoretical study of autoionizing states and lifetimes in multiply excited argon

    International Nuclear Information System (INIS)

    Autoionization transition rates have been calculated for a representative selection of spectroscopic terms of multiply excited argon atoms. The states selected consist of two highly excited electrons in the Rydberg states (n = 4,5), together with one or two vacancies in the valence shell (n = 3) and a single vacancy in the inner shell (n = 2). Configuration mixing was found to be important. The eigenvalues and eigenstates were found by the truncated diagonalization method (i.e., QHQ is diagonalized). The effect of term splitting was included by calculating the contributions of the quadrupole terms in the interelectron repulsive potentials. The applicability of the msnp +- classification scheme suggested by Cooper, Fano, and Prats for helium was investigated for the outer electrons. Among the doubly excited outer-shell states found here are pairs of states which predominantly have the characteristics of 45sp + and 45sp - levels. However, states of the less-ionized system show less +- character because the shielding of the nucleus by the core electrons removes the degeneracy in energy of 4s5p and 5s4p levels, so there is less mixing when there is more shielding. The lifetimes of the valence-electron (n = 3) shell decay range from approximately 10-17 to approximately 10-13 sec. The lifetimes of the highly excited electrons separate into two widely disparate ranges: from approximately 10-17 to approximately 10-16 sec and from approximately 10-13 to approximately 10-11 sec. The outer-shell states that have lifetimes shorter than the inner shell are those from which it is energetically possible for an electron to fall to a 4s, 4p, or 3d subshell, while the longer lifetimes are for states which can decay only to the n = 3 core

  8. Identification of autoionizing states of atomic chromium for resonance photo-ionization at the ISOLDE-RILIS

    CERN Document Server

    Goodacre, T Day; Fedorovc, D; Fedosseev, V N; Marsh, B A; Molkanov, P; Rossel, R E; Rothe, S; Seiffert, C

    2015-01-01

    The resonance ionization laser ion source (RILIS) is the principal ion source of the ISOLDE radioactive beam facility based at CERN. Using the method of in-source resonance ionization spectroscopy, an optimal three-step, three-resonance photo-ionization scheme has been developed for chromium. The scheme uses an ionizing transition to one of the 14 newly observed autoionizing states. This work increases the range of ISOLDE-RILIS ionized beams to 32 chemical elements. Details of the spectroscopic studies are described and the new ionization scheme is summarized. A link to the complete version of this document will be added here following publication:

  9. Rydberg and autoionization Tm states investigation by the three-step laser excitation and electric field ionization method

    International Nuclear Information System (INIS)

    The energies of 190 Rydberg and autoionization 4f136 snp-states of the Tm atom (ground electron configuration 4f136s2, nuclear charge Z=69) have been measured by the laser multistep excitation with subsequent electric field ionization method. The investigation range of these states has been extended towards states with higher and lower values of the principal quantum number. As a result the energies of 160 states have been obtained for the first time. The experiment has been carried out on an automated laser photoionization spectrometer. The measurement accuracy has been ±0.5 cm-1. (orig.)

  10. Resonance-enhanced multiphoton-ionization photoelectron spectroscopy of even-parity autoionizing Rydberg states of atomic sulphur

    Science.gov (United States)

    Woutersen, S.; Milan, J. B.; Buma, W. J.; de Lange, C. A.

    1997-05-01

    Several previously unobserved Rydberg states of the sulphur atom above the lowest ionization threshold are identified and assigned using (2+1) resonance-enhanced multiphoton-ionization photoelectron spectroscopy. All states were accessed by two-photon transitions from either the 3P ground or the 1D excited state, prepared by in situ photodissociation of H2S. The observed states derive from the (2Do)5p and (2Po)4p configurations. For the (2Do)5p 3F and (2Po)4p 3D triplets, extensive photoelectron spectroscopic studies enable a detailed comparison of the autoionization and photoionization rates of these states.

  11. Angular momenta and energies of high-lying even-parity autoionizing states of the gadolinium atom investigated by using three-step photoionization

    International Nuclear Information System (INIS)

    Sixteen even-parity autoionizing states of the Gd atom in the range of 50600 - 51000 cm-1 were newly investigated using resonance ionization mass spectroscopy (RIMS). The observed autoionizing states nearly had symmetrical line porfiles. The angular momenta of the J=0 states were determined by using the polarization selection rules in the J=2 → J=2 → J=1 → J=0 transition excited by linearly polarized laser beams. The J=1 and the J=2 states were identified by observing the variations of the ion spectra with changing total angular momenta of the intermediate states

  12. Resonance excitation of the (4p55s2)2P3/2,1/2 autoionizing states in Rb atoms by electron impact

    International Nuclear Information System (INIS)

    The near-threshold excitation dynamics of the 4p55s22P3/2,1/2 autoionizing states in rubidium atoms was studied experimentally by measuring the ejected-electron excitation functions and theoretically by applying a fully relativistic Dirac B-spline R-matrix (close-coupling) model. As in the previously studied np5(n+1)s22P3/2,1/2 states in Na (n=2), K (n=3), and Cs (n=5) atoms, strong negative-ion resonances dominate the electron-impact excitation of the lowest autoionizing states in Rb.

  13. Absorption and emission of single attosecond light pulses in an autoionizing gaseous medium dressed by a time-delayed control field

    OpenAIRE

    Chu, Wei-Chun; C. D. Lin

    2012-01-01

    An extreme ultraviolet (EUV) single attosecond pulse passing through a laser-dressed dense gas is studied theoretically. The weak EUV pulse pumps the helium gas from the ground state to the 2s2p(1P) autoionizing state, which is coupled to the 2s2(1S) autoionizing state by a femtosecond infrared laser with the intensity in the order of 10^{12} W/cm2. The simulation shows how the transient absorption and emission of the EUV are modified by the coupling laser. A simple analytical expression for ...

  14. Theoretical study of the 4p5nln′l′ autoionizing states of Rb excited by electron impact

    International Nuclear Information System (INIS)

    Large scale configuration interaction calculations of energy levels, autoionization probabilities and electron-impact excitation cross sections of the autoionizing states 4p5nln′l′ (nl = 5s,4d,5p,4f; n′l′ = 4d,5s,5p,5d,5f,5g,6s,6p,6d,7s,7p) of Rb up to 19.6 eV were performed for the first time. The relativistic effects were taken into account in the Dirac–Fock–Slater approximation. The asymmetry parameters of the angular distribution of Auger electrons for a number of electron-impact excited states were calculated in a single configuration intermediate coupling approximation. Strong dependence on the energy of exciting electrons was found for the angular distribution of the emitted Auger electrons from the states with J > 3/2 at the polar ‘magic angle’ of 54.73°. The calculated data were used for the novel classification of lines in an experimental ejected-electron spectrum. (paper)

  15. Electron-impact excitation of the (n - 1)d9 ns2np autoionizing states of cadmium (n = 5) and zinc (n = 4)

    International Nuclear Information System (INIS)

    Electron-impact excitation of the 53P1 (12.062 eV) and 51P1 (12.810 eV) 4d95s25p autoionizing states of Cd has been experimentally investigated at incident electron energies (E0) from 15 to 60 eV and scattering angles (θ) up to 40 deg. (at E0 = 40 eV, θ = 2 deg. -150 deg.). The absolute differential cross sections (DCSs) at E0 = 40 eV were determined through normalization to the optical oscillator strengths. These DCSs were extrapolated to 0 deg. and 180 deg. and numerically integrated to yield integral, momentum transfer and viscosity cross sections. Energy-loss spectra for Cd were recorded from 11 to 18 eV, and 22 autoionizing states were identified at different impact energies. Electron-impact excitation of the 3d94s24p autoionizing states was observed in energy-loss spectra of Zn at E0 = 20, 60, 80 and 100 eV (θ up to 10 deg.). The DCSs for Cd could not be compared with other results, because there are no available data in literature. The autoionizing energy levels and line widths are in good agreement with existing experimental and calculated values

  16. Two-step laser optogalvanic spectroscopy of high J momentum 4dnd and 4dng autoionizing states of strontium

    International Nuclear Information System (INIS)

    We have measured the energies of about two hundred even parity J=3-5 autoionizing 4 dnd and 4 dng Rydberg states of strontium (Sr) using an optogalvanic method. These states are reached by a two-step dye laser excitation from the 4d 5s metastables through the 4d 5p 3P2, 1F3, 3F4 intermediates. The 4d 5s are populated in a d.c. glow discharge through a Sr heated cell. The electronic configuration of the observed J=3, 4 states is deduced from the Lu-Fano plots of their quantum defect values and the spectral characteristics of the corresponding transitions. (orig.)

  17. Extracting partial decay rates of helium from complex rotation: autoionizing resonances of the one-dimensional configurations

    CERN Document Server

    Zimmermann, Klaus; Jörder, Felix; Heitz, Nicolai; Schmidt, Maximilian; Bouri, Celsus; Rodriguez, Alberto; Buchleitner, Andreas

    2014-01-01

    Partial autoionization rates of doubly excited one-dimensional helium in the collinear Zee and eZe configuration are obtained by means of the complex rotation method. The approach presented here relies on a projection of back-rotated resonance wave functions onto singly ionized $\\textrm{He}^{+}$ channel wave functions and the computation of the corresponding particle fluxes. In spite of the long-range nature of the Coulomb potential between the electrons and the nucleus, an asymptotic region where the fluxes are stationary is clearly observed. Low-lying doubly excited states are found to decay predomintantly into the nearest single-ionization continuum. This approach paves the way for a systematic analysis of the decay rates observed in higher-dimensional models, and of the role of electronic correlations and atomic structure in recent photoionization experiments.

  18. Zero-degree target electron spectroscopy: autoionizing resonances of helium excited by fast H+, He+ and He2+ impact

    International Nuclear Information System (INIS)

    Two-electron excitation and decay of the autoionizing (2p2)1D and (2s2p)1P states of helium in collisions with fast protons and helium ions have been studied using zero-degree target electron spectroscopy. The energy resolution of electron emission spectra is 80 meV. Experimental spectra were processed using a parametrization with allowance for the Coulomb interaction in the final state (CIFS) between the ejected electron, the scattered ion and the recoil helium ion. The Shore formula was applied as well. Calculations have been carried out with inclusion of CIFS in both direct and resonant ionization amplitudes and within an expansion of a two-electron excitation amplitude in powers of projectile-target interaction up to the second order. Influence of the three-body Coulomb interaction and effects of the charge and mass of the projectiles are studied. (author)

  19. The stereo-dynamics of collisional autoionization of ammonia by helium and neon metastable excited atoms through molecular beam experiments

    Energy Technology Data Exchange (ETDEWEB)

    Falcinelli, Stefano, E-mail: stefano.falcinelli@unipg.it; Vecchiocattivi, Franco [Department of Civil and Environmental Engineering, University of Perugia, Via G. Duranti 93, 06125 Perugia (Italy); Bartocci, Alessio; Cavalli, Simonetta; Pirani, Fernando [Department of Chemistry, Biology, and Biotechnology, University of Perugia, Via Elce di sotto 8, 06123 Perugia (Italy)

    2015-10-28

    A combined analysis of both new (energy spectra of emitted electrons) and previously published (ionization cross sections) experimental data, measured under the same conditions and concerning electronically excited lighter noble gas –NH{sub 3} collisional autoionization processes, is carried out. Such an analysis, performed by exploiting a formulation of the full potential energy surface both in the real and imaginary parts, provides direct information on energetics, structure, and lifetime of the intermediate collision complex over all the configuration space. The marked anisotropy in the attraction of the real part, driving the approach of reagents, and the selective role of the imaginary component, associated to the charge transfer coupling between entrance and exit channels, suggests that reactive events occur almost exclusively in the molecular hemisphere containing the nitrogen lone pair. Crucial details on the stereo-dynamics of elementary collisional autoionization processes are then obtained, in which the open shell nature of the disclosed ionic core of metastable atom plays a crucial role. The same analysis also suggests that the strength of the attraction and the anisotropy of the interaction increases regularly along the series Ne{sup *}({sup 3}P), He{sup *}({sup 3}S), He{sup *}({sup 1}S)–NH{sub 3}. These findings can be ascribed to the strong rise of the metastable atom electronic polarizability (deformability) along the series. The obtained results can stimulate state of the art ab initio calculations focused on specific features of the transition state (energetics, structure, lifetime, etc.) which can be crucial for a further improvement of the adopted treatment and to better understand the nature of the leading interaction components which are the same responsible for the formation of the intermolecular halogen and hydrogen bond.

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

    International Nuclear Information System (INIS)

    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 52,150–52,590 cm−1, through three different excitation pathways, originating from its ground state, 0 cm−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. -- Highlights: ► Three-colour photoionization optogalvanic spectroscopy of uranium was performed in a U–Ne hollow cathode discharge tube. ► Hollow cathode discharge tube was used as a source of atomic vapour and laser ionisation detector. ► Uranium photoionization spectra were investigated through three different three-colour photoionization schemes. ► Sixty new even-parity autoionization levels of uranium were identified. ► J-value of five autoionization levels was assigned uniquely

  1. Two-step excitation of an auto-ionized state of the Ba atom associated with two-photon excitation of an intermediate state

    International Nuclear Information System (INIS)

    An experimental and theoretical study is performed of the angular photoelectron distribution for three-photon ionization of Ba atoms through the 2ω-excited intermediate state 6p2(1S0) and the auto-ionized state 6p8s(3P1). Rotation of the polarization plane of dye-laser radiation allowed us to investigate the photoelectron angular distribution. Electrons were counted with the help of a time-of-flight electron spectrometer. The density-matrix formalism is used to obtain expressions for the angular dependence of the differential ionization probability. Possible experiments are discussed

  2. A study of the 4p-excited autoionization resonances in Sr by measurement of the angular correlation between the photoejected electrons and polarized fluorescent photons

    International Nuclear Information System (INIS)

    For five autoionization resonances of Sr in the 4p excitation region, we have determined the ratios of five amplitudes and one phase difference for the photo-ejected electron waves which leave the Sr+ ion in the 5p 2P1/2,3/2 excited states. The technique employed is a combination of conventional angle-resolved photoelectron spectroscopy, and angular correlation measurements between photoejected electrons and polarized fluorescent photons. We discuss how the ratios of the dipole amplitudes are related to the spectroscopic descriptions of the resonances studied. (author)

  3. Effects of autoionization in electron loss from helium-like highly charged ions in collisions with photons and fast atomic particles

    CERN Document Server

    Lyashchenko, K N; Voitkiv, A B

    2016-01-01

    We study theoretically single electron loss from helium-like highly charged ions involving excitation and decay of autoionizing states of the ion. Electron loss is caused by either photo absorption or the interaction with a fast atomic particle (a bare nucleus, a neutral atom, an electron). The interactions with the photon field and the fast particles are taken into account in the first order of perturbation theory. Two initial states of the ion are considered: $1s^2$ and $(1s2s)_{J=0}$. We analyze in detail how the shape of the emission pattern depends on the atomic number $Z_{I}$ of the ion discussing, in particular, the inter-relation between electron loss via photo absorption and due to the impact of atomic particles in collisions at modest relativistic and extreme relativistic energies. According to our results, in electron loss from the $1s^2$ state autoionization may substantially influence the shape of the emission spectra only up to $Z_{I} \\approx 35-40$. A much more prominent role is played by autoi...

  4. Giant autoionization resonance enhancement and term-dependence of photoionization time delay in half-filled subshell atoms: the Mn atom

    Science.gov (United States)

    Dolmatov, Valeriy; Kheifets, Anatoli; Manson, Steven; Deshmukh, Pranawa

    2015-05-01

    Time delay in photoelectron emission from atoms has become a hot topic of modern studies. To date, as far as we know, neither the significance of autoionization resonances in photoionization time delays has been established, nor features in time delays brought about by the configuration of open-shell atoms have been uncovered. To remedy the situation, we have studied the 3 d - and 4 s -photoionization time delays in the Mn(... 3d5 4s2 , 6 S) atom, which possesses a 3d5 half-filled subshell in its ground-state configuration, in the region of the well-known 3 p --> 3 d giant autoionization resonance (ℏω ~ 50 eV, γ ~ 2 eV). The dramatic impact of the resonance on 3 d - and 4 s -time delay is demonstrated and the physics behind it is unraveled. Strong term-dependence of the 4 s -time delay [Mn --> Mn+(4 s1 , 5 S) vs. Mn --> Mn+(4 s1 , 7 S) ] is discovered. The crucial importance of accounting for both the dominant 3 d --> f and the (generally) smaller 3 d --> p transitions in the calculation of the 3 d -photoinization time delay is established and explained. NSF grant No. PHY-1305085, DoE Grant No. DE-FG02-03ER15428, a grant from the Department of Science and Technology, Government of India.

  5. Measurements of oscillator strengths of the 2p{sup 5}({sup 2}P{sub 1/2})nd J = 2, 3 autoionizing resonances in neon

    Energy Technology Data Exchange (ETDEWEB)

    Mahmood, Shaukat; Amin, Nasir; Sami-ul-Haq; Shaikh, Nek M; Hussain, Shahid; Baig, M A [Atomic and Molecular Physics Laboratory, Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan)

    2006-05-14

    Oscillator strengths of the 2p{sup 5}({sup 2}P{sub 1/2})nd J = 2, 3 autoionizing resonances in neon have been determined using a dc discharge plasma in conjunction with an Nd:YAG pumped dye laser system. The excited states are approached using two-step laser excitation via 2p{sup 5}3p'[1/2]{sub 1}, 2p{sup 5}3p'[3/2]{sub 1} and 2p{sup 5}3p'[3/2]{sub 2} intermediate states which are accessed from the 2p{sup 5}3s [1/2]{sub 2} metastable state, populated by the discharge in the hollow cathode lamp. The f-values have been determined for the nd'[3/2]{sub 2}, nd'[5/2]{sub 2} and nd'[5/2]{sub 3} series following the {delta}K = {delta}J = +{delta}l selection rule. Employing the saturation technique the photoionization cross section at the 2p{sup 5} {sup 2}P{sub 1/2} ionization threshold is determined as 5.5(6) Mb and consequently the f-values of the nd' J = 2, 3 autoionizing resonances have been extracted.

  6. Efficient three-step, two-color ionization of plutonium using a resonance enhanced 2-photon transition into an autoionizing state

    Science.gov (United States)

    Kunz, P.; Huber, G.; Passler, G.; Trautmann, N.

    2004-05-01

    Resonance ionization mass spectrometry (RIMS) has proven to be a powerful method for isotope selective ultra-trace analysis of long-lived radioisotopes. For plutonium detection limits of 106 to 107 atoms have been achieved for various types of samples. So far a three-step, three-color laser excitation scheme was applied for efficient ionization. In this work, a two-photon transition from an excited state into a high-lying autoionizing state, will be presented, yielding a similar overall efficiency as the three-step, three-color ionization scheme. In this way, only two tunable lasers are needed, while the advantages of a three-step, three-color excitation (high selectivity, good efficiency and low non-resonant background) are preserved. The two-photon transition has been characterized with respect to saturation behavior and line width. The three-step, two-color ionization is a possibility for an improved RIMS procedure.

  7. Efficient three-step, two-color ionization of plutonium using a resonance enhanced 2-photon transition into an autoionizing state

    International Nuclear Information System (INIS)

    Resonance ionization mass spectrometry (RIMS) has proven to be a powerful method for isotope selective ultra-trace analysis of long-lived radioisotopes. For plutonium detection limits of to atoms have been achieved for various types of samples. So far a three-step, three-color laser excitation scheme was applied for efficient ionization. In this work, a two-photon transition from an excited state into a high-lying autoionizing state, will be presented, yielding a similar overall efficiency as the three-step, three-color ionization scheme. In this way, only two tunable lasers are needed, while the advantages of a three-step, three-color excitation (high selectivity, good efficiency and low non-resonant background) are preserved. The two-photon transition has been characterized with respect to saturation behavior and line width. The three-step, two-color ionization is a possibility for an improved RIMS procedure. (authors)

  8. Detection of the even parity, J=0-3, autoionizing 4 dnl Rydberg states of strontium by two-step laser optogalvanic spectroscopy

    International Nuclear Information System (INIS)

    We have measured the energies of a few hundreds of even parity, J=0-3 autoionizing 4 dnl Ry states of strontium using an optogalvanic spectroscopy technique. These states are reached by a two-step pulsed dye laser excitation from the 4d 5s metastables through the 4d 5p 3P0,1,2 intermediate states. Electronic collisions populate the 4d 5s states in a d.c. glow discharge through a Sr plus He vapour in a heated quartz cell. The electronic configuration for the majority of the observed Sr states is deduced from their quantum defect values and other characteristics of the corresponding transitions. (orig.)

  9. Relativistic multichannel treatment of autoionization Rydberg series of 4s2nf(n = 4 − 23) Jπ = (7/2)° for scandium

    International Nuclear Information System (INIS)

    Based on relativistic multichannel theory, this paper calculates the energy levels of autoionization Rydberg series 4s2nf(n = 4 − 23)Jπ = (7/2)° of scandium at different levels of approximation within the framework of multichannel quantum defect theory. The present results show that the dipole polarizations play an important role. Considering the dynamical dipole polarization effects, this paper finds that the difference between calculated and experimental quantum defects for the 4s2nf(n = 4 − 23)Jπ = (7/2)° series is generally about 0.01–0.03. Furthermore, the reason that 4s216f is obscured in experimental spectra is suggested to be the interaction with the neighbouring resonance state converged to 3d2(1G4)of Sc+

  10. Excitation energies, radiative and autoionization rates, dielectronic satellite lines and dielectronic recombination rates for excited states of Ag-like W from Pd-like W

    International Nuclear Information System (INIS)

    Energy levels, radiative transition probabilities and autoionization rates for [Kr]4d94fnl (n = 4-9), [Kr]4d95l'nl (n = 5-9) and [Kr]4d96l'nl (n = 6-7) states in Ag-like tungsten (W27+) are calculated using the relativistic many-body perturbation theory method, the multiconfiguration relativistic Hebrew University Lawrence Livermore Atomic Code and the Hartree-Fock-relativistic method. Branching ratios relative to the first threshold and intensity factors are calculated for satellite lines, and dielectronic recombination (DR) rate coefficients are determined for the singly excited [Kr]4d10nl (n = 4-9) states. The total DR rate coefficient is derived as a function of electron temperature. These atomic data are important in the modelling of N-shell radiation spectra of heavy ions generated in various collision as well as plasma experiments. The tungsten data are particularly important for fusion application.

  11. Time-dependent renormalized natural orbital theory applied to the two-electron spin-singlet case: ground state, linear response, and autoionization

    CERN Document Server

    Brics, M

    2013-01-01

    Favorably scaling numerical time-dependent many-electron techniques such as time-dependent density functional theory (TDDFT) with adiabatic exchange-correlation potentials typically fail in capturing highly correlated electron dynamics. We propose a method based on natural orbitals, i.e., the eigenfunctions of the one-body reduced density matrix, that is almost as inexpensive numerically as adiabatic TDDFT, but which is capable of describing correlated phenomena such as doubly excited states, autoionization, Fano profiles in the photoelectron spectra, and strong-field ionization in general. Equations of motion (EOM) for natural orbitals and their occupation numbers have been derived earlier. We show that by using renormalized natural orbitals (RNO) both can be combined into one equation governed by a hermitian effective Hamiltonian. We specialize on the two-electron spin-singlet system, known as being a "worst case" testing ground for TDDFT, and employ the widely used, numerically exactly solvable, one-dimens...

  12. Photoelectron angular distributions from autoionizing 4s14p66p1 states in atomic krypton probed with femtosecond time resolution

    International Nuclear Information System (INIS)

    Photoelectron angular distributions (PADs) are obtained for a pair of 4s14p66p1 (a singlet and a triplet) autoionizing states in atomic krypton. A high-order harmonic pulse is used to excite the pair of states and a time-delayed 801 nm ionization pulse probes the PADs to the final 4s14p6 continuum with femtosecond time resolution. The ejected electrons are detected with velocity map imaging to retrieve the time-resolved photoelectron spectrum and PADs. The PAD for the triplet state is inherently separable by virtue of its longer autoionization lifetime. Measuring the total signal over time allows for the PADs to be extracted for both the singlet state and the triplet state. Anisotropy parameters for the triplet state are measured to be β2= 0.55 ± 0.17 and β4=-0.01 ± 0.10, while the singlet state yields β2= 2.19 ± 0.18 and β4= 1.84 ± 0.14. For the singlet state, the ratio of radial transition dipole matrix elements, X, of outgoing S to D partial waves and total phase shift difference between these waves, Δ, are determined to be X= 0.56 ± 0.08 and Δ= 2.19 ± 0.11 rad. The continuum quantum defect difference between the S and D electron partial waves is determined to be -0.15 ± 0.03 for the singlet state. Based on previous analyses, the triplet state is expected to have anisotropy parameters independent of electron kinetic energy and equal to β2= 5/7 and β4=-12/7. Deviations from the predicted values are thought to be a result of state mixing by spin-orbit and configuration interactions in the intermediate and final states; theoretical calculations are required to quantify these effects.

  13. Excitation of the (2p2)1D and (2s2p)1P autoionizing states of helium by 200 eV electron impact

    International Nuclear Information System (INIS)

    We report full second Born calculations with inclusion of post-collision interactions for excitation of the (2p2)1D and (2s2p)1P autoionizing states of helium by 200 eV electron impact. The calculations are compared to (e, 2e) measurements of McDonald and Crowe (McDonald D G and Crowe A 1993 J. Phys. B: At. Mol. Opt. Phys. 26 2887-97) and Lower and Weigold (Lower J and Weigold E 1990 J. Phys. B: At. Mol. Opt. Phys. 23 2819-45). It is shown that post-collision interactions or Coulomb interactions in the final state between the scattered particle, the ejected electron and the recoil ion have a strong influence on both the direct ionization and resonance profiles around the binary lobe. The second-order terms in the amplitude of double electron excitation also play an observable role under these kinematic conditions. Reasonable agreement is found between the full-scale calculations and the experimental data. (author). Letter-to-the-editor

  14. Photoionization of cold gas phase coronene and its clusters: Autoionization resonances in monomer, dimer, and trimer and electronic structure of monomer cation

    International Nuclear Information System (INIS)

    Polycyclic aromatic hydrocarbons (PAHs) are key species encountered in a large variety of environments such as the Interstellar Medium (ISM) and in combustion media. Their UV spectroscopy and photodynamics in neutral and cationic forms are important to investigate in order to learn about their structure, formation mechanisms, and reactivity. Here, we report an experimental photoelectron-photoion coincidence study of a prototypical PAH molecule, coronene, and its small clusters, in a molecular beam using the vacuum ultraviolet (VUV) photons provided by the SOLEIL synchrotron facility. Mass-selected high resolution threshold photoelectron (TPES) and total ion yield spectra were obtained and analyzed in detail. Intense series of autoionizing resonances have been characterized as originating from the monomer, dimer, and trimer neutral species, which may be used as spectral fingerprints for their detection in the ISM by VUV absorption spectroscopy. Finally, a full description of the electronic structure of the monomer cation was made and discussed in detail in relation to previous spectroscopic optical absorption data. Tentative vibrational assignments in the near-threshold TPES spectrum of the monomer have been made with the support of a theoretical approach based on density functional theory

  15. Photoionization of cold gas phase coronene and its clusters: Autoionization resonances in monomer, dimer, and trimer and electronic structure of monomer cation

    Energy Technology Data Exchange (ETDEWEB)

    Bréchignac, Philippe, E-mail: philippe.brechignac@u-psud.fr; Falvo, Cyril; Parneix, Pascal; Pino, Thomas; Pirali, Olivier [Institut des Sciences Moléculaires d’Orsay, CNRS UMR8214, Univ Paris-Sud, F-91405 Orsay (France); Garcia, Gustavo A.; Nahon, Laurent [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, B.P. 48, F-91192 Gif-sur-Yvette (France); Joblin, Christine; Kokkin, Damian; Bonnamy, Anthony [IRAP, Université de Toulouse 3 - CNRS, 9 Av. Colonel Roche, B.P. 44346, F-31028 Toulouse Cedex 4 (France); Mulas, Giacomo [INAF - Osservatorio Astronomico di Cagliari, via della scienza 5, I-09047 Selargius (Italy)

    2014-10-28

    Polycyclic aromatic hydrocarbons (PAHs) are key species encountered in a large variety of environments such as the Interstellar Medium (ISM) and in combustion media. Their UV spectroscopy and photodynamics in neutral and cationic forms are important to investigate in order to learn about their structure, formation mechanisms, and reactivity. Here, we report an experimental photoelectron-photoion coincidence study of a prototypical PAH molecule, coronene, and its small clusters, in a molecular beam using the vacuum ultraviolet (VUV) photons provided by the SOLEIL synchrotron facility. Mass-selected high resolution threshold photoelectron (TPES) and total ion yield spectra were obtained and analyzed in detail. Intense series of autoionizing resonances have been characterized as originating from the monomer, dimer, and trimer neutral species, which may be used as spectral fingerprints for their detection in the ISM by VUV absorption spectroscopy. Finally, a full description of the electronic structure of the monomer cation was made and discussed in detail in relation to previous spectroscopic optical absorption data. Tentative vibrational assignments in the near-threshold TPES spectrum of the monomer have been made with the support of a theoretical approach based on density functional theory.

  16. Photoionization of cold gas phase coronene and its clusters: autoionization resonances in monomer, dimer, and trimer and electronic structure of monomer cation.

    Science.gov (United States)

    Bréchignac, Philippe; Garcia, Gustavo A; Falvo, Cyril; Joblin, Christine; Kokkin, Damian; Bonnamy, Anthony; Parneix, Pascal; Pino, Thomas; Pirali, Olivier; Mulas, Giacomo; Nahon, Laurent

    2014-10-28

    Polycyclic aromatic hydrocarbons (PAHs) are key species encountered in a large variety of environments such as the Interstellar Medium (ISM) and in combustion media. Their UV spectroscopy and photodynamics in neutral and cationic forms are important to investigate in order to learn about their structure, formation mechanisms, and reactivity. Here, we report an experimental photoelectron-photoion coincidence study of a prototypical PAH molecule, coronene, and its small clusters, in a molecular beam using the vacuum ultraviolet (VUV) photons provided by the SOLEIL synchrotron facility. Mass-selected high resolution threshold photoelectron (TPES) and total ion yield spectra were obtained and analyzed in detail. Intense series of autoionizing resonances have been characterized as originating from the monomer, dimer, and trimer neutral species, which may be used as spectral fingerprints for their detection in the ISM by VUV absorption spectroscopy. Finally, a full description of the electronic structure of the monomer cation was made and discussed in detail in relation to previous spectroscopic optical absorption data. Tentative vibrational assignments in the near-threshold TPES spectrum of the monomer have been made with the support of a theoretical approach based on density functional theory. PMID:25362317

  17. Chemiionization of the hydrogen molecule by He(2 3S) and He(2 1S) atoms: potential surfaces, autoionization widths, and cross sections

    International Nuclear Information System (INIS)

    Potential energy surfaces have been calculated for He(2 3S) and He(2 1S) atoms on H2 using the stabilization method. Energies have been obtained for several He*--H2 separations X and relative orientations theta of the H--H and He--H2 axes; the H--H distance was fixed at 1.4 a0. Aside from shallow van der Waals minima at large separations, cuts of both surfaces at fixed theta are repulsive. The adiabatic He*--H2 interactions are resonances lying in the HeH+2+e continuum at all points; hence chemiionization can occur in collisions. The autoionization width GAMMA as a function of nuclear coordinates has been calculated in two ways: (i) by Fermi's ''golden rule'' utilizing expansions in square-integrable functions to avoid having to directly evaluate integrals over continuum orbitals, and (ii) by a new, less rigorous technique based on observations about the convergence characteristics of the stabilization procedure. The widths are found to fall off exponentially with He*--H2 separation and to be only weakly dependent on the angular orientation. The scattering problem has been formulated in terms of the local complex potential V (X,theta)-1/2iGAMMA (X,theta) and total chemiionization cross sections have been calculated in the spherical potential and sudden approximations at energies below 10 eV. The two approximations yield very similar results. Ionization rate constants and the singlet-to-triplet cross section ratios are also presented. The cross sections and ratios exhibit a strong dependence on collision energy (or temperature), and it is shown that the well known disagreement between beam and afterglow experiments about these quantities may largely be a result of their different velocity distributions

  18. Three-step laser excitation of the 6p3/2ns, nd, ng autoionizing Rydberg levels via the 6p5f 1/2[5/2]2 level of lead

    Science.gov (United States)

    Ahad, A.; Nadeem, A.; Bhatti, S. A.; Baig, M. A.

    2005-03-01

    Odd parity autoionizing Rydberg levels of atomic lead in the energy region above the 6p1/2 ionization threshold have been investigated using three-step laser excitation in conjunction with an atomic beam apparatus. The 6p3/2ns (J = 1, 2), 6p3/2nd (J = 1, 2, 3) and 6p3/2ng (J = 2, 3) levels have been observed from the 6p5f 1/2[5/2]2 intermediate level. Energy values and FWHM of forty levels belonging to the 6p3/2ns, 6p3/2nd and 6p3/2ng configurations are presented. Six levels based on the 6p3/2ng (5, 13 ≤n ≤15) configurations and three levels attached to the 6p3/28d configuration are reported for the first time. The present study of the low-lying autoionizing levels attached to the 6p3/25g (J = 2, 3) configuration completes the series adjacent to the 6p1/2 limit.

  19. Ejected-electron excitation functions of the (4p55s2)2P3/2,1/2 autoionizing states of rubidium atoms excited by 15 to 640 eV electrons

    International Nuclear Information System (INIS)

    Ejected-electron excitation functions of the (4p55s2)2P3/2,1/2 leading autoionizing doublet in rubidium atoms were measured for the incident electron energy ranges from threshold up to 640 eV. The excitation functions show strong negative-ion resonances near threshold and broad maxima, typical for dipole-allowed transitions, around 100 eV. The excitation cross sections reach the maximum value of 1.1·10−17 cm2 at 15.9 eV and 0.3·10−17 cm2 at 16.9 eV for 2P3/2 and 2P1/2 states, respectively.

  20. Pump-probe photoelectron velocity-map imaging of autoionizing singly excited 4s14p6np1(n=7,8) and doubly excited 4s24p45s16p1 resonances in atomic krypton

    International Nuclear Information System (INIS)

    Pump-probe photoelectron velocity-map imaging, using 27-eV high-harmonic excitation and 786-nm ionization, is used to resolve overlapping autoionizing resonances in atomic krypton, obtaining two-photon photoelectron angular distributions (PADs) for singly and doubly excited states. Two features in the photoelectron spectrum are assigned to singly excited 4s14p6np1 (n = 7,8) configurations and four features provide information about double excitation configurations. The anisotropy parameters for the singly excited 7p configuration are measured to be β2 = 1.61 ± 0.06 and β4 = 1.54 ± 0.16 while the 8p configuration gives β2 = 1.23 ± 0.19 and β4 = 0.60 ± 0.15. These anisotropies most likely represent the sum of overlapping PADs from states of singlet and triplet spin multiplicities. Of the four bands corresponding to ionization of doubly excited states, two are assigned to 4s24p45s16p1 configurations that are probed to different J-split ion states. The two remaining doubly excited states are attributed to a previously observed, but unassigned, resonance in the vacuum-ultraviolet photoabsorption spectrum. The PADs from each of the double excitation states are also influenced by overlap from neighboring states that are not completely spectrally resolved. The anisotropies of the observed double excitation states are reported, anticipating future theoretical and experimental work to separate the overlapping PADs into the state resolved PADs. The results can be used to test theories of excited state ionization.

  1. XFEL resonant photo-pumping of dense plasmas and dynamic evolution of autoionizing core hole states

    Science.gov (United States)

    Rosmej, F. B.; Moinard, A.; Renner, O.; Galtier, E.; Lee, J. J.; Nagler, B.; Heimann, P. A.; Schlotter, W.; Turner, J. J.; Lee, R. W.; Makita, M.; Riley, D.; Seely, J.

    2016-03-01

    Similarly to the case of LIF (Laser-Induced Fluorescence), an equally revolutionary impact to science is expected from resonant X-ray photo-pumping. It will particularly contribute to a progress in high energy density science: pumped core hole states create X-ray transitions that can escape dense matter on a 10 fs-time scale without essential photoabsorption, thus providing a unique possibility to study matter under extreme conditions. In the first proof of principle experiment at the X-ray Free Electron Laser LCLS at SCLAC [Seely, J., Rosmej, F.B., Shepherd, R., Riley, D., Lee, R.W. Proposal to Perform the 1st High Energy Density Plasma Spectroscopic Pump/Probe Experiment”, approved LCLS proposal L332 (2010)] we have successfully pumped inner-shell X-ray transitions in dense plasmas. The plasma was generated with a YAG laser irradiating solid Al and Mg targets attached to a rotating cylinder. In parallel to the optical laser beam, the XFEL was focused into the plasma plume at different delay times and pump energies. Pumped X-ray transitions have been observed with a spherically bent crystal spectrometer coupled to a Princeton CCD. By using this experimental configuration, we have simultaneously achieved extremely high spectral (λ/δλ ≈ 5000) and spatial resolution (δx≈70 μm) while maintaining high luminosity and a large spectral range covered (6.90 - 8.35 Å). By precisely measuring the variations in spectra emitted from plasma under action of XFEL radiation, we have successfully demonstrated transient X- ray pumping in a dense plasma.

  2. Autoionization study of the Argon 2p satellites excited near the argon 2s threshold

    Energy Technology Data Exchange (ETDEWEB)

    Wang, H.; Glans, P.; Hemmers, O. [Univ. of Nevada, Las Vegas, NV (United States)] [and others

    1997-04-01

    The dynamics of near-threshold photoionization is a complex phenomenon in which the many-electron character of the wavefunctions plays an important role. According to generalized time-independent resonant scattering theory, the transition matrix element from an initial state to a final state is the summation of the amplitudes of direct photoionization and an indirect term in which intermediate states are involved and the resonant behavior is embedded. Studies of the interference effects of intermediate states have been explored in the cases where the direct term is negligible. In the present work, electron time-of-flight spectra of the Ar 2p satellites were measured at two angles (magic and 0{degrees}) in the dipole plane with the exciting photon energy tuned in the vicinity of the Ar 2s threshold. For excitation far below or above the 2s threshold, the 2p satellites spectrum is dominated by 3p to np shakeup contributions upon the ionization of a 2p electron.

  3. State-specific reactions and autoionization dynamics of Ar2+ produced by synchrotron radiation

    Czech Academy of Sciences Publication Activity Database

    Franceschi, P.; Thissen, R.; Dutuit, O.; Alcaraz, Ch.; Soldi-Lose, H.; Bassi, D.; Ascenzi, D.; Tosi, P.; Žabka, Ján; Herman, Zdeněk; Coreno, M.; De Simone, M.

    2009-01-01

    Roč. 280, 1-3 (2009), s. 119-127. ISSN 1387-3806 R&D Projects: GA AV ČR IAA400400702 Institutional research plan: CEZ:AV0Z40400503 Keywords : argon * dications * photoionization * ion molecule reaction Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.117, year: 2009

  4. Electronic Autoionization in Carbon monoxide: The effects of the Vibrational Motion.

    OpenAIRE

    Leyh, Bernard; Delwiche, Jacques; Hubin-Franskin, Marie-Jeanne; Nenner, I.

    1987-01-01

    New continuous measurements of the vibrationally resolved photoionization cross sections of CO+ X2Sigma+ and A2Pi between 63 and 83 nm are reported. We assign the Rydberg series converging to CO+ A2Pi. The effects of the vibrational motion are interpreted on the basis of the Condon approximation. This approximation is shown to allow a qualitative understanding of the decay of the Rydberg series converging to the A2Pi and B2Sigma+ states of CO+.

  5. First observation of a Fano profile following one step autoionization into a double photoionization continuum

    International Nuclear Information System (INIS)

    We have measured the double photoionization cross section of sodium atoms between the first 2s22p52P double photoionization (52.4 eV) and 2s-single 1.3S photoionization thresholds (71.0 eV). We have also observed a Fano profile into the double ionization continuum resulting from the interference between the one-step direct double photoionization process and the resonant double Auger decay of core-excited neutral sodium in the 2s → 3p resonance region. Profiles of absolute partial and total cross sections have been obtained in all important channels. The Fano and Starace parameters, in particular a width of 0.23 eV, have been determined, allowing full characterization of the resonance. (orig.)

  6. Grating Ti:Sa laser: Rydberg & auto-ionizing state spectroscopy

    Science.gov (United States)

    Teigelhoefer, Andrea; Bricault, Pierre; Lassen, Jens; Neu, Walter; Wendt, Klaus

    2009-05-01

    TRIUMF's Isotope Separator and Accelerator facility (ISAC) provides intense radioactive isotope beams (RIB) for nuclear and particle physics experiments. Resonant laser ionization is well suited as an on-line ion source for RIB production due to its efficiency and element selectivity. TRIUMF's Laser Ion Source (TRI LIS) uses BRF tuned Ti:Sa lasers with GHz linewidth and 10kHz rep. rate. Continuous wavelength scanning of these lasers is involved. A grating tuned Ti:Sa laser was built to allow for high resolution continuous wavelength scans (10nm/h) thus allowing for systematic studies of high lying atomic energy levels and the development of efficient RIS schemes. This grating tuned Ti:Sa laser system will be presented.

  7. Stereoselectivity in Autoionization Reactions of Hydrogenated Molecules by Metastable Noble Gas Atoms: The Role of Electronic Couplings.

    Science.gov (United States)

    Falcinelli, Stefano; Rosi, Marzio; Cavalli, Simonetta; Pirani, Fernando; Vecchiocattivi, Franco

    2016-08-22

    Focus in the present paper is on the analysis of total and partial ionization cross sections, measured in absolute value as a function of the collision energy, representative of the probability of ionic product formation in selected electronic states in Ne*-H2 O, H2 S, and NH3 collisions. In order to characterize the imaginary part of the optical potential, related to electronic couplings, we generalize a methodology to obtain direct information on the opacity function of these reactions. Such a methodology has been recently exploited to test the real part of the optical potential (S. Falcinelli et al., Chem. Eur. J., 2016, 22, 764-771). Depending on the balance of noncovalent contributions, the real part controls the approach of neutral reactants, the removal of ionic products, and the structure of the transition state. Strength, range, and stereoselectivity of electronic couplings, triggering these and many other reactions, are directly obtained from the present investigation. PMID:27470487

  8. Resonance-enhanced multiphoton ionization photoelectron spectroscopy of even-parity autoionizing Rydberg states of atomic sulphur

    OpenAIRE

    Woutersen, S.; Milan,, M; Lange; Buma, W.J.

    1997-01-01

    Several previously unobserved Rydberg states of the sulphur atom above the lowest ionization threshold are identified and assigned using (2 + 1) resonance-enhanced multiphoton-ionization photoelectron spectroscopy. All states were accessed by two-photon transitions from either the 3P ground or the 1D excited state, prepared by in situ photodissociation of H2S. The observed states derive from the (2Do)5p and (2Po)4p configurations. For the (2Do)5p 3F and (2Po)4p 3D triplets, extensive photoele...

  9. Theory and computation of the profile of the free-free transition probability between autoionizing (resonant) states

    International Nuclear Information System (INIS)

    We have derived the general expression for the energy-dependent cross section of the transition between two resonant states in the continuous spectrum of atoms and molecules, under the physically meaningful conditions of broadband excitation. The profile is expressed in terms of a symmetric, an asymmetric and a background component, and is cast in a form containing as limiting cases the discrete-discrete Lorentzian profile and the discrete-resonance Beutler-Fano profile. The theory has been implemented numerically by ab initio methods on the transition He** '2s2p' 1po → '2p3p' 1D, for tunable radiation hv around 3.4 eV. (Author)

  10. Complex-scaled equation-of-motion coupled-cluster method with single and double substitutions for autoionizing excited states: Theory, implementation, and examples

    International Nuclear Information System (INIS)

    Theory and implementation of complex-scaled variant of equation-of-motion coupled-cluster method for excitation energies with single and double substitutions (EOM-EE-CCSD) is presented. The complex-scaling formalism extends the EOM-EE-CCSD model to resonance states, i.e., excited states that are metastable with respect to electron ejection. The method is applied to Feshbach resonances in atomic systems (He, H−, and Be). The dependence of the results on one-electron basis set is quantified and analyzed. Energy decomposition and wave function analysis reveal that the origin of the dependence is in electron correlation, which is essential for the lifetime of Feshbach resonances. It is found that one-electron basis should be sufficiently flexible to describe radial and angular electron correlation in a balanced fashion and at different values of the scaling parameter, θ. Standard basis sets that are optimized for not-complex-scaled calculations (θ = 0) are not sufficiently flexible to describe the θ-dependence of the wave functions even when heavily augmented by additional sets.

  11. A Novel Observation of 'a Sharp Absorption Line' Using Much More Broad Laser Lights: Quantum Interference in the Autoionization Spectra of Sc

    International Nuclear Information System (INIS)

    The most accurate measurements in physical sciences will be precision spectroscopic experiments which are based on the usage of most narrow lines in cooperation with interference phenomena. We present a novel experimental observation of 'a sharp absorption resonance line' with much more broad laser lights. The mechanism of such a novel phenomenon will be elucidated and its implications will be discussed

  12. Liouville-space R-matrix-Floquet description of atomic radiative processes involving autoionizing states in the presence of intense electromagnetic fields.

    OpenAIRE

    Jacobs, V.L.; Burke, P. G.; Potvliege, R. M.

    2014-01-01

    A reduced-density-operator description is developed for coherent optical phenomena in many-electron atomic systems, utilizing a Liouville-space, multiple-mode Floquet–Fourier representation. The Liouville-space formulation provides a natural generalization of the ordinary Hilbert-space (Hamiltonian) R-matrix-Floquet method, which has been developed for multi-photon transitions and laser-assisted electron–atom collision processes. In these applications, the R-matrix-Floquet method has been dem...

  13. XUV emission from autoionizing hole states induced by intense XUV-FEL at intensities up to 10{sup 17} W/cm{sup 2}

    Energy Technology Data Exchange (ETDEWEB)

    Rosmej, F B; Galtier, E [Universite Pierre et Marie Curie UPMC, UMR 7605, LULI, case 128, 4 Place Jussieu, 75252 Paris Cedex 05 (France); Riley, D; Dzelzainis, T [School of Mathematics and Physics, Queen' s University, Belfast BT7 1NN (United Kingdom); Heinmann, P; Lee, R W; Nelson, A; Vinko, S M; Whitcher, T [Lawrence Livermore National Laboratory (United States); Khattak, F Y [Department of Physics, Kohat University, Kohat, NWFP (Pakistan); Nagler, B; Wark, J S [Clarendon Laboratory, University of Oxford, South Parks Road OX1 3PU (United Kingdom); Tschentscher, T; Toleikis, S; Faeustlin, R [HASYLAB DESY, Hamburg (Germany); Soberierski, R [Institute of Physics, Polish Academy of Sciences (Poland); Juha, L; Chalupsky, J; Hajkova, V [Institute of Physics, AS CR, Prague 8 (Czech Republic); Fajardo, M, E-mail: frank.rosmej@upmc.f [Instituto Superior Tecnico, U. Tecnica de Lisboa (Portugal)

    2010-08-01

    Aluminium targets were irradiated with 92 eV radiation from FLASH Free Electron Laser at DESY at intensities up to 10{sup 17} W/cm{sup 2} by focussing the beam on target down to a spot size of {approx}1 {mu}m by means of a parabolic mirror. High resolution XUV spectroscopy was used to identify aluminium emission from complex hole-states. Simulations carried out with the MARIA code show that the emission characterizes the electron heating in the transition phase solid-atomic. The analysis allows constructing a simple model of electron heating via Auger electrons.

  14. Stereodynamics in the Collisional Autoionization of Water, Ammonia, and Hydrogen Sulfide with Metastable Rare Gas Atoms: Competition Between Intermolecular Halogen and Hydrogen Bonds.

    Science.gov (United States)

    Falcinelli, Stefano; Bartocci, Alessio; Cavalli, Simonetta; Pirani, Fernando; Vecchiocattivi, Franco

    2016-01-11

    Recent experiments on the title subject, performed with a high-resolution crossed-beam apparatus, have provided the total ionization cross sections as a function of the collision energy between noble gas atoms, electronically excited in their metastable states (Ng*), and H2 O, H2 S, and NH3 reagents, as well as the emitted electron energy spectra. This paper presents a rationalization of all the experimental findings in a unifying picture to cast light on the basic chemical properties of Ng* under conditions of great relevance both from a fundamental and from an applied point of view. The importance of this investigation is that it isolates the selective role of the intermolecular halogen and hydrogen bonds, to assess their anisotropic effects on the stereodynamics of the promoted ionization reactions, and to model energy transfer and reactivity in systems of applied interest, such as planetary atmospheres, plasmas, lasers, and flames. PMID:26633846

  15. The role of autoionizing states in electron-impact excitation of the lambda 230.6 nm intercombination line of an indium ion

    International Nuclear Information System (INIS)

    The electronic excitation function of the intercombination line lambda 230.6 nm an In+ ion is first investigated by the spectroscopic method in the energy range from the threshold to 00 eV using ion and electron beams crossing at the right angle. It is determined that, in the energy region of the spin-orbit splitting of excited levels, the dominant contribution to the resonance excitation is made by the Coster-Kronig process. It is discovered that, at the electron energies higher than the fivefold threshold, a decrease of the excitation function does not correspond to the law E-3 characteristic of intercombination transitions

  16. Different Complexation Behavior of P-Functionalized Ferrocene Derivatives Towards SnCl2 , SnCl4 and SnPh2 Cl2 : Auto-ionization and Redox-Type Reactions.

    Science.gov (United States)

    Gawron, Matthias; Dietz, Christina; Lutter, Michael; Duthie, Andrew; Jouikov, Viatcheslav; Jurkschat, Klaus

    2015-11-01

    The novel phosphonyl-substituted ferrocene derivatives [Fe(η(5) -Cp)(η(5) -C5 H3 {P(O)(O-iPr)2 }2 -1,2)] (Fc(1,2) ) and [Fe{η(5) -C5 H4 P(O)(O-iPr)2 }2 ] (Fc(1,1') ) react with SnCl2 , SnCl4 , and SnPh2 Cl2 , giving the corresponding complexes [(Fc(1,2) )2 SnCl][SnCl3 ] (1), [{(Fc(1,1') )SnCl2 }n ] (2), [(Fc(1,1') )SnCl4 ] (3), [{(Fc(1,1') )SnPh2 Cl2 }n ] (4), and [(Fc(1,2) )SnCl4 ] (5), respectively. The compounds are characterized by elemental analyses, (1) H, (13) C, (31) P, (119) Sn NMR and IR spectroscopy, (31) P and (119) Sn CP-MAS NMR spectroscopy, cyclovoltammetry, electrospray ionization mass spectrometry, and single-crystal as well as powder X-ray diffraction analyses. The experimental work is accompanied by DFT calculations, which help to shed light on the origin for the different reaction behavior of Fc(1,1') and Fc(1,2) towards tin(II) chloride. PMID:26480839

  17. Post-Collision Interaction with Wannier electrons

    CERN Document Server

    Kuchiev, M Yu

    1997-01-01

    A theory of the Post-Collision Interaction (PCI) is developed for the case when an electron atom impact results in creation of two low-energy Wannier electrons and an ion excited into an autoionizing state. The following autoionization decay exposes the Wannier pair to the influence of PCI resulting in variation of the shape of the line in the autoionization spectrum. An explicit dependence of the autoionization profile on the wave function of the Wannier pair is found. PCI provides an opportunity to study this wave function for a wide area of distances

  18. Workshop report of problems relating to multi-electron excited ions in plasma

    International Nuclear Information System (INIS)

    A workshop was held to discuss the problems relating to multiple electron-excited ions in plasma. The first part of this report deals with the problems of satellite lines. The satellite lines from laser plasma and vacuum sparks are discussed. Review papers on satellite lines and bielectronic recombination are also presented. The second part of this report deals with the problems of autoionization. Theory, comment on the compound state, observation of autoionization and resonance scattering, excitation cross-section, inner shell ionization, excitation through autoionization, and the bielectronic recombination of helium-like ions are discussed. (Kato, T.)

  19. Spectroscopy and multichannel quantum-defect theory analysis of the np Rydberg series of H3

    International Nuclear Information System (INIS)

    The lowest np Rydberg series of triatomic hydrogen has been studied using optical-optical double-resonance excitation from the metastable 2p2A2'' level. Bound states, detected by field ionization as well as autoionizing states of the p series are characterized using rotational multichannel quantum-defect theory. Deviations from the calculations appear when vibrational interactions give rise to predissociation below threshold or autoionizing interlopers above threshold. The np Rydberg manifold of H3 provides an almost complete panorama of channel interactions in a polyatomic molecule: rotational and vibrational interactions and autoionization with rich Fano profile structure as well as predissociation

  20. Rydberg atom ionization by slow collisions with alkali element atoms

    International Nuclear Information System (INIS)

    A new mechanism for ionization of highexcited atoms due to the electron capture into the autoionization state of a negative ion is suggested. Calculations of cross-sections and the ionization rate for sodium and lithium atoms collisions are performed

  1. Ultrafast Relaxation Dynamics of Highly-excited States in N2 Molecules Excited by Femtosecond XUV Pulses

    Directory of Open Access Journals (Sweden)

    Vrakking Marc J.J.

    2013-03-01

    Full Text Available We used velocity-map-imaging to measure electronic and nuclear dynamics in N2 molecules excited by a train of attosecond pulses. A time-to-space mapping of autoionization channel is demonstrated. It is found that the autoionization becomes energetically allowed when the two nuclei are still very close (~ 3 Å and that it can be coherently manipulated by a strong femtosecond infrared pulse.

  2. Three-step resonant photoionization spectroscopy of Ni and Ge: ionization potential and odd-parity Rydberg levels

    Science.gov (United States)

    Kessler, T.; Brück, K.; Baktash, C.; Beene, J. R.; Geppert, Ch; Havener, C. C.; Krause, H. F.; Liu, Y.; Schultz, D. R.; Stracener, D. W.; Vane, C. R.; Wendt, K.

    2007-12-01

    In preparation of a laser ion source, we have investigated multi-step laser ionization via Rydberg and autoionizing states for atomic Ni and Ge using a mass separator with an ion beam energy of 20 keV. For both elements resonant three-step excitation schemes suitable for modern Ti:sapphire laser systems were developed. Rydberg series in the range of principal quantum numbers 20 Ionization potentials (IP) were extracted from fits of the individual series and quantum defects of individual levels were analysed for confirmation of series assignment. For Ni the ionization potential could be extracted with significantly increased precision compared to literature with a value of EIP (Ni) = 61 619.77(14) cm-1. Also, at least one notable autoionizing state above the first IP was discovered for both elements, and the different ionization schemes via Rydberg or autoionizing states were compared with respect to line shape, ionization efficiency and selectivity.

  3. Contribution of high-nl shells to electron-impact ionization processes

    CERN Document Server

    Jonauskas, V; Merkelis, G; Gaigalas, G; Kisielius, R; Kučas, S; Masys, Š; Radžiūtė, L; Rynkun, P

    2015-01-01

    The contribution to electron-impact ionization cross sections from excitations to high-nl shells and a consequent autoionization is investigated. We perform relativistic subconfiguration-average and detailed level-to-level calculations for this process. Ionization cross sections for the W27+ ion are presented to illustrate the large influence of the high shells (n >= 9) and orbitals (l >= 4) in the excitation-autoionization process. The obtained results show that the excitations to the high shells (n >= 9) increase cross sections of the indirect ionization process by a factor of 2 compared to the excitations to the lower shells (n <= 8). The excitations to the shells with orbital quantum number l = 4 give the largest contribution comparedwith the other orbital quantum numbers l. Radiative damping reduces the cross sections of the indirect process approximately twofold in the case of the level-to-level calculations. Determined data show that the excitation-autoionization process contributes approximately 40...

  4. Spectral phase measurement of a Fano resonance using tunable attosecond pulses

    Science.gov (United States)

    Kotur, M.; Guénot, D.; Jiménez-Galán, Á.; Kroon, D.; Larsen, E. W.; Louisy, M.; Bengtsson, S.; Miranda, M.; Mauritsson, J.; Arnold, C. L.; Canton, S. E.; Gisselbrecht, M.; Carette, T.; Dahlström, J. M.; Lindroth, E.; Maquet, A.; Argenti, L.; Martín, F.; L'Huillier, A.

    2016-02-01

    Electron dynamics induced by resonant absorption of light is of fundamental importance in nature and has been the subject of countless studies in many scientific areas. Above the ionization threshold of atomic or molecular systems, the presence of discrete states leads to autoionization, which is an interference between two quantum paths: direct ionization and excitation of the discrete state coupled to the continuum. Traditionally studied with synchrotron radiation, the probability for autoionization exhibits a universal Fano intensity profile as a function of excitation energy. However, without additional phase information, the full temporal dynamics cannot be recovered. Here we use tunable attosecond pulses combined with weak infrared radiation in an interferometric setup to measure not only the intensity but also the phase variation of the photoionization amplitude across an autoionization resonance in argon. The phase variation can be used as a fingerprint of the interactions between the discrete state and the ionization continua, indicating a new route towards monitoring electron correlations in time.

  5. Circular Dichrosim in Photoionization of H2 and D2

    International Nuclear Information System (INIS)

    In this work, circular dichroism in H2 (D2) photoionization is studied in detail. We have selected several photon energies for a case study: 19 eV for which only direct ionization to the 1sσg ionization channel is present, 27 eV where autoionization of Q11Σ+u doubly excited states takes place, and 32.5 eV for which autoionization from Q1 and doubly excited states and direct ionization to 1sσg and 2pσu channels strongly interfere. The latter case shows clear evidence of different behavior of the photoionization against radiation helicity.

  6. Communication: Formation of slow electrons in the Auger decay of core-ionized water molecules

    Science.gov (United States)

    Hikosaka, Y.; Yamamoto, K.; Nakano, M.; Odagiri, T.; Soejima, K.; Suzuki, I. H.; Lablanquie, P.; Penent, F.; Ito, K.

    2012-11-01

    Double Auger decay of O1s-1 and its satellite states in H2O has been studied with a multi-electron coincidence method, and a process leading to autoionizing O* fragments has been revealed. The breaking of the two O-H bonds producing the autoionizing O* fragments occurs for highly excited H2O2+ populated by the initial Auger decay. The O* fragments are more favorably produced in the decay from the satellite states, resulting from the larger population of highly excited H2O2+ states inheriting the valence excitation in the initial state.

  7. Electron scattering on molecular hydrogen

    International Nuclear Information System (INIS)

    The author considers scattering phenomena which occur when a beam of electrons interacts with a molecular hydrogen gas of low density. Depending on the energy loss of the scattered electrons one can distinguish elastic scattering, excitation and (auto)ionization of the H2-molecule. The latter processes may also lead to dissociation. These processes are investigated in four experiments in increasing detail. (Auth.)

  8. Many-body processes in atomic and molecular physics. Progress report, September 1, 1983-August 31, 1984

    International Nuclear Information System (INIS)

    Research is reported on: semiclassical many mode Floquet theory; exact semiclassical treatment of nonlinear multiphoton dissociation; nonadiabatic approach for resonant infrared multiphoton absorption spectroscopy; infrared MPD of triatomic molecules, most probable path approach; and complex-coordinate coupled-Landau-channel method for autoionizing resonances of H atoms in intense magnetic fields

  9. Interactions between electrons in the field of a positive ion

    International Nuclear Information System (INIS)

    Recent studies on the (auto)ionization of atoms by means of electron-atom collisions reveal the existence of phenomena probably brought about by post-collision interactions in the vicinity of a positive ion. In this article, a review of the subject is given in relation to the research program of the Utrecht atomic physics group

  10. Detuning effect in multistep photo-ionization of atomic isotope of heavy element

    International Nuclear Information System (INIS)

    Detuning effect on the excitation wavelength in 3-step photoionization of atomic isotope of heavy element was experimentally obtained and the role of the isotope shift and hyperfine structure in each transition level was discussed. To achieve high selectivity, the combination of the HFS and isotope sift of upper and lower energy level including the autoionizing level was important. (author)

  11. Calculations for electron-impact ionization of beryllium in the method of interacting configurations in the complex number representation

    CERN Document Server

    Simulik, V M; Tymchyk, R V

    2016-01-01

    The beginning of the application of the method of interacting configurations in the complex number representation to the compound atomic systems has been presented. The spectroscopic characteristics of the Be atom in the problem of the electron-impact ionization of this atom are investigated. The energies and the widths of the lowest autoionizing states of Be atom are calculated.

  12. Electron impact ionization of multicharged ions

    International Nuclear Information System (INIS)

    Cross sections were measured with a crossed-beams apparatus. Results for e- + N4+ → N5+ + 2e- and e- + O4+ → O5+ + 2e- are shown from 100 to 2000 eV. The contribution of excitation-autoionization is noted. 2 figures

  13. Metastable states of highly excited heavy ions

    Science.gov (United States)

    Pegg, D. J.; Griffin, P. M.; Sellin, I. A.; Smith, W. W.; Donnally, B.

    1973-01-01

    Description of the method used and results obtained in an experimental study of the metastable states of highly stripped heavy ions, aimed at determining the lifetimes of such states by the rates of autoionization and radiation. The significance and limitations of the results presented are discussed.

  14. The 4p6 electron energy-loss spectrum of Rb atoms

    International Nuclear Information System (INIS)

    The scattered electron energy-loss spectrum due to the excitation of the 4p5n1l1n2l2 states in rubidium atoms was measured at 25.6 eV impact energy. New optically forbidden non-autoionizing states located between 16.5 and 16.8 eV were observed.

  15. Dynamics of single and multiphoton ionization processes in molecules

    International Nuclear Information System (INIS)

    Single-photon and resonant multiphoton ionization studies, which can now be carried out using synchrotron radiation and lasers, respectively, are providing important dynamical information on molecular photoionization. The author studied the underlying dynamical features of these ionization processes using Hartree-Fock continuum orbitals generated using the iterative Schwinger variational method for solving the photoelecttron collisional equations. The single-photon studies examine the important role that shape and autoionizing resonances play in molecular photoionization, while the multiphoton studies investigate the ionization dynamics of exited electronic states. The subtle nature of shape resonances was demonstrated in polyatomic systems such as C2H2 and C2N2, where the possibility of multiple resonances in a single channel is observed. Molecular autoionizing resonances are known to dominate regions of the photoionization spectra. The author adapted and applied a generalization of the Fano treatment for autoionization to molecular systems. Results for H2 and C2H2 autoionizing resonances are presented and discussed

  16. Strong enhancement of Penning ionization for asymmetric atom pairs in cold Rydberg gases: the Tom and Jerry effect

    Science.gov (United States)

    Efimov, D. K.; Miculis, K.; Bezuglov, N. N.; Ekers, A.

    2016-06-01

    We consider Penning ionization of Rydberg atom pairs as an Auger-type process induced by the dipole–dipole interaction and employ semiclassical formulae for dipole transitions to calculate the autoionization width as a function of the principal quantum numbers, n d , n i , of both atoms. While for symmetric atom pairs with {n}d={n}i={n}0 the well-known increase of the autoionization width with increasing n 0 is obtained, the result for asymmetric pairs is counterintuitive—for a fixed n i of the ionizing atom of the pair, the autoionization width strongly increases with decreasing n d of the de-excited atom. For H Rydberg atoms this increase reaches two orders of magnitude at the maximum of the n d dependence, and the same type of counterintuitive behavior is exhibited also by Na, Rb and Cs atoms. This is a purely quantum-mechanical effect, which points towards existence of optimal (we call them ‘Tom’ and ‘Jerry’ for ‘big’ and ‘small’) pairs of Rydberg atoms with respect to autoionization efficiency. Building on the model of population redistribution in cold Rydberg gases proposed in [1], we demonstrate that population evolution following the initial laser excitation of Rydberg atoms in state n 0 would eventually lead to the formation of such Tom–Jerry pairs with {n}i\\gt {n}0\\gt {n}d which feature autoionization widths that are enhanced by several orders of magnitude compared to that of two atoms in the initial laser-excited state n 0. We also show that in the high-density regime of cold Rydberg gas experiments the ionization rate of Tom–Jerry pairs can be substantially larger than the blackbody radiation-induced photoionization rate.

  17. Gamma radiation and temperature influence on the chemical effect produced by isomeric transition in the telluric acid

    International Nuclear Information System (INIS)

    When the gamma radiation due to the isomeric transition is internally converted an autoionization is produced. For atoms with a high atomic number this autoionization can be a large one and produce a fragmentation in a molecule. In the specific case of the solid state these fragments remain trapped in different places of the crystalline system. This can be considered as chemical change in the original molecule. These damages produced by the nuclear transformation can be measured by different methods: heating, gamma rays, pressure, etc. In this work the results of an experimental measurement of the behavior of the crystalline telluric acid molecule fragments under gamma radiation (0 to 20 Mrads) with controlled temperature of 20C (-1960C to 500C) it is presented. It was observed that the values of the mentioned behavior vary rapidly at first for relatively low doses and that for larger doses these values remained constant. Besides with a lower temperature these variation are progressively lower. (author)

  18. Multichannel Quantum Defect Study of the Perturber's Effect on the Overlapping Resonances in Rydberg Series for the Systems Involving 2 Closed and Many Open Channels

    International Nuclear Information System (INIS)

    The phase-shifted version of the multichannel quantum-defect theory (MQDT) was reformulated by disentangling the interloper spectrum from the perturbed dense Rydberg series for a systems involving 2 closed and more than 1 open channel. The theory was applied successfully to Martins and Zimmermann's photoionization spectra of the Rydberg series Cu I 3d9 4s(1D2) nd 2G9/2 perturbed by the interloper, 3d9 4p24F9/2, for which Cohen's 4 channel QDT had failed. The zero surface graphic of the perturbed Fano's asymmetry parameter q of the autoionization spectrum of dense Rydberg series by the interloper was determined by only two parameters for this system. It was used as a map to trace the transformation route of the 3 channel autoionization spectra to the 4 channel spectra when the channel coupling of the closed channels with a newly added open channel was turned on progressively

  19. Study on the AMO data production and evaluation techniques

    International Nuclear Information System (INIS)

    AMODS (Atomic, Molecular, and Optical Database System) which can be accessed with the URL http://amods.kaeri.re.kr consists of a computer system which is an Alpha workstation 600 with UNIX O/S and the APACHE 1.2 WWW server installed on an independently mounted file system of 4.3 GB. Currently the data in AMODS is mostly atom-related and consists of atomic spectral lines, atomic transition probabilities, atomic energy levels, atomic transition lines, and CODATA 86 as well as several reference data. Meanwhile spectroscopic parameter of Sm which is one of the rare earth elements, has been measured, resulting in production of 36 isotope shift data of the high-lying even parity states, followed by the measurement of autoionization states. New 31 autoionization states are found and energy levels of them are measured. The Fano's q parameters are determined through the theoretical analysis of the experimental data. (author). 11 refs., 3 tabs., 15 figs

  20. Resonant three-photon ionization spectroscopy of atomic Fe

    Science.gov (United States)

    Liu, Y.; Gottwald, T.; Havener, C. C.; Mattolat, C.; Vane, C. R.; Wendt, K.

    2013-12-01

    Laser spectroscopic investigations on high-lying states around the ionization potential (IP) in the atomic spectrum of Fe have been carried out for the development of a practical three-step resonance ionization scheme accessible by Ti: sapphire lasers. A hot cavity laser ion source, typically used at on-line radioactive ion beam production facilities, was employed in this work. Ionization schemes employing high-lying Rydberg and autoionizing states populated by three-photon excitations were established. Five new Rydberg and autoionizing Rydberg series converging to the ground and to the first four excited states of Fe II are reported. Analyses of the Rydberg series yield the value 63 737.686 ± 0.068 cm-1 for the ionization potential of iron.

  1. Resonant three-photon ionization spectroscopy of atomic Fe

    International Nuclear Information System (INIS)

    Laser spectroscopic investigations on high-lying states around the ionization potential (IP) in the atomic spectrum of Fe have been carried out for the development of a practical three-step resonance ionization scheme accessible by Ti: sapphire lasers. A hot cavity laser ion source, typically used at on-line radioactive ion beam production facilities, was employed in this work. Ionization schemes employing high-lying Rydberg and autoionizing states populated by three-photon excitations were established. Five new Rydberg and autoionizing Rydberg series converging to the ground and to the first four excited states of Fe II are reported. Analyses of the Rydberg series yield the value 63 737.686 ± 0.068 cm−1 for the ionization potential of iron. (paper)

  2. Resonant three-Photon Ionization Spectroscopy of Atomic Fe

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yuan [ORNL; Gottwald, T. [Johannes Gutenberg-Universitaet Mainz, Mainz, Germany; Havener, Charles C [ORNL; Mattolat, C. [Johannes Gutenberg-Universitaet Mainz, Mainz, Germany; Vane, C Randy [ORNL; Wendt, K. [Johannes Gutenberg-Universitaet Mainz, Mainz, Germany

    2013-01-01

    Laser spectroscopic investigations on high-lying states around the ionization potential in the atomic spectrum of Fe have been carried out for development of a practical three-step resonance ionization scheme accessible by Ti:Sapphire lasers. A hot cavity laser ion source typically used at on-line radioactive ion beam production facilities was employed in this work. Ionization schemes employing high-lying Rydberg and autoionizing states populated by three-photon excitations were established. Five new Rydberg and autoionizing Rydberg series converging to the ground and to the first four excited states of Fe II are reported. Analyses of the Rydberg series yield the value 63737.686 0.068 cm-1 for the ionization potential of iron.

  3. Young-type experiment using a single-electron source and an independent atomic-size two-center interferometer.

    Science.gov (United States)

    Chesnel, J-Y; Hajaji, A; Barrachina, R O; Frémont, F

    2007-03-01

    Evidence is given for Young-type interferences caused by a single electron acting on a given double-center scatterer analogous to an atomic-size double-slit system. The electron is provided by autoionization of a doubly excited He atom following the capture of the electrons of H2 by a He2+ incoming ion. The autoionizing projectile is a single-electron source, independent of the interferometer provided by the two H+ centers of the fully ionized H2 molecule. This experiment resembles the famous thought experiment imagined by Feynman in 1963, in which the quantum nature of the electron is illustrated from a Young-like double-slit experiment. Well-defined oscillations are visible in the angular distribution of the scattered electrons, showing that each electron interferes with itself. PMID:17358516

  4. In-source laser spectroscopy developments at TRILIS—towards spectroscopy on actinium and scandium

    International Nuclear Information System (INIS)

    Resonance Ionization Laser Ion Sources (RILIS) have become a versatile tool for production and study of exotic nuclides at Isotope Separator On-Line (ISOL) facilities such as ISAC at TRIUMF. The recent development and addition of a grating tuned spectroscopy laser to the TRIUMF RILIS solid state laser system allows for wide range spectral scans to investigate atomic structures on short lived isotopes, e.g., those from the element actinium, produced in uranium targets at ISAC. In addition, development of new and improved laser ionization schemes for rare isotope production at ISAC is ongoing. Here spectroscopic studies on bound states, Rydberg states and autoionizing (AI) resonances on scandium using the existing off-line capabilities are reported. These results allowed to identify a suitable ionization scheme for scandium via excitation into an autoionizing state at 58,104 cm − 1 which has subsequently been used for ionization of on-line produced exotic scandium isotopes.

  5. Direct Imaging of Transient Fano Resonances in N2 Using Time-, Energy-, and Angular-Resolved Photoelectron Spectroscopy

    Science.gov (United States)

    Eckstein, Martin; Yang, Chung-Hsin; Frassetto, Fabio; Poletto, Luca; Sansone, Giuseppe; Vrakking, Marc J. J.; Kornilov, Oleg

    2016-04-01

    Autoionizing Rydberg states of molecular N2 are studied using time-, energy-, and angular-resolved photoelectron spectroscopy. A femtosecond extreme ultraviolet pulse with a photon energy of 17.5 eV excites the resonance and a subsequent IR pulse ionizes the molecule before the autoionization takes place. The angular-resolved photoelectron spectra depend on pump-probe time delay and allow for the distinguishing of two electronic states contributing to the resonance. The lifetime of one of the contributions is determined to be 14 ±1 fs , while the lifetime of the other appears to be significantly shorter than the time resolution of the experiment. These observations suggest that the Rydberg states in this energy region are influenced by the effect of interference stabilization and merge into a complex resonance.

  6. Direct Imaging of Transient Fano Resonances in N_{2} Using Time-, Energy-, and Angular-Resolved Photoelectron Spectroscopy.

    Science.gov (United States)

    Eckstein, Martin; Yang, Chung-Hsin; Frassetto, Fabio; Poletto, Luca; Sansone, Giuseppe; Vrakking, Marc J J; Kornilov, Oleg

    2016-04-22

    Autoionizing Rydberg states of molecular N_{2} are studied using time-, energy-, and angular-resolved photoelectron spectroscopy. A femtosecond extreme ultraviolet pulse with a photon energy of 17.5 eV excites the resonance and a subsequent IR pulse ionizes the molecule before the autoionization takes place. The angular-resolved photoelectron spectra depend on pump-probe time delay and allow for the distinguishing of two electronic states contributing to the resonance. The lifetime of one of the contributions is determined to be 14±1  fs, while the lifetime of the other appears to be significantly shorter than the time resolution of the experiment. These observations suggest that the Rydberg states in this energy region are influenced by the effect of interference stabilization and merge into a complex resonance. PMID:27152799

  7. A fully relativistic approach for calculating atomic data for highly charged ions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hong Lin [Los Alamos National Laboratory; Fontes, Christopher J [Los Alamos National Laboratory; Sampson, Douglas H [PENNSYLVANIA STATE UNIV

    2009-01-01

    We present a review of our fully relativistic approach to calculating atomic data for highly charged ions, highlighting a research effort that spans twenty years. Detailed discussions of both theoretical and numerical techniques are provided. Our basic approach is expected to provide accurate results for ions that range from approximately half ionized to fully stripped. Options for improving the accuracy and range of validity of this approach are also discussed. In developing numerical methods for calculating data within this framework, considerable emphasis is placed on techniques that are robust and efficient. A variety of fundamental processes are considered including: photoexcitation, electron-impact excitation, electron-impact ionization, autoionization, electron capture, photoionization and photorecombination. Resonance contributions to a variety of these processes are also considered, including discussions of autoionization, electron capture and dielectronic recombination. Ample numerical examples are provided in order to illustrate the approach and to demonstrate its usefulness in providing data for large-scale plasma modeling.

  8. Resonances at excitation of the 61S0 - 63P1 intercombination transition of thallium ion in electron-ion collisions

    International Nuclear Information System (INIS)

    Excitation of resonance intercombination Tl2 line lambda=190.8 nm is studied for the first time in intercrossing electron and ion beams. Resonance structure conditioned by the contribution of autoionization states of thallium atom into the population of the 63P1 level of thallium ion. A complicated energy behaviour of excitation cross section of thallium ion intercombination transition reflects mechanisms conditioned by the influence of relativistic and resonance effects in external shells under the conditions of concurrence of several processes: direct transition of electron from the ground state into excited one with spin change , population of levels through autoionized states of atom, and at the expence of cascade transitions as well

  9. Inner-shell excitation of alkali-metal atoms

    International Nuclear Information System (INIS)

    Inner-shell excitation of alkali-metal atoms, which leads to auto-ionization, is reviewed. The validity of quantum mechanical approximation is analyzed and the importance of exchange and correlation is demonstrated. Basic difficulties in making accurate calculations for inner-shell excitation process are discussed. Suggestions are made for further study of inner-shell process in atoms and ions. (author). 26 refs, 4 figs, 1 tab

  10. Cross sections for short pulse single and double ionization ofhelium

    Energy Technology Data Exchange (ETDEWEB)

    Palacios, Alicia; Rescigno, Thomas N.; McCurdy, C. William

    2007-11-27

    In a previous publication, procedures were proposed for unambiguously extracting amplitudes for single and double ionization from a time-dependent wavepacket by effectively propagating for an infinite time following a radiation pulse. Here we demonstrate the accuracy and utility of those methods for describing two-photon single and one-photon double ionization of helium. In particular it is shown how narrow features corresponding to autoionizing states are easily resolved with these methods.

  11. Calculation of the resonant ionization of helium

    International Nuclear Information System (INIS)

    Autoionizing resonances in the compound system of an electron and a helium ion are observed in kinematically-complete ionization experiments for electrons on helium atoms. The differential cross section is calculated for comparison with these experiments in an equivalent-local form of the distorted-wave impulse approximation. Resonant scattering amplitudes are calculated by a six-state momentum-space coupled-channels method. 10 refs., 1 tab., 2 figs

  12. Study of emission process in hot, optically thin plasma: application to solar active regions

    International Nuclear Information System (INIS)

    Analysis of soft X-ray got in hot and weak density plasmas, such as those in TOKAMAKS and in solar flares, needs a detailed knowledge of emission processes. In this work are presented spectroscopic diagnostics which can be deduced from such spectra analysis and results are applied to magnesium solar spectrum analysis. An important improvement is brought to collisional calculation corresponding to forbidden line populating. For this line, The relative importance of autoionizing states effect, called also resonance effect is studied

  13. The dissociative photoionization of hydrogen via two-electron excitation at 27.5 eV and 30.5 eV

    International Nuclear Information System (INIS)

    The kinetic energy spectra of the protons produced in the dissociative photoionization of H2 directed predominantly along the E vector of a photon beam have been measured at photon energies of 27.5 and 30.5 eV. Protons arising from autoionization of the lowest two-electron excited states exhibit an energy distribution which, unlike previous experimental results, is in accord with theory. (Author)

  14. Resonance ionization spectroscopy for AVLIS

    International Nuclear Information System (INIS)

    A spectroscopic study of three-step resonance photoionization was carried out for atomic gadolinium and uranium. Over 60 high-lying odd-parity states and about 30 autoionizing states were revealed for gadolinium. J-values and radiative lifetimes were determined by the method based on the electric-dipole transition selection rules and by the delayed coincidence method, respectively. Photo-absorption cross-sections were measured by three different methods, and efficient photoionization schemes for AVLIS were determined. (author)

  15. Doubly resonant three-photon double ionization of Ar atoms induced by an EUV free-electron laser

    International Nuclear Information System (INIS)

    A mechanism for three-photon double ionization of atoms by extreme-ultraviolet free-electron laser pulses is revealed, where in a sequential process the second ionization step, proceeding via resonant two-photon ionization of ions, is strongly enhanced by the excitation of ionic autoionizing states. In contrast to the conventional model, the mechanism explains the observed relative intensities of photoelectron peaks and their angular dependence in three-photon double ionization of argon.

  16. Experimental approaches to the measurement of dielectronic recombination

    International Nuclear Information System (INIS)

    In dielectronic recombination, the first step involves a continuum electron which excites a previously bound electron and, in so doing, loses just enough energy to be captured in a bound state (nl). This results in a doubly excited ion of a lower charge state which may either autoionize or emit a photon resulting in a stabilized recombination. The complete signature of the event is an ion of reduced charge and an emitted photon. Methods of measuring this event are discussed

  17. Atomic and Molecular Aspects of Astronomical Spectra

    OpenAIRE

    Sochi, T.

    2012-01-01

    In the first section of this thesis, we present the atomic part of our investigation. A C2+ atomic target was prepared and used to generate theoretical data required in the investigation of recombination lines that arise from collisions between electrons and ions in thin plasma found in planetary nebulae and other astrophysical objects. The R-matrix method of electron scattering theory was used to describe the C2+ plus electron system. Theoretical data concerning bound and autoionizing states...

  18. Double-hump resonance structure of the cross sections for electron impact ionization of Ar5+

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Configuration-average distorted-wave calculations are carried out for electron-impact ionization of Ar5+. Both direct ionization and the indirect excitation autoionization processes are included in our calculations. Our theoretical values are in quite reasonable agreement with the experimental data. The indirect processes contribute up to 50% to the total ionization cross sections. The possible origin of double-hump resonance structure of the cross sections is demonstrated and the contributions of metastable states are also taken into account.

  19. Single and double electron capture cross sections in keV-collisions between fully stripped ions with helium atom

    OpenAIRE

    Ibaaz, Aicha; Dubois, Alain

    2015-01-01

    International audience We present cross section calculations for single-, double-capture, and double capture to auto-ionizing states occurring in the course of collisions between fully stripped ions Aq+ (q≤10) and helium atom at impact energies ranging from 0.25 to 625 keV/u. These calculations were performed by applying a semiclassical nonperturbative close coupling approach, based on the expansion of the scattering wave function into asymptotic bielectronic states with proper translation...

  20. K-shell photoionization of Li-like Ti XX

    Science.gov (United States)

    Liang, Liang; Lu, Xu-yang; Zhou, Chao; Qing, Pang

    2015-04-01

    K-shell photoionization of Li-like Ti XX ions from ground state and first excited state has been studied using the R-matrix method. Through the combination of R-matrix and QB methods, we have not only studied the K-shell photoionization cross section between the first and ninth ionization threshold of Ti XX, but also identified the energy levels of K-shell excited state due to the twelve autoionization Rydberg series.

  1. Femtosecond time-resolved molecular multiphoton ionization: the Na_2 system

    OpenAIRE

    Baumert, Thomas,; Grosser, M.; Thalweiser, Rainer; Gerber, Gustav

    1991-01-01

    We report here the first experimental study of femtosecond time-resolved molecular multiphoton ionization. Femtosecond pump-probe techniques are combined with time-of-flight spectroscopy to measure transient ionization spectra of Na_2 in a molecular-beam experiment. The wave-packet motions in different molecular potentials show that incoherent contributions from direct photoionization of a singly excited state and from excitation and autoionization of a bound doubly excited molecu...

  2. Atomic spectroscopy sympsoium, Gaithersburg, Maryland, September 23--26, 1975. [Program, abstracts, and author index

    Energy Technology Data Exchange (ETDEWEB)

    1975-01-01

    Abstracts of one hundred papers given at the conference are presented along with the conference program and an author index. Session topics include: highly ionized atoms; laser spectroscopy and hyperfine structure; complex spectra; laser spectroscopy, radiation theory; theory of highly ionized atoms and analysis of plasmas; plasma spectroscopy, line strengths; spectral analysis, instrumentation, reference wavelengths; beam foil spectroscopy, line strengths, energy levels; absorption spectroscopy, autoionization, and related theory; and spectral analysis, instrumentation, and VUV physics. (GHT)

  3. Effects of configuration interaction on photoabsorption spectra in the continuum

    International Nuclear Information System (INIS)

    It is pointed out that the proper interpretation of a recently published experimental spectrum from the multilaser photoionization of Sr [Eichmann et al., Phys. Rev. Lett. 90, 233004 (2003)] must account for a radiative transition between two autoionizing states. The application of orthonormality selection rules and of configuration-interaction theory involving the continuous spectrum and the quasicontinuum of the upper part of Rydberg series explains quantitatively the appearance, the shape, and the variation of heights of the observed peaks of resonances

  4. Atomic spectroscopy sympsoium, Gaithersburg, Maryland, September 23--26, 1975

    International Nuclear Information System (INIS)

    Abstracts of one hundred papers given at the conference are presented along with the conference program and an author index. Session topics include: highly ionized atoms; laser spectroscopy and hyperfine structure; complex spectra; laser spectroscopy, radiation theory; theory of highly ionized atoms and analysis of plasmas; plasma spectroscopy, line strengths; spectral analysis, instrumentation, reference wavelengths; beam foil spectroscopy, line strengths, energy levels; absorption spectroscopy, autoionization, and related theory; and spectral analysis, instrumentation, and VUV physics

  5. Argon and krypton Auger spectra induced by ion bombardment of aluminium and silicon surfaces

    International Nuclear Information System (INIS)

    Measurements are reported of Auger (autoionization) spectra of Ar and Kr produced by bombarding Al and Si substrates with Ar+ and Kr+ ions in the 110 eV-5 keV energy range. These are shown to be consistent with the simple Doppler model suggested, for Ne and Al and Si, in a previous paper. Once corrected using the model, the observed Auger energies are shown to correspond to theoretical predictions produced using Dirac-Fock calculations. (Author)

  6. Suppression and Enhancement in Parametric Two-Photon Resonant Nondegenerate Four-Wave Mixing via Quantum Interference

    Institute of Scientific and Technical Information of China (English)

    SUN Jiang; MI Xin; YU Zu-He; JIANG Qian; ZUO Zhan-Chun; WANG Yan-Bang; WU Ling-An; FU Pan-Ming

    2004-01-01

    @@ Quantum interference may lead to suppression and enhancement of the two-photon resonant nondegenerate fourwave mixing signal in a cascade four-level system. Such phenomena are demonstrated in Ba through inducing atomic coherence between the ground state 6s2 and the doubly excited autoionizing Rydberg state 6pnd. This method can be used as a new spectroscopic tool for measuring the transition dipole moment between two highly excited atomic states.

  7. A Model of Calculating Radiative Opacities of Hot Dense Plasmas Based on the Density-Functional Theory

    OpenAIRE

    Kiyokawa, Shuji

    2014-01-01

    We determine the radiative opacity of plasmas in a local thermal equilibrium (LTE) by time-dependent density-functional theory (TDDFT) including autoionization resonances, where the photoabsorption cross section is calculated for an ion embedded in the plasma using the detailed configuration accounting (DCA) method. The abundance of ion with integer occupation numbers is determined by means of the finite temperature density-functional theory (FTDFT). For an Al plasma of temperature T=20 eV an...

  8. Aluminium Lyman ŕ group formation at high-intensity, high-energy laser-matter interaction

    Czech Academy of Sciences Publication Activity Database

    Renner, Oldřich; Rosmej, F. B.; Krouský, Eduard; Sondhauss, P.; Kalachnikov, M. P.; Nickels, P. V.; Uschmann, I.; Förster, E.

    2001-01-01

    Roč. 71, - (2001), s. 623-634. ISSN 0022-4073 R&D Projects: GA MŠk LA 055 Grant ostatní: CZ-DE Bilateral Cooperation in Science(XC) CZE-00-008 Institutional research plan: CEZ:AV0Z1010921 Keywords : laser-produced plasma * x-ray spectra * absolute and relative intensities * autoionization Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.493, year: 2001

  9. Relativistic atomic data for Cu-like tungsten

    Science.gov (United States)

    Safronova, U. I.; Safronova, A. S.; Beiersdorfer, P.

    2013-05-01

    Energy levels, radiative transition probabilities, and autoionization rates for [Ne] 3s2 3p6 3d9 4l' nl , [Ne] 3s2 3p5 3d10 4l' nl (n=4-6), and [Ne] 3s2 3p6 3d9 5l' nl ,(n=5-7) states in Cu-like tungsten (W45+) are calculated using the relativistic many-body perturbation theory method (RMBPT code), the multiconfiguration relativistic Hebrew University Lawrence Livermore Atomic Code (HULLAC code), and the Hartree-Fock-relativistic method (COWAN code). Branching ratios relative to the first threshold and intensity factors are calculated for satellite lines, and dielectronic recombination (DR) rate coefficients are determined for the singly excited, as well as doubly excited non-autoionizing states in Cu-like W45+ ion. Contributions from the autoionizing doubly excited states (with n up to 500), which are particulary important for calculating total DR rates, are estimated. Synthetic dielectronic satellite spectra from Cu-like W are simulated in a broad spectral range from 3 to 70 Å. These calculations provide highly accurate values for a number of W45+ properties useful for a variety of applications including for fusion applications. This research was sponsored by the grant DE-FG02-08ER54951.

  10. Efficient mass-selective three-photon ionization of zirconium atoms

    International Nuclear Information System (INIS)

    In an AVLIS process, 91Zr is selectively removed from natural zirconium by a three-step photoionization wherein Zr atoms are irradiated by a laser beam having a wavelength λ1, selectively raising 91Zr atoms to an odd-parity E1 energy level in the range of 16000-19000 cm-1, are irradiated by a laser beam having a wavelength λ2 to raise the atoms from an E1 level to an even-parity E2 energy level in the range of 35000-37000 cm-1, and are irradiated by a laser beam having a wavelength λ3 to cause a resonant transition of atoms from an E2 level to an autoionizing level above 53506 cm-1. λ3 wavelengths of 5607, 6511 or 5756 A will excite a zirconium atom from an E2 energy state of 36344 cm-1 to an autoionizing level; a λ3 wavelength of 5666 A will cause an autoionizing transition from an E2 level of 36068 cm-1; and a λ3 wavelength of 5662 A will cause an ionizing resonance of an atom at an E2 level of 35904 cm-1. (author)

  11. Three-step resonant photoionization spectroscopy of Ni and Ge: ionization potential and odd-parity Rydberg levels

    International Nuclear Information System (INIS)

    In preparation of a laser ion source, we have investigated multi-step laser ionization via Rydberg and autoionizing states for atomic Ni and Ge using a mass separator with an ion beam energy of 20 keV. For both elements resonant three-step excitation schemes suitable for modern Ti:sapphire laser systems were developed. Rydberg series in the range of principal quantum numbers 20 ≤ n ≤ 80 were localized, assigned and quantum numbers were allocated to the individual resonances. Ionization potentials (IP) were extracted from fits of the individual series and quantum defects of individual levels were analysed for confirmation of series assignment. For Ni the ionization potential could be extracted with significantly increased precision compared to literature with a value of EIP (Ni) = 61 619.77(14) cm-1. Also, at least one notable autoionizing state above the first IP was discovered for both elements, and the different ionization schemes via Rydberg or autoionizing states were compared with respect to line shape, ionization efficiency and selectivity

  12. Electron-impact ionization of W27 +

    Science.gov (United States)

    Pindzola, M. S.; Loch, S. D.

    2016-06-01

    Electron-impact ionization cross sections for W27 + are calculated using a semirelativistic configuration-average distorted-wave (CADW) method. Calculations for direct ionization, excitation autoionization, and branching ratios are compared with recent calculations by Jonauskas et al. [Phys. Rev. A 91, 012715 (2015), 10.1103/PhysRevA.91.012715], who used fully relativistic subconfiguration-average distorted-wave (SCADW) and level-to-level distorted-wave (LLDW) methods. Reasonable agreement is found between the CADW and the recent LLDW calculations for direct ionization of the 4 l (l =0 -1 ,3 ) subshells, but not the 4 d subshell, and between the CADW and recent SCADW-LLDW calculations for excitation autoionization of the 4 l (l =0 -2 ) subshells. Reasonable agreement is also found between the CADW and the recent SCADW calculations, including branching ratios, but both differ from the recent LLDW calculations. Additional CADW calculations are made for excitation autoionization, including branching ratios involving the important 3 l (l =1 -2 ) subshells, not examined by Jonauskas et al. [Phys. Rev. A 91, 012715 (2015), 10.1103/PhysRevA.91.012715].

  13. Design and construction of a Fourier transform soft x-ray interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Spring, John A.

    2000-05-10

    Helium, with its two electrons and one nucleus, is a three-body system. One of the models for investigating correlated electron motion in this system is autoionization, produced via double excitation of the electrons. Predictions about the autoionization spectrum of helium have differed from each other and from preliminary experimental data. However, previous experiments have not been able to distinguish among the theoretical predictions because their energy resolution is not high enough to resolve the narrow linewidths of quasi-forbidden peaks and the resonances that appear in the highest excited states. Consequently, a team of researchers at Lawrence Berkeley National Laboratory have embarked on a project for building a high-resolution Fourier-Transform Soft X-ray (or VUV) interferometer (FTSX) to provide definitive data to answer remaining questions about the autoionization spectrum of helium. The design and construction of this interferometer is described in detail below, including the use of a flexure stage to provide the large path length difference necessary for high resolution measurements, the manufacture of x-ray beamsplitters, a description of the software, and the solution to the problems of stick-slip, vibration, and alignment. Current progress of its development is also described, as well as future goals.

  14. Identification of the Broad Solar Emission Features Near 117 nm

    CERN Document Server

    Avrett, E H; Loeser, R; Avrett, Eugene H.; Kurucz, Robert L.; Loeser, Rudolf

    2006-01-01

    Wilhelm et al. have recently called attention to the unidentified broad emission features near 117 nm in the solar spectrum. They discuss the observed properties of these features in detail but do not identify the source of this emission. We show that the broad autoionizing transitions of neutral sulfur are responsible for these emission features. Autoionizing lines of \\ion{S}{i} occur throughout the spectrum between Lyman alpha and the Lyman limit. Sulfur is a normal contributor to stellar spectra. We use non-LTE chromospheric model calculations with line data from the Kurucz 2004 \\ion{S}{i} line list to simulate the solar spectrum in the range 116 to 118 nm. We compare the results with SUMER disk-center observations from Curdt et al. and limb observations from Wilhelm et al. Our calculations generally agree with the SUMER observations of the broad autoionizing \\ion{S}{i} emission features, the narrow \\ion{S}{i} emission lines, and the continuum in this wavelength region, and agree with basic characteristics...

  15. Quantitative study of multiphoton multiple ionization: Second-harmonic Nd:YAG laser ionization of the doubly excited 2p23P bound state of H-

    International Nuclear Information System (INIS)

    Starting with the H- 2p23P excited bound state, we have studied the problem of direct versus sequential two-photon, two-electron ionization with linearly polarized laser light of λ=5320 A and intensity I=1.4x109 W/cm2. The theory is nonperturbative and electronic-structure oriented. It allows for the multiconfigurational zero-order representation of bound and autoionizing states, for electron correlation, and for the effects of nonorthonormality which cause multielectron excitation even without correlation corrections. The one- and two-electron multichannel continua are represented by square-integrable complex exponential functions. The results show that the sequential process is dominant, even though there exists the H- 4s4p 3P degree autoionizing state, which is near resonance. However, the direct process would dominate if the autoionization width, which is computed to be 1.16x10-3 a.u., happened to be smaller by about a factor of 100, which is a realistic possibility for other systems

  16. Efficient mass-selective three-photon ionization of zirconium atoms

    Science.gov (United States)

    Page, Ralph H.

    1994-01-01

    In an AVLIS process, .sup.91 Zr is selectively removed from natural zirconium by a three-step photoionization wherein Zr atoms are irradiated by a laser beam having a wavelength .lambda..sub.1, selectively raising .sup.91 Zr atoms to an odd-parity E.sub.1 energy level in the range of 16000-19000 cm.sup.-1, are irradiated by a laser beam having a wavelength .lambda..sub.2 to raise the atoms from an E.sub.l level to an even-parity E.sub.2 energy level in the range of 35000-37000 cm.sup.-1 and are irradiated by a laser beam having a wavelength .lambda..sub.3 to cause a resonant transition of atoms from an E.sub.2 level to an autoionizing level above 53506 cm.sup.-1. .lambda..sub.3 wavelengths of 5607, 6511 or 5756 .ANG. will excite a zirconium atom from an E.sub.2 energy state of 36344 cm.sup.-1 to an autoionizing level; a .lambda..sub.3 wavelength of 5666 .ANG. will cause an autoionizing transition from an E.sub.2 level of 36068 cm.sup.-1 ; and a .lambda. .sub.3 wavelength of 5662 .ANG. will cause an ionizing resonance of an atom at an E.sub.2 level of 35904 cm.sup.-1.

  17. Transfer Ionization Cross-sections in Ar Ions on Neon Collisions

    Institute of Scientific and Technical Information of China (English)

    MaXinwen; LiuHelping; ChenXimeng; YangZhihu; ShenZhiyong; WangYoude; YuDeyang; CaiXiaohong; LiuZhaoyuan

    2003-01-01

    We measured the charge exchange cross-sections in collisions of Arq+(q=8, 9, 11, 12) on Ne atoms at low impact energies from 80 keV to 240 keV, and obtained a set of cross-section data. In order to understand the charge exchange processes, we combined the Molecular Classical over-Barrier Model (MCBM) developed by Niehaus[1] with auto-ionization and electron evaporation of multiply excited states. This was described in detail in Refs.[2, 3]. The de-excitation was considered only via Auger process (auto-ionization) in Refs.[4]. In our treatment, the multiply excited states of the projectile undergo Auger decay while the electrons in the multiply excited states of target ions undergo statistical evaporation[5'6]. For projectile auto-ionization, some criterions based on the Auger electron spectra are applied in order to proceed the sequential decay. To calculate the evaporation probability, one has to get the excitation energy of the system. In our case, the excitation energy was obtained according to the states occupied by the captured electrons based on the MCBM. The values are different from the ones in, but more realistic. If one traces each molecularized electrons to its final states in the processes, one can reproduce each possible reaction channel. The processes discussed can be summarized in the following equation

  18. Resonance ionization mass spectroscopy for trace analysis of plutonium

    International Nuclear Information System (INIS)

    Trace amounts of plutonium are determined by means of resonance ionization mass spectroscopy (RIMS). Plutonium atoms evaporated from a heated filament are ionized via a three-step excitation leading to an autoionizing state. The ions are mass-selectively detected with a time-of-flight (TOF) mass spectrometer. Several types of filaments have been tested with respect to atomic yield after evaporation and reproducibility. The best results have been obtained using tantalum as backing and titanium as covering. An overall detection efficiency of 1·10-5 could be determined with such filaments yielding a detection limit of 2·106 atoms of 239Pu

  19. Resonance ionization mass spectroscopy for trace analysis of plutonium

    Science.gov (United States)

    Erdmann, N.; Albus, F.; Deiβenberger, R.; Eberhardt, K.; Funk, H.; Hasse, H.-U.; Herrmann, G.; Huber, G.; Kluge, H.-J.; Köhler, S.; Nunnemann, M.; Passler, G.; Trautmann, N.; Urban, F.-J.

    1995-04-01

    Trace amounts of plutonium are determined by means of resonance ionization mass spectroscopy (RIMS). Plutonium atoms evaporated from a heated filament are ionized via a three-step exciation leading to an autoionizing state. The ions are mass-selectively detected with a time-of-flight (TOF) mass spectrometer. Several types of filaments have been tested with respect to atomic yield after evaporation and reproducibility. The best results have been obtained using tantalum as backing and titanium as covering. An overall detection efficiency of 1ṡ10-5 could be determined with such filaments yielding a detection limit of 2ṡ106 atoms of 239Pu.

  20. Ionization branching ratio control with a resonance attosecond clock

    CERN Document Server

    Argenti, Luca

    2010-01-01

    We investigate the possibility to monitor the dynamics of autoionizing states in real time and control the yields of different ionization channels in helium by simulating XUV-pump IR-probe experiments focused on the N=2 threshold. The XUV pulse creates a coherent superposition of doubly excited states which is found to decay by ejecting electrons in bursts. Prominent interference fringes in the photoelectron angular distribution of the $2s$ and $2p$ ionization channels are observed, along with sizable out-of-phase quantum beats in the yields of the corresponding parent ions.

  1. Ionization Branching Ratio Control with a Resonance Attosecond Clock

    International Nuclear Information System (INIS)

    We investigate the possibility to monitor the dynamics of autoionizing states in real-time and control the yields of different ionization channels in helium by simulating extreme ultraviolet (XUV) pump IR-probe experiments focused on the N=2 threshold. The XUV pulse creates a coherent superposition of doubly excited states which is found to decay by ejecting electrons in bursts. Prominent interference fringes in the photoelectron angular distribution of the 2s and 2p ionization channels are observed, along with significant out-of-phase quantum beats in the yields of the corresponding parent ions.

  2. XUV postionization of fragments of photodissociated C{sub 60}

    Energy Technology Data Exchange (ETDEWEB)

    Lykke, K.R.

    1995-06-01

    We report experimental evidence for the loss of neutral C, C{sub 2}, C{sub 3}, and C{sub 4} from photoexcited C{sub 60} and C{sub 70}. These species are detected by postionization with XUV radiation formed by four-wave mixing in Kr vapor. The fragments have been detected in the nascent distribution (i.e., before total disintegration of the fullerene-size molecular entities). A resonant autoionization transition in C atom has yielded an upper limit to the translational energy release for dissociation into C atoms. The detection of these products gives new insight into the fragmentation mechanism of fullerenes.

  3. Application of the Landau-Zener model and the classical trajectory Monte Carlo method for capture processes in collisions of highly charged ions with light atoms

    International Nuclear Information System (INIS)

    In describing the collision dynamics of processes SEC and DEC (single and double electron capture, respectively) in case of the He target the one active electron approximation was used with a single-centre effective potential for calculations of the dominant (n,l)-level state selective and total charge exchange cross sections. For He target part of the diexcited states of the projectile ions produced by DEC decay by Auger emission of one electron. This autoionizing double capture channel (ADEC) is not taken into account in the present work. (R.P.)

  4. Production of excited atomic hydrogen and deuterium from H2 and D2photodissociation

    Energy Technology Data Exchange (ETDEWEB)

    Bozek, J.D.; Furst, J.E.; Gay, T.J.; Gould, H.; Kilcoyne, A.L.D.; Machacek, J.R.; Martin, F.; McLaughlin, K.W.; Sanz-Vicario, J.L.

    2006-09-17

    We have measured the production of both Ly alpha and H alphafluorescence from atomic H and D for the photodissociation of H2 and D2by linearly polarized photons with energies between 24 and 60 eV. In thisenergy range, excited photofragments result primarily from the productionof doubly excited molecular species which promptly autoionize ordissociate into two neutrals. Our data are compared with ab initiocalculations of the dissociation process, in which both doubly excitedstate production and prompt ionization (nonresonant) channels areconsidered. Agreement between our experimental data and that of earlierwork, and with our theoretical calculations, is qualitative atbest.

  5. Spin-dipole induced lifetime of the least-bound quintet sigma state of He(2S)+He(2S)

    CERN Document Server

    Beams, T J; Whittingham, I B; Beams, Timothy J.; Peach, Gillian; Whittingham, Ian B.

    2006-01-01

    The properties of the least-bound vibrational level (v=14) of the quintet sigma state formed during the ultracold collision of two spin-polarized metastable helium atoms are crucial to studies of photoassociation spectroscopy of metastable helium. We report a calculation of the autoionization lifetime of this state induced by spin-dipole coupling of the quintet sigma state to the singlet sigma state from which Penning and associative ionization processes are highly probable. We find a lifetime of about 150 microseconds, significantly larger than the recent experimental estimates of (4-5) microseconds.

  6. High-order harmonic generation and Fano resonances

    OpenAIRE

    Strelkov, V. V.; Khokhlova, M. A.; Shubin, N. Yu.

    2013-01-01

    We present a high harmonic generation theory which generalizes the strong-field approximation to the resonant case, when the harmonic frequency is close to that of the transition from the ground to an autoionizing state of the generating system. We show that the line shape of the resonant harmonic is a product of the Fano-like factor and the harmonic line which would be emitted in the absence of the resonance. The theory predicts rapid variation of the harmonic phase in the vicinity of the re...

  7. A novel diiminopyridine ligand containing redox active Co(III) mixed sandwich complexes.

    Science.gov (United States)

    Magdzinski, Eleanor; Gobbo, Pierangelo; Workentin, Mark S; Ragogna, Paul J

    2013-10-01

    The synthesis of a diiminopyridine (DIMPY) ligand containing pendant mixed sandwich cobaltocene functionalities on the imine nitrogens was prepared and characterized (18). Its reactivity with 2 equiv of GeCl2·dioxane and SnCl2 in THF yields the respective Lewis base mediated autoionization products (18Ge and 18Sn). Analogous low-valent complexes utilizing an N,N'- differocenyl diiminopyridine support were also prepared (15Ge and 15Sn). All compounds were characterized by spectroscopic and X-ray crystallographic methods. Electrochemical studies were conducted for both 15Sn and the precursor of 18. PMID:24050633

  8. Mayer-Fermi theory and the long sequences in the periodic table

    International Nuclear Information System (INIS)

    Changes in the radial wave functions for d electrons which occur preceding the onset of the transition series of elements and for f electrons preceding the onset of the lanthanide and actinide series are examined. The sensitivity of the radial wave functions to variations in the effective potential is discussed, and the large variation in the radial wave functions between the LS terms of certain types of excited configurations in these regions of the periodic system is analyzed. Several examples of electron-impact ionization are explained by analyzing the effective potentials for the excited electrons in the intermediate autoionizing states. 46 refs., 18 figs

  9. Investigation of angular momenta and correlation patterns in doubly excited states populated by low velocity double charge exchange

    Energy Technology Data Exchange (ETDEWEB)

    Rozet, J.P.; Politis, M.F.; Blumenfeld, L.; Vernhet, D.; Wohrer, K.; Touati, A.; Stephan, C.; Chetioui, A.; Roncin, P.; Laurent, H.

    1987-12-01

    Autoionization branching ratios of O/sup 6+/ doubly excited states are shown to depend sensitively on the K, T and L quantum numbers of these states. A measurement of the decay probabilities to 2s and 2p sublevels has been performed for the (3, 3) and (3, 4) doubly excited states populated in the 1.3 keV/u O/sup 8+/ -> He collision. A new technique of X-ray, energy gain coincidence has been used. Results are discussed in terms of possible distributions K, L for the doubly excited states.

  10. Resonance ionization mass spectroscopy of uranium

    International Nuclear Information System (INIS)

    Resonance ionization mass spectroscopy (RIMS) has been used for the sensitive detection of uranium. The apparatus consists of a laser system with three dye lasers and two pulsed copper vapour lasers and a time-of-flight (TOF) mass spectrometer. The uranium atoms are ionized in a three step excitation with the third step leading to an autoionizing state. Several excitation schemes were investigated and for two schemes all three transitions could be saturated with the available laser power. The hyperfine structure splitting (HFS) of 235U, the isotopic shift (IS) between 235U and 238U as well as isotopic ratios in uranium samples were determined. (Author)

  11. High-resolution, three-step resonance ionization mass spectrometry of gadolinium

    Science.gov (United States)

    Blaum, K.; Bushaw, B. A.; Nörtershäuser, W.; Wendt, K.

    2001-08-01

    High-resolution resonance ionization mass spectrometry has been used to measure triple-resonance autoionization (AI) spectra of gadolinium. Al resonances as narrow as 10 MHz have been observed and isotope shifts and hyperfine structure have been measured in selected AI states. The strongest AI state observed at 49663.576 cm-1 with a photoionization cross section of >3.6×10-15 cm2 was found to have an overall detection efficiency of >3×10-5, allowing application to a number of ultratrace determination problems. Analytical measurements with a diode-laser-based system have been successfully performed on bio-medical tissue samples.

  12. High-resolution, three-step resonance ionization mass spectrometry of gadolinium

    International Nuclear Information System (INIS)

    High-resolution resonance ionization mass spectrometry has been used to measure triple-resonance autoionization (AI) spectra of gadolinium. Al resonances as narrow as 10 MHz have been observed and isotope shifts and hyperfine structure have been measured in selected AI states. The strongest AI state observed at 49663.576 cm-1 with a photoionization cross section of >3.6x10-15 cm2 was found to have an overall detection efficiency of >3x10-5, allowing application to a number of ultratrace determination problems. Analytical measurements with a diode-laser-based system have been successfully performed on bio-medical tissue samples

  13. Rise and fall of the 4d10→4d94f resonance in the Xe isoelectronic sequence

    International Nuclear Information System (INIS)

    The extreme ultraviolet photoabsorption spectrum of a laser-produced lanthanum plasma has been recorded and found to contain a number of discrete features in the 130-eV region. These have been analyzed as 4d10→4d9nf,np transitions in La3+. We show that the 4f transition, which is expected to be the strongest, is not in evidence. The reason is that this resonance, after the collapse of the 4f wave function, has a large autoionization width. We conclude that the 4f orbital in Ba2+ is only partially collapsed, which settles a long-standing discussion of this point

  14. Collisional radiative model for heavy atoms in hot non-local-thermodynamical-equilibrium plasmas

    Science.gov (United States)

    Bar-Shalom, A.; Oreg, J.; Klapisch, M.

    1997-07-01

    A collisional radiative model for calculating non-local-thermodynamical-equilibrium (non-LTE) spectra of heavy atoms in hot plasmas has been developed, taking into account the numerous excited and autoionizing states. This model uses superconfigurations as effective levels with an iterative procedure which converges to the detailed configuration spectrum. The non-LTE opacities and emissivities may serve as a reliable benchmark for simpler on-line models in hydrodynamic code simulations. The model is tested against detailed configuration calculations of selenium and is applied to non-LTE optically thin plasma of lutetium.

  15. Time-dependent wave packet approach to the pulse delay effect upon RbI photoelectron spectrum

    Institute of Scientific and Technical Information of China (English)

    LIU Chunhua; MENG Qingtian; ZHANG Qinggang

    2006-01-01

    The time-resolved photoelectron spectrum (TRPES) of Rbl molecule is simulated using the time-dependent wave-packet method. Both the normal three-photon ionization process and auto-ionization process are involved in the simulation. The calculated results show that the change of delay time will influence the shape of the photoelectron spectrum (PES), and the influence is substantially due to the existence of the crossing between excited states and the strong laser field which will change the position of relevant curves.

  16. Formation of the ion-pair in electron recombination with H+3

    International Nuclear Information System (INIS)

    We present a two-dimensional theoretical study of the formation of the ion-pair, H+2 + H-, in electron recombination with H+3 in its ground electronic and vibrational state. The relevant potential energy surfaces, electronic couplings and autoionization widths are calculated by combining electron scattering calculations with quantum chemistry calculations. The nuclear dynamics on six coupled electronic states is studied by propagating wave packets using the MCTDH (Multi Configuration Time-Dependent Hartree) method. Also the cross section for ion-pair formation in electron recombination with D+3 is calculated.

  17. Experimental Photoionization Cross-Section Measurements in the Ground and Metastable State Threshold Region of Se+

    CERN Document Server

    Sterling, N C; Bilodeau, R C; Kilcoyne, A L D; Red, E C; Phaneuf, R A; Aguilar, A

    2010-01-01

    Absolute photoionization cross-section measurements are reported for Se+ in the photon energy range 18.0-31.0 eV, which spans the ionization thresholds of the 4S_{3/2} ground state and the low-lying 2P_{3/2,1/2} and 2D_{5/2,3/2} metastable states. The measurements were performed using the Advanced Light Source synchrotron radiation facility. Strong photoexcitation-autoionization resonances due to 4p-->nd transitions are seen in the cross-section spectrum and identified with a quantum-defect analysis.

  18. High-resolution Auger spectroscopy on 79 MeV Ar5+, 89 MeV Ar6+, and 136 MeV Ar7+ ions after excitation by helium

    International Nuclear Information System (INIS)

    In this thesis the atomic structure of highly excited Ar6+ and Ar7+ ions was studied. For this 79 MeV Ar5+, 89 MeV Ar6+, and 136 MeV Ar7+ ions of a heavy ion accelerator were excited by a He gas target to autoionizing states and the Auger electrons emitted in the decay were measured in highly-resolving state. The spectra were taken under an observational angle of zero degree relative to the beam axis in order to minimize the kinematical broadening of the Auger lines. (orig./HSI)

  19. The Non-local Thermodynamical Equilibrium Effects on Opacity

    Institute of Scientific and Technical Information of China (English)

    WU Ze-Qing; ZHANG Ben-Ai; QIU Yu-Bo

    2001-01-01

    Based on the detailed configuration accounting (DCA) model, a method is developed to include the resonant photoionization and the excitation-autoionization in the non-local thermodynamical equilibrium (NLTE) average atom(AA) model. Using this new model, the mean charge states and the opacity are calculated for NLTE high-Z plasmas and compared with other results. The agreement w ith AA model is poor at low electron density. The present results agree well with those of DCA model within 10%. The calculations show that the NLTE effects on opacity are strong.

  20. Relativistic calculation of dielectronic recombination for He-like krypton

    Institute of Scientific and Technical Information of China (English)

    Shi Xi-Heng; Wang Yan-Sen; Chen Chong-Yang; Gu Ming-Feng

    2005-01-01

    Dielectronic recombination (DR) cross sections and rate coefficients of He-like Kr are calculated employing the relativistic flexible atomic code, in which autoionization rates are calculated based on the relativistic distorted-wave approximation and the configuration interaction is considered. The Auger and total radiative rates of some strong resonances are listed and compared with the results from multiconfiguration Dirac-Fock and Hebrew University Lawrence Livermore Atomic Code methods. The n-3 scaling law is checked and used to extrapolate rate coefficients. We also show the variation of DR branching ratio with different DR resonances or atomic number Z. The effect of radiative cascades on DR cross sections are studied.

  1. Field ion microscopy of defects in tungsten caused by 140 keV proton irradiation

    International Nuclear Information System (INIS)

    The disturbances in the crystal structure of tungsten during its bombardment with 140 KeV protons (the integral dose of irradiation is 2.1016 protons/cm2, the specimens were irradiated out of the microscope at a room temperature) with the auto-ionic helium microscope operating at 78 deg K were investigated. The random pinpoint defects and small pores in the irradiated specimens were observed. The reasons for discrepancy between the estimated concentration of single displaced atoms and the concentration determined by reference to the autonomous images of the irradiated specimens are discussed

  2. Photoelectron recapture and reemission process associated with double Auger decay in Ar

    Science.gov (United States)

    Hikosaka, Y.; Mashiko, R.; Odagiri, T.; Adachi, J.; Tanaka, H.; Kosuge, T.; Ito, K.

    2016-06-01

    Multielectron coincidence spectroscopy has been performed for Ar at a photon energy of only 0.2 eV above the 2 p1 /2 threshold. It is revealed that a postcollision interaction induced by double Auger decay leads to photoelectron recapture, followed by reemission of the captured electron, where the recapture of the slow photoelectron forms the A r2 + Rydberg-excited states which subsequently undergo autoionization. The energy correlation of the emitted electrons discloses that both direct and cascade paths in the double Auger decay contribute to the photoelectron recapture.

  3. Laser resonance ionization scheme development for tellurium and germanium at the dual Ti:Sa-Dye ISOLDE RILIS

    Science.gov (United States)

    Day Goodacre, T.; Fedorov, D.; Fedosseev, V. N.; Forster, L.; Marsh, B. A.; Rossel, R. E.; Rothe, S.; Veinhard, M.

    2016-09-01

    The resonance ionization laser ion source (RILIS) is the principal ion source of the ISOLDE radioactive beam facility based at CERN. Using the method of in-source laser resonance ionization spectroscopy, a transition to a new autoionizing state of tellurium was discovered and applied as part of a three-step, three-resonance, photo-ionization scheme. In a second study, a three-step, two-resonance, photo-ionization scheme for germanium was developed and the ionization efficiency was measured at ISOLDE. This work increases the range of ISOLDE RILIS ionized beams to 31 elements. Details of the spectroscopy studies are described and the new ionization schemes are summarized.

  4. K-shell photoionization of Li-like Ti XX

    International Nuclear Information System (INIS)

    K-shell photoionization of Li-like highly ionized ions can introduce rich absorption lines that can be used for fusion plasma diagnostics. In this paper K-shell photoionization of Li-like Ti XX ions from the ground state and the first excited state (1s22p 2P) has been studied using the R-matrix method. Through the combination of R-matrix and QB methods, we have not only studied the K-shell photoionization cross section between the first and ninth ionization threshold of Ti XX, but also identified the energy levels of K-shell excited state due to the twelve autoionization Rydberg series

  5. Perspectives on double-excitations in TDDFT

    CERN Document Server

    Elliott, Peter; Canahui, Chris; Maitra, Neepa T

    2011-01-01

    The adiabatic approximation in time-dependent density functional theory (TDDFT) yields reliable excitation spectra with great efficiency in many cases, but fundamentally fails for states of double excitation character. We discuss how double-excitations are at the root of some of the most challenging problems for TDDFT today. We then present new results for (i) the calculation of autoionizing resonances in the helium atom, (ii) understanding the nature of the double excitations appearing in the quadratic response function, and (iii) retrieving double-excitations through a real-time semiclassical approach to correlation in a model quantum dot.

  6. AM data activities (1999-2001) at Data and Planning Center, National Institute for Fusion Science, Japan

    International Nuclear Information System (INIS)

    In this report recent work at the Data and Planning Center, NIFS, consisting of compilation activities, research and collaboration programmes, data publications, and future plans, is presented. The NIFS website and services, the status of data records in the numerical databases (AMDIS, CHART, SPUTY and BACKS) and bibliographic databases are reviewed. These databases are accessed through the www and require a simple user registration process. The new database on recombination processes has been constructed and contains 26000 records for cross sections and rate coefficients for radiative, dielectronic or three-body recombination. New numerical databases in progress in 2001 include impact and ion/atom/molecule impact for molecular processes and autoionization

  7. Non-perturbative methods applied to multiphoton ionization

    International Nuclear Information System (INIS)

    The use of non-perturbative methods in the treatment of atomic ionization is discussed. Particular attention is given to schemes of the type proposed by Keldysh where multiphoton ionization and tunnel auto-ionization occur for high intensity fields. These methods are shown to correspond to a certain type of expansion of the T-matrix in the intra-atomic potential; in this manner a criterium concerning the range of application of these non-perturbative schemes is suggested. A brief comparison between the ionization rate of atoms in the presence of linearly and circularly polarized light is presented. (Author)

  8. An energy-dispersive VUV beamline for NEXAFS and other CFS/CIS studies

    Energy Technology Data Exchange (ETDEWEB)

    Batchelor, D.R. [Universitaet Wuerzburg, Experimentelle Physik II, Am Hubland, D-97074 Wuerzburg (Germany)]. E-mail: David.Batchelor@physik.uni-wuerzburg.de; Schmidt, Th. [Universitaet Wuerzburg, Experimentelle Physik II, Am Hubland, D-97074 Wuerzburg (Germany); Follath, R. [BESSY GmbH, Albert-Einstein-Strasse 15, 12489 Berlin (Germany); Jung, C. [BESSY GmbH, Albert-Einstein-Strasse 15, 12489 Berlin (Germany); Fink, R. [Physikalische Chemie II, Universitaet Erlangen-Nuernberg, Egerlandstrasse 3, D-91058 Erlangen (Germany); Knupfer, M. [IFW Dresden, D-01171 Dresden (Germany); Schoell, A. [Universitaet Wuerzburg, Experimentelle Physik II, Am Hubland, D-97074 Wuerzburg (Germany); Noll, T. [BESSY GmbH, Albert-Einstein-Strasse 15, 12489 Berlin (Germany); Siewert, F. [BESSY GmbH, Albert-Einstein-Strasse 15, 12489 Berlin (Germany); Buechner, B. [IFW Dresden, D-01171 Dresden (Germany); Umbach, E. [Universitaet Wuerzburg, Experimentelle Physik II, Am Hubland, D-97074 Wuerzburg (Germany)

    2007-06-01

    By combining the photon energy dispersion of a plane-grating XUV monochromator with the imaging properties of a hemispherical electron energy analyzer, energy-dispersive electron spectroscopy is possible. This multiplex technique allows the utilization of various electron spectroscopies, such as near-edge X-ray absorption (NEXAFS), photoemission (XPS) and Auger/autoionization spectroscopy, without time-consuming scanning of the photon energy. Thus, changes on short time scales may be monitored with full spectroscopic information. We present the design for an upgrade of the existing BESSY UE52-PGM beamline and the results of a pilot energy-dispersive experiment on condensed C{sub 60} molecules.

  9. A NEW TECHNIQUE TO STUDY RYDBERG STATES BY MULTIPHOTON IONIZATION SPECTROSCOPY

    OpenAIRE

    Verma, R.; Chanda, A.

    1987-01-01

    A new technique to study the Rydberg states of the Ba atom has been developed. In this technique a Multiphoton Ionization signal is detected by selective excitation of the ground state ion (6s) to an excited state (6p), which results in a collimated Amplified Spontaneous Emission (ASE) signal at the 6p→5d transition of Ba*. Discrete Rydberg states, 6snℓ (ℓ=0,2), as well as autoionizing Rydberg states, 5dnℓ (ℓ=0,2) and 6pnℓ (ℓ=0,2) are observed by this novel but very simple method.

  10. NON-PERTURBATIVE METHODS APPLIED TO MULTIPHOTON IONIZATION

    OpenAIRE

    Brandi, H.; Davidovich, L.; Zagury, N.

    1982-01-01

    We discuss the use of non-perturbative methods in the treatment of atomic ionization. Particular attention is given to schemes of the type proposed by Keldysh where multiphoton ionization and tunnel auto-ionization occur for high intensity fields. These methods are shown to correspond to a certain type of expansion of the T-matrix in the intra-atomic potential, in this manner a criterium concerning the range of application of these non-perturbative scheme is suggested. A brief comparison betw...

  11. Coherence of Auger and inter-Coulombic decay processes in the photoionization of Ar@C60 versus Kr@C60

    CERN Document Server

    Magrakvelidze, Maia; Javani, Mohammad H; Madjet, Mohamed E; Manson, Steven T; Chakraborty, Himadri S

    2015-01-01

    For the asymmetric spherical dimer of an endohedrally confined atom and a host fullerene, an innershell vacancy of either system can decay through the continuum of an outer electron hybridized between the systems. Such decays, viewed as coherent superpositions of the single-center Auger and two-center inter-Coulombic (ICD) amplitudes, are found to govern leading decay mechanisms in noble-gas endofullerenes, and are likely omnipresent in this class of nanomolecules. A comparison between resulting autoionizing resonances calculated in the photoionization of Ar@C60 and Kr@C60 exhibits details of the underlying processes.

  12. Resonant Auger-intercoulombic hybridized decay in the photoionization of endohedral fullerenes

    CERN Document Server

    Javani, Mohammad H; De, Ruma; Madjet, Mohamed E; Manson, Steven T; Chakraborty, Himadri S

    2013-01-01

    Considering the photoionization of Ar@C60, we predict resonant femtosecond decays of both Ar and C60 vacancies through the continua of atom-fullerene hybrid final states. The resulting resonances emerge from the interference between simultaneous autoionizing and intercoulombic decay (ICD) processes. For Ar 3s-->np excitations, these resonances are far stronger than the Ar-to-C60 resonant ICDs, while for C60 excitations they are strikingly larger than the corresponding Auger features. The results indicate the power of hybridization to enhance decay rates, and modify lifetimes and line profiles.

  13. Associative ionization between sodium atoms excited by polarized light. Test of a theoretical model by comparison with a variety of experiments. Extension to the case of the potassium

    International Nuclear Information System (INIS)

    This thesis presents a theoretical model of the associative collisional ionization reaction between two sodium atoms, excited by a polarized laser beam. This model combines the multi-channels quantum defect treatment of the molecular autoionization at short internuclear distances and the description of the long range dynamic. This model is compared to many experimental results. It is in agreement with measures of the ion production rate. For the internuclear long range dynamic treatment, the model is limited: results concerning the ionization cross section are not suitable. The model is broadened to the associative ionization study between two potassium atoms where the experimental data are rare. (A.L.B.)

  14. Relativistic energy levels and oscillator strengths for the ns(n-1)d 1D-ns21S transitions of the alkaline earth atoms

    International Nuclear Information System (INIS)

    A fully relativistic Dirac-Fock method with Breit and QED corrections has been employed to study energy levels and oscillator strengths for the ns(n-1)d 1D-ns21S transitions of the alkaline earth atoms. In calculation, the authors consider significant Breit and QED corrections, the results are in good agreements with recent experimental data and other theoretical values. The results show that it is feasible to obtain the highly Rybderg states of the alkaline earth atoms, especially the autoionization states, by use of quadrupole transitions as an intermediate resonance

  15. Second bound state of PsH

    OpenAIRE

    Mitroy, J.; Bromley, M. W. J.

    2006-01-01

    The existence of a second bound state of PsH that is electronically stable and also stable against positron annihilation by the normal 2gamma and 3gamma processes is demonstrated by explicit calculation. The state can be found in the 2,4So symmetries with the two electrons in a spin triplet state. The binding energy against dissociation into the H(2p) + Ps(2p) channel was 6.06x10-4 Hartree. The dominant decay mode of the states will be radiative decay into a configuration that autoionizes or ...

  16. e-He+ scattering phase shifts in the nonresonant region

    International Nuclear Information System (INIS)

    The double excited autoionization states of the He atom and the e-He+ scattering phase shifts in the nonresonant region near the first ionization threshold are examined in detail, using a simple configuration-interaction approach. The phase shifts reflect the short-range electron-electron correlations. The S, P and D partial wave phase shifts of high accuracy are obtained for both the singlet and the triplet spin states. It shows excellent agreement between the present calculation and existing theoretical results

  17. Theoretical study of the photoionization of the excited 1s22s2p 1,3Po states of the Be-like B+ ion

    International Nuclear Information System (INIS)

    Photoionization of the first excited p states of the Be-like B+ ion, which interact with the even-parity continua, has been studied theoretically. The calculated photoionization cross sections contain a number of autoionizing Rydberg series of resonances converging to the B2+ 2p, 3s, 3p, and 3d states. Lower members of the Rydberg series of resonances with n≤12 are identified and resonance positions Er, effective quantum numbers n*, and widths Γ are presented. Excellent agreement between length- and velocity-gauge results is found, along with overall good agreement with previous work

  18. Theoretical study for photoionization of Mg-like S4+ ion

    International Nuclear Information System (INIS)

    Photoionization of the Mg-like S4+ ion has been studied for the ground 1S and excited 3,1P initial states. Using a noniterative eigenchannel R-matrix method, we have investigated the partial photoionization cross sections leading to the final photo-ionic 3l states. The autoionizing resonance structures arising from the ground and excited states are identified and characterized. Our calculational results, which show excellent agreement between length and velocity gauges, are compared with the available previous Opacity Project results, and some significant discrepancies are found.

  19. Interference effect involving doubly excited states [1s2p](3,1P)3p2 (J=1) in 1s photoionization of neon

    International Nuclear Information System (INIS)

    Within the framework of multiconfiguration Dirac-Fock (MCDF) method, the interference between photoionization and photoexcitation autoionization involving the doubly excited states [1s2p](3,1P)3p2 (J=1) of neon have been studied theoretically. The present results indicate the fine structure of the interference spectra in experiment and show the dominant contribution to the total profile resulting from some individual resonances. Reasonable agreement is found between the present calculations and other available theoretical and experimental results. In addition, some interesting trends of variation of Fano parameters q and ρ2 have also been pointed out. (author)

  20. Interferometry with Strontium Ions

    Science.gov (United States)

    Jackson, Jarom; Lambert, Enoch; Otterstrom, Nils; Jones, Tyler; Durfee, Dallin

    2014-05-01

    We describe progress on a cold ion matter-wave interferometer. Cold Strontium atoms are extracted from an LVIS. The atoms will be photo-ionized with a two-photon transition to an auto-ionizing state in the continuum. The ions will be split and recombined using stimulated Raman transitions from a pair of diode lasers injection locked to two beams from a master laser which have been shifted up and down by half the hyperfine splitting. We are developing laser instrumentation for this project including a method to prevent mode-hopping by analyzing laser frequency noise, and an inexpensive, robust wavelength meter. Supported by NSF Award No. 1205736.

  1. Cold Strontium Ion Source for Ion Interferometry

    Science.gov (United States)

    Jackson, Jarom; Durfee, Dallin

    2015-05-01

    We are working on a cold source of Sr Ions to be used in an ion interferometer. The beam will be generated from a magneto-optical trap (MOT) of Sr atoms by optically ionizing atoms leaking out a carefully prepared hole in the MOT. A single laser cooling on the resonant transition (461 nm) in Sr should be sufficient for trapping, as we've calculated that losses to the atom beam will outweigh losses to dark states. Another laser (405 nm), together with light from the trapping laser, will drive a two photon transition in the atom beam to an autoionizing state. Supported by NSF Award No. 1205736.

  2. Many-body processes in atomic and molecular physics: Progress report, September 1, 1986-August 31, 1988

    International Nuclear Information System (INIS)

    This paper discusses the work being done at the University of Kansas in many-body processes in atomic and molecular physics. The particular topics discussed are: Complex-coordinate coupled-channel methods for autoionization predissociation and multiphoton resonances; intensity-dependent ionization potential and above-threshold multiphoton ionization; collisional processes in the presence of laser fields; Floquet-Liouville supermatrix approach to intense field multiphoton and nonlinear optical processes; and classical time-dependent self-consistent field approach to intense field multiphoton dissociation of molecules. 17 refs., 16 figs

  3. Inner- and outer-shell excitation in lithium isoelectronic sequence

    International Nuclear Information System (INIS)

    The inner-shell excitation 1s22s2Se → 1s2s22Se, which leads to autoionization (Auger transition), as well as the outer-shell excitation 1s22s 2Se → 1s22p 2P0 transitions have been investigated in Li, Be+, B2+ and C3+ ions of the lithium isoelectronic sequence employing the configuration interaction wave functions for both the initial and final states involved in the transition matrix element. Results are compared with other available theoretical predictions and experimental observations. Comparison shows that our present theoretical results are encouraging. (author). 33 refs, 5 tabs

  4. Charge-exchange-driven X-ray emission from highly ionized plasma jets

    Energy Technology Data Exchange (ETDEWEB)

    Rosmej, F.B. [Universite de Provence et CNRS UMR 6633, Centre de St Jerome, 13 - Marseille (France); Lisitsa, V.S. [Russian Research Center Kurchatov, Moscow (Russian Federation); Schott, R.; Dalimier, E. [Paris-6 Univ., 75 - Paris (France); Schott, R.; Dalimier, E. [Ecole Polytechnique, LULI, 91 - Palaiseau (France); Riley, D.; Delserieys, A. [Queens Univ., Belfast (United Kingdom); Renner, O.; Krousky, E. [Institute of Physics, Prague (Czech Republic)

    2006-12-15

    The interaction of highly ionized laser-produced plasma jets with gases has been studied with X-ray microscopic methods. Simultaneous high spectral and 2-dimensional spatial resolution provided a detailed topological structure of the counter-propagating plasma and discovered a gas pressure-dependent X-ray emission structure inside the jets of H-like and He-like aluminum ions. At larger distances from the target, anomalous high (3 orders of magnitude) intensities of Li-like intercombination transitions from double excited states have been identified. Charge-exchange-driven cascading in autoionizing states is proposed to explain the experimental findings. (authors)

  5. Inner shell ionization in beta decay

    International Nuclear Information System (INIS)

    The purpose of this paper is to examine various ways to resolve the discrepancy that exists between the theoretical calculations on K-shell autoionization probabilities in #betta# decay and the measured values. The chequered history of the subject may be traced through the reviews and papers of Freedman and co workers. Suffice it to say that Isozumi et al (ISM) found that the Law and Campbell (LC) model over counted the shake-off contribution by a factor of two; this correction thus destroys the remarkable agreement between theory and experiment

  6. Dissociative recombination of N2H+

    Science.gov (United States)

    dos Santos, S. Fonseca; Ngassam, V.; Orel, A. E.; Larson, Å.

    2016-08-01

    The direct and indirect mechanisms of dissociative recombination of N2H+ are theoretically studied. At low energies, the electron capture is found to be driven by recombination into bound Rydberg states, while at collision energies above 0.1 eV, the direct capture and dissociation along electronic resonant states becomes important. Electron-scattering calculations using the complex Kohn variational method are performed to obtain the scattering matrix as well as energy positions and autoionization widths of resonant states. Potential-energy surfaces of electronic bound states of N2H and N2H+ are computed using structure calculations with the multireference configuration interaction method. The cross section for the indirect mechanism is calculated using a vibrational frame transformation of the elements of the scattering matrix at energies just above the ionization threshold. Here vibrational excitations of the ionic core from v =0 to v =1 and v =2 for all three normal modes are considered and autoionization is neglected. The cross section for the direct dissociation along electronic resonant states is computed with wave-packet calculations using the multiconfiguration time-dependent Hartree method, where all three internal degrees of freedom are considered. The calculated cross sections are compared to measurements.

  7. Kinematics of 3-body in Ionization Collision

    International Nuclear Information System (INIS)

    In this thesis we study three body problems in the frame of the collision theory. First, we deal with the process of autoionization by ion impact where the line profile of the electron emitted is strongly affected by the post-collision interaction with the Coulomb field of the outgoing projectile.Here we analyze how these effects are modified when the projectile velocity is in the close vicinity of the resonant electron velocity.In this energy range, the analysis of the resonance contribution is hindered by the characteristic 'electron capture to the continuum' divergence in the direct term.Here we present a detailed theoretical study of the interplay between both contributions, based on a generalization of the Final-State Interaction model.Finally we propose a modified parameterization of the autoionization line shape in the vicinity of the ECC cusp.Secondly, we study the direct ionization of an atomic target by the impact of a charge projectile, through analysis of the quintuple differential cross section (QDCS) which gives the most complete information about a ionization collision.Its study, without any approximation on the mass ratios can unveil new, not previously observed, structures.In particular, in this work the ionization of Hydrogen molecules by the impact of positrons and muons was studied and a new structure that has not been identified until now was found. Its main characteristics and a possible explanation are presented

  8. Atomic and Molecular Complex Resonances from Real Eigenvalues Using Standard (Hermitian) Electronic Structure Calculations.

    Science.gov (United States)

    Landau, Arie; Haritan, Idan; Kaprálová-Žd'ánská, Petra Ruth; Moiseyev, Nimrod

    2016-05-19

    Complex eigenvalues, resonances, play an important role in a large variety of fields in physics and chemistry. For example, in cold molecular collision experiments and electron scattering experiments, autoionizing and predissociative metastable resonances are generated. However, the computation of complex resonance requires modifications of standard electronic structure codes and methods, which are not always straightforward, in addition, application of complex codes requires more computational efforts. Here we show how resonance eigenvalues, positions and widths, can be calculated using the standard, widely used, electronic-structure packages. Our method enables the calculations of the complex resonance eigenvalues by using analytical continuation procedures (such as Padé). The key point in our approach is the existence of narrow analytical passages from the real axis to the complex energy plane. In fact, the existence of these analytical passages relies on using finite basis sets. These passages become narrower as the basis set becomes more complete, whereas in the exact limit, these passages to the complex plane are closed. As illustrative numerical examples we calculated the autoionization Feshbach resonances of helium, hydrogen anion, and hydrogen molecule. We show that our results are in an excellent agreement with the results obtained by other theoretical methods and with available experimental results. PMID:26677725

  9. Probing the Dynamics of Rydberg and Valence States of Molecular Nitrogen with Attosecond Transient Absorption Spectroscopy.

    Science.gov (United States)

    Warrick, Erika R; Cao, Wei; Neumark, Daniel M; Leone, Stephen R

    2016-05-19

    An attosecond pulse is used to create a wavepacket in molecular nitrogen composed of multiple bound and autoionizing electronic states of Rydberg and valence character between 12 and 16.7 eV. A time-delayed, few-femtosecond, near-infrared (NIR) laser pulse is used to couple individual states in the wavepacket to multiple neighboring states, resulting in time-dependent modification of the absorption spectrum and revealing both individual quantum beats of the wavepacket and the energy shifts of the excited states in the presence of the strong NIR field. The broad bandwidth of the attosecond pulse and high energy resolution of the extreme ultraviolet spectrometer allow the simultaneous observation of time-dependent dynamics for many individual vibrational levels in each electronic state. Quantum beating with periods from 1.3 to 12 fs and transient line shape changes are observed among vibrational levels of a progression of electronically autoionizing Rydberg states leading to the excited A (2)Πu N2(+) ion core. Vibrational levels in the valence b (1)Πu state exhibit 50 fs oscillation periods, revealing superpositions between individual vibrational levels within this state. Comparisons are made to previous studies of electronic wavepackets in atoms that highlight similarities to atomic behavior yet illustrate unique contributions of the diatomic molecular structure to the wavepacket, including the influence of different electronic potentials and vibrational-level-specific electronic dynamics. PMID:26862883

  10. Electron-impact ionization of P-like ions forming Si-like ions

    International Nuclear Information System (INIS)

    We have calculated electron-impact ionization (EII) for P-like systems from P to Zn15+ forming Si-like ions. The work was performed using the flexible atomic code (FAC) which is based on a distorted-wave approximation. All 3ℓ → nℓ' (n = 3-35) excitation-autoionization (EA) channels near the 3p direct ionization threshold and 2ℓ → nℓ' (n = 3-10) EA channels at the higher energies are included. Close attention has been paid to the detailed branching ratios. Our calculated total EII cross sections are compared both with previous FAC calculations, which omitted many of these EA channels, and with the available experimental results. Moreover, for Fe11+, we find that part of the remaining discrepancies between our calculations and recent measurements can be accounted for by the inclusion of the resonant excitation double autoionization process. Lastly, at the temperatures where each ion is predicted to peak in abundances in collisional ionization equilibrium, the Maxwellian rate coefficients derived from our calculations differ by 50%-7% from the previous FAC rate coefficients, with the difference decreasing with increasing charge.

  11. Femtosecond laser enhanced current in a thermionic diode with barium vapor

    International Nuclear Information System (INIS)

    We studied the signal from a thermionic diode when a femtosecond laser beam was spatially overlapped by an excimer pumped dye laser beam. The nanosecond dye laser was scanned from 435 to 438 nm in order to excite the autoionizing levels of barium by two photon absorption. The broadband ultrashort laser light was centered at 427 nm, which is also above the first ionization limit of barium. The bias voltage between the cell body and the tungsten rod (set at either 9 or 0 V) was used to collect electrons after the barium ions had been created by multiphoton (auto) ionization. The overall background of the thermionic signal was appreciably elevated due to the two photon ionization by the broadband femtosecond laser. We measured the thermionic signal with and without femtosecond laser overlap, and with a biasless and biased thermionic diode. The effect of the femtosecond laser was appreciable enhancement of the background ionization continuum. This was especially visible in the presence of noble gases at pressure of 50 mbar. Argon produced the largest and helium produced the smallest enhancement in the background continuum. In addition, we observed a few broad spectral features of a presumably collision induced nature. - Highlights: • Femtosecond laser beam spatially overlapped by excimer pumped dye laser beam. • The nanosecond dye laser scanned from 435 to 438 nm for two photon absorption. • Thermionic signal detection of Ba autoionizing levels. • The femtosecond laser enhanced the background ionization continuum. • Broad spectral features of presumably collision induced nature have been observed

  12. Ionization photophysics and Rydberg spectroscopy of diacetylene

    KAUST Repository

    Schwell, Martin

    2012-11-01

    Photoionization of diacetylene was studied using synchrotron radiation over the range 8-24 eV, with photoelectron-photoion coincidence (PEPICO) and threshold photoelectron-photoion coincidence (TPEPICO) techniques. Mass spectra, ion yields, total and partial ionization cross-sections were measured. The adiabatic ionization energy of diacetylene was determined as IE ad=(10.17±0.01) eV, and the appearance energy of the principal fragment ion C4H+ as AE=(16.15±0.03) eV. Calculated appearance energies of other fragment ions were used to infer aspects of dissociation pathways forming the weaker fragment ions C+ 4, C3H+, C+3 and C 4H+. Structured autoionization features observed in the PEPICO spectrum of diacetylene in the 11-13 eV region were assigned to vibrational components of three new Rydberg series, R1(nsσg, n=4-11), R2(ndσg, n=4-7) and R3(ndδg, n=4-6) converging to the A2Πu state of the cation, and to a new series R01(nsσg, n=3) converging to the B\\' 2Σ+u state of the cation. The autoionization mechanisms and their consistence with specific selection rules are discussed. © 2012 Taylor and Francis.

  13. STORAGE RING CROSS-SECTION MEASUREMENTS FOR ELECTRON IMPACT SINGLE AND DOUBLE IONIZATION OF Fe9+ AND SINGLE IONIZATION OF Fe10+

    International Nuclear Information System (INIS)

    We have measured electron impact ionization from the ground state of Fe9+ and Fe10+ over the relative electron-ion collision energy ranges 200-1900 eV and 250-1800 eV, respectively. The ions were confined in an ion storage ring long enough for essentially all metastable levels to radiatively relax to the ground state. For single ionization, we find a number of discrepancies between the existing theoretical cross sections and our results. The calculations appear to neglect some excitation-autoionization (EA) channels, particularly from n = 3 to n' excitations, which are important near threshold, and those from n = 2 → 3 excitations, which contribute at about 650 eV. Conversely, at higher energies the calculations appear to overestimate the importance of EA channels due to excitation into levels where n ≥ 4. The resulting experimental rate coefficients agree with the most recent theory for Fe9+ to within 16% and for Fe10+ to within 19% at temperatures where these ions are predicted to form in collisional ionization equilibrium. We have also measured double ionization of Fe9+ forming Fe11+ in the energy range 450-3000 eV and found that although there is an appreciable cross section for direct double ionization, the dominant mechanism appears to be through direct ionization of an inner shell electron producing an excited state that subsequently stabilizes through autoionization.

  14. Effect of electronic angular momentum exchange on photoelectron anisotropy following the two-color ionization of krypton atoms

    Science.gov (United States)

    Saquet, N.; Holland, D. M. P.; Pratt, S. T.; Cubaynes, D.; Tang, X.; Garcia, G. A.; Nahon, L.; Reid, K. L.

    2016-03-01

    We present photoelectron energy and angular distributions for resonant two-photon ionization via several low-lying Rydberg states of atomic Kr. The experiments were performed by using synchrotron radiation to pump the Rydberg states and a continuous-wave laser to probe them. Photoelectron images, recorded with both linear and circular polarized pump and probe light, were obtained in coincidence with mass-analyzed Kr ions. The photoelectron angular distributions and branching ratios for direct ionization into the K r+2P3 /2 and 2P1 /2 spin-orbit continua show considerable dependence on the intermediate level, as well as on the polarizations of the pump and probe light. Photoelectron images were also recorded with several polarization combinations following two-color excitation of the (2P1 /2 ) 5 f [5/2 ] 2 autoionizing resonance. These results are compared with the results of recent work on the corresponding autoionizing resonance in atomic Xe [E. V. Gryzlova et al., New J. Phys. 17, 043054 (2015), 10.1088/1367-2630/17/4/043054].

  15. Collisional-radiative modeling of the L-shell emission of Mo30+ to Mo33+ emitted from a high-temperature endash low-density tokamak plasma

    International Nuclear Information System (INIS)

    The x-ray spectra of several highly stripped molybdenum ions have been recorded between 0.6 and 5.5 A in the Frascati tokamak upgrade with a rotating crystal spectrometer. Detailed, quasi-steady-state collisional-radiative models have been used to interpret emission features from inner shell, electron impact excitations in molybdenum ions near the neonlike charge state and to characterize the charge state distribution in the plasma. Processes such as resonant excitation, excitation autoionization, and dielectronic recombination have been included in the models of the molybdenum ions close-quote emission features. Introducing the excitation-autoionization process into ionization equilibrium calculations brings agreement between observations and calculations of the relative ionization equilibrium fractions of highly stripped molybdenum ions. Absolutely calibrated spectra and detailed models for the excitation processes in these molybdenum ions allow us to calculate crucial plasma parameters, such as the concentration of impurity ions in the plasma and the amount of power lost from the plasma through impurity line radiation. copyright 1996 The American Physical Society

  16. Probing microhydration effect on the electronic structure of the GFP chromophore anion: Photoelectron spectroscopy and theoretical investigations

    Energy Technology Data Exchange (ETDEWEB)

    Bhaskaran-Nair, Kiran; Shelton, William A. [Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Center for Computation and Technology, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Valiev, Marat; Kowalski, Karol, E-mail: karol.kowalski@pnnl.gov [William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, K8-91, P.O. Box 999, Richland, Washington 99352 (United States); Deng, S. H. M.; Wang, Xue-Bin, E-mail: xuebin.wang@pnnl.gov [Physical Sciences Division, Pacific Northwest National Laboratory, K8-88, P.O. Box 999, Richland, Washington 99352 (United States)

    2015-12-14

    The photophysics of the Green Fluorescent Protein (GFP) chromophore is critically dependent on its local structure and on its environment. Despite extensive experimental and computational studies, there remain many open questions regarding the key fundamental variables that govern this process. One outstanding problem is the role of autoionization as a possible relaxation pathway of the excited state under different environmental conditions. This issue is considered in our work through combined experimental and theoretical studies of microsolvated clusters of the deprotonated p-hydroxybenzylidene-2,3-dimethylimidazolinone anion (HBDI{sup −}), an analog of the GFP chromophore. Through selective generation of microsolvated structures of predetermined size and subsequent analysis of experimental photoelectron spectra by high level ab initio methods, we are able to precisely identify the structure of the system, establish the accuracy of theoretical data, and provide reliable description of auto-ionization process as a function of hydrogen-bonding environment. Our study clearly illustrates the first few water molecules progressively stabilize the excited state of the chromophore anion against the autodetached neutral state, which should be an important trait for crystallographic water molecules in GFPs that has not been fully explored to date.

  17. Probing microhydration effect on the electronic structure of the GFP chromophore anion: Photoelectron spectroscopy and theoretical investigations

    Science.gov (United States)

    Bhaskaran-Nair, Kiran; Valiev, Marat; Deng, S. H. M.; Shelton, William A.; Kowalski, Karol; Wang, Xue-Bin

    2015-12-01

    The photophysics of the Green Fluorescent Protein (GFP) chromophore is critically dependent on its local structure and on its environment. Despite extensive experimental and computational studies, there remain many open questions regarding the key fundamental variables that govern this process. One outstanding problem is the role of autoionization as a possible relaxation pathway of the excited state under different environmental conditions. This issue is considered in our work through combined experimental and theoretical studies of microsolvated clusters of the deprotonated p-hydroxybenzylidene-2,3-dimethylimidazolinone anion (HBDI-), an analog of the GFP chromophore. Through selective generation of microsolvated structures of predetermined size and subsequent analysis of experimental photoelectron spectra by high level ab initio methods, we are able to precisely identify the structure of the system, establish the accuracy of theoretical data, and provide reliable description of auto-ionization process as a function of hydrogen-bonding environment. Our study clearly illustrates the first few water molecules progressively stabilize the excited state of the chromophore anion against the autodetached neutral state, which should be an important trait for crystallographic water molecules in GFPs that has not been fully explored to date.

  18. Probing microhydration effect on the electronic structure of the GFP chromophore anion. Photoelectron spectroscopy and theoretical investigations

    Energy Technology Data Exchange (ETDEWEB)

    Bhaskaran-Nair, Kiran [Louisiana State Univ., Baton Rouge, LA (United States); Valiev, Marat [Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Atmospheric Science and Global Change Div. (ASGC); Deng, Shihu [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Shelton, William A. [Louisiana State Univ., Baton Rouge, LA (United States); Kowalski, Karol [Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Atmospheric Science and Global Change Div. (ASGC); Wang, Xue B. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-12-14

    The photophysics of Green Fluorescent Protein (GFP) chromophore is critically dependent on its local structure and on its environment. Despite extensive experimental and computational studies, there remain many open questions regarding the key fundamental variables that govern this process. One outstanding problem is the role of autoionization as a possible relaxation pathway of the excited state under different environmental conditions. This issue is considered in our work through combined experimental and theoretical studies of microsolvated clusters of the deprotonated p-hydroxybenzylidene-2,3-dimethylimidazolinone anion (HBDI⁻), an analog of GFP chromophore. Through selective generation of microsolvated structures of predetermined size and subsequent analysis of experimental photoelectron spectra by high level ab-initio methods we are able to precisely identify the structure of the system, establish the accuracy of theoretical data, and provide reliable description of auto-ionization process as a function of hydrogen-bonding environment. Our study clearly illustrates the first few water molecules progressively stabilize the excited state of the chromophore anion against the autodetached neutral state, which should be an important trait for crystallographic water molecules in GFPs that has not been fully explored to date.

  19. Electron capture and transfer-ionization processes in 4He2++Ar collision at 12.5 keV amu-1

    International Nuclear Information System (INIS)

    Electron emission in the 4He2++Ar collisional system has been investigated at 35 deg. and 12.5 keV amu-1 collision velocity, in coincidence with the recoil target ion charges. Direct single ionization is found to be negligible with respect to single-electron capture. Contributions of transfer-ionization processes are stressed in the production of Ar2+ to Ar4+ ions; those of direct ionization, double excitation of the target and double capture into autoionization states of helium are instead found to be much less probable. Among the two-electron processes which explain the formation of Ar2+ ions, the double capture into autoionizing states of helium remains unimportant with respect to a pure transfer ionization process (one captured electron plus one ionized electron). The measured predominant production of Ar3+ ions illustrates the role played by three-electron processes, mainly a two-electron transfer accompanied by a single-target ionization. Finally, the formation of Ar4+ ions is connected with more complex transfer ionization processes. A qualitative analysis of these results is made within the quasimolecular approach. (author). Letter-to-the-editor

  20. The photoionization of Fe7+ and Fe8+ in the 2p-3d resonance energy region

    International Nuclear Information System (INIS)

    The photoionization cross sections of the levels belonging to the ground configuration [Ne]3s23p63d of Fe7+ and [Ne]3s23p6 of Fe8+ have been investigated using the fully relativistic R-matrix method in the 2p-3d excitation region. The detailed resonance structures are described and analysed in some detail with the resonance positions, widths and oscillator strengths being determined. To identify the resonances, the transition energies and oscillator strengths are calculated by the multi-configuration Dirac-Fock method implemented by the GRASP code as well. The cross sections have also been obtained using the non-relativistic R-matrix calculations. The resonances in the relativistic calculation span a much broader energy region than the non-relativistic result. For an iron plasma at a temperature of 20 eV and a density of 0.004 g cm-3, which is a typical experimental condition recently carried out by Chenais-Popovics et al (2000 Astrophys. J. Suppl. Ser. 127 275), the autoionization widths of the 2p-3d resonances are much larger than the widths caused by the radiative lifetime and electron impact broadening, while the Doppler widths are smaller than but rather close to the autoionization widths

  1. Analysis of Mg spectral features produced by irradiations of laser pulses with different contrast and pulse durations

    International Nuclear Information System (INIS)

    Experiments performed at the Leopard Laser Facility at the Nevada Terawatt Facility of the University of Nevada, Reno have produced K-shell Mg spectra with complex satellite features. K-shell Mg spectra were collected from experiments comprised of three different conditions related to laser pulse and contrast. Two spectrometers were fielded: a survey convex spectrometer with a potassium hydrogen phthalate (KAP) crystal (R ∼ 300) and a high resolution focusing spectrometer with spatial resolution using a spherically bent mica crystal (R ∼ 3000). These spectra included dielectronic satellite (DS) lines that were investigated using the quasi-relativistic many-body perturbation theory (MZ) code for previously identified transitions from autoionizing 2lnl′ states in He-like Mg and new transitions involving autoionizing 1s3lnl′ states in Li-like Mg and 1s3l3l′3l″ in Be-like Mg calculated using the Hartree–Fock-relativistic method (COWAN code). Radiative and non-radiative data are combined to obtain branching ratios, intensities and effective emission rate coefficients of DS lines. Synthetic spectra were matched to experimental data to identify strong satellite structures to the Heβ (7.8507 Å) and Lyα (8.4192 Å) resonance transitions. (paper)

  2. Dielectronic recombination of Ni-like ions through the 3d94ln'l' (n'=4,5) Cu-like configurations

    International Nuclear Information System (INIS)

    Ab initio calculations of the rate coefficients for dielectronic recombination (DR) of ten ions along the Ni I isoelectronic sequence in the ground state (Mo14+, Ag19+, Xe26+, Pr31+, Gd36+, Dy38+, Ta45+, Au51+, At57+, and U64+) through the Cu-like 3d94ln'l' (n'=4,5) inner-shell excited configurations were performed using the HULLAC code package. Resonant and nonresonant radiative stabilizing transitions and decays to autoionizing levels followed by radiative cascades are included. Collisional transitions following electron capture are neglected. Nonresonant stabilizing transitions are found to enhance the DR rates, and may even dominate the process at low electron temperature. The remarkable difference between the isoelectronic trend of the rate coefficients for DR through 3d94l4l' and through 3d94l5l' is emphasized. The trend of DR through 3d94l4l' shows irregularities at relatively low temperature due to the progressive closing of DR channels as Z increases. Thus, the DR coefficients cannot be reproduced or interpolated by a simple analytical formula. Even for the smooth contributions of the 3d94l5l' configurations, a simplified model using configuration averaging for autoionization and radiative decays instead of level-by-level detailed computations is found to overestimate the DR rates by a factor of up to 2

  3. Valence-shell single photoionization of Chlorine-like K$^{2+}$ ions: Experiment and Theory

    CERN Document Server

    Alna'Washi, G A; Habibi, M; Esteves-Macaluso, D; Wang, J C; Phaneuf, R A; Kilcoyne, A L D; Cisneros, C; McLaughlin, B M

    2014-01-01

    The absolute single photoionization cross-section was measured for Cl-like K$^{2+}$ over the photon energy range from 44.2 - 69.7 eV at a constant energy resolution of 0.045 eV. The experiments were performed by merging an ion beam with a beam of synchrotron radiation from an undulator. The ground-state ionization threshold was measured at 0.004 eV energy resolution to be 45.717 $\\pm$ 0.030 eV. The measurements are rich in resonance structure due to multiple Rydberg series of transitions to autoionizing states. These series are assigned spectroscopically using the quantum defect method, guided by pseudo-relativistic Hartree-Fock calculations for the energies and oscillator strengths of transitions to autoionizing states. The experimental results, which include significant contributions from K$^{2+}$ ions initially in metastable states, are in satisfactory agreement with a linear superposition of semi-relativistic R-matrix calculations of photoionization cross sections from these initial states.

  4. Two-photon finite-pulse model for resonant transitions in attosecond experiments

    Science.gov (United States)

    Jiménez-Galán, Álvaro; Martín, Fernando; Argenti, Luca

    2016-02-01

    We present an analytical model capable of describing two-photon ionization of atoms with attosecond pulses in the presence of intermediate and final isolated autoionizing states. The model is based on the finite-pulse formulation of second-order time-dependent perturbation theory. It approximates the intermediate and final states with Fano's theory for resonant continua, and it depends on a small set of atomic parameters that can either be obtained from separate ab initio calculations or be extracted from a few selected experiments. We use the model to compute the two-photon resonant photoelectron spectrum of helium below the N =2 threshold for the RABITT (reconstruction of attosecond beating by interference of two-photon transitions) pump-probe scheme, in which an XUV attosecond pulse train is used in association with a weak IR probe, obtaining results in quantitative agreement with those from accurate ab initio simulations. In particular, we show that (i) the use of finite pulses results in a homogeneous redshift of the RABITT beating frequency, as well as a resonant modulation of the beating frequency in proximity to intermediate autoionizing states; (ii) the phase of resonant two-photon amplitudes generally experiences a continuous excursion as a function of the intermediate detuning, with either zero or 2 π overall variation.

  5. High lying energy positions of doubly (2pns) {sup 1,3}P{sup o} and (2pnd) {sup 1,3}P{sup o} excited states of the beryllium atom

    Energy Technology Data Exchange (ETDEWEB)

    Sakho, I., E-mail: aminafatima_sakho@yahoo.fr [UFR Sciences and Technologies, Department of physics, University of Ziguinchor, Ziguinchor (Senegal)

    2011-12-15

    The Screening Constant by Unit Nuclear Charge (SCUNC) method is used to study (2pns) {sup 1,3}P{sup o} and (2pnd) {sup 1,3}P{sup o} autoionizing states of the beryllium atom. Energy positions are reported up to n=20. In addition, resonance widths of the (2pns) {sup 1}P{sup o} states also presented. The current results compared very well to available theoretical and experimental literature values up to n=15. The accurate data presented in this work may be of interest for future experimental and theoretical studies in the photoabsorption spectrum of Be. - Highlights: > Accurate energy positions of (2pns) {sup 1,3}P{sup o} and (2pnd) {sup 1,3}P{sup o} (n=3-20) autoionizing states of Be atoms. > Currently results compared very well to theoretical and experimental literature values up to n=15. > Presently data may be of interest for future experimental and theoretical studies in the photoabsorption spectrum of Be.

  6. Time-dependent reduced density matrix functional theory applied to laser-driven, correlated two-electron dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Brics, Martins; Kapoor, Varun; Bauer, Dieter [Institut fuer Physik, Universitaet Rostock, 18051 Rostock (Germany)

    2013-07-01

    Time-dependent density functional theory (TDDFT) with known and practicable exchange-correlation potentials does not capture highly correlated electron dynamics such as single-photon double ionization, autoionization, or nonsequential ionization. Time-dependent reduced density matrix functional theory (TDRDMFT) may remedy these problems. The key ingredients in TDRDMFT are the natural orbitals (NOs), i.e., the eigenfunctions of the one-body reduced density matrix (1-RDM), and the occupation numbers (OCs), i.e., the respective eigenvalues. The two-body reduced density matrix (2-RDM) is then expanded in NOs, and equations of motion for the NOs can be derived. If the expansion coefficients of the 2-RDM were known exactly, the problem at hand would be solved. In practice, approximations have to be made. We study the prospects of TDRDMFT following a top-down approach. We solve the exact two-electron time-dependent Schroedinger equation for a model Helium atom in intense laser fields in order to study highly correlated phenomena such as the population of autoionizing states or single-photon double ionization. From the exact wave function we calculate the exact NOs, OCs, the exact expansion coefficients of the 2-RDM, and the exact potentials in the equations of motion. In that way we can identify how many NOs and which level of approximations are necessary to capture such phenomena.

  7. Photoionization studies with molecular beams

    International Nuclear Information System (INIS)

    A molecular beam photoionization apparatus which combines the advantages of both the molecular beam method with photoionization mass spectrometry has been designed and constructed for carrying out some unique photoionization experiments. Rotational cooling during the supersonic expansion has resulted in high resolution photoionization efficiency curves for NO, ICl, C2H2 and CH3I. The analysis of these spectra has yielded ionization potentials for these molecules to an accuracy of +- 3 MeV. Detailed autoionization structures were also resolved. This allows the investigation of the selection rules for autoionization, and the identification of the Rydberg series which converge to the excited states of the molecular ions. The degree of relaxation for thermally populated excited states has been examined using NO and ICl as examples. As a result of adiabatic cooling, a small percentage of dimers is also formed during the expansion. The photoionization efficiency curves for (NO)2, ArICl, Ar2, Kr2 and Xe2 have been obtained near the thresholds. Using the known dissociation energies of the (NO)2, Ar2, Kr2 and Xe2 van der Waals molecules, the corresponding dissociation energies for NO-NO+, Ar2+, Kr2+, and Xe2+ have been determined. The ionization mechanisms for this class of molecules are examined and discussed

  8. Isoelectronic behavior of resonant and intercombination lines in MgI-like ions

    International Nuclear Information System (INIS)

    Radiative transitions with very different characteristic rates can serve as important diagnostics of local conditions in a plasma. Here, the observed intensity ratio of the 3s21S0 - 3s3p 1P1 to the 3s21S0 - 3s3p 3P1 transitions in MgI-like ions has always presented those who model plasma spectra with a challenge; the observed intensity of the intercombination line is always several times greater than what simple models predict. The authors offer a model that takes into account the contribution to the MgI-like emission features from autoionizing levels of the adjacent AlI-like charge state. Models in the present work, which include the effects of configuration interaction on ionic wavefunctions, and the contribution of both direct, impact ionization and autoionization channels from the AlI-like ion to the MgI-like ion, give good agreement with the observed resonant/intercombination (R/I) emission ratio only when a departure from ionization equilibrium is assumed. The authors also identify, for the first time, intercombination lines of the form 3s3p 1P1 - 3p23P2 in several elements relevant to both astrophysical and magnetically-confined fusion plasmas

  9. Electron impact single and double ionization of Niq+ ions (q = 10, 11, 13 and 15)

    International Nuclear Information System (INIS)

    Absolute cross sections for electron impact single and double ionization of Niq+ ions (q=10, 11, 13 and 15) have been measured for energies from threshold to about 5 keV. Experimental results for Ni11+, Ni13+ and Ni15+ are in good agreement with the calculations of Pindzola et al, obtained in the average configuration distorted-wave approximation for the 3s23pn (n=5, 3 and 1) ground configurations, respectively. The Ni10+ results show a significant ionization signal below the ground state [Ne]3s23p6 threshold due to ions formed in the metastable configuration [Ne]3s23p53d in the parent ion beam. The theoretical calculations including direct ionization and excitation-autoionization from both the ground and the excited configurations underestimated the cross section. The difference is probably due solely to the 3s → nl excitations. In this isonuclear sequence, the whole results shows that ions with an odd number of electrons behave differently from ions with an even number. Our measurements show clearly that double ionization is dominated by L-shell ionization followed by autoionization. (orig.)

  10. Valence-shell photoionization of chlorinelike Ar+ ions

    International Nuclear Information System (INIS)

    Absolute cross-section measurements for valence-shell photoionization of Ar+ ions are reported for photon energies ranging from 27.4 to 60.0 eV. The data, taken by merging beams of ions and synchrotron radiation at a photon energy resolution of 10 meV, indicate that the primary ion beam was a statistically weighted mixture of the 2P3/2o ground state and the 2P1/2o metastable state of Ar+. Photoionization of this Cl-like ion is characterized by multiple Rydberg series of autoionizing resonances superimposed on a direct photoionization continuum. Observed resonance line shapes indicate interference between indirect and direct photoionization channels. Resonance features are spectroscopically assigned and their energies and quantum defects are tabulated. The measurements are satisfactorily reproduced by theoretical calculations based on an intermediate coupling semirelativistic Breit-Pauli approximation.

  11. The role of multiple electron capture in the x-ray emission process following charge exchange collisions with neutral targets

    International Nuclear Information System (INIS)

    In this work we theoretically study photonic spectra that follow charge exchange processes between highly charged ions and neutral argon and CO targets. The range of collision energies studied is 5 eV/amu-10 keV/amu, covering typical EBIT-traps and Solar Wind energies. Our studies are based on multiple electrons schemes within the classical trajectory Monte Carlo method. Electrons are sorted with the sequential binding energies for the target under consideration. The role played by the multiple electron capture process for the different collision systems under consideration is explicitly analyzed and its contribution separated as arising from double radiative decay and autoionizing multiple capture. Present studies are stimulated by the upcoming launch of the Astro-H mission in 2015, which will provide high resolution spectra in the 0.3 keV-12keV band

  12. Non local thermodynamic equilibrium self-consistent average atom model for plasma physics

    International Nuclear Information System (INIS)

    A time-dependent collisional-radiative average-atom model is presented to study statistical properties of highly-charged ion plasmas in off-equilibrium conditions. Atomic structure is described either with a screened-hydrogenic model including l-splitting, or by calculating one electron states in a self-consistent average-atom potential. Collisional and radiative excitation/deexcitation and ionization/recombination rats, as well as auto-ionization and dielectronic recombination rates, are formulated within the average-configuration framework. A good agreement with experiment is found for the charge-state distribution of a gold plasma at electron and density temperature equal to 6 x 1020 cm-3 and 2200 eV. (author)

  13. Atomic physics of strongly correlated systems

    International Nuclear Information System (INIS)

    This report presents the progress made in our continuing study of strongly correlated atomic systems within the last year. We have examined the shape of three-body systems in hyperspherical coordinates by studying the evolution of the density functions with the mass ratio of the particles in the system. We have calculated the ejected electron spectra from the autoionizing states formed in double capture processes in collisions of multiply charged ions with atoms. We have investigated the systematics and the propensity rules of radiative and Auger decay rates of high-lying doubly excited states. We have also studied ion-atom collisions for processes which pose great challenges to detailed theories, by looking into processes where the cross sections are small such as the excitation process in He++ + H collisions, or by looking into fine details such as the orientation parameters in excitation and charge transfer processes

  14. Study of the population inversion mechanisms and superradiance on ion transitions of molecular nitrogen in the filament

    Science.gov (United States)

    Ivanov, N. G.; Losev, V. F.; Prokop'ev, V. E.

    2015-12-01

    The experimental results of the inversion population mechanisms study in the resonant electronic transition B3Πg-A3Σu+ of nitrogen ions by optically pumped of air and pure nitrogen by femtosecond laser pulse at a wavelength of 950 nm are presented. It is shown that the inversion results from selective settling of N2+(B2Σu+, v' =0) excited state by multiphoton excitation of the autoionization states of the nitrogen molecule with energy of 18.7 eV. Seed photon for superradiance at transitions of molecular nitrogen ions are photons the axial supercontinuum occurring in the filament on the respective wavelengths. The mode of the superradiance at a wavelength λ = 358.4 nm referred to the transition of the CN molecules was realized.

  15. One- and two-electron numerical models of multiphoton ionization of helium

    International Nuclear Information System (INIS)

    We discuss the calculation of ionization rates of helium using time-dependent solutions of the full-dimensional Schroedinger equation in conjunction with time-dependent solutions of a single active electron (SAE) model of helium. The SAE model is a one-electron atom with a non-Coulombic effective potential that can be tuned in certain limits to give near quantitative agreement with the results of the full-dimensional integration. We show how the tuned SAE model can be used to improve the accuracy and reliability of the calculations of ionization cross sections. In addition we consider a case in which failure of the SAE model can be attributed to strong correlation effects in laser-driven helium, specifically interaction with an intermediate doubly excited (autoionizing) state of helium. (author)

  16. The solution and the study of the coupled rate equations in high temperature and high density plasmas

    International Nuclear Information System (INIS)

    Numerous and stiff coupled rate equations describing ionic charge-state distribution and the level populations is solved rapidly by using quasi-static state approximation. The physical meaning of the matrices (E**m)-1 and Tg defined in the paper is discussed and was used to given ideas on ionic charge-state distribution and the level populations. The Ne/Te objective region for 3d5/2-2P3/2 transitions in H-like C recombination X-ray lasers is obtained. The conclusion that ion abundance υs electron density at an electron temperature may have two peaks is derived. Z-scaling law is also obtained. Finally, the effect of auto-ionization and dielectronic capture process and whether the ionic charge-state distribution fits the binomial distribution are inspected

  17. Production of excited atomic hydrogen and deuterium from H{sub 2} and D{sub 2} photodissociation

    Energy Technology Data Exchange (ETDEWEB)

    Bozek, J D [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Furst, J E [University of Newcastle-Ourimbah, Ourimbah, NSW 2258 (Australia); Gay, T J [Behlen Laboratory of Physics, University of Nebraska, Lincoln, NE 68588-0111 (United States); Gould, H [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Kilcoyne, A L D [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Machacek, J R [Behlen Laboratory of Physics, University of Nebraska, Lincoln, NE 68588-0111 (United States); MartIn, F [Departamento de Quimica, Universidad Autonoma de Madrid, 28049 Madrid (Spain); McLaughlin, K W [Department of Physics and Engineering, Loras College, Dubuque, IA 52001 (United States); Sanz-Vicario, J L [Departamento de Quimica, Universidad Autonoma de Madrid, 28049 Madrid (Spain)

    2006-12-14

    We have measured the production of both Ly{alpha} and H{alpha} fluorescence from atomic H and D for the photodissociation of H{sub 2} and D{sub 2} by linearly polarized photons with energies between 24 and 60 eV. In this energy range, excited photofragments result primarily from the production of doubly excited molecular species which promptly autoionize or dissociate into two neutrals. Our data are compared with ab initio calculations of the dissociation process, in which both doubly excited state production and prompt ionization (non-resonant) channels are considered. Agreement between our experimental data and that of earlier work, and with our theoretical calculations, is qualitative at best.

  18. Double ionization of Ne5+ and Ne6+ ions by electron impact

    International Nuclear Information System (INIS)

    Theoretical studies of electron impact double ionization cross sections of Ne5+ and Ne6+ ions have been performed in the binary encounter approximation (BEA). Direct double ionization (DDI) has been investigated in the modified double binary encounter model. The K-shell ionization cross sections have been also calculated in the BEA to take into account the contributions to double ionization from the ionization-autoionization (IA) process. The effect of the Coulombic field of the target ion on the incident electron has been considered in the present work. Accurate expression of σΔE (cross section for energy transfer ΔE) and the Hartree-Fock (HF) velocity distributions for the target electrons have been used throughout the calculations. The present results are in overall moderate agreement with the experimental observations. Possible reasons behind the discrepancies between the theory and the experiment have been discussed. (authors)

  19. Atomic and molecular complex resonances from real eigenvalues using standard (hermitian) electronic structure calculations

    CERN Document Server

    Landau, Arie; Kaprálová-Žďánská, Petra Ruth; Moiseyev, Nimrod

    2015-01-01

    Complex eigenvalues, resonances, play an important role in large variety of fields in physics and chemistry. For example, in cold molecular collision experiments and electron scattering experiments, autoionizing and pre-dissociative metastable resonances are generated. However, the computation of complex resonance eigenvalues is difficult, since it requires severe modifications of standard electronic structure codes and methods. Here we show how resonance eigenvalues, positions and widths, can be calculated using the standard, widely used, electronic-structure packages. Our method enables the calculations of the complex resonance eigenvalues by using analytical continuation procedures (such as Pad\\'{e}). The key point in our approach is the existence of narrow analytical passages from the real axis to the complex energy plane. In fact, the existence of these analytical passages relies on using finite basis sets. These passages become narrower as the basis set becomes more complete, whereas in the exact limit,...

  20. The standard map: From Boltzmann-Gibbs statistics to Tsallis statistics

    Science.gov (United States)

    Tirnakli, Ugur; Borges, Ernesto P.

    2016-03-01

    As well known, Boltzmann-Gibbs statistics is the correct way of thermostatistically approaching ergodic systems. On the other hand, nontrivial ergodicity breakdown and strong correlations typically drag the system into out-of-equilibrium states where Boltzmann-Gibbs statistics fails. For a wide class of such systems, it has been shown in recent years that the correct approach is to use Tsallis statistics instead. Here we show how the dynamics of the paradigmatic conservative (area-preserving) stan-dard map exhibits, in an exceptionally clear manner, the crossing from one statistics to the other. Our results unambiguously illustrate the domains of validity of both Boltzmann-Gibbs and Tsallis statistical distributions. Since various important physical systems from particle confinement in magnetic traps to autoionization of molecular Rydberg states, through particle dynamics in accelerators and comet dynamics, can be reduced to the standard map, our results are expected to enlighten and enable an improved interpretation of diverse experimental and observational results.

  1. Theoretical electron-impact ionization of W17+ forming W18+

    International Nuclear Information System (INIS)

    We have calculated electron-impact ionization for ground state and excited states of W17+ using the flexible atomic code and level-to-level distorted-wave method. Particular attention has been paid to excitation-autoionization (EA) processes. The calculated EA cross section contributes to the total cross section as much as about 50%. Our calculated total cross sections have been compared with the recent experimental results (Rausch et al 2011 J. Phys. B: At. Mol. Opt. Phys. 44 165202). The total cross section for the ground state is a little smaller than the experimental results, but that for the excited states with ionization threshold near the starting energy of the measured cross sections is very close to the experimental results. Maxwellian rate coefficients derived from our calculated cross sections for the ground state are also compared with the previous configuration-average distorted-wave rate coefficients in detail. (paper)

  2. Electron-impact ionization for P-like ions forming Si-like ions

    International Nuclear Information System (INIS)

    We have calculated electron-impact ionization (EII) for initially P-like systems for ions with an even proton number Z from S+ to Zn15+. We used the flexible atomic code (FAC) which is based on a distorted-wave (DW) approximation. In our work, 3l → nl (n = 4 − 35) excitation-autoionization (EA) channels near the 3p direct ionization threshold and 2l → nl' (n = 3 – 10) EA channels at the higher energies are included, along with the detailed branching ratios. Our calculated EII cross sections are compared both with previous FAC calculations, which omitted many of these EA channels, and with the available experiments.

  3. Ground state photoionization of copper-like thulium

    International Nuclear Information System (INIS)

    The R-matrix method has been applied to photoionization of copper-like thulium from its 4s 2Se ground state. Configuration-interaction wavefunctions were used to describe the initial bound and final continuum states. Up to seven states of the final Tm41+ ion were included in the wavefunction expansion. Total photoionization cross sections were calculated for a wide range of photon energies from the ionization threshold up to 350 Ryd. The background cross section increases thirtyfold as the 3De threshold is crossed. At low energies the cross section is dominated by several series of autoionizing resonances, which we have analysed in some detail. We have also calculated oscillator strengths for some transitions between the bound states of the Tm40+ ion. The calculations were performed in LS coupling. (author)

  4. Ultra-low kinetic energy photoelectron angular distribution measurements in He and Ne using a Velocity Map Imaging spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Juarez, A M; Hoyos-Campo, L M [Institute de Ciencias Fisicas, Universidad Nacional Autonoma de Mexico, Cuernavaca, Mor. 62210 (Mexico); Redt, E; Hoenert, M; Aguilar, A [Lawrence Berkeley National Laboratory, Berkeley CA-94720 (United States); Rolles, D [Max Planck Advanced Study Group, CFEL, D-22761 Hamburg (Germany); Berrah, N, E-mail: aaguilar@lbl.go [Department of Physics, Western Michigan University, Kalamazoo MI-49008 (United States)

    2009-11-01

    We present photoelectron angular distributions (PADs) in Helium and Neon for electrons with excess energies between 5 and 100 meV. These ultra-low kinetic energy PAD measurements were obtained with a modified Velocity Map Imaging spectrometer (VMI) and VUV light from the Advanced Light Source (ALS) synchrotron radiation source. The efficiency and reliability of the spectrometer at this ultra-low kinetic energy range has been tested by determining the variation with energy of the asymmetry, {beta}, parameter of photoelectrons from the s-shell direct ionization in Helium. For Neon, we determined the energy dependent asymmetry parameters across the 's' and 'd' autoionizing resonances between the P{sub 3/2} and P{sub 1/2} ionic states. Furthermore, we measured the asymmetry parameter for photoelectrons produced from the n = 2 to n = 6 satellite states of He. These measurements were performed at values of excess kinetic energy previously unexplored.

  5. Ultra-low kinetic energy photoelectron angular distribution measurements in He and Ne using a Velocity Map Imaging spectrometer

    International Nuclear Information System (INIS)

    We present photoelectron angular distributions (PADs) in Helium and Neon for electrons with excess energies between 5 and 100 meV. These ultra-low kinetic energy PAD measurements were obtained with a modified Velocity Map Imaging spectrometer (VMI) and VUV light from the Advanced Light Source (ALS) synchrotron radiation source. The efficiency and reliability of the spectrometer at this ultra-low kinetic energy range has been tested by determining the variation with energy of the asymmetry, β, parameter of photoelectrons from the s-shell direct ionization in Helium. For Neon, we determined the energy dependent asymmetry parameters across the 's' and 'd' autoionizing resonances between the P3/2 and P1/2 ionic states. Furthermore, we measured the asymmetry parameter for photoelectrons produced from the n = 2 to n = 6 satellite states of He. These measurements were performed at values of excess kinetic energy previously unexplored.

  6. Effect of laser beam non-uniformity and the AC stark shift on the two-photon resonant three-photon ionization process of the cesium atom

    International Nuclear Information System (INIS)

    The Ac Stark effect and the effect of laser beam non-uniformity on the two-photon resonant three-photon ionization spectrum of cesium is investigated. The non-uniformity due to the temporal and the spatial variations of the pumping laser makes the ionization spectrum non-symmetric and shifts the peak frequency of the excited-state population from the peak frequency of the ionization yield. The order of the non-linearity of the ionization process is also studied near resonances, and it is found that the minimum of the curve is close to the peak frequency of the excited-state spectrum. Ways of applying these results to studies of autoionizing states are suggested

  7. Scheme for multistep resonance photoionization of atoms

    Science.gov (United States)

    Liu, Bo; Ning, Xi-Jing

    2001-07-01

    Traditional schemes for multistep resonance photoionization of atoms let every employed laser beam interact with the atoms simultaneously. In such a situation, analyses via time-dependent Schrödinger equation show that high ionization probability requires all the laser beams must be intense enough. In order to decrease laser intensity, we proposed a scheme that the laser beam used to pump the excited atoms (in a higher bound state) into an autoionization state does not interact with the atoms until all the population is transferred by the other lasers from a ground state to the bound state. As an interesting example, we examined three-step photoionization of 235U with our scheme, showing that the intensity of two laser beams can be lowered by two orders of magnitude without losing high ionization probability.

  8. Resonance ionization mass spectroscopy with neptunium and plutonium

    International Nuclear Information System (INIS)

    The resonance ionization mass spectroscopy was one of the methods used for detection of the actinides. The principles of the method are: atoms of the elements to be measured are excited step by step through resonant irradiation with laser light, and are thus ionized. The ions are accelerated by electrical fields and can then be detected. The equipment for this process comprised a pulsed laser system consisting of two copper vapor lasers and three dye lasers, and a linear time-of-flight mass spectrometer with a mass resolution M/ΔM of approx. 1500. Due to a two-step resonant excitation of atomic energy levels and subsequent population of an autoionized state, the three-step ionization method is particularly element-selective. Use of powerful lasers with a high pulse repetition rate yield a high sensitivity and thus allow low detection limits. (orig./BBR)

  9. Study of short-lived tin isotopes with a laser ion source

    International Nuclear Information System (INIS)

    A chemically selective laser ion source based on resonance ionization of atoms in a hot cavity was applied for study of short-lived tin isotopes at the heavy ion accelerator UNILAC/GSI. Tin atoms were ionized by a three-step resonance laser excitation of an autoionizing state. Yields of fusion-produced 108Sn and 108In isotopes were compared with the plasma ion source FEBIAD-B3. The total efficiency of tin ionization was determined to be 8.5%, whilst the indium isobar ionization was suppressed by a factor of 12. An experimental run on study of decay properties of extremely neutron deficient isotopes 101-103Sn has been carried out

  10. Laser resonance ionization mass spectrometry as a sensitive analytical method for actinides and technetium

    International Nuclear Information System (INIS)

    Laser resonance ionization mass spectrometry has been investigated as a method for the determination of trace amounts of actinides and technetium. A high sensitivity and selectivity have been achieved by three-step photoionization of the elements in the atomic state followed by time-of-flight measurement for mass analysis. The system for photoionization consists of three dye lasers which are pumped simultaneously by a copper vapour laser of 30 W average power at a pulse repetition rate of 6.5 KHz. The time-of-flight spectrometer has a mass resolution better than 2500. By ionization via autoionization states and by saturation in each excitation step a detection limit of less than 108 atoms of actinides or of technetium in the sample can be reached. (author)

  11. Development of an Ionization Scheme for Gold using the Selective Laser Ion Source at the On-Line Isotope Separator ISOLDE

    CERN Document Server

    Fedosseev, V; Marsh, B A; CERN. Geneva. AB Department

    2006-01-01

    At the ISOLDE on-line isotope separation facility, the resonance ionization laser ion source (RILIS) can be used to ionize reaction products as they effuse from the target. The RILIS process of laser step-wise resonance ionization of atoms in a hot metal cavity provides a highly element selective stage in the preparation of the radioactive ion beam. As a result, the ISOLDE mass separators can provide beams of a chosen isotope with greatly reduced isobaric contamination. The number of elements available at RILIS has been extended to 26, with the addition of a new three-step ionization scheme for gold. The optimal ionization scheme was determined during an extensive study of the atomic energy levels and auto-ionizing states of gold, carried out by means of in-source resonance ionization spectroscopy. Details of the ionization scheme and a summary of the spectroscopy study are presented.

  12. Electron impact ionization and excitation of laser-excited atoms: investigation by means of electron spectrometry

    International Nuclear Information System (INIS)

    We have measured the electron spectra following the excitation and ionization of laser-excited atoms by impact of 1.5 keV electrons: 2p excitation and 2s ionization of Na(3p3/2), 1s excitation of Li(2p3/2) and 5p ionization of Ba(6s5d 1,3D). Except for Ba the intensities of ejected electrons are directly proportional to the cross sections of Auger and autoionizing states. Theoretical excitation cross sections (Na 2p, Li 1s) are obtained in first Born approximation including the full relaxation of the atomic electrons. Relative ionization cross sections (Na 2s, Ba 5p) are evaluated in sudden approximation as a two-step process: pure 2s(5p) ionization plus relaxation of the rest of the atomic electrons. The experimental spectra are compared to theoretical spectra

  13. Ionization potential of neutral atomic plutonium determined by laser spectroscopy

    International Nuclear Information System (INIS)

    The ionization potential of the neutral plutonium atom, Pu i, has been determined by two- and three-step resonance photoionization observation of the threshold of ionization and of the Rydberg series. The Rydberg series were observed by field ionization as series that converge to the first ionization limit and as autoionizing series the converge to the second and to several higher convergence limits. The threshold and Rydberg series were obtained through a number of two- and three-step pathways. The photoionization threshold value for the 239Pu i ionization potential is 48 582(30) cm-1, and the more accurate value from the Rydberg series is 48 604(1) cm-1 or 6.0262(1) eV

  14. Laser ion source tests at the HRIBF on stable Sn, Ge and Ni isotopes

    International Nuclear Information System (INIS)

    As one step in the ion source development for the Rare Isotope Accelerator, a hot-cavity laser ion source using an all-solid-state titanium-sapphire laser system has been tested at the Holifield Radioactive Ion Beam Facility. Resonance ionization of stable isotopes of Sn, Ge and Ni has been studied in a Ta hot cavity. Efficient three step resonant ionization schemes applying frequency tripling for the first excitation step and using auto-ionizing or atomic Rydberg states in the ionizing step have been identified for all three elements, resulting in laser ion beams of typically around 100 nA. By saturating most of the optical excitation steps involved, ionization efficiencies of 22%, 3.3% and 2.7% have been measured for Sn, Ge and Ni, respectively

  15. Effects of the properties of excitation laser pulses on selective photoionization of ^168Yb

    Science.gov (United States)

    Kwon, Duck-Hee; Park, Hyunmin; Han, Jaemin; Rhee, Yongjoo

    2002-05-01

    We have investigated selective photoionization of ^168Yb in the well-known three-color, three-step, three-photon ionization scheme which consists of coherent excitations between the bound levels and of incoherent excitation between the third level and the autoionization state. The incoherent line broadening and Doppler broadening are considered in the interaction of the atomic system with laser pulses, and we pay attention to the effects of the power, the spectral shape, and the time delay of the excitation lasers on the selectivity and population dynamics of ^168Yb. We numerically observe that the selectivity of ^168Yb is decreased with the increase of the power of the lasers, which is in good agreement with an experimental result.

  16. Ultrasensitive detection of actinides and technetium by laser resonance ionization mass spectrometry

    International Nuclear Information System (INIS)

    The application of laser resonance ionization mass spectrometry for the detection of extremely small numbers of atoms has been explored in the very recent years. High sensitivity and unambiguity in element and isotope identification can be achieved by three-step photoionization of the elements in the atomic state followed by time-of-flight mass analysis. The laser system for photoionization consists of three dye lasers which are pumped simultaneously by a copper vapor laser. For mass determination a time-of-flight spectrometer with a mass resolution better than 1500 is used. By ionization via autoionizing states and by saturation in each excitation step a detection limit of about 107 atoms of actinides or of technetium in the sample has been obtained

  17. Detection and speciation of trace amounts of neptunium and plutonium

    International Nuclear Information System (INIS)

    Laser resonance ionization mass spectrometry has been applied for the detection of trace amounts of neptunium and plutonium. High sensitivity and selectivity can be achieved by three-step-photoionization followed by time-of-flight mass analysis. The detection system consists of three tunable dye lasers, pumped by one or two copper vapor lasers and a time-of-flight spectrometer. By ionization of the excited atoms via autoionizing states and by complete saturation of each excitation step a detection limit of about 107 atoms of actinides has been obtained. Measurements of the isotopic ratios of plutonium samples yielded a good agreement with mass spectrometric data. The combination of resonance ionization mass spectrometry with chemical procedures enables the speciation of neptunium and plutonium ions at very low concentrations

  18. Separation and detection of trace amounts of technetium

    International Nuclear Information System (INIS)

    A chemical procedure for the separation of technetium from environmental samples is presented. Laser resonance ionization mass spectrometry is used for the detection of trace amounts of technetium. The detection system consists of three tunable dye lasers, pumped by one or two pulsed copper vapour lasers, and of a time-of-flight spectrometer. By ionization of the excited atoms via autoionizing states in the three-step photoionization process an overall efficiency of 2x10-6 was determined for 99gTc corresponding to a detection limit of 107 atoms. The three-step photoionization in combination with time-of-flight measurements guarantees an unambiguous element and isotope assignment. (orig.)

  19. Resonant photoemission from SmS(100)

    International Nuclear Information System (INIS)

    A strong, sharp resonance enhancement of 4f photoemission has been observed on SmS(100) surfaces for photon energies in the region of the 4d-4f transitions at about 126 eV. The discrete final state reached via the excitation hν + 4d104f6 → 4d94f7 autoionizes primarily via a super Coster-Kronig transition of the type 4d94f7 → 4d104f5 + unbound electron. Other decay channels, e.g. Sm 5p emission, as well as a surface induce binding energy shift in the Sm3+ final state are identified and discussed. (author)

  20. Partial ionization cross-sections of rubidium atom by electron impact

    International Nuclear Information System (INIS)

    The partial ionization cross-sections of the 5s, 4p6, 4s2, 3d10 shells of a rubidium atom are calculated by using the relativistic distorted-wave, Coulomb-Born and binary-encounter-dipole approximations for the incident electron energies from the threshold up to 600 eV. The comparative analysis of the data with the experimental autoionization cross-section and the total single ionization cross-section of a rubidium atom is performed. Each of the considered approximations reflects satisfactorily the direct ionization of rubidium atom only in the certain energy regions, namely, the distorted-wave approximation at low impact energies, and the binary-encounter-dipole approximation at high impact energies.

  1. Study of attosecond delays using perturbation diagrams and exterior complex scaling

    CERN Document Server

    Dahlström, J M

    2014-01-01

    We describe in detail how attosecond delays in laser-assisted photoionization can be computed using perturbation theory based on two-photon matrix elements. Special emphasis is laid on above-threshold ionization, where the electron interacts with an infrared field after photoionization by an extreme ultraviolet field. Correlation effects are introduced using diagrammatic many-body theory to the level of the random-phase approximation with exchange (RPAE). Our aim is to provide an ab initio route to correlated multi-photon processes that are required for an accurate description of experiments on the attosecond time scale. Here, our results are focused on photoionization of the M -shell of argon atoms, where experiments have been carried out using the so-called RABITT technique. An influence of autoionizing resonances in attosecond delay measurements is observed. Further, it is shown that the delay depends on both detection angle of the photoelectron and energy of the probe photon.

  2. Phase measurement of a Fano window resonance using tunable attosecond pulses

    CERN Document Server

    Kotur, M; Jimenez-Galan, A; Kroon, D; Larsen, E W; Louisy, M; Bengtsson, S; Miranda, M; Mauritsson, J; Arnold, C L; Canton, S E; Gisselbrecht, M; Carette, T; Dahlstrom, J M; Lindroth, E; Maquet, A; Argenti, L; Martin, F; L'Huillier, A

    2015-01-01

    We study the photoionization of argon atoms close to the 3s$^2$3p$^6$ $\\rightarrow$ 3s$^1$3p$^6$4p $\\leftrightarrow$ 3s$^2$3p$^5$ $\\varepsilon \\ell$, $\\ell$=s,d Fano window resonance. An interferometric technique using an attosecond pulse train, i.e. a frequency comb in the extreme ultraviolet range, and a weak infrared probe field allows us to study both amplitude and phase of the photoionization probability amplitude as a function of photon energy. A theoretical calculation of the ionization process accounting for several continuum channels and bandwidth effects reproduces well the experimental observations and shows that the phase variation of the resonant two-photon amplitude depends on the interaction between the channels involved in the autoionization process.

  3. Time delay in photoionization in Ne: Effect of different types of correlation

    Science.gov (United States)

    Mandal, Ankur; Saha, Soumyajit; Dutta, Narenda Nath; Ganesan, Aarthi; Deshmukh, P. C.; Dolmatov, V. K.; Kheifets, A. S.; Manson, S. T.

    2015-05-01

    Various effects on time delay in photoionization, such as many body correlations, relativity, Cooper minima, autoionizing resonances, etc.,. have been studied. Here we investigate the effects of correlation on time delay using relativistic randon phase approximation (RRPA), RRPA with relaxation (RRPA-R) muticonfiguration Tamm Dancoff (MCTD) (configuration interaction) and many-body perturbation theory (MBPT). Ne is chosen since it has been studied extensively. In an earlier study a truncated RRPA calculation on Ne showed an increase in time delay near the 2s threshold as compared to a nonrelativistic calculation. In the present work, a full RRPA calculation is studied to explore the interchannel coupling effects in the vicinity of the 1s threshold.

  4. Cross sections and excitation rates for electron collisions with heliumlike ions

    International Nuclear Information System (INIS)

    We describe the techniques and the approximations used in extensive calculations for cross sections and reaction-rate parameters for electron-impact excitation of a number of heliumlike ions. All transitions involving the ground state and the n=2 states are considered. Calculations are made in the distorted-wave approximation using configuration-interaction wave functions to represent the target states. Autoionizing resonances in the scattering cross sections are included through bound-channel correlation-type functions and through quantum-defect-theory analysis of the reactance matrices. The resonances are shown to make considerable contributions to the cross sections and thereby, in many cases, to enhance the excitation-rate coefficients by a significant factor. This should have important consequences for practical applications in the analysis of laboratory and astrophysical plasmas. The accuracy of our approximations is also discussed

  5. Low energy 4f-5d transitions in lanthanide doped CaLaSiN3 with low degree of cross-linking between SiN4 tetrahedra

    International Nuclear Information System (INIS)

    CaLaSiN3 samples doped with Eu, Yb, Sm, Ce and Pr have been prepared via solid-state reaction synthesis and the optical properties have been studied. Both Yb and Sm were only observed in the trivalent state due to the fact that their Ln2+ ground states are located inside or very close to the conduction band of the CaLaSiN3 host lattice. Doping with Ce3+ or Eu2+ resulted in a very low energy Ce3+ or Eu2+ 4f-5d absorption band around 1.9 eV (650 nm) and 1.4 eV (885 nm), respectively. The Ce3+ 5d-4f emission appeared to be quenched, just as the Eu2+ 5d-4f emission, which can be explained as the result of auto-ionization. (paper)

  6. Spectral modeling of Fe XVII pumped by a free-electron x-ray laser

    Science.gov (United States)

    Clementson, Joel

    2011-09-01

    The atomic structure and x-ray pumping of neonlike Fe xvii have been calculated and modeled under free-electron laser excitation conditions using the Flexible Atomic Code. Specifically, pumping of the (2p3/23s1/2)2,1, (2p1/23s1/2)1, (2p3/23d5/2)1, and (2p1/23d3/2)1 levels that connect with the ground state (2s22p6)0 by the so-called M2, 3G, 3F, 3D, and 3C transitions have been studied. In addition, the spectrum of sodiumlike Fe xvi has been modeled to account for possible line coincidences with the neonlike spectrum. The calculations include oscillator strengths, radiative transition probability rates, autoionization rates, non-resonant photoionization cross sections, and line emissivities.

  7. Recombination Lines of CII in the Spectra of Planetary Nebulae

    CERN Document Server

    Sochi, Taha

    2010-01-01

    The current report presents the work carried out by the author to investigate the recombination lines of CII in the spectra of planetary nebulae. Two CIII targets were prepared and used to generate theoretical data required in the investigation of recombination lines that arise from collisions between electrons and ions in thin plasma found in planetary nebulae and other astrophysical objects. One of these targets contains 9 atomic terms while the other contains 26 terms. For each one of these targets, theoretical data concerning bound and autoionizing states were generated in the intermediate coupling approximation by R-matrix and Autostructure codes and compared to experimental data. The comparison revealed very good agreement. These theoretical data were then used to generate emissivity data and compare it to the carbon recombination lines found in the observational line list of Zhang et al [2005] on the planetary nebula NGC 7027. The main tool used in this analysis is the `Emissivity' code which is a prog...

  8. Modulation of attosecond beating in resonant two-photon ionization

    CERN Document Server

    Galán, Álvaro J; Martín, Fernando

    2014-01-01

    We present a theoretical study of the photoelectron attosecond beating at the basis of RABBIT (Reconstruction of Attosecond Beating By Interference of Two-photon transitions) in the presence of autoionizing states. We show that, as a harmonic traverses a resonance, its sidebands exhibit a peaked phase shift as well as a modulation of the beating frequency itself. Furthermore, the beating between two resonant paths persists even when the pump and the probe pulses do not overlap, thus providing a sensitive non-holographic interferometric means to reconstruct coherent metastable wave packets. We characterize these phenomena quantitatively with a general finite-pulse analytical model that accounts for the effect of both intermediate and final resonances on two-photon processes, at a negligible computational cost. The model predictions are in excellent agreement with those of accurate ab initio calculations for the helium atom in the region of the N=2 doubly excited states.

  9. Photo association in metastable helium in the vicinity of the Bose-Einstein condensation and production of giant dimers; Photo-association de l'helium metastable au voisinage de la condensation de Bose-Einstein et formation de dimeres geants

    Energy Technology Data Exchange (ETDEWEB)

    Leonard, J

    2003-11-15

    In the vicinity of Bose-Einstein condensation, the collisional properties of a dilute gas of metastable helium (He{sub 2}{sup 3}S) are governed by the rate of ionizing Penning collisions and the s-wave scattering length. In order to investigate these properties, we have carried out new photo-association experiments in which a pair of free atoms absorbs a photon to produce a molecule in an excited electronic state. In particular, we have observed 'giant dimers' for which the autoionizing process is inhibited. Accurate spectra have been acquired by the use of an original 'calorimetric' detection scheme. In addition, we have calculated long-range electronic potentials for the 2{sup 3} S + 2{sup 3} P system. Our asymptotic approach is described in detail, which reproduces the measured binding energies of the giant dimers with very good accuracy. (author)

  10. Study of a high and low pressure plasma produced in a He-N2 mixture: application to spontaneous emissions by radiative collisions

    International Nuclear Information System (INIS)

    This thesis is centered on the study of the energy transfer from helium metastable atoms to ground state nitrogen molecules by the process of radiative collisions. Experimental techniques employed include the analysis of spontaneous emission from the reaction: He(23S)+N2(X,v=0) → He(11S)+(N2sup(R)(B,v'=4,5) → N2sup(R)(X,v'')+hω), where R indicates highly excited nitrogen Rydberg states. As the lower level Rydberg states are autoionizing, the net effect of the radiative collision is identical that of Penning ionization where the Rydberg to states are intermediates. The results of this study lend support to the validity of a radiative collision based laser amplifier model proposed in the thesis

  11. Coherent and incoherent processes in resonant photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Magnuson, M.; Karis, O.; Weinelt, M. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    In this contribution the authors present the distinction between coherent and incoherent processes in resonant photoemission. As a first step they determine whether an autoionization process is photoemission-like or Auger-like. The discussion is based on measurements for a weakly bonded adsorption system, Ar/Pt(111). This type of system is well adapted to investigate these effects since it yields distinctly shifted spectral features depending on the nature of the process. After this, the question of resonance photoemission in metallic systems is addressed. This is done in connection with measurements at the 2p edges for Ni metal. Ni has been one of the prototype systems for resonant photoemission. The resonances have been discussed in connection with the strong correlation and d-band localization effects in this system. Based on the results some general comments about the appearance of resonant effects in metallic systems are made.

  12. Computer simulation of cluster impact induced electronic excitation of solids

    International Nuclear Information System (INIS)

    We present a computational study of electronic excitation upon bombardment of a metal surface with cluster projectiles. Our model employs a molecular dynamics (MD) simulation to calculate the particle dynamics following the projectile impact. Kinetic excitation is implemented via two mechanisms describing the electronic energy loss of moving particles: autoionization in close binary collisions and a velocity proportional friction force resulting from direct atom–electron collisions. Two different friction models are compared with respect to the predicted sputter yields after single atom and cluster bombardment. We find that a density dependent friction coefficient leads to a significant reduction of the total energy transferred to the electronic sub-system as compared to the Lindhard friction model, thereby strongly enhancing the predicted sputter yield under cluster bombardment conditions. In contrast, the yield predicted for monoatomic projectile bombardment remains practically unchanged

  13. Population kinetics and M band emission spectra of gold plasmas in non-local thermodynamic equilibrium by using a detailed relativistic configuration approach

    International Nuclear Information System (INIS)

    A collisional-radiative model based on the approach of detailed relativistic configurations is developed, where the complete set of atomic data including photo-excitation, photoionization, electron impact excitation, electron impact ionization and autoionization is calculated, and the data of the inverse processes are obtained by detailed balance. The population distribution is obtained by solving the rate equation under the steady-state condition. The present model is applied to calculate the charge state distribution and M band emission spectra of gold plasmas in non-local thermodynamic equilibrium under a variety of plasma conditions. Comparisons between the present work and experimental results were made and good agreement is found. For the strong transition lines, the intensities predicted by the present model agree with those of experimental spectra within 50%. The present work is useful in analyzing and interpreting experiments as well as in diagnosing the electron temperature in experiments. (paper)

  14. Commissioning of a dedicated soft X-ray energy dispersive beamline for NEXAFS and other CFS/CIS studies

    Energy Technology Data Exchange (ETDEWEB)

    Batchelor, D.; Schmidt, T.; Schoell, A [Universitaet Wuerzburg, Experimentelle Physik II, Wuerzburg (Germany); Follath, R.; Jung, C. [BESSY GmbH, Berlin (Germany); Fink, R. [Physikalische Chemie II, Universitaet Erlangen-Nuernberg (Germany); Knupfer, M.; Buechner, B. [IFW Dresden (Germany); Umbach, E. [Universitaet Wuerzburg, Experimentelle Physik II, Wuerzburg (Germany); Forschungszentrum, Karlsruhe (Germany)

    2008-07-01

    We have recently published a design for a dedicated Soft X-Ray dispersive beamline (NIMA 575 (2007) 470-475) using photoelectron spectroscopy. The new dispersive technique allows not only NEXAFS without the time-consuming scanning of the photon energy but also high resolution CFS/CIS spectroscopic studies such as Auger/autoionization spectroscopy. The technique provides data with much more accuracy and detail hitherto achieved by simply stepping the photon energy. The method was originally tested using a ''Pilot'' setup which exploited extending the depth of focus of the monochromator by limiting the beamline angular aperture. Although very successful the decrease in angular beamline aperture obviously had drawbacks in terms of signal and also mode of operation of the monochromator (low Cff values). We present commissioning results from the upgraded monochromator demonstrating that the new design overcomes most of these difficulties.

  15. Photon flux optimization in three-color multiphoton ionization of uranium atoms

    International Nuclear Information System (INIS)

    Ionization probability in three-color excitation of uranium atoms depends on the photon flux which drives the transition to an autoionization level. for a proper choice of the flux ratio, the ionization probability is insensitive of the actual fluxes over a considerable range (Table 1). Thus, the laser intensities used may be lowered by a factor of 3 as compared with values predicted on the basis of cross-sections of the individual transition. A quantum mechanical model (see figure 1), based on a detailed calculation of population dynamics of the levels in ionization scheme, predicts the ionization probability as a function of the three laser intensities. Ionization saturation measurements provide parameters for the model. The theoretical calculations were partially consistent with the experimental results (see figure 2). Ionization probabilities as high as 93% are achievable (authors). 1 ref.; 1 tab.; 2 figs

  16. Resonance-enhanced multiphoton ionization-photoelectron spectra of CO2. I. Photoabsorption above the ionization potential

    International Nuclear Information System (INIS)

    Photoabsorption above the first ionization potential of CO2 was observed at relatively low laser intensity, detected via resonant-enhanced multiphoton ionization-photoelectron spectra through several Rydberg states. This phenomenon can be explained by the presence of accidental resonances with long-lived autoionizing states which make photon absorption within the ionization continuum possible. Laser powers are too low for this to be explained in terms of a ponderomotive potential and conventional above-threshold ionization. This resonance-enhanced above-threshold absorption phenomenon is potentially useful in the study of excited and superexcited states. Photoelectron energies can be assigned to terminations on CO+2 ionic states at both the four- and five-photon levels, allowing measurement of states up to 22 eV. Two unassigned bands may represent terminations on a new state of CO+2, with an ionization potential of 21.4 eV

  17. Photon flux optimization in three-color multiphoton ionization of uranium atoms

    International Nuclear Information System (INIS)

    Ionization probability in three color excitation of uranium atoms depends on the photon flux which drives the transition to an autoionizing level. For a proper choice of the flux ratio, the ionization probability is insensitive of the actual fluxes over a considerable range. Thus, the laser intensities used may be lowered by a factor of about 3 as compared to values predicted on the basis of cross-sections of the individual transitions. A quantum-mechanical model, based on a detailed calculation of population dynamics of the levels in the ionization scheme, predicts the ionization probability as a function of the three-laser intensities. Ionization saturation measurements provide parameters for the model. The theoretical predictions were partially consistent with the experimental results. Ionization probabilities as high as 93% are achievable

  18. Spin-mixed doubly excited resonances in Ca and Sr spectra

    International Nuclear Information System (INIS)

    We present a joint theoretical and experimental investigation to demonstrate explicitly how the combined spin-dependent interaction and the configuration interaction may affect the mixing of different spin states along various doubly excited autoionization series for Ca and Sr as energy increases across several ionization thresholds. In particular, our study has identified the inversion of energy levels between members of a number of multiplets, i.e., in contrast to the Hund's rules, due to the presence of perturber from other overlapping resonance series. We are also able to demonstrate the beginning of the breakdown of the LS coupling for resonance series corresponding to electron configurations with higher orbital angular momenta and those above the third ionization threshold.

  19. The Autler-Townes splitting in uranium observed with pulsed lasers

    International Nuclear Information System (INIS)

    We describe measurements of the Autler-Townes splitting in optical transitions in uranium using pulsed lasers in a double optical resonance experiment. These measurements give absolute values for transition strengths. Although the resolution of the experiments is insufficient to show explicitly either the magnetic degeneracy of the levels, or the quantum mechanical oscillations which arise from the pulse shape, theoretical analysis shows that both these effects contribute significantly to the observed lineshapes. Separate experiments in which a third laser was used to ionize the uranium through an autoionizing level were also performed and a fit to the ion yield as a function of laser intensities provides confirmation of the coupling strengths derived from the double optical resonance experiments. (author)

  20. Dielectronic recombination of the Xe8+ ion and satellite lines of the Xe7+ ion

    International Nuclear Information System (INIS)

    The Hartree-Fock relativistic method (Cowan code) and the relativistic many-body perturbation theory are used to perform a large-scale calculation of atomic parameters for dielectronic recombination (DR) of Pd-like Xe8+. The energy levels, radiative transition probabilities and autoionization rates are reported for 4d94fnl, 4d95l'nl, (n= 5-8) and 4d96lnl (n= 6-7) states in Ag-like Xe7+. The partial and total DR rate coefficients are calculated with account of high-n states, and contribution of different atomic configurations to DR is discussed. The branching ratios and intensity factors are calculated for dielectronic satellite lines. The obtained results can be used for modelling of various Xe plasmas including those used in lithography applications.

  1. Energy dependence of the partial widths of the Wannier two-electron ionization ladder states

    International Nuclear Information System (INIS)

    The autoionization partial widths to the 1s channel of the Wannier two-electron ionization ladder of H- are computed quantum mechanically and are compared with earlier results obtained from qualitative or semiclassical arguments. The energy dependence of the partial width Γ(E) turns out to be ∼Ep, p = 3.4 ± 0.2, which, making the substitution E ∼ 1/n2, corresponds to Γ(n) ∼ n-6.8±0.4. This finding is in reasonable agreement with an earlier result of Γ(n) ∼ n-6.254, and in strong disagreement with the recently published result which is Γ(n) ∼ n-3.254. A new semiclassical theory confirms previous conjecture. (author)

  2. Ionization Modeling Astrophysical Gaseous Structures. I. The Optically Thin Regime

    CERN Document Server

    Churchill, Christopher W; Medina, Amber; Vliet, Jacob R Vander

    2014-01-01

    We present a code for modelling the ionization conditions of optically thin astrophysical gas structures. Given the gas hydrogen density, equilibrium temperature, elemental abundances, and the ionizing spectrum, the code solves the equilibrium ionization fractions and number densities for all ions from hydrogen to zinc. The included processes are photoionization, Auger ionization, direct collisional ionization, excitation auto-ionization, charge exchange ionization, two-body radiative recombination, dielectronic recombination, and charge exchange recombination. The ionizing spectrum can be generalized to include the ultraviolet background (UVB) and/or Starburst99 stellar populations of various masses, ages, metallicities, and distances. The ultimate goal with the code is to provide fast computation of the ionization conditions of gas in N-body + hydrodynamics cosmological simulations, in particular adaptive mesh refinement codes, in order to facilitate absorption line analysis of the simulated gas for compari...

  3. Electron impact double ionization of Mg+ ions

    International Nuclear Information System (INIS)

    Electron impact ionization of atoms/ions is one of the fundamental atomic collision processes. Absolute cross sections for electron impact single and multiple ionization are of considerable importance in many fields like astrophysics and controlled nuclear fusion. Theoretical studies of electron impact double ionisation cross sections of Mg+ ions have been performed in the binary encounter approximation (BEA). Direct double ionisation has been investigated in the modified double binary encounter model. Ionization cross sections of different shells have been also calculated in order to analyse the contributions to double ionisation from ionisation-autoionization. The effect of the Coulombic field of the target ion on the incident electron has been considered in the present work. Accurate expression of σΔE (cross-section for energy transfer ΔE) and Hartree-Fock velocity distributions for the target electrons have been used throughout the calculations. The theoretical results show satisfactory agreement with the experimental observations. (authors)

  4. Storage Ring Cross Section Measurements for Electron Impact Ionization of Fe 7+

    CERN Document Server

    Hahn, M; Bernhardt, D; Grieser, M; Krantz, C; Lestinsky, M; Müller, A; Novotný, O; Repnow, R; Schippers, S; Spruck, K; Wolf, A; Savin, D W

    2015-01-01

    We have measured electron impact ionization (EII) for Fe 7+ from the ionization threshold up to 1200 eV. The measurements were performed using the TSR heavy ion storage ring. The ions were stored long enough prior to measurement to remove most metastables, resulting in a beam of 94% ground state ions. Comparing with the previously recommended atomic data, we find that the Arnaud & Raymond (1992) cross section is up to about 40\\% larger than our measurement, with the largest discrepancies below about 400~eV. The cross section of Dere (2007) agrees to within 10%, which is about the magnitude of the experimental uncertainties. The remaining discrepancies between measurement and the most recent theory are likely due to shortcomings in the theoretical treatment of the excitation-autoionization contribution.

  5. Photoionization of the ground-state Be-like B+ ion leading to the n = 2 and n = 3 states of B2+

    International Nuclear Information System (INIS)

    A theoretical study of the photoionization of the 1S ground state of Be-like B+ ion leading to the 2s, 2p, 3s and 3p states of B2+ has been performed using a noniterative eigenchannel R-matrix method. The autoionizing Rydberg series which converge to the various levels of B2+ limits up to 3d are identified and characterized. In addition, a calculation of the photoionization of the 2s2p 3Po metastable state of B+ ion was performed to compare the results with recent work on the photoionization of a mixture of ground and metastable states of the B+ ion. Excellent agreement with recent experiment and associated theory in the photon energy range 22-31.3 eV was found. The present calculation is also in overall reasonable agreement with a previous Opacity Project (OP) calculation, and excellent agreement between length and velocity gauges is found

  6. Rydberg series in the photoionization of the excited 1s2s3s 1,3Se states of atomic beryllium

    International Nuclear Information System (INIS)

    Photoionization cross sections for ionization to Be+(2s, 2p, 3s, 3p, and 3d) states from the excited 2s3s 1,3S states of atomic beryllium, which contain several autoionizing Rydberg series of resonances converging to the Be+(2p, 3s, 3p, and 3d) states, have been calculated by an enhanced noniterative eigenchannel R-matrix method. Lower members of the Rydberg series of resonances with n ≤ 10 are identified along with the calculated resonance positions Er, effective quantum numbers n*, and widths Γ. The present results are compared with those of previous calculation and very good agreement between them is noted. There is excellent agreement between length and velocity gauges in the present calculation. (author)

  7. Photoionization of the Be-like O4+ ion: total and partial cross sections for the ground 2s21S and excited 2s2p 1,3P states

    International Nuclear Information System (INIS)

    Photoionization cross sections of the Be-like O4+ ion in the photon energy region from the first threshold up to the O5+ 3d threshold have been calculated using a non-iterative variational R-matrix method combined with multichannel quantum-defect theory for the ground 2s21S and excited 2s2p 1,3P states. The partial cross sections are presented and the autoionizing resonance structures arising from the ground and excited states are identified and characterized. Our calculational results, which show excellent agreement between length and velocity gauges, are compared with the available experiment and previous calculations, and good agreement is found.

  8. Real-Time Probing of Electron Dynamics Using Attosecond Time-Resolved Spectroscopy

    Science.gov (United States)

    Ramasesha, Krupa; Leone, Stephen R.; Neumark, Daniel M.

    2016-05-01

    Attosecond science has paved the way for direct probing of electron dynamics in gases and solids. This review provides an overview of recent attosecond measurements, focusing on the wealth of knowledge obtained by the application of isolated attosecond pulses in studying dynamics in gases and solid-state systems. Attosecond photoelectron and photoion measurements in atoms reveal strong-field tunneling ionization and a delay in the photoemission from different electronic states. These measurements applied to molecules have shed light on ultrafast intramolecular charge migration. Similar approaches are used to understand photoemission processes from core and delocalized electronic states in metal surfaces. Attosecond transient absorption spectroscopy is used to follow the real-time motion of valence electrons and to measure the lifetimes of autoionizing channels in atoms. In solids, it provides the first measurements of bulk electron dynamics, revealing important phenomena such as the timescales governing the switching from an insulator to a metallic state and carrier-carrier interactions.

  9. Photoionization mass spectrometry of UF6

    International Nuclear Information System (INIS)

    The photoionization mass spectrum of 238UF6 was obtained. At 600 A = 20.66 eV, the relative ionic abundances were as follows: UF6+, 1.4; UF5+, 100; UF+, 17; UF3+, approx. 0.7; UF2+, very weak; UF+, very weak; U+, essentially zero. The adiabatic ionization potential for UF6 was 13.897 +- 0.005 eV. The production of UF5+ begins at approx. 887 A = 13.98 eV, at which energy the UF6+ partial cross section abruptly declines and then levels off. This behavior suggests the vague possibility of an isotope effect. The UF4+ signal begins at approx. 725 A = 17.10 eV, at which energy the UF5+ signal reaches a plateau value. The UF5+ photoionization yield curve displays some autoionization structure from its threshold to approx. 750 A

  10. Doubly excited 2s2p 1,3p1 resonances in photoionization of helium

    Institute of Scientific and Technical Information of China (English)

    Wan Jian-Jie; Dong Chen-Zhong

    2009-01-01

    The multi-configuration Dirac-Fock (MCDF) method is implemented to study doubly excited 2s2p 1,3P1 resonances of the helium atom and the interference between photoionization and photoexcitation autoionization processes.In order to reproduce the total photoionization sprectra,the excited energies from the ground ls2 1 S0 state to the doubly excited 2s2p 1'3P1 states and the relevant Auger decay rates and widths are calculated in detail. Furthermore,the interference profile determined by the so-called Fano parameters q and p2 is also reproduced. Good agreement is found between the present results and other available theoretical and experimental results. This indeed shows a promising way to investigate the Fano resonances in photoionization of atoms within the MCDF scheme,although there are some discrepancies in the present calculations of the 2s2p 3P1 state.

  11. Methods for polarized electron production during atom photoionization

    International Nuclear Information System (INIS)

    The comparison of polarized electron production methods available is carried out. The polarized electron production during ionization of atoms with a single outermost electron by circular polarization light is considered in detail. Polarized electrons is produced in the following cases: 1) near the Cooper minimum in the p→d transitions; 2) in the range of autoionizing states with total moment J=1/2 for which the only decay channel is the np→epsilonS transition; 3) during two-photon ionization when the first photon excites the descrete n'Ssub(1/2)-state. The second method possesses the maximal electron quantum yield, but the necessity of usage the power monochromatic source is the disadvantage. In the third case the laser application is possible. The parameters of the tallium electron source employing the effects described are given

  12. Progress on and Instrumentation for an Ion Inteferometer

    Science.gov (United States)

    Jackson, Jarom; Archibald, James; Christopher, Erickson; Durfee, Dallin

    2013-05-01

    We describe progress on a cold ion matter-wave interferometer. The ions are generated by laser-cooling strontium and then photo-ionizing the atoms with a two-photon transition to an auto-ionizing state in the continuum. A pair of electrodes will set the kinetic energy of the ions. Splitting and recombining the quantum waves will be achieved using Raman transitions driven by a pair of laser beams. These beams are created by injection locking a pair of diode lasers with two beams from a master laser which have been shifted to differ in frequency by the strontium ion hyperfine splitting. Optical pumping and detection of the ions will be done with a laser locked to a column of strontium vapor which has been photo-ionized. Funding provided by the NSF and NIST.

  13. X-ray emission measurements following charge exchange between C$^{6+}$ and H$_2$

    CERN Document Server

    Fogle, M; Morgan, K; McCammon, D; Seely, D G; Draganić, I N; Havener, C C

    2014-01-01

    Lyman x-ray spectra following charge exchange between C$^{6+}$ and H$_2$ are presented for collision velocities between 400 and 2300 km/s (1--30 keV/amu). Spectra were measured by a microcalorimeter x-ray detector capable of fully resolving the C VI Lyman series emission lines though Lyman-$\\delta$. The ratios of the measured emission lines are sensitive to the angular momentum $l$-states populated during charge exchange and are used to gauge the effectiveness of different $l$-distribution models in predicting Lyman emission due to charge exchange. At low velocities, we observe that both single electron capture and double capture autoionization contribute to Lyman emission and that a statistical $l$-distribution best describes the measured line ratios. At higher velocities single electron capture dominates with the $l$-distribution peaked at the maximum $l$.

  14. Resonant enhancement of a single attosecond pulse in a gas medium by a time-delayed control field

    International Nuclear Information System (INIS)

    An optical coherent control scheme has been proposed and theoretically investigated where an extreme ultraviolet single attosecond pulse (SAP) propagates through dense helium gas dressed by a time-delayed femtosecond laser pulse. The laser pulse couples the 2s2p(1P) and 2s2(1S) autoionizing states when the SAP excites the 2s2p state. After going through the gas, the spectral and temporal profiles of the SAP are strongly distorted. A narrowed but enhanced spike in the spectrum shows up for specific intensities and time delays of the laser, which exemplifies the control of a broadband photon wave packet by an ultrashort dressing field for the first time. We analyse the photon and electron dynamics and determine the dressing condition that maximizes this enhancement. The result demonstrates new possibilities of attosecond optical control.

  15. Detection and speciation of trace amounts of neptunium and plutonium

    International Nuclear Information System (INIS)

    This paper reports that laser resonance ionization mass spectrometry has been investigated as a method for the detection of trace amounts of neptunium and plutonium. The instrument consists of three tunable pulsed dye lasers pumped by one or two copper vapor lasers and a time-of-flight spectrometer. High selectivity can be achieved by three-step photoionization. Measurements of the isotopic ratios of plutonium yielded a good agreement with mass spectrometric data. By saturating the excitation steps and by using autoionizing states for the ionization step, a detection efficiency of 4 x 10-6 has been determined for plutonium, corresponding to a detection limit of less than 107 atoms. Electrophoretic ion focusing enable s the separation of oxidation states of neptumiun and plutonium. The combination of this analytical technique with radiometric detection method or laser resonance ionization mass spectrometry allows the speciation of neptunium and plutonium at very low concentrations

  16. Various applications of atomic physics and kinetics codes to plasma modeling

    International Nuclear Information System (INIS)

    A collection of computer codes developed at Los Alamos have been applied to a variety of plasma modeling problems. The CATS, RATS, ACE, and GIPPER codes are used to calculate a consistent set of atomic physics data for a given problem. The calculated data include atomic energy levels, oscillator strengths, electron impact excitation and ionization cross sections, photoionization cross sections, and autoionization rates. The FINE and LINES codes access these data sets directly to perform plasma modeling calculations. Preliminary results of some of the current applications are presented, including, the calculation of holmium opacity, the modeling of plasma flat panel display devices, the analysis of some new results from the LANL TRIDENT laser and prediction of the radiative properties of the plasma wakefield light source for extreme ultraviolet lithography (EUVL). For the latter project, the simultaneous solution of atomic kinetics for the level populations and the Boltzmann equation for the electron energy distribution is currently being implemented. copyright 1996 American Institute of Physics

  17. Entanglement Properties of the Two-Electron Quasi-One Dimensional Gaussian Quantum Dot

    International Nuclear Information System (INIS)

    We analyze the entanglement characteristics of the quasi one-dimensional quantum dot containing two Coulombically interacting electrons in an inverted Gaussian potential. The linear entropy of the lowest energy states is calculated in the whole range of the effective interaction strength g for different parameters of the longitudinal potential and the lateral radius of the quantum dot. We employ the configuration interaction method with complex-coordinate rotation, since the considered states become autoionizing resonances at the interaction strength above the critical value gth . We study the dependence of the linear entropy on the parameters of the quantum dot and discuss how the stability properties of the system are characterized by the entanglement between the electrons. (author)

  18. Real-Time Probing of Electron Dynamics Using Attosecond Time-Resolved Spectroscopy.

    Science.gov (United States)

    Ramasesha, Krupa; Leone, Stephen R; Neumark, Daniel M

    2016-05-27

    Attosecond science has paved the way for direct probing of electron dynamics in gases and solids. This review provides an overview of recent attosecond measurements, focusing on the wealth of knowledge obtained by the application of isolated attosecond pulses in studying dynamics in gases and solid-state systems. Attosecond photoelectron and photoion measurements in atoms reveal strong-field tunneling ionization and a delay in the photoemission from different electronic states. These measurements applied to molecules have shed light on ultrafast intramolecular charge migration. Similar approaches are used to understand photoemission processes from core and delocalized electronic states in metal surfaces. Attosecond transient absorption spectroscopy is used to follow the real-time motion of valence electrons and to measure the lifetimes of autoionizing channels in atoms. In solids, it provides the first measurements of bulk electron dynamics, revealing important phenomena such as the timescales governing the switching from an insulator to a metallic state and carrier-carrier interactions. PMID:26980312

  19. LS-averaged 1/Z method as a tool of studying the interactions of highly charged ions with a metal surface

    International Nuclear Information System (INIS)

    In the present paper, a new theoretical approach is described for the calculation of the atomic characteristics of the multiply charged ions (MCI) in various electronic configurations. This theoretical approach is based on the perturbation theory using the nuclear charge of the ion as a parameter and the inter electron interaction and relativistic corrections as a perturbation. In order to reduce a large number of the calculations of atomic data for many different electron configurations which may be formed in MCI colliding with a surface, the transition energies, radiative transition probabilities and autoionizing rates are averaged over the orbital and spin quantum numbers. It turned out that these atomic characteristics can be expressed in analytical forms as a function of the number of electrons in different shells of the ions and the suggested method can be applied for the calculation of the atomic characteristics of practically any atomic system with arbitrary number of electrons. (author)

  20. EXPANDED IRON UTA SPECTRA-PROBING THE THERMAL STABILITY LIMITS IN AGN CLOUDS

    Energy Technology Data Exchange (ETDEWEB)

    Ferland, G. J.; Lykins, M. L. [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506 (United States); Kisielius, R.; Jonauskas, V. [Institute of Theoretical Physics and Astronomy, Vilnius University, A. Gostauto 12, LT-01108 (Lithuania); Keenan, F. P. [Astrophysics Research Centre, School of Mathematics and Physics, Queen' s University Belfast, Belfast BT7 1NN (United Kingdom); Van Hoof, P. A. M. [Royal Observatory of Belgium, Ringlaan 3, B-1180 Brussel (Belgium); Porter, R. L. [Department of Physics, University of Georgia, Athens, GA 30602 (United States); Williams, R. J. R., E-mail: gary@pa.uky.edu [AWE plc, Aldermaston, Reading RG7 4PR (United Kingdom)

    2013-04-20

    The Fe unresolved transition arrays (UTAs) produce prominent features in the {approx}15-17 A wavelength range in the spectra of active galactic nuclei (AGNs). Here, we present new calculations of the energies and oscillator strengths of inner-shell lines from Fe XIV, Fe XV, and Fe XVI. These are crucial ions since they are dominant at inflection points in the gas thermal stability curve, and UTA excitation followed by autoionization is an important ionization mechanism for these species. We incorporate these, and data reported in previous papers, into the plasma simulation code Cloudy. This updated physics is subsequently employed to reconsider the thermally stable phases in absorbing media in AGNs. We show how the absorption profile of the Fe XIV UTA depends on density, due to the changing populations of levels within the ground configuration.

  1. Low-energy photodetachment of Ga- and elastic electron scattering from neutral Ga

    Science.gov (United States)

    Wang, Kedong; Zatsarinny, Oleg; Bartschat, Klaus

    2016-08-01

    We present a comprehensive study of the photodetachment of the negative gallium ion and elastic electron scattering from neutral Ga for photon and electron energies ranging from threshold to 12 eV. The calculations are carried out with the B -spline R -matrix method. A multiconfiguration Hartree-Fock method with nonorthogonal term-dependent orbitals is employed to generate accurate initial- and final-state wave functions. The close-coupling expansions include the 4 s 24 p n l (k l ) bound and continuum states of Ga and the 4 s -excited autoionizing states 4 s 4 p2 . The calculated photodetachment and elastic cross sections exhibit prominent resonance features. In order to clarify the origin of these resonances, the contributions of the major ionization channels to the partial cross sections are analyzed in detail.

  2. Atomic and Molecular Aspects of Astronomical Spectra

    CERN Document Server

    Sochi, Taha

    2012-01-01

    In the first section we present the atomic part where a C2+ atomic target was prepared and used to generate theoretical data to investigate recombination lines arising from electron-ion collisions in thin plasma. R-matrix method was used to describe the C2+ plus electron system. Theoretical data concerning bound and autoionizing states were generated in the intermediate-coupling approximation. The data were used to generate dielectronic recombination data for C+ which include transition lines, oscillator strengths, radiative transition probabilities, emissivities and dielectronic recombination coefficients. The data were cast in a line list containing 6187 optically-allowed transitions which include many C II lines observed in astronomical spectra. This line list was used to analyze the spectra from a number of astronomical objects, mainly planetary nebulae, and identify their electron temperature. The electron temperature investigation was also extended to include free electron energy analysis to investigate...

  3. Resonance Averaged Photoionization Cross Sections for Astrophysical Models

    CERN Document Server

    Bautista, M A; Pradhan, A K

    1997-01-01

    We present ground state photoionization cross sections of atoms and ions averaged over resonance structures for photoionization modeling of astrophysical sources. The detailed cross sections calculated in the close-coupling approximation using the R-matrix method, with resonances delineated at thousands of energies, are taken from the Opacity Project database TOPbase and the Iron Project, including new data for the low ionization stages of iron Fe I--V. The resonance-averaged cross sections are obtained by convolving the detailed cross sections with a Gaussian distribution over the autoionizing resonances. This procedure is expected to minimize errors in the derived ionization rates that could result from small uncertainties in computed positions of resonances, while preserving the overall resonant contribution to the cross sections in the important near threshold regions. The detailed photoionization cross sections at low photon energies are complemented by new relativistic distorted-wave calculations for Z1...

  4. About problems of the interpretation of spectroscopic data from plasmas

    International Nuclear Information System (INIS)

    Quantitative plasma spectroscopy dates now back to more than 40 years and has become an indispensable diagnostic tool for numerous types of laboratory and astrophysical sources of plasma radiation. A large driving force for continued developments of plasma spectroscopic methods is originating from inertial and magnetic fusion research and the rapid development of x-ray lasers. The related problems are impressive: non-Maxwellian particle distributions, charge state distribution and power loss of heavy elements, strongly coupled plasmas, destruction of the Coulomb potential of test elements in super dense plasmas, particle diffusion, interpenetrating plasmas, transient non-LTE plasma evolution. An overview of the current developments of plasma spectroscopy which are able to deal with so complicated phenomena is given. They are based on the analysis of radiation from complex autoionizing states (hollow ions and dielectronic satellite emission), charge exchange, super-configuration approaches and the Virtual Contour Shape Kinetic Theory. (author)

  5. Diffusion-Oscillatory Dynamics in Liquid Water on Data of Dielectric Spectroscopy

    CERN Document Server

    Volkov, A A; Volkov, A A; Sysoev, N N

    2016-01-01

    When analyzing the broadband absorption spectrum of liquid water (10^10 - 10^13 Hz), we find its relaxation-resonance features to be an indication of Frenkel's translation-oscillation motion of particles, which is fundamentally inherent to liquids. We have developed a model of water structure, of which the dynamics is due to diffusion of particles, neutral H2O molecules and H3O+ and OH- ions - with their periodic localizations and mutual transformations. This model establishes for the first time a link between the dc conductivity, the Debye and the high frequency sub-Debye relaxations and the infrared absorption peak at 180 cm-1. The model reveals the characteristic times of the relaxations, 50 ps and 3 ps, as the lifetimes of water molecules and water ions, respectively. The model sheds light on the anomalous mobility of a proton and casts doubt on the long lifetime of a water molecule, 10 hours, commonly associated with autoionization.

  6. Crystal momentum dependence of the correlation satellite intensity in the 3p → 3d resonant photoemission spectra of Bi2Sr2CaCu2O8 + δ

    Science.gov (United States)

    Goldoni, A.; Corradini, V.; del Pennino, U.; Sangalli, P.; Parmigiani, F.; Avila, J.; Teodorescu, C.

    2000-05-01

    Angle-resolved resonant photoemission measurements at the Cu3p → Cu3d threshold have been performed on the superconducting cuprate Bi2Sr2CaCu2O8 + δ. We have investigated in particular the correlation satellite appearing in the valence band photoemission spectrum to investigate the effect of solid state on the interference effect occurring at resonance. We found that the intensity of the correlation satellite changes with the electron take-off angle in a way that depends on the particular crystallographic direction and on the sample hole doping. These results indicate that the intensity enhancement at the absorption edge is a real resonance albeit the intermediate state in the autoionization process is partly delocalised. This fact does not prevent the occurrence of interference between indirect and direct photoemission.

  7. Crystal momentum dependence of the correlation satellite intensity in the 3p {yields} 3d resonant photoemission spectra of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Goldoni, A. [INFM, Trieste (Italy); Corradini, V.; Del Pennino, U. [INFM, Modena (Italy); Sangalli, P. [INFM, Pavia (Italy); Parmigiani, F. [INFM, Brescia (Italy); Avila, J. [CSIC, Madrid (Spain). Inst. de Ciencia de Materiales; Laboratoire pour l' Utilisation du Rayonnement Electromagnetique (LURE), Paris-11 Univ., 91 - Orsay (France); Teodorescu, C. [Laboratoire pour l' Utilisation du Rayonnement Electromagnetique (LURE), Paris-11 Univ., 91 - Orsay (France)

    2000-05-01

    Angle-resolved resonant photoemission measurements at the Cu3p {yields} Cu3d threshold have been performed on the superconducting cuprate Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}. We have investigated in particular the correlation satellite appearing in the valence band photoemission spectrum to investigate the effect of solid state on the interference effect occurring at resonance. We found that the intensity of the correlation satellite changes with the electron take-off angle in a way that depends on the particular crystallographic direction and on the sample hole doping. These results indicate that the intensity enhancement at the absorption edge is a real resonance albeit the intermediate state in the autoionization process is partly delocalised. This fact does not prevent the occurrence of interference between indirect and direct photoemission. (orig.)

  8. Crystal momentum dependence of the correlation satellite intensity in the 3p → 3d resonant photoemission spectra of Bi2Sr2CaCu2O8+δ

    International Nuclear Information System (INIS)

    Angle-resolved resonant photoemission measurements at the Cu3p → Cu3d threshold have been performed on the superconducting cuprate Bi2Sr2CaCu2O8+δ. We have investigated in particular the correlation satellite appearing in the valence band photoemission spectrum to investigate the effect of solid state on the interference effect occurring at resonance. We found that the intensity of the correlation satellite changes with the electron take-off angle in a way that depends on the particular crystallographic direction and on the sample hole doping. These results indicate that the intensity enhancement at the absorption edge is a real resonance albeit the intermediate state in the autoionization process is partly delocalised. This fact does not prevent the occurrence of interference between indirect and direct photoemission. (orig.)

  9. Contribution to simple and double photoionization studies in several molecules excited by synchrotron radiation

    International Nuclear Information System (INIS)

    This work is divided into two parts. Photoelectron spectrometry has enabled us to study the simple photoionisation in inner and outer shell of the N2 molecule. The limits of an independent particle model, and the importance of electronic interactions have been outlined; an analysis of the structures situated at a photon energy of 23 eV revealed the behavior of two kinds of autoionizing states; the shape resonances of the Σg+ states have been compared. We have then built a new experimental set-up to study double photoionisation. The case of the CS2 molecule has been examined by mass spectrometry associated to a PIPICO (PhotoIon-PhotoIon Coincidence) technique. An approach of the spectroscopy of the CS2++ ion has been proposed; two dissociation paths of the ion have been observed, their mechanisms are discussed. (author)

  10. Hollow ion formation and decay in slow Bi{sup 46+}-C{sub 60} collisions

    Energy Technology Data Exchange (ETDEWEB)

    Thumm, U. [J. R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States)

    1997-01-01

    The interaction of slow highly charged ions with many-electron targets leads to the formation of unstable, multiply excited projectiles. We simulated the formation of such hollow ions for slow incident Bi{sup 46+} projectiles and C{sub 60} targets. Our semiclassical overbarrier simulation includes resonant exchange and Auger emission of electrons. It models the dynamical variation of level occupations and charge states during the collision and predicts highly unstable hollow ions immediately after the collision. With respect to the subsequent downstream relaxation of the hollow ions, we propose a simple relaxation scheme that includes autoionizing and radiative transitions. As a consequence of this downstream relaxation, almost all of the resonantly captured electrons are emitted. {copyright} {ital 1997} {ital The American Physical Society}

  11. Fully differential measurements for electron capture in collisions of slow Heq+ and NeNq+ with He and Ne

    International Nuclear Information System (INIS)

    We report on kinematically complete studies of electron capture from He (and Ne) in collisions with slow Heq+ (and Neq+) projectiles using a 'Reaction Microscope'. We succeeded in collecting fully differential data sets for several reaction channels like single and double electron capture, resonant capture and capture accompanied with subsequent auto-ionization. The results are compared with theoretical model calculations. In order to achieve an efficient detection of emitted recoil-ions and electrons we implemented large area position sensitive MCP detectors with central holes for the passage of the projectile beam. This enabled us to measure the recoiling target ion in coincidence with Auger-electrons emitted from the highly excited projectile ion after capture. The experimental setup and first results of ongoing measurements are presented.

  12. Density and temperature diagnostics of x-ray sources: Line ratios for helium-like ions

    International Nuclear Information System (INIS)

    Improved calculations are made for the line ratios R = f/i and G = (i+f)/r involving the forbidden (f), the intercombination (i), and the resonance (r) lines of helium-like ions: C V, O VII, Ne IX, Si XIII, Ca XIX, and Fe XXV. The ratios in ionization equilibrium are obtained over a range of electron temperatures. Departures from ionization equilibrium are also studied. In cases where the i and the r lines appear blended together, the electron density may be derived from the observed ratio K = f/(i+r). We use the best available atomic data, including accurate rate coefficients for collisional excitation computed earlier, taking into account the effect of autoionizing resonances on electron impact cross sections. These effects enhance considerably the rates for the f and the i transitions. For the line ratios observed in the Sun and in supernova remnants, the density and temperature diagnostics based on previous works may not be entirely correct

  13. Dynamic modification of the fragmentation of COq+ excited states generated with high-order harmonics

    International Nuclear Information System (INIS)

    The dynamic process of fragmentation of COq+ excited states is investigated using a pump-probe approach. EUV radiation (32-48 eV) generated by high-order harmonics was used to ionize and excite CO molecules and a time-delayed infrared (IR) pulse (800 nm) was used to influence the evolution of the dissociating multichannel wave packet. Two groups of states, separable experimentally by their kinetic-energy release (KER), are populated by the EUV and lead to C+-O+ fragmentation: direct double ionization of the neutral molecule and fragmentation of the cation leading to C+-O*, followed by autoionization of O*. The IR pulse was found to modify the KER of the latter group in a delay-dependent way which is explained with a model calculation.

  14. Electron impact single ionization of multiply charged iron ions

    International Nuclear Information System (INIS)

    Employing the animated crossed-beams technique, absolute cross sections for electron impact single ionization of the iron isonuclear sequence are measured for charge states q=1-6 for electron energies from threshold up to 1 keV, as well as for the intermediate charge states q=9,10 up to an electron energy of 5 keV. The cross sections observed for Feq+ ions in charge states q=1-4, 9 and 10 show a significant ionization signal below the respective ground state threshold resulting from ions in excited, long-lived metastable states in the parent ion beam. In the case of Fe5+ and Fe6+ no metastable components are found. The experimental results are in good agreement with the theoretical predictions if excitation-autoionization processes are taken into account. Our measured cross sections are also in good agreement with experimental results of other groups. (author)

  15. Electron-impact single-ionization of singly and multiply charged tungsten ions

    International Nuclear Information System (INIS)

    Employing the 'crossed-beams' technique, electron-impact ionization cross sections for the single-ionization of Wq+ ions in charge states q = 1...10 have been measured. The cross sections for the ionization of ions in charge states q ≥ 5 show significant contributions below the ground-state threshold caused by the ionization of ions in excited, long-lived metastable states in the parent ion beam. In the case of W6+, the measured cross section is completely dominated by metastable contributions. For ions in charge states q = 3...7, excitation-autoionization from the ground state as well as from excited, metastable states contributes strongly to the cross sections. This results in a strong underestimation of the measured cross sections by the semiempirical Lotz formula in the energy range between the ionization threshold and the cross section maximum. (Author)

  16. Doubly excited helium. From strong correlation to chaos

    International Nuclear Information System (INIS)

    In the present dissertation, the double excitation states of helium including the autoionization decay of these states were studied experimentally and theoretically in a broad energy region, which includes the transition from strong correlation below the low single ionization thresholds (SIT) to the region of quantum chaos at energies very close to the double-ionization threshold. Two kind of experiments were performed, namely total-ion-yield measurements with the aim to observe total cross sections (TCS) and electron time-of-flight (TOF) measurements to obtain partial cross sections (PCS) as well as angular distribution parameters (ADP). Both types of measurements were performed at the third generation synchrotron radiation facility BESSY II in Berlin. The TCSs were recorded up to the SIT I15, and they were found to be in in excellent agreement with state-of-the-art complex-rotation calculations performed recently by D. Delande. These experimental and theoretical data on the TCSs were analyzed in order to study quantum chaos in doubly excited helium, and interesting signatures of quantum chaos were found. The TOF technique allowed to measure PCSs and ADPs in the energy regions from I5 to I9 and I7, respectively. These experimental data provide a critical assessment of theoretical models that can be used to explore the dynamics of strong correlation as well as quantum chaos in helium. In the theoretical part of this dissertation, the n- and l-specific PCSs and ADPs below I4 were calculated employing the R-matrix method. The present theoretical results agree well with a recent experimental study of l-specific PCSs below I4 by J.R. Harries et al. An analysis of patterns in the PCSs and ADPs on the basis of the present experimental and theoretical l-specific data allowed to improve the present understanding of autoionization decay dynamics in this two-electron atom. (orig.)

  17. Bombardment induced electronic processes at insulator surfaces: The role of electron-capture collisions

    International Nuclear Information System (INIS)

    Discrete features observed in the energy distribution of electrons emitted from ion-bombarded sodium halide surfaces can be attributed to a new type of collisional deexcitation mechanism. This mechanism involves collisions of sodium in bombardment-excited states with other lattice ions so that, in contract to a metal, the deexcitation process is not simply a consequence of the inner-shell lifetime of the excited sodium ion. Rather, the deexcitation process involves a sequence of collisions within the solid during which the collisionally excited Na+ ion captures an electron to form a neutral excited Na0 atoms; it is the autoionization of these inner-shell excited states of Na0 that are responsible for the observed transition. The authors have found that for such localized electron-transfer processes, the Na0 that are responsible for the observed transitions. They have found that for such localized electron-transfer processes, the Na0 deexcitation transitions can only be associated with a specific lattice collision in which a Na+ captures an electron from a negative halogen lattice ion. These Na0 transitions, therefore, are a direct monitor of the electron transfer event itself. A model is proposed to account for the formation of such autoionizing Na0 states in which excitation processes and localized collisional electron-transfer mechanisms are taken into account. In this model, the electron transfer process is described by a Landau-Zener-Stueckelberg resonant level-crossing mechanism. This type of localized electron-transfer process makes possible new channels for electronic deexcitation and chemical activity. The authors believe that such processes are critical for understanding inelastic ion-surface collisions in solids

  18. Effect of the Rydberg states on the time evolution of nonstationary states below or just above the ionization threshold

    International Nuclear Information System (INIS)

    We consider problems of short-time dynamics of a polyelectronic atomic nonstationary state, V, assumed to be formed as a wave packet at t=0. We focus on two cases, for which the role of the quasicontinuum of the upper part of the Rydberg states, with which the V state has nonzero coupling matrix elements, is investigated. In the first case, the position of the V state is just above the ionization threshold, E=0, and so V dissipates into the free electron continuum as an autoionizing state. The question is how the presence of the Rydberg series converging to E=0 affects the time evolution of the autoionizing V. In the second case, the position of V is embedded in the quasicontinuum of the Rydberg series below threshold. The question is whether there are distinct features in the time evolution of this V, although its position is in the discrete part of the energy spectrum. In this case, by focusing on short times and by evaluating analytically certain infinite sums, analogous to Fourier integrations, the following result is obtained: For small times, the V state evolves as an exponentially decaying state. However, in addition to the term describing exponential decay, there is a term, entering with a small coefficient, which describes exponential growth and eventually dominates. It is shown that exponential decay holds for times shorter than the time tp needed by the wave packet to reach the outer classical turning point. For the decay to be physically meaningful, this time must be smaller than the time td which equals the inverse of the half-width in atomic units. We examined a model system of V-Rydberg state interaction based on the Boron 2S spectrum. The results indicate that the effect is observable on the scale of femtoseconds

  19. Experimental study of the collision mechanisms involved in one-electron capture by slow N5+ ions in atomic and molecular hydrogen

    International Nuclear Information System (INIS)

    Translational energy spectroscopy (TES) in the range 214-857 eV amu-1 has been used to study the collision mechanisms involved in one-electron capture by slow helium-like N5+ in both atomic and molecular hydrogen. In the case of N5+-H2 collisions, our measurements show that non-dissociative electron capture leading to the N4+ (n=3) states is the main product channel at the higher impact energies with smaller contributions to the N4+ (n=4) states. While this has also been observed in previous studies based on photon emission spectroscopy (PES), there are substantial differences in both magnitude and energy dependence between the TES and PES results. Theoretical predictions for n=3 formation are also in poor accord with experiment. Unlike previous PES measurements, the present TES study has been able to identify the presence of dissociative one-electron capture channels and two-electron autoionizing capture channels, both leading to N4+ (n=2) formation. Two-electron autoionizing electron capture is found to be the main collision mechanism leading to N4+ ions at the lowest energies considered. Our measurements of one-electron capture in N5+ + H(1s) are in excellent accord with previous higher measurements based on PES and now provide a useful extension to energies below 1 keV amu-1. In this case, only the N4+ (n=4) and N4+ (n=3) product channels are observed, with contributions from the latter becoming insignificant at our lowest energies

  20. Dielectronic recombination of Zn-like W44 + from Cu-like W45 +

    Science.gov (United States)

    Safronova, U. I.; Safronova, A. S.; Beiersdorfer, P.

    2015-06-01

    Energy levels, radiative transition probabilities, and autoionization rates for [Ar]3 d104 l'n l (n =4 -12 , l ≤n -1 ), [Ar]3 d105 l'n l (n =5 -8 , l ≤n -1 ), and [Ar]3 d94 l'4 l''n l (n =4 -5 , l ≤n -1 ) states in Zn-like tungsten (W44 +) are calculated using the relativistic Hartree-Fock method (cowan code), the multiconfiiguration relativistic Hebrew University Lawrence Livermore Atomic Code (hullac code), and the relativistic many-body perturbation theory method (rmbpt code). Autoionizing levels above the thresholds [Ar]3 d104 s are considered. It is found that configuration mixing [4 s n s +4 p n p +4 d n d +4 f n f ], [4 s n p +4 p n s +4 p n d +4 d n p +4 f n s +4 f n d ] plays an important role for all atomic characteristics. Branching ratios relative to the first threshold and intensity factors are calculated for satellite lines, and dielectronic recombination (DR) rate coefficients are determined for the first excited odd- and even-parity states. It is shown that the contribution of the highly excited states is very important for the calculation of total DR rates. Contributions to DR rate coefficients from the excited [Ar]3 d104 l'n l states with n >12 and [Ar]3 d105 l'n l states with n >8 , and additionally from core-excited [Ar]3 d94 l'4 l''n l states with n >5 , are estimated by extrapolation of all atomic parameters. The orbital angular momentum quantum number l distribution of the rate coefficients shows two peaks at l =2 and l =5 . The total DR rate coefficient is derived as a function of electron temperature. The dielectronic satellite spectra of W44 + are important for M -shell diagnostic of very high-temperature laboratory plasmas such as those found in future tokamaks.

  1. Model atomic systems in intense laser fields. Exact time-dependent density functional and Floquet theory

    International Nuclear Information System (INIS)

    Describing the quantum dynamics in strong time-dependent external fields is challenging for at least two reasons. Firstly, the external driver has to be treated in a non-perturbative way. Secondly, correlations, responsible for phenomena such as single-photon double ionization, nonsequential double ionization, autoionization, Auger decay etc., have to be taken into account. The ab initio solution of the time-dependent Schroedinger equation for a many-body system is feasible for only a few constituents. Density functional theory (DFT) has been successful in overcoming the exponentially increasing complexity of solving the stationary Schroedinger equation in electronic structure applications. Its time-dependent extension (TDDFT) is widely applied within the linear response domain. However, its success when it comes to highly correlated electron dynamics in, for instance, strong laser fields, is very limited, reasons being the lack of a sufficiently accurate exchange-correlation potential in the Kohn-Sham equation and functionals for the relevant observables. Numerically exactly solvable model systems are hence very useful to proceed with the further development of TDDFT. In this thesis, the exact exchange-correlation potential for the highly correlated process of autoionization in a model Helium atom is constructed. Besides applying a suitable many-body technique one may try to employ the time-periodicity of external drivers such as laser fields. The Floquet theorem allows to rewrite partial differential equations with timeperiodic coefficients as sets of time-independent algebraic equations. If the Floquet theorem could also be applied to the time-dependent Kohn-Sham equation of TDDFT the time-dependent many-body problem could be reduced to a time-independent one. In this thesis, it is investigated under which circumstances this is possible. To that end a method is introduced to extract the information about light-induced states (Floquet states) and their

  2. DNA strand breaks and crosslinks induced by transient anions in the range 2-20 eV

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Xinglan; Zheng, Yi, E-mail: Yizheng@fzu.edu.cn [Research Institute of Photocatalysis, State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou 350002 (China); Sanche, Léon [Group in the Radiation Sciences, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4 (Canada)

    2014-04-21

    The energy dependence of the yields of single and double strand breaks (SSB and DSB) and crosslinks induced by electron impact on plasmid DNA films is measured in the 2-20 eV range. The yield functions exhibit two strong maxima, which are interpreted to result from the formation of core-excited resonances (i.e., transient anions) of the bases, and their decay into the autoionization channel, resulting in π → π{sup *} electronic transitions of the bases followed by electron transfer to the C–O σ{sup *} bond in the phosphate group. Occupancy of the σ{sup *} orbital ruptures the C–O bond of the backbone via dissociative electron attachment, producing a SSB. From a comparison of our results with those of other works, including theoretical calculations and electron-energy-loss spectra of the bases, the 4.6 eV peak in the SSB yield function is attributed to the resonance decay into the lowest electronically excited states of the bases; in particular, those resulting from the transitions 1{sup 3}A{sup ′} (π{sub 2} → π{sub 3}{sup *}) and 1{sup 3}A{sup ″} (n{sub 2} → π{sub 3}{sup *}) of thymine and 1{sup 3}A{sup ′} (π → π{sup *}) of cytosine. The strongest peak at 9.6 eV in the SSB yield function is also associated with electron captured by excited states of the bases, resulting mostly from a multitude of higher-energy π → π{sup *} transitions. The DSB yield function exhibits strong maxima at 6.1 and 9.6 eV. The peak at 9.6 eV is probably related to the same resonance manifold as that leading to SSB, but the other at 6.1 eV may be more restricted to decay into the electronic state 1{sup 3}A{sup ′} (π → π{sup *}) of cytosine via autoionization. The yield function of crosslinks is dominated by a broad peak extending over the 3.6-11.6 eV range with a sharper one at 17.6 eV. The different line shape of the latter function, compared to that of SSB and DSB, appears to be due to the formation of reactive radical sites in the initial supercoiled

  3. Radiative opacity of plasmas studied by detailed term (level) accounting approaches

    Institute of Scientific and Technical Information of China (English)

    ZENG Jiao-long; JIN Feng-tao; YUAN Jian-min

    2006-01-01

    Detailed term and level accounting (DTA and DLA) schemes have been developed to calculate the spectrally resolved and Rosseland and Planck mean opacities of plasmas in local thermodynamic equilibrium.Various physical effects,such as configuration interaction effect (including core-valence electron correlations effect and relativistic effect),detailed line width effect (including the line saturation effect),etc.,on the opacity of plasmas have been investigated in detail.Some of these physical effects are less capable or even impossible to be taken into account by statistical models such as unresolved transition arrays,super-transitionarray or average atom models.Our detailed model can obtain accurate opacity of plasmas.Using this model,we have systematically investigated the radiative opacities of low,medium and high-Z plasmas under different conditions of temperature and density.For example,for aluminum plasma,in the X-ray region,we demonstrated the effects of autoionization resonance broadening on the opacity for the first time.Furthermore,the relativistic effects play an important role on the opacity as well.Our results are in good agreement with other theoretical ones although better agreement can be obtained after the effects of autoionization resonance broadening and relativity have been considered.Our results also show that the modelling of the opacity is very complicated,since too many physical effects influence the accuracy of opacity.``For medium and high-Z plasmas,however,there are systematic discrepancies unexplained so far between the theoretical and experimental opacities.Here,the theoretical opacities are mainly obtained by statistical models.To clarify the discrepaneies,efforts from both sides are needed.From the viewpoint of theory,however,a DLA method,in which various physical effects can be taken into account,should be useful in resolving the difference.Taking gold plasma as an example,we studied in detail the effects of core-valence electron

  4. Quantal Description of Atomic Diamagnetism: the Quasi-Landau Resonances

    Science.gov (United States)

    Wang, Qiaoling

    We describe atomic hydrogen diamagnetism within the framework of nonrelativistic quantum mechanics. Our theoretical studies have used three descriptions: an adiabatic description, a multichannel quantum defect theory (MQDT) description using an ab initio R-matrix approach, and a model description. The analysis has conclusively demonstrated that the diamagnetic spectrum can be viewed as a perturbed Rydberg spectrum. The adiabatic analysis provides a crude but useful picture to see the overall channel structure and the nature of the perturbing configurations, where the quasi-Landau resonances are the lowest states in each Landau channel which will perturb high Rydberg states in lower Landau channels once the nonadiabatic coupling is turned on. The ab initio calculation of the photoionization spectrum in the field range 10^3 -10^4 Tesla shows that the quasi -Landau resonances are broad interlopers which perturb high Rydberg states converging to the Landau thresholds, forming complex resonances. Also in these calculations, a new partial cross section analysis has been performed to predict the relative electron populations in different Landau channels. The population is found to depend on the azimuthal quantum number and the parity of final states. For photoionization from the hydrogen ground state of final states with m = 1, the electron is predicted to escape predominantly in the higher Landau channels. In contrast, for the final states with m = 0, it escapes in the lower channels. This property is reflected in the shape of autoionizing resonances, which are more like peaks for m = 1, but are more like dips (window resonances) for m = 0. In studying the features of the complex resonances, formed by the quasi-Landau resonances perturbing the high Rydberg states, we developed an analytical description using a model based on three interacting Rydberg channels, identifying the key dynamical quantities which control the appearance of a complex resonance and its evolution

  5. Positronic complexes with unnatural parity

    International Nuclear Information System (INIS)

    The structure of the unnatural parity states of PsH, LiPs, NaPs, and KPs are investigated with the configuration interaction and stochastic variational methods. The binding energies (in hartree) are found to be 8.17x10-4, 4.42x10-4, 15.14x10-4, and 21.80x10-4, respectively. These states are constructed by first coupling the two electrons into a configuration which is predominantly 3Pe, and then adding a p-wave positron. All the active particles are in states in which the relative angular momentum between any pair of particles is at least L=1. The LiPs state is Borromean since there are no three-body bound subsystems (of the correct symmetry) of the (Li+, e-, e-, e+) particles that make up the system. The dominant decay mode of these states will be radiative decay into a configuration that autoionizes or undergoes positron annihilation

  6. Spin-orbit effects in aluminum photoionization

    International Nuclear Information System (INIS)

    The eigenchannel R-matrix approach, in conjunction with the multichannel quantum-defect theory and the LS→jj recoupling frame transformation, is used to calculate the photoionization spectrum of Al I below the 3s3p 1Po ionization threshold (photon energies in the range 0.44≤ℎω≤0.98 Ry). Relativistic channel mixing is incorporated in the calculations by a recoupling frame transformation and by the inclusion of experimental fine-structure threshold energies. This mixing enables autoionization of resonances whose decay would otherwise be forbidden in the pure LS-coupling scheme. The calculated J-dependent energies and widths agree well with those of experimental resonances. The complicated relativistic spectrum, with up to 11 interacting channels, provides an experimentally realizable testing ground for studies of statistical properties of resonances. The spectrum below the 3s3p 3Po ionization threshold exhibits the Wigner and Porter-Thomas distributions of positions and widths of resonances, respectively. While portions of the aluminum spectrum appear to be random, according to these measures, there remains much underlying regularity in the level spacing and width distributions

  7. Low-energy photodetachment of O-

    International Nuclear Information System (INIS)

    The B-spline R-matrix method is used to investigate the low-energy photodetachment of O-(2p5) for photon energies from threshold to 7 eV. We report a detailed study regarding the dependence of the predicted partial and total photodetachment cross sections on the scattering model and the accuracy of the target description. A multiconfiguration Hartree-Fock method with nonorthogonal term-dependent orbitals is employed to generate accurate representations of the target wave functions. Four close-coupling scattering models with a different number of target states in the expansion are used to explore the dependence of the calculated photodetachment cross sections on the polarization of the target. Our largest model for the e-O collision problem in the final state includes 60 states, namely 25 bound and autoionizing states of neutral oxygen derived from the 1s22s22p4, 2s22p3nl, and 2s2p5 configurations, plus a set of pseudostates to partially account for the polarizability of the ground state 2p43P and the metastable 2p41D and 1S states. We only find a small dependence of the calculated photodetachment cross section on the amount of target polarization accounted for, but a very strong dependence of the near-threshold results on the degree of short-range inner-core correlation incorporated in the target description

  8. Development of a multipurpose beam foil spectroscopy set-up for the low cross-section measurements

    Science.gov (United States)

    Sharma, Gaurav; Nandi, T.; Berry, H. G.; Puri, Nitin K.

    2016-08-01

    A multipurpose facility for low cross section measurements has been developed at Inter University Accelerator Centre, New Delhi, India. The facility consists of a multipurpose miniature chamber equipped with 1 m focal length normal incidence Monochromator and charge coupled device based detection system which has been aligned to realize the best resolution of the spectrometer. The chamber in this facility collects radiation 100 times more efficiently from the older system, without using any extra focusing mirror assembly. It is ensured to have the provision of mounting an X-ray detector and the spectrometer transverse to the beam direction simultaneously in the same chamber. The atomic spectroscopic studies can be performed by interaction of ions beams with both thin foil and gas targets. Provision for using photomultiplier tube instead of charge coupled device, is employed in the system depending on the condition of the source strength or other detection issues. We observed the essence of a very weak atomic phenomenon, a triply excited autoionizing forbidden transition, using the above facility to demonstrate its capability for measuring such low cross section phenomena. The present developed facility covers a large spectroscopic region from X-rays to the near infrared (0.1-10,000 Å).

  9. The Spectr-W3 database on the spectroscopic properties of atoms and ions

    Science.gov (United States)

    Skobelev, I. Yu.; Loboda, P. A.; Gagarin, S. V.; Ivliev, S. V.; Kozlov, A. I.; Morozov, S. V.; Pikuz, S. A.; Pikuz, T. A.; Popova, V. V.; Faenov, A. Ya.

    2016-04-01

    The Spectr-W3 database was developed in 2001-2013 and is available online (http://spectrw3. snz.ru). The database contains information on various spectroscopic constants of atoms and ions such as the wavelengths and probabilities of radiative transitions, energy levels of atoms and ions, ionization potentials, autoionization rates, and the parameters of analytical approximation of cross sections and rates of collisional transitions in atoms and ions. Spectr-W3 presently contains around 450 thousand records and is the world's largest factual database on spectral properties of multicharged ions. A new stage of development of Spectr-W3, which involves adding a new section titled "Emission Spectrograms" to the database, commenced in 2014. In contrast to the already existing sections that contain tabulated data, this new section provides graphical data (with necessary explanatory notes) on the spectrograms of emission of atoms and ions excited in various plasma sources. The structure of sections of the Spectr-W3 database is characterized, and examples of queries and the corresponding search results are given.

  10. Anomalous dispersions of `hedgehog' particles

    Science.gov (United States)

    Bahng, Joong Hwan; Yeom, Bongjun; Wang, Yichun; Tung, Siu On; Hoff, J. Damon; Kotov, Nicholas

    2015-01-01

    Hydrophobic particles in water and hydrophilic particles in oil aggregate, but can form colloidal dispersions if their surfaces are chemically camouflaged with surfactants, organic tethers, adsorbed polymers or other particles that impart affinity for the solvent and increase interparticle repulsion. A different strategy for modulating the interaction between a solid and a liquid uses surface corrugation, which gives rise to unique wetting behaviour. Here we show that this topographical effect can also be used to disperse particles in a wide range of solvents without recourse to chemicals to camouflage the particles' surfaces: we produce micrometre-sized particles that are coated with stiff, nanoscale spikes and exhibit long-term colloidal stability in both hydrophilic and hydrophobic media. We find that these `hedgehog' particles do not interpenetrate each other with their spikes, which markedly decreases the contact area between the particles and, therefore, the attractive forces between them. The trapping of air in aqueous dispersions, solvent autoionization at highly developed interfaces, and long-range electrostatic repulsion in organic media also contribute to the colloidal stability of our particles. The unusual dispersion behaviour of our hedgehog particles, overturning the notion that like dissolves like, might help to mitigate adverse environmental effects of the use of surfactants and volatile organic solvents, and deepens our understanding of interparticle interactions and nanoscale colloidal chemistry.

  11. Electronic Structure of Helium Atom in a Quantum Dot

    Science.gov (United States)

    Jayanta, K. Saha; Bhattacharyya, S.; T. K., Mukherjee

    2016-03-01

    Bound and resonance states of helium atom have been investigated inside a quantum dot by using explicitly correlated Hylleraas type basis set within the framework of stabilization method. To be specific, precise energy eigenvalues of bound 1sns (1Se) (n = 1-6) states and the resonance parameters i.e. positions and widths of 1Se states due to 2sns (n = 2-5) and 2pnp (n = 2-5) configurations of confined helium below N = 2 ionization threshold of He+ have been estimated. The two-parameter (Depth and Width) finite oscillator potential is used to represent the confining potential due to the quantum dot. It has been explicitly demonstrated that the electronic structural properties become sensitive functions of the dot size. It is observed from the calculations of ionization potential that the stability of an impurity ion within a quantum dot may be manipulated by varying the confinement parameters. A possibility of controlling the autoionization lifetime of doubly excited states of two-electron ions by tuning the width of the quantum cavity is also discussed here. TKM Gratefully Acknowledges Financial Support under Grant No. 37(3)/14/27/2014-BRNS from the Department of Atomic Energy, BRNS, Government of India. SB Acknowledges Financial Support under Grant No. PSW-160/14-15(ERO) from University Grants Commission, Government of India

  12. X-ray fluorescence spectrum of highly charged Fe ions driven by strong free-electron-laser fields

    Science.gov (United States)

    Oreshkina, Natalia S.; Cavaletto, Stefano M.; Keitel, Christoph H.; Harman, Zoltán

    2016-05-01

    The influence of nonlinear dynamical effects is analyzed on the observed spectra of controversial 3C and 3D astrophysically relevant x-ray lines in neonlike Fe{}16+ and the A, B, and C lines in natriumlike Fe{}15+ ions. First, a large-scale configuration-interaction calculation of oscillator strengths is performed with the inclusion of higher-order electron-correlation effects. Also, quantum-electrodynamic corrections to the transition energies are calculated. Further considered dynamical effects provide a possible resolution of the discrepancy between theory and experiment found by recent x-ray free-electron-laser measurements of these controversial lines. We find that, for strong x-ray sources, the modeling of the spectral lines by a peak with an area proportional to the oscillator strength is not sufficient and nonlinear dynamical effects have to be taken into account. Thus, we advocate the use of light–matter-interaction models also valid for strong light fields in the analysis and interpretation of the associated astrophysical and laboratory spectra. We investigate line-strength ratios distinguishing between the coherent and incoherent parts of the emission spectrum. In addition, the spectrum of Fe{}15+, an autoionizing ion which was also present in the recent laboratory experiment, is analyzed as well.

  13. Electron capture and fragmentation in Ar11+ + CO collisions

    International Nuclear Information System (INIS)

    Collisions between 3, 10, and 50 keV/q Ar11+ ions and CO molecules have been studied using the Macdonald Lab CRYEBIS. Coincidence time of flight was used to detect all recoil ions and a position sensitive detector was used to determine final projectile charge states. Single- and double-electron capture are much larger than ionization at these collision energies. The dominant recoil channel associated with the Ar10+ final state is the CO+ molecular ion. The main ion-pair channel is the C+ + O+ dissociation of CO2+ while higher charge states of the transient COq+ fall off rapidly. Charge states up to CO4+ are formed in the collision indicating that many electrons are captured, but only one (and sometimes two) is retained by the projectile. This is due to autoionization of the highly excited states occupied by the captured electrons. In general, the fragmentation pattern of the CO molecule resembles the fragmentation associated with ionization caused by fast highly charged ions. This is as expected, since both processes happen at large impact parameters

  14. Study of isotopic selectivity in laser resonance ionization of lutetium atom

    International Nuclear Information System (INIS)

    Using numerical simulation method in terms of rate equation approximation, laser-induced isotopic selectivity of the scheme of resonance ionization: 5d6s22D3/2(573.655 nm)→5d6s6p 4F3/2 (642.518 nm)→6s6p24P1/2(643.548 nm)→Autoionization state was studied. The function of isotopic selectivity on laser wavelength was calculated for the parameters matching real experimental conditions by this method. The results calculated were well met with the experimental. The dependences of laser-induced isotopic selectivity on the laser parameters, such as wavelength, bandwidth and intensity, were discussed in view of the interaction of linearly polarized light with lutetium atom. The approaches that isotopic ratio were accurately determined by laser resonance ionization mass spectrometry in the case of certain laser parameters were presented. This theoretical method may be also used to study the isotopic selectivity of other elements and select the scheme of resonance ionization of laser isotope separation

  15. Resonant Ionization Laser Ion Source (RILIS) off-line developments on Ga, Al and Ca

    International Nuclear Information System (INIS)

    The Resonant Ionization Laser Ion Source (RILIS) is an element selective, highly efficient and versatile tool for generation of radioactive ion beams at on-line mass separator facilities. Parallel to TRIUMF’s on-line RILIS at the Isotope Separator and ACcelerator (ISAC) facility, an off-line Laser Ion Source test stand (LIS STAND) is operated for systematic laser resonance ionization spectroscopy, ionization scheme and ion source development. Three titanium sapphire (Ti:Sa) lasers optionally equipped with harmonic frequency generation units are used to resonantly step-wise excite and ionize elements of interest. A grating tuned Ti:Sa laser allows continuous laser wavelength scans of up to Δ≈200nm. With this laser inventory and the LIS STAND, atomic Rydberg series and auto-ionizing levels can systematically be studied. The LIS STAND has been in use since 2009 and so far the spectroscopy on Ga, Al and Ca has been performed. The development of efficient laser resonant ionization schemes, their investigation and comparison using the LIS STAND are discussed

  16. Resonance ionization spectroscopy of thorium isotopes-towards a laser spectroscopic identification of the low-lying 7.6 eV isomer of 229Th

    International Nuclear Information System (INIS)

    In-source resonance ionization spectroscopy was used to identify an efficient and selective three-step excitation/ionization scheme of thorium, suitable for titanium:sapphire (Ti:sa) lasers. The measurements were carried out in the preparation of laser spectroscopic investigations for an identification of the low-lying 229mTh isomer predicted at 7.6 ± 0.5 eV above the nuclear ground state. Using a sample of 232Th, a multitude of optical transitions leading to over 20 previously unknown intermediate states of even parity as well as numerous high-lying odd parity auto-ionizing (AI) states were identified. Level energies were determined with an accuracy of 0.06 cm-1 for intermediate and 0.15 cm-1 for AI states. Using different excitation pathways, an assignment of total angular momenta for several energy levels was possible. One particularly efficient ionization scheme of thorium, exhibiting saturation in all three optical transitions, was studied in detail. For all three levels in this scheme, the isotope shifts of the isotopes 228Th, 229Th and 230Th relative to 232Th were measured. An overall efficiency including ionization, transport and detection of 0.6% was determined, which was predominantly limited by the transmission of the mass spectrometer ion optics.

  17. Resonance ionization spectroscopy of thorium isotopes-towards a laser spectroscopic identification of the low-lying 7.6 eV isomer of {sup 229}Th

    Energy Technology Data Exchange (ETDEWEB)

    Raeder, S; Sonnenschein, V; Gottwald, T; Rothe, S; Wendt, K [Institute of Physics, University of Mainz, Staudingerweg 7, 55128 Mainz (Germany); Moore, I D; Reponen, M [Department of Physics, University of Jyvaeskylae, Survontie 9, 40014 Jyvaeskylae (Finland); Trautmann, N, E-mail: raeder@uni-mainz.de, E-mail: volker.t.sonnenschein@jyu.fi [Institute of Nuclear Chemistry, University of Mainz, Fritz-Strassmann-Weg 2, 55128 Mainz (Germany)

    2011-08-28

    In-source resonance ionization spectroscopy was used to identify an efficient and selective three-step excitation/ionization scheme of thorium, suitable for titanium:sapphire (Ti:sa) lasers. The measurements were carried out in the preparation of laser spectroscopic investigations for an identification of the low-lying {sup 229m}Th isomer predicted at 7.6 {+-} 0.5 eV above the nuclear ground state. Using a sample of {sup 232}Th, a multitude of optical transitions leading to over 20 previously unknown intermediate states of even parity as well as numerous high-lying odd parity auto-ionizing (AI) states were identified. Level energies were determined with an accuracy of 0.06 cm{sup -1} for intermediate and 0.15 cm{sup -1} for AI states. Using different excitation pathways, an assignment of total angular momenta for several energy levels was possible. One particularly efficient ionization scheme of thorium, exhibiting saturation in all three optical transitions, was studied in detail. For all three levels in this scheme, the isotope shifts of the isotopes {sup 228}Th, {sup 229}Th and {sup 230}Th relative to {sup 232}Th were measured. An overall efficiency including ionization, transport and detection of 0.6% was determined, which was predominantly limited by the transmission of the mass spectrometer ion optics.

  18. Principle and analytical applications of resonance ionization mass spectrometry

    International Nuclear Information System (INIS)

    Resonance ionization mass spectrometry (RIMS) is a very sensitive analytical technique for the detection of trace elements. This method is based on the excitation and ionization of atoms with resonant laser light followed by mass analysis. It allows element and, in some cases, isotope selective ionization and is applicable to most of the elements of the periodic table. A high selectivity can be achieved by applying three step photoionization of the elements under investigation and an additional mass separation for an unambiguous isotope assignment. An effective facility for resonance ionization mass spectrometry consists of three dye lasers which are pumped by two copper vapor lasers and of a linear time-of-flight spectrometer with a resolution better than 2500. Each copper vapor laser has a pulse repetition rate of 6,5 kHz and an average output power of 30 W. With such an apparatus measurements with lanthanide-, actinide-, and technetium-samples have been performed. By saturating the excitation steps and by using autoionizing states for ionization step a detection efficiency of 4 x 10-6 and 2,5 x 10-6 has been reached for plutonium and technetium, respectively, leading to a detection limit of less than 107 atoms in the sample. Measurements of isotope ratios of plutonium samples were in good agreement with mass-spectrometric data. The high elemental selectivity of the resonance ionization spectrometry could be demonstrated. (Authors)

  19. Resonance ionization spectroscopy of thorium isotopes-towards a laser spectroscopic identification of the low-lying 7.6 eV isomer of 229Th

    Science.gov (United States)

    Raeder, S.; Sonnenschein, V.; Gottwald, T.; Moore, I. D.; Reponen, M.; Rothe, S.; Trautmann, N.; Wendt, K.

    2011-08-01

    In-source resonance ionization spectroscopy was used to identify an efficient and selective three-step excitation/ionization scheme of thorium, suitable for titanium:sapphire (Ti:sa) lasers. The measurements were carried out in the preparation of laser spectroscopic investigations for an identification of the low-lying 229mTh isomer predicted at 7.6 ± 0.5 eV above the nuclear ground state. Using a sample of 232Th, a multitude of optical transitions leading to over 20 previously unknown intermediate states of even parity as well as numerous high-lying odd parity auto-ionizing (AI) states were identified. Level energies were determined with an accuracy of 0.06 cm-1 for intermediate and 0.15 cm-1 for AI states. Using different excitation pathways, an assignment of total angular momenta for several energy levels was possible. One particularly efficient ionization scheme of thorium, exhibiting saturation in all three optical transitions, was studied in detail. For all three levels in this scheme, the isotope shifts of the isotopes 228Th, 229Th and 230Th relative to 232Th were measured. An overall efficiency including ionization, transport and detection of 0.6% was determined, which was predominantly limited by the transmission of the mass spectrometer ion optics.

  20. Resonance Ionization Mass Spectrometry (RIMS) with Pulsed and CW-Lasers on Plutonium

    Science.gov (United States)

    Kunz, P.; Huber, G.; Passler, G.; Trautmann, N.; Wendt, K.

    2005-04-01

    The detection of long-lived plutonium isotopes in ultra-trace amounts by resonance ionization mass spectrometry (RIMS) is a well-established routine method. Detection limits of 106 to 107 atoms and precise measurements of the isotopic composition have been achieved. In this work multi-step resonance ionization of plutonium atoms has been performed with tunable lasers having very different output intensities and spectral properties. In order to compare different ways for the resonance ionization of plutonium broadband pulsed dye and titanium:sapphire lasers as well as narrow-band cw-diode and titanium:sapphire lasers have been applied for a number of efficient excitation schemes. It has been shown, that for identical excitation schemes the optical isotope selectivity can be improved by using cw-lasers (bandwidths lasers (bandwidths > 2 GHz). Pulsed and cw-laser systems have been used simultaneously for resonance ionization enabling direct comparisons of pulsed and continuous ionization processes. So far, a three-step, three-color laser excitation scheme has been proven to be most practical in terms of efficiency, selectivity and laser wavelengths. Alternatively a newly discovered three-step, two-color excitation scheme which includes a strong two-photon transition from an excited state into a high-lying autoionizing state yields similar ionization efficiencies. This two-photon transition was characterized with respect to saturation behavior and line width.

  1. Trace determination of gadolinium in biomedical samples by diode laser-based multi-step resonance ionization mass spectrometry.

    Science.gov (United States)

    Blaum, K; Geppert, C; Schreiber, W G; Hengstler, J G; Müller, P; Nörtershäuser, W; Wendt, K; Bushaw, B A

    2002-04-01

    The application of high-resolution multi-step resonance ionization mass spectrometry (RIMS) to the trace determination of the rare earth element gadolinium is described. Utilizing three-step resonant excitation into an autoionizing level, both isobaric and isotopic selectivity of >10(7) were attained. An overall detection efficiency of approximately 10(-7) and an isotope specific detection limit of 1.5 x 10(9) atoms have been demonstrated. When targeting the major isotope (158)Gd, this corresponds to a total Gd detection limit of 1.6 pg. Additionally, linear response has been demonstrated over a dynamic range of six orders of magnitude. The method has been used to determine the Gd content in various normal and tumor tissue samples, taken from a laboratory mouse shortly after injection of gadolinium diethylenetriaminepentaacetic acid dimeglumine (Gd-DTPA), which is used as a contrast agent for magnetic resonance imaging (MRI). The RIMS results show Gd concentrations that vary by more than two orders of magnitude (0.07-11.5 microg mL(-1)) depending on the tissue type. This variability is similar to that observed in MRI scans that depict Gd-DTPA content in the mouse prior to dissection, and illustrates the potential for quantitative trace analysis in microsamples of biomedical materials. PMID:12012186

  2. In-Source Laser Resonance Ionization at ISOL Facilities

    CERN Document Server

    Marsh, Bruce; Feddosseev, Valentin

    Resonance ionization laser ion source development has been carried out at two radioactive ion beam facilities: ISOLDE (CERN, Switzerland) and the IGISOL facility (Jyvaskyla, Finland). The scope of the Resonance Ionization Laser Ion Source has been extended to 27 elements with the development of new three-step ionization schemes for Sb, Sc, Dy, Y and Au. The efficiencies were determined to be in the range of 2 - 20 %. Additionally, a new two-step ionization scheme has been developed for bismuth in an off-line atomic beam unit. The scheme relies on ionization via a strong and broad auto-ionizing resonance at an energy of 63196.79 cm$^{−1}$. This scheme may offer an improvement over the existing RILIS efficiency and will be more convenient for use during resonance ionization spectroscopy of Bi isotopes. The RILIS can be used as a spectroscopic tool to probe features such as the hyperfine structures and the isotope-shifts of radioisotopes with low production rates. By coupling a laser scanning process that dire...

  3. Gadolinium trace determination in biomedical samples by diode-laser-based multi-step resonance ionization mass spectrometry

    International Nuclear Information System (INIS)

    Diode laser based multi-step resonance ionization mass spectrometry (RIMS), which has been developed primarily for ultra trace analysis of long lived radioactive isotopes has been adapted for the application to elements within the sequence of the rare earths. First investigations concern Gd isotopes. Here high suppression of isobars, as provided by RIMS, is mandatory. Using a three step resonant excitation scheme into an autoionizing state, which has been the subject of preparatory spectroscopic investigations, high efficiency of >1x10-6 and good isobaric selectivity >107 was realized. Additionally the linearity of the method has been demonstrated over six orders of magnitude. Avoiding contaminations from the Titanium-carrier foil resulted in a suppression of background of more than one order of magnitude and a correspondingly low detection limit of 4x109 atoms, equivalent to lpg of Gd. The technique has been applied for trace determination of the Gd-content in animal tissue. Bio-medical micro samples were analyzed shortly after Gd-chelat, which is used as the primary contrast medium for magnetic resonance imaging (MRI) in biomedical investigations, has been injected. Correlated in-vivo magnetic resonance images have been taken. The RIMS measurements show high reproducibility as a well as good precision, and contribute to new insight into the distribution and kinetics of Gd within different healthy and cancerous tissues

  4. Resonance Ionization Mass Spectrometry (RIMS) with Pulsed and CW-Lasers on Plutonium

    International Nuclear Information System (INIS)

    The detection of long-lived plutonium isotopes in ultra-trace amounts by resonance ionization mass spectrometry (RIMS) is a well-established routine method. Detection limits of 106 to 107 atoms and precise measurements of the isotopic composition have been achieved. In this work multi-step resonance ionization of plutonium atoms has been performed with tunable lasers having very different output intensities and spectral properties. In order to compare different ways for the resonance ionization of plutonium broadband pulsed dye and titanium:sapphire lasers as well as narrow-band cw-diode and titanium:sapphire lasers have been applied for a number of efficient excitation schemes. It has been shown, that for identical excitation schemes the optical isotope selectivity can be improved by using cw-lasers (bandwidths 2 GHz). Pulsed and cw-laser systems have been used simultaneously for resonance ionization enabling direct comparisons of pulsed and continuous ionization processes. So far, a three-step, three-color laser excitation scheme has been proven to be most practical in terms of efficiency, selectivity and laser wavelengths. Alternatively a newly discovered three-step, two-color excitation scheme which includes a strong two-photon transition from an excited state into a high-lying autoionizing state yields similar ionization efficiencies. This two-photon transition was characterized with respect to saturation behavior and line width.

  5. Experimental studies on selective photoionization scheme of 152Sm

    International Nuclear Information System (INIS)

    We investigated the selective photoionization scheme of 152Sm by three- color, three-step ionization. The first resonant step was fixed at well-known transition from the ground state [4f66s2] 7F1 ro the state [4f66s6p] 7F20 of which wavelength is 591.635 nm. The second laser was scanned in the range 550 nm-600 nm to observe even-parity states accessible from the [4f66s6p] 7F20 state. Forty-two states were observed and their isotope shifts were measured by three-step resonant ionization. Considering the measured data, we could determined the second resonant step with large isotope shifts. Additionally, an autoionization state with large photoionization cross-section was found. Using a time of flight mass spectrometer, we measured the ion yield and the selectivity of 152Sm. When the selected 3-color photoionization scheme was used, the high selective ionization of 152Sm was achieved.

  6. Resonance ionization spectroscopy of thorium isotopes-towards a laser spectroscopic identification of the low-lying 7.6 eV isomer of (229)Th

    CERN Document Server

    Raeder, S; Wendt, K; Sonnenschein, V; Trautmann, N; Rothe, S; Reponen, M; Gottwald, T

    2011-01-01

    In-source resonance ionization spectroscopy was used to identify an efficient and selective three-step excitation/ionization scheme of thorium, suitable for titanium: sapphire (Ti:sa) lasers. The measurements were carried out in the preparation of laser spectroscopic investigations for an identification of the low-lying (229m)Th isomer predicted at 7.6 +/- 0.5 eV above the nuclear ground state. Using a sample of (232)Th, a multitude of optical transitions leading to over 20 previously unknown intermediate states of even parity as well as numerous high-lying odd parity auto-ionizing (AI) states were identified. Level energies were determined with an accuracy of 0.06 cm(-1) for intermediate and 0.15 cm(-1) for AI states. Using different excitation pathways, an assignment of total angular momenta for several energy levels was possible. One particularly efficient ionization scheme of thorium, exhibiting saturation in all three optical transitions, was studied in detail. For all three levels in this scheme, the is...

  7. Laser spectroscopy of multi-level doppler broadened atomic system

    International Nuclear Information System (INIS)

    Doppler broadened atomic vapor system can be easily prepared for spectroscopy study than an atomic beam system can be. Vapor cell and hollow cathode discharge lamps are widely used in the experiment. The possibility for observing the trapped state in a Doppler broadened Λ system was examined and confirmed by our early experiment where counter-propagating laser beams are used. For the measurement of the hyperfine structure constants of high-lying levels of heavy elements, we compared the co-propagating and counter-propagating beams in a Doppler broadened ladder systems. It was shown that the counter-propagating beams give a stronger and narrower signal than that from the co-propagating beams. Our treatment also considers the power broadening of the transition. For some photo-ionization experiments, it is necessary to pump two thermally populated levels simultaneously to the higher level and then to the auto-ionizing levels. A technique is proposed to avoid the trapped state and to increase the ionization efficiency.

  8. A test stand for off-line laser ion source development at TRIUMF

    International Nuclear Information System (INIS)

    A test stand for ion source development and laser resonance ionization spectroscopy was built and commissioned at TRIUMF. The test stand is needed to develop efficient ion sources that can function reliably in the hostile, high temperature, high radiation environment of TRIUMF's isotope separator on-line (ISOL) production target ion source. In addition, it enables laser resonance ionization spectroscopy to develop laser excitation schemes suitable for the solid-state laser systems used with TRIUMF's resonant ionization laser ion source . Also, it allows for possible improvement of current ion sources and validation of new designs. The test stand employs a copy of the ion optics used on-line, so that results can be transferred directly to radioactive ion beam production. Due to space restrictions and the need for rapid mass scans, a quadrupole mass spectrometer is used as a mass separator. One of the first experiments conducted on the laser ion source test stand (LIS STAND) was resonant ionization spectroscopy of gallium to improve on the ionization scheme previously used on-line, so that low yield isotopes (e.g., 62Ga) become available for experiments. Different Rydberg series in gallium were observed and autoionizing states were searched for. The overall LIS STAND system performance, characteristics, and the first resonant ionization spectroscopy are described.

  9. Charge symmetric dissociation of doubly ionized N{sub 2} and CO molecules

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, A., E-mail: amrendra@prl.res.in; Bapat, B. [Physical Research Laboratory, Ahmedabad 380009 (India); Shamasundar, K. R. [Indian Institute of Science Education and Research, Mohali, Sector 81, SAS Nagar 140306 (India)

    2014-01-21

    We report a comparative study of the features in dissociative double ionization by high energy electron impact of N{sub 2} and CO molecules. The ratio of cross-section of charge symmetric dissociative ionization to non-dissociative ionization (CSD-to-ND ratio) and the kinetic energy release (KER) spectra of dissociation are experimentally measured and carefully corrected for various ion transmission losses and detector inefficiencies. Given that the double ionization cross sections of these iso-electronic diatomics are very similar, the large difference in the CSD-to-ND ratios must be attributable to the differences in the evolution dynamics of the dications. To understand these differences, potential energy curves (PECs) of dications have been computed using multi-reference configuration interaction method. The Franck-Condon factors and tunneling life times of vibrational levels of dications have also been computed. While the KER spectrum of N{sub 2}{sup ++} can be readily explained by considering dissociation via repulsive states and tunneling of meta-stable states, indirect dissociation processes such as predissociation and autoionization have to be taken into account to understand the major features of the KER spectrum of CO{sup ++}. Direct and indirect processes identified on the basis of the PECs and experimental KER spectra also provide insights into the differences in the CSD-to-ND ratios.

  10. Investigation into four-stage scheme of separation of ytterbium isotopes by laser radiation

    International Nuclear Information System (INIS)

    A scheme of four-stage selective photoionization (SPI) of ytterbium atoms with photoionization from a higher state by means of CO2 laser radiation was suggested and theoretically investigated. Two versions of the scheme of laser four-stage SPI of Yb atoms are presented. In both cases the first two stages are related to excitation of the 4f146s6p-3P10 and 4f166s7s-3S1 states. The third excitation stage in the first scheme transfers Yb atoms to the Rydberg 4f146s20p-3P1 state and in the second scheme - to the 4f135d26s-1P10 state. The last, fourth stage transfers an atom to the autoionization state. The four-stage scheme of Yb atom SPI was calculated with the use of the density matrix apparatus. The suggested scheme can be used for commercial production of 168Yb isotope. Production of 168Yb equals 2.6 mg/h can be expected on the basis of conducted calculations at the 1014 cm-3 atom density in a beam

  11. Study of attosecond delays using perturbation diagrams and exterior complex scaling

    International Nuclear Information System (INIS)

    We describe in detail how attosecond delays in laser-assisted photoionization can be computed using perturbation theory based on two-photon matrix elements. Special emphasis is laid on above-threshold ionization, where the electron interacts with an infrared field after photoionization by an extreme ultraviolet field. Correlation effects are introduced using diagrammatic many-body theory to the level of the random-phase approximation with exchange. Our aim is to provide an ab initio route to correlated multi-photon processes that are required for an accurate description of experiments on the attosecond time scale. Here, our results are focused on photoionization of the M-shell of argon atoms, where experiments have been carried out using the so-called reconstruction of attosecond beating by the two-photon interference transitions technique. An influence of autoionizing resonances in attosecond delay measurements is observed. Further, it is shown that the delay depends on both detection angle of the photoelectron and energy of the probe photon. (paper)

  12. Dielectronic recombination of Xe10+ ions and satellite line of Xe9+ ions

    International Nuclear Information System (INIS)

    EUV light sources from compact plasmas are now intensively studied for the next generation of lithography. The multicharged Xe ions emit EUV emission and are now investigated extensively. However we do not know the detailed atomic processes for the Xe ions. We study in this paper on dielectronic and radiative recombination processes of Xe ions. We have calculated the energy levels, radiative transition probabilities (Ar), autoionization rates (Aa), and radiative recombination cross section for Xe10+ ions using the FAC code. The dielectronic recombination rate coefficient (αDR) from the Xe10+ ions and the related dielectronic satellite lines are obtained. We studied the n- and 1-dependence for Ar, Aa, dielectronic recombination rate coefficient (αDR), and radiative recombination rate coefficient (Krr). The dielectronic recombination processes from the 4d8+e→4d74f1nl→4d8nl+hν and the 4d8+e→4d75p1nl→4d8nl+hν become important at low plasma temperature Te≅10eV for line intensities. Also, the radiative recombination rate coefficient is smaller than the values of the dielectronic recombination processes in our interested temperature region at Te=1eV - 1000eV. (author)

  13. Systematic search of excited states of negative ions lying above the ground state of the neutral atom

    International Nuclear Information System (INIS)

    Nonrelativistic fixed-core valence-shell configuration interaction calculations are carried out for excited states of atomic negative ions in the range H through Ca, in an effort to identify the ones which are metastable against autoionization. Approximate relativistic corrections are included in some cases. From Be onwards, all (Core)sub(n)(n + 1)ssup(q)(n + 1)psup(r) neutrals appear to bind an extra electron into a bound (Core)sub(n)(n + 1)ssup(q)(n + 1)psup(r+1 2 + 1)L negative ion, in all cases where the sup(2S + 1)L continuum starts at the corresponding neutral atom state. Similarly as in the recently discussed case of Li-, alkali-earths (Be-, Mg-, Ca-), Zn-, B-, Al-, C-, Si-, Ar-, and possibly S-, have two bound excited states connected by an E1 transition in regions extending from infrared to vacuum ultraviolet. Negative neon is found to decay by E1 radiation into a continuum, thus Ne- beams are unlikely to be made in the future. However, there exists a metastable [Ne]3p54s4p 4S state of negative argon, making possible the production of Ar- beams. (orig.)

  14. Systematic search of excited states of negative ions lying above the ground state of the neutral atom

    Energy Technology Data Exchange (ETDEWEB)

    Bunge, C.F.; Galan, M.; Jauregui, R. (Universidad Nacional Autonoma de Mexico, Mexico City. Inst. de Fisica); Bunge, A.V. (Universidad Autonoma Metropolitana, Mexico City. Dept. de Quimica)

    1982-11-01

    Nonrelativistic fixed-core valence-shell configuration interaction calculations are carried out for excited states of atomic negative ions in the range H through Ca, in an effort to identify the ones which are metastable against autoionization. Approximate relativistic corrections are included in some cases. From Be onwards, all (Core)sub(n)(n + 1)ssup(q)(n + 1)psup(r) neutrals appear to bind an extra electron into a bound (Core)sub(n)(n + 1)ssup(q)(n + 1)psup(r+1 2 + 1)L negative ion, in all cases where the sup(2S + 1)L continuum starts at the corresponding neutral atom state. Similarly as in the recently discussed case of Li/sup -/, alkali-earths (Be/sup -/, Mg/sup -/, Ca/sup -/), Zn/sup -/, B/sup -/, Al/sup -/, C/sup -/, Si/sup -/, Ar/sup -/, and possibly S/sup -/, have two bound excited states connected by an E1 transition in regions extending from infrared to vacuum ultraviolet. Negative neon is found to decay by E1 radiation into a continuum, thus Ne/sup -/ beams are unlikely to be made in the future. However, there exists a metastable (Ne)3p/sup 5/4s4p /sup 4/S state of negative argon, making possible the production of Ar/sup -/ beams.

  15. R-matrix calculations for electron impact excitation of Fe II: LS coupling and Breit-Pauli approximations

    International Nuclear Information System (INIS)

    Two sets of close coupling calculations have been carried out on the Cray-2 and the Cray Y-MP using the R-matrix method: (i) a 38-term calculation in LS coupling and (ii) a 41-level fine structure calculation in the Breit-Pauli approximation. The first set includes the quartet and sextet terms dominated by the configurations 3d64s, 3d7 and 3d6 4p and collision strengths are calculated for all 703 transitions in LS coupling. The second set of calculations is carried out using the Breit-Pauli version of the R-matrix method and includes a number of important fine structure levels from the quartet and the sextet multiplets and 820 corresponding transitions. Detailed autoionization structures are obtained in both sets of collision strengths, and a significant enhancement is seen in the effective collision strengths for a number of transitions due to the resonances: for example, an enhancement of factors of 1.4, 2.5 and 1.15 respectively for transitions from the 6D ground term to the lowest 4F, 4D and 4P terms. (author)

  16. Using the charge-stabilization technique in the double ionization potential equation-of-motion calculations with dianion references.

    Science.gov (United States)

    Kuś, Tomasz; Krylov, Anna I

    2011-08-28

    The charge-stabilization method is applied to double ionization potential equation-of-motion (EOM-DIP) calculations to stabilize unstable dianion reference functions. The auto-ionizing character of the dianionic reference states spoils the numeric performance of EOM-DIP limiting applications of this method. We demonstrate that reliable excitation energies can be computed by EOM-DIP using a stabilized resonance wave function instead of the lowest energy solution corresponding to the neutral + free electron(s) state of the system. The details of charge-stabilization procedure are discussed and illustrated by examples. The choice of optimal stabilizing Coulomb potential, which is strong enough to stabilize the dianion reference, yet, minimally perturbs the target states of the neutral, is the crux of the approach. Two algorithms of choosing optimal parameters of the stabilization potential are presented. One is based on the orbital energies, and another--on the basis set dependence of the total Hartree-Fock energy of the reference. Our benchmark calculations of the singlet-triplet energy gaps in several diradicals show a remarkable improvement of the EOM-DIP accuracy in problematic cases. Overall, the excitation energies in diradicals computed using the stabilized EOM-DIP are within 0.2 eV from the reference EOM spin-flip values. PMID:21895161

  17. Theoretical methods for attosecond electron and nuclear dynamics: applications to the H2 molecule

    Science.gov (United States)

    Palacios, Alicia; Sanz-Vicario, José Luis; Martín, Fernando

    2015-12-01

    Attosecond science, born at the beginning of this century with the generation of the first bursts of light with durations shorter than a femtosecond, has opened the way to look at electron dynamics in atoms and molecules at its natural timescale. Thus controlling chemical reactions at the electronic level or obtaining time-resolved images of the electronic motion has become a goal for many physics and chemistry laboratories all over the world. The new experimental capabilities have spurred the development of sophisticated theoretical methods that can accurately predict phenomena occurring in the sub-fs timescale. This review provides an overview of the capabilities of existing theoretical tools to describe electron and nuclear dynamics resulting from the interaction of femto- and attosecond UV/XUV radiation with simple molecular targets. We describe one of these methods in more detail, the time-dependent Feshbach close-coupling (TDFCC) formalism, which has been used successfully over the years to investigate various attosecond phenomena in the hydrogen molecule and can easily be extended to other diatomics. In addition to describing the details of the method and discussing its advantages and limitations, we also provide examples of the new physics that one can learn by applying it to different problems: from the study of the autoionization decay that follows attosecond UV excitation to the imaging of the coupled electron and nuclear dynamics in H2 using different UV-pump/IR-probe and UV-pump/UV-probe schemes.

  18. Threshold photoelectron spectroscopy of acetaldehyde and acrolein

    International Nuclear Information System (INIS)

    Highlights: •High-resolution threshold photoelectron spectrum of acetaldehyde. •High-resolution threshold photoelectron spectrum of acrolein. •High-resolution total photoion yield spectrum of acetaldehyde. •High-resolution total photoion yield spectrum of acrolein. •Determination of vertical ionization potentials in acetaldehyde and acrolein. -- Abstract: High-resolution (6 meV and 12 meV) threshold photoelectron (TPE) spectra of acetaldehyde and acrolein (2-propenal) have been recorded over the valence binding energy region 10–20 eV, employing synchrotron radiation and a penetrating-field electron spectrometer. These TPE spectra are presented here for the first time. All of the band structures observed in the TPE spectra replicate those found in their conventional HeI photoelectron (PE) spectra. However, the relative band intensities are found to be dramatically different in the two types of spectra that are attributed to the different dominant operative formation mechanisms. In addition, some band shapes and their vertical ionization potentials are found to differ in the two types of spectra that are associated with the autoionization of Rydberg states in the two molecules

  19. Threshold photoelectron spectroscopy of acetaldehyde and acrolein

    Energy Technology Data Exchange (ETDEWEB)

    Yencha, Andrew J., E-mail: ayencha@albany.edu [Department of Chemistry, University at Albany, State University of New York, Albany, NY 12222 (United States); Siggel-King, Michele R.F. [Cockcroft Institute, Sci-Tech Daresbury, Warrrington WA4 4AD (United Kingdom); Department of Physics, University of Liverpool, Liverpool L69 3BX (United Kingdom); King, George C. [Department of Physics and Astronomy and Photon Science Institute, Manchester University, Manchester M13 9PL (United Kingdom); Malins, Andrew E.R. [Cockcroft Institute, Sci-Tech Daresbury, Warrrington WA4 4AD (United Kingdom); Eypper, Marie [School of Chemistry, University of Southampton, Southampton SO17 1BJ (United Kingdom)

    2013-04-15

    Highlights: •High-resolution threshold photoelectron spectrum of acetaldehyde. •High-resolution threshold photoelectron spectrum of acrolein. •High-resolution total photoion yield spectrum of acetaldehyde. •High-resolution total photoion yield spectrum of acrolein. •Determination of vertical ionization potentials in acetaldehyde and acrolein. -- Abstract: High-resolution (6 meV and 12 meV) threshold photoelectron (TPE) spectra of acetaldehyde and acrolein (2-propenal) have been recorded over the valence binding energy region 10–20 eV, employing synchrotron radiation and a penetrating-field electron spectrometer. These TPE spectra are presented here for the first time. All of the band structures observed in the TPE spectra replicate those found in their conventional HeI photoelectron (PE) spectra. However, the relative band intensities are found to be dramatically different in the two types of spectra that are attributed to the different dominant operative formation mechanisms. In addition, some band shapes and their vertical ionization potentials are found to differ in the two types of spectra that are associated with the autoionization of Rydberg states in the two molecules.

  20. Elemental speciation of neptunium in ultra trace amount ranges; Elementspeziation von Neptunium im Ultraspurenbereich

    Energy Technology Data Exchange (ETDEWEB)

    Stoebener, Nils

    2013-06-25

    In the presented work, the detection of the isotope Np-237 with resonance ionization mass spectrometry (RIMS) was developed and optimized. In RIMS, sample atoms are excited and ionized with laser radiation in several, resonant steps and are subsequently detected by a mass spectrometer. Energy levels suitable for the excitation and ionization of Np-237 were identified using resonance ionization spectroscopy (RIS). With RIS, more than 300 previously unknown electronic states and autoionizing resonances of Np-237 were identified. Using in-source-RIMS, a limit of detection of 9E+5 atoms was demonstrated for the isotope. The mobility of Np in the environment strongly depends on its elemental speciation. Therefore, safety assessments of proposed nuclear waste repositories require analytical methods for the detection of Np species. CE (capillary electrophoresis) was hyphenated to ICP-MS (inductively coupled plasma mass spectrometry) to examine the distribution of the Np redox species Np(IV) and Np(V), which was possible at Np concentrations as low as 1E-9 mol/L. The method was used to study the interaction of the element with Opalinus Clay at varying conditions. CE-ICP-MS revealed, that under the presence of Fe(II), Np(V) is reduced to Np(IV), which is sorbed onto the clay. This leads to a higher overall Np sorption.

  1. Spaced resolved analysis of suprathermal electrons in dense plasma

    Directory of Open Access Journals (Sweden)

    Moinard A.

    2013-11-01

    Full Text Available The investigation of the hot electron fraction is a crucial topic for high energy density laser driven plasmas: first, energy losses and radiative properties depend strongly on the hot electron fraction and, second, in ICF hohlraums suprathermal electrons preheat the D-T-capsule and seriously reduce the fusion performance. In the present work we present our first experimental and theoretical studies to analyze single shot space resolved hot electron fractions inside dense plasmas via optically thin X-ray line transitions from autoionizing states. The benchmark experiment has been carried out at an X-pinch in order to create a dense, localized plasma with a well defined symmetry axis of hot electron propagation. Simultaneous high spatial and spectral resolution in the X-ray spectral range has been obtained with a spherically bent quartz Bragg crystal. The high performance of the X-ray diagnostics allowed to identify space resolved hot electron fractions via the X-ray spectral distribution of multiple excited states.

  2. A master equation approach to the dynamics of zero electron kinetic energy (ZEKE) states and ZEKE spectroscopy

    International Nuclear Information System (INIS)

    We have theoretically studied important dynamic processes involved in zero electron kinetic energy (ZEKE) spectroscopy using the density matrix method with the inverse Born-Oppenheimer approximation basis sets. In ZEKE spectroscopy, the ZEKE Rydberg states are populated by laser excitation (either a one- or two-photon process), which is followed by autoionizations and l-mixing due to a stray field. The discrimination field is then applied to ionize loosely bound electrons in the ZEKE states. This is followed by using the extraction field to extract electrons from the ZEKE levels which have a strength comparable to that of the extraction field. These extracted electrons are measured for the relative intensities of the ion states under investigation. The spectral positions are determined by the applied laser wavelength and modified by the extraction electric field. In this paper, all of these processes are conducted within the context of the density matrix method. The density matrix method can provide not only the dynamics of system's population and coherence (or phase) but also the rate constants of the processes involved in the ZEKE spectroscopy. Numerical examples are given to demonstrate the theoretical treatments.

  3. X-ray and inner-shell processes: Their impact on our understanding of atomic physics and atoms interacting with solids

    International Nuclear Information System (INIS)

    Atomic physics and the basic concepts of quantum theory have been probed in the last fifty years by using the techniques of optics and lasers in the visible range. The new powerful accelerators, storage rings, and various large scale devices, such as ion beams, synchrotron radiation, plasma confinement machines, powerful lasers, etc. developed by the nuclear physicists and high technology engineers have allowed, in the past three decades, new, unexpected and more general insights of atomic structure and more accurate checks of quantum mechanics. It is now possible to prepare any kind of atom or ion, having any number of electrons in any quantum states (atomic manipulations), and to trap or set them in defined places on surfaces. The study of these atomic species having electrons in any deep, or highly excited levels requires the use of electromagnetic transitions in a much wider range of wavelengths than in optics, and, because most of the time they are in autoionizing states, of Auger spectrometry. It is the purpose of this talk to review some of the most salient discoveries in the field since this time, to present some of the most recent and exciting results obtained in the last decade, and future prospects

  4. Photoionization cross section of Ne-like Cu XX with J=1

    International Nuclear Information System (INIS)

    Relativistic calculations of photoionization cross sections of Ne-like Cu XX using the Breit–Pauli R-matrix method in close-coupling approximation and fully relativistic distorted-wave method are reported. In the present work, the relativistic distorted-wave method is employed to calculate the fine-structure energy levels and radial functions, and the Breit–Pauli R-matrix method is employed to calculate photoionizaton cross section for photon energy from 124.2 Ryd to 208 Ryd. Resonance structure in the photoionization of Ne-like Cu XX for ejection of 2p or 2s electron from the ground 2s22p61S0 has been studied. -- Highlights: ► Photoionization cross sections of Cu XX are investigated using 11 target states. ► Radiative probabilities, line strength and oscillator strength are studied. ► Many new autoionizing energy levels have been calculated. ► The R-matrix method, distorted-wave method and QB method are used.

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

    Institute of Scientific and Technical Information of China (English)

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

    2009-01-01

    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(X, θe,φe)MFPADs.where X is the orientation of the molecular axis with respect to the light quantization axis and (θe,φe) 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 polarizcd light, are presented for dissociative photoionization (DPI) of D2 at two photon excitation energies, hv=19 eV, where direct PI is the only channel opened, and hv=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.

  6. Experimental and theoretical studies of metal vapor atoms

    International Nuclear Information System (INIS)

    Employing electron spectrometry in conjunction with tuneable synchrotron radiation, we will present a detailed examination of the photoionization dynamics of selected metal vapor atoms. In particular, this paper will focus on the relative partial cross sections of the atomic Li K-shell main and satellite (ionization with excitation) photoelectron lines in the region of the strong 1snln'l' autoionizing transitions, the atomic Sc 3d, 4s main and satellite photoelectron lines in the region of the 3p→3d giant resonance, and also the atomic Fe 3d, 4s main and satellite photoelectron lines in the same resonance region. Our experimental data for Sc and Fe will be compared to our state-of-the-art calculations based on the superposition of configuration method developed by Cowan (The Theory of Atomic Structure and Spectra. University of California Berkeley Press, Berkeley and Los Angeles, 1981). Our partial cross section measurements for Li and Sc will be complemented with measurements of the angular distribution parameter, β. In addition, our Li data will also be compared with recent R-matrix calculations (Phys. Rev. 57 (1998) 1045). In the case of Fe, we will also address the term dependent behavior of the partial cross sections on resonance. These results will highlight what can be achieved with today's technology and point the way towards future endeavors in the study of the photoionization dynamics of open-shell metal vapor atoms

  7. Postcollision interactions in the Auger decay of the Ar L-shell

    Energy Technology Data Exchange (ETDEWEB)

    Samson, J.A.R.; Stolte, W.C.; He, Z.X. [Univ. of Nebraska, Lincoln, NE (United States)] [and others

    1997-04-01

    The photoionization cross sections for Ar{sup +} through Ar{sup 4+}, produced by the Auger decay of an inner shell 2p hole, have been measured between 242 eV and 253 eV on beamline 9.0.1 and 6.3.2. In this study the authors are interested in near threshold phenomenon involving postcollision interactions (PCI), which are related to the Auger decay of a vacancy in the Ar L-shell. During an Auger decay a postcollision interaction can occur causing the out-going photoelectron to be retarded thus losing a certain amount of energy. If the retardation is sufficiently large the photoelectron will not escape. This result produces a singly charged ion, which normally would not be present. Such evidence of electron capture by the PCI effect was first shown clearly by Eberhardt et al. and, with higher resolution, in the present work. However, capture of the photoelectron is expected to be 100% exactly at the L{sub 2,3} thresholds. Thus, from the authors results they would have expected the Ar{sup 2+} signal to be zero at threshold, but it was not? The authors can explain this anomoly on the basis that during the Auger decay the photoelectrons are captured into high lying excited states of Ar{sup +}, which subsequently decay through autoionization yielding Ar{sup 2+}. Future work in this area will seek experimental evidence to verify this prediction.

  8. Fluorescence excitation involving multiple electron transition states of N{sub 2} and CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Wu, C.Y.R.; Chen, F.Z.; Hung, T.; Judge, D.L. [Univ. of Southern California, Los Angeles, CA (United States)

    1997-04-01

    The electronic states and electronic structures of N{sub 2} and CO{sub 2} in the 8-50 eV energy region have been studied extensively both experimentally and theoretically. In the energy region higher than 25 eV there exists many electronic states including multiple electron transition (MET) states which are responsible for producing most of the dissociative photoionization products. The electronic states at energies higher than 50 eV have been mainly determined by Auger spectroscopy, double charge transfer, photofragment spectroscopy and ion-ion coincidence spectroscopy. The absorption and ionization spectra of these molecules at energies higher than 50 eV mainly show a monotonic decrease in cross section values and exhibit structureless features. The decay channels of MET and Rydberg (or superexcited) states include autoionization, ionization, dissociative ionization, predissociation, and dissociation while those of single ion and multiple ion states may involve predissociation. and dissociation processes. The study of fluorescence specifically probes electronically excited species resulting from the above-mentioned decay channels and provides information for understanding the competition among these channels.

  9. Measurements of photoionization cross sections from the 5s5p {sup 1}P{sub 1} and 5s6s {sup 1}S{sub 0} excited states of strontium

    Energy Technology Data Exchange (ETDEWEB)

    Sami-ul-Haq; Mahmood, S; Amin, N; Jamil, Y; Ali, R; Baig, M A [Atomic and Molecular Physics Laboratory, Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan)

    2006-04-14

    We present new measurements of the photoionization cross section from the 5s5p {sup 1}P{sub 1} state employing two-step excitation and from the 5s6s {sup 1}S{sub 0} state using two-photon excitation and then a second laser for subsequent ionization in each case. The two dye lasers, pumped by a common Nd:YAG laser, have been used in conjunction with a thermionic diode ion detector in one set of experiments and an atomic beam apparatus in the second experiment. The photoionization cross sections have been measured at six different wavelengths between 355 nm and 410 nm. The absolute value of the cross section at the peak of the (4d{sup 2}+5p{sup 2}) {sup 1}D{sub 2} autoionizing resonance is determined as 5450 (18%) Mb. The photoionization cross section from the 5s6s {sup 1}S{sub 0} state is estimated as 0.41 (16%) Mb.

  10. Theoretical study of the near uv photoabsorption by the Kr2* excimer

    International Nuclear Information System (INIS)

    The physical process responsible for near UV photoabsorption by the Kr*2 excimer are examined and the energy dependence of the photoabsorption cross sections is calculated. Near UV photoabsorption by the Kr*2 is a multiprocess phenomenon involving direct photoionization and concurrent photoexcitation to a repulsive resonance state, which subsequently autoionizes or dissociates. An adiabatic nuclei theory is developed, based on the use of Feshbach projection operators, to separate the ionization and dissociation channels, and to device photoionization and photodissociation cross sections. These cross sections are expressed in terms of parameters obtained from fixed nuclei electronic calculations and in terms wavefunctions describing nuclear motion. Stieltjes Tchebycheff Moment Theory (STMT) techniques are used to extract information concerning the ionization continuum from localized L2 electronic wavefunctions obtained from molecular electronic structure codes. Problems in the application of STMT techniques to narrow spectral features are examined. The cause of these problems is determined to be the use of the histogram midpoint approximation in low order STMT quadratures. Techniques are then developed which significantly improve the accuracy of STMT calculations for an isolated, narrow, resonance in a single continuum. Improved treatment of resonance profiles is demonstrated for pure Fano profiles, a shape resonance in a model barrier-and-well potential, and a shape resonance in the K-shell photoionization spectrum of N2. The improved STMT techniques are then used to obtain the fixed nuclei resonance profiles in the spectrum of Kr2

  11. Rydberg and valence state excitation dynamics: a velocity map imaging study involving the E-V state interaction in HBr.

    Science.gov (United States)

    Zaouris, Dimitris; Kartakoullis, Andreas; Glodic, Pavle; Samartzis, Peter C; Rafn Hróðmarsson, Helgi; Kvaran, Ágúst

    2015-04-28

    Photoexcitation dynamics of the E((1)Σ(+)) (v' = 0) Rydberg state and the V((1)Σ(+)) (v') ion-pair vibrational states of HBr are investigated by velocity map imaging (VMI). H(+) photoions, produced through a number of vibrational and rotational levels of the two states were imaged and kinetic energy release (KER) and angular distributions were extracted from the data. In agreement with previous work, we found the photodissociation channels forming H*(n = 2) + Br((2)P3/2)/Br*((2)P1/2) to be dominant. Autoionization pathways leading to H(+) + Br((2)P3/2)/Br*((2)P1/2) via either HBr(+)((2)Π3/2) or HBr(+)*((2)Π1/2) formation were also present. The analysis of KER and angular distributions and comparison with rotationally and mass resolved resonance enhanced multiphoton ionization (REMPI) spectra revealed the excitation transition mechanisms and characteristics of states involved as well as the involvement of the E-V state interactions and their v' and J' dependence. PMID:25801122

  12. Future directions in electron--ion collision physics

    International Nuclear Information System (INIS)

    This report discusses the following topics: Summary of session on synergistic co-ordination of theory and experiment; synergism between experiment and theory in atomic physics; comparison of theory and experiment for electron-ion excitation and ionization; summary of session on new theoretical and computational methods; new theoretical and computational methods-r-matrix calculations; the coulomb three-body problem: a progress report; summary of session on needs and applications for electron-ion collisional data; electron-ion collisions in the plasma edge; needs and applications of theoretical data for electron impact excitation; summary of session on relativistic effects, indirect effects, resonance, etc; direct and resonant processes in electron-ion collisions; relativistic calculations of electron impact ionization and dielectronic recombination cross section for highly charged ions; electron-ion recombination in the close-coupling approximation; modified resonance amplitudes with strongly correlated channels; a density-matrix approach to the broadening of spectral lines by autoionization, radiative transitions and electron-ion collisions; towards a time-dependent description of electron-atom/ion collisions two electron systems; and comments on inclusion of the generalized bright interaction in electron impact excitation of highly charged ions

  13. Electron-impact excitation and ionization of W3+ for the determination of tungsten influx in a fusion plasma

    Science.gov (United States)

    Ballance, C. P.; Loch, S. D.; Pindzola, M. S.; Griffin, D. C.

    2013-03-01

    Tungsten will be employed as a plasma facing material in the ITER fusion reactor under construction in Cadarache, France; therefore, there is a significant need for accurate electron-impact excitation and ionization data for the ions of tungsten. We report on the results of extensive calculations of ionization and excitation for W3+ that are intended to provide the atomic data needed for the determination of impurity influx diagnostics of tungsten in several existing tokamak reactors. The electron-impact excitation rate coefficients for this study were determined using the relativistic R-matrix method. The contribution to direct electron-impact ionization was determined using the distorted-wave approximation, the accuracy of which was verified by an R-matrix with pseudo states calculation. Contributions to total ionization from excitation autoionization were also generated from the relativistic R-matrix method. These results were then employed to calculate values of ionization per emitted photon, or SXB ratios, for four carefully selected spectral lines; these data will allow the determination of impurity influx from tungsten facing surfaces. For the range of densities of importance in the edge region of a tokamak reactor, these SXB ratios are found to be nearly independent of electron density but vary significantly with electron temperature.

  14. The benzene radical anion: A computationally demanding prototype for aromatic anions

    International Nuclear Information System (INIS)

    The benzene radical anion is studied with ab initio coupled-cluster theory in large basis sets. Unlike the usual assumption, we find that, at the level of theory investigated, the minimum energy geometry is non-planar with tetrahedral distortion at two opposite carbon atoms. The anion is well known for its instability to auto-ionization which poses computational challenges to determine its properties. Despite the importance of the benzene radical anion, the considerable attention it has received in the literature so far has failed to address the details of its structure and shape-resonance character at a high level of theory. Here, we examine the dynamic Jahn-Teller effect and its impact on the anion potential energy surface. We find that a minimum energy geometry of C2 symmetry is located below one D2h stationary point on a C2h pseudo-rotation surface. The applicability of standard wave function methods to an unbound anion is assessed with the stabilization method. The isotropic hyperfine splitting constants (Aiso) are computed and compared to data obtained from experimental electron spin resonance experiments. Satisfactory agreement with experiment is obtained with coupled-cluster theory and large basis sets such as cc-pCVQZ

  15. Study by photo-ionization of some simple poly-atomic molecules and calculation of the Franck-Condon factors

    International Nuclear Information System (INIS)

    The photo-ionization yield curves for C2H2, C2D2, C2H4 and C2H2D2 have been determined using a mass spectrometer coupled with an U.V. monochromator. Besides exhibiting a stair case structure near threshold due to the excitation of vibrational levels in the ion ground state, all the curves have broad maxima corresponding to auto-ionization phenomena. The ionization potentials of these molecules have been measured, together with the appearance potentials of the main ion-fragments. The excitation probabilities for the vibrational levels during ionization, or Franck-Condon factors, have been calculated for C2H2 and C2D2 using the method developed by Sharp and Rosenstock. Good agreement is generally obtained between the calculated values and those obtained experimentally from the photo-ionization yield curves. The preceding calculation method is then extended to the case where the electronic transition occurs with changes in the geometrical structure of the molecule (in particular, changes of symmetry). The Franck-Condon factors have been determined for NH3 (symmetry changes) and for H2O (changes in the equilibrium angle). Calculations show that there is generally considerable excitation of the combination bands. (author)

  16. Excitation and ionization of outer shells in Rb by electron impact

    Science.gov (United States)

    Roman, V.; Kupliauskienė, A.; Borovik, A.

    2015-10-01

    The relativistic distorted-wave and binary-encounter-dipole approximations were employed for calculating the electron-impact single ionization cross sections of the 5s, 4p6, 4s2, 3d10 shells and 4p6 excitation cross section for Rb atom taking into account both configuration interaction and relativistic effects. The capabilities of the most used theoretical approaches in describing the single ionization of Rb atom were considered by comparing the present and other available calculated data with the experimental total ionization and total direct single ionization cross sections over the electron-impact energy range from the 5s threshold to 600 eV. The best agreement within experimental uncertainty was obtained by using the non-relativistic binary-encounter-dipole approximation included in the LANL Atomic Physics Codes package. At present none of the used approximations (plane-wave Born or relativistic distorted wave) can satisfactorily describe the experimental excitation-autoionization cross section in rubidium because the efficient formation of the 4p6 core-excited negative-ion rubidium states at near-threshold impact energies is ignored in calculations.

  17. Dissociative photoionization of molecular hydrogen. A joint experimental and theoretical study of the electron-electron correlations induced by XUV photoionization and nuclear dynamics on IR-laser dressed transition states

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Andreas

    2015-01-13

    In this thesis, the dissociative single-ionization of molecular hydrogen is investigated in a kinematically complete experiment by employing extreme ultraviolet attosecond pulse trains and infrared femtosecond laser pulses. Induced by the absorption of a single XUV photon, a pronounced energy-dependent asymmetry of the relative emission direction of the photoelectron and the ion is observed. The asymmetry pattern is explained in terms of an interference of two ionization pathways involving a doubly-excited state. This interpretation is validated by a semi-classical model which only takes the nuclear motion into account. Using this model and the observed asymmetry, it is furthermore possible to disentangle the two dissociation pathways which allows for the determination of the autoionization lifetime of the contributing doubly-excited state as a function of the internuclear distance. Moreover, using a pump-probe experiment the dissociation dynamics of molecular hydrogen is investigated. A time-delay dependent momentum distribution of the fragments is observed. With a combined quantum mechanical and semi-classical approach the mechanism giving rise to the observed time-dependence is identified in terms of an intuitive elevator mechanism.

  18. Fano resonances in photoionization spectra of chromium in helium nanodroplets

    International Nuclear Information System (INIS)

    Full text: Ultracold He nanodroplets (HeN) at 0.4 K serve as ideal matrix to isolate and analyze single atoms with supporting effects from the interaction with the surrounding He. Resonance ionization mass spectroscopy (RIMS) is a versatile technique to selectively excite and detect atoms. We combined these methods and carried out resonant two-photon ionization (R2PI) measurements on Cr atoms in HeN in the wavelength range from 350 to 361 nm (27700 - 28600 cm-1). Possible pathways leading to ionization include a strong first step y7P0 7S transition happening inside the droplet. This results in a broadening and a blue shift of about 7 nm enabling the possibility to obtain detailed information about the perturbation upon electronic excitation of the Cr atom in HeN. Subsequently, the Cr atom leaves the droplet and simultaneously relaxes into lower lying states, which are spin and parity forbidden transitions. With a second photon of the same colour the ionization is accomplished through either continuum or autoionization states. We characterized Fano type resonances in terms of laser fluence saturation to get further insight into the various processes. (author)

  19. Total dielectronic recombination rate coefficient for Co-like tungsten

    International Nuclear Information System (INIS)

    Ab initio calculation of the total dielectronic recombination (DR) rate coefficient from the ground state 3s23p63d9(J=5/2) of Co-like tungsten is performed employing the relativistic distorted-wave approximation with configuration-interaction. The DR contributions mainly come from complex series 3d84ln'l'. The complex series 3p53d10n'l', 3p53d94ln'l' and 3d85ln'l' also contribute significantly to the total DR rates at relatively high electron temperatures. The l' and n' dependences of the partial rate coefficient are investigated. The inclusion of decays into autoionizing levels followed by radiative cascades (DAC) enlarges the total DR rate coefficients by a factor of about 10%. The level-by-level extrapolation method is developed to include DAC effects. The total DR rate coefficients are fitted to an empirical formula. It is shown that at temperatures above 2.5 keV the Burgess-Merts (BM) semiempirical formula can provide DR results with an accuracy of about 15%, whereas at electron temperatures below 100 eV it underestimates the DR rate coefficients by up to a few orders of magnitude and its temperature dependence is completely inadequate. The comparison of the results for Ni-like and Co-like tungsten shows that these two sets of DR rate coefficients are very close in magnitude at relatively high electron temperatures

  20. Negative ions, production of slow high-q ions, collisions with inner-shell excited targets using synchrotron radiation

    International Nuclear Information System (INIS)

    Tunable xuv radiation is important in atomic and molecular physics for the basic reason that the scale size for electronic binding energies in atoms and molecules is the Rydberg energy unit hcR = 1/2 e2/a0 13.6 eV, corresponding to the hydrogen atom photoelectric threshold wavelength near 910 A. All atoms and molecules will show outer or inner-shell electronic photoabsorption near or somewhat below this wavelength. The combination of high intensity (compared with conventional continuum sources) with monochromaticity and wide-range tunability is needed for systematic absorption spectroscopy of atomic core-excited states. The pioneering work on precision spectroscopy of autoionizing series in atoms was done a number of years ago but there is still considerable interest in this kind of work which should be greatly facilitated with synchrotron radiation. The work is needed for a better understanding of electron-correlation effects in many-electron atoms and of the nature of many-body discrete states embeded in a single-particle continuum

  1. Electron capture in collisions of S4+ with helium

    International Nuclear Information System (INIS)

    Charge transfer due to collisions of ground-state S4+(3s21S) ions with helium is investigated for energies between 0.1 meV u-1 and 10 MeV u-1. Total and state-selective single electron capture (SEC) cross sections and rate coefficients are obtained utilizing the quantum mechanical molecular-orbital close-coupling (MOCC), atomic-orbital close-coupling (AOCC), classical trajectory Monte Carlo (CTMC) and continuum distorted wave methods. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial coupling matrix elements obtained with the spin-coupled valence-bond approach. Previous data are limited to a calculation of the total SEC rate coefficient using the Landau-Zener model that is, in comparison to the results presented here, three orders of magnitude smaller. The MOCC SEC cross sections at low energy reveal a multichannel interference effect. True double capture is also investigated with the AOCC and CTMC approaches while autoionizing double capture and transfer ionization (TI) is explored with CTMC. SEC is found to be the dominant process except for E>200 keV u-1 when TI becomes the primary capture channel. Astrophysical implications are briefly discussed. (author)

  2. Effect of adsorbates on the formation of doubly excited He atoms during impact of He{sup 2+} ions on a Ni(1 1 0) surface

    Energy Technology Data Exchange (ETDEWEB)

    Busch, M.; Wethekam, S. [Humboldt-Universitaet zu Berlin, Institut fuer Physik, Newtonstrasse 15, D-12489 Berlin (Germany); Winter, H. [Humboldt-Universitaet zu Berlin, Institut fuer Physik, Newtonstrasse 15, D-12489 Berlin (Germany)], E-mail: winter@physik.hu-berlin.de

    2009-08-15

    The formation of doubly excited states of He atoms during impact of He{sup 2+} ions with projectile energies of 60-1000 eV under near-grazing angles of incidence of 5 deg. - 20 deg. on clean and adsorbate-covered Ni(1 1 0) surfaces is studied by means of Auger electron spectroscopy. Pronounced dependencies of electron spectra from autoionization of atoms in doubly excited 2s{sup 2}, 2s2p and 2p{sup 2} configurations on the coverage of the target surface with adsorbates are observed. These are directly related to work function changes, which are studied for the controlled adsorption of oxygen. Changes of the electron spectra on the target temperature are found for adsorbate-covered surfaces only, which puts into question recent interpretations of similar electron spectra in terms of a high local electron spin polarization of Ni(1 1 0) by an alternative interpretation based on thermal desorption or dissolution into bulk of surface contaminations. The formation of doubly excited states is studied for the oxygen p(2 x l) and p(3 x l) superstructures on Ni(1 1 0) in order to provide well-defined experimental data for theoretical investigations.

  3. Effect of adsorbates on the formation of doubly excited He atoms during impact of He2+ ions on a Ni(1 1 0) surface

    International Nuclear Information System (INIS)

    The formation of doubly excited states of He atoms during impact of He2+ ions with projectile energies of 60-1000 eV under near-grazing angles of incidence of 5 deg. - 20 deg. on clean and adsorbate-covered Ni(1 1 0) surfaces is studied by means of Auger electron spectroscopy. Pronounced dependencies of electron spectra from autoionization of atoms in doubly excited 2s2, 2s2p and 2p2 configurations on the coverage of the target surface with adsorbates are observed. These are directly related to work function changes, which are studied for the controlled adsorption of oxygen. Changes of the electron spectra on the target temperature are found for adsorbate-covered surfaces only, which puts into question recent interpretations of similar electron spectra in terms of a high local electron spin polarization of Ni(1 1 0) by an alternative interpretation based on thermal desorption or dissolution into bulk of surface contaminations. The formation of doubly excited states is studied for the oxygen p(2 x l) and p(3 x l) superstructures on Ni(1 1 0) in order to provide well-defined experimental data for theoretical investigations.

  4. Spectroscopic applications of the ISOLDE laser ion source

    CERN Document Server

    Sebastian, V; Fedosseev, V; Georg, U; Huber, G; Jading, Y; Jonsson, O; Köster, U; Koizumi, M; Kratz, K L; Kugler, E; Lettry, Jacques; Mishin, V I; Ravn, H L; Tamburella, C; Wöhr, A

    1998-01-01

    At the ISOLDE facility radioactive ion beams are produced via proton induced reactions in a target which is connected to a laser ion source. For beryllium a two step excitation scheme with laser light at wavelengths of lambda =235 nm and lambda =297 nm has been developed. Efficient laser ionization of beryllium was achieved with a new optical set-up using frequency tripling with two non-linear BBO crystals to generate laser light in the ultraviolet for the first excitation step. The second step was optimized to reach the 2p/sup 2 1/S/sub 0/ autoionizing state for high ionization efficiency. The isotope shift of /sup 7,9,10,11,12,14/Ba could be measured by tuning the wavelength of the first step. The laser ion source has also been used for the preparation of neutron-rich silver ion beams. Tuning the laser frequency of the first step it was possible to ionize selectively low- and high spin isomers of silver isotopes via the hyperfine structure. In both cases it was demonstrated that laser spectroscopy of exotic...

  5. Valence-shell photoionization of Ag-like Xe$^{7+}$ ions : experiment and theory

    CERN Document Server

    Mueller, A; Esteves-Macaluso, D; Habibi, M; Aguilar, A; Kilcoyn, A L D; Phaneuf, R A; Ballance, C P; McLaughlin, B M

    2014-01-01

    We report on experimental and theoretical results for the photoionization of Ag-like xenon ions, Xe$^{7+}$, in the photon energy range 95 to 145~eV. The measurements were carried out at the Advanced Light Source at an energy resolution of $\\Delta$E = 65 meV with additional measurements made at $\\Delta$E = 28 meV and 39 meV. Small resonance features below the ground-state ionization threshold, at about 106 eV, are due to the presence of metastable Xe$^{7+} (4d^{10} 4f~^2{\\rm F}^{\\circ}_{5/2,7/2})$ ions in the ion beam. On the basis of the accompanying theoretical calculations using the Dirac Atomic R-matrix Codes (DARC), an admixture of only a few percent of metastable ions in the parent ion beam is inferred, with almost 100\\% of the parent ions in the $(4d^{10}5s ~^2{\\rm S_{1/2}})$ ground level. The cross-section is dominated by a very strong resonance associated with $4d \\rightarrow 5f$ excitation and subsequent autoionization. This prominent feature in the measured spectrum is the $4d^95s5f ~^2{\\rm P}^{\\cir...

  6. The use of a shaped mesh lens in electron optics.

    Science.gov (United States)

    Deharak, B. A.; Martin, N. L. S.

    2006-05-01

    In electron impact ionization studies, an electron optical system is often used to (a) transport electrons from the interaction region to the entrance of an energy analyzer, and (b) adjust the energy of the electrons to that required by the analyzer. To obtain good resolution using electrostatic energy analyzers, such as the hemispherical sector type, low pass energies (a few eV) are required. However, such analyzers are often used in the detection of electrons with energies of tens of eV (e.g. those ejected from the He 2l2l' autoionizing levels with Eej˜35eV) and, if conventional electron optics are used, the required retardation increases the angular spread of trajectories at the analyzer entrance. This has the unwelcome effect of either degrading the energy resolution, or, if angular stops are used, substantially reducing the intensity. We have designed an electron optical system that uses shaped mesh lenses to achieve the required retardation without the attendant increase in angular spread. We will present simulations using SIMION 3D 7.0 Ion and Electron Optics Software.

  7. Photoionization of the ground state of the Be-like C2+ ion leading to C3+ 2l and 3l states

    International Nuclear Information System (INIS)

    Total and partial photoionization cross sections of the Be-like C2+ ion leading to the C3+ 2l and 3l(l = 0, 1) states from the 1S ground state have been calculated. The lower members of all autoionizing Rydberg series converging to the C3+ 2p, 3s, 3p, and 3d thresholds are identified and their energies and widths are determined. Except for the resonances converging to the C3+ 2p threshold, all of the resonance series are perturbed by overlapping series converging to other thresholds. In addition, the 4s4p 1P resonance is found to lie just below the C3+ 3d threshold. The calculations show excellent agreement between length and velocity gauges. Comparison with experiment for the photoionization of a mixture of the 1S ground state and 3P metastable states of C2+ in the photon energy range 40.8-56.9 eV shows good agreement with the present theoretical results; for the comparison, a calculation of photoionization of the metastable state was also performed. The present calculations are also compared with other previous theoretical and experimental results

  8. Characteristics of photoionization in the XUV domain for the excited 1s22s2p1,3Po states of the Be-like C2+ ion

    International Nuclear Information System (INIS)

    Resonance structures and their characteristics in the photoionization of the first excited p-states of Be-like C2+ ion which interact with the even-parity continua have been studied up to the C3+ 3d threshold limit. Using the variational R-matrix method, calculations have been performed in the initial 20 and final 22 state close-coupling approximations in the photon wavelength range 15-35 nm. The detailed photoionization processes of included multichannels are displayed in the partial photoionization cross sections, which contain a number of autoionizing Rydberg series of resonances converging to the C3+ 2p, 3s, 3p and 3d thresholds. In particular, the lower members of the Rydberg series showing irregular patterns of resonances, which lie above the C3+ 2p threshold, are identified and resonance positions Er, effective quantum numbers n*, and widths Γ are presented. Excellent agreement between length and velocity gauge results is found, along with overall good agreement with previous work, except for the discrepancies with the threshold behaviour of the OP (opacity project) result

  9. Photoionization of Be-like N3+ and Ne6+ ions: features of Be isoelectronic sequences of Z ⩽ 10

    International Nuclear Information System (INIS)

    Using a noniterative eigenchannel R-matrix method, we have studied the photoionization for ground 1S and excited 3,1P initial states of the Be-like N3+ and Ne6+ ions, up to the energy range of the final photo-ionic 3d state. The autoionizing resonance structures arising from the ground and excited states are identified and characterized. Our calculated photoionization cross sections with excellent agreement between length and velocity gauges are compared with the available experimental and previous theoretical results, and good agreement is shown. For the isoelectronic sequences of Z ⩽ 10, the Z-dependent spectral structures and developments of the cross sections are discussed based on the present results of N3+ and Ne6+ ions and the previous results of other ions obtained by the same noniterative eigenchannel R-matrix method. The intermixing among the resonances converging to the final photo-ionic 2p and the various 3l states is increased as Z, resulting in a much more complex pattern of resonances for the photoionization.

  10. Controlling the $2p$ Hole Alignment in Neon via the $2s$-$3p$ Fano Resonance

    CERN Document Server

    Heinrich-Josties, Elisabeth; Santra, Robin

    2014-01-01

    We study the state-resolved production of neon ion after resonant photoionization of Ne via the $2s$-$3p$ Fano resonance. We find that by tuning the photon energy across the Fano resonance a surprisingly high control over the alignment of the final $2p$ hole along the polarization direction can be achieved. In this way hole alignments can be created that are otherwise very hard to achieve. The mechanism responsible for this hole alignment is the destructive interference of the direct and indirect (via the autoionizing $2s^{-1}3p$ state) ionization pathways of $2p$. By changing the photon energy the strength of the interference varies and $2p$-hole alignments with ratios up to 19:1 between $2p_0$ and $2p_{\\pm 1}$ holes can be created: an effect normally only encountered in tunnel ionization using strong-field IR pulses. Including spin-orbit interaction does not change the qualitative feature and leads only to a reduction in the alignment by $2/3$. Our study is based on a time-dependent configuration-interactio...

  11. Dissociative photoionization of molecular hydrogen. A joint experimental and theoretical study of the electron-electron correlations induced by XUV photoionization and nuclear dynamics on IR-laser dressed transition states

    International Nuclear Information System (INIS)

    In this thesis, the dissociative single-ionization of molecular hydrogen is investigated in a kinematically complete experiment by employing extreme ultraviolet attosecond pulse trains and infrared femtosecond laser pulses. Induced by the absorption of a single XUV photon, a pronounced energy-dependent asymmetry of the relative emission direction of the photoelectron and the ion is observed. The asymmetry pattern is explained in terms of an interference of two ionization pathways involving a doubly-excited state. This interpretation is validated by a semi-classical model which only takes the nuclear motion into account. Using this model and the observed asymmetry, it is furthermore possible to disentangle the two dissociation pathways which allows for the determination of the autoionization lifetime of the contributing doubly-excited state as a function of the internuclear distance. Moreover, using a pump-probe experiment the dissociation dynamics of molecular hydrogen is investigated. A time-delay dependent momentum distribution of the fragments is observed. With a combined quantum mechanical and semi-classical approach the mechanism giving rise to the observed time-dependence is identified in terms of an intuitive elevator mechanism.

  12. Two-photon finite-pulse model for resonant transitions in attosecond experiments

    CERN Document Server

    Galán, Álvaro Jiménez; Argenti, Luca

    2015-01-01

    We present an analytical model capable of describing two-photon ionization of atoms with attosecond pulses in the presence of intermediate and final isolated autoionizing states. The model is based on the finite-pulse formulation of second-order time-dependent perturbation theory. It approximates the intermediate and final states with Fano's theory for resonant continua, and it depends on a small set of atomic parameters that can either be obtained from separate \\emph{ab initio} calculations, or be extracted from few selected experiments. We use the model to compute the two-photon resonant photoelectron spectrum of helium below the N=2 threshold for the RABITT (Reconstruction of Attosecond Beating by Interference of Two-photon Transitions) pump-probe scheme, in which an XUV attosecond pulse train is used in association to a weak IR probe, obtaining results in quantitative agreement with those from accurate \\emph{ab initio} simulations. In particular, we show that: i) Use of finite pulses results in a homogene...

  13. Electronic structure of helium atom in a quantum dot

    CERN Document Server

    Saha, Jayanta K; Mukherjee, T K

    2015-01-01

    Bound and resonance states of helium atom have been investigated inside a quantum dot by using explicitly correlated Hylleraas type basis set within the framework of stabilization method. To be specific, precise energy eigenvalues of bound 1sns (1Se) [n = 1-6] states and the resonance parameters i.e. positions and widths of 1Se states due to 2sns [n = 2-5] and 2pnp [n = 2-5] configuration of confined helium below N = 2 ionization threshold of He+ have been estimated. The two-parameter (Depth and Width) finite oscillator potential is used to represent the confining potential representing the quantum dot. It has been explicitly demonstrated that electronic structure properties become a sensitive function of the dot size. It is observed from the calculations of ionization potential that the stability of an impurity ion within quantum dot may be manipulated by varying the confinement parameters. A possibility of controlling the autoionization lifetime of doubly excited states of two-electron ions by tuning the wi...

  14. Strong-field absorption and emission of radiation in two-electron systems calculated with time-dependent natural orbitals

    CERN Document Server

    Brics, M; Bauer, D

    2016-01-01

    Recently introduced time-dependent renormalized-natural-orbital theory (TDRNOT) is based on the equations of motion for the so-called natural orbitals, i.e., the eigenfunctions of the one-body reduced density matrix. Exact TDRNOT can be formulated for any time-dependent two-electron system in either spin configuration. In this paper, the method is tested against high-order harmonic generation (HHG) and Fano profiles in absorption spectra with the help of a numerically exactly solvable one-dimensional model He atom, starting from the spin-singlet ground state. Such benchmarks are challenging because Fano profiles originate from transitions involving autoionizing states, and HHG is a strong-field phenomenon well beyond linear response. TDRNOT with just one natural orbital per spin in the helium spin-singlet case is equivalent to time-dependent Hartree-Fock or time-dependent density functional theory (TDDFT) in exact exchange-only approximation. It is not unexpected that TDDFT fails in reproducing Fano profiles ...

  15. Multi-photon excitation and ionization cross sections in atomic oxygen

    Energy Technology Data Exchange (ETDEWEB)

    McGuire, E.J.

    1985-01-01

    Calculations are presented on a variety of multi-photon excitation and ionization cross sections in oxygen. The regimes of cross sections discussed are: (1) 2-photon excitation to the bound (2p)/sup 3/ /sup 4/S (nl) levels; (2) 2-photon excitation to the autoionizing (2p)/sup 3/ /sup 2/D (3p) and (2p)/sup 3/ /sup 2/P (3p) levels; (3) excitation of the (2p)/sup 4/ /sup 1/D and /sup 1/S levels by both 1-photon excitation on forbidden transitions and 2-photon excitations; (4) 1-photon photoionization of the (2p)/sup 3/ /sup 4/S (3s) /sup 3/S and (2p)/sup 3/ /sup 4/S (3p) /sup 3/P levels; and (5) 3-photon nonresonant ionization with the (2p)/sup 3/ /sup 4/S (3p) /sup 3/P level as an intermediate resonance. 5 refs., 3 figs., 2 tabs.

  16. Spectroscopy of {sup 39}K{sup 85}Rb triplet excited states using ultracold a {sup 3}{sigma}{sup +} state molecules formed by photoassociation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J T; Wang, D; Eyler, E E; Gould, P L; Stwalley, W C [Physics Department, University of Connecticut, Storrs, CT 06269 (United States)], E-mail: w.stwalley@uconn.edu, E-mail: kimjt@chosun.ac.kr

    2009-05-15

    Convenient state-selective detection methods are proposed for exploring triplet Rydberg states from the metastable a {sup 3}{sigma}{sup +} state of ultracold KRb molecules by resonance-enhanced two-photon ionization and time-of-flight (TOF) mass spectroscopy. This would allow the first accurate determination of the ionization potential. Particularly suitable resonant intermediate states include the 2 {sup 3}{pi} {sub {omega}}, 3 {sup 3}{sigma}{sup +} and 4 {sup 3}{sigma}{sup +} states, and we report spectroscopic studies of these states. For the 2 {sup 3}{pi} {sub {omega}} state, the spin-orbit components ({omega} = 0{sup +}, 0{sup -}, 1 and 2) have been investigated and a shallow long-range state (5(0{sup +})) at {approx} 9.3 A has been observed. We compare our observations of these three states with predictions based on ab initio potential energy curves. Such studies may also permit the direct observation of autoionizing resonances leading to efficient formation of low-lying rovibrational levels of the {sup 2}{sigma}{sup +} ground state of KRb{sup +}, ideally in the v{sup +}= 0, N{sup +}= 0 level.

  17. Excited State Formation in Electron Capture by Slow Multiply Charged Ions

    International Nuclear Information System (INIS)

    Translational energy spectroscopy (TES) has been used to study one-electron capture by H and He-like ions of C, N and O in both H and H2 at energies below 1 keV amu-1. Similar measurements have been carried out for He2+ ions in the hydrocarbons CH4, C2H4, C2H6 and H2O at energies within the range 250-2000 eV amu-1. One-electron capture by O6+ ions in H2O, CO2 and CH4 and by C4+ ions in CH4 have also been studied in the range 200-1500 eV amu-1. The main excited product states have been identified, their relative importance assessed and, in some cases, cross-sections determined. In the molecular targets, contributions to one-electron capture from non-dissociative and dissociative mechanisms as well as from two-electron capture into autoionizing states has also been determined. In all cases, the highly selective nature of the electron capture process is confirmed even in the case of molecules with many possible fragmentation channels involving a wide range of energy defects. In the case of H, the main product channels are well predicted by reaction windows calculated using a Landau-Zener approach. However, the same approach applied to molecules, where both non-dissociative and dissociative mechanisms are significant, is found to be of limited use. (author)

  18. Shock-ionization in the Extended Emission-Line Region of 3C~305. The last piece of the (optical) puzzle

    CERN Document Server

    Reynaldi, Victoria

    2013-01-01

    We present new Gemini spectroscopical data of the Extended Emission-Line Region of 3C~305 radio galaxy in order to achieve the final answer of the long-standing question about the ionizing mechanism. The spectra show strong kinematic disturbances within the most intense line-emitting region. The relative intensities amongst the emission lines agree with the gas being shocked during the interaction of the powerful radio jets with the ambient medium. The emission from the recombination region acts as a very effective cooling mechanism, which is supported by the presence of a neutral outflow. However, the observed intensity is almost an order of magnitude lower than expected in a pure shock model. So auto-ionizing shock models, in low-density and low-abundance regime, are required in order to account for the observed emission within the region. This scenario also supports the hypothesis that the optical emitting gas and the X-ray plasma are in pressure balance.

  19. Photophysics of fullerenes: Thermionic emission

    International Nuclear Information System (INIS)

    Multiphoton ionization of fullerenes using long-pulse length lasers occurs mainly through vibrational autoionization. In many cases the laser ionization can be described as thermionic in analogy to the boiling off of electrons from a filament. Thermionic emission manifests itself as a delayed emission of electrons following pulsed laser excitation. Klots has employed quasiequilibrium theory to calculate rate constants for thermionic emission from fullerenes which seem to quantitatively account for the observed delayed emission times and the measured electron energy distributions. The theory of Klots also accounts for the thermionic emission of C60 excited by a low power CW Argon Ion laser. Recently Klots and Compton have reviewed the evidence for thermionic emission from small aggregates where mention was also made of experiments designed to determine the effects of externally applied electric fields on thermionic emission rates. The authors have measured the fullerene ion intensity as a function of the applied electric field and normalized this signal to that produced by single photon ionization of an atom in order to correct for all collection efficiency artifacts. The increase in fullerene ion signal relative to that of Cs+ is attributed to field enhanced thermionic emission. From the slope of the Schottky plot they obtain a temperature of approximately 1,000 K. This temperature is comparable to but smaller than that estimated from measurements of the electron kinetic energies. This result for field enhanced thermionic emission is discussed further by Klots and Compton. Thermionic emission from neutral clusters has long been known for autodetachment from highly excited negative ions. Similarly, electron attachment to C60 in the energy range from 8 to 12 eV results in C60 anions with lifetimes in the range of microseconds. Quasiequilibrium theory (QET) calculations are in reasonable accord with these measurements

  20. Theoretical Studies of Electron Driven Resonant Processes in H+2 and HeH+: Dissociative Recombination, Vibrational Excitation and Dissociative Excitation

    International Nuclear Information System (INIS)

    Full text: We have carried out a number of preliminary studies of the dynamics of H2+ and HeH+ and their isotopes following low-energy electron collisions. We are continuing these studies, increasing the accuracy of the calculations and studying reactions leading to dissociative recombination, vibrational excitation and dissociative excitation and possibly ion-pair formation. These calculations will be carried out for a wider range of electron energies than previously explored, and in addition will look at the effect of vibrational excitation of the initial target. Previous work had assumed the target molecule was in its ground vibrational state. For the fusion plasma environment, both the energy of the electron collision and the degree of vibrational excitation is higher than what has been studied before. In addition, final branching ratios will be calculated. We use the complex Kohn variational method to study the electron collisions and a combination of time-dependent and time-independent solutions to the Schroedinger equation to study the dynamics following the collision. Another important reaction for modeling of the fusion plasmas is mutual neutralization in collisions between H- and H+ or He+. We have previously studied the first of these reactions and we intend to study the second reaction. These reactions are driven by non-adiabatic couplings between the ion-pair state and the covalent states especially at large internuclear distances and the cross section for the reaction will be computed by solving a coupled Schroedinger equation for the nuclear motion where the effect of autoionization will be included. (author)

  1. Auger energies, branching ratios, widths and x-ray rates of double K-vacancy states of Ne2+: a close-coupling calculation

    International Nuclear Information System (INIS)

    A close-coupling calculation is performed for the photoionization cross section of the high-lying core-excited state 1s2s22p5 1Po of Ne2+ in the energy region of the double K-vacancy resonance 1s02s22p6 1S. The calculation is carried out by using the R-matrix method in the LS-coupling scheme, which includes 27 target states and extensive configuration interaction. The KK-KL x-ray energy, rate and autoionization width of the double K-vacancy state, together with KK-KLL Auger energies and branching ratios of the main channels, are obtained from the cross sections and the contributions of these channels. The calculated resonance energy and x-ray rate are in good agreement with the existing experimental and theoretical results. For the Auger width, our result agrees well with the available experimental result and it is very close to the average of other theoretical data, which shows considerable differences with each other. The Auger energy of the predominate channel KK-KL23L23 2D is in rather good agreement with recent experiments on the Auger spectra. Our branching ratios for the channels KK-KL23L23 2D and KK-KL23L23 2S are larger than the results obtained by the multi-configuration Dirac–Fock method by ∼20% on average, which may be due to the coupling of the continuum channels. (paper)

  2. Three-photon resonance ionization of atomic Mn in a hot-cavity laser ion source using Ti:sapphire lasers

    Science.gov (United States)

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

    2015-06-01

    Three-photon resonance ionization of atomic manganese (Mn) in a hot-cavity ion source using Ti:sapphire lasers has been demonstrated. Three-step ionization schemes employing different intermediate levels and Rydberg or autoionizing (AI) states in the final ionization step are established. Strong AI resonances were observed via the 3d54s5s f 6S5/2 level at 49 415.35 cm-1, while Rydberg transitions were reached from the 3d54s4d e 6D9/2,7/2,5/2 levels at around 47 210 cm-1. Analyses of the strong Rydberg transitions associated with the 3d54s4d e 6D7/2 lower level indicate that they belong to the dipole-allowed 4d → nf 6F°9/2,7/2,5/2 series converging to the 3d54s 7S3 ground state of Mn II. From this series, an ionization potential of 59 959.56 ± 0.01 cm-1 is obtained for Mn. At high ion source temperatures the semi-forbidden 4d → nf 8F°9/2,7/2,5/2 series was also observed. The overall ionization efficiency for Mn has been measured to be about 0.9% when using the strong AI transition in the third excitation step and 0.3% when employing an intense Rydberg transition. Experimental data indicate that the ionization efficiency was limited by the interaction of Mn atoms with ion source materials at high temperatures.

  3. Investigations of the biological effects of radiation: a multi-discipline approach. Progress report, September 1, 1976--August 31, 1977

    Energy Technology Data Exchange (ETDEWEB)

    Friedell, H.L.

    1977-09-01

    The quasi-free electron attachment rate, k/sub e/, and mobility, ..mu../sub e/, were studied in non-polar solutions using pulsed conductivity techniques. Measurements of k/sub e/ of >50 nitro compounds in liquids have ..mu../sub e/ ranging from <0.1 to 100 cm/sup 2//volt sec at temperatures from -100 to +40/sup 0/C indicated electron-dipole interactions are important in liquids having ..mu../sub e/ < 1 cm/sup 2//volt sec. The Smoluchowski equation was modified to include electron-dipole interactions and calculated k/sub e/'s agreed with observations within +-20%. The cellular enhancement ratio, CER, of nine of the nitro compounds were measured and a correlation between k/sub e/ and CER was found which was used to refine a model of cellular radiosensitization involving quasi-free electrons. Diffusion-controlled k/sub e/'s were observed for several carcinogens and in reversed micellar solutions. Field-dependent k/sub e/'s were measured in liquids having ..mu../sub e/ ranging from 10/sup -4/ to 500 cm/sup 2//volt sec and were found to increase at ..mu../sub e/ < 1 and decrease at ..mu../sub e/ > 70 cm/sup 2//volt sec with increasing field. The ..mu../sub e/ of liquid C/sub 2/H/sub 6/ was measured from -40/sup 0/C through the critical temperature at fields up to 180 kV/cm and a transition from polaron to delocalized electron conduction was observed. A pico-second (ps) pulse conductivity technique was developed and hot electron and/or autoionization processes were observed in tetramethylsilane, TMS, 200 ps after the ionizing pulse. A dose, field, and polarity dependent conductivity spike having a lifetime of 100 ps was observed in TMS and is interpreted as a prebreakdown phenomenon.

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

    Science.gov (United States)

    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

  5. Characterizing the gas phase ion chemistry of an ion trap mobility spectrometry based explosive trace detector using a tandem mass spectrometer.

    Science.gov (United States)

    Kozole, Joseph; Tomlinson-Phillips, Jill; Stairs, Jason R; Harper, Jason D; Lukow, Stefan R; Lareau, Richard T; Boudries, Hacene; Lai, Hanh; Brauer, Carolyn S

    2012-09-15

    A commercial-off-the-shelf (COTS) ion trap mobility spectrometry (ITMS) based explosive trace detector (ETD) has been interfaced to a triple quadrupole mass spectrometer (MS/MS) for the purpose of characterizing the gas phase ion chemistry intrinsic to the ITMS instrument. The overall objective of the research is to develop a fundamental understanding of the gas phase ionization processes in the ITMS based ETD to facilitate the advancement of its operational effectiveness as well as guide the development of next generation ETDs. Product ion masses, daughter ion masses, and reduced mobility values measured by the ITMS/MS/MS configuration for a suite of nitro, nitrate, and peroxide containing explosives are reported. Molecular formulas, molecular structures, and ionization pathways for the various product ions are inferred using the mass and mobility data in conjunction with density functional theory. The predominant product ions are identified as follows: [TNT-H](-) for trinitrotoluene (TNT), [RDX+Cl](-) for cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), [NO(3)](-) for ethylene glycol dinitrate (EGDN), [NG+NO(3)](-) for nitroglycerine (NG), [PETN+NO(3)](-) for pentaerythritol tetranitrate (PETN), [HNO(3)+NO(3)](-) for ammonium nitrate (NH(4)NO(3)), [HMTD-NC(3)H(6)O(3)+H+Cl](-) for hexamethylene triperoxide diamine (HMTD), and [(CH(3))(2)CNH(2)](+) for triacetone triperoxide (TATP). The predominant ionization pathways for the formation of the various product ions are determined to include proton abstraction, ion-molecule attachment, autoionization, first-order and multi-order thermolysis, and nucleophilic substitution. The ion trapping scheme in the reaction region of the ITMS instrument is shown to increase predominant ion intensities relative to the secondary ion intensities when compared to non-ion trap operation. PMID:22967626

  6. Absorption spectroscopy of laser excited europium vapour

    International Nuclear Information System (INIS)

    Absorption spectra of europium vapour irradiated by intense, monochromatic resonance radiation at the wavelengths of the three principal resonance lines, 4f76s2, 8S(J=7/2)→4f76s6p, y 8P(J=5/2, 7/2 and 9/2) at 466.2, 462.7 and 459.4 nm respectively, have been photographed at high resolution. Pulsed resonance radiation was obtained from a tunable, narrow-band dye laser pumped by a nitrogen laser: a broad-band dye laser pumped by the same nitrogen laser provided background radiation. Our spectra covered the ranges 380-400 nm, and 410-450 nm, each one showing transitions from a single resonance level to upper levels in the region of either the 4f76s, 7S or the 4f76s, 9S ionization limit of EuII. In the shorter wavelength range the spectra consisted of weak autoionized series converging towards the 7S limit. In the longer wavelength range the three spectra were surprisingly dissimilar. The majority of the upper levels could be arranged into five highly-perturbed series, one corresponding to each of the J values 3/2, 5/2, 7/2, 9/2 and 11/2. These series arose from excitation of the 6p electron to high lying d-orbitals. The absorption transitions to the series members are only prominent in regions where the series are strongly perturbed, indicating that most of the line strength is derived from the perturbing levels. Possible origins for the perturbing levels are discussed. Little evidence was found for a series arising from excitation of the 6p electron to high lying s-orbitals. (author)

  7. Resonant photoelectron spectroscopy at the Mo 4p→4d absorption edge in MoS2

    International Nuclear Information System (INIS)

    A systematic study has been conducted of the resonant behavior of the valence-band photoelectron spectrum of MoS2 for hν=26--70 eV, spanning the Mo 4p→4d transition region. A broad Fano-like resonance appears at ∼42 eV in the constant-initial-state (CIS) intensity plot of the dz2 peak near the valence-band maximum [∼2 eV binding energy (BE)], confirming its predominantly Mo 4d character. A second shoulder on the higher-hν side of the maximum in the dz2 CIS intensity plot is suggested to result from transitions to unoccupied states in the 5sp band ∼10 eV above EF, by comparison with a partial-yield spectrum and previous inverse-photoemission data. The region of the valence band in the range 3--4.5-eV BE also exhibits resonant behavior, indicating Mo 4d character, although somewhat less than for the dz2 peak. The 5--7-eV BE range does not exhibit resonance behavior at the Mo 4p edge and, therefore, contains negligible Mo 4d character. A feature at ∼30 eV in the CIS intensity plot for the 5--7-eV BE range could not be definitively assigned in this study, but may be due to a resonance between direct photoemission and a process involving absorption and autoionization of electronic states that contain Mo 5s and 5p character

  8. Electron attachment to pentafluorobenzene, to oxygen in a mixture of 90% argon and 10% methane, and to oxygen in various polar/nitrogen mixtures

    International Nuclear Information System (INIS)

    By means of electron swarm experiments, electron attachment to pentafluorobenzene (C6HF5) in nitrogen (N2) and to oxygen (O2) in various gas mixtures has been studied. The variation of the electron attachment rate for C6HF5 in N2 with the gas pressure and with the mean electron energy was determined. The lifetime of the species C6HF5- against autoionization was deduced and the electron attachment cross section for C6HF5 was calculated. The influence of the permanent electric dipole of C6HF5 upon the electron attachment process is discussed. Electron attachment to O2 in P-10 (90% argon + 10% methane) and in mixtures of various polar molecules with N2 was investigated. As a preliminary to these studies electron drift velocities in P-10 and in the various mixtures of polar species with N2 were determined. These drift velocities are reported and discussed. The variation of the electron attachment rate for O2 in P-10 with pressure and the mean electron energy was determined. The attachment rate as a function of mean electron energy was found to possess distinct structure. Models which account for this structure and for the variation of the attachment rate with the P-10 pressure are advanced and the corresponding reaction rate constant are presented. The electron attachment rates for O2 in mixtures of N2 with 1-butene, dimethyl amine, ammonia, trifluoromethane, and acetaldehyde were measured. Models of the variation of the attachment rate with the concentration of the polar species are advanced and the corresponding reaction rate constants are presented

  9. Development of a method for the study of H{sub 2} gas emission in sealed compartments containing canister copper immersed in O{sub 2}-free water

    Energy Technology Data Exchange (ETDEWEB)

    Bengtsson, Andreas; Chukharkina, Alexandra; Eriksson, Lena; Hallbeck, Bjoern; Hallbeck, Lotta; Johansson, Jessica; Johansson, Linda; Pedersen, Karsten [Microbial Analytics Sweden AB, Moelnlycke (Sweden)

    2013-06-15

    Current models of copper corrosion indicate that copper is not subject to corrosion by water in itself, but that additional components, such as O{sub 2}, chloride or sulphide are needed to initiate a corrosive process. Of late however, a number of reports have suggested that copper may be susceptible to water-induced corrosion in the absence of external constituents affecting the process. The process has been proposed to rely the auto-ionization driven presence of the hydroxide ions in pure water, and to result in the development of atomic hydrogen (H), with subsequent release of H{sub 2} gas. A suggested equilibrium is reached at a partial pressure of H{sub 2} of about 1 mbar (0.1 kPa) in 73 deg C, and the corrosion reaction is proposed to be rate-limited by the supply of hydroxide ions from the water, a process being slower than proposed formation of water from a H{sub 2}-O{sub 2} reaction. In consequence, the presence of O{sub 2} in the system would result in no detectable release of H{sub 2} until all O{sub 2} was consumed, while the absence of O{sub 2} would lead to water-driven corrosion of copper proceeding until the H{sub 2} equilibrium is reached, at a partial H{sub 2} pressure of about 1 mbar. The proposed mechanism presents a novel aspect on copper corrosion processes. By extension, the suggested corrosion process may have implications for proposed strategies for long-term storage of spent nuclear fuel waste (SNF), which in part rely on the long-term (>105 years) integrity of copper canisters stored in anoxic water inundated environments (SKB 2010)

  10. Investigations of the biological effects of radiation: a multi-discipline approach. Progress report, September 1, 1976--August 31, 1977

    International Nuclear Information System (INIS)

    The quasi-free electron attachment rate, k/sub e/, and mobility, μ/sub e/, were studied in non-polar solutions using pulsed conductivity techniques. Measurements of k/sub e/ of >50 nitro compounds in liquids have μ/sub e/ ranging from 2/volt sec at temperatures from -100 to +400C indicated electron-dipole interactions are important in liquids having μ/sub e/ 2/volt sec. The Smoluchowski equation was modified to include electron-dipole interactions and calculated k/sub e/'s agreed with observations within +-20%. The cellular enhancement ratio, CER, of nine of the nitro compounds were measured and a correlation between k/sub e/ and CER was found which was used to refine a model of cellular radiosensitization involving quasi-free electrons. Diffusion-controlled k/sub e/'s were observed for several carcinogens and in reversed micellar solutions. Field-dependent k/sub e/'s were measured in liquids having μ/sub e/ ranging from 10-4 to 500 cm2/volt sec and were found to increase at μ/sub e/ 70 cm2/volt sec with increasing field. The μ/sub e/ of liquid C2H6 was measured from -400C through the critical temperature at fields up to 180 kV/cm and a transition from polaron to delocalized electron conduction was observed. A pico-second (ps) pulse conductivity technique was developed and hot electron and/or autoionization processes were observed in tetramethylsilane, TMS, 200 ps after the ionizing pulse. A dose, field, and polarity dependent conductivity spike having a lifetime of 100 ps was observed in TMS and is interpreted as a prebreakdown phenomenon

  11. Studies in the electronic structure of matter

    Energy Technology Data Exchange (ETDEWEB)

    Miller, D. L.

    1979-01-01

    KLL Auger transition rates for helium are computed using simple atomic orbital wavefunctions which take into account the difference in average electron--electron repulsion of initial and final states. The results are consistent with transition rates computed by other authors using a variety of many-electron techniques. It is suggested that wavefunctions determined in the manner described provide a useful representation of the autoionizing state within the first Bohr radius. A method for extracting atomic pseudopotentials from photoelectron angular distributions is described and applied photoionization of the outermost p shells of Ar, Kr, and Xe and to the 4d shell of Xe. The pseudopotentials obtained reproduce the data, and also predict accurate cross sections and phase shifts for photoelectron energies up to 100 eV. It is suggested that the pseudopotentials aptly mimic the effects of intrashell electron--electron correlations in the photoionization process. The extended Hueckel theory is applied to the nitrogen trap in GaAs and GaP. Perfect crystal band structures are computed and are shown to be in reasonable agreement with those computed with empirical pseudopotentials. Nitrogen impurity levels in GaAs and GaP are computed using an extended Hueckel cluster model. In each case the model predicts two states within the band gap, in contrast to experiment which detects one impurity state in GaP and none in GaAs. It is suggested that the choice of cluster used unrealistically concentrates states near the conduction band edge on the central atom.

  12. Studies in the electronic structure of matter

    International Nuclear Information System (INIS)

    KLL Auger transition rates for helium are computed using simple atomic orbital wavefunctions which take into account the difference in average electron--electron repulsion of initial and final states. The results are consistent with transition rates computed by other authors using a variety of many-electron techniques. It is suggested that wavefunctions determined in the manner described provide a useful representation of the autoionizing state within the first Bohr radius. A method for extracting atomic pseudopotentials from photoelectron angular distributions is described and applied photoionization of the outermost p shells of Ar, Kr, and Xe and to the 4d shell of Xe. The pseudopotentials obtained reproduce the data, and also predict accurate cross sections and phase shifts for photoelectron energies up to 100 eV. It is suggested that the pseudopotentials aptly mimic the effects of intrashell electron--electron correlations in the photoionization process. The extended Hueckel theory is applied to the nitrogen trap in GaAs and GaP. Perfect crystal band structures are computed and are shown to be in reasonable agreement with those computed with empirical pseudopotentials. Nitrogen impurity levels in GaAs and GaP are computed using an extended Hueckel cluster model. In each case the model predicts two states within the band gap, in contrast to experiment which detects one impurity state in GaP and none in GaAs. It is suggested that the choice of cluster used unrealistically concentrates states near the conduction band edge on the central atom

  13. Theoretical photoionization spectra in the UV photon energy range for a Mg-like Al+ ion

    International Nuclear Information System (INIS)

    In the present work, we report the photoionization cross sections of the Al+ ion calculated for the photon energy range 20-26 eV and 30-50 eV. We have expanded our previous calculation (2007 J. Phys. Soc. Japan 76 014302) with an optimized admixture of the initial ground state 3s21S and exited states 3s3p1,3P, 3s3d1,3D and 3s4s1,3S, and obtained significantly improved predictions for the main background and autoionizing resonance structures of the reported experimental spectra. The absolute measurements of the photoionization cross sections of the Al+ ion in these energy ranges have been performed by West et al (2001 Phys. Rev. A 63 052719), and they reported that the prominent peaks around 21 eV were attributed to the effects of the significant influence of the small fraction of the fourth-order radiation with energies around 84 eV from the synchrotron source. In our previous work, the main shape for these cross sections was calculated assuming an admixture of initial 3s21S and 3s3p3P states, only with a rough overall estimate for the experimental spectra in the photon energy range 20-26 eV, and without these peaks around 21 eV. The report of the experimental assignment attributes these peaks to the excitation of a 2p electron from the core. However, our present results with the new admixture reveal similar peaks without considering the possibility of the core excitation

  14. Excitation and ionization of highly charged ions by electron impact: Progress report for period May 1, 1986-April 30, 1987

    International Nuclear Information System (INIS)

    (1) Cross sections and rate coefficients with inclusion of mixing effects have been obtained for innershell ionization of Na-like ions. This is an important mechanism for populating the excited levels of Neon-like ions and the importance increases with Z. (2) Cross sections and rate coefficients with inclusion of mixing effects have been obtained for innershell ionization of Li-like ions. This appears to be an important mechanism for populating the excited levels of He-like ions and its importance also increases with Z. (3) The collision strengths have been calculated for all 1171 innershell excitation transitions from the five lower levels of the form 1s22s22p63l2L/sub J/ to the doubly excited upper levels of kinds 1s22s22p5(3l'3l''/sup 2S''+1/L''/sub J'/ and 1s22s2p6(3l'3l''/sup 2S''+1/L'')/sup 2S'+1/L'/sub J'/ in 22 Na-like ions. These upper levels can radiatively decay, which produces satellite lines to those due to n = 3 to n = 2 transitions in neon-like ions, or they can autoionize, which populates the 1s22s22p61S0 ground level of neon-like ions. Considerable progress has also been made on our new quasirelativistic code development. After checking the accuracy for hydrogenic ions with Z values up to 90, we have now obtained preliminary quasirelativistic results for both structure and collision strengths for neon-like ions. These generally agree well with fully relativistic calculations. 41 refs

  15. Exotic helium molecules

    International Nuclear Information System (INIS)

    We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range 4He2(23S1-23P0) molecule, or a 4He2(23S1-23S1) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 ± 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range 4He2(23S1-23S1) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime τ = (1.4 ± 0.3) μs is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)

  16. The soft-photon approximation in infrared-laser-assisted atomic ionization by extreme-ultraviolet attosecond-pulse trains

    International Nuclear Information System (INIS)

    We use the soft-photon approximation, formulated for finite pulses, to investigate the effects of the dressing pulse duration and intensity on simulated attosecond pump–probe experiments employing trains of attosecond extreme-ultraviolet pulses in conjunction with an IR probe pulse. We illustrate the validity of the approximation by comparing the modelled photoelectron distributions for the helium atom, in the photon energy region close to the N = 2 threshold, to the results from the direct solution of the time-dependent Schrödinger equation for two active electrons. Even in the presence of autoionizing states, the model accurately reproduces most of the background features of the ab initio photoelectron spectrum in the 1s channel. A splitting of the photoelectron harmonic signal along the polarization axis, in particular, is attributed to the finite duration of the probe pulse. Furthermore, we study the dependence of the sideband integrated signal on the pump–probe time delay for increasing IR field strengths. Starting at IR intensities of the order of  ∼ 1 TW cm−2, overtones in the sideband oscillations due to the exchange of three or more IR photons start to appear. We derive an analytical expression in the frequency-comb limit of the soft-photon model for the amplitude of all the sideband frequency components and show that these amplitudes oscillate as a function of the intensity of the IR field. In particular, we predict that the amplitude of the fundamental component with frequency 2ωIR, on which the rabitt optical reconstruction technique is based, changes sign periodically. (paper)

  17. Development of a method for the study of H2 gas emission in sealed compartments containing canister copper immersed in O2-free water

    International Nuclear Information System (INIS)

    Current models of copper corrosion indicate that copper is not subject to corrosion by water in itself, but that additional components, such as O2, chloride or sulphide are needed to initiate a corrosive process. Of late however, a number of reports have suggested that copper may be susceptible to water-induced corrosion in the absence of external constituents affecting the process. The process has been proposed to rely the auto-ionization driven presence of the hydroxide ions in pure water, and to result in the development of atomic hydrogen (H), with subsequent release of H2 gas. A suggested equilibrium is reached at a partial pressure of H2 of about 1 mbar (0.1 kPa) in 73 deg C, and the corrosion reaction is proposed to be rate-limited by the supply of hydroxide ions from the water, a process being slower than proposed formation of water from a H2-O2 reaction. In consequence, the presence of O2 in the system would result in no detectable release of H2 until all O2 was consumed, while the absence of O2 would lead to water-driven corrosion of copper proceeding until the H2 equilibrium is reached, at a partial H2 pressure of about 1 mbar. The proposed mechanism presents a novel aspect on copper corrosion processes. By extension, the suggested corrosion process may have implications for proposed strategies for long-term storage of spent nuclear fuel waste (SNF), which in part rely on the long-term (>105 years) integrity of copper canisters stored in anoxic water inundated environments (SKB 2010)

  18. High-Resolution Spectroscopy of Long-Range Molecular States of 85Rb_2

    Science.gov (United States)

    Carollo, Ryan; Eyler, Edward E.; Bruneau, Yoann; Gould, Phillip; Stwalley, W. C.

    2015-06-01

    We present analysis of low-n long-range molecular Rydberg states in 85Rb_2, based on high-resolution spectra. The weakly bound states are accessed by bound-bound transitions from high-v levels of the a ^3 σ _u^+ state, which are prepared by photoassociation of laser-cooled atoms. Single-photon transitions to target states near the 5s + 7p asymptote are excited by a frequency-doubled pulse-amplified CW laser with a narrow linewidth, under 200 MHz. The long-range portion of the bonding potential is dominated by the elastic scattering interaction of the Rydberg electron of a perturbed 7p atom and a nearby ground-state atom, in much the same manner as trilobite states. We use time of flight to selectively measure molecular ions, which are formed via autoionization. This technique gives a two orders-of-magnitude improvement in linewidth over our previous work, reported in Ref. [1]. We also present calculations of a proposed scheme for STIRAP transfer from the current v''=35 level of the a ^3 σ _u^+ state to the v''=39 level. The long-range states accessible to us are defined in large part by the Franck-Condon factors, which are dominated by the outer lobe of the wavefunction. Thus, choosing a v'' sets R, and determines the Franck-Condon window. The proposed v'' = 39 level has a classical outer turning point at ˜ 72 a_0, and will provide access to higher-n states with longer-range wells. This work is supported by the NSF and AFOSR. [1] M. A. Bellos et al., Phys. Rev. Lett. 111, 053001 (2013)

  19. High-resolution threshold photoelectron and photoion spectroscopy of molecular nitrogen in the 15.0–52.7 eV photon energy range

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • High-resolution threshold photoelectron spectrum of N2 over the photon energy range 15.0–52.7 eV. • High-resolution photoion spectrum of N2 over the photon energy range 15.0–28.0 eV. • Spectroscopic constants for electronic states of N2+ from analyses of vibrational data. • Vibrational assignment of electronic states of N2+. • Rydberg state assignment for series converging on N2+ states. - Abstract: We have performed an extensive study of the threshold photoelectron spectrum of N2 over the valence ionization region 15.0–28.0 eV under high-resolution conditions. In addition, we measured the high-resolution photoion spectrum of N2 over the same photon energy range. These complimentary views of ionization in molecular systems provide different perspectives of the mechanism for the production of both ions and threshold electrons. The studies are presented in the context of our current understanding of the relationship between: (i) the autoionization of neutral Rydberg states and direct photoionization to (ii) the production of electrons and the ionic states of nitrogen at threshold. In both cases (ions and threshold electrons) we have found a considerable amount of new information on the vibrational states of a number of neutral and ionic electronic states. The inner valence ionization region of nitrogen was also investigated using threshold photoelectron spectroscopy over the photon energy range (27.7–52.7 eV) and is presented from the perspective of the formation of mixed-configuration ionic satellite states and the possibility of the involvement of ionic Rydberg states converging on the double ionization of nitrogen

  20. Luminescence of impurity-bound excitons in Li6GdB3O9:Ce3+ single crystals

    International Nuclear Information System (INIS)

    The anomalous (τ 6GdB3O9 doped with trivalent cerium ions, has been revealed for the first time and investigated through the low-temperature time-resolved vacuum ultraviolet synchrotron spectroscopy. It was shown that the optical transitions at 6.2 eV are due to electron transfer from the ground 4f1 states of Ce3+ ion onto the autoionized states near the conduction band bottom of a crystal. These transitions lead to the formation of impurity-bound excitons in the form of correlated electron-hole pair, in which the hole component is localized at 4f-level of the cerium ion and an electron component is located at the conduction band bottom in the attractive potential of this hole. It is established that the direct radiative recombination of the cerium impurity-bound exciton leads to a fast broadband emission at 4.25 eV. The energy threshold for creation of the impurity-bound excitons was determined on the basis of the obtained spectroscopic data. We calculated the H(k) functions of distribution of the elementary relaxations over the reaction rate constants and explained on this basis the decay kinetics and quenching processes, not only for the anomalous emission at 4.25 eV, but for the ordinary 5d-4f luminescence at 3.0 eV in Ce3+ ions. The paper discusses the decay channels for the impurity-bound excitons and their influence on the decay kinetics and spectra of luminescence in Li6GdB3O9 crystals.

  1. Photophysics of fullerenes: Thermionic emission

    Energy Technology Data Exchange (ETDEWEB)

    Compton, R.N. [Univ. of Tennessee, Knoxville, TN (United States)]|[Oak Ridge National Lab., TN (United States); Tuinman, A.A. [Univ. of Tennessee, Knoxville, TN (United States); Huang, J. [Ames Lab., IA (United States)

    1996-09-01

    Multiphoton ionization of fullerenes using long-pulse length lasers occurs mainly through vibrational autoionization. In many cases the laser ionization can be described as thermionic in analogy to the boiling off of electrons from a filament. Thermionic emission manifests itself as a delayed emission of electrons following pulsed laser excitation. Klots has employed quasiequilibrium theory to calculate rate constants for thermionic emission from fullerenes which seem to quantitatively account for the observed delayed emission times and the measured electron energy distributions. The theory of Klots also accounts for the thermionic emission of C{sub 60} excited by a low power CW Argon Ion laser. Recently Klots and Compton have reviewed the evidence for thermionic emission from small aggregates where mention was also made of experiments designed to determine the effects of externally applied electric fields on thermionic emission rates. The authors have measured the fullerene ion intensity as a function of the applied electric field and normalized this signal to that produced by single photon ionization of an atom in order to correct for all collection efficiency artifacts. The increase in fullerene ion signal relative to that of Cs{sup +} is attributed to field enhanced thermionic emission. From the slope of the Schottky plot they obtain a temperature of approximately 1,000 K. This temperature is comparable to but smaller than that estimated from measurements of the electron kinetic energies. This result for field enhanced thermionic emission is discussed further by Klots and Compton. Thermionic emission from neutral clusters has long been known for autodetachment from highly excited negative ions. Similarly, electron attachment to C{sub 60} in the energy range from 8 to 12 eV results in C{sub 60} anions with lifetimes in the range of microseconds. Quasiequilibrium theory (QET) calculations are in reasonable accord with these measurements.

  2. Dissociative recombination of vibrationally excited H{sub 2}{sup +} ions: High-Rydberg-state formation

    Energy Technology Data Exchange (ETDEWEB)

    Chibisov, M.I. [Russian Research Center, Kurchatov Institute, Kurchatov strasse 1, Institute of Nuclear Fusion, Moscow 123182 (Russia); Mitchell, J.B.; Van der Donk, P.J. [Department of Physics, University of Western Ontario, London, Ontario, N6A3K7 (CANADA); Yousif, F.B. [Instituto de Fisica, UNAM, Cuernavaca, (Mexico) 62191; Morgan, T.J. [Physics Department, Wesleyan University, Middletown, Connecticut 06459-0155 (United States)

    1997-07-01

    The dissociative recombination (DR) of vibrationally excited H{sub 2}{sup +} ions to form products in high Rydberg states has been investigated experimentally and theoretically for small (0.01{minus}0.1 eV) center-of-mass energies of the projectile electron. The merged beam method was used in the experiment and very large cross sections were found for DR from highly vibrationally excited states. The Rydberg states population was analyzed by the application of an electric field ionizer with an axial electric field in excess of 70 kV/cm, which is sufficient to ionize Rydberg states with n{ge}10. Experiments with and without the ionizer were performed and cross sections {sigma}(0{lt}n{le}21), {sigma}(n{lt}10), and {sigma}(10{le}n{le}21) were measured. The dipole approximation was used for the interpretation of the experimental results. Molecular rovibrational transitions were considered quantum mechanically. At low collision energy (0.01 eV), DR cross sections with high n=10{minus}21 Rydberg products arise from initial vibrational states v{ge}15. Absolute values of these cross sections are found to be of the order of magnitude of 10{sup {minus}12}{minus}10{sup {minus}13} cm{sup 2}. Comparison of theoretical and experimental results has shown that the modified back autoionization (involving transitions to the continuum and to very high n; that is the {open_quotes}indirect{close_quotes} mechanism of DR) plays a significant role for all cross sections. {copyright} {ital 1997} {ital The American Physical Society}

  3. Advances in NLTE Modeling for Integrated Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Scott, H A; Hansen, S B

    2009-07-08

    The last few years have seen significant progress in constructing the atomic models required for non-local thermodynamic equilibrium (NLTE) simulations. Along with this has come an increased understanding of the requirements for accurately modeling the ionization balance, energy content and radiative properties of different elements for a wide range of densities and temperatures. Much of this progress is the result of a series of workshops dedicated to comparing the results from different codes and computational approaches applied to a series of test problems. The results of these workshops emphasized the importance of atomic model completeness, especially in doubly excited states and autoionization transitions, to calculating ionization balance, and the importance of accurate, detailed atomic data to producing reliable spectra. We describe a simple screened-hydrogenic model that calculates NLTE ionization balance with surprising accuracy, at a low enough computational cost for routine use in radiation-hydrodynamics codes. The model incorporates term splitting, {Delta}n = 0 transitions, and approximate UTA widths for spectral calculations, with results comparable to those of much more detailed codes. Simulations done with this model have been increasingly successful at matching experimental data for laser-driven systems and hohlraums. Accurate and efficient atomic models are just one requirement for integrated NLTE simulations. Coupling the atomic kinetics to hydrodynamics and radiation transport constrains both discretizations and algorithms to retain energy conservation, accuracy and stability. In particular, the strong coupling between radiation and populations can require either very short timesteps or significantly modified radiation transport algorithms to account for NLTE material response. Considerations such as these continue to provide challenges for NLTE simulations.

  4. Study of Isotopic Selectivity in Laser Resonance Ionization of Lutetium Atom%镥的激光共振电离同位素选择性研究

    Institute of Scientific and Technical Information of China (English)

    李志明; 朱凤蓉; 邓虎; 张子斌; 任向军; 翟利华; 韦冠一; 张利兴

    2002-01-01

    本文在速率方程基础上通过数值模拟方法,对镥的激光共振电离通道:5d6s22D3/2(573.655nm)→5d6s6p4F3/2(642.518 nm)→6s6p24P1/2(643.548 nm)→Autoionization state的激光诱导同位素选择性进行了研究.在实际实验条件下用这一方法计算得到的激光波长对激光诱导同位素选择性的关系与实验结果相符合.探讨了在偏振激光作用的情况下各种激光参数(波长、带宽和激光强度)对激光诱导同位素选择性的影响,并提出了在一定实验条件下激光共振电离质谱计较为准确地测定同位素比值的方法.这一理论方法,同样适用于研究其它元素的激光共振电离同位素选择性和选择激光同位素分离电离通道.

  5. Energy redistribution in the dissociation of low Rydberg states of HeH and 02

    International Nuclear Information System (INIS)

    In this thesis the dissocation process is studied of the diatomic molecules, heliumhydride and molecular oxygen. In ch.'s 2-4 results on the spectroscopy and dissociative decay of the excited states of heliumhydride (HeH) are explained. The positions and dissociation pathways of the A2Σ+ and B2Π states are determined and a theoretical description of the decay of these states are given. An isotope dependent dissociation behaviour of the C2/σ+ Rydberg state is reported which explained with this theory. In ch.'s 5-7 observations are presented regarding the first Rydberg states of molecular oxygen. The spectroscopy of the (3sσ)d 1Πg and C3Πg states is treated, and the stability and decay of these Rydberg states is discussed qualitatively. An experimental study is described of the (3sσ)d 1Πg , v=4-8 states. By isotope studies and resolving rotational lines and the measurements of natural linewidths quantitative estimates have been acquired on coupling strengths, positions of repulsive valence states and perturbations reported in literature from REMPI experiments. The electronic coupling strengths between the C3Πg state and the 3Πg valence state has been established. Observed spin-orbit interactions have been quantified and the dissociation of the multiplet states (C3Πg,ω=0-2 has been correlated with the multiplet states of the fragment O3P J=0-2. The spectroscopy of the (3sσ3) Rydberg states which con- verge to and are formed in collisions with the O+2, a4Π μ ion state, is treated. The (3sσ)5/π μ state competition between auto-ionizations and (pre-)dissociation has been observed. 207 refs.; 36 figs.; 18 tabs

  6. Exotic helium molecules; Molecules exotiques d'helium

    Energy Technology Data Exchange (ETDEWEB)

    Portier, M

    2007-12-15

    We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}P{sub 0}) molecule, or a {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 {+-} 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime {tau} = (1.4 {+-} 0.3) {mu}s is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)

  7. Accurate wavelength measurements and modeling of FeXV to FeXIX spectra recorded in high density plasmas between 13.5 to 17 A.

    Energy Technology Data Exchange (ETDEWEB)

    May, M; Beiersdorfer, P; Dunn, J; Jordan, N; Osterheld, A; Faenov, A; Pikuz, T; Skobelev, I; Fora, F; Bollanti, S; Lazzaro, P D; Murra, D; Reale, A; Reale, L; Tomassetti, G; Ritucci, A; Francucci, M; Martellucci, S; Petrocelli, G

    2004-09-28

    Iron spectra have been recorded from plasmas created at three different laser plasma facilities, the Tor Vergata University laser in Rome (Italy), the Hercules laser at ENEA in Frascati (Italy), and the Compact Multipulse Terawatt (COMET) laser at LLNL in California (USA). The measurements provide a means of identifying dielectronic satellite lines from FeXVI and FeXV in the vicinity of the strong 2p {yields} 3d transitions of FeXVII. About 80 {Delta}n {ge} 1 lines of FeXV (Mg-like) to FeXIX (O-like) were recorded between 13.8 to 17.1 {angstrom} with a high spectral resolution ({lambda}/{Delta}{lambda} {approx} 4000), about thirty of these lines are from FeXVI and FeXV. The laser produced plasmas had electron temperatures between 100 to 500 eV and electron densities between 10{sup 20} to 10{sup 22} cm{sup -3}. The Hebrew University Lawrence Livermore Atomic Code (HULLAC) was used to calculate the atomic structure and atomic rates for FeXV to FeXIX. HULLAC was used to calculate synthetic line intensities at T{sub e} = 200 eV and n{sub e} = 10{sup 21}cm{sup -3} for three different conditions to illustrate the role of opacity: optically thin plasmas with no excitation-autoionization/dielectronic recombination (EA/DR) contributions to the line intensities, optically thin plasmas that included EA/DR contributions to the line intensities, and optically thick plasmas (optical depth {approx} 200 {micro}m) that included EA/DR contributions to the line intensities. The optically thick simulation best reproduced the recorded spectrum from the Hercules laser. However some discrepancies between the modeling and the recorded spectra remain.

  8. Penning ionization and photoionization electron spectrometry of hydrogen bromide

    International Nuclear Information System (INIS)

    An electron spectrometric study has been performed on HBr using metastable helium and neon atoms as well as helium resonance photons. High resolution electron spectra were obtained for a mixed He (21S, 23S) beam, a pure He(23S) beam, a mixed Ne(3s3P2,3P0) beam, and for HeI VUV light. From the comparison of vibrational populations of HBr+ (X,v') and HBr+ (A,v'), formed by either He* and Ne* Penning ionization (PI) or HeI photoionization, we conclude that HBr+ (X) formation by PI exhibits only little perturbation of HBr potentials, whereas HBr+ (A) formation by PI exhibits substantial bond stretching of HBr due to metastable atom attack preferably from the H end. For He(21S) + HBr the X- and A-state vibrational peak shapes are substantially broader than for the He(23S) + HBr case pointing to an additional, charge exchange interaction (He+ + HBr-) in the entrance channel of the former system which is also responsible for a broad feature found at lower electron energies in the He(21S,23S) induced PI electron spectra. For the first time, we have detected the low energy electrons in both the He(21S) + HBr and He (23S) + HBr spectra, associated with the major mechanism for the formation of Br+ ions: energy transfer to repulsive HBr** Rydberg states, dissociating to H (1s) and autoionizing Br** atoms. The HBr+ (X) 2Π3/2:2Π1/2 fine structure branching ratios vary significantly with the ionizing agent in a similar way as for the isoelectronic, atomic target case krypton. (orig.)

  9. News and views from the attosecond generation, characterization and applications frontier

    International Nuclear Information System (INIS)

    Complete text of publication follows. We report on recent results in the generation, characterization and applications of energetic attosecond pulse trains and ultra-broad coherent XUV continua: 1) Generation: 1a) We report experimental results confirming contribution of both long and short trajectories in on-axis harmonic generation before, at and after an atomic gas jet, i.e. under three different phase matching conditions. The contribution of both trajectories is manifested through their interference leading to a modulated harmonic (and side band) yield as a function of the driving intensity. 1b) We report the generation of sub-fs pulse trains at the 40 μJ pulse energy level from laser surface plasma, measured through 2nd order intensity volume autocorrelation (2nd order IVAC). 2) Characterization: We present comparative studies between RABITT and 2nd order IVAC in on axis harmonic generation before, at and after an atomic gas jet. We find that the two techniques give fairly different results that are compatible with the differently weighted but unavoidable presence of the long and short trajectory in the generation process in all three phase matching conditions. We show that the relative contributions of the two trajectories can be estimated through RABITT measurements, while spatiotemporal mean pulse durations can be extracted from 2nd order IVAC traces. 3) Applications: 3a) We present time resolved VUV spectroscopy of ultrafast dynamics in molecular ethylene. 3b) We present time resolved XUV spectroscopy at the 1 fs temporal scale and ultra-broad band XUV Fourier Transform Spectroscopy in a manifold of doubly excited autoionizing and inner-shell Auger decaying states excited simultaneously through a coherent broadband XUV continuum. Acknowledgments. This work is supported in part by the European Community's Human Potential Program under contract MTKD-CT-2004-517145 (X-HOMES), the Ultraviolet Laser Facility (ULF) operating at FORTH-IESL (contract PHRI-CT-2001

  10. One-photon two-electron processes in helium close to the double ionization threshold; Diexcitation electronique de l'helium par un photon au voisinage du seuil de double ionisation

    Energy Technology Data Exchange (ETDEWEB)

    Bouri, C

    2007-04-15

    experimental results. We complete this work with the study of doubly excited autoionizing states.

  11. Recombination Reactions and Commissioning of DESIREE

    International Nuclear Information System (INIS)

    By combining electron scattering calculations with structure calculations molecular potential energy curves, couplings and autoionization widths are obtained. Using this molecular data the cross sections of different recombination reactions relevant for the fusion plasma of the Divertor can be calculated. Here electron-molecular ion collisions leading to either dissociative recombination, vibrational excitation (or de-excitation) or dissociative excitation have been studied. Furthermore, the believed presence of H- in the plasma is a motivation for the study of mutual neutralization in collisions between H- and light atomic cations (H+, He+, Be+). We have performed both quantum ab initio as well as semi-classical calculations on reactions involving the H2, HeH and BeH molecular systems. On H2, the focus has been on the mutual neutralization reaction in collisions of H+ and H. An fully quantum ab initio study of the reaction produce total cross section and final state distributions in good agreement with experimental studies. Additionally, the neutralization cross sections are computed for collisions between different isotopes of the hydrogen ions and a very small isotope effects are observed. Furthermore, the differential cross section of the reaction is calculated. A semi- classical Landau-Zener model is used to study the reaction. Different methods to obtain the electronic coupling elements between ionic and covalent states are examined by comparing the semiclassical results with those obtained quantum mechanically. Theoretical studies of dissociative excitation of HeH+ are performed where both the resonant and direct processes are investigated. Calculations on the non-adiabatic couplings between resonant states of HeH are under the way and goal is to perform a fully quantum ab intio study of mutual neutralization in He++H- collisions as well dissociative recombination and resonant ion-pair formation. The direct mechanism of dissociative recombination of BeH+ has

  12. Zinc abundances in Galactic bulge field red giants: Implications for damped Lyman-α systems

    Science.gov (United States)

    Barbuy, B.; Friaça, A. C. S.; da Silveira, C. R.; Hill, V.; Zoccali, M.; Minniti, D.; Renzini, A.; Ortolani, S.; Gómez, A.

    2015-08-01

    Context. Zinc in stars is an important reference element because it is a proxy to Fe in studies of damped Lyman-α systems (DLAs), permitting a comparison of chemical evolution histories of bulge stellar populations and DLAs. In terms of nucleosynthesis, it behaves as an alpha element because it is enhanced in metal-poor stars. Abundance studies in different stellar populations can give hints to the Zn production in different sites. Aims: The aim of this work is to derive the iron-peak element Zn abundances in 56 bulge giants from high resolution spectra. These results are compared with data from other bulge samples, as well as from disk and halo stars, and damped Lyman-α systems, in order to better understand the chemical evolution in these environments. Methods: High-resolution spectra were obtained using FLAMES+UVES on the Very Large Telescope. We computed the Zn abundances using the Zn i lines at 4810.53 and 6362.34 Å. We considered the strong depression in the continuum of the Zn i 6362.34 Å line, which is caused by the wings of the Ca i 6361.79 Å line suffering from autoionization. CN lines blending the Zn i 6362.34 Å line are also included in the calculations. Results: We find [Zn/Fe] = +0.24 ± 0.02 in the range -1.3 < [Fe/H] < -0.5 and [Zn/Fe] = + 0.06 ± 0.02 in the range -0.5 < [Fe/H] < -0.1, whereas for [Fe/H] ≥ -0.1, it shows a spread of -0.60 < [Zn/Fe] < + 0.15, with most of these stars having low [Zn/Fe] < 0.0. These low zinc abundances at the high metallicity end of the bulge define a decreasing trend in [Zn/Fe] with increasing metallicities. A comparison with Zn abundances in DLA systems is presented, where a dust-depletion correction was applied for both Zn and Fe. When we take these corrections into account, the [Zn/Fe] vs. [Fe/H] of the DLAs fall in the same region as the thick disk and bulge stars. Finally, we present a chemical evolution model of Zn enrichment in massive spheroids, representing a typical classical bulge evolution

  13. Defining the buffering process by a triprotic acid without relying on stewart-electroneutrality considerations

    Directory of Open Access Journals (Sweden)

    Kao Liyo

    2011-08-01

    Full Text Available Abstract Upon the addition of protons to an aqueous solution, a component of the H+ load will be bound i.e. buffered. In an aqueous solution containing a triprotic acid, H+ can be bound to three different states of the acid as well as to OH- ions that are derived from the auto-ionization of H2O. In quantifying the buffering process of a triprotic acid, one must define the partitioning of H+ among the three states of the acid and also the OH- ions in solution in order to predict the equilibrium pH value. However, previous quantitative approaches that model triprotic acid titration behaviour and used to predict the equilibrium pH rely on the mathematical convenience of electroneutrality/charge balance considerations. This fact has caused confusion in the literature, and has led to the assumption that charge balance/electroneutrality is a causal factor in modulating proton buffering (Stewart formulation. However, as we have previously shown, although charge balance can be used mathematically as a convenient tool in deriving various formulae, electroneutrality per se is not a fundamental physicochemical parameter that is mechanistically involved in the underlying buffering and proton transfer reactions. The lack of distinction between a mathematical tool, and a fundamental physicochemical parameter is in part a reason for the current debate regarding the Stewart formulation of acid-base analysis. We therefore posed the following question: Is it possible to generate an equation that defines and predicts the buffering of a triprotic acid that is based only on H+ partitioning without incorporating electroneutrality in the derivation? Towards this goal, we derived our new equation utilizing: 1 partitioning of H+ buffering; 2 conservation of mass; and 3 acid-base equilibria. In validating this model, we compared the predicted equilibrium pH with the measured pH of an aqueous solution consisting of Na2HPO4 to which HCl was added. The measured pH values

  14. Isotope effects and spectroscopic assignments in the non-dissociative photoionization spectrum of N{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Randazzo, John B.; Croteau, Philip [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Kostko, Oleg; Ahmed, Musahid [Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Boering, Kristie A. [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Department of Earth and Planetary Science, University of California, Berkeley, California 94720 (United States)

    2014-05-21

    Photoionization efficiency spectra of {sup 14}N{sub 2}, {sup 15}N{sup 14}N, and {sup 15}N{sub 2} from 15.5 to 18.9 eV were measured using synchrotron radiation at the Advanced Light Source at Lawrence Berkeley National Laboratory with a resolution of 6 meV, and significant changes in peak energies and intensities upon isotopic substitution were observed. Previously, we reported the isotope shifts and their applications to Titan's atmosphere. Here, we report more extensive experimental details and tabulate the isotope shifts of many transitions in the N{sub 2} spectrum, including those for {sup 15}N{sup 14}N, which have not been previously reported. The isotope shifts are used to address several long-standing ambiguities in spectral peak assignments just above the ionization threshold of N{sub 2}. The feature at 15.677 eV (the so-called second “cathedral” peak) is of particular interest in this respect. The measured isotope shifts for this peak relative to {sup 14}N{sub 2} are 0.015 ± 0.001 eV for {sup 15}N{sub 2} and 0.008 ± 0.001 eV for {sup 15}N{sup 14}N, which match most closely with the isotope shifts predicted for transitions to the (A {sup 2}Π{sub u} v{sup ′} = 2)4sσ{sub g} {sup 1}Π{sub u} state using Herzberg equations for the isotopic differences in harmonic oscillator energy levels plus the first anharmonic correction of 0.0143 eV for {sup 15}N{sub 2} and 0.0071 eV for {sup 15}N{sup 14}N. More generally, the isotope shifts measured for both {sup 15}N{sub 2} and {sup 15}N{sup 14}N relative to {sup 14}N{sub 2} provide new benchmarks for theoretical calculations of interferences between direct and indirect autoionization states which can interact to produce intricate resonant structures in molecular photoionization spectra in regions near ionization thresholds.

  15. Quantum control of the XUV photoabsorption sp ectrum of helium atoms via the carrier-envelop e-phase of an infrared laser pulse%红外激光载波包络相位对氦原子的极紫外光(XUV)吸收谱的量子调控研究∗

    Institute of Scientific and Technical Information of China (English)

    杨增强; 张力达

    2015-01-01

    In the present paper, we investigate the quantum control of the XUV photoabsorption spectrum of helium atoms via the carrier-envelope-phase (CEP) of an infrared (IR) laser pulse by numerically solving the time-dependent one-dimensional (1D) two-electron Schrödinger equation. The advantage of the 1D model is that the associated time-dependent Schrodinger equation (TDSE) can be solved numerically with high precision as taking full account of the interaction between the electrons and without making any assumptions about the dominant physical mechanisms. In our study, a single attosecond XUV pulse with broad bandwidth is used to create a wave packet consisting of several doubly-excited states. Helium atoms subjected to the XUV pulse can be ionized through two different pathways: either direct ionization into the continuum or indirect ionization via the autoionization of doubly excited states. The interference of these two paths gives rise to the well-known Fano line shape in the photoabsorption spectrum, which is determined by the ratio and relative phases of the two paths. In the presence of an IR laser pulse, however, we find that the Fano line profiles are strongly modified, in good agreement with recent experimental observations [C. Ott et al., Science 340, 716 (2013); C. Ott et al., Nature 516, 374 (2014)]. At certain time delays, we can observe symmetric Lorentz, inverted Fano profiles, and even negative absorption cross sections, indicating that the XUV light can be amplified during the interaction with atoms. We fit the absorption spectra with the Fano line profiles giving rise to the CEP-dependent Fano q parameters, which are modulated from extremely large positive value to extremely large negative value. Since the q parameter is proportional to the ratio between the dipole matrix of the indirect ionization path and the dipole matrix of the direct ionization path;these results indicate that the quantum interference between the two ionization paths can be e

  16. Hundred years of the Einstein theory of photoeffect

    International Nuclear Information System (INIS)

    Full Text:Although H. Hertz discovered the photo-effect experimentally in 1887, the attempts to describe the results obtained in the frame of pre-Einstein theories failed. After publication of Einstein's paper in 1905 the laws of photo-effect became clear, opening new directions in research. The theory of photo-effect has been developed since at first by inclusion of new processes, such as Compton effect, photo-pair production and so on, in which conservation of both energy and momentum plays an equally important role. For many years the atomic photoionization theory was bound to one-electron model, starting with very simple potentials. But even the most sophisticated ones, such as Hartree - Fock approach, failed to describe the experimental findings at the middle of the 60th of the 20th century. It opened the door to the many - electron effects in photoionization. It appeared that along with modification of one-electron picture collective effects are decisively important. The discovery of atomic Giant resonances in photo-effect was a remarkable milestone in atomic photo-effects history. With prediction and observation of other resonances, such as auto-ionization, interference, intra-doublet and phase, the theory included interesting additional physics of electron correlations. Some of these resonances are very well seen in the partial cross-sections, the others require investigation of the dipole and non-dipole angular distribution and photoelectrons spin polarization. A separate domain became the photoionization of two or even three electrons by a single photon, which is until now not completely understood theoretically both in near threshold and in the high photon energy region, where its contribution is much less than that of Compton ionization. The theory of atomic photo-effect is not limited to atoms and ions, both positive and negative. As targets, it considers now multi-atomic formations, such as molecules, fullerenes, and metallic clusters, for all of

  17. Interaction between 4p photoionization and 3p resonant excitation channels of krypton

    International Nuclear Information System (INIS)

    Complete text of publication follows. The angular distribution of Kr 4p photoelectrons was measured employing a linearly polarized photon beam at energies from 205 eV to 230 eV. In this range the Kr 3p→ns/md (n,m=4,5,6, etc.) resonances can be excited. The experimental anisotropy parameters (β, γ and δ) were determined for the Kr 4p shell and its fine structure components. The measurement was carried out at beamline BW3 of the DORIS III synchrotron light source at HASYLAB (Hamburg, Germany). The ESA-22D electrostatic electron spectrometer was used to analyze the emitted electrons. The spectrometer consists of a spherical and a cylindrical mirror analyzer. The spherical mirror focuses the electrons from the scattering plane to the entrance slit of the cylindrical analyzer performing the energy analysis of the electrons. (For detailed description of an ESA- 22-type electron spectrometer see Ref. [1].) The measured dipole anisotropy parameters ? of Kr 4p photoelectrons are shown in Fig. 1 as a function of photon energy. Resonance-like structure can be seen in the photon energy dependence of the dipole parameters. This structure indicates that the channel interactions are important between the 3p resonant excitation-autoionization and 4p direct photoionization processes in krypton. The natural line width of the 3p photoelectron peaks was determined from the measured spectra and it is about 0.8 eV while the experimental width of the resonance near 220 eV photon energy (3p1/2-1→5s resonant excitation) is approximately 2 eV in Fig. 1. This broadening can be explained with the strong interference between the ionization and excitation channels. As before, we conclude that the angular distribution of photoelectrons is strongly influenced by the excitation processes. Acknowledgements. The authors wish to thank the DORIS III staff for providing excellent working conditions. This work was supported by the NKTH-OTKA (Grant No. K67719), and by the European Community

  18. Communication: Direct measurements of nascent O(3P0,1,2) fine-structure distributions and branching ratios of correlated spin-orbit resolved product channels CO(ã3Π; v) + O(3P0,1,2) and CO(Χ~1Σ+; v) + O(3P0,1,2) in VUV photodissociation of CO2

    International Nuclear Information System (INIS)

    We present a generally applicable experimental method for the direct measurement of nascent spin-orbit state distributions of atomic photofragments based on the detection of vacuum ultraviolet (VUV)-excited autoionizing-Rydberg (VUV-EAR) states. The incorporation of this VUV-EAR method in the application of the newly established VUV-VUV laser velocity-map-imaging-photoion (VMI-PI) apparatus has made possible the branching ratio measurement for correlated spin-orbit state resolved product channels, CO(ã3Π; v) + O(3P0,1,2) and CO(Χ~1Σ+; v) + O(3P0,1,2), formed by VUV photoexcitation of CO2 to the 4s(101) Rydberg state at 97,955.7 cm−1. The total kinetic energy release (TKER) spectra obtained from the O+ VMI-PI images of O(3P0,1,2) reveal the formation of correlated CO(ã3Π; v = 0–2) with well-resolved v = 0–2 vibrational bands. This observation shows that the dissociation of CO2 to form the spin-allowed CO(ã3Π; v = 0–2) + O(3P0,1,2) channel has no potential energy barrier. The TKER spectra for the spin-forbidden CO(Χ~1Σ+; v) + O(3P0,1,2) channel were found to exhibit broad profiles, indicative of the formation of a broad range of rovibrational states of CO(Χ~1Σ+)  with significant vibrational populations for v = 18–26. While the VMI-PI images for the CO(ã3Π; v = 0–2) + O(3P0,1,2) channel are anisotropic, indicating that the predissociation of CO2 4s(101) occurs via a near linear configuration in a time scale shorter than the rotational period, the angular distributions for the CO(Χ~1Σ+; v) + O(3P0,1,2) channel are close to isotropic, revealing a slower predissociation process, which possibly occurs on a triplet surface via an intersystem crossing mechanism

  19. Dielectronic recombination of Co-like gold ions

    International Nuclear Information System (INIS)

    Ab initio calculation of the total dielectronic recombination (DR) rate coefficient from the ground and the first excited states of Co-like gold is performed employing the relativistic distorted-wave approximation with configuration interaction. The DR contributions are explicitly taken into account from the relevant complexes of a Ni-like ion: 3d33/2 3d65/2n'l', 3p5 3d10n'l', 3s 3p63d10n'l', 3d8 4ln'l', 3p5 3d9 4ln'l' and 3s 3p6 3d9 4ln'l' with n' ≤ 25, and 3d8 5ln'l' with n' ≤ 9. The contributions from a higher n' complex are evaluated by an extrapolation procedure. The DR contributions mainly come from complex series 3d8 4ln'l' and 3p5 3d9 4ln'l'. The complex series 3p5 3d10n'l' and 3d8 5ln'l' also contribute significantly to the total DR rates at low and high electron temperatures, respectively. The l' and n' dependences of the partial rate coefficient are investigated. The possible important decays into autoionizing levels followed by radiative cascade (DAC) from the resonant levels are taken into account, as well as the resonant stabilizing and non-resonant stabilizing transitions. The inclusion of DAC transitions enlarges the total DR rate coefficients by a factor of about 10% and may break down the usual n'-3 scaling law of the partial DR rates along some complex series. To evaluate the high n' contributions from these complex series, the level-by-level extrapolation method is developed to include DAC effects. The total DR rate coefficients are fitted to an empirical formula. The present results are compared with those from the semiempirical Burgess-Merts approximation. The DR rate coefficients of Ni-like gold are also presented and compared to those of Co-like gold. In addition, some comments on the published DR data for the NiI isoelectronic sequence are drawn from the present calculation

  20. Computational Studies on the Anharmonic Dynamics of Molecular Clusters

    Science.gov (United States)

    Mancini, John S.

    Molecular nanoclusters present ideal systems to probe the physical forces and dynamics that drive the behavior of larger bulk systems. At the nanocluster limit the first instances of several phenomena can be observed including the breaking of hydrogen and molecular bonds. Advancements in experimental and theoretical techniques have made it possible to explore these phenomena in great detail. The most fruitful of these studies have involved the use of both experimental and theoretical techniques to leverage to strengths of the two approaches. This dissertation seeks to explore several important phenomena of molecular clusters using new and existing theoretical methodologies. Three specific systems are considered, hydrogen chloride clusters, mixed water and hydrogen chloride clusters and the first cluster where hydrogen chloride autoionization occurs. The focus of these studies remain as close as possible to experimentally observable phenomena with the intention of validating, simulating and expanding on experimental work. Specifically, the properties of interested are those related to the vibrational ground and excited state dynamics of these systems. Studies are performed using full and reduced dimensional potential energy surface alongside advanced quantum mechanical methods including diffusion Monte Carlo, vibrational configuration interaction theory and quasi-classical molecular dynamics. The insight gained from these studies are great and varied. A new on-they-fly ab initio method for studying molecular clusters is validated for (HCl)1--6. A landmark study of the dissociation energy and predissociation mechanism of (HCl)3 is reported. The ground states of mixed (HCl)n(H2O)m are found to be highly delocalized across multiple stationary point configurations. Furthermore, it is identified that the consideration of this delocalization is required in vibrational excited state calculations to achieve agreement with experimental measurements. Finally, the theoretical

  1. Allowed and forbidden transition parameters for Fe XXII

    International Nuclear Information System (INIS)

    Radiative transitions for photo-excitations and de-excitations in Fe XXII are studied in the relativistic Breit-Pauli approximation. A comprehensive set of fine structure energy levels, oscillator strengths (f), line strengths (S), and radiative decay rates (A) for electric dipole (E1), same spin multiplicity and intercombination, fine structure transitions is presented. These are obtained from the first calculations in the close coupling approximation using the Breit-Pauli R-matrix method for this ion, all existing theoretical results having been obtained from various other atomic structure calculations. The present work obtains a set of 771 fine structure energy levels with n ≤ 10, l ≤ 9, and 1/2 ≤ J ≤ 17/2, only 52 of which have been observed. The f, S, and A values are reported for 70,372 allowed E1 transitions, exceeding by far those published previously. The calculated fine structure levels have been identified spectroscopically using a procedure based on quantum defect analysis. The energies agree with the available observed energies to within less than one to a few percent. The A values for E1 transitions are in good agreement with other existing values for most transitions. Using the atomic structure code SUPERSTRUCTURE (SS), S and A values are also presented for 38,215 forbidden transitions of the types electric quadrupole (E2), electric octupole (E3), magnetic dipole (M1), and magnetic quadrupole (M2) among 274 fine structure levels formed from 25 configurations with orbitals ranging from 1s to 4f. Some of these levels lie above the ionization limit and hence can form autoionizing lines. Such lines for 1s-2p Kα transitions have been observed in experiments. The energies from the SS calculations agree with observed energies within a few percent. The A values for E2 and M1 transitions agree very well with the available values. The atomic parameters for both allowed and forbidden transitions should be applicable for diagnostics as well as complete

  2. Laser Materials and Laser Spectroscopy - A Satellite Meeting of IQEC '88

    Science.gov (United States)

    Wang, Zhijiang; Zhang, Zhiming

    1989-03-01

    Highly Excited Vibrational State * Investigation of the Stark Effect in Xenon Autoionizing Rydberg Series with the Use of Coherent Tunable XUV Radiation * Laser Spectroscopy of Autoionising 5 dnf J = 4.5 Rydberg Series of Ba I * Resonance Photoionization Spectroscopy of Atoms: Autoionization and Highly Excited States of Kr and U * Stark Spectra of Strontium and Calcium Atoms * Observation of Bidirectional Stimulated Radiation at 330 nm, 364 nm and 718 nm with 660 nm Laser Pumping in Sodium Vapour * Study of Molecular Rydberg States and their Discriminations in Na2 * The Measurement of the High Excited Spectra of Samarium by using Stepwise Laser Excitation Method * Product Analysis in the Reaction of the Two-photon Excited Xe(5p56p) States with Freons * Photoionization Spectra of Ca and Sr Atoms above the Classical Field-ionization Threshold * Effect of Medium Background on the Hydrogen Spectrum * Photoemission and Photoelectron Spectra from Autoionizing Atoms in Strong Laser Field * Natural Radiative Lifetime Measurements of High-lying States of Samarium * Two-step Laser Excitation of nf Rydberg States in Neutral Al and Observation of Stark Effect * Measurements of Excited Spectra of the Refractory Metal Elements using Discharge Synchronized with the Laser Pulse * Multiphoton Ionization of Atomic Lead at 1.06μ * Kinetic Processes in the Electron-beam pumped KrF Laser * Laser-induced Fluorescence of Zn2 Excimer * Calculation of Transition Intensity in Heteronuclear Dimer NaK: Comparison with Experiment * Laser-induced Fluorescence of CCl2 Carbene * Study of Multiphoton Ionization Spectrum of Benzene and Two-photon Absorption Cross Section * Dicke Narrowing of N2O Linewidth Perturbed by N2 at 10 μm Band * Polyatomic Molecular Ions Studied by Laser Photodissociation Spectroscopy * Transverse-optically Pumped Ultraviolet S2 Laser * Multiphoton Ionization of Propanal by High Power Laser * UV MPI Mass Spectroscopy and Dynamics of Photodissociation of SO2 * Multiphoton

  3. Stark structure and field ionization characteristics of highly excited Rydberg atoms

    Science.gov (United States)

    Kishimoto, Yasuhiro

    2002-03-01

    The Stark structure and time evolution of highly excited 85Rb Rydberg states in a pulsed electric field have been studied experimentally as well as theoretically. The Rydberg states in 85Rb with the principal quantum number n ranging from 110 to 140 have been excited with the two step laser excitation scheme and field ionization spectra under the pulsed electric field were observed with the ionized electron detection. From the systematic measurements it was found that the in general there exist two peaks in the field ionization spectrum: the lower peak is rather broad and the field value of the peak does not depend on the excitation position in the manifold. The value of the higher peak field, on the other hand, increases with increasing bluer states in the manifold when the pulsed electric field is increased in the same direction with the initially applied static field. However when the pulsed field is increased in the reversed direction to the static field, the peak field value decreases with increasing bluer state excitations, showing the opposite behavior to the case in the same field-driving direction. In order to reveal the origin of these two peak-field values in the ionization process, theoretical calculations of the Stark structure and ionization rates in an electric field have been performed with a computational method based on the Hamiltonian diagonalization. From these calculations it was found that the excitation position dependence of the higher peaks observed in the field ionization is in good agreement with the predictions from the tunneling process. On the other hand the lower peak behavior is roughly explained from the autoionization-like process together with the effect of the blackbody-induced radiative transitions to the neighboring states from the orignally excited states. In due course of the above investigations, time evolution of the multi-level Rydberg system in a pulsed electric field was also studied to confirm the usefulness and

  4. Photonic, Electronic and Atomic Collisions

    Science.gov (United States)

    Fainstein, Pablo D.; Lima, Marco Aurelio P.; Miraglia, Jorge E.; Montenegro, Eduardo C.; Rivarola, Roberto D.

    2006-11-01

    ionization of fixed in space deuterium molecules / T. Weber ... [et al.]. Coherence and intramolecular scattering in molecular photoionization / U. Becker. Experimental observation of interatomic coulombic decay in neon dimers / T. Jahnke ... [et al.]. Ionization by short UV laser pulses: secondary ATI peaks of the electron spectrum / V. D. Rodríguez, E. Cormier and R. Gayet. Molecular frame photoemission in photoionization of H[symbol] and D[symbol]: the role of dissociation on autoionization of the Q[symbol] and Q[symbol] doubly excited states / D. Dowek, M. Lebech and J. C. Houver. 3p photoemission of 3d transition metals - atoms, molecules and clusters / M. Martins -- Collisions involving electrons. Spin-resolved collisions of electrons with atoms and molecules / G. F. Hanne. Calculation of ionization and excitation processes using the convergent close-coupling method / D. V. Fursa, I. Bray and A. T. Stelbovics. The B-spline R-matrix method for electron and photon collisions with atoms and ions / O. Zatsarinny and K. Bartschat. Absolute angle-differential cross sections for excitation of neon atoms electrons of energy 16.6-19.2 eV / M. Allan ... [et al.]. Studies of QED and nuclear size effects with highly charged ions in an EBIT / J. R. Crespo López-Urrutia ... [et al.]. Recombination of astrophysically relevant ions: Be-like C, N, and O / M. Fogle ... [et al.]. Dissociation and excitation of molecules and molecular ions by electron impact / A. E. Orel and J. Royal state-selective X-ray study of the radiative recombination of U[symbol] ions with cooling electrons / M. Pajek ... [et al.]. Electron collisions with trapped, metastable helium / L. J. Uhlmann ... [et al.]. Non-dipole effects in electron and photon impact ionization / N. L. S. Martin. Electron driven processes in atmospheric behaviour / L. Campbell, M. J. Brunger and P. J. 0. Teubner. Calculation of excitation and ionization for electron-molecule collisions at intermediate energies / J. D. Gorfinkiel

  5. Final Report on Atomic Database Project

    International Nuclear Information System (INIS)

    LTE model, the calculation is simple since the Boltzmann distribution can be used. As long as we have the energy levels and the ionization energy, we can calculate the plasma population very easily. However, for the non-LTE model, the calculation is very complex since various atomic data are required to build the transition balance matrix. Currently, empirical formulas are used to calculate these data such as electron collision ionization and autoionization. Furnished with these tested atomic data computing codes, we have developed a friendly user interface and a flexible atomic database [5]. The UTA model is considered the most practical method for medium and high Z elements since it is very time-consuming and difficult to calculate the enormous number of the transitions. However, the UTA model may overestimate the opacity, therefore, the DTA model is desirable even for medium and high Z elements. With the constant decrease in the cost of the disk storage and increase of CPU speed, it is possible to apply the DTA model to the medium and high Z elements. In this project, we calculate opacities for high Z elements in fully detailed term accounting model for significant populated states. For the various rate coefficients, we calculate the data using the detailed configuration accounting approximation. In order to handle the large volume of data generated for medium to high-Z atoms, we use the HDF data format as our database format, which is becoming a standard for storing scientific data. We have built a sophisticated graphical user interface using Java technology to distinguish our atomic database from other existing databases. Unlike other atomic databases, in which the users can obtain the opacity data in a pair of photon energy and opacity, in our database the user can browser more detailed atomic data information other than the opacity data set by combining our atomic database and Java technology. For example, the user can find out the abundant ion stage and

  6. BOOK REVIEW: Computational Atomic Structure

    Science.gov (United States)

    Post, Douglass E.

    1998-02-01

    introduction to atomic structure. It covers single and many electron systems, how to set up a basis set of wavefunctions for a many electron system, LS coupling, single and multi-electron Hamiltonians, the elementary Hartree-Fock approximation and how variational methods are used to determine the ground state energy and wavefunctions. The computational methods used in the codes are outlined and there are exercises at the end of each chapter. For a number of candidate atomic configurations, explicit examples are given that illustrate the physics, the approximations and the computational methods involved, and which provide the reader with the opportunity to check that he is using the suite of codes correctly. Relativistic effects are covered as perturbations with Breit-Pauli Hamiltonians. Isotope and hyperfine level splitting are also covered. A summary chapter covers allowed and forbidden bound-bound transitions. It describes how to set up the matrix elements for transition operators, and the determination of selection rules and computational aspects of the methods for allowed and forbidden lines. The last chapter provides a brief introduction to continuum transitions, including how to compute the necessary wavefunctions to calculate photoionization or photodetachment and autoionization processes. Several appendices provide a summary of angular momentum theory, an introduction to the Dirac and Breit-Pauli theory for relativistic processes, and a description of the input parameters needed to run the programs. In summary, the book is an almost essential guide to anyone planning to use the Multi-Configuration Hartree-Fock suite of codes. With this guide, even someone not thoroughly familiar with the details of the subject or the codes should be able to use them to obtain energy levels, wavefunctions and transition rates for any atomic system of interest. This book serves as a model example for the general computational physics community of how to document an important suite of