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. 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...

  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. 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

  11. Influence of the plasma environment on auto-ionization

    Science.gov (United States)

    Belkhiri, Madeny; Fontes, Christopher J.

    2016-09-01

    In this work, we show the influence of the plasma environment on the auto-ionization rate using an ion-sphere model. We consider transitions from the He-like to the H-like ion stage of aluminum for illustrative purposes, but the approach is completely general and can be applied to arbitrary, highly charged ions. A detailed numerical investigation and comparison is made between two independent computational schemes, using the relativistic configuration-average, distorted-wave approach. We show that the decreasing behavior of the auto-ionization rates as a function of free-electron density is due to a change in the quantum interference between the bound and free electrons, and also provide a qualitative explanation of this trend.

  12. 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.

  13. 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.

  14. 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

  15. 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

  16. Observation of autoionization in O 2 by an electron-electron coincidence method

    Science.gov (United States)

    Doering, J. P.; Yang, J.; Cooper, J. W.

    1995-01-01

    A strong transition to an autoionizing stata has been observed in O 2 at 16.83 ± 0.11 eV by means of a new electron-electron conincidence method. The method uses the fact that electrons arising from autoionizing states appear at a constant energy loss corresponding to the excitation energy of the autoionizing state rather than at a constant ionization potential as do electrons produced by direct ionization. Comparison of the present data with previous photoionization studies suggests that the autoionizing O 2 state is the same state deduced to be responsible for abnormal vibrational intensities in the O 2+X 2Πg ground state when 16.85 eV Ne(I) photons are used. These electron-electron coincidence experiments provide a direct new method for the study of autoionization produced by electron impact.

  17. 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...

  18. 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.

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

    Institute of Scientific and Technical Information of China (English)

    LI ChunYan; WANG TingTing; ZHEN JunFeng; ZHANG Qun; CHEN Yang

    2009-01-01

    Kr atoms were produced in their metastable states 4p55s [3/2]2 and 4p55s' [1/2]0 in a pulsed DC discharge 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 cm-1. 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.

  20. Resonance-Enhanced Photon Excitation Spectroscopy of the Even-Parity Autoionizing Rydberg States of Xe

    Institute of Scientific and Technical Information of China (English)

    Chun-yan Li; Ting-ting Wang; Jun-feng Zhen; Qun Zhang; Yang Chen

    2008-01-01

    Xenon atoms were produced in their metastable states 5p56s[3/2]2 and 5p56s'[1/2]0 in a pulsed DC discharge in a beam, and subsequently excited to the even-parity autoionizing Rydberg states 5p5np' [3/2] 1 ,[1/2]1, t, and 5p5 nf'[5/2]3 using single photon excitation. The excitation spectra of the even-parity autoionizing resonance series from the metastable 129Xe were obtained by recording the autoionized Xe+ with time-of-flight ion detection in the photon energy range of 28000-42000 cm-1. A wealth of autoionizing resonances were newly observed, from which more precise and systematic spectroscopic data of the level energies and quantum defects were derived.

  1. 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.

  2. 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

  3. 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

  4. 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.

  5. 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.

  6. Saturation effects on Ba 6pnl (l= 0, 2) and 6pnk (|M| = 0, 1) autoionization spectra

    Institute of Scientific and Technical Information of China (English)

    Li Shi-Ben; Dai Chang-Jian

    2007-01-01

    Using a three-step laser saturation excitation technique, the saturation effects on the Ba 6pns (J = 1) and 6pnd (J = 1, 3) autoionization spectra are observed systemically in zero field. These saturation spectra are introduced to determine the high n members of 6pnl (l = 0, 2) autoionizing series and are used to analyse the channel interactions among the autoionizing series in zero field. Furthermore, the saturation excitation technique is applied to the electric field case, in which the saturation spectra of Ba 6pnk (|M|= 0, 1) autoionizing Stark states are measured. Most of these saturation spectra are observed for the first time so far as we know, which indicate the mixing of the autoionizing states in the electric fields.

  7. Autoionization and ultrafast relaxation dynamics of highly excited states in N2

    Science.gov (United States)

    Lucchini, M.; Kim, K.; Calegari, F.; Kelkensberg, F.; Siu, W.; Sansone, G.; Vrakking, M. J. J.; Hochlaf, M.; Nisoli, M.

    2012-10-01

    We have used the velocity-map imaging (VMI) technique to measure autoionization dynamics in molecular nitrogen initiated by a train of attosecond pulses. The pump-probe measurements show clear evidence of a crossing between potential energy curves of the highly excited N2+ ion and of the N22+ ion. It is found that the autoionization becomes energetically allowed when the two nuclei are still very close (˜3 Å), in contrast with observations in other diatomic molecules, and that it can be coherently manipulated by a strong femtosecond infrared pulse.

  8. [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

  9. 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

  10. Electron-impact excitation-autoionization of helium in the S-wave limit

    Energy Technology Data Exchange (ETDEWEB)

    Horner, Daniel A.; McCurdy, C. William; Rescigno, Thomas N.

    2004-10-01

    Excitation of the autoionizing states of helium by electron impact is shown in calculations in the s-wave limit to leave a clear signature in the singly differential cross section for the (e,2e) process. It is suggested that such behavior should be seen generally in (e,2e) experiments on atoms that measure the single differential cross section.

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. 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

  16. 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.

  17. 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.)

  18. 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.

  19. Autoionizing doubly-excited states of 3Σg− symmetry of H2

    Directory of Open Access Journals (Sweden)

    Argoubi F.

    2015-01-01

    Full Text Available We report R-matrix calculations of doubly-excited 3Σg− states of molecular hydrogen corresponding to 3d̃πnℓ̃π configurations. These states form Rydberg series converging to the 3d̃π series limit. They lie in the continuum of the doubly-excited states of 3Σg− symmetry built on the 2p̃π ion core, and therefore they are autoionized. Calculations of resonance positions and widths are presented.

  20. 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.

  1. 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.)

  2. 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

  3. Investigation of odd-parity Rydberg states of Eu I with autoionization detection

    Institute of Scientific and Technical Information of China (English)

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

    2009-01-01

    Isolated-core-excitation (ICE) scheme and autoionization detection are employed to study the bound Rydberg states of europium atom. The high-lying states with odd parity have been measured using the autoionization detection method with three different excitation paths via 4f~76s6p[~8P_(5/2)], 4f~76s6p[~8P_(7/2)]and 4f~76s6p[~8P_(9/2)]intermediate states, s respectively. In this paper the spectra of bound Rydberg states of Eu atom are reported, which cover the energy regions from 36000 cm~(-1) to 38250 cm~(-1) and from 38900 cm~(-1) to 39500 cm~(-1). The study provides the information about level energy, the possible J values and relative line intensity as well as the effective principal quantum number n~* for these states. This work not only confirms the previous results of many states, but also discovers 11 new Rydberg states of Eu atom.

  4. 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

  5. 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.

  6. Electromagnetically induced transparency in systems with degenerate autoionizing levels in \\Lambda-configuration

    CERN Document Server

    Dinh, T Bui; Long, V Cao; Peřina, J

    2013-01-01

    We discuss a \\Lambda-like model of atomic levels involving two autoionizing (AI) states of the same energy. The system is irradiated by two external electromagnetic fields (strong -- driving and weak -- probing ones). For such a system containing degenerate AI levels we derive the analytical formula describing the medium susceptibility. We show that the presence of the second AI level lead to the additional electromagnetically induced transparency (EIT) window appearance. We show that the characteristic of this window can be manipulated by changes of the parameters describing the interactions of AI levels with other ones. This is a new mechanism which leads to additional transparency windows in EIT model, that differs from the mechanism, where a bigger number of Zeeman sublevels is taken into account.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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...

  12. 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...

  13. 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.

  14. 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.

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

    Science.gov (United States)

    Zhang, Kai; Shen, Li; Dong, Cheng; Dai, Chang-Jian

    2015-10-01

    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 8 DJ (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. Project supported by the National Natural Science Foundation of China (Grant No. 11174218).

  16. 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.

  17. 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

  18. 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:

  19. 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.)

  20. 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 ...

  1. 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

  2. Out-of-plane (e , 2 e) measurements on He autoionizing levels at 80, 150, and 488 eV

    Science.gov (United States)

    Martin, N. L. S.; Kim, B. N.; Weaver, C. M.; Deharak, B. A.; Bartschat, K.

    2016-05-01

    We report out-of-scattering-plane (e , 2 e) measurements on helium 2 l 2l' autoionizing levels for 80, 150, and 488 eV incident electron energies, and scattering angles 60°, 39. 2°, and 20. 5°, respectively. The kinematics are the same in all cases: ejected electrons are detected in a plane that contains the momentum transfer direction and is perpendicular to the scattering plane, and the momentum transfer is 2.1 a.u.. The 80 eV results complete our sets of measurements at low, intermediate, and high, incident energies. The results are presented as (e , 2 e) angular distributions energy-integrated over each level, and are compared with our theory calculated for 488 eV incident electron energy. The 150 eV and 488 eV experiments are characterized by recoil peaks appropriate to each autoionizing level. However, for the 80 eV angular distributions, these recoil peaks are largely absent for all levels, including the 3 P level observed at this energy. This work was supported by the National Science Foundation under Grants Nos. PHY-0855040 (NLSM), PHY-1402899 (BAdH), and PHY-1212450 (KB).

  3. 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.)

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. Autoionization of Be-like ions following double electron capture in C sup 4+ , O sup 6+ and Ne sup 8+ ions

    Energy Technology Data Exchange (ETDEWEB)

    McDonald, J.W.

    1990-09-11

    This paper describes electron emission following the autoionization of doubly excited states in Be-like ions. The Be-like Auger states are produced by two electron capture in slow C{sup 4+}, O{sup 6+} and Ne{sup 8+} ions. These measurements were performed by means of high resolution Auger electron spectroscopy on different target gases and at different projectile energies. Line assignments and relative cross sections are given for the investigated doubly excited states and the excitation mechanism is discussed. 15 refs., 16 figs., 4 tabs.

  9. 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...

  10. 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.

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

    Institute of Scientific and Technical Information of China (English)

    Jia Feng-Dong; Wang Jing-Yang; Zhong Zhi-Ping

    2008-01-01

    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+.

  12. 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.

  13. 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)

  14. 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.)

  15. 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.

  16. 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...

  17. 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

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. Autoionization of water: does it really occur?

    CERN Document Server

    Artemov, V G; Sysoev, N N; Volkov, A A

    2015-01-01

    The ionization constant of water Kw is currently determined on the proton conductivity sigma1 which is measured at frequencies lower than 10^7 Hz. Here, we develop the idea that the high frequency conductivity sigma2 (~10^11 Hz), rather than sigma1 represents a net proton dynamics in water, to evaluate the actual concentration c of H3O+ and OH- ions from sigma2. We find c to be not dependent on temperature to conclude that i) water electrodynamics is due to a proton exchange between H3O+ (or OH-) ions and neutral H2O molecules rather than spontaneous ionization of H2O molecules, ii) the common Kw (or pH) reflects the thermoactivation of the H3O+ and OH- ions from the potential of their interaction, iii) the lifetime of a target water molecule does not exceed parts of nanosecond.

  4. 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.

  5. 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.

  6. 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.

  7. 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.)

  8. 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

  9. 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...

  10. 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)

  11. 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

  12. Autoionization Rates Coefficients of Highly Ionized State in SOSA Model%SOSA模型下高剥离态的自电离系数

    Institute of Scientific and Technical Information of China (English)

    焦荣珍; 程新路; 李小红; 杨向东

    2001-01-01

    在SOSA模型下,计算得出Ni-like、Cu-like、Zn-like(Xe、Gd、Dy、Au)的3d-nf(n=4,5,6)的自电离系数Aa,结果表明,由于旁观电子对slater积分Rk的影响,使自电离系数呈规律性变化,同时对Ta45+的自电离系数与采用相对论参数势方法得出的自电离系数作了比较,结果比较一致.

  13. 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

  14. 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.

  15. 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

  16. Level-resolved distorted-wave cross-sections of electron impact ionization of Ar{sup 5+}

    Energy Technology Data Exchange (ETDEWEB)

    Yumak, A; Yavuz, I; Altun, Z, E-mail: zikalt@superonline.co [Department of Physics, Marmara University, Istanbul, 34722 (Turkey)

    2009-11-01

    Electron impact ionization cross sections of Ar{sup 5+} were calculated using configuration-average (CADW) and level-resolved (LRDW) distorted-wave methods. Direct ionization cross-sections of 2s, 2p, 3s and 3p subshells were calculated within a CADW approximation. The contributions from the excitation autoionization channels were evaluated assuming single excitations from the 2s, 2p, and 3s subshells and in both CADW and LRDW methods. The radiative stabilization of the excitation autoionization channels were found to reduce the excitation autoionization by a small amount.

  17. 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

  18. 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.

  19. REMPI Spectroscopy of HfF

    CERN Document Server

    Loh, Huanqian; Yahn, Tyler S; Looser, Herbert; Field, Robert W; Cornell, Eric A

    2012-01-01

    The spectrum of electronic states at 30000--33000 cm$^{-1}$ in hafnium fluoride has been studied using (1+1) resonance-enhanced multi-photon ionization (REMPI) and (1+1$'$) REMPI. Six $\\Omega' = 3/2$ and ten $\\Pi_{1/2}$ vibronic bands have been characterized. We report the molecular constants for these bands and estimate the electronic energies of the excited states using a correction derived from the observed isotope shifts. When either of two closely spaced $\\Pi_{1/2}$ electronic states is used as an intermediate state to access autoionizing Rydberg levels, qualitatively distinct autoionization spectra are observed. The intermediate state-specificity of the autoionization spectra bodes well for the possibility of using a selected $\\Pi_{1/2}$ state as an intermediate state to create ionic HfF$^+$ in various selected quantum states, an important requirement for our electron electric dipole moment (eEDM) search in HfF$^+$.

  20. 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.

  1. 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...

  2. 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.

  3. 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.

  4. 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.

  5. The attosecond regime of impulsive stimulated electronic Raman excitation

    CERN Document Server

    Ware, Matthew R; Cryan, James P; Haxton, Daniel J

    2016-01-01

    We have calculated the resonant and nonresonant contributions to attosecond impulsive stimulated electronic Raman scattering (SERS) in regions of autoionizing transitions. Comparison with Multiconfiguration Time-Dependent Hartree-Fock (MCTDHF) calculations find that attosecond SERS is dominated by continuum transitions and not autoionizing resonances. These results agree quantitatively with a rate equation that includes second-order Raman and first-and second-order photoionization rates. Such rate models can be extended to larger molecular systems. Our results indicate that attosecond SERS transition probabilities may be understood in terms of two-photon generalized cross sections even in the high-intensity limit for extreme ultraviolet wavelengths.

  6. 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

  7. 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

  8. 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.

  9. Understanding Chemical Equilibrium Using Entropy Analysis: The Relationship between [delta]S[subscript tot](sys[superscript o]) and the Equilibrium Constant

    Science.gov (United States)

    Bindel, Thomas H.

    2010-01-01

    Entropy analyses as a function of the extent of reaction are presented for a number of physicochemical processes, including vaporization of a liquid, dimerization of nitrogen dioxide, and the autoionization of water. Graphs of the total entropy change versus the extent of reaction give a visual representation of chemical equilibrium and the second…

  10. 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.

  11. 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

  12. 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)

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

    KAUST Repository

    Efimov, D K

    2016-05-18

    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 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 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. © 2016 IOP Publishing Ltd.

  14. 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.

  15. Resonance Excitation Rate Coefficient of Ni-Like Tantalum

    Institute of Scientific and Technical Information of China (English)

    SHEN Tian-Ming; CHEN Chong-Yang; WANG Yan-Sen; GU Ming-Feng

    2007-01-01

    The ab initio calculations of electron-impact resonant excitation rate coefficients from the ground level to 54 fine-structure levels of 3d941(l=s,p,d,f)configurations of Ni-like tantalum ion are performed by using a fully relativistic distorted-wave approximation.The configuration-interaction effects are taken into account.The decays to autoionizing levels possibly followed by autoionization cascades are also included in the calculation.The contributions from doubly-excited intermediate states of Cu-like 3l17n'l'n"l"(n'=4,5;n"=5-15)arecalculated explicitly,and the contributions from high Rydberg states(n">15)are taken into account by using n-3 scaling law.The present results should be more accurate than the existent calculations.

  16. 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

  17. 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

  18. 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.

  19. 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)

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. A Young double-slit experiment using a single electron source: Oscillations in the angular distribution of Auger-line width

    Energy Technology Data Exchange (ETDEWEB)

    Fremont, F; Chesnel, J-Y [Universite de Caen-CEA-CNRS-EnsiCaen-CIMAP, 6 bd du Mal Juin, F-14050 Caen Cedex (France); Barrachina, R O; Suarez, S, E-mail: francois.fremont@ensicaen.f, E-mail: barra@cab.cnea.gov.a [Centro Atomico Bariloche and Instituto Balseiro 8400 S. C. de Bariloche, Rio Negro (Argentina)

    2009-11-01

    We present evidence for two-center interference effects in the autoionization of a Helium atom following a double capture process in a He''2''+ + H{sub 2} collision, by looking, not at the total intensity as in a previous article [1], but at the full width at half maximum of the energy distribution at a function of the observation angle.

  5. 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...

  6. Photoionization of He in the 3lnl' doubly-excited state energy region: angular distribution of the fluorescence from the residual ion He{sup +}(2p){sup 2}P

    Energy Technology Data Exchange (ETDEWEB)

    Harries, James R [Photon Factory, IMSS, KEK, 1-1 Oho, Tsukuba 305-0081 (Japan); Sullivan, James P [Atomic and Molecular Physics Laboratories, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT (Australia); Hammond, Peter [School of Physics, CAMSP, University of Western Australia, Nedlands, Perth (Australia); Azuma, Yoshiro [Photon Factory, IMSS, KEK, 1-1 Oho, Tsukuba 305-0081 (Japan)

    2006-12-14

    We present experimental observations of the photoexcitation of 3lnl' doubly-excited states of helium decaying by autoionization into the (2p){sup 2}P excited ion final-state channel. By determining the angular distribution of the fluorescence from the final ion state, the alignment of the ion and hence the partial 2pks and 2pkd cross-sections are determined and compared to recent theoretical calculations.

  7. Partial photoionization of helium into the 2s{sup 2}S and 2p{sup 2}P ion states in the 3lnl' doubly-excited states region

    Energy Technology Data Exchange (ETDEWEB)

    Harries, James R [Photon Factory, IMSS, KEK, 1-1 Oho, Tsukuba 305-0081 (Japan); Sullivan, James P [Photon Factory, IMSS, KEK, 1-1 Oho, Tsukuba 305-0081 (Japan); Obara, Satoshi [Photon Factory, IMSS, KEK, 1-1 Oho, Tsukuba 305-0081 (Japan); Azuma, Yoshiro [Photon Factory, IMSS, KEK, 1-1 Oho, Tsukuba 305-0081 (Japan); Lambourne, J G [LDIAM, Universite P and M Curie, 75252 Paris 5 (France); Penent, F [LDIAM, Universite P and M Curie, 75252 Paris 5 (France); Hall, R I [LDIAM, Universite P and M Curie, 75252 Paris 5 (France); Lablanquie, P [LURE, Bat.209D, Centre Universitaire Paris-Sud, BP34, 91898 ORSAY Cedex (France); Bucar, K [J Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Zitnik, M [J Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Hammond, Peter [CAMSP, School of Physics, University of Western Australia, Crawlay, WA 6009, Perth (Australia)

    2005-05-28

    We present experimental observations of the auto-ionization of 3lnl' doubly-excited states of helium into the 2s{sup 2}S and 2p{sup 2}P excited ion final-state channels using time-resolved detection techniques to separate the decay routes. A qualitative comparison to previously published theoretical results is given. (letter to the editor)

  8. 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

  9. 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

  10. 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)

  11. 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.

  12. 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...

  13. 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...

  14. 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.

  15. 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...

  16. 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)

  17. 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.

  18. 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

  19. 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.

  20. 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)

  1. 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

  2. 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

  3. Dye laser chain for laser isotope separation

    Science.gov (United States)

    Doizi, Denis; Jaraudias, Jean; Pochon, E.; Salvetat, G.

    1993-05-01

    Uranium enrichment by laser isotope separation uses a three step operation which requires four visible wavelengths to boost an individual U235 isotope from a low lying atomic energy level to an autoionizing state. The visible wavelengths are delivered by dye lasers pumped by copper vapor lasers (CVL). In this particular talk, a single dye chain consisting of a master oscillator and amplifier stages will be described and some of its performance given.

  4. 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.

  5. 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...

  6. 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].

  7. 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

  8. 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)

  9. 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

  10. Cluster model for the ionic product of water: accuracy and limitations of common density functional methods.

    Science.gov (United States)

    Svozil, Daniel; Jungwirth, Pavel

    2006-07-27

    In the present study, the performance of six popular density functionals (B3LYP, PBE0, BLYP, BP86, PBE, and SVWN) for the description of the autoionization process in the water octamer was studied. As a benchmark, MP2 energies with complete basis sets limit extrapolation and CCSD(T) correction were used. At this level, the autoionized structure lies 28.5 kcal.mol(-1) above the neutral water octamer. Accounting for zero-point energy lowers this value by 3.0 kcal.mol(-1). The transition state of the proton transfer reaction, lying only 0.7 kcal.mol(-1) above the energy of the ionized system, was identified at the MP2/aug-cc-pVDZ level of theory. Different density functionals describe the reactant and product with varying accuracy, while they all fail to characterize the transition state. We find improved results with hybrid functionals compared to the gradient-corrected ones. In particular, B3LYP describes the reaction energetics within 2.5 kcal.mol(-1) of the benchmark value. Therefore, this functional is suggested to be preferably used both for Carr-Parinello molecular dynamics and for quantum mechanics/molecular mechanics (QM/MM) simulations of autoionization of water.

  11. 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.

  12. 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

  13. 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.

  14. Optically Forbidden Excitations of 2s Electron of Neon Studied by Fast Electron Impact

    Institute of Scientific and Technical Information of China (English)

    GE Min; ZHU Lin-Fan; LIU Cun-Ding; XU Ke-Zun

    2008-01-01

    The electron energy loss spectrum in the energy region of 42-48.5 eV of neon is measured with an angle-resolved fast-electron energy-loss spectrometer at an incident electron energy of 2500eV. Besides the dipole-allowed autoionization transitions of 2s-1np (n = 3, 4) and 2p-23s3p, the dipole-forbidden ones of 2s-1ns (n = 3 - 6) and 2s-13d are observed. The line profile parameters, i.e. ET, F and q for these transitions, are determined, and the momentum transfer dependence behaviour is discussed.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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)

  3. EUV ionization of pure He nanodroplets: Mass-correlated photoelectron imaging, Penning ionization and electron energy-loss spectra

    CERN Document Server

    Buchta, D; Brauer, N B; Drabbels, M; O'Keeffe, P; Devetta, M; Di Fraia, M; Callegari, C; Richter, R; Coreno, M; Prince, K C; Stienkemeier, F; Moshammer, R; Mudrich, M

    2013-01-01

    The ionization dynamics of pure He nanodroplets irradiated by EUV radiation is studied using Velocity-Map Imaging PhotoElectron-PhotoIon COincidence (VMI-PEPICO) spectroscopy. We present photoelectron energy spectra and angular distributions measured in coincidence with the most abundant ions He+, He2+, and He3+. Surprisingly, below the autoionization threshold of He droplets we find indications for multiple excitation and subsequent ionization of the droplets by a Penning-like process. At high photon energies we evidence inelastic collisions of photoelectrons with the surrounding He atoms in the droplets.

  4. 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.

  5. 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.

  6. Signature of triply excited Li-like V states in ion-solid collisions

    Science.gov (United States)

    Sharma, Gaurav; Haris, K.; Singh, G.; Kumar, B.; Karmakar, S.; Puri, N. K.; Mishra, Adya P.; Kumar, Pravin; Nandi, T.

    2016-10-01

    The transitions originating from triply excited, doubly autoionizing states of Li-like V formed in beam-foil experiments detected within a set of blended spectroscopic profiles have been assigned tentatively by the Hartree-Fock calculations including relativistic corrections and multi-configuration interactions as perturbations. The x-ray decay channels from the triply excited states such as 3p34S, 2p2 np4S (n ∼ 12) through radiative transitions to the ground state via two or more steps have been observed.

  7. Absolute vacuum ultraviolet photoabsorption cross section studies of atomic and molecular species: Techniques and observational data

    Science.gov (United States)

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

    1990-01-01

    Absorption of a high energy photon (greater than 6 eV) by an isolated molecule results in the formation of highly excited quasi-discrete or continuum states which evolve through a wide range of direct and indirect photochemical processes. These are: photoionization and autoionization, photodissociation and predissociation, and fluorescence. The ultimate goal is to understand the dynamics of the excitation and decay processes and to quantitatively measure the absolute partial cross sections for all processes which occur in photoabsorption. Typical experimental techniques and the status of observational results of particular interest to solar system observations are presented.

  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. 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.

  10. 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.

  11. The dielectronic recombination process in laser-produced Au plasmas

    Institute of Scientific and Technical Information of China (English)

    焦荣珍; 程新路; 杨向东

    2003-01-01

    The calculations of the rate coefficients for dielectronic recombination (DR) along the NiI isoelectronic sequence in the ground state Au51+ through Cu-like 3d9nln′f (n, n′=4,5,6) inner-shell excited configurations are performed using the spin-orbit-split array (SOSA) model Resonant and nonresonant radiative stabilizing transitions and decays to autoionizing levels followed by radiative cascades are included. Collisional transitions following electron capture are neglected. The trend of the DR rate coefficients and the ratio of dielectronic satellite lines intensities with the change of the electron temperature are discussed.

  12. 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...

  13. 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.

  14. 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.

  15. 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...

  16. 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.

  17. 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.

  18. 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.

  19. 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)

  20. 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.

  1. 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

  2. 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.

  3. 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)

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. Relaxation Processes in Aqueous Systems upon X-ray Ionization: Entanglement of Electronic and Nuclear Dynamics.

    Science.gov (United States)

    Slavíček, Petr; Kryzhevoi, Nikolai V; Aziz, Emad F; Winter, Bernd

    2016-01-21

    The knowledge of primary processes following the interaction of high-energy radiation with molecules in liquid phase is rather limited. In the present Perspective, we report on a newly discovered type of relaxation process involving simultaneous autoionization and proton transfer between adjacent molecules, so-called proton transfer mediated charge separation (PTM-CS) process. Within PTM-CS, transients with a half-transferred proton are formed within a few femtoseconds after the core-level ionization event. Subsequent nonradiative decay of the highly nonequilibrium transients leads to a series of reactive species, which have not been considered in any high-energy radiation process in water. Nonlocal electronic decay processes are surprisingly accelerated upon proton dynamics. Such strong coupling of electronic and nuclear dynamics is a general phenomenon for hydrogen-bonded systems, however, its probability correlates strongly with hydration geometry. We suggest that the newly observed processes will impact future high-energy radiation-chemistry-relevant modeling, and we envision application of autoionization spectroscopy for identification of solution structure details. PMID:26712083

  3. STUDIES OF ELECTRON CORRELATION IN THE PHOTOIONIZATION PROCESS

    Energy Technology Data Exchange (ETDEWEB)

    Rosenberg, Richard Allen

    1979-03-01

    Electron correlation is a result of the interaction of two or more electrons confined in a region of space, and may conveniently be treated under the formalism of configuration interaction (CI). Photoionization provides a rather direct experimental method for studying configuration interaction. The types of CI involved in the photoionization process can be divided into three categories: initial state configuration interaction (ISCI), final ionic state configuration interaction (FISCI), and continuum state configuration interaction (CSCI). This thesis deals with experimental studies which reveal how the various types of CI may become manifested in photoionization. The experimental methods utilized in this work are photoelectron spectroscopy (PES), electron impact spectroscopy (EIS), and time-resolved fluorescence spectroscopy. The EIS was carried out following the discovery that the UV lamp on a Perkin-Elmer photoelectron spectrometer could be utilized as a source of low energy electrons. The time-resolved fluorescence work utilized both the tunability and the time structure of the radiation available at the Stanford Synchrotron Radiation Laboratory (SSRL). A commercial photoelectron spectrometer equipped with a conventional UV lamp (Hei, Nei) was employed for some of the PES studies, and a novel time-of-flight photoelectron spectrometer was developed for the PES work performed using synchrotron radiation. The PES of Ba, Sm, Eu, and Yb was studied using both Hei (22.22 eV) and Nei (16.85 eV) radiation. Satellite structure observed in these spectra using Nei (and for Yb, Hei also) radiation could be satisfactorily explained by ISCI alone. The Hei spectra of Sm, Eu, and, in particular, Ba showed dramatic changes in the satellite population which could only be explained by a new mechanism, autoionization, which is a special form of CSCI. The detailed nature of this mechanism was explored in Ba using synchrotron radiation. It was found that the autoionizing level decays

  4. Analysis and modeling of Fano resonances using equivalent circuit elements.

    Science.gov (United States)

    Lv, Bo; Li, Rujiang; Fu, Jiahui; Wu, Qun; Zhang, Kuang; Chen, Wan; Wang, Zhefei; Ma, Ruyu

    2016-08-22

    Fano resonance presents an asymmetric line shape formed by an interference of a continuum coupled with a discrete autoionized state. In this paper, we show several simple circuits for Fano resonances from the stable-input impedance mechanism, where the elements consisting of inductors and capacitors are formulated for various resonant modes, and the resistor represents the damping of the oscillators. By tuning the pole-zero of the input impedance, a simple circuit with only three passive components e.g. two inductors and one capacitor, can exhibit asymmetric resonance with arbitrary Q-factors flexiblely. Meanwhile, four passive components can exhibit various resonances including the Lorentz-like and reversely electromagnetically induced transparency (EIT) formations. Our work not only provides an intuitive understanding of Fano resonances, but also pave the way to realize Fano resonaces using simple circuit elements.

  5. High-resolution dipole (e, e) study for optical oscillator strengths of helium

    Institute of Scientific and Technical Information of China (English)

    凤任飞; 杨炳忻; 武淑兰; 邢士林; 张芳; 钟志萍; 郭学哲; 徐克尊

    1996-01-01

    The optical oscillator strengths of helium have been studied by a high-resolution dipole (e, e) method on the recently built high-resolution fast-electron energy-loss spectrometer. The difficulties of optical measurement have been avoided and the experimental precision has been improved by using this method. The optical oscillator strength density spectrum corresponding to the 1S n’P transitions and ionization of helium has been measured in the energy loss range of 21 - 26 eV. And the same work corresponding to the autoionization resonance region has been done in energy loss ranges of 59-67 eV and 69-74 eV. The above results have also been compared with those of the previous work.

  6. 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.

  7. 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.

  8. Ultrafast electro-nuclear dynamics of H2 double ionization

    CERN Document Server

    Saugout, Sebastien; Suzor-Weiner, Annick; Charron, Eric; 10.1103/PhysRevLett.98.253003

    2011-01-01

    The ultrafast electronic and nuclear dynamics of H2 laser-induced double ionization is studied using a time-dependent wave packet approach that goes beyond the fixed nuclei approximation. The double ionization pathways are analyzed by following the evolution of the total wave function during and after the pulse. The rescattering of the first ionized electron produces a coherent superposition of excited molecular states which presents a pronounced transient H+H- character. This attosecond excitation is followed by field-induced double ionization and by the formation of short-lived autoionizing states which decay via double ionization. These two double ionization mechanisms may be identified by their signature imprinted in the kinetic-energy distribution of the ejected protons.

  9. 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.

  10. 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.

  11. 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)

  12. 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)

  13. 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.

  14. 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)

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

    Science.gov (United States)

    Tirnakli, Ugur; Borges, Ernesto P

    2016-03-23

    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.

  16. 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.

  17. The influence of crater formation for electron excitation processes in cluster induced collision cascades

    Energy Technology Data Exchange (ETDEWEB)

    Weidtmann, B.; Duvenbeck, A.; Wucher, A.

    2015-06-01

    The interplay between electronic energy loss and the excitation of electronic degrees of freedom accompanying the bombardment of a silver crystal with 7-keV Ag and 20-keV Ag{sub 3} particles is investigated by molecular dynamics simulation. Two kinetic excitation processes – the friction of moving atoms in a free electron gas and autoionization in close, binary collisions – are considered, as to describe the electronic stopping. In order to accommodate the massive transient morphology changes following a cluster impact, the electronic friction is described by a modified Lindhard/Scharff model, where the friction coefficient is scaled to the local environment of a moving atom. It is shown that this approach is capable of reproducing both the measured sputter yields and the degree of electronic excitation as manifested by measured electron and secondary ion yields.

  18. Determination of ionization potential of atomic gadolinium and its isotope effect. Analysis of unperturbed Rydberg series

    Energy Technology Data Exchange (ETDEWEB)

    Miyabe, Masabumi; Ohba, Masaki; Wakaida, Ikuo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1997-10-01

    Autoionizing Rydberg series converging to six states (0, 261.841, 633.273, 3082.011, 3427.274, 3444.235 cm{sup -1}) of Gd ion have been observed by using three-color three-step photoionization via ten different 2nd-step levels of J=0 or 1. While the perturbations with interlopers become significant in the region of n=30-35 for most of the observed series, long and well-defined series structures appeared in higher energy region. From an analysis of such unperturbed structures, the first ionization potential of Gd atom was estimated to be 49601.45 (30) cm{sup -1}. This is in good agreement with the previous value, but the accuracy is improved by about one order of magnitude. In addition, isotope effect on the ionization potential was also determined by isotope shifts of some Rydberg series. (author)

  19. Free-carrier generation in aggregates of single-wall carbon nanotubes by photoexcitation in the ultraviolet regime.

    Science.gov (United States)

    Crochet, Jared J; Hoseinkhani, Sajjad; Lüer, Larry; Hertel, Tobias; Doorn, Stephen K; Lanzani, Guglielmo

    2011-12-16

    We present evidence for the generation of free carriers in aggregated single-wall carbon nanotubes by photoexcitation in the energetic range of the π→π(*) transition associated with the M saddle point of the graphene lattice. The underlying broad absorption culminating at 4.3 eV can be fit well with a Fano line shape that describes strong coupling of a saddle-point exciton to an underlying free electron-hole pair continuum. Moreover, it is demonstrated that transitions in this energetic region autoionize into the continuum by detecting features unique to the presence of free charges in the transient transmission spectra of the continuum-embedded second sub-band exciton, S(2).

  20. 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

  1. 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}

  2. 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.

  3. Lorentz meets Fano in spectral line shapes: a universal phase and its laser control.

    Science.gov (United States)

    Ott, Christian; Kaldun, Andreas; Raith, Philipp; Meyer, Kristina; Laux, Martin; Evers, Jörg; Keitel, Christoph H; Greene, Chris H; Pfeifer, Thomas

    2013-05-10

    Symmetric Lorentzian and asymmetric Fano line shapes are fundamental spectroscopic signatures that quantify the structural and dynamical properties of nuclei, atoms, molecules, and solids. This study introduces a universal temporal-phase formalism, mapping the Fano asymmetry parameter q to a phase φ of the time-dependent dipole response function. The formalism is confirmed experimentally by laser-transforming Fano absorption lines of autoionizing helium into Lorentzian lines after attosecond-pulsed excitation. We also demonstrate the inverse, the transformation of a naturally Lorentzian line into a Fano profile. A further application of this formalism uses quantum-phase control to amplify extreme-ultraviolet light resonantly interacting with He atoms. The quantum phase of excited states and its response to interactions can thus be extracted from line-shape analysis, with applications in many branches of spectroscopy. PMID:23661754

  4. 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

  5. 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.

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

    Science.gov (United States)

    Juarez, A. M.; Redt, E.; Hoenert, M.; Hoyos-Campo, L. M.; Rolles, D.; Berrah, N.; Aguilar, A.

    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, 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.

  7. 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.

  8. Analysis and modeling of Fano resonances using equivalent circuit elements

    Science.gov (United States)

    Lv, Bo; Li, Rujiang; Fu, Jiahui; Wu, Qun; Zhang, Kuang; Chen, Wan; Wang, Zhefei; Ma, Ruyu

    2016-08-01

    Fano resonance presents an asymmetric line shape formed by an interference of a continuum coupled with a discrete autoionized state. In this paper, we show several simple circuits for Fano resonances from the stable-input impedance mechanism, where the elements consisting of inductors and capacitors are formulated for various resonant modes, and the resistor represents the damping of the oscillators. By tuning the pole-zero of the input impedance, a simple circuit with only three passive components e.g. two inductors and one capacitor, can exhibit asymmetric resonance with arbitrary Q-factors flexiblely. Meanwhile, four passive components can exhibit various resonances including the Lorentz-like and reversely electromagnetically induced transparency (EIT) formations. Our work not only provides an intuitive understanding of Fano resonances, but also pave the way to realize Fano resonaces using simple circuit elements.

  9. Lorentz meets Fano spectral line shapes: A universal phase and its laser control

    CERN Document Server

    Ott, Christian; Raith, Philipp; Meyer, Kristina; Laux, Martin; Evers, Jörg; Keitel, Christoph H; Greene, Chris H; Pfeifer, Thomas

    2013-01-01

    Symmetric Lorentzian and asymmetric Fano line shapes are fundamental spectroscopic signatures that quantify the structural and dynamical properties of nuclei, atoms, molecules, and solids. This study introduces a universal temporal-phase formalism, mapping the Fano asymmetry parameter q to a phase {\\phi} of the time-dependent dipole-response function. The formalism is confirmed experimentally by laser-transforming Fano absorption lines of autoionizing helium into Lorentzian lines after attosecond-pulsed excitation. We also prove the inverse, the transformation of a naturally Lorentzian line into a Fano profile. A further application of this formalism amplifies resonantly interacting extreme-ultraviolet light by quantum-phase control. The quantum phase of excited states and its response to interactions can thus be extracted from line-shape analysis, with scientific applications in many branches of spectroscopy.

  10. 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

  11. 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.

  12. 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.

  13. Control of photodetachment spectra through laser dressing

    Science.gov (United States)

    Morrison, Nathan; Greene, Chris

    2013-05-01

    Photodetachment and photoionization spectra often display rich resonance structures. The properties of these spectra can be modified through dressing with intense laser fields, providing control over photon absorption and the emitted electron. We present a Floquet R-matrix method for calculating photodetachment cross sections in the presence of a dressing laser. The full wave functions in the Floquet formalism for bound and escaping electrons are found by solving the Schrödinger equation near the atomic core and applying analytic boundary conditions outside of the interaction region. These calculations are used to investigate the modification of existing resonances, such as modifying the shape, or q parameter, of Feshbach resonances. We also investigate the creation of new resonances in cases where high-lying bound states become autoionizing through the absorption of dressing laser photons. This work was supported by the DOE.

  14. 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.

  15. 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...

  16. 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)

  17. 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,...

  18. Long-range interactions between Rydberg atoms

    Science.gov (United States)

    Deiglmayr, Johannes

    2016-10-01

    We present an overview over theoretical models to describe adiabatic potential-energy curves, experimental excitation spectra, and electronic and nuclear dynamics in interacting Rydberg-atom pairs at large internuclear separations. The potential-energy curves and molecular wavefunctions are determined from the multipole expansion of the static Coulomb interaction which is evaluated numerically in a product basis of atomic orbitals. The convergence of this approach both in the truncation of the multipole expansion as well as in the size of the product basis is discussed, and the comparison of simulated excitation spectra is established as a useful criterium to test the convergence of the calculation. We finally discuss the dynamics of electronic and nuclear motions of pairs of Rydberg atoms, focusing on the stability of ultralong range Rydberg molecules with respect to autoionization.

  19. 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

  20. 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

  1. 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

  2. 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.

  3. Excited electronic structure of methylcyanoacetylene probed by VUV Fourier-transform absorption spectroscopy

    Science.gov (United States)

    Lamarre, N.; Gans, B.; Vieira Mendes, L. A.; Gronowski, M.; Guillemin, J.-C.; De Oliveira, N.; Douin, S.; Chevalier, M.; Crépin, C.; Kołos, R.; Boyé-Péronne, S.

    2016-10-01

    High resolution photoabsorption spectrum of gas-phase methylcyanoacetylene (CH3C3 N) has been recorded from 44 500 to 130 000 cm-1 at room temperature with a vacuum ultraviolet Fourier-transform spectrometer on the DESIRS synchrotron beamline (SOLEIL). The absolute photoabsorption cross section in this range is reported for the first time. Valence shell transitions and Rydberg series converging to the ground state X˜+2E of the cation as well as series converging to electronically excited states (A˜+A21 and C˜+) are observed and assigned. Time-dependent density-functional-theory calculations have been performed to support the assignment of the experimental spectrum in the low energy range. A tentative scaling of the previously measured CH3C3N+ ion yield by Lamarre et al. [17] is proposed, based on the comparison of the absorption data above the first ionization potential with the observed autoionization structures.

  4. 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

  5. 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.

  6. 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)

  7. 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

  8. 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)

  9. 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.

  10. 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

  11. 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

  12. 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

  13. 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.

  14. 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

  15. 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

  16. 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.)

  17. 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...

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. The effect of configuration complex on dielectronic recombination process in highly ionized plasmas

    Institute of Scientific and Technical Information of China (English)

    Jiao Rong-Zhen; Feng Chen-Xu

    2008-01-01

    This paper analyses the effect of configuration complex on dielectronic recombination (DR) process in highly ionized plasmas (Xe26+,Dy38+,W46+) by using the multiconfiguration relativistic Hartree-Fock method.Resonant and nonresonant radiative stabilizing transitions and decays to autoionizing levels followed by radiative cascades are included. Collisional transitions following electron capture are neglected. The remarkable difference between the isoelectronic trend of the rate coefficients for DR through 3d94/4l4l' 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 atomic number Z increases.

  3. 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.

  4. 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)

  5. 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.

  6. 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

  7. 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.

  8. 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...

  9. 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)

  10. 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.

  11. Resonances in photoabsorption: Predissociation line shapes in the 3pπD{sup 1}Π{sup +}{sub u} ← Χ{sup 1}Σ{sub g}{sup +} system in H{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Mezei, J. Zs. [Laboratoire Aimé-Cotton du CNRS Université Paris Sud, Bât. 505, F-91405 Orsay (France); Laboratoire Ondes et Milieux Complexes, UMR-6294 CNRS and Université du Havre, 25, rue Philippe Lebon, BP 540, 76058, Le Havre France (France); Schneider, I. F. [Laboratoire Ondes et Milieux Complexes, UMR-6294 CNRS and Université du Havre, 25, rue Philippe Lebon, BP 540, 76058, Le Havre France (France); Glass-Maujean, M. [Sorbonne Universités, UPMC Univ. Paris 06, UMR 8112, Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères, F-75005 Paris (France); Jungen, Ch., E-mail: christian.jungen@lac.u-psud.fr [Laboratoire Aimé-Cotton du CNRS Université Paris Sud, Bât. 505, F-91405 Orsay (France); Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom)

    2014-08-14

    The predissociation of the 3pπD{sup 1}Π{sub u}{sup +},v≥3,N=1, N = 2, and N = 3 levels of diatomic hydrogen is calculated by ab initio multichannel quantum defect theory combined with a R-matrix type approach that accounts for interfering predissociation and autoionization. The theory yields absorption line widths and shapes that are in good agreement with those observed in the high-resolution synchrotron vacuum-ultraviolet absorption spectra obtained by Dickenson et al. [J. Chem. Phys. 133, 144317 (2010)] at the DESIRS beamline of the SOLEIL synchrotron. The theory predicts further that many of the D state resonances with v ⩾ 6 exhibit a complex fine structure which cannot be modeled by the Fano profile formula and which has not yet been observed experimentally.

  12. 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

  13. 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.

  14. 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)

  15. Assessment of the Fluorescence and Auger Data Base used in Plasma Modeling

    CERN Document Server

    Gorczyca, T W; Korista, K T; Zatsarinny, O; Badnell, N R; Behar, E; Chen, M H; Savin, D W

    2003-01-01

    We have investigated the accuracy of the 1s-vacancy fluorescence data base of Kaastra & Mewe (1993, A&AS, 97, 443) resulting from the initial atomic physics calculations and the subsequent scaling along isoelectronic sequences. In particular, we have focused on the relatively simple Be-like and F-like 1s-vacancy sequences. We find that the earlier atomic physics calculations for the oscillator strengths and autoionization rates of singly-charged B II and Ne II are in sufficient agreement with our present calculations. However, the substantial charge dependence of these quantities along each isoelectronic sequence, the incorrect configuration averaging used for B II, and the neglect of spin-orbit effects (which become important at high-Z) all cast doubt on the reliability of the Kaastra & Mewe data for application to plasma modeling.

  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. 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

  18. Doubly excited helium. From strong correlation to chaos

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yuhai

    2006-03-15

    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 I{sub 15}, 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 I{sub 5} to I{sub 9} and I{sub 7}, 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 I{sub 4} were calculated employing the R-matrix method. The present theoretical results agree well with a recent experimental study of l-specific PCSs below I{sub 4} 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.)

  19. Relativistic atomic data for Rb-like tungsten

    Science.gov (United States)

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

    2016-05-01

    Accurate calculations of the atomic properties of Rb-like W37+ are needed for studying high energy density plasma as well as for magnetic fusion applications. In this work, we have calculated energy levels, radiative transition probabilities, and autoionization rates for [Ni] 4s2 4p6 nl , [Ni] 4s2 4p5 4l' nl (l' = d , f , n = 4-7), [Ni] 4 s 4p6 4l' nl ,(l' = d , f , n =4-7), [Ni] 4s2 4p5 5l' nl (n = 5-7), and [Ni] 4 s 4p6 46l' nl (n =6-7) states in Rb-like tungsten (W37+) using the relativistic many-body perturbation theory and the Hartree-Fock-relativistic method. Branching ratios and intensity factors were calculated for satellite lines, and dielectronic recombination rate coefficients were determined for the [Ni] 4s2 4p6 nl (n=4-7) singly excited states, as well as for the [Ni] 4s2 4p5 4 dnl , [Ni] 4s2 4p5 4 fnl , [Ni] 4 s 4p6 4 dnl , [Ni] 4 s 24p6 4 fnl , (n = 4-6), and [Ni] 4s2 4p5 5l' 5 l doubly excited nonautoionizing states. Contributions from the [Ni] 4 s 24p6 4 fnl (n = 6 - 7), [Ni] 4s2 4p5 5l' nl (n = 5 - 6), and [Ni] 4s2 4p5 6l' nl n = 6 - 7) doubly excited autoionizing states are evaluated numerically. Contributions from high-n states (n Cooperative Agreement DE-NA0001984. Work at LLNL was performed under auspices of the US DOE under Contract No. DE-AC52-07NA27344.

  20. 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

  1. 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

  2. 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

  3. 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.

  4. 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

  5. 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

  6. Time and frequency resolved spectra of high molecular Rydberg states by dynamical computations

    Science.gov (United States)

    Remacle, F.; Levine, R. D.

    1997-09-01

    The absorption spectrum of bound Rydberg states which can be detected by a delayed, pulsed field ionization is computed. The spectrum, measured for various delay times, provides information on the short and the longer time dynamics of high molecular Rydberg states. A quantitative dynamical theory, based on an effective Hamiltonian formalism is applied, illustrating the role of the Rydberg electron-core coupling and of an external electrical field in the delay-time dependent spectra. The sharpening of the spectra for longer delay times is reproduced by the dynamical computations. It is found that the overall intensity, as a function of the delay time before detection, is well described by a double exponential decay where the short lifetime is primarily a manifestation of the direct autoionization to the continuum, while the long lifetime is due to interseries coupling. Both lifetimes increase with the principal quantum number of the Rydberg states. The notion of trapped "reservoir states" is illustrated by the computational results, with special reference to a kinetic model analysis. The role of the initially optically accessed state(s) and of the depth of detection, in particular with regard to the intensity, is demonstrated. The effect of varying the strength of an external dc field in the time interval prior to the detection is illustrated by the dynamical computations, with respect to both the decay kinetics and the intensity of the spectrum.

  7. Precision measurements and test of molecular theory in highly-excited vibrational states of H$_2$ $(v=11)$

    CERN Document Server

    Trivikram, T Madhu; Wcisło, P; Ubachs, W; Salumbides, E J

    2016-01-01

    Accurate $EF{}^1\\Sigma^+_g-X{}^1\\Sigma^+_g$ transition energies in molecular hydrogen were determined for transitions originating from levels with highly-excited vibrational quantum number, $v=11$, in the ground electronic state. Doppler-free two-photon spectroscopy was applied on vibrationally excited H$_2^*$, produced via the photodissociation of H$_2$S, yielding transition frequencies with accuracies of $45$ MHz or $0.0015$ cm$^{-1}$. An important improvement is the enhanced detection efficiency by resonant excitation to autoionizing $7p\\pi$ electronic Rydberg states, resulting in narrow transitions due to reduced ac-Stark effects. Using known $EF$ level energies, the level energies of $X(v=11, J=1,3-5)$ states are derived with accuracies of typically 0.002 cm$^{-1}$. These experimental values are in excellent agreement with, and are more accurate than the results obtained from the most advanced ab initio molecular theory calculations including relativistic and QED contributions.

  8. 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.

  9. 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.

  10. Non-linear photoelectron effect contributes to the formation of negative matrix ions in UV-MALDI.

    Science.gov (United States)

    Alonso, E; Zenobi, R

    2016-07-20

    The mechanism of negative ion formation in matrix-assisted laser desorption/ionization (MALDI) is less well understood than that of positive ions: electron capture, disproportionation, and liberation of negatively charged sample molecules or clusters have been proposed to produce the initial anions in MALDI. Here, we propose that the non-linear photoelectric effect can explain the emission of electrons from the metallic target material. Moreover, electrons with sufficient kinetic energy (0-10 eV) could be responsible for the formation of initial negative ions. Gas-phase electron capture by neutral 2,5-dihydroxy benzoic acid (DHB) to yield M(-) is investigated on the basis of a coupled physical and chemical dynamics (CPCD) theory from the literature. A three-layer energy mass balance model is utilized to calculate the surface temperature of the matrix, which is used to determine the translational temperature, the number of desorbed matrix molecules per unit area, and the ion velocity. Calculations of dissociative attachment and autoionization rates of DHB are presented. It was found that both processes contribute significantly to the formation of [M - H](-) and [M - H2](-), although the predicted yield in the fluence range of 5-100 mJ cm(-2) is low, certainly less than that for positive ions M(+). This work represents the first proposal for a comprehensive theoretical description of negative ion formation in UV-MALDI.

  11. 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.

  12. 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

  13. High efficiency resonance ionization of palladium with Ti:sapphire lasers

    Science.gov (United States)

    Kron, T.; Liu, Y.; Richter, S.; Schneider, F.; Wendt, K.

    2016-09-01

    This work presents the development and testing of highly efficient excitation schemes for resonance ionization of palladium. To achieve the highest ionization efficiencies, a high-power, high repetition rate Ti:sapphire laser system was used and 2-step, 3-step and 4-step schemes were investigated and compared. Starting from different excited steps, the frequencies of the final ionization steps were tuned across the full accessible spectral range of the laser system, revealing several autoionizing Rydberg series, which converge towards the energetically higher lying state 4{{{d}}}9{}2{{{D}}}3/2 of the Pd+ ion ground state configuration. Through proper choice of these excitation steps, we developed a highly efficient, fully resonant 3-step excitation scheme, which lead to overall efficiencies of 54.3(1.4) % and 59.7(2.1) %, measured at two independent mass separator setups. To our knowledge, these are presently the highest efficiency values ever achieved with a resonance ionization laser ion source.

  14. 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.

  15. 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.

  16. Hematite(001)-liquid water interface from hybrid density functional-based molecular dynamics

    Science.gov (United States)

    Falk von Rudorff, Guido; Jakobsen, Rasmus; Rosso, Kevin M.; Blumberger, Jochen

    2016-10-01

    The atom-scale characterisation of interfaces between transition metal oxides and liquid water is fundamental to our mechanistic understanding of diverse phenomena ranging from crystal growth to biogeochemical transformations to solar fuel production. Here we report on the results of large-scale hybrid density functional theory-based molecular dynamics simulations for the hematite(001)-liquid water interface. A specific focus is placed on understanding how different terminations of the same surface influence surface solvation. We find that the two dominant terminations for the hematite(001) surface exhibit strong differences both in terms of the active species formed on the surface and the strength of surface solvation. According to present simulations, we find that charged oxyanions (-O-) and doubly protonated oxygens (-OH2+ ) can be formed on the iron terminated layer via autoionization of neutral -OH groups. No such charged species are found for the oxygen terminated surface. In addition, the missing iron sublayer in the iron terminated surface strongly influences the solvation structure, which becomes less well ordered in the vicinity of the interface. These pronounced differences are likely to affect the reactivity of the two surface terminations, and in particular the energetics of excess charge carriers at the surface.

  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. Exotic x-ray emission from dense plasmas

    Science.gov (United States)

    Rosmej, F. B.; Dachicourt, R.; Deschaud, B.; Khaghani, D.; Dozières, M.; Šmíd, M.; Renner, O.

    2015-11-01

    Exotic x-ray emission from dense matter is identified as the complex high intensity satellite emission from autoionizing states of highly charged ions. Among a vast amount of possible transitions, double K-hole hollow ion (HI) x-ray emission K0L X → K1L X-1 + hν hollow is of exceptional interest due to its advanced diagnostic potential for matter under extreme conditions where opacity and radiation fields play important roles. Transient ab initio simulations identify intense short pulse radiation fields (e.g., those emitted by x-ray free electron lasers) as possible driving mechanisms of HI x-ray emission via two distinct channels: first, successive photoionization of K-shell electrons, second, photoionization followed by resonant photoexciation among various ionic charge states that are simultaneously present in high density matter. We demonstrated that charge exchange of intermixing inhomogenous plasmas as well as collisions driven by suprathermal electrons are possible mechanisms to populate HIs to observable levels in dense plasmas, particularly in high current Z-pinch plasmas and high intensity field-ionized laser produced plasmas. Although the HI x-ray transitions were repeatedly identified in many other cases of dense optical laser produced plasmas on the basis of atomic structure calculations, their origin is far from being understood and remains one of the last holy grails of high intensity laser-matter interaction.

  19. 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...

  20. 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.

  1. 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.

  2. Communication: Vacuum ultraviolet laser photodissociation studies of small molecules by the vacuum ultraviolet laser photoionization time-sliced velocity-mapped ion imaging method

    Science.gov (United States)

    Pan, Yang; Gao, Hong; Yang, Lei; Zhou, Jingang; Ng, C. Y.; Jackson, William M.

    2011-08-01

    We demonstrate that the vacuum ultraviolet (VUV) photodissociation dynamics of N2 and CO2 can be studied using VUV photoionization with time-sliced velocity-mapped ion imaging (VUV-PI-VMI) detection. The VUV laser light is produced by resonant sum frequency mixing in Kr. N2 is used to show that when the photon energy of the VUV laser is above the ionization energy of an allowed transition of one of the product atoms it can be detected and characterized as the wavelength is varied. In this case a β parameter = 0.57 for the N(2D°) was measured after exciting N2(o1Πu, v' = 2, J' = 2) ← N2(X1Σg+, v″ = 0, J″ = 1). Studies with CO2 show that when there is no allowed transition, an autoionization resonance can be used for the detection of a product atom. In this case it is shown for the first time that the O(1D) atom is produced with CO(1Σ+) at 92.21 nm. These results indicate that the VUV laser photodissociation combined with the VUV-PI-VMI detection is a viable method for studying the one-photon photodissociation from the ground state of simple molecules in the extreme ultraviolet and VUV spectral regions.

  3. 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

  4. 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...

  5. New insight into the Auger decay process in O{sub 2}: The coincidence perspective

    Energy Technology Data Exchange (ETDEWEB)

    Arion, Tiberiu, E-mail: tiberiu.arion@cfel.de [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstr. 2, 85748 Garching (Germany); Institut fuer Experimentalphysik, Universitaet Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); Puettner, Ralph [Institut fuer Experimentalphysik, Freie Universitaet Berlin, Arnimallee 14, 14195 Berlin (Germany); Lupulescu, Cosmin [Technische Universitaet Berlin, Institut fuer Optik und atomare Physik, Hardenbergstr. 36, 10623 Berlin (Germany); Ovsyannikov, Ruslan [Helmholtz-Zentrum Berlin, Albert-Einstein-Str. 15, 12489 Berlin (Germany); Foerstel, Marko [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstr. 2, 85748 Garching (Germany); Oehrwall, Gunnar [MAX-lab, Lund University, P.O. Box 118, SE-22100 Lund (Sweden); Lindblad, Andreas [Uppsala University, Department of Physics and Astronomy, Box 516, SE-751 20 Uppsala (Sweden); Ueda, Kiyoshi [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Svensson, Svante [Uppsala University, Department of Physics and Astronomy, Box 516, SE-751 20 Uppsala (Sweden); Bradshaw, Alex M. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstr. 2, 85748 Garching (Germany); Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin (Germany); Eberhardt, Wolfgang [Technische Universitaet Berlin, Institut fuer Optik und atomare Physik, Hardenbergstr. 36, 10623 Berlin (Germany); Center for Free-Electron Laser Science, Notkestrasse 85, 22607 Hamburg (Germany); and others

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer We developed a new experimental set-up for e,e-coincidence experiments. Black-Right-Pointing-Pointer New information on the potential curves of the final states in O{sub 2} has been extracted. Black-Right-Pointing-Pointer We observed new features, assigned to autoionization of neutral doubly excited states. -- Abstract: Photoelectron-Auger electron coincidence spectroscopy is a powerful tool for the investigation of Auger decay processes with different core-ionized intermediate states. In this paper we describe an investigation into the Auger decay of the O{sub 2} molecule, with the purpose of bringing new insight into the dynamics of the core hole decay mechanism. Using a novel experimental approach to measuring such coincidence spectra we report the highest resolution Auger spectrum of O{sub 2} recorded hitherto. In our approach, we have combined the advantages of these coincidence spectra with the high resolution and excellent signal-to-noise ratios of non-coincident Auger spectra and a state-of-the-art fit analysis. In this way we have derived information about the potential energy curves of the final states W {sup 3}{Delta}{sub u}, B {sup 3}{Pi}{sub g}, and B Prime {sup 3}{Sigma}{sub u}{sup -} and concluded that the corresponding Auger transitions are formed to a large part by strongly overlapping vibrational progressions. The present findings are compared to earlier results reported in the literature confirming some theoretical predictions.

  6. 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

  7. 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...

  8. Resonance poles and threshold energies for hadron physical problems by a model-independent universal algorithm

    CERN Document Server

    Tripolt, Ralf-Arno; Wambach, Jochen; Moiseyev, Nimrod

    2016-01-01

    We show how complex resonance poles and threshold energies for systems in hadron physics can be accurately obtained by using a method based on the Pad\\'{e}-approximant which was recently developed for the calculation of resonance poles for atomic and molecular auto-ionization systems. The main advantage of this method is the ability to calculate the resonance poles and threshold energies from \\emph{real} spectral data. In order to demonstrate the capabilities of this method we apply it here to an analytical model as well as to experimental data for the squared modulus of the vector pion form factor, the S0 partial wave amplitude for $\\pi\\pi$ scattering and the cross section ratio $R(s)$ for $e^+e^-$ collisions. The extracted values for the resonance poles of the $\\rho(770)$ and the $f_0(500)$ or $\\sigma$ meson are in very good agreement with the literature. When the data are noisy the prediction of decay thresholds proves to be less accurate but feasible.

  9. 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.

  10. 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

  11. 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)

  12. 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.

  13. 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).

  14. 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

  15. Gd激光等离子体的双电子复合过程研究%Dielectronic recombination process in laser-produced Gd Plasmas

    Institute of Scientific and Technical Information of China (English)

    焦荣珍; 郭爱鹏; 张茹

    2006-01-01

    Dielectronic recombination (DR) coefficients for the ground-state ion of Ni-like Gd have been calculated through Cu-like 3d9nln′f(n,n′=4,5,6) inner-shell excited configurations using the spin-orbit-split array(SOSA) model. 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 DR rates, and may even dominate the process at low electron temperature . The trend of the DR rate coefficients and the ratio of dielectronic satellite lines intensities with the change of the electron temperature are discussed.%在自旋-轨道劈裂阵模型下,通过类铜的内壳层激发组态计算了类镍Gd的双电子复合速率系数,其中考虑了共振和非共振辐射平衡跃迁对自电离能级的影响,而忽略了因碰撞跃迁引起的电子俘获,非共振辐射平衡跃迁在低电子温度条件下主要影响双电子复合过程;本文讨论了双电子复合系数及双电子伴线强度比随电子温度的变化.

  16. 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.

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. 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)

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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...

  9. Photoionisation of Cl$^+$ from the $3s^23p^4\\;^3P_{2,1,0}$ and the$3s^23p^4\\;^1D_2, ^1S_0$ states in the energy range 19 - 28 eV

    CERN Document Server

    McLaughlin, Brendan M

    2016-01-01

    Absolute photoionisation cross sections for the Cl$^+$ ion in its ground and the metastable states; $3s^2 3p^4\\; ^3P_{2,1,0}$, and $3s^2 3p^4\\; ^1D_2,\\; ^1S_0$, were measured recently at the Advanced Light Source ALS) at Lawrence Berkeley National Laboratory using the merged beams photon-ion technique at an photon energy resolution of 15 meV in the energy range 19 -- 28 eV. These measurements are compared with large-scale Dirac Coulomb {\\it R}-matrix calculations in the same energy range. Photoionisation of this sulphur-like chlorine ion is characterized by multiple Rydberg series of autoionizing resonances superimposed on a direct photoionisation continuum. A wealth of resonance features observed in the experimental spectra are spectroscopically assigned and their resonance parameters tabulated and compared with the recent measurements. Metastable fractions in the parent ion beam are determined from the present study. Theoretical resonance energies and quantum defects of the prominent Rydberg series $3s^2 3p...

  10. 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.

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

    Science.gov (United States)

    McLaughlin, Brendan M.

    2016-10-01

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

  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. 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)

  14. a New Spectroscopic Window on Hydroxyl Radicals and Their Association Reactions of Significance in the Atmosphere

    Science.gov (United States)

    Lester, Marsha I.

    2012-06-01

    The weakly bound hydrogen trioxy radical (HOOO), produced in the association reaction of the hydroxyl radical (OH) with molecular oxygen (O_2), has been postulated to play an important role in atmospherically relevant reactions. Experimental studies in this laboratory have utilized infrared action spectroscopy to probe the structure, vibrational frequencies, and stability of this weakly bound species. Recent experimental and theoretical results on HOOO will be presented, and used in assessing its significance in the atmosphere. Most studies of the hydroxyl radical and its association products utilize laser-induced fluorescence on the well-characterized OH A^2Σ^+ - X^2π band system for detection. This laboratory has recently demonstrated a new photoionization scheme combining initial UV excitation on the A^2Σ^+ - X^2π band system with subsequent fixed-frequency VUV ionization via autoionizing Rydberg states. The photoionization mechanism as well as the applicability of this quantum state-selective photoionization scheme will be presented. footnote C. Murray, E. L. Derro, T. D. Sechler, and M. I. Lester, Acc. Chem. Res. 42, 419-427 (2009). J. M. Beames, M. I. Lester, C. Murray, M. E. Varner, and J. F. Stanton, J. Chem. Phys. 134, 044304 (2011). J. M. Beames, M. I. Lester, C. Murray, M. E. Varner, and J. F. Stanton, J. Chem. Phys. 134, 044304 (2011). J. M. Beames, F. Liu, M. I. Lester, and C. Murray, J. Chem. Phys. 134, 241102 (2011).

  15. 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.

  16. Dielectronic recombination rate coefficient for Cu-like Au50+ ion

    Institute of Scientific and Technical Information of China (English)

    Yang Tian-Li; Jiang Gang; Zhu Zheng-He

    2004-01-01

    The rate coefficients αDR of dielectronic recombination (DR) for Cu-like Au50+ ion collided with the incident free electron are calculated based on the quasi-relativistic multi-configuration Hartree-Fock theory. The results clearly show that the oDR of all recombination channels exhibits resonance characters with electron temperature. At lower temperatures, the recombination for electrons caused by 4s excitation is dominant through outer electron radiative transitions among the intermediate doubly excited autoionizing levels, in which the most components come from 3d105pns states,whereas with increasing electron temperature, DR caused by 3d excitation turns out to be dominant, and the contribution from the 3d94s4fnf state to the total rate coefficient of electron 3d is the largest with αDR = 1.15 × 10-11 cm3.s-1at an electron temperature of Te=0.35 keV. Under this condition, there exists a strong competition between the two types of recombination channels.

  17. 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

  18. Resonance Ionization Spectroscopy of Europium: The First Application of the PISA at ISOLDE-RILIS

    CERN Document Server

    AUTHOR|(CDS)2099873; Marsh, Bruce Alan

    The following work has been carried out at the radioactive ion beam facility ISOLDE at CERN. A compact atomic beam unit named PISA (Photo Ionization Spectroscopy Apparatus) has been implemented as a recent addition to the laboratory of the Resonance Ionization Laser Ion Source (RILIS). The scope of this thesis work was to demonstrate different applications of the PISA, using the existing and highly developed laser setup of the RILIS installation. In a demonstration of the suitability of PISA for ionization scheme development, a new ionization scheme for Europium has been developed. This resulted in the observation of several new autoionizing states and Rydberg series. Through the analysis of the observed Rydberg resonances a refined value of $45734.33(3)(3)$ cm$^{-1}$ for the ionization potential of the europium atom has been determined. In addition this thesis reports on the feasibility of the use of the PISA as a RILIS performance monitoring device during laser ion source operations. Finally the present wor...

  19. 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.

  20. 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.

  1. 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.

  2. 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...

  3. Photoionization of hydrogen in atmospheres of magnetic neutron stars

    CERN Document Server

    Potekhin, A Yu

    1997-01-01

    The strong magnetic fields (B ~ 10^{12} - 10^{13} G) characteristic of neutron stars make all the properties of an atom strongly dependent on the transverse component K_\\perp of its generalized momentum. In particular, the photoionization process is modified substantially: (i) threshold energies are decreased as compared with those for an atom at rest, (ii) cross section values are changed significantly, and (iii) selection rules valid for atoms at rest are violated by the motion so that new photoionization channels become allowed. To calculate the photoionization cross sections, we, for the first time, employ exact numerical treatment of both initial and final atomic states. This enables us to take into account the quasi-bound (autoionizing) atomic states as well as coupling of different ionization channels. We extend the previous consideration, restricted to the so-called centered states corresponding to relatively small values of K_\\perp, to arbitrary states of atomic motion. We fold the cross sections wit...

  4. 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 ...

  5. 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...

  6. 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)

  7. 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

  8. Probing charge transfer and hot carrier dynamics in organic solar cells with terahertz spectroscopy

    Science.gov (United States)

    Cunningham, Paul D.; Lane, Paul A.; Melinger, Joseph S.; Esenturk, Okan; Heilweil, Edwin J.

    2016-04-01

    Time-resolved terahertz spectroscopy (TRTS) was used to explore charge generation, transfer, and the role of hot carriers in organic solar cell materials. Two model molecular photovoltaic systems were investigated: with zinc phthalocyanine (ZnPc) or alpha-sexathiophene (α-6T) as the electron donors and buckminsterfullerene (C60) as the electron acceptor. TRTS provides charge carrier conductivity dynamics comprised of changes in both population and mobility. By using time-resolved optical spectroscopy in conjunction with TRTS, these two contributions can be disentangled. The sub-picosecond photo-induced conductivity decay dynamics of C60 were revealed to be caused by auto-ionization: the intrinsic process by which charge is generated in molecular solids. In donor-acceptor blends, the long-lived photo-induced conductivity is used for weight fraction optimization of the constituents. In nanoscale multilayer films, the photo-induced conductivity identifies optimal layer thicknesses. In films of ZnPc/C60, electron transfer from ZnPc yields hot charges that localize and become less mobile as they thermalize. Excitation of high-lying Franck Condon states in C60 followed by hole-transfer to ZnPc similarly produces hot charge carriers that self-localize; charge transfer clearly precedes carrier cooling. This picture is contrasted to charge transfer in α-6T/C60, where hole transfer takes place from a thermalized state and produces equilibrium carriers that do not show characteristic signs of cooling and self-localization. These results illustrate the value of terahertz spectroscopic methods for probing charge transfer reactions.

  9. 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.

  10. 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)

  11. 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)

  12. 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

  13. 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}

  14. 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.

  15. 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)

  16. 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.)

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

    Science.gov (United States)

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

    2013-05-01

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

  18. 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.

  19. Dielectronic recombination process in laser-produced Xe plasmas%氙激光等离子体的双电子复合过程研究

    Institute of Scientific and Technical Information of China (English)

    焦荣珍; 冯晨旭; 张茹

    2007-01-01

    Dielectronic recombination(DR)coefficients for the ground-state ion of Ni-like Xe have been calculated through Cu-like 3d9nln'f(n,n'=4,5,6)inner-shell excited configurations using the spin-orbit-split array(SOSA)model.Resonant and nonresonant radiative stabilizing transitions and decays to autoionizing levels followed by radiative cacsades are included.Collisional transitions following electron capture are neglected.Nonresonant stabilizing transitions are found to enhance DR rates,and may even dominate the process at low electron temperature.The trend of the DR rate coefficients and the ratio of dielectronic satellite lines intensities with the change of the electron temperature are discussed.%在自旋-轨道劈裂阵模型下,通过类铜的内壳层激发组态计算了类镍氙的双电子复合速率系数,其中考虑了共振和非共振辐射平衡跃迁对自电离能级的影响,而忽略了因碰撞跃迁引起的电子俘获,非共振辐射平衡跃迁在低电子温度条件下主要影响双电子复合过程;本文讨论了双电子复合系数及双电子伴线强度比随电子温度的变化.

  20. 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)

  1. 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.

  2. Two-electron transfer and ionization mechanism in 80-keV/u Ne8 + on He collisions

    Science.gov (United States)

    Zhang, R. T.; Feng, W. T.; Zhu, X. L.; Zhang, S. F.; Guo, D. L.; Gao, Y.; Qian, D. B.; Xu, S.; Yan, S. C.; Zhang, P.; Huang, Z. K.; Wang, H. B.; Hai, B.; Zhao, D. M.; Ma, X.

    2016-03-01

    Autoionization decay from doubly excited states of Ne6 +[1 s23 l n l (n =3 ,4 ,5 )] (symmetric configurations) as well as the Coster-Kronig transition from doubly excited states of Ne6 +[1 s22 p n l (n ⩾7 ) ] (asymmetric configurations) are observed in the transfer ionization reaction channel of 80 keV/u Ne8 +-He collisions. It has been predicted that the formation of symmetric configurations results from uncorrelated double-electron capture processes [Z. Chen and C. D. Lin, Phys. Rev. A 48, 1298 (1993), 10.1103/PhysRevA.48.1298], and the formation of asymmetric configurations probably results from correlated double-electron capture caused by the dynamical electron-correlation effects which are attributed to small internuclear distances. However, previous experimental measurements were not able to obtain information about the dependence on internuclear distance which can be reflected in the transversal recoil-ion momentum. In this work, we measure the recoil-ion momentum in coincidence with the ejected electron velocity and find that the observed transverse recoil-ion momentum is smaller for the formation of symmetric Ne6 +[1 s23 l n l (n =3 ,4 ,5 ) ] states than the formation of asymmetric Ne6 +[1 s22 p n l (n ⩾7 ) ] states. Since large momentum transfer occurs for small internuclear distances (strong electron-electron interactions) and small momentum transfer occurs for large internuclear distances (weak electron-electron interactions), the results indicate that dynamical electron correlation is important for the formation of the asymmetric states.

  3. Ionization photophysics and spectroscopy of cyanoacetylene

    Energy Technology Data Exchange (ETDEWEB)

    Leach, Sydney; Champion, Norbert [LERMA UMR CNRS 8112, Observatoire de Paris-Meudon, 5 place Jules-Jansen, 92195 Meudon (France); Garcia, Gustavo A.; Fray, Nicolas; Gaie-Levrel, François [Synchrotron SOLEIL, L’Orme des Merisiers, St. Aubin, B.P. 48, 91192, Gif-sur-Yvette Cedex (France); Mahjoub, Ahmed; Bénilan, Yves; Gazeau, Marie-Claire; Schwell, Martin [LISA UMR CNRS 7583, Université Paris Est Créteil and Université Paris Diderot, Institut Pierre Simon Laplace, 61 Avenue du Général de Gaulle, 94010 Créteil (France)

    2014-05-07

    Photoionization of cyanoacetylene was studied using synchrotron radiation over the non-dissociative ionization excitation range 11–15.6 eV, with photoelectron-photoion coincidence techniques. The absolute ionization cross-section and spectroscopic aspects of the parent ion were recorded. The adiabatic ionization energy of cyanoacetylene was measured as 11.573 ± 0.010 eV. A detailed analysis of photoelectron spectra of HC{sub 3}N involves new aspects and new assignments of the vibrational components to excitation of the A{sup 2}Σ{sup +} and B{sup 2}Π states of the cation. Some of the structured autoionization features observed in the 11.94 to 15.5 eV region of the total ion yield (TIY) spectrum were assigned to two Rydberg series converging to the B{sup 2}Π state of HC{sub 3}N{sup +}. A number of the measured TIY features are suggested to be vibrational components of Rydberg series converging to the C{sup 2}Σ{sup +} state of HC{sub 3}N{sup +} at ≈17.6 eV and others to valence shell transitions of cyanoacetylene in the 11.6–15 eV region. The results of quantum chemical calculations of the cation electronic state geometries, vibrational frequencies and energies, as well as of the C–H dissociation potential energy profiles of the ground and electronic excited states of the ion, are compared with experimental observations. Ionization quantum yields are evaluated and discussed and the problem of adequate calibration of photoionization cross-sections is raised.

  4. 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

  5. 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.

  6. 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)

  7. Double Electron Processes in Low Energy Isotope Bare Ions 13C6+ with Helium Collisions

    Institute of Scientific and Technical Information of China (English)

    YU De-Yang; SHAO Jian-Xiong; DING Bao-Wei; YANG Zhi-Hu; CHEN Xi-Meng; CAI Xiao-Hong; LU Rong-Chun; SHAO Cao-Jie; LU Jun; RUAN Fang-Fang; ZHANG Hong-Qiang; CUI Ying; XU Xu

    2005-01-01

    @@ The isotopic bare ion 13C6+ was employed to collide with helium at 4.15-11.08keV/u. The relative partial cross sections were measured by position-sensitive and time-of-flight coincident techniques. It is shown that the direct-ionization (DI) process can be completely ignored in this region, the transfer ionization (TI) process is the most important double-electron channel, and the probability of the pure double-electron capture (DC) process is quite small. The cross-section ratio of the total double-electron (DE) process (i.e. DC+TI) to the single-electron capture (SC) process is experimentally determined to be approximately a constant of 0.09 ± 0.03 in this region,and this value is obviously smaller than the predictions of the classical over-barrier models and the semi-empirical scaling laws. It is found that the cross-section ratio of pure DC to DE decreases obviously as the projectile velocity increases. Because the pure DC process only comes from the radiation de-excitation following the DC process and are competed by the TI process (comes from the auto-ionization following the DC process), this implies that the population of the two captured electrons depends distinctly on the collision velocity. Comparison with works on Ar16+-He by Wu et al. [Phys. Rev. A 48 (1993) 3617] reveals that the strong projectile-dependent character of the pure DC process exists.

  8. 4d → 4f resonance in photoabsorption of cerium ion Ce3+ and endohedral cerium in fullerene complex {\\rm{Ce}}@{{{\\rm{C}}}_{82}}^{+}

    Science.gov (United States)

    Schrange-Kashenock, G.

    2016-09-01

    cage decreases the autoionizing giant 4d\\to 4f resonance lifetime for endohedral cerium in {{Ce}}@{{{{C}}}82}+ due to the opening of additional decay channels involving electrons of the fullerene shell, which cannot be accounted as a static potential. From consideration of the two-step model, it is clear that these processes are important. However, they lead only to broadening of the resonance. The dramatic reduction in the integrated oscillator strength in the cerium 4d resonance region can only occur when additional processes besides photoionization come into play.

  9. Photoionization of iodine atoms: Angular distributions and relative partial photoionization cross-sections in the energy region 11.0-23.0 eV

    Science.gov (United States)

    Eypper, Marie; Innocenti, Fabrizio; Morris, Alan; Dyke, John M.; Stranges, Stefano; West, John B.; King, George C.

    2010-08-01

    states, relativistic effects including spin-orbit interaction, and autoionization via resonant Rydberg states.

  10. 4d → 4f resonance in photoabsorption of cerium ion Ce3+ and endohedral cerium in fullerene complex {\\rm{Ce}}@{{{\\rm{C}}}_{82}}^{+}

    Science.gov (United States)

    Schrange-Kashenock, G.

    2016-09-01

    fullerene cage decreases the autoionizing giant 4d\\to 4f resonance lifetime for endohedral cerium in {{Ce}}@{{{{C}}}82}+ due to the opening of additional decay channels involving electrons of the fullerene shell, which cannot be accounted as a static potential. From consideration of the two-step model, it is clear that these processes are important. However, they lead only to broadening of the resonance. The dramatic reduction in the integrated oscillator strength in the cerium 4d resonance region can only occur when additional processes besides photoionization come into play.

  11. 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

  12. 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(tilde X{}^1Σ ^ + ; v) + O(3P0,1,2) in VUV photodissociation of CO2

    Science.gov (United States)

    Lu, Zhou; Chang, Yih Chung; Gao, Hong; Benitez, Yanice; Song, Yu; Ng, C. Y.; Jackson, W. M.

    2014-06-01

    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(tilde X{}^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(tilde X{}^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(tilde X{}^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(tilde X{}^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.

  13. Communication: direct measurements of nascent O((3)P0,1,2) fine-structure distributions and branching ratios of correlated spin-orbit resolved product channels CO(ã(3)Π; v) + O((3)P0,1,2) and CO(X̃(1)Σ(+); v) + O((3)P0,1,2) in VUV photodissociation of CO2.

    Science.gov (United States)

    Lu, Zhou; Chang, Yih Chung; Gao, Hong; Benitez, Yanice; Song, Yu; Ng, C Y; Jackson, W M

    2014-06-21

    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(ã(3)Π; v) + O((3)P0,1,2) and CO(X̃(1)Σ(+); v) + O((3)P0,1,2), formed by VUV photoexcitation of CO2 to the 4s(10 (1)) Rydberg state at 97,955.7 cm(-1). The total kinetic energy release (TKER) spectra obtained from the O(+) VMI-PI images of O((3)P0,1,2) reveal the formation of correlated CO(ã(3)Π; 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(ã(3)Π; v = 0-2) + O((3)P0,1,2) channel has no potential energy barrier. The TKER spectra for the spin-forbidden CO(X̃(1)Σ(+); v) + O((3)P0,1,2) channel were found to exhibit broad profiles, indicative of the formation of a broad range of rovibrational states of CO(X̃(1)Σ(+)) with significant vibrational populations for v = 18-26. While the VMI-PI images for the CO(ã(3)Π; v = 0-2) + O((3)P0,1,2) channel are anisotropic, indicating that the predissociation of CO2 4s(10 (1)) occurs via a near linear configuration in a time scale shorter than the rotational period, the angular distributions for the CO(X̃(1)Σ(+); v) + O((3)P0,1,2) channel are close to isotropic, revealing a slower predissociation process, which possibly occurs on a triplet surface via an intersystem crossing mechanism. PMID:24952514

  14. Communication: Direct measurements of nascent O({sup 3}P{sub 0,1,2}) fine-structure distributions and branching ratios of correlated spin-orbit resolved product channels CO(ã{sup 3}Π; v) + O({sup 3}P{sub 0,1,2}) and CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}) in VUV photodissociation of CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Zhou; Chang, Yih Chung; Gao, Hong; Benitez, Yanice; Song, Yu; Ng, C. Y., E-mail: cyng@chem.ucdavis.edu, E-mail: wmjackson@ucdavis.edu; Jackson, W. M., E-mail: cyng@chem.ucdavis.edu, E-mail: wmjackson@ucdavis.edu [Department of Chemistry, University of California, Davis, Davis, California 95616 (United States)

    2014-06-21

    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(ã{sup 3}Π; v) + O({sup 3}P{sub 0,1,2}) and CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}), formed by VUV photoexcitation of CO{sub 2} to the 4s(1{sub 0}{sup 1}) Rydberg state at 97,955.7 cm{sup −1}. The total kinetic energy release (TKER) spectra obtained from the O{sup +} VMI-PI images of O({sup 3}P{sub 0,1,2}) reveal the formation of correlated CO(ã{sup 3}Π; v = 0–2) with well-resolved v = 0–2 vibrational bands. This observation shows that the dissociation of CO{sub 2} to form the spin-allowed CO(ã{sup 3}Π; v = 0–2) + O({sup 3}P{sub 0,1,2}) channel has no potential energy barrier. The TKER spectra for the spin-forbidden CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}) channel were found to exhibit broad profiles, indicative of the formation of a broad range of rovibrational states of CO(Χ{sup ~1}Σ{sup +})  with significant vibrational populations for v = 18–26. While the VMI-PI images for the CO(ã{sup 3}Π; v = 0–2) + O({sup 3}P{sub 0,1,2}) channel are anisotropic, indicating that the predissociation of CO{sub 2} 4s(1{sub 0}{sup 1}) occurs via a near linear configuration in a time scale shorter than the rotational period, the angular distributions for the CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}) channel are close to isotropic, revealing a slower predissociation process, which possibly occurs on a triplet surface via an intersystem crossing mechanism.

  15. 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.

  16. 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

  17. 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.

  18. 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

  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. 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

  1. 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

  2. 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