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Sample records for 1s ionization energies

  1. Energy partitioning in {sup 1}S-wave electron-impact ionization of atomic hydrogen

    SciTech Connect

    Shakeshaft, Robin

    2010-03-15

    Results of calculations of the integrated cross section and the energy distribution for ionization of ground-state hydrogen by {sup 1}S-wave electron impact are presented. The breakup amplitude is expressed as a volume integral that contains an approximate final-state wave function which accounts for postcollision dynamic screening. The error in this wave function is accounted for by the response function, which is represented on a real discrete (Sturmian) basis, with its physical branch specified by the arrow of time. It is found that the energy distribution is primarily convex for impact energies from about 2 to 10 eV above threshold, and primarily flat from about 10 to 20 eV above threshold. The shape of the energy distribution appears to reflect both the competition between escape and recapture, and the substantial postcollision exchange of energy between the electrons. A rough, nonclassical criterion for predicting the curvature of the energy distribution is derived.

  2. Ionization energies and term energies of the ground states 1s22s of lithium-like systems

    NASA Astrophysics Data System (ADS)

    Li, Jin-Ying; Wang, Zhi-Wen

    2014-01-01

    We extend the Hamiltonian method of the full-core plus correlation (FCPC) by minimizing the expectation value to calculate the non-relativistic energies and the wave functions of 1s22s states for the lithium-like systems from Z = 41 to 50. The mass-polarization and the relativistic corrections including the kinetic-energy correction, the Darwin term, the electron—electron contact term, and the orbit—orbit interaction are calculated perturbatively as first-order correction. The contribution from quantum electrodynamic (QED) is also explored by using the effective nuclear charge formula. The ionization potential and term energies of the ground states 1s22s are derived and compared with other theoretical calculation results. It is shown that the FCPC methods are also effective for theoretical calculation of the ionic structure for high nuclear ion of lithium-like systems.

  3. Fine structure and ionization energy of the 1s2s2p 4P state of the helium negative ion He-.

    PubMed

    Wang, Liming; Li, Chun; Yan, Zong-Chao; Drake, G W F

    2014-12-31

    The fine structure and ionization energy of the 1s2s2p (4)P state of the helium negative ion He(-) are calculated in Hylleraas coordinates, including relativistic and QED corrections up to O(α(4)mc(2)), O((μ/M)α(4)mc(2)), O(α(5)mc(2)), and O((μ/M)α(5)mc(2)). Higher order corrections are estimated for the ionization energy. A comparison is made with other calculations and experiments. We find that the present results for the fine structure splittings agree with experiment very well. However, the calculated ionization energy deviates from the experimental result by about 1 standard deviation. The estimated theoretical uncertainty in the ionization energy is much less than the experimental accuracy.

  4. Ionization, excitation, and electron transfer in MeV-energy collisions between light nuclei and C{sup 5+}(1s) ions studied with a Sturmian basis

    SciTech Connect

    Winter, Thomas G.

    2004-04-01

    Cross sections have been determined for direct excitation, ionization, and electron transfer in collisions between H, He, Li, and Be nuclei and C{sup 5+}(1s) target ions at nuclear energies 1-24 MeV/nucleon, extending earlier work [Phys. Rev. A 56, 2903 (1997)] to higher energies. Coupled Sturmian pseudostates of principal quantum number at least up to 30 have been included for each angular momentum s, p, d, and f centered on the C nucleus, as well as a 1s state centered on the projectile. Detailed basis-convergence studies have been carried out. Cross sections have been compared with the corresponding Born results, and scaling rules have also been examined.

  5. Excitation and Ionization in H(1s)-H(1s) Collisions

    SciTech Connect

    Riley, Merle E.; Ritchie, A. Burke

    1999-07-15

    Hydrogen atom - hydrogen atom scattering is a prototype for many of the fundamental principles of atomic collisions. In this work we present an approximation to the H+H system for scattering in the intermediate energy regime of 1 to 100 keV. The approximation ignores electron exchange and two-electron excitation by assuming that one of the atoms is frozen in the 1s state. We allow for the evolution of the active electron by numerically solving the 3D Schroedinger equation. The results capture many features of the problem and are in harmony with recent theoretical studies. Excitation and ionization cross sections are computed and compared to other theory and experiment. New insight into the mechanism of excitation and ionization is inferred from the solutions.

  6. Ionization Energies of Lanthanides

    ERIC Educational Resources Information Center

    Lang, Peter F.; Smith, Barry C.

    2010-01-01

    This article describes how data are used to analyze the pattern of ionization energies of the lanthanide elements. Different observed pathways of ionization between different ground states are discussed, and the effects of pairing, exchange, and orbital interactions on ionization energies of the lanthanides are evaluated. When all the above…

  7. Ionization Energies of Lanthanides

    ERIC Educational Resources Information Center

    Lang, Peter F.; Smith, Barry C.

    2010-01-01

    This article describes how data are used to analyze the pattern of ionization energies of the lanthanide elements. Different observed pathways of ionization between different ground states are discussed, and the effects of pairing, exchange, and orbital interactions on ionization energies of the lanthanides are evaluated. When all the above…

  8. Collision energy dependence of product branching in Penning ionization: He*(2 /sup 1/S, 2 /sup 3/S) + H/sub 2/, D/sub 2/, and HD

    SciTech Connect

    Martin, D.W.; Weiser, C.; Sperlein, R.F.; Bernfeld, D.L.; Siska, P.E.

    1989-02-01

    Relative ionization cross sections for the title systems with articulation of all product ion channels have been measured in the collision energy range 1.5--4.0 kcal/mol using crossed supersonic molecular beams; the H/sub 2/ results have been extended down to 0.5 kcal/mol by the use of a 10% H/sub 2//Ar seeded beam. The data are interpreted with a microscopic two-step model that assumes ionization near the turning point in the excited state, a centrifugal barrier criterion for ionic complex formation, and statistical partitioning of flux among the possible ionic products, i.e., phase-space theory. A full statistical calculation underestimates the amount of rearrangement ionization He*+H/sub 2/..-->..HeH/sup +/+H+e/sup -/ by a factor of 2, but one which excludes antiparallel coupling of orbital and rotational angular momenta in the H/sup +//sub 2/ channel is in better accord with the data. A substantial isotope effect favoring HeD/sup +/ over HeH/sup +/ in the HD reactions by a factor of 1.9 +- 0.2 is well represented by the model.

  9. N1s and O1s double ionization of the NO and N{sub 2}O molecules

    SciTech Connect

    Hedin, L.; Zhaunerchyk, V.; Karlsson, L.; Pernestål, K.; Feifel, R.; Tashiro, M.; Ehara, M.; Linusson, P.; Eland, J. H. D.; Ueda, K.

    2014-01-28

    Single-site N1s and O1s double core ionisation of the NO and N{sub 2}O molecules has been studied using a magnetic bottle many-electron coincidence time-of-flight spectrometer at photon energies of 1100 eV and 1300 eV. The double core hole energies obtained for NO are 904.8 eV (N1s{sup −2}) and 1179.4 eV (O1s{sup −2}). The corresponding energies obtained for N{sub 2}O are 896.9 eV (terminal N1s{sup −2}), 906.5 eV (central N1s{sup −2}), and 1174.1 eV (O1s{sup −2}). The ratio between the double and single ionisation energies are in all cases close or equal to 2.20. Large chemical shifts are observed in some cases which suggest that reorganisation of the electrons upon the double ionization is significant. Δ-self-consistent field and complete active space self-consistent field (CASSCF) calculations were performed for both molecules and they are in good agreement with these results. Auger spectra of N{sub 2}O, associated with the decay of the terminal and central N1s{sup −2} as well as with the O1s{sup −2} dicationic states, were extracted showing the two electrons emitted as a result of filling the double core holes. The spectra, which are interpreted using CASSCF and complete active space configuration interaction calculations, show atomic-like character. The cross section ratio between double and single core hole creation was estimated as 1.6 × 10{sup −3} for nitrogen at 1100 eV and as 1.3 × 10{sup −3} for oxygen at 1300 eV.

  10. Ionization and excitation in collisions between antiprotons and H(1s) atoms studied with Sturmian bases

    SciTech Connect

    Winter, Thomas G.

    2011-02-15

    Coupled two-center as well as one-center Sturmian cross sections have been determined for ionization and excitation in p-bar-H(1s) collisions at p-bar energies from 1 to 16 000 keV, following the author's recent work for p-H(1s) collisions [Phys. Rev. A 80, 032701 (2009)]. Basis convergence is studied in detail. Results for ionization and excitation are compared to other coupled-state results and to numerical results, as well as limited experimental results for ionization only. Except for the large, two-center coupled-Gaussian-pseudostate calculation of Toshima for ionization only [Phys. Rev. A 64, 024701 (2001)], previous calculations employed one-center bases, including a one-center Sturmian calculation by Igarashi et al. [Phys. Rev. A 61, 062712 (2000)]. A strong contrast with p-H collisions is confirmed at intermediate energies, while at high energies the extent of agreement is revealed between coupled-state results for the two collisional systems, as well as with first Born results.

  11. Feasibility of coherent xuv spectroscopy on the 1S-2S transition in singly ionized helium

    SciTech Connect

    Herrmann, M.; Saathoff, G.; Gohle, C.; Ozawa, A.; Batteiger, V.; Knuenz, S.; Kolachevsky, N.; Udem, Th.; Haas, M.; Jentschura, U. D.; Kottmann, F.; Leibfried, D.; Schuessler, H. A.; Haensch, T. W.

    2009-05-15

    The 1S-2S two-photon transition in singly ionized helium is a highly interesting candidate for precision tests of bound-state quantum electrodynamics (QED). With the recent advent of extreme ultraviolet frequency combs, highly coherent quasi-continuous-wave light sources at 61 nm have become available, and precision spectroscopy of this transition now comes into reach for the first time. We discuss quantitatively the feasibility of such an experiment by analyzing excitation and ionization rates, propose an experimental scheme, and explore the potential for QED tests.

  12. QED effects in 1s and 2s single and double ionization potentials of the noble gases

    NASA Astrophysics Data System (ADS)

    Niskanen, J.; Jänkälä, K.; Huttula, M.; Föhlisch, A.

    2017-04-01

    We present calculations on the quantum electrodynamics (QED) effects in 1s and 2s single and double ionization potentials of noble gases from Ne to Rn as perturbations on relativistic four-component Dirac-Fock wavefunctions. The most dominant effect originates from the self-energy of the core-electron that yields corrections of similar order as the transverse interaction. For 1s ionization potentials, a match within few eV against the known experimental values is obtained, and our work reveals considerable QED effects in the photoelectron binding energies across the periodic table—most strikingly even for Ne. We perform power-law fits for the corrections as a function of Z and interpolate the QED correction of ˜-0.55 eV for S1s. Due to this, the K-edge electron spectra of the third row and below need QED for a match in the absolute energy when using state-of-the-art instrumentation.

  13. QED effects in 1s and 2s single and double ionization potentials of the noble gases.

    PubMed

    Niskanen, J; Jänkälä, K; Huttula, M; Föhlisch, A

    2017-04-14

    We present calculations on the quantum electrodynamics (QED) effects in 1s and 2s single and double ionization potentials of noble gases from Ne to Rn as perturbations on relativistic four-component Dirac-Fock wavefunctions. The most dominant effect originates from the self-energy of the core-electron that yields corrections of similar order as the transverse interaction. For 1s ionization potentials, a match within few eV against the known experimental values is obtained, and our work reveals considerable QED effects in the photoelectron binding energies across the periodic table-most strikingly even for Ne. We perform power-law fits for the corrections as a function of Z and interpolate the QED correction of ∼-0.55 eV for S1s. Due to this, the K-edge electron spectra of the third row and below need QED for a match in the absolute energy when using state-of-the-art instrumentation.

  14. Absolute cross section for electron-impact ionization of He (1 s 2 s 3S)

    NASA Astrophysics Data System (ADS)

    Génévriez, Matthieu; Jureta, Jozo J.; Defrance, Pierre; Urbain, Xavier

    2017-07-01

    We present an experimental determination of the electron-impact ionization cross section of the 1 s 2 s 3S state of helium, for which there is a serious long-lasting discrepancy between theory and experiment. A technique for the production of a fast, intense beam of helium in the 1 s 2 s 3S state only has been developed for this purpose, based on photodetachment of the He- anion. The cross section is measured using the animated crossed beam technique. The present results are much lower than the experimental data of Dixon et al. [J. Phys. B 9, 2617 (1976), 10.1088/0022-3700/9/15/013] and are in excellent agreement with the calculation of Fursa and Bray [J. Phys. B 36, 1663 (2003), 10.1088/0953-4075/36/8/317].

  15. Gas-Liquid Correlation of Ionization Energies.

    DTIC Science & Technology

    1984-04-01

    ions and water. The threshold and reorganization energies of the hydrated electron are calculated from threshold energies of anions and their absorption...hydroxide ions and water. The threshold and reorganization energies of the hydrated electron are calculated from threshold energies of anions and their...threshold energy of the hydrated electron. 2. Free energy of emission and gas-phase ionization Consider the photoelectron emission by an aqueous

  16. Overexpression of c-Myc alters G(1)/S arrest following ionizing radiation.

    PubMed

    Sheen, Joon-Ho; Dickson, Robert B

    2002-03-01

    Study of the mechanism(s) of genomic instability induced by the c-myc proto-oncogene has the potential to shed new light on its well-known oncogenic activity. However, an underlying mechanism(s) for this phenotype is largely unknown. In the present study, we investigated the effects of c-Myc overexpression on the DNA damage-induced G(1)/S checkpoint, in order to obtain mechanistic insights into how deregulated c-Myc destabilizes the cellular genome. The DNA damage-induced checkpoints are among the primary safeguard mechanisms for genomic stability, and alterations of cell cycle checkpoints are known to be crucial for certain types of genomic instability, such as gene amplification. The effects of c-Myc overexpression were studied in human mammary epithelial cells (HMEC) as one approach to understanding the c-Myc-induced genomic instability in the context of mammary tumorigenesis. Initially, flow-cytometric analyses were used with two c-Myc-overexpressing, nontransformed immortal lines (184A1N4 and MCF10A) to determine whether c-Myc overexpression leads to alteration of cell cycle arrest following ionizing radiation (IR). Inappropriate entry into S phase was then confirmed with a bromodeoxyuridine incorporation assay measuring de novo DNA synthesis following IR. Direct involvement of c-Myc overexpression in alteration of the G(1)/S checkpoint was then confirmed by utilizing the MycER construct, a regulatable c-Myc. A transient excess of c-Myc activity, provided by the activated MycER, was similarly able to induce the inappropriate de novo DNA synthesis following IR. Significantly, the transient expression of full-length c-Myc in normal mortal HMECs also facilitated entry into S phase and the inappropriate de novo DNA synthesis following IR. Furthermore, irradiated, c-Myc-infected, normal HMECs developed a sub-G(1) population and a >4N population of cells. The c-Myc-induced alteration of the G(1)/S checkpoint was also compared to the effects of expression of MycS (N

  17. Single and double ionization of the camphor molecule excited around the C 1s edge.

    PubMed

    de Castilho, R B; Ramalho, T C; Nunez, C V; Coutinho, L H; Santos, A C F; Pilling, S; Lago, A F; Silva-Moraes, M O; de Souza, G G B

    2014-08-15

    An interesting class of volatile compounds, the monoterpenes, is present in some plants although their functions are not yet fully understood. We have studied the interaction of the camphor molecule with monochromatic high-energy photons (synchrotron radiation) using time-of-flight mass spectrometry and coincidence techniques. A commercial sample of S-camphor was admitted into the vacuum chamber, without purification, through an inlet system. Monochromatic light with energy around the C 1s edge was generated by the TGM beamline at the Brazilian Synchrotron Facility. A Wiley-McLaren mass spectrometer was used to characterize and detect the ions formed by the camphor photoionization. The data analysis was supported by energy calculations. Although the fragmentation patterns were basically the same at 270 eV and 330 eV, it was observed that above the C 1s edge the contribution to the spectrum from lower mass/charge fragment ions increased, pointing to a higher degree of dissociation of the molecule. Projections of the PEPIPICO spectra demonstrated the existence of unstable doubly charged species. The Gibbs free energy was calculated using the Møller-Plesset perturbation theory (MP2) for the neutral, singly and doubly excited camphor molecule. Our PEPIPICO spectrum clearly demonstrated the formation of doubly ionic dissociative species. From a slope analysis, we propose a secondary decay after a deferred charge separation mechanism in which, after a few steps, the camphor dication dissociates into C2 H3 (+) and C3 H5 (+) . This is the main relaxation route observed at 270 eV and 330 eV. The large energy difference between the mono and the dication (of the order of 258.2 kcal/mol) may explain the experimentally observed absence of stable dications in the spectra, because their formation is disadvantaged energetically. Copyright © 2014 John Wiley & Sons, Ltd.

  18. Intensity oscillations in the carbon 1s ionization cross sections of 2-butyne

    SciTech Connect

    Carroll, Thomas X.; Zahl, Maria G.; Borve, Knut J.; Saethre, Leif J.; Decleva, Piero; Ponzi, Aurora; Kas, Joshua J.; Vila, Fernando D.; Rehr, John J.; Thomas, T. Darrah

    2013-06-21

    Carbon 1s photoelectron spectra for 2-butyne (CH{sub 3}C{identical_to}CCH{sub 3}) measured in the photon energy range from threshold to 150 eV above threshold show oscillations in the intensity ratio C2,3/C1,4. Similar oscillations have been seen in chloroethanes, where the effect has been attributed to EXAFS-type scattering from the substituent chlorine atoms. In 2-butyne, however, there is no high-Z atom to provide a scattering center and, hence, oscillations of the magnitude observed are surprising. The results have been analyzed in terms of two different theoretical models: a density-functional model with B-spline atom-centered functions to represent the continuum electrons and a multiple-scattering model using muffin-tin potentials to represent the scattering centers. Both methods give a reasonable description of the energy dependence of the intensity ratios.

  19. Ionization Energy: Implications of Preservice Teachers' Conceptions

    ERIC Educational Resources Information Center

    Tan, Kim Chwee Daniel; Taber, Keith S.

    2009-01-01

    The results from a study to explore pre-service teachers' understanding of ionization energy, a topic that features in A-level (grade 11 and 12) chemistry courses. in Singapore , is described. A previous study using a two-tier multiple choice diagnostic test has shown that Singapore A-level students have considerable difficulty understanding the…

  20. Ionization Energy: Implications of Preservice Teachers' Conceptions

    ERIC Educational Resources Information Center

    Tan, Kim Chwee Daniel; Taber, Keith S.

    2009-01-01

    The results from a study to explore pre-service teachers' understanding of ionization energy, a topic that features in A-level (grade 11 and 12) chemistry courses. in Singapore , is described. A previous study using a two-tier multiple choice diagnostic test has shown that Singapore A-level students have considerable difficulty understanding the…

  1. Double-K-vacancy states in electron-impact single ionization of metastable two-electron N5+(1s2s 3S1) ions

    NASA Astrophysics Data System (ADS)

    Müller, A.; Borovik, A.; Huber, K.; Schippers, S.; Fursa, D. V.; Bray, I.

    2014-07-01

    The role of hollow states intermediately produced in electron-impact ionization of metastable He-like N5+(1s2s3S1) ions has been investigated in detail. A crossed-beam setup and suitable experimental techniques were employed for the measurement of accurate absolute cross sections and precise energy-scan data. Fine structures arising from K-shell excitations and associated resonances have been observed for this two-electron ion with less than ±0.5 eV uncertainty on the energy scale. Fine details, such as interference of the reaction pathways of direct ionization and excitation with capture of the incident electron followed by double-Auger decay, could be revealed. Ab initio calculations based on the convergent close coupling (CCC) approach are in good agreement with the experiment.

  2. Ground Levels and Ionization Energies for the Neutral Atoms

    National Institute of Standards and Technology Data Gateway

    SRD 111 Ground Levels and Ionization Energies for the Neutral Atoms (Web, free access)   Data for ground state electron configurations and ionization energies for the neutral atoms (Z = 1-104) including references.

  3. Role of Penning ionization in the enhancement of streamer channel conductivity and Ar(1s{sub 5}) production in a He-Ar plasma jet

    SciTech Connect

    Sands, Brian L.; Huang, Shih K.; Speltz, Jared W.; Niekamp, Matthew A.; Ganguly, Biswa N.

    2013-04-21

    Plasma jet devices that use a helium gas flow mixed with a small percentage of argon have been shown to operate with a larger discharge current and enhanced production of the Ar(1s{sub 5}) metastable state, particularly in the discharge afterglow. In this experiment, time-resolved quantitative measurements of He(2{sup 3}S{sub 1}) and Ar(1s{sub 5}) metastable species were combined with current and spectrally resolved emission measurements to elucidate the role of Penning ionization in a helium plasma jet with a variable argon admixture. The plasma jet was enclosed in a glass chamber through which a flowing nitrogen background was maintained at 600 Torr. At 3%-5% Ar admixture, we observed a {approx}50% increase in the peak circuit current and streamer velocity relative to a pure helium plasma jet for the same applied voltage. The streamer initiation delay also decreased by {approx}20%. Penning ionization of ground-state argon was found to be the dominant quenching pathway for He(2{sup 3}S{sub 1}) up to 2% Ar and was directly correlated with a sharp increase in both the circuit current and afterglow production of Ar(1s{sub 5}) for Ar admixtures up to 1%, but not necessarily with the streamer velocity, which increased more gradually with Ar concentration. Ar(1s{sub 5}) was produced in the afterglow through recombination of Ar{sup +} and dissociative recombination of Ar{sub 2}{sup +} as the local mean electron energy decreased in the plasma channel behind the streamer head. The discharge current and argon metastable enhancement are contingent on the rapid production of He(2{sup 3}S{sub 1}) near the streamer head, >5 Multiplication-Sign 10{sup 12} cm{sup -3} in 30 ns under the conditions of this experiment.

  4. Ionization energy of acetone by vacuum ultraviolet mass-analyzed threshold ionization spectrometry

    NASA Astrophysics Data System (ADS)

    Kim, Jae Han; Kang, Do Won; Hong, Yong Jun; Hwang, Hyonseok; Kim, Hong Lae; Kwon, Chan Ho

    2013-04-01

    Mass-analyzed threshold ionization (MATI) time-of-flight mass spectrometer using coherent vacuum ultraviolet (VUV) laser generated by four-wave difference frequency mixing (FWDFM) in Kr has been constructed and utilized to obtain the accurate ionization energy of acetone. From the MATI onsets measured from various applied pulsed fields, the ionization energy to the ionic ground state of acetone has been determined to be 9.7074 ± 0.0019 eV.

  5. Lanthanide Ionization Energies and the Sub-Shell Break. Part 1. The Second Ionization Energies

    NASA Astrophysics Data System (ADS)

    Johnson, David A.; Nelson, Peter G.

    2017-03-01

    By interpolating a 4fq6s → 4fq7s transition within the sequence f1 → f14 rather than between f0 and f14, revised second ionization energies of the lanthanides have been obtained. In the early part of the series, between cerium and samarium, the revisions are significantly higher than currently accepted values. The revised values have been used to calculate the energy variation for the conversion of Ln(g, 4fq6s2) to Ln2+(g, 4fq) across the series Ba → Yb. The variation is smooth between lanthanum and ytterbium but the barium point at q = 0 is displaced downwards by more than 0.3 eV, thereby representing a significant sub-shell break. A case is also made for a substantial change to the second ionization energy of lutetium, the revised value being 14.13 ± 0.10 eV.

  6. First determination of ionization energies of phenylnitrene

    NASA Astrophysics Data System (ADS)

    Huijuan, Che; Huimin, Bi; Rui, Ding; Dong, Wang; Lingpeng, Meng; Shijun, Zheng; Dianxun, Wang; Mok, Daniel Kam-Wak; Chau, Foo-Tim

    2003-12-01

    The continuous flowing beams of the triplet state phenylnitrene (PhN) species have been generated by respective pyrolysis of PhN 3 at 83(±0.5) °C and phenylisocyanate (PhNCO) at 105(±0.5) °C in the quartz inlet tube loosely filled with a 30 Å molecular sieve powder supported on the quartz wool. PE spectrum of PhN is recorded in situ for the first time. The ionization energies, corresponding to different ionic states of PhN +, are determined by PES experiment and both G2 and DFT calculations. The study indicates that PhN is a diradical with C 2v symmetry and has a 3A 2 ground state.

  7. Ionizing Energy Depositions After Fast Neutron Interactions in Silicon

    DOE PAGES

    Bergmann, Benedikt; Pospisil, Stanislav; Caicedo, Ivan; ...

    2016-06-01

    In our study we present the ionizing energy depositions in a 300 μm thick silicon layer after fast neutron impact. With the Time-of-Flight (ToF) technique, the ionizing energy deposition spectra of recoil silicons and secondary charged particles were assigned to (quasi-)monoenergetic neutron energies in the range from 180 keV to hundreds of MeV. We also show and interpret representative measured energy spectra. By separating the ionizing energy losses of the recoil silicon from energy depositions by products of nuclear reactions, the competition of ionizing (IEL) and non-ionizing energy losses (NIEL) of a recoil silicon within the silicon lattice was investigated.more » Furthermore, the data give supplementary information to the results of a previous measurement and are compared with different theoretical predictions.« less

  8. Ionizing Energy Depositions After Fast Neutron Interactions in Silicon

    SciTech Connect

    Bergmann, Benedikt; Pospisil, Stanislav; Caicedo, Ivan; Kierstead, James; Takai, Helio; Frojdh, Erik

    2016-06-01

    In our study we present the ionizing energy depositions in a 300 μm thick silicon layer after fast neutron impact. With the Time-of-Flight (ToF) technique, the ionizing energy deposition spectra of recoil silicons and secondary charged particles were assigned to (quasi-)monoenergetic neutron energies in the range from 180 keV to hundreds of MeV. We also show and interpret representative measured energy spectra. By separating the ionizing energy losses of the recoil silicon from energy depositions by products of nuclear reactions, the competition of ionizing (IEL) and non-ionizing energy losses (NIEL) of a recoil silicon within the silicon lattice was investigated. Furthermore, the data give supplementary information to the results of a previous measurement and are compared with different theoretical predictions.

  9. Ionizing Energy Depositions After Fast Neutron Interactions in Silicon

    SciTech Connect

    Bergmann, Benedikt; Pospisil, Stanislav; Caicedo, Ivan; Kierstead, James; Takai, Helio; Frojdh, Erik

    2016-06-01

    In our study we present the ionizing energy depositions in a 300 μm thick silicon layer after fast neutron impact. With the Time-of-Flight (ToF) technique, the ionizing energy deposition spectra of recoil silicons and secondary charged particles were assigned to (quasi-)monoenergetic neutron energies in the range from 180 keV to hundreds of MeV. We also show and interpret representative measured energy spectra. By separating the ionizing energy losses of the recoil silicon from energy depositions by products of nuclear reactions, the competition of ionizing (IEL) and non-ionizing energy losses (NIEL) of a recoil silicon within the silicon lattice was investigated. Furthermore, the data give supplementary information to the results of a previous measurement and are compared with different theoretical predictions.

  10. Field ionization of free helium atoms: Correlation between the kinetic energy of ionized atoms and probability of their field ionization

    NASA Astrophysics Data System (ADS)

    Piskur, J.; Borg, L.; Stupnik, A.; Leisch, M.; Ernst, W. E.; Holst, B.

    2008-05-01

    In this paper the correlation between the kinetic energy of helium atoms and the probability of field ionization is investigated by exploiting the narrow velocity distribution of supersonic molecular beams. Field ionization measurements were carried out on supersonic helium beams at 298 K and 95 K corresponding to energies of about 65 meV and 20 meV, respectively, for the individual atoms. The field ionization was performed with a tungsten tip, radius of curvature 12 nm, kept at room temperature. The ionization probability was found to increase by about a factor 10 when the beam was cooled from 298 K to 95 K. The results presented in this paper are of importance for improving the understanding of field ionization and for the development of a new detector for helium and other molecular beams.

  11. Size Effect in the Ionization Energy of PAH Clusters

    PubMed Central

    2017-01-01

    We report the first experimental measurement of the near-threshold photoionization spectra of polycyclic aromatic hydrocarbon clusters made of pyrene C16H10 and coronene C24H12, obtained using imaging photoelectron–photoion coincidence spectrometry with a VUV synchrotron beamline. The experimental results of the ionization energy are compared to calculated ones obtained from simulations using dedicated electronic structure treatment for large ionized molecular clusters. Experiment and theory consistently find a decrease of the ionization energy with cluster size. The inclusion of temperature effects in the simulations leads to a lowering of this energy and to quantitative agreement with the experiment. In the case of pyrene, both theory and experiment show a discontinuity in the IE trend for the hexamer. This work demonstrates the ability of the models to describe the electronic structure of PAH clusters and suggests that these species are ionized in astronomical environments where they are thought to be present. PMID:28742357

  12. Plasmadynamics and ionization kinetics of thermionic energy conversion

    SciTech Connect

    Lawless, J.L. Jr.; Lam, S.H.

    1982-02-01

    To reduce the plasma arc-drop, thermionic energy conversion is studied with both analytical and numerical tools. Simplifications are made in both the plasmadynamic and ionization-recombination theories. These are applied to a scheme proposed presently using laser irradiation to enhance the ionization kinetics of the thermionic plasma and thereby reduce the arc-drop. It is also predicted that it is possible to generate the required laser light from a thermionic-type cesium plasma. The analysis takes advantage of theoretical simplifications derived for the ionization-recombination kinetics. It is shown that large laser ionization enhancements can occur and that collisional cesium recombination lasing is expected. To complement the kinetic theory, a numerical method is developed to solve the thermionic plasma dynamics. To combine the analysis of ionization-recombination kinetics with the plasma dynamics of thermionic conversion, a finite difference computer program is constructed. It is capable of solving for both unsteady and steady thermionic converter behavior including possible laser ionization enhancement or atomic recombination lasing. A proposal to improve thermionic converter performance using laser radiation is considered. In this proposed scheme, laser radiation impinging on a thermionic plasma enhances the ionization process thereby raising the plasma density and reducing the plasma arc-drop. A source for such radiation may possibly be a cesium recombination laser operating in a different thermionic converter. The possibility of this being an energy efficient process is discussed. (WHK)

  13. Analytic saddlepoint approximation for ionization energy loss distributions

    NASA Astrophysics Data System (ADS)

    Sjue, S. K. L.; George, R. N.; Mathews, D. G.

    2017-09-01

    We present a saddlepoint approximation for ionization energy loss distributions, valid for arbitrary relativistic velocities of the incident particle 0 < v / c < 1 , provided that ionizing collisions are still the dominant energy loss mechanism. We derive a closed form solution closely related to Moyal's distribution. This distribution is intended for use in simulations with relatively low computational overhead. The approximation generally reproduces the Vavilov most probable energy loss and full width at half maximum to better than 1% and 10%, respectively, with significantly better agreement as Vavilov's κ approaches 1.

  14. Polycyclic Aromatic Hydrocarbon Ionization Energy Lowering in Water Ices

    NASA Technical Reports Server (NTRS)

    Gudipati, Murthy S.; Allamandola, Louis J.

    2004-01-01

    In studying various interstellar and solar system ice analogs, we have recently found that upon vacuum ultraviolet photolysis, polycyclic aromatic hydrocarbons (PAHs) frozen in water ice at low temperatures are easily ionized and indefinitely stabilized as trapped ions (Gudipati; Gudipati & Allamandola). Here we report the first experimental study that shows that PAH ionization energy is significantly lowered in PAH/H2O ices, in agreement with recent theoretical work (Woon & Park). The ionization energy (IE) of the PAH studied here, quaterrylene (C40H20, IE = 6.11 eV), is lowered by up to 2.11 eV in water ice. PAH ionization energy reduction in low-temperature water ice substantially expands the astronomical regions in which trapped ions and electrons may be important. This reduction in ionization energy should also hold for other types of trapped species in waterrich interstellar, circumstellar, and solar system ices. Subject headings: ISM: clouds - methods: laboratory - molecular processes - radiation mechanisms: nonthermal -ultraviolet: ISM - ultraviolet: solar system

  15. Relativistic contributions to single and double core electron ionization energies of noble gases.

    PubMed

    Niskanen, J; Norman, P; Aksela, H; Agren, H

    2011-08-07

    We have performed relativistic calculations of single and double core 1s hole states of the noble gas atoms in order to explore the relativistic corrections and their additivity to the ionization potentials. Our study unravels the interplay of progression of relaxation, dominating in the single and double ionization potentials of the light elements, versus relativistic one-electron effects and quantum electrodynamic effects, which dominate toward the heavy end. The degree of direct relative additivity of the relativistic corrections for the single electron ionization potentials to the double electron ionization potentials is found to gradually improve toward the heavy elements. The Dirac-Coulomb Hamiltonian is found to predict a scaling ratio of ∼4 for the relaxation induced relativistic energies between double and single ionization. Z-scaling of the computed quantities were obtained by fitting to power law. The effects of nuclear size and form were also investigated and found to be small. The results indicate that accurate predictions of double core hole ionization potentials can now be made for elements across the full periodic table.

  16. Relativistic contributions to single and double core electron ionization energies of noble gases

    SciTech Connect

    Niskanen, J.; Norman, P.; Aksela, H.; Aagren, H.

    2011-08-07

    We have performed relativistic calculations of single and double core 1s hole states of the noble gas atoms in order to explore the relativistic corrections and their additivity to the ionization potentials. Our study unravels the interplay of progression of relaxation, dominating in the single and double ionization potentials of the light elements, versus relativistic one-electron effects and quantum electrodynamic effects, which dominate toward the heavy end. The degree of direct relative additivity of the relativistic corrections for the single electron ionization potentials to the double electron ionization potentials is found to gradually improve toward the heavy elements. The Dirac-Coulomb Hamiltonian is found to predict a scaling ratio of {approx}4 for the relaxation induced relativistic energies between double and single ionization. Z-scaling of the computed quantities were obtained by fitting to power law. The effects of nuclear size and form were also investigated and found to be small. The results indicate that accurate predictions of double core hole ionization potentials can now be made for elements across the full periodic table.

  17. Comments on GUT monopole energy loss and ionization

    SciTech Connect

    Hagstrom, R.

    1982-01-01

    A few comments about the likely behavior of the electromagnetic energy loss and ionization rates of super-slowly moving magnetic monopoles are presented. The questions of energy loss rates and ionization rates for super-low monopoles passing through matter are considered, concentrating on aspects of these issues which affect practical detection techniques. It is worthwhile here to emphasize that there is a potentially great distinction between energy loss rates and ionization rates and that the magnitude of this distinction is really the great issue which must be settled in order to understand the significance of experimental results from present and proposed investigations of the slow monopole question. Energy loss here means the total dE/dX of the projectile due to interactions with the electrons of the slowing medium. To the extent that nuclear collisions can be neglected, this so-called electronic energy loss is the relevant quantity in questions about whether monopoles stop within the earth's crust, whether they are slowed by interstellar plasmas, or the signal in a truly calorimetric measurement (measuring temperature rises along the trajectory), etc. Most of our successful detection techniques depend upon the promotion of ground state electrons into states which lie above some energy gap in the material of the detector: electrons must be knocked completely free from the gas atoms in a proportional chamber gas, electrons must be promoted to a higher band in solid scintillator plastics. These processes are generically identified as ionization. (WHK)

  18. Radial behavior of the average local ionization energies of atoms

    SciTech Connect

    Politzer, P.; Murray, J.S.; Grice, M.E.; Brinck, T.; Ranganathan, S. )

    1991-11-01

    The radial behavior of the average local ionization energy {ital {bar I}}({bold r}) has been investigated for the atoms He--Kr, using {ital ab} {ital initio} Hartree--Fock atomic wave functions. {ital {bar I}}({bold r}) is found to decrease in a stepwise manner with the inflection points serving effectively to define boundaries between electronic shells. There is a good inverse correlation between polarizability and the ionization energy in the outermost region of the atom, suggesting that {ital {bar I}}({bold r}) may be a meaningful measure of local polarizabilities in atoms and molecules.

  19. Scattering of H(1s) off metastable helium atom at thermal energies

    SciTech Connect

    Sinha, Prabal K.; Ghosh, A. S.

    2006-06-15

    Quantal calculations for scattering of ground-state antihydrogen by metastable (n=2S) helium atoms have been performed using the nonadiabatic, atomic orbital expansion technique at thermal energies. The zero-energy elastic cross sections of the present systems are much greater than the corresponding value for the ground-state helium target. The low-energy elastic cross section for the singlet metastable helium [He(2 {sup 1}S)] target is higher than the corresponding value when the target is in the metastable triplet state [He(2 {sup 3}S)].

  20. Ionization cooling in a low-energy proton storage ring

    SciTech Connect

    Neuffer, David V.; /Fermilab

    2006-03-01

    At the FFAG05 meeting, Mori and Okabe presented a scenario in which the lifetime of protons in a low-energy storage ring ({approx}10 MeV) is extended by energy-loss in a wedge foil, and this enables greater neutron production from the foil. The lifetime extension is due to the cooling effect of this energy loss. We have previously analyzed ionization cooling for muons at optimal cooling energies. The same equations, with appropriate adaptations, can be used to analyze the dynamic situation for proton-material interactions at low energies. In this note we discuss this extension and calculate cooling and heating effects at these very different parameters. The ring could provide a practical application of ionization cooling methods.

  1. Electron impact ionization at relativistic energies

    NASA Astrophysics Data System (ADS)

    Belkacem, Ali; Cole, Kyra; Hertlein, Marcus; Feinberg, Benedict; Schriel, Ralf; Adaniya, Hidehito; Neumann, Nadine

    2004-05-01

    We used an ion time-of-flight set up based on a pulsed high-voltage extraction technique to study the charge state distribution of He, Ne, Ar, Kr and Xe atoms after impact of 0.2 to 1.5 GeV electrons. The relativistic electron beam is produced at the booster beamline at the Advanced Light Source at the Lawrence Berkeley National Laboratory. The yield of ions drops drastically with the charge state number. Our measurements show that the ratio of doubly-charge to singly-charged ions reaches an asymptotic limit of 0.0028 for He already at electron energies below 40 MeV. However we observe a very pronounced energy dependence of the ratio of the doubly-charged to singly-charged ions for the heavier atoms such as Kr and Xe in the 0.2 - 1.5 GeV energy range. This energy dependence takes place way above the energy at which theories based on the equivalent photon method or the born- approximation predict the asymptotic limit to be reached. This may be an indication of new physics coming into play in the photoionization process due to relativistic effects.

  2. Trends in Ionization Energy of Transition-Metal Elements

    ERIC Educational Resources Information Center

    Matsumoto, Paul S.

    2005-01-01

    A rationale for the difference in the periodic trends in the ionization energy of the transition-metal elements versus the main-group elements is presented. The difference is that in the transition-metal elements, the electrons enter an inner-shell electron orbital, while in the main-group elements, the electrons enter an outer-shell electron…

  3. Trends in Ionization Energy of Transition-Metal Elements

    ERIC Educational Resources Information Center

    Matsumoto, Paul S.

    2005-01-01

    A rationale for the difference in the periodic trends in the ionization energy of the transition-metal elements versus the main-group elements is presented. The difference is that in the transition-metal elements, the electrons enter an inner-shell electron orbital, while in the main-group elements, the electrons enter an outer-shell electron…

  4. Average local ionization energy generalized to correlated wavefunctions

    SciTech Connect

    Ryabinkin, Ilya G.; Staroverov, Viktor N.

    2014-08-28

    The average local ionization energy function introduced by Politzer and co-workers [Can. J. Chem. 68, 1440 (1990)] as a descriptor of chemical reactivity has a limited utility because it is defined only for one-determinantal self-consistent-field methods such as the Hartree–Fock theory and the Kohn–Sham density-functional scheme. We reinterpret the negative of the average local ionization energy as the average total energy of an electron at a given point and, by rewriting this quantity in terms of reduced density matrices, arrive at its natural generalization to correlated wavefunctions. The generalized average local electron energy turns out to be the diagonal part of the coordinate representation of the generalized Fock operator divided by the electron density; it reduces to the original definition in terms of canonical orbitals and their eigenvalues for one-determinantal wavefunctions. The discussion is illustrated with calculations on selected atoms and molecules at various levels of theory.

  5. Energy calculation for beryllium atom in different excited states (1s2 2s 3s), (1s 2s2 3s) and (1s 2s 3s2)

    NASA Astrophysics Data System (ADS)

    Al-Sharaa, Mayada J.; Mahmood, Maysoon A.; Madhkoor, Naaemh C. H.; Al-Bayati, Khalil H.

    2017-09-01

    The energy expectation value E has been evaluated for Beryllium different excited state and Be like ions such as B+1 and C+2 and the potential energy expectation value V has been evaluated too. The partitioning technique of Hartree-Fock (H-F) has been used for existing wave functions. The results show that the expectation values of and < r12 -1> of (1s2s 3s2), (1s2s23s) and (1s2s 3s2) states increase when the atomic number (Z) increases for all shells for Be-like ions. All the studied properties are calculated using atomic units.

  6. Ionization energy and active cation vibrations of trans-2-fluorostyrene

    NASA Astrophysics Data System (ADS)

    Wu, Pei Ying; Tzeng, Sheng Yuan; Hsu, Ya Chu; Tzeng, Wen Bih

    2017-02-01

    We applied the two-color resonant two-photon mass-analyzed threshold ionization (MATI) technique to record the cation spectra of trans-2-fluorostyrene by ionizing via six intermediate vibronic levels. The adiabatic ionization energy was determined to be 69 304 ± 5 cm-1. The distinct MATI bands at 67, 124, 242, 355, 737, 806, 833, and 993 cm-1 were assigned to the active cation vibrations related to out-of-plane substituent-sensitive bending vibrations and in-plane ring deformation and bending motions. Many combination vibrations were also observed. Our experimental results suggest that the molecular geometry and vibrational coordinates of the trans-2-fluorostyrene cation in the D0 state resemble those of the neutral species in the S1 state.

  7. Cascade L-shell soft-x-ray emission as incident x-ray photons are tuned across the 1s ionization threshold

    SciTech Connect

    Sokaras, D.; Andrianis, M.; Lagoyannis, A.; Kochur, A. G.; Mueller, M.; Kolbe, M.; Beckhoff, B.; Mantler, M.; Zarkadas, Ch.; Karydas, A. G.

    2011-05-15

    The cascade L-shell x-ray emission as an incident polarized and unpolarized monochromatic radiation overpass the 1s ionization threshold is investigated for the metallic Fe by means of moderate resolution, quantitative x-ray spectrometry. A full ab initio theoretical investigation of the L-shell x-ray emission processes is performed based on a detailed straightforward construction of the cascade decay trees within the Pauli-Fock approximation. The agreement obtained between experiments and the presented theory is indicated and discussed with respect to the accuracy of advanced atomic models as well as its significance for the characterization capabilities of x-ray fluorescence (XRF) analysis.

  8. Low-energy electron rescattering in laser-induced ionization

    NASA Astrophysics Data System (ADS)

    Becker, W.; Goreslavski, S. P.; Milošević, D. B.; Paulus, G. G.

    2014-10-01

    The low-energy structure (LES) in the energy spectrum of above-threshold ionization of rare-gas atoms is reinvestigated from three different points of view. First, the role of forward rescattering in the completely classical simple-man model (SMM) is considered. Then, the corresponding classical electronic trajectories are retrieved in the quantum-mechanical ionization amplitude derived in the strong-field approximation augmented to allow for rescattering. Third, classical trajectories in the presence of both the laser field and the Coulomb field are scrutinized in order to see how they are related to the LES. It is concluded that the LES is already rooted in the SMM. The Coulomb field enhances the structure so that it can successfully compete with other contributions and become visible in the total spectrum.

  9. On the adiabatic ionization energy of the propargyl radical.

    PubMed

    Jacovella, U; Gans, B; Merkt, F

    2013-08-28

    The photoionization and pulsed-field-ionization zero-kinetic-energy photoelectron spectra of the propargyl radical have been recorded in the vicinity of the origin of the X(+) (1)A1←X(2)B1 photoionizing transition. An internally cold sample of propargyl with a rotational temperature of ~45 K was produced in a supersonic expansion of 1,3-butadiene in helium. Propargyl was generated by excimer laser (ArF, 193 nm) photolysis of 1,3-butadiene in a quartz capillary mounted at the exit of a pulsed valve. The rotational structure of the origin band of the photoelectron spectrum was partially resolved and an improved value of the adiabatic ionization energy of propargyl (E(I)/hc = 70174.5(20) cm(-1)) was determined.

  10. On the adiabatic ionization energy of the propargyl radical

    NASA Astrophysics Data System (ADS)

    Jacovella, U.; Gans, B.; Merkt, F.

    2013-08-01

    The photoionization and pulsed-field-ionization zero-kinetic-energy photoelectron spectra of the propargyl radical have been recorded in the vicinity of the origin of the tilde{X}^+ ^1A_1 leftarrow tilde{X} ^2B_1 photoionizing transition. An internally cold sample of propargyl with a rotational temperature of ˜45 K was produced in a supersonic expansion of 1,3-butadiene in helium. Propargyl was generated by excimer laser (ArF, 193 nm) photolysis of 1,3-butadiene in a quartz capillary mounted at the exit of a pulsed valve. The rotational structure of the origin band of the photoelectron spectrum was partially resolved and an improved value of the adiabatic ionization energy of propargyl (EI/hc = 70174.5(20) cm-1) was determined.

  11. Velocity dependence for the chemi-ionization of Ar, Kr, N/sub 2/, CO, and O/sub 2/ by He(2 /sup 1/S) and He(2 /sup 3/S) metastable atoms

    SciTech Connect

    Parr, T.P.; Parr, D.M.; Martin, R.M.

    1982-01-01

    The velocity dependence of the title reactions was measured using crossed molecular beams and time-of-flight velocity dispersion of the metastable helium atoms. The relative collision energy ranged from 6--10 to 600--800 meV. The singlet cross section energy dependences are all of the ''repulsive'' type, i.e., increasing with energy at low energies, implying that the interaction potential well depths are < or approx. =6--8 meV. The triplet cross sections are also generally repulsive, but the Ar, Kr, and O/sub 2/ cases show evidence of minimums at the lowest energies. These observations are in qualitative agreement with the available interaction potential data. The cross section curves were put on an absolute basis by normalization to thermal quenching rate constants. The cross sections tend to approach the same magnitude at high energies and diverge at low energies. The singlet cross sections increase more rapidly than the triplet cross sections at low energies, with the singlet Ar, Kr, and N/sub 2/ curves having especially steep slopes. Theoretical cross section curves were calculated for the He(/sup 1/S,/sup 3/S)/Ar, Kr cases using interaction potentials available from differential scattering studies. The results are in good agreement with experiment, and confirm the need for unusual low energy repulsive structure in the singlet potentials to explain the collisional energy dependence of chemi-ionization.

  12. Low-energy structures in strong-field ionization

    NASA Astrophysics Data System (ADS)

    Ivanov, I. A.; Nam, Chang Hee; Kim, Kyung Taec

    2016-04-01

    We show that the Gabor transform provides a convenient tool allowing one to study the origin of the low-energy structures (LES) in the process of the strong-field ionization. The classical trajectories associated with the stationary points of the Gabor transform enable us to explicate the role of the forward scattering process in forming LES. Our approach offers a fully quantum mechanical description of LES, which can also be applied for other strong-field processes.

  13. Quantitative ionization energies and work functions of aqueous solutions.

    PubMed

    Olivieri, Giorgia; Goel, Alok; Kleibert, Armin; Cvetko, Dean; Brown, Matthew A

    2016-10-26

    Despite the ubiquitous nature of aqueous solutions across the chemical, biological and environmental sciences our experimental understanding of their electronic structure is rudimentary-qualitative at best. One of the most basic and seemingly straightforward properties of aqueous solutions-ionization energies-are (qualitatively) tabulated at the water-air interface for a mere handful of solutes, and the manner in which these results are obtained assume the aqueous solutions behave like a gas in the photoelectron experiment (where the vacuum levels of the aqueous solution and of the photoelectron analyzer are equilibrated). Here we report the experimental measure of a sizeable offset (ca. 0.6 eV) between the vacuum levels of an aqueous solution (0.05 M NaCl) and that of our photoelectron analyzer, indicating a breakdown of the gas-like vacuum level alignment assumption for the aqueous solution. By quantifying the vacuum level offset as a function of solution chemical composition our measurements enable, for the first time, quantitative determination of ionization energies in liquid solutions. These results reveal that the ionization energy of liquid water is not independent of the chemical composition of the solution as is usually inferred in the literature, a finding that has important ramifications as measured ionization energies are frequently used to validate theoretical models that posses the ability to provide microscopic insight not directly available by experiment. Finally, we derive the work function, or the electrochemical potential of the aqueous solution and show that it too varies with the chemical composition of the solution.

  14. Effect of the corrected ionization potential and spatial distribution on the angular and energy distribution in tunnel ionization

    SciTech Connect

    Petrović, V. M.; Miladinović, T. B.

    2016-05-15

    Within the framework of the Ammosov–Delone–Krainov theory, we consider the angular and energy distribution of outgoing electrons due to ionization by a circularly polarized electromagnetic field. A correction of the ground ionization potential by the ponderomotive and Stark shift is incorporated in both distributions. Spatial dependence is analyzed.

  15. The effect of microhydration on ionization energies of thymine

    SciTech Connect

    Khistyev, Kirill; Bravaya, Ksenia B.; Kamarchik, Eugene; Kostko, Oleg; Ahmed, Musahid; Krylov, Anna I.

    2011-01-03

    A combined theoretical and experimental study of the effect of microhydration on ionization energies (IEs) of thymine is presented. The experimental IEs are derived from photoionization efficiency curves recorded using tunable synchrotron VUV radiation. The onsets of the PIE curves are 8.85+-0.05, 8.60+-0.05, 8.55+-0.05, and 8.40+-0.05 eV for thymine, thymine mono-, di-, and tri-hydrates, respectively. The computed (EOM-IP-CCSD/cc-pVTZ) AIEs are 8.90, 8.51, 8.52, and 8.35 eV for thymine and the lowest isomers of thymine mono-, di-, and tri-hydrates. Due to large structural relaxation, the Franck-Condon factors for the 0<-- 0 transitions are very small shifting the apparent PIE onsets to higher energies. Microsolvation strongly affects IEs of thymine -- addition of each water molecule reduces the first vertical IE by 0.10-0.15 eV. The adiabatic IE decreases even more (up to 0.4 eV). The magnitude of the effect varies for different ionized states and for different isomers. For the ionized states that are localized on thymine the dominant contribution to the IE reduction is the electrostatic interaction between the delocalized positive charge on thymine and the dipole moment of the water molecule.

  16. High-energy ionization by relativistically intense laser pulses

    NASA Astrophysics Data System (ADS)

    Kamiński, J. Z.; Cajiao Vélez, F.; Krajewska, K.

    2017-07-01

    High-energy ionization by relativistically intense, 30~\\text{fs} laser pulses is investigated within the relativistic strong-field approximation. It is shown that the momentum distribution of photoelectrons is focused around a spiral, the analytical form of which is derived from the saddle-point analysis of probability amplitudes. The geometry of this spiral allows one to clearly interpret the exact numerical results of the ionization probability distributions and to identify the photoelectron momentum domains in which the interference- and the interference-free patterns are observed. It is also demonstrated that attosecond single-electron wave packets can be created in this process. Thus, it opens new research opportunities for the four-dimensional electron diffraction experiments, which can be conducted in large-scale laser facilities such as ELI or XCELS.

  17. IONS (ANURADHA): Ionization states of low energy cosmic rays

    NASA Technical Reports Server (NTRS)

    Biswas, S.; Chakraborti, R.; Cowsik, R.; Durgaprasad, N.; Kajarekar, P. J.; Singh, R. K.; Vahia, M. N.; Yadav, J. S.; Dutt, N.; Goswami, J. N.

    1987-01-01

    IONS (ANURADHA), the experimental payload designed specifically to determine the ionization states, flux, composition, energy spectra and arrival directions of low energy (10 to 100 MeV/amu) anomalous cosmic ray ions of helium to iron in near-Earth space, had a highly successful flight and operation Spacelab-3 mission. The experiment combines the accuracy of a highly sensitive CR-39 nuclear track detector with active components included in the payload to achieve the experimental objectives. Post-flight analysis of detector calibration pieces placed within the payload indicated no measurable changes in detector response due to its exposure in spacelab environment. Nuclear tracks produced by alpha-particles, oxygen group and Fe ions in low energy anomalous cosmic rays were identified. It is calculated that the main detector has recorded high quality events of about 10,000 alpha-particles and similar number of oxygen group and heavier ions of low energy cosmic rays.

  18. Efficient Ionization Investigation for Flow Control and Energy Extraction

    NASA Technical Reports Server (NTRS)

    Schneider, Steven J.; Kamhawi, Hani; Blankson, Isaiah M.

    2009-01-01

    Nonequilibrium ionization of air by nonthermal means is explored for hypersonic vehicle applications. The method selected for evaluation generates a weakly ionized plasma using pulsed nanosecond, high-voltage discharges sustained by a lower dc voltage. These discharges promise to provide a means of energizing and sustaining electrons in the air while maintaining a nearly constant ion/neutral molecule temperature. This paper explores the use of short approx.5 nsec, high-voltage approx.12 to 22 kV, repetitive (40 to 100 kHz) discharges in generating a weakly ionized gas sustained by a 1 kV dc voltage in dry air at pressures from 10 to 80 torr. Demonstrated lifetimes of the sustainer discharge current approx.10 to 25 msec are over three orders of magnitude longer than the 5 nsec pulse that generates the electrons. This life is adequate for many high speed flows, enabling the possibility of exploiting weakly ionized plasma phenomena in flow-fields such as those in hypersonic inlets, combustors, and nozzles. Results to date are obtained in a volume of plasma between electrodes in a bell jar. The buildup and decay of the visible emission from the pulser excited air is photographed on an ICCD camera with nanosecond resolution and the time constants for visible emission decay are observed to be between 10 to 15 nsec decreasing as pressure increases. The application of the sustainer voltage does not change the visible emission decay time constant. Energy consumption as indicated by power output from the power supplies is 194 to 669 W depending on pulse repetition rate.

  19. Ion energies in high power impulse magnetron sputtering with and without localized ionization zones

    SciTech Connect

    Yang, Yuchen; Tanaka, Koichi; Liu, Jason; Anders, André

    2015-03-23

    High speed imaging of high power impulse magnetron sputtering discharges has revealed that ionization is localized in moving ionization zones but localization disappears at high currents for high yield targets. This offers an opportunity to study the effect ionization zones have on ion energies. We measure that ions have generally higher energies when ionization zones are present, supporting the concept that these zones are associated with moving potential humps. We propose that the disappearance of ionization zones is caused by an increased supply of atoms from the target which cools electrons and reduces depletion of atoms to be ionized.

  20. High field – low energy muon ionization cooling channel

    DOE PAGES

    Sayed, Hisham Kamal; Palmer, Robert B.; Neuffer, David

    2015-09-04

    Muon beams are generated with large transverse and longitudinal emittances. In order to achieve the low emittances required by a muon collider, within the short lifetime of the muons, ionization cooling is required. Cooling schemes have been developed to reduce the muon beam 6D emittances to ≈ 300 μm–rad in transverse and ≈ 1–1.5 mm in longitudinal dimensions. The transverse emittance has to be further reduced to ≈ 50–25 μm–rad with an upper limit on the longitudinal emittance of ≈ 76 mm in order to meet the high-energy muon collider luminosity requirements. Earlier studies of the transverse cooling of lowmore » energy muon beams in high field magnets showed a promising performance, but did not include transverse or longitudinal matching between the stages. In this study we present the first complete design of the high field-low energy ionization cooling channel with transverse and longitudinal matching. The channel design was based on strong focusing solenoids with fields of 25–30 T and low momentum muon beam starting at 135 MeV/c and gradually decreasing. The cooling channel design presented here is the first to reach ≈ 50 micron scale emittance beam. As a result, we present the channel’s optimized design parameters including the focusing solenoid fields, absorber parameters and the transverse and longitudinal matching.« less

  1. Energy and charge transfer in ionized argon coated water clusters.

    PubMed

    Kočišek, J; Lengyel, J; Fárník, M; Slavíček, P

    2013-12-07

    We investigate the electron ionization of clusters generated in mixed Ar-water expansions. The electron energy dependent ion yields reveal the neutral cluster composition and structure: water clusters fully covered with the Ar solvation shell are formed under certain expansion conditions. The argon atoms shield the embedded (H2O)n clusters resulting in the ionization threshold above ≈15 eV for all fragments. The argon atoms also mediate more complex reactions in the clusters: e.g., the charge transfer between Ar(+) and water occurs above the threshold; at higher electron energies above ~28 eV, an excitonic transfer process between Ar(+)* and water opens leading to new products Ar(n)H(+) and (H2O)(n)H(+). On the other hand, the excitonic transfer from the neutral Ar* state at lower energies is not observed although this resonant process was demonstrated previously in a photoionization experiment. Doubly charged fragments (H2O)(n)H2(2+) and (H2O)(n)(2+) ions are observed and Intermolecular Coulomb decay (ICD) processes are invoked to explain their thresholds. The Coulomb explosion of the doubly charged cluster formed within the ICD process is prevented by the stabilization effect of the argon solvent.

  2. Energy and charge transfer in ionized argon coated water clusters

    SciTech Connect

    Kočišek, J. E-mail: michal.farnik@jh-inst.cas.cz Lengyel, J.; Fárník, M. E-mail: michal.farnik@jh-inst.cas.cz; Slavíček, P. E-mail: michal.farnik@jh-inst.cas.cz

    2013-12-07

    We investigate the electron ionization of clusters generated in mixed Ar-water expansions. The electron energy dependent ion yields reveal the neutral cluster composition and structure: water clusters fully covered with the Ar solvation shell are formed under certain expansion conditions. The argon atoms shield the embedded (H{sub 2}O){sub n} clusters resulting in the ionization threshold above ≈15 eV for all fragments. The argon atoms also mediate more complex reactions in the clusters: e.g., the charge transfer between Ar{sup +} and water occurs above the threshold; at higher electron energies above ∼28 eV, an excitonic transfer process between Ar{sup +}* and water opens leading to new products Ar{sub n}H{sup +} and (H{sub 2}O){sub n}H{sup +}. On the other hand, the excitonic transfer from the neutral Ar* state at lower energies is not observed although this resonant process was demonstrated previously in a photoionization experiment. Doubly charged fragments (H{sub 2}O){sub n}H{sub 2}{sup 2+} and (H{sub 2}O){sub n}{sup 2+} ions are observed and Intermolecular Coulomb decay (ICD) processes are invoked to explain their thresholds. The Coulomb explosion of the doubly charged cluster formed within the ICD process is prevented by the stabilization effect of the argon solvent.

  3. DNA lesion can facilitate base ionization: vertical ionization energies of aqueous 8-oxoguanine and its nucleoside and nucleotide.

    PubMed

    Palivec, Vladimír; Pluhařová, Eva; Unger, Isaak; Winter, Bernd; Jungwirth, Pavel

    2014-12-04

    8-Oxoguanine is one of the key products of indirect radiation damage to DNA by reactive oxygen species. Here, we describe ionization of this damaged nucleobase and the corresponding nucleoside and nucleotide in aqueous phase, modeled by the nonequilibrium polarizable continuum model, establishing their lowest vertical ionization energies of 6.8-7.0 eV. We thus confirm that 8-oxoguanine has even lower ionization energy than the parental guanine, which is the canonical nucleobase with the lowest ionization energy. Therefore, it can act as a trap for the cationic hole formed by ionizing radiation and thus protect DNA from further radiation damage. We also model using time-dependent density functional theory and measure by liquid jet photoelectron spectroscopy the valence photoelectron spectrum of 8-oxoguanine in water. We show that the calculated higher lying ionization states match well the experiment which, however, is not sensitive enough to capture the electron signal corresponding to the lowest ionization process due to the low solubility of 8-oxoguanine in water.

  4. The excitation energies and term energies of the excited states 1s2ns (n=3,4,5) and 1s2nf (n=4,5) of lithium-like systems of Z=11-20

    NASA Astrophysics Data System (ADS)

    Ge, Zi-Ming; Wang, Zhi-Wen; Zhou, Ya-Jun; He, Li-Ming; Liu, Guo-Guang

    2003-05-01

    In this paper, the full-core plus correlation (FCPC) and the Ritz method is extended to calculate the non-relativistic energies of 1s2ns (n=3,4,5) and 1s2nf (n=4,5) states and the wavefunctions of the lithium-like systems from Z=11-20. The mass-polarization and the relativistic correction including the kinetic-energy correction, the Darwin term, the electron-electron contact term and the orbit-orbit interaction are evaluated perturbatively as the first-order correction. The contribution from quantum electrodynamic is also included by using the effective nuclear charge formula. The excited energies, the term-energy and fine structure, are given and compared with the other theoretical calculation and experimental results. It is shown that the correlative wave in the FCPC method embodies well the strong correlation between the 1s2 core and the valence electron.

  5. Electronic structure and spectroscopy of nucleic acid bases: Ionization energies, ionization-induced structural changes, and photoelectron spectra

    SciTech Connect

    Bravaya, Ksenia B.; Kostko, Oleg; Dolgikh, Stanislav; Landau, Arie; Ahmed, Musahid; Krylov, Anna I.

    2010-08-02

    We report high-level ab initio calculations and single-photon ionization mass spectrometry study of ionization of adenine (A), thymine (T), cytosine (C) and guanine (G). For thymine and adenine, only the lowest-energy tautomers were considered, whereas for cytosine and guanine we characterized five lowest-energy tautomeric forms. The first adiabatic and several vertical ionization energies were computed using equation-of-motion coupled-cluster method for ionization potentials with single and double substitutions. Equilibrium structures of the cationic ground states were characterized by DFT with the {omega}B97X-D functional. The ionization-induced geometry changes of the bases are consistent with the shapes of the corresponding molecular orbitals. For the lowest-energy tautomers, the magnitude of the structural relaxation decreases in the following series G > C > A > T, the respective relaxation energies being 0.41, 0.32, 0.25 and 0.20 eV. The computed adiabatic ionization energies (8.13, 8.89, 8.51-8.67 and 7.75-7.87 eV for A,T,C and G, respectively) agree well with the onsets of the photoionization efficiency (PIE) curves (8.20 {+-} 0.05, 8.95 {+-} 0.05, 8.60 {+-} 0.05 and 7.75 {+-} 0.05 eV). Vibrational progressions for the S{sub 0}-D{sub 0} vibronic bands computed within double-harmonic approximation with Duschinsky rotations are compared with previously reported experimental photoelectron spectra.

  6. Extreme ultraviolet ionization of pure He nanodroplets: Mass-correlated photoelectron imaging, Penning ionization, and electron energy-loss spectra

    SciTech Connect

    Buchta, D.; Stienkemeier, F.; Mudrich, M.; Krishnan, S. R.; Moshammer, R.; Brauer, N. B.; Drabbels, M.; O’Keeffe, P.; Coreno, M.; Devetta, M.; Di Fraia, M.; Callegari, C.; Richter, R.; Prince, K. C.; Ullrich, J.

    2013-08-28

    The ionization dynamics of pure He nanodroplets irradiated by Extreme ultraviolet radiation is studied using Velocity-Map Imaging PhotoElectron-PhotoIon COincidence spectroscopy. We present photoelectron energy spectra and angular distributions measured in coincidence with the most abundant ions He{sup +}, He{sub 2}{sup +}, and He{sub 3}{sup +}. 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 observe inelastic collisions of photoelectrons with the surrounding He atoms in the droplets.

  7. Hylleraas-configuration-interaction nonrelativistic energies for the {sup 1}S ground states of the beryllium isoelectronic sequence

    SciTech Connect

    Sims, James S.; Hagstrom, Stanley A.

    2014-06-14

    In a previous work, Sims and Hagstrom [“Hylleraas-configuration-interaction study of the 1 {sup 1}S ground state of neutral beryllium,” Phys. Rev. A 83, 032518 (2011)] reported Hylleraas-configuration-interaction (Hy-CI) method variational calculations for the {sup 1}S ground state of neutral beryllium with an estimated accuracy of a tenth of a microhartree. In this work, the calculations have been extended to higher accuracy and, by simple scaling of the orbital exponents, to the entire Be 2 {sup 1}S isoelectronic sequence. The best nonrelativistic energies for Be, B{sup +}, and C{sup ++} obtained are −14.6673 5649 269, −24.3488 8446 36, and −36.5348 5236 25 hartree, respectively. Except for Be, all computed nonrelativistic energies are superior to the known reference energies for these states.

  8. Spectrum and energy levels of quadruply-ionized molybdenum (Mo V)

    NASA Astrophysics Data System (ADS)

    Reader, Joseph; Tauheed, Ahmad

    2015-07-01

    The spectrum of quadruply-ionized molybdenum Mo V was observed from 200 to 4700 Å with sliding spark discharges on 10.7 m normal- and grazing-incidence spectrographs. The existing analyses of this spectrum (Tauheed et al 1985 Phys. Scr. 31 369; Cabeza et al 1986 Phys. Scr. 34 223) were extended to include the 5s2, 5p2, 5s5d, 5s6s, 4d5f, and 4d5g configurations as well as the missing 3H6 level of 4d4f and about 75 levels of the core-excited configuration 4p54d3. The values of the 4d5d 1S0, 5s5p 1P1, and 4d6p 3P0 levels were revised. There are now about 900 lines classified as transitions between 66 even parity and 191 odd parity energy levels. Of these, about 600 lines and 130 levels are new. From the optimized energy level values, Ritz-type wavelengths were determined for about 380 lines, with uncertainties varying from 0.0003 to 0.002 Å. The observed configurations were theoretically interpreted by means of Hartree-Fock calculations and least-squares fits of the energy parameters to the observed levels. The fitted parameters were used to calculate oscillator strengths for all classified lines. A few unclassified lines and undesignated levels are also given. An improved value for the ionization energy was obtained by combining the observed energy of the 4d5g configuration with an ab initio calculation of its term value. The adopted value is 438 900 ± 150 cm-1 (54.417 ± 0.019 eV).

  9. Xbp1s in Pomc neurons connects ER stress with energy balance and glucose homeostasis

    USDA-ARS?s Scientific Manuscript database

    The molecular mechanisms underlying neuronal leptin and insulin resistance in obesity and diabetes remain unclear. Here we show that induction ofthe unfolded protein response transcription factor spliced X-box binding protein 1(Xbp1s) in pro-opio-melanocortin (Pomc) neurons alone is sufficient to pr...

  10. Reverse Energy Cascade in Turbulent Weakly Ionized Plasmas

    NASA Technical Reports Server (NTRS)

    Williams, Kyron; Appartaim, R.; Belay, K.; Johnson, J. A., III

    1998-01-01

    For systems far from equilibrium, the neglect of a role for viscous effects in turbulence may be generally inappropriate when the relaxation time for the molecular process approaches the local flow time (Orou et al. (1996)). Furthermore, for stationary collisional plasmas, the conventional Reynolds number is irrelevant under circumstances where the standard features of turbulence in ordinary gases are observed in the plasma (Johnson et al. (1987)). The current theoretical understanding of these turbulent phenomenon is particularly inadequate for turbulence associated with ionizing shock waves; generally speaking, thermodynamic, acoustic and pressure fluctuations are all seen as amplified across the shock wave followed by a dramatic decay (relaminarization) usually attributed to a lack of importance of viscosity in the turbulent regions. This decay would be accelerated when the flow speed is also reduced due to the importance usually given to the conventional Reynolds number (which is directly proportional to velocity) as a quality of turbulence index. However, evidence supporting this consensus is lacking. By contrast, recent evidence of vanishing triple correlations form De Silva et al. (1996) provides strong support for early theoretical speculation of inherently molecular effects in macroscopic turbulence in Tsuge (1974). This specifically suggests that the role of compressive effects ordinarily associated with the shock wave could be significantly muted by the existence of a strongly turbulent local environment. There is also more recent theoretical speculation (Frisch et al. (1984)) of an inherently and previously unsuspected non-dissipative nature to turbulence, with energy conservation being nurtured by reverse energy cascades in the turbulent fluctuation spectra. Furthermore, the role which might be played by fluctuations on quantum mechanical phenomena and variations in molecular parameters is completely unknown, especially of the sort which might be found

  11. Reverse Energy Cascade in Turbulent Weakly Ionized Plasmas

    NASA Technical Reports Server (NTRS)

    Williams, Kyron; Appartaim, R.; Belay, K.; Johnson, J. A., III

    1998-01-01

    For systems far from equilibrium, the neglect of a role for viscous effects in turbulence may be generally inappropriate when the relaxation time for the molecular process approaches the local flow time (Orou et al. (1996)). Furthermore, for stationary collisional plasmas, the conventional Reynolds number is irrelevant under circumstances where the standard features of turbulence in ordinary gases are observed in the plasma (Johnson et al. (1987)). The current theoretical understanding of these turbulent phenomenon is particularly inadequate for turbulence associated with ionizing shock waves; generally speaking, thermodynamic, acoustic and pressure fluctuations are all seen as amplified across the shock wave followed by a dramatic decay (relaminarization) usually attributed to a lack of importance of viscosity in the turbulent regions. This decay would be accelerated when the flow speed is also reduced due to the importance usually given to the conventional Reynolds number (which is directly proportional to velocity) as a quality of turbulence index. However, evidence supporting this consensus is lacking. By contrast, recent evidence of vanishing triple correlations form De Silva et al. (1996) provides strong support for early theoretical speculation of inherently molecular effects in macroscopic turbulence in Tsuge (1974). This specifically suggests that the role of compressive effects ordinarily associated with the shock wave could be significantly muted by the existence of a strongly turbulent local environment. There is also more recent theoretical speculation (Frisch et al. (1984)) of an inherently and previously unsuspected non-dissipative nature to turbulence, with energy conservation being nurtured by reverse energy cascades in the turbulent fluctuation spectra. Furthermore, the role which might be played by fluctuations on quantum mechanical phenomena and variations in molecular parameters is completely unknown, especially of the sort which might be found

  12. Modeling heavy ion ionization energy loss at low and intermediate energies

    SciTech Connect

    Rakhno, I.L.; /Fermilab

    2009-11-01

    The needs of contemporary accelerator and space projects led to significant efforts made to include description of heavy ion interactions with matter in general-purpose Monte Carlo codes. This paper deals with an updated model of heavy ion ionization energy loss developed previously for the MARS code. The model agrees well with experimental data for various projectiles and targets including super-heavy ions in low-Z media.

  13. Decomposition reaction of the veterinary antibiotic ciprofloxacin using electron ionizing energy.

    PubMed

    Cho, Jae Young; Chung, Byung Yeoup; Lee, Kyeong-Bo; Lee, Geon-Hwi; Hwang, Seon Ah

    2014-12-01

    The application of electron ionizing energy for degrading veterinary antibiotic ciprofloxacin (CFX) in aqueous solution was elucidated. The degradation efficiency of CFX after irradiation with electron ionizing energy was 38% at 1 kGy, 80% at 5kGy, and 97% at 10 kGy. Total organic carbon of CFX in aqueous solution after irradiation with electron ionizing energy decreased 2% at 1 kGy, 18% at 5 kGy, and 53% at 10 kGy. The CFX degradation products after irradiation with electron ionizing energy were CFX1 ([M+H] m/z 330), CFX2 ([M+H] m/z 314), and CFX3 ([M+H] m/z 263). CFX1 had an F atom substituted with OH and CFX2 was expected to originate from CFX via loss of F or H2O. CFX3 was expected to originate from CFX via loss of the piperazynilic ring. Among the several radicals, hydrate electron (eaq(-)) is expected to play an important role in degradation of veterinary antibiotic during irradiation with electron ionizing energy. The toxicity of the degraded products formed during irradiation with electron ionizing energy was evaluated using microbes such as Escherichia coli, Pseudomonas putida, and Bacillus subtilis, and the results revealed that the toxicity decreased with irradiation. These results demonstrate that irradiation technology using electron ionizing energy is an effective was to remove veterinary antibiotics from an aquatic ecosystem.

  14. Ab initio study of thiol aqueous phase ionization energies. Methyl mercaptan and cysteamine

    SciTech Connect

    Colson, A.O.; Sevilla, M.D. )

    1994-10-13

    The ionization energies of two thiol model compounds (methyl mercaptan and cysteamine) are calculated at the ROHF/6-31G* level to aid our understanding of the mechanisms involved in DNA radioprotection. Methyl mercaptan, the thiolate anion, and its trihydrated form are fully geometry optimized. The resulting gas-phase Koopmans ionization energies are 9.68, 1.67, and 3.63 eV, respectively. The ionization energy for the solvated methylthiolate anion, CH[sub 3]S[sup [minus

  15. One-photon mass-analyzed threshold ionization (MATI) spectroscopy of pyridine: Determination of accurate ionization energy and cationic structure

    SciTech Connect

    Lee, Yu Ran; Kang, Do Won; Kim, Hong Lae E-mail: hlkim@kangwon.ac.kr; Kwon, Chan Ho E-mail: hlkim@kangwon.ac.kr

    2014-11-07

    Ionization energies and cationic structures of pyridine were intensively investigated utilizing one-photon mass-analyzed threshold ionization (MATI) spectroscopy with vacuum ultraviolet radiation generated by four-wave difference frequency mixing in Kr. The present one-photon high-resolution MATI spectrum of pyridine demonstrated a much finer and richer vibrational structure than that of the previously reported two-photon MATI spectrum. From the MATI spectrum and photoionization efficiency curve, the accurate ionization energy of the ionic ground state of pyridine was confidently determined to be 73 570 ± 6 cm{sup −1} (9.1215 ± 0.0007 eV). The observed spectrum was almost completely assigned by utilizing Franck-Condon factors and vibrational frequencies calculated through adjustments of the geometrical parameters of cationic pyridine at the B3LYP/cc-pVTZ level. A unique feature unveiled through rigorous analysis was the prominent progression of the 10 vibrational mode, which corresponds to in-plane ring bending, and the combination of other totally symmetric fundamentals with the ring bending overtones, which contribute to the geometrical change upon ionization. Notably, the remaining peaks originate from the upper electronic state ({sup 2}A{sub 2}), as predicted by high-resolution photoelectron spectroscopy studies and symmetry-adapted cluster configuration interaction calculations. Based on the quantitatively good agreement between the experimental and calculated results, it was concluded that upon ionization the pyridine cation in the ground electronic state should have a planar structure of C{sub 2v} symmetry through the C-N axis.

  16. One-photon mass-analyzed threshold ionization (MATI) spectroscopy of pyridine: Determination of accurate ionization energy and cationic structure

    NASA Astrophysics Data System (ADS)

    Lee, Yu Ran; Kang, Do Won; Kim, Hong Lae; Kwon, Chan Ho

    2014-11-01

    Ionization energies and cationic structures of pyridine were intensively investigated utilizing one-photon mass-analyzed threshold ionization (MATI) spectroscopy with vacuum ultraviolet radiation generated by four-wave difference frequency mixing in Kr. The present one-photon high-resolution MATI spectrum of pyridine demonstrated a much finer and richer vibrational structure than that of the previously reported two-photon MATI spectrum. From the MATI spectrum and photoionization efficiency curve, the accurate ionization energy of the ionic ground state of pyridine was confidently determined to be 73 570 ± 6 cm-1 (9.1215 ± 0.0007 eV). The observed spectrum was almost completely assigned by utilizing Franck-Condon factors and vibrational frequencies calculated through adjustments of the geometrical parameters of cationic pyridine at the B3LYP/cc-pVTZ level. A unique feature unveiled through rigorous analysis was the prominent progression of the 10 vibrational mode, which corresponds to in-plane ring bending, and the combination of other totally symmetric fundamentals with the ring bending overtones, which contribute to the geometrical change upon ionization. Notably, the remaining peaks originate from the upper electronic state (2A2), as predicted by high-resolution photoelectron spectroscopy studies and symmetry-adapted cluster configuration interaction calculations. Based on the quantitatively good agreement between the experimental and calculated results, it was concluded that upon ionization the pyridine cation in the ground electronic state should have a planar structure of C2v symmetry through the C-N axis.

  17. Electron-nuclear energy sharing in above-threshold multiphoton dissociative ionization of H2.

    PubMed

    Wu, J; Kunitski, M; Pitzer, M; Trinter, F; Schmidt, L Ph H; Jahnke, T; Magrakvelidze, M; Madsen, C B; Madsen, L B; Thumm, U; Dörner, R

    2013-07-12

    We report experimental observation of the energy sharing between electron and nuclei in above-threshold multiphoton dissociative ionization of H2 by strong laser fields. The absorbed photon energy is shared between the ejected electron and nuclei in a correlated fashion, resulting in multiple diagonal lines in their joint energy spectrum governed by the energy conservation of all fragment particles.

  18. Effect of rescattering potential on the high-energy above-threshold ionization of a model-H atom

    NASA Astrophysics Data System (ADS)

    Chen, J.-H.; Wang, G.-L.; Zhang, Z.-R.; Zhao, S.-F.

    2017-01-01

    The high-energy above-threshold ionization of a model-H atom (with 1s state and the same binding energy as H atom) in a few-cycle laser pulse is investigated by using the improved strong-field approximation (ISFA), where the spherical shell potential is used as the rescattering potential. The results obtained from numerically solving time-dependent Schrödinger equation(TDSE) are regarded as the benchmark results. Our results show that the energy distributions in high-energy region obtained from ISFA calculations using the spherical shell potential may either match or be better than those from ISFA using Yukawa potential and zero-range potential in the laser with wavelengths of 800 and 1200 nm. In addition, the influence of the rescattering potential on the density of probability at different ejection angles is also discussed in this paper.

  19. High resolution gas ionization chamber in proportional mode for low energy applications

    NASA Astrophysics Data System (ADS)

    Müller, Arnold Milenko; Döbeli, Max; Synal, Hans-Arno

    2017-09-01

    The operation of the ETH gas ionization detector as a proportional chamber, where a secondary ionization avalanche is initiated between the Frisch grid and anode, was investigated for ions covering the mass range from H to 127I. By amplifying the detector electron signal through secondary ionization, the limitations due to the sensitivity of the detector electronics are minimized. It could be demonstrated that in the energy range of a few hundreds of keV and below a proportional chamber clearly outperforms a conventionally used gas ionization detector. Protons below 10 keV were measured with a resolution better than 1.4 keV and a good linearity of the particle energy and detector signal was found in the energy range between 50 and 1000 keV. At higher energies almost no difference in resolution for the two operation modes could be found.

  20. Generalized average local ionization energy and its representations in terms of Dyson and energy orbitals.

    PubMed

    Kohut, Sviataslau V; Cuevas-Saavedra, Rogelio; Staroverov, Viktor N

    2016-08-21

    Ryabinkin and Staroverov [J. Chem. Phys. 141, 084107 (2014)] extended the concept of average local ionization energy (ALIE) to correlated wavefunctions by defining the generalized ALIE as Ī(r)=-∑jλj|fj(r)|(2)/ρ(r), where λj are the eigenvalues of the generalized Fock operator and fj(r) are the corresponding eigenfunctions (energy orbitals). Here we show that one can equivalently express the generalized ALIE as Ī(r)=∑kIk|dk(r)|(2)/ρ(r), where Ik are single-electron removal energies and dk(r) are the corresponding Dyson orbitals. The two expressions for Ī(r) emphasize different physical interpretations of this quantity; their equivalence enables one to calculate the ALIE at any level of ab initio theory without generating the computationally expensive Dyson orbitals.

  1. Ionization energies of argon clusters: A combined experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Echt, O.; Fiegele, T.; Rümmele, M.; Probst, M.; Matt-Leubner, S.; Urban, J.; Mach, P.; Leszczynski, J.; Scheier, P.; Märk, T. D.

    2005-08-01

    We have measured appearance energies of Arn+,n⩽30, by electron impact of gas phase clusters. Quantum-chemical calculations have been performed to determine the adiabatic and vertical ionization energies of argon clusters up to n =4 and 6, respectively. The experimental appearance energy of the dimer ion approaches, under suitable cluster source conditions, the adiabatic ionization energy. The agreement with values obtained by photoionization and threshold photoelectron-photoion coincidence (TPEPICO) spectra demonstrates that autoionizing Rydberg states are accessible by electron impact. Appearance energies of larger clusters, though, exceed the TPEPICO values by about 0.5 eV.

  2. Photon Energy Deposition in Strong-Field Single Ionization of Multielectron Molecules.

    PubMed

    Zhang, Wenbin; Li, Zhichao; Lu, Peifen; Gong, Xiaochun; Song, Qiying; Ji, Qinying; Lin, Kang; Ma, Junyang; He, Feng; Zeng, Heping; Wu, Jian

    2016-09-02

    Molecules exposed to strong laser fields may coherently absorb multiple photons and deposit the energy into electrons and nuclei, triggering the succeeding dynamics as the primary stage of the light-molecule interaction. We experimentally explore the electron-nuclear sharing of the absorbed photon energy in above-threshold multiphoton single ionization of multielectron molecules. Using CO as a prototype, vibrational and orbital resolved electron-nuclear sharing of the photon energy is observed. Different from the simplest one- or two-electron systems, the participation of the multiple orbitals and the coupling of various electronic states in the strong-field ionization and dissociation processes alter the photon energy deposition dynamics of the multielectron molecule. The population of numerous vibrational states of the molecular cation as the energy reservoir in the ionization process plays an important role in photon energy sharing between the emitted electron and the nuclear fragments.

  3. Nanocluster ionization energies and work function of aluminum, and their temperature dependence

    SciTech Connect

    Halder, Avik; Kresin, Vitaly V.

    2015-10-28

    Ionization threshold energies of Al{sub n} (n = 32-95) nanoclusters are determined by laser ionization of free neutral metal clusters thermalized to several temperatures in the range from 65 K to 230 K. The photoion yield curves of cold clusters follow a quadratic energy dependence above threshold, in agreement with the Fowler law of surface photoemission. Accurate data collection and analysis procedures make it possible to resolve very small (few parts in a thousand) temperature-induced shifts in the ionization energies. Extrapolation of the data to the bulk limit enables a determination of the thermal shift of the polycrystalline metal work function, found to be in excellent agreement with theoretical prediction based on the influence of thermal expansion. Small clusters display somewhat larger thermal shifts, reflecting their greater susceptibility to thermal expansion. Ionization studies of free size-resolved nanoclusters facilitate understanding of the interplay of surface, electronic, and lattice properties under contamination-free conditions.

  4. Ionization energies of aqueous nucleic acids: photoelectron spectroscopy of pyrimidine nucleosides and ab initio calculations.

    PubMed

    Slavícek, Petr; Winter, Bernd; Faubel, Manfred; Bradforth, Stephen E; Jungwirth, Pavel

    2009-05-13

    Vertical ionization energies of the nucleosides cytidine and deoxythymidine in water, the lowest ones amounting in both cases to 8.3 eV, are obtained from photoelectron spectroscopy measurements in aqueous microjets. Ab initio calculations employing a nonequilibrium polarizable continuum model quantitatively reproduce the experimental spectra and provide molecular interpretation of the individual peaks of the photoelectron spectrum, showing also that lowest ionization originates from the base. Comparison of calculated vertical ionization potentials of pyrimidine bases, nucleosides, and nucleotides in water and in the gas phase underlines the dramatic effect of bulk hydration on the electronic structure. In the gas phase, the presence of sugar and, in particular, of phosphate has a strong effect on the energetics of ionization of the base. Upon bulk hydration, the ionization potential of the base in contrast becomes rather insensitive to the presence of the sugar and phosphate, which indicates a remarkable screening ability of the aqueous solvent. Accurate aqueous-phase vertical ionization potentials provide a significant improvement to the corrected gas-phase values used in the literature and represent important information in assessing the threshold energies for photooxidation and oxidation free energies of solvent-exposed DNA components. Likewise, such energetic data should allow improved assessment of delocalization and charge-hopping mechanisms in DNA ionized by radiation.

  5. Calculations of photoelectron momentum distributions and energy spectra at strong-field multiphoton ionization of sodium

    NASA Astrophysics Data System (ADS)

    Bunjac, Andrej; Popović, Duška B.; Simonović, Nenad S.

    2017-08-01

    Multiphoton ionization of sodium by a femtosecond laser pulse of 760 nm wavelength and different peak intensities is studied by inspecting the photoelectron angular and momentum distributions and the energy spectra. For this purpose a single-electron model of the atom interacting with the electromagnetic field is used, and the distributions are determined by calculating the evolution of the electron wave function. Beside the most prominent distribution maxima related to the four-photon ionization, the five-photon (above-threshold) ionization peaks are observed. Substructures in the main (nonresonant) maximum in the photoelectron spectra at the four-photon ionization are related to the resonantly enhanced multiphoton ionization via intermediate 4 s, 4 f, 5 p, 5 f and 6 p states.

  6. Treatment of Electronic Energy Level Transition and Ionization Following the Particle-Based Chemistry Model

    NASA Technical Reports Server (NTRS)

    Liechty, Derek S.; Lewis, Mark

    2010-01-01

    A new method of treating electronic energy level transitions as well as linking ionization to electronic energy levels is proposed following the particle-based chemistry model of Bird. Although the use of electronic energy levels and ionization reactions in DSMC are not new ideas, the current method of selecting what level to transition to, how to reproduce transition rates, and the linking of the electronic energy levels to ionization are, to the author s knowledge, novel concepts. The resulting equilibrium temperatures are shown to remain constant, and the electronic energy level distributions are shown to reproduce the Boltzmann distribution. The electronic energy level transition rates and ionization rates due to electron impacts are shown to reproduce theoretical and measured rates. The rates due to heavy particle impacts, while not as favorable as the electron impact rates, compare favorably to values from the literature. Thus, these new extensions to the particle-based chemistry model of Bird provide an accurate method for predicting electronic energy level transition and ionization rates in gases.

  7. Propensity for distinguishing two free electrons with equal energies in electron-impact ionization of helium

    NASA Astrophysics Data System (ADS)

    Ren, Xueguang; Senftleben, Arne; Pflüger, Thomas; Bartschat, Klaus; Zatsarinny, Oleg; Berakdar, Jamal; Colgan, James; Pindzola, Michael S.; Bray, Igor; Fursa, Dmitry V.; Dorn, Alexander

    2015-11-01

    We report a combined experimental and theoretical study on the electron-impact ionization of helium at E0=70.6 eV and equal energy sharing of the two outgoing electrons (E1=E2=23 eV ), where a double-peak or dip structure in the binary region of the triple differential cross section is observed. The experimental cross sections are compared with results from convergent close-coupling (CCC), B -spline R-matrix-with-pseudostates (BSR), and time-dependent close-coupling (TDCC) calculations, as well as predictions from the dynamic screening three-Coulomb (DS3C) theory. Excellent agreement is obtained between experiment and the nonperturbative CCC, BSR, and TDCC theories, and good agreement is also found for the DS3C model. The data are further analyzed regarding contributions in particular coupling schemes for the spins of either the two outgoing electrons or one of the outgoing electrons and the 1 s electron remaining in the residual ion. While both coupling schemes can be used to explain the observed double-peak structure in the cross section, the second one allows for the isolation of the exchange contribution between the incident projectile and the target. For different observation angles of the two outgoing electrons, we interpret the results as a propensity for distinguishing these two electrons—one being more likely the incident projectile and the other one being more likely ejected from the target.

  8. Electron transfer and ionization in collisions between H{sup +}, He{sup 2+}, Li{sup 3+}, Be{sup 4+}, B{sup 5+}, C{sup 6+}, N{sup 7+} ions and target C{sup 5+}(1s) ions studied using a Sturmian basis

    SciTech Connect

    Winter, T.G.

    1997-10-01

    Cross sections have been determined for electron transfer and ionization in collisions between H{sup +}, He{sup 2+}, Li{sup 3+}, Be{sup 4+}, B{sup 5+}, C{sup 6+}, N{sup 7+} ions and target C{sup 5+}(1s) ions for projectile energies 125{endash}1000 keV/amu using a coupled-Sturmian-pseudostate approach [Phys. Rev. A {bold 35}, 3799 (1987)]. A comparison is made with results using simpler approaches, and rules for scaling with the projectile nuclear charge are considered. Except for H{sup +}, the results for electron transfer to the ground state are estimated to be converged to 1{percent}; for ionization, the convergence is probably to 10{endash}20thinsp{percent}. {copyright} {ital 1997} {ital The American Physical Society}

  9. Modeling ionization and recombination from low energy nuclear recoils in liquid argon

    SciTech Connect

    Foxe, Michael P.; Hagmann, Chris; Jovanovic, Igor; Bernstein, A.; Joshi, T.; Kazkaz, K.; Mozin, Vladimir V.; Pereverzev, S. V.; Sangiorgio, Samuele; Sorensen, Peter F.

    2015-09-01

    Coherent neutrino-nucleus scattering (CNNS) is an as-yet undetected, flavor-independent neutrino interaction predicted by the Standard Model. CNNS is a flavor-blind interaction, which offers potential benefits for its use in nonproliferation (nuclear reactor monitoring) and astrophysics (supernova and solar neutrinos) applications. One challenge with detecting CNNS is the low energy deposition associated with a typical CNNS nuclear recoil. In addition, nuclear recoils are predicted to result in lower ionization yields than those produced by electron recoils of the same energy. This ratio of nuclear- and electron-induced ionization, known as the nuclear quenching factor, is unknown at energies typical for CNNS interactions in liquid xenon (LXe) and liquid argon (LAr), detector media being considered for CNNS detection. While there have been recent measurements [1] of the ionization yield from nuclear recoils in LAr, there is no universal model for nuclear quenching and ionization yield. For this reason, a Monte Carlo simulation has been developed to predict the ionization yield at sub-10 keV energies. The local ionization yield of a recoiling atom in the medium is calculated first. The ejected electrons are subsequently tracked in the electric field resulting from both the local electric charges and the externally applied drift field. The dependence of the ionization yield on the drift electric field is obtained by combining the calculated ionization yield for the initial collision cascade with the electron escape probability. An updated estimate of the CNNS signal expected in a LAr detector operated near a nuclear power reactor is presented.

  10. Energy Transport and Ionization Balance in Isochorically Heated Dense Plasmas*

    NASA Astrophysics Data System (ADS)

    Landen, Otto

    2003-04-01

    Dense plasmas, a principal state of matter in inertial confinement fusion research and in planetary and stellar environments, can now be routinely created in the laboratory at diagnosable mm-scales by x-ray radiative heating provided by high power laser produced plasmas. We discuss two recent studies in such isochorically-heated plasmas, the first examining supersonic diffusive radiative transport in foam cylinders using spectrally and temporally-resolved soft x-ray imaging [1] and the second studying solid density plasma ionization balance [2] using spectrally resolved x-ray scattering [3]. The radiation transport data provides a measure of the dense plasma heat capacity and opacity for the various foam and wall materials tested. Moreover, data from more complex radiation flow geometries further constrain the radiation transport modelling. In the case of x-ray scattering measurements, by spectrally resolving both the Compton downshifted and Doppler broadened inelastic component and the Rayleigh scattered elastic component, we can infer both the plasma electron temperature and ratio of weakly bound and free electron fraction to tightly bound electron fraction in low Z samples. The results are compared to various dense plasma ionization balance models. [1] C.A. Back, et. al., Phys. Rev. Lett. 84 (2000) 274 and Phys. Plasmas 7 (2000 ) 2126. [2] S.H. Glenzer, et. al., submitted to Phys. Rev. Lett. (2003). [3] O.L. Landen, et. al., J. Quant. Spectrosc. Radiat. Trans. 71 (2001) 465.

  11. Ionization damage in NPN transistors caused by lower energy electrons

    NASA Astrophysics Data System (ADS)

    Li, Xingji; Xiao, Jingdong; Liu, Chaoming; Zhao, Zhiming; Geng, Hongbin; Lan, Mujie; Yang, Dezhuang; He, Shiyu

    2010-09-01

    Electrical degradation of two type NPN bipolar junction transistors (BJTs) with different emitter sizes was examined under exposures of 70 and 110 keV electrons. Base and collector currents as a function of base-emitter voltage were in-situ measured during exposure. Experimental results show that both the 70 and 110 keV electrons produce an evident ionization damage to the NPN BJTs. With increasing fluence, collector currents of the NPN BJTs hardly change in the whole range of base-emitter voltage from 0 to 1.2 V, while base currents increase in a gradually mitigative trend. Base currents vary more at lower base-emitter voltages than at higher ones for a given fluence. The change in the reciprocal of current gain at a fixed base-emitter voltage of 0.65 V increases non-linearly at lower fluences and tends to be gradually saturated at higher fluences. Sensitivity to ionization damage increases for BJTs with an emitter having a larger perimeter-to-area ratio.

  12. Monte Carlo calculation of energy deposition in ionization chambers for tritium measurements

    NASA Astrophysics Data System (ADS)

    Zhilin, Chen; Shuming, Peng; Dan, Meng; Yuehong, He; Heyi, Wang

    2014-10-01

    Energy deposition in ionization chambers for tritium measurements has been theoretically studied using Monte Carlo code MCNP 5. The influence of many factors, including carrier gas, chamber size, wall materials and gas pressure, has been evaluated in the simulations. It is found that β rays emitted by tritium deposit much more energy into chambers flowing through with argon than with deuterium in them, as much as 2.7 times higher at pressure 100 Pa. As chamber size gets smaller, energy deposition decreases sharply. For an ionization chamber of 1 mL, β rays deposit less than 1% of their energy at pressure 100 Pa and only 84% even if gas pressure is as high as 100 kPa. It also indicates that gold plated ionization chamber results in the highest deposition ratio while aluminum one leads to the lowest. In addition, simulations were validated by comparison with experimental data. Results show that simulations agree well with experimental data.

  13. Fundamental Transitions and Ionization Energies of the Hydrogen Molecular Ions with Few ppt Uncertainty

    NASA Astrophysics Data System (ADS)

    Korobov, Vladimir I.; Hilico, L.; Karr, J.-Ph.

    2017-06-01

    We calculate ionization energies and fundamental vibrational transitions for H2 + , D2 + , and HD+ molecular ions. The nonrelativistic quantum electrodynamics expansion for the energy in terms of the fine structure constant α is used. Previous calculations of orders m α6 and m α7 are improved by including second-order contributions due to the vibrational motion of nuclei. Furthermore, we evaluate the largest corrections at the order m α8. That allows us to reduce the fractional uncertainty to the level of 7.6 ×10-12 for fundamental transitions and to 4.5 ×10-12 for the ionization energies.

  14. Fundamental Transitions and Ionization Energies of the Hydrogen Molecular Ions with Few ppt Uncertainty.

    PubMed

    Korobov, Vladimir I; Hilico, L; Karr, J-Ph

    2017-06-09

    We calculate ionization energies and fundamental vibrational transitions for H_{2}^{+}, D_{2}^{+}, and HD^{+} molecular ions. The nonrelativistic quantum electrodynamics expansion for the energy in terms of the fine structure constant α is used. Previous calculations of orders mα^{6} and mα^{7} are improved by including second-order contributions due to the vibrational motion of nuclei. Furthermore, we evaluate the largest corrections at the order mα^{8}. That allows us to reduce the fractional uncertainty to the level of 7.6×10^{-12} for fundamental transitions and to 4.5×10^{-12} for the ionization energies.

  15. Analytical model of ionization and energy deposition by proton beams in subcellular compartments

    NASA Astrophysics Data System (ADS)

    de Vera, Pablo; Surdutovich, Eugene; Abril, Isabel; Garcia-Molina, Rafael; Solov'yov, Andrey V.

    2014-04-01

    We present an analytical model to evaluate in a fast, simple and effective manner the energy delivered by proton beams moving through a cell model made of nucleus and cytoplasm, taking into account the energy carried by the secondary electrons generated along the proton tracks. The electronic excitation spectra of these subcellular compartments have been modelled by means of an empirical parameterization of their dielectric properties. The energy loss rate and target ionization probability induced by swift protons are evaluated by means of the dielectric formalism. With the present model we have quantified the energy delivered, the specific energy, and the number of ionizations produced per incoming ion in a typical human cell by a typical hadrontherapy proton beam having energies usually reached around the Bragg peak (below 20 MeV). We find that the specific energy per incoming ion delivered in the nucleus and in the cytoplasm are rather similar for all the proton energy range analyzed.

  16. Low-energy ionization yield in liquid argon for a coherent neutrino-nucleus scatter detector

    NASA Astrophysics Data System (ADS)

    Foxe, Michael P.

    A mode of interaction predicted by the Standard Model of particle physics, but not yet observed, is coherent neutrino-nucleus scattering (CNNS). CNNS results from the neutrino (or antineutrino) scattering coherently with the entire nucleus rather than a single nucleon. The leading challenge in detecting CNNS is the resulting sub-keV nuclear recoil energies, producing little ionization in the detector medium. In order to detect the CNNS interaction, it is beneficial to first measure the nuclear ionization yield for the chosen detector medium. The ionization yield represents the expected number of electrons produced by a nuclear recoil, and it depends both on the recoil energy and on the detector medium in which the recoil occurs. Additionally, the ionization yield depends on the applied electron drift electric field, and for this reason it should be measured directly in the detector type anticipated for future CNNS measurements. This dissertation is focused on making the prediction and measurement of the ionization yield in LAr using a dual-phase Ar detector. Due to the complexity of measuring the ionization yield at various energies, it is beneficial to also construct a predictive model for the ionization yield. In this dissertation, the prediction of the ionization yield is made on the basis of a simulation of a two-stage process. The number of ionizations generated from Ar recoil of a given energy is simulated using a Monte Carlo atomic collision model, along with the cross sections for ionization and excitation in Ar + Ar collisions. After the electrons are generated, a fraction of them recombine with the initially generated ion cloud. The electron recombination fraction is simulated by assigning the emitted electrons either 1 or 10 eV of initial kinetic energy and transporting the electrons under the influence of Coulomb forces of the ion cloud and an applied external electric field. The simulation predicts the energy dependent ionization yield, with a value of

  17. Note: Energy calibration of a femtosecond photoelectron imaging detector with correction for the ponderomotive shift of atomic ionization energies

    NASA Astrophysics Data System (ADS)

    Hüter, O.; Temps, F.

    2017-04-01

    Femtosecond photoelectron imaging spectroscopy is a powerful technique for following state-resolved molecular transformations in complex coupled potential energy landscapes. To avoid unwanted nonlinear side-effects, the employed laser pulse energies are usually reduced to minimal values. However, the energy calibration of the photoelectron imaging detector is ideally performed using multi-photon above-threshold ionization of suitable atomic species, for which rather high laser intensities are required. In this work, we show that the calibration spectra of xenon obtained with high laser pulse energies cannot be directly used for the evaluation of molecular photoelectron spectra recorded using low-energy laser pulses. The reason is the intensity-dependent AC Stark shift of the atomic ionization energies to larger values, which in turn leads to a corresponding decrease of the photoelectron kinetic energies. We present a simple procedure to quantify this so-called ponderomotive shift and calculate the theoretically expected un-shifted photoelectron energies.

  18. Ionization energies of the C60 fullerene and its hydrogenated derivatives C60H18 and C60H36 determined by electron ionization

    NASA Astrophysics Data System (ADS)

    Pogulay, Andrey V.; Abzalimov, Rinat R.; Nasibullaev, Shamil'k.; Lobach, Anatoly S.; Drewello, Thomas; Vasil'Ev, Yury V.

    2004-04-01

    Modification of a method for processing positive ion ionization efficiency curves of polyatomic molecules, as developed earlier by Märk and coworkers, has been described. Based on the method, the first, second, and third ionization energies of C60 have been re-examined and found to be in excellent agreement with the most reliable literature data. The ionization energies for C60H18 and C60H36 have been measured for the first time and were established as 7.3+/-0.3 eV and 7.01+/-0.25 eV, respectively. Although the appearance energy of C60H362+ (18.7+/-0.2 eV) has been determined to be lower than that of C602+ (18.98+/-0.35 eV), the reverse scenario is true for the second ionization energies of C60H36 and C60.

  19. Multiphoton laser ionization for energy conversion in barium vapor

    NASA Astrophysics Data System (ADS)

    Makdisi, Y.; Kokaj, J.; Afrousheh, K.; Mathew, J.; Nair, R.; Pichler, G.

    2013-03-01

    We have studied the ion detection of barium atoms in special heated ovens with a tungsten rod in the middle of the stainless steel tube. The tungsten rod was heated indirectly by the oven body heaters. A bias voltage between the cell body and the tungsten rod of 9 V was used to collect electrons, after the barium ions had been created. However, we could collect the electrons even without the bias voltage, although with ten times less efficiency. We studied the conditions for the successful bias-less thermionic signal detection using excimer/dye laser two-photon excitation of Rydberg states below and above the first ionization limit (two-photon wavelength at 475.79 nm). We employed a hot-pipe oven and heat-pipe oven (with inserted mesh) in order to generate different barium vapor distributions inside the oven. The thermionic signal increased by a factor of two under heat-pipe oven conditions.

  20. HEATING OF THE WARM IONIZED MEDIUM BY LOW-ENERGY COSMIC RAYS

    SciTech Connect

    Walker, Mark A.

    2016-02-10

    In light of evidence for a high ionization rate due to low-energy cosmic rays (LECR) in diffuse molecular gas in the solar neighborhood, we evaluate their heat input to the warm ionized medium (WIM). LECR are much more effective at heating plasma than they are at heating neutrals. We show that the upper end of the measured ionization rates corresponds to a local LECR heating rate sufficient to maintain the WIM against radiative cooling, independent of the nature of the ionizing particles or the detailed shape of their spectrum. Elsewhere in the Galaxy the LECR heating rates may be higher than those measured locally. In particular, higher fluxes of LECR have been suggested for the inner Galactic disk, based on the observed hard X-ray emission, with correspondingly larger heating rates implied for the WIM. We conclude that LECR play an important and perhaps dominant role in the thermal balance of the WIM.

  1. Ionization energy shift of characteristic K x-ray lines from high-Z materials for plasma diagnostics

    SciTech Connect

    Słabkowska, K.; Szymańska, E.; Polasik, M.; Pereira, N. R.; Rzadkiewicz, J.; Seely, J. F.; Weber, B. V.; Schumer, J. W.

    2014-03-15

    The energy of the characteristic x-rays emitted by high atomic number atoms in a plasma that contains energetic electrons depends on the atom's ionization. For tungsten, the ionization energy shift of the L-lines has recently been used to diagnose the plasma's ionization; the change in energy of a K-line has been measured for iridium and observed for ytterbium. Here, we present detailed computations of the ionization energy shift to K-lines of these and an additional element, dysprosium; for these atoms, some K-lines nearly coincide in energy with K-edges of slightly lower Z atoms so that a change in transmission behind a K-edge filter betrays a change in energy. The ionization energy shift of such high-energy K-lines may enable a unique diagnostic when the plasma is inside an otherwise opaque enclosure such as hohlraums used on the National Ignition Facility.

  2. Electron-impact ionization of helium for equal-energy-sharing kinematics

    SciTech Connect

    Stelbovics, A.T.; Bray, I.; Fursa, D.V.; Bartschat, K.

    2005-05-15

    The close-coupling approach to electron-helium single ionization is analyzed and several ways of defining the scattering amplitudes are determined, for both equal- and unequal-energy outgoing electrons. Nevertheless, the various definitions all lead to the same cross section. The convergent close-coupling (CCC) method with Laguerre (CCC-L) and box-based (CCC-B) target functions is applied to calculate electron-impact ionization of helium for the cases where the two outgoing electrons have equal energy. Excellent absolute agreement with experiment is obtained for all available cases of comparison.

  3. Ionization of hydrogen atoms by multiply charged ions at low energies: The scaling law

    SciTech Connect

    Janev, R.K.; Ivanovski, G.; Solov'ev, E.A. Faculty of Natural Sciences and Mathematics, St. Cyril and Methodius University, P.O. Box 162, 91000 Skopje, Macedonia )

    1994-02-01

    Using the adiabatic superpromotion model of low-energy atomic collisions, a simple scaling relationship is derived for the ionization cross section of hydrogen atoms colliding with multiply charged ions. Detailed ionization-cross-section calculations for the systems H(1[ital s])+He[sup 2+], C[sup 6+], and O[sup 8+] have been performed and used to determine three numerical constants in the cross-section-scaling relationship. The scaled cross section represents well the available data for fully stripped ions with charge [ital Z][ge]2 in the energy region below the cross-section maximum.

  4. Ionization of Water Clusters is Mediated by Exciton Energy Transfer from Argon Clusters

    SciTech Connect

    Golan, Amir; Ahmed, Musahid

    2012-01-25

    The exciton energy deposited in an argon cluster, (Arn ,< n=20>) using VUV radiation is transferred to softly ionize doped water clusters, ((H2O)n, n=1-9) leading to the formation of non-fragmented clusters. Following the initial excitation, electronic energy is channeled to ionize the doped water cluster while evaporating the Ar shell, allowing identification of fragmented and complete water cluster ions. Examination of the photoionization efficiency curve shows that cluster evaporation from excitons located above 12.6 eV are not enough to cool the energized water cluster ion, and leads to their dissociation to (H2O)n-2H+ (protonated) clusters.

  5. Energy and angle differential cross sections for the electron-impact double ionization of helium

    SciTech Connect

    Colgan, James P; Pindzola, M S; Robicheaux, F

    2008-01-01

    Energy and angle differential cross sections for the electron-impact double ionization of helium are calculated using a non-perturbative time-dependent close-coupling method. Collision probabilities are found by projection of a time evolved nine dimensional coordinate space wave function onto fully antisymmetric products of spatial and spin functions representing three outgoing Coulomb waves. At an incident energy of 106 eV, we present double energy differential cross sections and pentuple energy and angle differential cross sections. The pentuple energy and angle differential cross sections are found to be in relative agreement with the shapes observed in recent (e,3e) reaction microscope experiments. Integration of the differential cross sections over all energies and angles yields a total ionization cross section that is also in reasonable agreement with absolute crossed-beams experiments.

  6. Multiply-ionized Atoms at Low Energy for Precise Measurements

    NASA Astrophysics Data System (ADS)

    Fogwell Hoogerheide, Shannon; Tan, Joseph N.

    2014-05-01

    Recent work at NIST introduced a new system for the slowing, capture and manipulation of multiply-ionized atoms in a controlled environment suitable for precision measurements. As a demonstration of its potentials, we have measured the lifetimes of metastable states in krypton and argon (gases), and are now extending this technique to metals such as iron. Work is also underway on a table-top apparatus that incorporates a miniature electron-beam ion trap (EBIT) coupled to a cryo-cooled, compact Penning trap to enable spectroscopic studies of interest for atomic physics, astrophysics, and metrology. This apparatus will allow charge exchange between laser-excited Rydberg rubidium atoms and isolated bare nuclei, opening the way for precision spectroscopy of one-electron ions in Rydberg states using optical frequency comb technology. Earlier theoretical work at NIST has shown that such measurements would provide a new determination of the Rydberg constant that was independent of the proton radius. Such a measurement could help resolve the proton-radius puzzle. Additional applications could include the study of very-long-lived atomic states proposed for new atomic frequency standards or laboratory studies of potential time variation of the fine structure constant. SFH acknowledges funding through a National Research Council Reseach Associateship award.

  7. Electronic relativistic effects on K-shell ionization by low-energy protons

    SciTech Connect

    Mukoyama, T.; Sarkadi, L.

    1981-01-01

    K-shell ionization cross sections by low-energy proton impact have been calculated in the relativistic plane-wave Born approximation, taking into account the effects of binding-energy increase and Coulomb deflection. The calculated values are compared with the recent experimental cross sections of Zander and Andrews. It is found that the use of Dirac wave functions for target electrons improves agreement with the experimental results, but the theoretical predictions are still systematically higher at the lower proton energies.

  8. Determination of flux ionization fraction using a quartz crystal microbalance and a gridded energy analyzer in an ionized magnetron sputtering system

    NASA Astrophysics Data System (ADS)

    Green, K. M.; Hayden, D. B.; Juliano, D. R.; Ruzic, D. N.

    1997-12-01

    A diagnostic which combines a quartz crystal microbalance (QCM) and a gridded energy analyzer has been developed to measure the metal flux ionization fraction in a modified commercial dc magnetron sputtering device. The sensor is mounted on a linear motion feedthrough and embedded in a slot in the substrate plane to allow for measuring the uniformity in deposition and ionization throughout the plane of the wafer. Radio-frequency (rf) power is introduced through a coil to ionize the Al atoms. The metal flux ionization fraction at the QCM is determined by comparing the total deposition rate with and without a bias that screens out the ions, but that leaves the plasma undisturbed. By varying the voltage applied to the grids, the plasma potential is determined. At a pressure of 35 mTorr, a magnetron power of 2 kW, and a net rf power of 310±5 W, 78±5% ionization was found.

  9. Nonconstant ponderomotive energy in above-threshold ionization by intense short laser pulses

    NASA Astrophysics Data System (ADS)

    Della Picca, R.; Gramajo, A. A.; Garibotti, C. R.; López, S. D.; Arbó, D. G.

    2016-02-01

    We analyze the contribution of the quiver kinetic energy acquired by an electron in an oscillating electric field of a short laser pulse to the energy balance in atomic ionization processes. Due to the time dependence of this additional kinetic energy, a temporal average is assumed to preserve a stationary energy conservation rule, which is used to predict the position of the energy peaks observed in the photoelectron (PE) spectra. For a plane wave and a flattop pulse, the mean value of the quiver energy over the whole pulse leads to the concept of ponderomotive energy Up. However, for a short pulse with a fast changing intensity, the stationary approximation loses its validity. We check these concepts by studying first the PE spectrum within the semiclassical model (SCM) for multiple-step pulses. The SCM offers the possibility to establish a connection between emission times and the PE spectrum in the energy domain. We show that PE substructures stem from ionization at different times mapping the pulse envelope. We also analyze the PE spectrum for a realistic sine-squared envelope within the Coulomb-Volkov and ab initio calculations solving the time-dependent Schrödinger equation. We found that the electron emission amplitudes produced at different times interfere with each other producing, in this way, a new additional pattern that modulates the above-threshold ionization (ATI) peaks.

  10. Comparison of Internal Energy Distributions of Ions Created by Electrospray Ionization and Laser Ablation-Liquid Vortex Capture-Electrospray Ionization

    SciTech Connect

    Cahill, John F.; Kertesz, Vilmos; Ovchinnikova, Olga S.; Van Berkel, Gary J.

    2015-06-27

    Recently a number of techniques have combined laser ablation with liquid capture for mass spectrometry spot sampling and imaging applications. The newly developed non-contact liquid-vortex capture probe has been used to efficiently collect 355 nm UV laser ablated material in a continuous flow solvent stream in which the captured material dissolves and then undergoes electrospray ionization. This sampling and ionization approach has produced what appear to be classic electrospray ionization spectra; however, the softness of this sampling/ionization process versus simple electrospray ionization has not been definitely determined. A series of benzlypyridinium salts, known as thermometer ions, were used to compare internal energy distributions between electrospray ionization and the UV laser ablation liquid-vortex capture probe electrospray combination. Measured internal energy distributions were identical between the two techniques, even with differences in laser fluence (0.7-3.1 J cm-2) and when using UV-absorbing or non-UV-absorbing sample substrates. This data indicates ions formed directly by UV laser ablation, if any, are likely an extremely small constituent of the total ion signal observed. Instead, neutral molecules, clusters or particulates ejected from the surface during laser ablation, subsequently captured and dissolved in the flowing solvent stream then electrosprayed are the predominant source of ion signal observed. The electrospray ionization process used controls the softness of the technique.

  11. Comparison of Internal Energy Distributions of Ions Created by Electrospray Ionization and Laser Ablation-Liquid Vortex Capture-Electrospray Ionization

    DOE PAGES

    Cahill, John F.; Kertesz, Vilmos; Ovchinnikova, Olga S.; ...

    2015-06-27

    Recently a number of techniques have combined laser ablation with liquid capture for mass spectrometry spot sampling and imaging applications. The newly developed non-contact liquid-vortex capture probe has been used to efficiently collect 355 nm UV laser ablated material in a continuous flow solvent stream in which the captured material dissolves and then undergoes electrospray ionization. This sampling and ionization approach has produced what appear to be classic electrospray ionization spectra; however, the softness of this sampling/ionization process versus simple electrospray ionization has not been definitely determined. A series of benzlypyridinium salts, known as thermometer ions, were used to comparemore » internal energy distributions between electrospray ionization and the UV laser ablation liquid-vortex capture probe electrospray combination. Measured internal energy distributions were identical between the two techniques, even with differences in laser fluence (0.7-3.1 J cm-2) and when using UV-absorbing or non-UV-absorbing sample substrates. This data indicates ions formed directly by UV laser ablation, if any, are likely an extremely small constituent of the total ion signal observed. Instead, neutral molecules, clusters or particulates ejected from the surface during laser ablation, subsequently captured and dissolved in the flowing solvent stream then electrosprayed are the predominant source of ion signal observed. The electrospray ionization process used controls the softness of the technique.« less

  12. Determination of the ionization energy of vanadium levels in zinc selenide

    SciTech Connect

    Makhniy, V. P.; Kinzerskaya, O. V.

    2012-02-15

    By comparing the experimental spectra of optical absorption and photoconductivity with those calculated using the Lucovsky formulas, it is established that the V impurity in ZnSe forms acceptor levels with the ionization energy 0.62 eV.

  13. Relating polarizability to volume, ionization energy, electronegativity, hardness, moments of momentum, and other molecular properties

    SciTech Connect

    Blair, Shamus A.; Thakkar, Ajit J.

    2014-08-21

    Semiquantitative relationships between the mean static dipole polarizability and other molecular properties such as the volume, ionization energy, electronegativity, hardness, and moments of momentum are explored. The relationships are tested using density functional theory computations on the 1641 neutral, ground-state, organic molecules in the TABS database. The best polarizability approximations have median errors under 5%.

  14. Elastic, excitation, ionization and charge transfer cross sections of current interest in fusion energy research

    SciTech Connect

    Schultz, D.R.; Krstic, P.S.

    1996-12-31

    Due to the present interest in modeling and diagnosing the edge and divertor plasma regions in magnetically confined fusion devices, we have sought to provide new calculations regarding the elastic, excitation, ionization, and charge transfer cross sections in collisions among relevant ions, neutrals, and isotopes in the low- to intermediate-energy regime. We summarize here some of our recent work.

  15. Emergence of a Higher Energy Structure in Strong Field Ionization with Inhomogeneous Electric Fields.

    PubMed

    Ortmann, L; Pérez-Hernández, J A; Ciappina, M F; Schötz, J; Chacón, A; Zeraouli, G; Kling, M F; Roso, L; Lewenstein, M; Landsman, A S

    2017-08-04

    Studies of strong field ionization have historically relied on the strong field approximation, which neglects all spatial dependence in the forces experienced by the electron after ionization. More recently, the small spatial inhomogeneity introduced by the long-range Coulomb potential has been linked to a number of important features in the photoelectron spectrum, such as Coulomb asymmetry, Coulomb focusing, and the low energy structure. Here, we demonstrate using midinfrared laser wavelength that a time-varying spatial dependence in the laser electric field, such as that produced in the vicinity of a nanostructure, creates a prominent higher energy peak. This higher energy structure (HES) originates from direct electrons ionized near the peak of a single half-cycle of the laser pulse. The HES is separated from all other ionization events, with its location and width highly dependent on the strength of spatial inhomogeneity. Hence, the HES can be used as a sensitive tool for near-field characterization in the "intermediate regime," where the electron's quiver amplitude is comparable to the field decay length. Moreover, the large accumulation of electrons with tuneable energy suggests a promising method for creating a localized source of electron pulses of attosecond duration using tabletop laser technology.

  16. Emergence of a Higher Energy Structure in Strong Field Ionization with Inhomogeneous Electric Fields

    NASA Astrophysics Data System (ADS)

    Ortmann, L.; Pérez-Hernández, J. A.; Ciappina, M. F.; Schötz, J.; Chacón, A.; Zeraouli, G.; Kling, M. F.; Roso, L.; Lewenstein, M.; Landsman, A. S.

    2017-08-01

    Studies of strong field ionization have historically relied on the strong field approximation, which neglects all spatial dependence in the forces experienced by the electron after ionization. More recently, the small spatial inhomogeneity introduced by the long-range Coulomb potential has been linked to a number of important features in the photoelectron spectrum, such as Coulomb asymmetry, Coulomb focusing, and the low energy structure. Here, we demonstrate using midinfrared laser wavelength that a time-varying spatial dependence in the laser electric field, such as that produced in the vicinity of a nanostructure, creates a prominent higher energy peak. This higher energy structure (HES) originates from direct electrons ionized near the peak of a single half-cycle of the laser pulse. The HES is separated from all other ionization events, with its location and width highly dependent on the strength of spatial inhomogeneity. Hence, the HES can be used as a sensitive tool for near-field characterization in the "intermediate regime," where the electron's quiver amplitude is comparable to the field decay length. Moreover, the large accumulation of electrons with tuneable energy suggests a promising method for creating a localized source of electron pulses of attosecond duration using tabletop laser technology.

  17. Use of thin ionization calorimeters for measurements of cosmic ray energy spectra

    NASA Technical Reports Server (NTRS)

    Jones, W. V.; Ormes, J. S.; Schmidt, W. K. H.

    1976-01-01

    The reliability of performing measurements of cosmic ray energy spectra with a thin ionization calorimeter was investigated. Monte Carlo simulations were used to determine whether energy response fluctuations would cause measured spectra to be different from the primary spectra. First, Gaussian distributions were assumed for the calorimeter energy resolutions. The second method employed a detailed Monte Carlo simulation of cascades from an isotropic flux of protons. The results show that as long as the energy resolution does not change significantly with energy, the spectral indices can be reliably determined even for sigma sub e/e = 50%. However, if the energy resolution is strongly energy dependent, the measured spectra do not reproduce the true spectra. Energy resolutions greatly improving with energy result in measured spectra that are too steep, while resolutions getting much worse with energy cause the measured spectra to be too flat.

  18. Cataract after exposure to non-ionizing radiant energy.

    PubMed Central

    Zaret, M M; Snyder, W Z; Birenbaum, L

    1976-01-01

    The case histories of two individuals exposed to thermal radiation emitted from an electric oven and range were presented. In one patient, earlier exposure to medical diathermy appears to have initiated delayed or late-appearing, capsular cataracts. Instead of the anticipated slow progression, the cataractogenesis was accelerated following recent, repeated exposure to the intense, infrared radiation. In the other patient, exposed solely to infrared radiation, a chorioretinal lesion indistinguishable from the type characteristically secondary to repeated, thermal radiation was observed. More recently, the earliest sign of thermal radiation cataractogenesis, capsular opacification, has become evident. The widespread availability of radiant energy sources such as diathermy machines, microwave ovens, and electric ovens and ranges makes it imperative to examine carefully any possible hazards that may result from their use. With this in mind, radiant energy should be considered in the differential diagnosis of cataractogenesis. Images PMID:990233

  19. Cataract after exposure to non-ionizing radiant energy.

    PubMed

    Zaret, M M; Snyder, W Z; Birenbaum, L

    1976-09-01

    The case histories of two individuals exposed to thermal radiation emitted from an electric oven and range were presented. In one patient, earlier exposure to medical diathermy appears to have initiated delayed or late-appearing, capsular cataracts. Instead of the anticipated slow progression, the cataractogenesis was accelerated following recent, repeated exposure to the intense, infrared radiation. In the other patient, exposed solely to infrared radiation, a chorioretinal lesion indistinguishable from the type characteristically secondary to repeated, thermal radiation was observed. More recently, the earliest sign of thermal radiation cataractogenesis, capsular opacification, has become evident. The widespread availability of radiant energy sources such as diathermy machines, microwave ovens, and electric ovens and ranges makes it imperative to examine carefully any possible hazards that may result from their use. With this in mind, radiant energy should be considered in the differential diagnosis of cataractogenesis.

  20. Accurate energy levels for singly ionized platinum (Pt II)

    NASA Technical Reports Server (NTRS)

    Reader, Joseph; Acquista, Nicolo; Sansonetti, Craig J.; Engleman, Rolf, Jr.

    1988-01-01

    New observations of the spectrum of Pt II have been made with hollow-cathode lamps. The region from 1032 to 4101 A was observed photographically with a 10.7-m normal-incidence spectrograph. The region from 2245 to 5223 A was observed with a Fourier-transform spectrometer. Wavelength measurements were made for 558 lines. The uncertainties vary from 0.0005 to 0.004 A. From these measurements and three parity-forbidden transitions in the infrared, accurate values were determined for 28 even and 72 odd energy levels of Pt II.

  1. Interplay between relativistic energy corrections and resonant excitations in x-ray multiphoton ionization dynamics of Xe atoms

    NASA Astrophysics Data System (ADS)

    Toyota, Koudai; Son, Sang-Kil; Santra, Robin

    2017-04-01

    In this paper, we theoretically study x-ray multiphoton ionization dynamics of heavy atoms taking into account relativistic and resonance effects. When an atom is exposed to an intense x-ray pulse generated by an x-ray free-electron laser (XFEL), it is ionized to a highly charged ion via a sequence of single-photon ionization and accompanying relaxation processes, and its final charge state is limited by the last ionic state that can be ionized by a single-photon ionization. If x-ray multiphoton ionization involves deep inner-shell electrons in heavy atoms, energy shifts by relativistic effects play an important role in ionization dynamics, as pointed out in Phys. Rev. Lett. 110, 173005 (2013), 10.1103/PhysRevLett.110.173005. On the other hand, if the x-ray beam has a broad energy bandwidth, the high-intensity x-ray pulse can drive resonant photoexcitations for a broad range of ionic states and ionize even beyond the direct one-photon ionization limit, as first proposed in Nat. Photon. 6, 858 (2012), 10.1038/nphoton.2012.261. To investigate both relativistic and resonance effects, we extend the xatom toolkit to incorporate relativistic energy corrections and resonant excitations in x-ray multiphoton ionization dynamics calculations. Charge-state distributions are calculated for Xe atoms interacting with intense XFEL pulses at a photon energy of 1.5 keV and 5.5 keV, respectively. For both photon energies, we demonstrate that the role of resonant excitations in ionization dynamics is altered due to significant shifts of orbital energy levels by relativistic effects. Therefore, it is necessary to take into account both effects to accurately simulate multiphoton multiple ionization dynamics at high x-ray intensity.

  2. C1s and O1s photoelectron satellite spectra of CO with symmetry-dependent vibrational excitations

    NASA Astrophysics Data System (ADS)

    Ehara, M.; Kuramoto, K.; Nakatsuji, H.; Hoshino, M.; Tanaka, T.; Kitajima, M.; Tanaka, H.; De Fanis, A.; Tamenori, Y.; Ueda, K.

    2006-09-01

    The photoelectron shake-up satellite spectra that accompany the C1s and O1s main lines of carbon monoxide have been studied by a combination of high-resolution x-ray photoelectron spectroscopy and accurate ab initio calculations. The symmetry-adapted cluster-expansion configuration-interaction general-R method satisfactorily reproduces the satellite spectra over a wide energy region, and the quantitative assignments are proposed for the 16 and 12 satellite bands for C1s and O1s spectra, respectively. Satellite peaks above the π-1π * transitions are mainly assigned to the Rydberg excitations accompanying the inner-shell ionization. Many shake-up states, which interact strongly with three-electron processes such as π-2π*2 and n-2π*2, are calculated in the low-energy region, while the continuous Rydberg excitations are obtained with small intensities in the higher-energy region. The vibrational structures of low-lying shake-up states have been examined for both C1s and O1s ionizations. The vibrational structures appear in the low-lying C1s satellite states, and the symmetry-dependent angular distributions for the satellite emission have enabled the Σ and Π symmetries to be resolved. On the other hand, the potential curves of the low-lying O1s shake-up states are predicted to be weakly bound or repulsive.

  3. On the accuracy of density functional theory and wave function methods for calculating vertical ionization energies

    SciTech Connect

    McKechnie, Scott; Booth, George H.; Cohen, Aron J.; Cole, Jacqueline M.

    2015-05-21

    The best practice in computational methods for determining vertical ionization energies (VIEs) is assessed, via reference to experimentally determined VIEs that are corroborated by highly accurate coupled-cluster calculations. These reference values are used to benchmark the performance of density functional theory (DFT) and wave function methods: Hartree-Fock theory, second-order Møller-Plesset perturbation theory, and Electron Propagator Theory (EPT). The core test set consists of 147 small molecules. An extended set of six larger molecules, from benzene to hexacene, is also considered to investigate the dependence of the results on molecule size. The closest agreement with experiment is found for ionization energies obtained from total energy difference calculations. In particular, DFT calculations using exchange-correlation functionals with either a large amount of exact exchange or long-range correction perform best. The results from these functionals are also the least sensitive to an increase in molecule size. In general, ionization energies calculated directly from the orbital energies of the neutral species are less accurate and more sensitive to an increase in molecule size. For the single-calculation approach, the EPT calculations are in closest agreement for both sets of molecules. For the orbital energies from DFT functionals, only those with long-range correction give quantitative agreement with dramatic failing for all other functionals considered. The results offer a practical hierarchy of approximations for the calculation of vertical ionization energies. In addition, the experimental and computational reference values can be used as a standardized set of benchmarks, against which other approximate methods can be compared.

  4. On the accuracy of density functional theory and wave function methods for calculating vertical ionization energies

    NASA Astrophysics Data System (ADS)

    McKechnie, Scott; Booth, George H.; Cohen, Aron J.; Cole, Jacqueline M.

    2015-05-01

    The best practice in computational methods for determining vertical ionization energies (VIEs) is assessed, via reference to experimentally determined VIEs that are corroborated by highly accurate coupled-cluster calculations. These reference values are used to benchmark the performance of density functional theory (DFT) and wave function methods: Hartree-Fock theory, second-order Møller-Plesset perturbation theory, and Electron Propagator Theory (EPT). The core test set consists of 147 small molecules. An extended set of six larger molecules, from benzene to hexacene, is also considered to investigate the dependence of the results on molecule size. The closest agreement with experiment is found for ionization energies obtained from total energy difference calculations. In particular, DFT calculations using exchange-correlation functionals with either a large amount of exact exchange or long-range correction perform best. The results from these functionals are also the least sensitive to an increase in molecule size. In general, ionization energies calculated directly from the orbital energies of the neutral species are less accurate and more sensitive to an increase in molecule size. For the single-calculation approach, the EPT calculations are in closest agreement for both sets of molecules. For the orbital energies from DFT functionals, only those with long-range correction give quantitative agreement with dramatic failing for all other functionals considered. The results offer a practical hierarchy of approximations for the calculation of vertical ionization energies. In addition, the experimental and computational reference values can be used as a standardized set of benchmarks, against which other approximate methods can be compared.

  5. On the accuracy of density functional theory and wave function methods for calculating vertical ionization energies.

    PubMed

    McKechnie, Scott; Booth, George H; Cohen, Aron J; Cole, Jacqueline M

    2015-05-21

    The best practice in computational methods for determining vertical ionization energies (VIEs) is assessed, via reference to experimentally determined VIEs that are corroborated by highly accurate coupled-cluster calculations. These reference values are used to benchmark the performance of density functional theory (DFT) and wave function methods: Hartree-Fock theory, second-order Møller-Plesset perturbation theory, and Electron Propagator Theory (EPT). The core test set consists of 147 small molecules. An extended set of six larger molecules, from benzene to hexacene, is also considered to investigate the dependence of the results on molecule size. The closest agreement with experiment is found for ionization energies obtained from total energy difference calculations. In particular, DFT calculations using exchange-correlation functionals with either a large amount of exact exchange or long-range correction perform best. The results from these functionals are also the least sensitive to an increase in molecule size. In general, ionization energies calculated directly from the orbital energies of the neutral species are less accurate and more sensitive to an increase in molecule size. For the single-calculation approach, the EPT calculations are in closest agreement for both sets of molecules. For the orbital energies from DFT functionals, only those with long-range correction give quantitative agreement with dramatic failing for all other functionals considered. The results offer a practical hierarchy of approximations for the calculation of vertical ionization energies. In addition, the experimental and computational reference values can be used as a standardized set of benchmarks, against which other approximate methods can be compared.

  6. On the accuracy of density functional theory and wave function methods for calculating vertical ionization energies.

    SciTech Connect

    McKechnie, Scott; Booth, George H.; Cohen, Aron J.; Cole, Jacqueline M.

    2015-05-21

    The best practice in computational methods for determining vertical ionization energies (VIEs) is assessed, via reference to experimentally determined VIEs that are corroborated by highly accurate coupled-cluster calculations. These reference values are used to benchmark the performance of density-functional theory (DFT) and wave function methods: Hartree-Fock theory (HF), second-order Møller-Plesset perturbation theory (MP2) and Electron Propagator Theory (EPT). The core test set consists of 147 small molecules. An extended set of six larger molecules, from benzene to hexacene, is also considered to investigate the dependence of the results on molecule size. The closest agreement with experiment is found for ionization energies obtained from total energy diff calculations. In particular, DFT calculations using exchange-correlation functionals with either a large amount of exact exchange or long-range correction perform best. The results from these functionals are also the least sensitive to an increase in molecule size. In general, ionization energies calculated directly from the orbital energies of the neutral species are less accurate and more sensitive to an increase in molecule size. For the single-calculation approach, the EPT calculations are in closest agreement for both sets of molecules. For the orbital energies from DFT functionals, only those with long-range correction give quantitative agreement with dramatic failing for all other functionals considered. The results offer a practical hierarchy of approximations for the calculation of vertical ionization energies. In addition, the experimental and computational reference values can be used as a standardized set of benchmarks, against which other approximate methods can be compared.

  7. Surface ionization mass spectrometry of drugs in the thermal and hyperthermal energy range -- a comparative study

    NASA Astrophysics Data System (ADS)

    Dagan, Shai; Amirav, Aviv; Fujü, Toshihiro

    1995-12-01

    Thermal and hyperthermal surface ionization (SI) mass spectra of nicotine, caffeine and lidocaine were obtained using a rhenium oxide surface. Thermal surface ionization was studied on an oxidized surface positioned inside an electron impact ion source, while hyperthermal surface ionization (HSI) was obtained upon seeding the compounds into a hydrogen or helium supersonic molecular beam that scattered from the rhenium oxide surface. Both HSI and SI provide rich, informative and complementary mass spectral information. The results indicate that SI follows thermal dissociation processes on the surface prior to the desorption of the ion, while in HSI no thermal equilibrium is established and the ionization process is impulsive, followed by mostly unimolecular ion dissociation. HSI mass spectra are similar to electron impact mass spectra in the fragment ion masses, but the observed relative intensities are different. HSI is a softer ionization method compared to SI, and enables the degree of ion fragmentation to be tuned so that it can be minimized to a low level at low molecular kinetic energy. In SI, limited control over the degree of fragmentation is possible through the surface temperature. The analytical mass spectrometric applications of SI and HSI are briefly mentioned.

  8. Testing excited-state energy-density functionals and potentials with the ionization potential theorem

    NASA Astrophysics Data System (ADS)

    Harbola, Manoj; Myneni, Hemanadhan; Shamim, Md.

    2014-03-01

    The modified local spin density functional and the related local potential for excited-states are tested by employing the ionization potential theorem. The functional is constructed by splitting k-space. Since its functional derivative cannot be obtained easily, the corresponding potential is given by analogy to its ground-state counterpart. Further, to calculate the highest occupied orbital energy ɛmax accurately, the potential is corrected for its asymptotic behavior by employing the van Leeuwen-Barends correction to it. The highest occupied orbital energy ɛmax thus obtained is then compared with the ΔSCF ionization energy calculated using the excited-state functional. It is shown that the two match quite accurately, demonstrating thereby that our approach of constructing excited-state functional is on sound footing.

  9. Low energy electron-impact ionization of hydrogen atom for coplanar equal-energy-sharing kinematics in Debye plasmas

    NASA Astrophysics Data System (ADS)

    Li, Jun; Zhang, Song Bin; Ye, Bang Jiao; Wang, Jian Guo; Janev, R. K.

    2016-12-01

    Low energy electron-impact ionization of hydrogen atom in Debye plasmas has been investigated by employing the exterior complex scaling method. The interactions between the charged particles in the plasma have been represented by Debye-Hückel potentials. Triple differential cross sections (TDCS) in the coplanar equal-energy-sharing geometry at an incident energy of 15.6 eV for different screening lengths are reported. As the screening strength increases, TDCS change significantly. The evolutions of dominant typical peak structures of the TDCS are studied in detail for different screening lengths and for different coplanar equal-energy-sharing geometries.

  10. Dissociative ionization of the H 2O molecule induced by medium-energy singly charged projectiles

    NASA Astrophysics Data System (ADS)

    Kovács, S. T. S.; Herczku, P.; Juhász, Z.; Sarkadi, L.; Gulyás, L.; Sulik, B.

    2017-09-01

    We report on the fragmentation of the water molecule by 1 MeV H+ and He+ and 650 keV N+ ion impact. The fragment-ion energy spectra were measured by an electrostatic spectrometer at different observation angles. The obtained double-differential fragmentation cross sections for N+ are found to be more than an order of magnitude higher than that for H+. The relative ratios of the fragmentation channels are also different for the three projectiles. Additional fragmentation channels were observed in the spectra for He+ and for N+ impact, which are missing in the case of H+. From the analysis of the kinetic energy of the fragments, the maximum observed degree of ionization was found to be qmax=3 , 4, and 5 for H + , He + , and N + impact, respectively. Absolute multiple-ionization cross sections have been determined. They are compared with the predictions of the classical trajectory Monte Carlo and continuum-distorted-wave eikonal-initial-state theories. At lower degrees of ionization, theories provide reasonable agreement with experiment. The systematic overestimation of the cross section by the theories towards higher degrees of ionization indicates the failure of the independent particle model.

  11. AN ASSESSMENT OF THE ENERGY BUDGETS OF LOW-IONIZATION NUCLEAR EMISSION REGIONS

    SciTech Connect

    Eracleous, Michael; Hwang, Jason A.; Flohic, Helene M. L. G.

    2010-03-10

    Using the spectral energy distributions (SEDs) of the weak active galactic nuclei (AGNs) in 35 low-ionization nuclear emission regions (LINERs) presented in a companion paper, we assess whether photoionization by the weak AGN can power the emission-line luminosities measured through the large (few-arcsecond) apertures used in ground-based spectroscopic surveys. Spectra taken through such apertures are used to define LINERs as a class and constrain non-stellar photoionization models for LINERs. Therefore, our energy budget test is a self-consistency check of the idea that the observed emission lines are powered by an AGN. We determine the ionizing luminosities and photon rates by integrating the observed SEDs and by scaling a template SED. We find that even if all ionizing photons are absorbed by the line-emitting gas, more than half of the LINERs in this sample suffer from a deficit of ionizing photons. In 1/3 of LINERs the deficit is severe. If only 10% of the ionizing photons are absorbed by the gas, there is an ionizing photon deficit in 85% of LINERs. We disfavor the possibility that additional electromagnetic power, either obscured or emitted in the unobservable far-UV band, is available from the AGN. Therefore, we consider other power sources such as mechanical heating by compact jets from the AGN and photoionization by either young or old stars. Photoionization by young stars may be important in a small fraction of cases. Mechanical heating can provide enough power in most cases but it is not clear how this power would be transferred to the emission-line gas. Photoionization by post asymptotic giant branch stars is an important power source; it provides more ionizing photons than the AGN in more than half of the LINERs and enough ionizing photons to power the emission lines in 1/3 of the LINERs. It appears likely that the emission-line spectra of LINERs obtained from the ground include the sum of emission from different regions where different power sources

  12. Dissociation and multiple ionization energies for five polycyclic aromatic hydrocarbon molecules

    NASA Astrophysics Data System (ADS)

    Holm, A. I. S.; Johansson, H. A. B.; Cederquist, H.; Zettergren, H.

    2011-01-01

    We have performed density functional theory calculations for a range of neutral, singly, and multiply charged polycyclic aromatic hydrocarbons (PAHs), and their fragmentation products for H-, H^+-, C_2H_2-, and C_2H_2^+-emissions. The adiabatic and vertical ionization energies follow linear dependencies as functions of charge state for all five intact PAHs (naphthalene, biphenylene, anthracene, pyrene, and coronene). First estimates of the total ionization and fragmentation cross sections in ion-PAH collisions display markedly different size dependencies for pericondensed and catacondensed PAH species, reflecting differences in their first ionization energies. The dissociation energies show that the PAH^{q+}-molecules are thermodynamically stable for q ⩽ 2 (naphthalene, biphenylene, and anthracene), q ⩽ 3 (pyrene), and q ⩽ 4 (coronene). PAHs in charge states above these limits may also survive experimental time scales due to the presence of reaction barriers as deduced from explorations of the potential energy surface regions for H^+-emissions from all five PAHs and for C_2H_2+-emission from naphthalene - the smallest PAH.

  13. Internal energy deposition with silicon nanoparticle-assisted laser desorption/ionization (SPALDI) mass spectrometry

    NASA Astrophysics Data System (ADS)

    Dagan, Shai; Hua, Yimin; Boday, Dylan J.; Somogyi, Arpad; Wysocki, Ronald J.; Wysocki, Vicki H.

    2009-06-01

    The use of silicon nanoparticles for laser desorption/ionization (LDI) is a new appealing matrix-less approach for the selective and sensitive mass spectrometry of small molecules in MALDI instruments. Chemically modified silicon nanoparticles (30 nm) were previously found to require very low laser fluence in order to induce efficient LDI, which raised the question of internal energy deposition processes in that system. Here we report a comparative study of internal energy deposition from silicon nanoparticles to previously explored benzylpyridinium (BP) model compounds during LDI experiments. The internal energy deposition in silicon nanoparticle-assisted laser desorption/ionization (SPALDI) with different fluorinated linear chain modifiers (decyl, hexyl and propyl) was compared to LDI from untreated silicon nanoparticles and from the organic matrix, [alpha]-cyano-4-hydroxycinnamic acid (CHCA). The energy deposition to internal vibrational modes was evaluated by molecular ion survival curves and indicated that the ions produced by SPALDI have an internal energy threshold of 2.8-3.7 eV. This is slightly lower than the internal energy induced using the organic CHCA matrix, with similar molecular survival curves as previously reported for LDI off silicon nanowires. However, the internal energy associated with desorption/ionization from the silicon nanoparticles is significantly lower than that reported for desorption/ionization on silicon (DIOS). The measured survival yields in SPALDI gradually decrease with increasing laser fluence, contrary to reported results for silicon nanowires. The effect of modification of the silicon particle surface with semifluorinated linear chain silanes, including fluorinated decyl (C10), fluorinated hexyl (C6) and fluorinated propyl (C3) was explored too. The internal energy deposited increased with a decrease in the length of the modifier alkyl chain. Unmodified silicon particles exhibited the highest analyte internal energy

  14. Photoelectron spectroscopy of quinoline derivatives. Correlation of experimental ionization potentials with calculated molecular energies

    NASA Astrophysics Data System (ADS)

    Ahmed, A. A.; Julliard, M.; Chanon, F.; Chanon, M.; Gracian, F.; Pfister-Guillouzo, G.

    1997-03-01

    Experimental ionization potentials of quinoline 1 and substituted quinolines: 6-methylquinoline 2, 2,6-dimethylquinoline 3, 6-methoxyquinoline 4, 3-bromoquinoline 5, 2-chloro-4-methylquinoline 6, 4-hydroxyquinoline 7, 4-hydroxy-2-methylquinoline 8, 2-hydroxy-4-methylquinoline 9, 4-methoxyquinoline 10, 4- methoxy-2-methylquinoline 11, 2-methoxy-4-methylquinoline 12, were measured by photoelectron spectroscopy. Molecular orbital energies of the same derivatives were calculated by the Austin Method 1. The assignments of the bands of the photoelectron spectra were done with the aid of the theoretical calculations and on the basis of the substituent effects. For quinolines 1-6 a good agreement was found between the experimental ionization potentials and the calculated orbital energies.

  15. The excitation energies, ionization potentials, and oscillator strengths of neutral and ionized species of Uuq (Z=114) and the homolog elements Ge, Sn, and Pb.

    PubMed

    Yu, Y J; Dong, C Z; Li, J G; Fricke, B

    2008-03-28

    Multiconfiguration Dirac-Fock method is employed to calculate the excitation energies, ionization potentials, oscillator strengths, and radii for all neutral and up to four times ionized species of element Uuq, as well as the homolog elements Ge, Sn, and Pb. Using an extrapolative scheme, improved ionization potentials of Uuq were obtained with an uncertainty of less than 2000 cm(-1). Two relatively stronger resonance transitions are predicted for the element Uuq. In particular, the strongest line in Uuq, corresponding to the [6d(10)7s(2)7p(3/2)8s(1/2)](1)-->[6d(10)7s(2)7p(3/2)(2)](2) transition at 22 343 cm(-1), just lies in the prime energy region of experimental measurement.

  16. Charge transfer and ionization in collisions of Si{sup 3+} with H from low to high energy

    SciTech Connect

    Wang, J. G.; He, B.; Ning, Y.; Liu, C. L.; Yan, J.; Stancil, P. C.; Schultz, D. R.

    2006-11-15

    Charge transfer processes due to collisions of ground state Si{sup 3+}(3s {sup 1}S) ions with atomic hydrogen are investigated using the quantum-mechanical molecular-orbital close-coupling (MOCC) and classical-trajectory Monte Carlo (CTMC) methods. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial coupling matrix elements obtained from Herrero et al. [J. Phys. B 29, 5583 (1996)] which were calculated with a full configuration-interaction method. Total and state-selective single-electron capture cross sections are obtained for collision energies from 0.01 eV/u to 1 MeV/u. Total and state-selective rate coefficients are also presented for temperatures from 2x10{sup 3} K to 10{sup 7} K. Comparison with existing data reveals that the total CTMC cross sections are in good agreement with the experimental measurements at the higher considered energies and that previous Landau-Zener calculations underestimate the total rate coefficients by a factor of up to two. The CTMC calculations of target ionization are presented for high energies.

  17. Spectrum and ionization rate of low-energy Galactic cosmic rays

    NASA Astrophysics Data System (ADS)

    Nath, Biman B.; Gupta, Nayantara; Biermann, Peter L.

    2012-09-01

    We consider the rate of ionization of diffuse and molecular clouds in the interstellar medium by Galactic cosmic rays (GCRs) in order to constrain its low-energy spectrum. We extrapolate the GCR spectrum obtained from PAMELA at high energies (≥200 GeV nucleon-1) and a recently derived GCR proton flux at 1-200 GeV from observations of gamma-rays from molecular clouds, and find that the observed average Galactic ionization rate can be reconciled with this GCR spectrum if there is a low-energy cut-off for protons at 10-100 MeV. We also identify the flattening below a few GeV as being due to (a) decrease of the diffusion coefficient and dominance of convective loss at low energy and (b) the expected break in energy spectrum for a constant spectral index in momentum. We show that the inferred CR proton spectrum of ? for Ekin≤ few GeV is consistent with a power-law spectrum in momentum p-2.45± 0.4, which we identify as the spectrum at source. Diffusion loss at higher energies then introduces a steepening by E-α with α˜ 1/3, making it consistent with high-energy measurements.

  18. Quantum Computational Calculations of the Ionization Energies of Acidic and Basic Amino Acids: Aspartate, Glutamate, Arginine, Lysine, and Histidine

    NASA Astrophysics Data System (ADS)

    de Guzman, C. P.; Andrianarijaona, M.; Lee, Y. S.; Andrianarijaona, V.

    An extensive knowledge of the ionization energies of amino acids can provide vital information on protein sequencing, structure, and function. Acidic and basic amino acids are unique because they have three ionizable groups: the C-terminus, the N-terminus, and the side chain. The effects of multiple ionizable groups can be seen in how Aspartate's ionizable side chain heavily influences its preferred conformation (J Phys Chem A. 2011 April 7; 115(13): 2900-2912). Theoretical and experimental data on the ionization energies of many of these molecules is sparse. Considering each atom of the amino acid as a potential departing site for the electron gives insight on how the three ionizable groups affect the ionization process of the molecule and the dynamic coupling between the vibrational modes. In the following study, we optimized the structure of each acidic and basic amino acid then exported the three dimensional coordinates of the amino acids. We used ORCA to calculate single point energies for a region near the optimized coordinates and systematically went through the x, y, and z coordinates of each atom in the neutral and ionized forms of the amino acid. With the calculations, we were able to graph energy potential curves to better understand the quantum dynamic properties of the amino acids. The authors thank Pacific Union College Student Association for providing funds.

  19. Electron residual energy due to stochastic heating in field-ionized plasma

    SciTech Connect

    Khalilzadeh, Elnaz; Yazdanpanah, Jam Chakhmachi, Amir; Jahanpanah, Jafar; Yazdani, Elnaz

    2015-11-15

    The electron residual energy originated from the stochastic heating in under-dense field-ionized plasma is investigated here. Initially, the optical response of plasma is modeled by using two counter-propagating electromagnetic waves. In this case, the solution of motion equation of a single electron indicates that by including the ionization, the electron with higher residual energy compared with that without ionization could be obtained. In agreement with chaotic nature of the motion, it is found that the electron residual energy will be significantly changed by applying a minor change in the initial conditions. Extensive kinetic 1D-3V particle-in-cell simulations have been performed in order to resolve full plasma reactions. In this way, two different regimes of plasma behavior are observed by varying the pulse length. The results indicate that the amplitude of scattered fields in a proper long pulse length is high enough to act as a second counter-propagating wave and trigger the stochastic electron motion. On the contrary, the analyses of intensity spectrum reveal the fact that the dominant scattering mechanism tends to Thomson rather than Raman scattering by increasing the pulse length. A covariant formalism is used to describe the plasma heating so that it enables us to measure electron temperature inside and outside of the pulse region.

  20. Electron residual energy due to stochastic heating in field-ionized plasma

    NASA Astrophysics Data System (ADS)

    Khalilzadeh, Elnaz; Yazdanpanah, Jam; Jahanpanah, Jafar; Chakhmachi, Amir; Yazdani, Elnaz

    2015-11-01

    The electron residual energy originated from the stochastic heating in under-dense field-ionized plasma is investigated here. Initially, the optical response of plasma is modeled by using two counter-propagating electromagnetic waves. In this case, the solution of motion equation of a single electron indicates that by including the ionization, the electron with higher residual energy compared with that without ionization could be obtained. In agreement with chaotic nature of the motion, it is found that the electron residual energy will be significantly changed by applying a minor change in the initial conditions. Extensive kinetic 1D-3V particle-in-cell simulations have been performed in order to resolve full plasma reactions. In this way, two different regimes of plasma behavior are observed by varying the pulse length. The results indicate that the amplitude of scattered fields in a proper long pulse length is high enough to act as a second counter-propagating wave and trigger the stochastic electron motion. On the contrary, the analyses of intensity spectrum reveal the fact that the dominant scattering mechanism tends to Thomson rather than Raman scattering by increasing the pulse length. A covariant formalism is used to describe the plasma heating so that it enables us to measure electron temperature inside and outside of the pulse region.

  1. Highly correlated systems. Ionization energies of first row transition metals Sc--Zn

    SciTech Connect

    Raghavachari, K.; Trucks, G. W.

    1989-08-15

    The low-lying ionization potentials of the first row transition metal atoms Sc--Zn are calculated using fourth-order Moller--Plesset perturbation theory (MP4) and quadratic configuration interaction (QCI) techniques with large /ital spd/ and /ital spdf/ basis sets. Two ionic states have been considered for each atom yielding a total of 20 different ionization processes which we have included in this study. For Sc/sup +/--Cu/sup +/, the ionic states considered have /ital d//sup /ital n/s//sup 1/ and /ital d//sup /ital n/+1/ orbital occupations and for Zn/sup +/, the /ital d//sup 10//ital s1/ and /ital d//sup 9//ital s2/ states were studied. The MP4 method accurately reproduces the ionization potentials of Sc--Fe, but is found to be inadequate for Co--Zn. In contrast, the QCI technique performs uniformly for all ionization energies with a mean deviation from experiment of only 0.13 eV (with the /ital spdf/ basis set) after inclusion of relativistic corrections.

  2. Critically Evaluated Energy Levels, Spectral Lines, Transition Probabilities, and Intensities of Singly Ionized Vanadium (V ii)

    NASA Astrophysics Data System (ADS)

    Saloman, Edward B.; Kramida, Alexander

    2017-08-01

    The energy levels, observed spectral lines, and transition probabilities of singly ionized vanadium, V ii, have been compiled. The experimentally derived energy levels belong to the configurations 3d 4, 3d 3 ns (n = 4, 5, 6), 3d 3 np, and 3d 3 nd (n = 4, 5), 3d 34f, 3d 24s 2, and 3d 24s4p. Also included are values for some forbidden lines that may be of interest to the astrophysical community. Experimental Landé g-factors and leading percentages for the levels are included when available, as well as Ritz wavelengths calculated from the energy levels. Wavelengths and transition probabilities are reported for 3568 and 1896 transitions, respectively. From the list of observed wavelengths, 407 energy levels are determined. The observed intensities, normalized to a common scale, are provided. From the newly optimized energy levels, a revised value for the ionization energy is derived, 118,030(60) cm-1, corresponding to 14.634(7) eV. This is 130 cm-1 higher than the previously recommended value from Iglesias et al.

  3. Correlated electron-nuclear kinetic energy distribution following strong-field ionization of H2^+

    NASA Astrophysics Data System (ADS)

    Madsen, C. B.; Anis, F.; Madsen, L. B.; Esry, B. D.

    2010-03-01

    Being the simplest molecule, understanding the behavior of H2^+ in a strong laser field helps to understand more complex molecules. Theoretically, however, it is challenging to account for both electronic and nuclear motion in the ionization of even this simple molecule. Accordingly, calculating correlated electron-nuclear physical observables --- such as energy or momentum distributions --- has rarely been accomplished. Such calculations are needed to interpret recent measurements of coincidence momentum distributions of electrons and ions following the ionization of molecules by short intense laser pulses. We study how the energy absorbed from an intense laser pulse (400--800 nm, ˜10^14 W/cm^2, >=10 cycles) is shared among the nuclei and the electron of H2^+ by calculating the 2D electron-nuclei momentum distribution for a 1D model with soft-core Coulomb interactions. These 2D momentum plots reveal multiphoton structure with the energy shared between the nuclei and electron. This structure survives integrating out the nuclear energy, but not integrating out the electronic energy. ^*Supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. DoE.

  4. Ionization energies of three resonance-stabilized radicals: cyclohexadienyl (dn, n = 0, 1, 6, 7), 1-phenylpropargyl, and methylcyclohexadienyl.

    PubMed

    Krechkivska, Olha; Wilcox, Callan; O'Connor, Gerard D; Nauta, Klaas; Kable, Scott H; Schmidt, Timothy W

    2014-11-06

    The ionization energies for three resonance-stabilized radicals are determined: cyclohexadienyl, 1-phenylpropargyl, and methylcyclohexadienyl. The recommended ionization energies are, respectively, 6.820(1), 6.585(1), and 7.232(1) eV. That of cyclohexadienyl is found to be just 0.02 eV above a high level ab initio calculation [Bargholz, A.; Oswald, R.; Botschwina, P. J. Chem. Phys. 2013, 138, 014307], and that of 1-phenylpropargyl is found within the stated error of a recent experimental determination [Holzmeier, F.; Lang, M.; Hemberger, P.; Fischer, I. ChemPhysChem 2014, DOI: 10.1002/cphc.201402446]. The ionization energy of the methylcyclohexadienyl radical is consistent with the ortho isomer. Ionization energies of a range of isotopologues of cyclohexadienyl radical are given, along with their D1 ← D0 origin band positions, which indicate a blue shift of 18 cm(-1) per deuterium atom substituted. The ionization energy of cyclohexadienyl, along with the calculated bond dissociation energy of Bargholz et al., affords a new estimate of the 0 K proton affinity of benzene: 739.7 ± 2.0 kJ/mol. The ionization energies are discussed in terms of the interplay between radical and cation stabilization energies.

  5. Ionization of glycine molecules by α-particles with keV energies

    NASA Astrophysics Data System (ADS)

    Afrosimov, V. V.; Basalaev, A. A.; Kuz'michev, V. V.; Panov, M. N.; Smirnov, O. V.

    2017-04-01

    The method of "multistop" time-of-flight mass spectrometry has been used to study the mechanism of radiation damage to glycine molecules in the gas phase upon their interaction with He2+ ions with energy E p = 4 keV/amu. The relative cross sections of various elementary processes occurring in single collisions of glycine molecules with the ions were measured for the first time. A difference was found between the fragmentations of intermediate doubly charged ions formed in capture of a single electron with ionization and in two-electron capture, which is accounted for by the difference between the excitation energies of molecular ions.

  6. Extended bulk defects induced by low-energy ions during partially ionized beam deposition

    SciTech Connect

    Lee, W.I.; Wong, J.; Borrego, J.M.; Lu, T.

    1988-08-15

    The study of possible defects generated by low-energy ions during partially ionized beam (PIB) depositions was performed. No defects were observed when acceleration voltage was set lower than 1 kV. Surprisingly, several deep levels were detected up to the depth of 4000 A in the 3-kV sample. However, these levels can be annealed out at a relatively low temperature of 400 /sup 0/C. It is concluded in this study that, by properly choosing the ion energy range, PIB deposition will not cause severe damage to the substrate and can be a viable technique for growing heterostructures.

  7. Residual energy in optical-field-ionized plasmas with the longitudinal motion of electrons included.

    PubMed

    He, Bin; Chang, Tie-Qiang

    2005-06-01

    The space-charge effect on the residual energy of electrons in optical-field-ionized plasmas is studied in detail by an extended simplified model and the cloud-in-cell simulation, with the longitudinal motion of electrons included. It is found that in moderate conditions the space-charge field can influence the residual energy of electrons effectively by matching the space-charge field with laser pulse. The effect of stimulated Raman scattering on electron temperature is also investigated in detail. Finally, a comparison is made between the results and experimental data.

  8. Fluorescence Resonance Energy Transfer-based Structural Analysis of the Dihydropyridine Receptor α1S Subunit Reveals Conformational Differences Induced by Binding of the β1a Subunit.

    PubMed

    Mahalingam, Mohana; Perez, Claudio F; Fessenden, James D

    2016-06-24

    The skeletal muscle dihydropyridine receptor α1S subunit plays a key role in skeletal muscle excitation-contraction coupling by sensing membrane voltage changes and then triggering intracellular calcium release. The cytoplasmic loops connecting four homologous α1S structural domains have diverse functions, but their structural arrangement is poorly understood. Here, we used a novel FRET-based method to characterize the relative proximity of these intracellular loops in α1S subunits expressed in intact cells. In dysgenic myotubes, energy transfer was observed from an N-terminal-fused YFP to a FRET acceptor, ReAsH (resorufin arsenical hairpin binder), targeted to each α1S intracellular loop, with the highest FRET efficiencies measured to the α1S II-III loop and C-terminal tail. However, in HEK-293T cells, FRET efficiencies from the α1S N terminus to the II-III and III-IV loops and the C-terminal tail were significantly lower, thus suggesting that these loop structures are influenced by the cellular microenvironment. The addition of the β1a dihydropyridine receptor subunit enhanced FRET to the II-III loop, thus indicating that β1a binding directly affects II-III loop conformation. This specific structural change required the C-terminal 36 amino acids of β1a, which are essential to support EC coupling. Direct FRET measurements between α1S and β1a confirmed that both wild type and truncated β1a bind similarly to α1S These results provide new insights into the role of muscle-specific proteins on the structural arrangement of α1S intracellular loops and point to a new conformational effect of the β1a subunit in supporting skeletal muscle excitation-contraction coupling. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  9. Fluorescence Resonance Energy Transfer-based Structural Analysis of the Dihydropyridine Receptor α1S Subunit Reveals Conformational Differences Induced by Binding of the β1a Subunit*

    PubMed Central

    Mahalingam, Mohana; Perez, Claudio F.; Fessenden, James D.

    2016-01-01

    The skeletal muscle dihydropyridine receptor α1S subunit plays a key role in skeletal muscle excitation-contraction coupling by sensing membrane voltage changes and then triggering intracellular calcium release. The cytoplasmic loops connecting four homologous α1S structural domains have diverse functions, but their structural arrangement is poorly understood. Here, we used a novel FRET-based method to characterize the relative proximity of these intracellular loops in α1S subunits expressed in intact cells. In dysgenic myotubes, energy transfer was observed from an N-terminal-fused YFP to a FRET acceptor, ReAsH (resorufin arsenical hairpin binder), targeted to each α1S intracellular loop, with the highest FRET efficiencies measured to the α1S II-III loop and C-terminal tail. However, in HEK-293T cells, FRET efficiencies from the α1S N terminus to the II-III and III-IV loops and the C-terminal tail were significantly lower, thus suggesting that these loop structures are influenced by the cellular microenvironment. The addition of the β1a dihydropyridine receptor subunit enhanced FRET to the II-III loop, thus indicating that β1a binding directly affects II-III loop conformation. This specific structural change required the C-terminal 36 amino acids of β1a, which are essential to support EC coupling. Direct FRET measurements between α1S and β1a confirmed that both wild type and truncated β1a bind similarly to α1S. These results provide new insights into the role of muscle-specific proteins on the structural arrangement of α1S intracellular loops and point to a new conformational effect of the β1a subunit in supporting skeletal muscle excitation-contraction coupling. PMID:27129199

  10. The effect of solvation on vertical ionization energy of thymine: from microhydration to bulk

    PubMed Central

    Ghosh, Debashree; Isayev, Olexandr; Slipchenko, Lyudmila V.; Krylov, Anna I.

    2011-01-01

    The effect of hydration on the vertical ionization energy (VIE) of thymine was characterized using equation-of-motion ionization potential coupled-cluster (EOM-IP-CCSD) and effective fragment potential (EFP) methods. We considered several microsolvated clusters as well as thymine solvated in bulk water. The VIE in bulk water was computed by averaging over solvent-solute configurations obtained from equilibrium MD trajectories at 300 K. The effect of microsolvation was analyzed and contrasted against the combined effect of the first solvation shell in bulk water. Microsolvation reduces the ionization energy (IE) by about 0.1 eV per water molecule while the first solvation shell increases the IE by 0.1 eV. The subsequent solvation lowers the IE, and the bulk value of the solvent-induced shift of thymine’s VIE is approximately −0.9 eV. The combined effect of the first solvation shell was explained in terms of specific solute-solvent interactions, which were investigated using model geometries. The convergence of IE to the bulk value requires the hydration sphere of approximately 13.5 Å radius. The performance of the EOM-IP-CCSD/EFP scheme was benchmarked against full EOM-IP-CCSD using microhydrated structures. The errors were found to be less than 0.01–0.02 eV. The relative importance of the polarization and higher multipole moments in EFP model was also investigated. PMID:21500795

  11. Free-air ionization chamber, FAC-IR-300, designed for medium energy X-ray dosimetry

    NASA Astrophysics Data System (ADS)

    Mohammadi, S. M.; Tavakoli-Anbaran, H.; Zeinali, H. Z.

    2017-01-01

    The primary standard for X-ray photons is based on parallel-plate free-air ionization chamber (FAC). Therefore, the Atomic Energy Organization of Iran (AEOI) is tried to design and build the free-air ionization chamber, FAC-IR-300, for low and medium energy X-ray dosimetry. The main aim of the present work is to investigate specification of the FAC-IR-300 ionization chamber and design it. FAC-IR-300 dosimeter is composed of two parallel plates, a high voltage (HV) plate and a collector plate, along with a guard electrode that surrounds the collector plate. The guard plate and the collector were separated by an air gap. For obtaining uniformity in the electric field distribution, a group of guard strips was used around the ionization chamber. These characterizations involve determining the exact dimensions of the ionization chamber by using Monte Carlo simulation and introducing correction factors.

  12. Spectrum and energy levels of five-times ionized zirconium (Zr VI)

    NASA Astrophysics Data System (ADS)

    Reader, Joseph; Lindsay, Mark D.

    2016-02-01

    We carried out a new analysis of the spectrum of five-times-ionized zirconium Zr VI. For this we used sliding-spark discharges together with normal- and grazing-incidence spectrographs to observe the spectrum from 160 to 2000 Å. These observations showed that the analysis of this spectrum by Khan et al (1985 Phys. Scr. 31 837) contained a significant number of incorrect energy levels. We have now classified ˜420 lines as transitions between 23 even-parity levels 73 odd-parity levels. The 4s24p5, 4s4p6, 4s24p44d, 5s, 5d, 6s configurations are now complete, although a few levels of 4s24p45d are tentative. We determined Ritz-type wavelengths for ˜135 lines from the optimized energy levels. The uncertainties range from 0.0003 to 0.0020 Å. Hartree-Fock calculations and least-squares fits of the energy parameters to the observed levels were used to interpret the observed configurations. Oscillator strengths for all classified lines were calculated with the fitted parameters. The results are compared with values for the level energies, percentage compositions, and transition probabilities from recent ab initio theoretical calculations. The ionization energy was revised to 777 380 ± 300 cm-1 (96.38 ± 0.04 eV).

  13. Comparison of plasma excitation, ionization, and energy influx in single and dual frequency capacitive discharges

    NASA Astrophysics Data System (ADS)

    Sahu, B. B.; Han, Jeon G.

    2016-12-01

    Argon (Ar) plasma characteristics in a single and dual-frequency (DF), capacitively coupled plasma processing system are compared for drive frequencies 13.56 MHz, 320 MHz and their mixture as dual frequencies (DF). We present frequency dependent changes that occur in discharges in terms of plasma parameters such as plasma density, electron temperature, electron energy distribution function, optical emission, gas temperature, and metastable Ar density in a pressure range of 10-150 mTorr. Additionally, this work also presents the formulation and characterization of energy fluxes from plasma to a substrate/probe during the plasma generation. By variation of the operating pressure and plasma excitation frequency, the different contributions originating from the kinetic energy, the recombination of charge carriers such as electrons and ions at the surface along with the contributions from the neutral and excited species are determined. Data reveals that Ar metastable density in low-frequency radio frequency (RF) plasma is not a strong function of operating pressure even though plasma ionization increases with pressure. However, in the case of high-frequency and DF, the excitation of Ar metastable decreases and ionization increases due to enhanced collisions and efficient electron-neutral momentum/energy transfer. Also, data reveals that energy flux in the low-frequency RF plasmas is very high compared to that of high-frequency and DF operations.

  14. High-kinetic-energy photoemission spectroscopy of Ni at 1s : 6-eV satellite at 4 eV

    NASA Astrophysics Data System (ADS)

    Karis, O.; Svensson, S.; Rusz, J.; Oppeneer, P. M.; Gorgoi, M.; Schäfers, F.; Braun, W.; Eberhardt, W.; Mårtensson, N.

    2008-12-01

    Electron correlations are responsible for many profound phenomena in solid-state physics. A classical example is the 6-eV satellite in the photoelectron spectrum of Ni. Until now the satellite structure has only been investigated at the L shell and more shallow levels. Here we report a high-kinetic-energy photoemission spectroscopy (HIKE) investigation of Ni metal. We present 1s and 2p photoelectron spectra, obtained using excitation energies up to 12.6 keV. Our investigation demonstrates that the energy position of the satellite relative to the main line is different for the 1s and the 2p levels. In combination with electronic structure calculations, we show that this energy shift is attributed to unique differences in the core-valence coupling for the K and L2,3 shells in 3d transition metals, resulting in different screening of the core holes.

  15. A VUV Photoionization and Ab Initio Determination of the Ionization Energy of a Gas-Phase Sugar (Deoxyribose).

    PubMed

    Ghosh, Debashree; Golan, Amir; Takahashi, Lynelle K; Krylov, Anna I; Ahmed, Musahid

    2012-01-05

    The ionization energy of gas-phase deoxyribose was determined using tunable vacuum ultraviolet synchrotron radiation coupled to an effusive thermal source. Adiabatic and vertical ionization energies of the ground and first four excited states of α-pyranose, the structure that dominates in the gas phase, were calculated using high-level electronic structure methods. An appearance energy of 9.1(±0.05) eV was recorded, which agrees reasonably well with a theoretical value of 8.8 eV for the adiabatic ionization energy. A clear picture of the dissociative photoionization dynamics of deoxyribose emerges from the fragmentation pattern recorded using mass spectrometry and from ab initio molecular dynamics calculations. The experimental threshold 9.4 (±0.05) eV for neutral water elimination upon ionization is captured well in the calculations, and qualitative insights are provided by molecular orbital analysis and molecular dynamics snapshots along the reaction coordinate.

  16. Influence of energy pooling and ionization on physical features of a diode-pumped alkali laser.

    PubMed

    An, Guofei; Wang, You; Han, Juhong; Cai, He; Zhou, Jie; Zhang, Wei; Xue, Liangping; Wang, Hongyuan; Gao, Ming; Jiang, Zhigang

    2015-10-05

    In recent years, a diode-pumped alkali laser (DPAL) has become one of the most hopeful candidates to achieve the high power performance. A series of models have been established to analyze the DPAL's kinetic process and most of them were based on the algorithms in which only the ideal 3-level system was considered. In this paper, we developed a systematic model by taking into account the influence of excitation of neutral alkali atoms to even-higher levels and their ionization on the physical features of a static DPAL. The procedures of heat transfer and laser kinetics were combined together in our theoretical model. By using such a theme, the continuous temperature and number density distribution have been evaluated in the transverse section of a cesium vapor cell. The calculated results indicate that both energy pooling and ionization play important roles during the lasing process. The conclusions might deepen the understanding of the kinetic mechanism of a DPAL.

  17. The energy and momentum input of supernova explosions in structured and ionized molecular clouds

    NASA Astrophysics Data System (ADS)

    Walch, Stefanie; Naab, Thorsten

    2015-08-01

    We investigate the early impact of single and binary supernova (SN) explosions on dense gas clouds with three-dimensional, high-resolution, hydrodynamic simulations. The effect of cloud structure, radiative cooling and ionizing radiation from the progenitor stars on the net input of kinetic energy, fkin = Ekin/ESN, thermal energy, ftherm = Etherm/ESN, and gas momentum, fP = P/PSN, to the interstellar medium (ISM) is tested. For clouds with bar{n} = 100cm^{-3}, the momentum generating Sedov and pressure-driven snowplough phases are terminated early (∝0.01 Myr) and radiative cooling limits the coupling to ftherm ˜ 0.01, fkin ˜ 0.05, and fP ˜ 9, significantly lower than for the case without cooling. For pre-ionized clouds, these numbers are only increased by ˜50 per cent, independent of the cloud structure. This only suffices to accelerate ˜5 per cent of the cloud to radial velocities ≳30 km s-1. A second SN might enhance the coupling efficiencies if delayed past the Sedov phase of the first explosion. Such very low coupling efficiencies cast doubts on many subresolution models for SN feedback, which are, in general, validated a posteriori. Ionizing radiation appears not to significantly enhance the coupling of SNe to the surrounding gas as it drives the ISM into inert dense shells and cold clumps, a process which is unresolved in galaxy-scale simulations. Our results indicate that the momentum input of SNe in ionized, structured clouds is larger (more than a factor of 10) than the corresponding momentum yield of the progenitor's stellar winds.

  18. Communication: Importance of rotationally inelastic processes in low-energy Penning ionization of CHF3.

    PubMed

    Jankunas, Justin; Jachymski, Krzysztof; Hapka, Michał; Osterwalder, Andreas

    2016-06-14

    Low energy reaction dynamics can strongly depend on the internal structure of the reactants. The role of rotationally inelastic processes in cold collisions involving polyatomic molecules has not been explored so far. Here we address this problem by performing a merged-beam study of the He((3)S1)+CHF3 Penning ionization reaction in a range of collision energies E/kB = 0.5-120 K. The experimental cross sections are compared with total reaction cross sections calculated within the framework of quantum defect theory. We find that the broad range of collision energies combined with the relatively small rotational constants of CHF3 makes rotationally inelastic collisions a crucial player in the total reaction dynamics. Quantitative agreement between theory and experiment is only obtained if the energy-dependent probability for rotational excitation is included in the calculations, in stark contrast to previous experiments where classical scaling laws were able to describe the results.

  19. Communication: Importance of rotationally inelastic processes in low-energy Penning ionization of CHF3

    NASA Astrophysics Data System (ADS)

    Jankunas, Justin; Jachymski, Krzysztof; Hapka, Michał; Osterwalder, Andreas

    2016-06-01

    Low energy reaction dynamics can strongly depend on the internal structure of the reactants. The role of rotationally inelastic processes in cold collisions involving polyatomic molecules has not been explored so far. Here we address this problem by performing a merged-beam study of the He(3S1)+CHF3 Penning ionization reaction in a range of collision energies E/kB = 0.5-120 K. The experimental cross sections are compared with total reaction cross sections calculated within the framework of quantum defect theory. We find that the broad range of collision energies combined with the relatively small rotational constants of CHF3 makes rotationally inelastic collisions a crucial player in the total reaction dynamics. Quantitative agreement between theory and experiment is only obtained if the energy-dependent probability for rotational excitation is included in the calculations, in stark contrast to previous experiments where classical scaling laws were able to describe the results.

  20. Theoretical study of energy deposition in ionization chambers for tritium measurements

    SciTech Connect

    Chen, Zhilin; Peng, Shuming; Meng, Dan; He, Yuehong; Wang, Heyi

    2013-10-15

    Energy deposition in ionization chambers has been theoretically studied for tritium measurements in gaseous form. A one-dimension model is introduced to establish the quantitative relationship between energy deposition rate and many factors, including carrier gas, gas pressure, wall material, chamber size, and gas temperature. Energy deposition rate has been calculated at pressure varying from 5 kPa to 500 kPa based on some approximations. It is found that energy deposition rate varies greatly for different parameters, especially at low gas pressure. For the same chamber, energy deposition rate in argon is much higher than in deuterium, as much as 70.7% higher at 5 kPa. Gold plated chamber gives highest energy deposition rate in the calculations while aluminum chamber results in the lowest. As chamber size gets smaller, β ray emitted by tritium will deposit less energy in the sensitive region of the chamber. For chambers flowing through with the same gas, energy deposition rate in a 10 L chamber is 23.9% higher than in a 0.05 L chamber at 5 kPa. Gas temperature also places slight influence on energy deposition rate, and 373 K will lead to 6.7% lower deposition rate than 233 K at 5 kPa. In addition, experiments have been performed to obtain energy deposition rate in a gold plated chamber, which show good accordance with theoretical calculations.

  1. Theoretical study of energy deposition in ionization chambers for tritium measurements

    NASA Astrophysics Data System (ADS)

    Chen, Zhilin; Peng, Shuming; Meng, Dan; He, Yuehong; Wang, Heyi

    2013-10-01

    Energy deposition in ionization chambers has been theoretically studied for tritium measurements in gaseous form. A one-dimension model is introduced to establish the quantitative relationship between energy deposition rate and many factors, including carrier gas, gas pressure, wall material, chamber size, and gas temperature. Energy deposition rate has been calculated at pressure varying from 5 kPa to 500 kPa based on some approximations. It is found that energy deposition rate varies greatly for different parameters, especially at low gas pressure. For the same chamber, energy deposition rate in argon is much higher than in deuterium, as much as 70.7% higher at 5 kPa. Gold plated chamber gives highest energy deposition rate in the calculations while aluminum chamber results in the lowest. As chamber size gets smaller, β ray emitted by tritium will deposit less energy in the sensitive region of the chamber. For chambers flowing through with the same gas, energy deposition rate in a 10 L chamber is 23.9% higher than in a 0.05 L chamber at 5 kPa. Gas temperature also places slight influence on energy deposition rate, and 373 K will lead to 6.7% lower deposition rate than 233 K at 5 kPa. In addition, experiments have been performed to obtain energy deposition rate in a gold plated chamber, which show good accordance with theoretical calculations.

  2. Use of relativistic rise in ionization chambers for measurement of high energy heavy nuclei

    NASA Technical Reports Server (NTRS)

    Barthelmy, S. D.; Israel, M. H.; Klarmann, J.; Vogel, J. S.

    1983-01-01

    A balloon-borne instrument has been constructed to measure the energy spectra of cosmic-ray heavy nuclei in the range of about 0.3 to about 100 GeV/amu. It makes use of the relativistic rise portion of the Bethe-Bloch curve in ionization chambers for energy determination in the 10- to 100-GeV/amu interval. The instrument consists of six layers of dual-gap ionization chambers for energy determination above 10 GeV/amu. Charge is determined with a NE114 scintillator and a Pilot 425 plastic Cerenkov counter. A CO2 gas Cerenkov detector (1 atm; threshold of 30 GeV/amu) calibrates the ion chambers in the relativistic rise region. The main emphasis of the instrument is the determination of the change of the ratio of Iron (26) to the Iron secondaries (21-25) in the energy range of 10 to 100 GeV/amu. Preliminary data from a balloon flight in the fall of 1982 from Palestine, TX is presented.

  3. Hardness assurance for proton direct ionization-induced SEEs using a high-energy proton beam

    SciTech Connect

    Dodds, Nathaniel Anson; Schwank, James R.; Shaneyfelt, Marty R.; Dodd, Paul E.; Doyle, Barney Lee; Trinczek, M.; Blackmore, E. W.; Rodbell, K. P.; Reed, R. A.; Pellish, J. A.; LaBel, K. A.; Marshall, P. W.; Swanson, Scot E.; Vizkelethy, Gyorgy; Van Deusen, Stuart B.; Sexton, Frederick W.; Martinez, Marino J.; Gordon, M. S.

    2014-11-06

    The low-energy proton energy spectra of all shielded space environments have the same shape. This shape is easily reproduced in the laboratory by degrading a high-energy proton beam, producing a high-fidelity test environment. We use this test environment to dramatically simplify rate prediction for proton direct ionization effects, allowing the work to be done at high-energy proton facilities, on encapsulated parts, without knowledge of the IC design, and with little or no computer simulations required. Proton direct ionization (PDI) is predicted to significantly contribute to the total error rate under the conditions investigated. Scaling effects are discussed using data from 65-nm, 45-nm, and 32-nm SOI SRAMs. These data also show that grazing-angle protons will dominate the PDI-induced error rate due to their higher effective LET, so PDI hardness assurance methods must account for angular effects to be conservative. As a result, we show that this angular dependence can be exploited to quickly assess whether an IC is susceptible to PDI.

  4. Use of relativistic rise in ionization chambers for measurement of high energy heavy nuclei

    NASA Technical Reports Server (NTRS)

    Barthelmy, S. D.; Israel, M. H.; Klarmann, J.; Vogel, J. S.

    1983-01-01

    A balloon-borne instrument has been constructed to measure the energy spectra of cosmic-ray heavy nuclei in the range of about 0.3 to about 100 GeV/amu. It makes use of the relativistic rise portion of the Bethe-Bloch curve in ionization chambers for energy determination in the 10- to 100-GeV/amu interval. The instrument consists of six layers of dual-gap ionization chambers for energy determination above 10 GeV/amu. Charge is determined with a NE114 scintillator and a Pilot 425 plastic Cerenkov counter. A CO2 gas Cerenkov detector (1 atm; threshold of 30 GeV/amu) calibrates the ion chambers in the relativistic rise region. The main emphasis of the instrument is the determination of the change of the ratio of Iron (26) to the Iron secondaries (21-25) in the energy range of 10 to 100 GeV/amu. Preliminary data from a balloon flight in the fall of 1982 from Palestine, TX is presented.

  5. Hardness assurance for proton direct ionization-induced SEEs using a high-energy proton beam

    DOE PAGES

    Dodds, Nathaniel Anson; Schwank, James R.; Shaneyfelt, Marty R.; ...

    2014-11-06

    The low-energy proton energy spectra of all shielded space environments have the same shape. This shape is easily reproduced in the laboratory by degrading a high-energy proton beam, producing a high-fidelity test environment. We use this test environment to dramatically simplify rate prediction for proton direct ionization effects, allowing the work to be done at high-energy proton facilities, on encapsulated parts, without knowledge of the IC design, and with little or no computer simulations required. Proton direct ionization (PDI) is predicted to significantly contribute to the total error rate under the conditions investigated. Scaling effects are discussed using data frommore » 65-nm, 45-nm, and 32-nm SOI SRAMs. These data also show that grazing-angle protons will dominate the PDI-induced error rate due to their higher effective LET, so PDI hardness assurance methods must account for angular effects to be conservative. As a result, we show that this angular dependence can be exploited to quickly assess whether an IC is susceptible to PDI.« less

  6. Complex time contours in tunnel ionization and low-energy structures

    NASA Astrophysics Data System (ADS)

    Pisanty, Emilio; Ivanov, Misha

    2015-03-01

    In tunnel ionization, a strong low-frequency laser field removes an electron from an atom by setting up a slowly-varying potential energy barrier that the electron can tunnel through. During its subsequent oscillations in the laser field, the electron can revisit the neighbourhood of the remaining ion one or more times. Frequently, this is a soft recollision which affects the momentum distribution, although more substantial effects can happen. We use the Analytical R-Matrix theory to investigate the effect of these soft recollisions, focusing on low drift momenta, where the laser-induced trajectory has a turning point near the nucleus. Our framework provides a complex-valued trajectory perspective on the electron propagation, from first principles. We show that the presence of the Coulomb interaction, which is responsible for the soft recollisions, forbids certain common choices of contour within the complex time plane, and we describe an algorithm for safely circumventing the associated branch cuts. We find quantum analogues to the classical turning points near the ion, and we investigate their relation to the recently-discovered low-energy and very-low-energy structures in above-threshold ionization. We acknowledge funding from CONACYT (Mexico) and the MC-ITN CORINF network.

  7. An equation of state for partially ionized plasmas: The Coulomb contribution to the free energy

    NASA Astrophysics Data System (ADS)

    Kilcrease, D. P.; Colgan, J.; Hakel, P.; Fontes, C. J.; Sherrill, M. E.

    2015-09-01

    We have previously developed an equation of state (EOS) model called ChemEOS (Hakel and Kilcrease, Atomic Processes in Plasmas, Eds., J. Cohen et al., AIP, 2004) for a plasma of interacting ions, atoms and electrons. It is based on a chemical picture of the plasma and is derived from an expression for the Helmholtz free energy of the interacting species. All other equilibrium thermodynamic quantities are then obtained by minimizing this free energy subject to constraints, thus leading to a thermodynamically consistent EOS. The contribution to this free energy from the Coulomb interactions among the particles is treated using the method of Chabrier and Potekhin (Phys. Rev. E 58, 4941 (1998)) which we have adapted for partially ionized plasmas. This treatment is further examined and is found to give rise to unphysical behavior for various elements at certain values of the density and temperature where the Coulomb coupling begins to become significant and the atoms are partially ionized. We examine the source of this unphysical behavior and suggest corrections that produce acceptable results. The sensitivity of the thermodynamic properties and frequency-dependent opacity of iron is examined with and without these corrections. The corrected EOS is used to determine the fractional ion populations and level populations for a new generation of OPLIB low-Z opacity tables currently being prepared at Los Alamos National Laboratory with the ATOMIC code.

  8. Mass separation of deuterium and helium with conventional quadrupole mass spectrometer by using varied ionization energy

    SciTech Connect

    Yu, Yaowei; Hu, Jiansheng Wan, Zhao; Wu, Jinhua; Wang, Houyin; Cao, Bin

    2016-03-15

    Deuterium pressure in deuterium-helium mixture gas is successfully measured by a common quadrupole mass spectrometer (model: RGA200) with a resolution of ∼0.5 atomic mass unit (AMU), by using varied ionization energy together with new developed software and dedicated calibration for RGA200. The new software is developed by using MATLAB with the new functions: electron energy (EE) scanning, deuterium partial pressure measurement, and automatic data saving. RGA200 with new software is calibrated in pure deuterium and pure helium 1.0 × 10{sup −6}–5.0 × 10{sup −2} Pa, and the relation between pressure and ion current of AMU4 under EE = 25 eV and EE = 70 eV is obtained. From the calibration result and RGA200 scanning with varied ionization energy in deuterium and helium mixture gas, both deuterium partial pressures (P{sub D{sub 2}}) and helium partial pressure (P{sub He}) could be obtained. The result shows that deuterium partial pressure could be measured if P{sub D{sub 2}} > 10{sup −6} Pa (limited by ultimate pressure of calibration vessel), and helium pressure could be measured only if P{sub He}/P{sub D{sub 2}} > 0.45, and the measurement error is evaluated as 15%. This method is successfully employed in EAST 2015 summer campaign to monitor deuterium outgassing/desorption during helium discharge cleaning.

  9. An equation of state for partially ionized plasmas: The Coulomb contribution to the free energy

    SciTech Connect

    Kilcrease, D. P.; Colgan, J.; Hakel, P.; Fontes, C. J.; Sherrill, M. E.

    2015-06-20

    We have previously developed an equation of state (EOS) model called ChemEOS (Hakel and Kilcrease, Atomic Processes in Plasmas, Eds., J. Cohen et al., AIP, 2004) for a plasma of interacting ions, atoms and electrons. It is based on a chemical picture of the plasma and is derived from an expression for the Helmholtz free energy of the interacting species. All other equilibrium thermodynamic quantities are then obtained by minimizing this free energy subject to constraints, thus leading to a thermodynamically consistent EOS. The contribution to this free energy from the Coulomb interactions among the particles is treated using the method of Chabrier and Potekhin (Phys. Rev. E 58, 4941 (1998)) which we have adapted for partially ionized plasmas. This treatment is further examined and is found to give rise to unphysical behavior for various elements at certain values of the density and temperature where the Coulomb coupling begins to become significant and the atoms are partially ionized. We examine the source of this unphysical behavior and suggest corrections that produce acceptable results. The sensitivity of the thermodynamic properties and frequency-dependent opacity of iron is examined with and without these corrections. Lastly, the corrected EOS is used to determine the fractional ion populations and level populations for a new generation of OPLIB low-Z opacity tables currently being prepared at Los Alamos National Laboratory with the ATOMIC code.

  10. An equation of state for partially ionized plasmas: The Coulomb contribution to the free energy

    DOE PAGES

    Kilcrease, D. P.; Colgan, J.; Hakel, P.; ...

    2015-06-20

    We have previously developed an equation of state (EOS) model called ChemEOS (Hakel and Kilcrease, Atomic Processes in Plasmas, Eds., J. Cohen et al., AIP, 2004) for a plasma of interacting ions, atoms and electrons. It is based on a chemical picture of the plasma and is derived from an expression for the Helmholtz free energy of the interacting species. All other equilibrium thermodynamic quantities are then obtained by minimizing this free energy subject to constraints, thus leading to a thermodynamically consistent EOS. The contribution to this free energy from the Coulomb interactions among the particles is treated using themore » method of Chabrier and Potekhin (Phys. Rev. E 58, 4941 (1998)) which we have adapted for partially ionized plasmas. This treatment is further examined and is found to give rise to unphysical behavior for various elements at certain values of the density and temperature where the Coulomb coupling begins to become significant and the atoms are partially ionized. We examine the source of this unphysical behavior and suggest corrections that produce acceptable results. The sensitivity of the thermodynamic properties and frequency-dependent opacity of iron is examined with and without these corrections. Lastly, the corrected EOS is used to determine the fractional ion populations and level populations for a new generation of OPLIB low-Z opacity tables currently being prepared at Los Alamos National Laboratory with the ATOMIC code.« less

  11. Calculations of molecular ionization energies using a self-consistent-charge Hartree-Fock-Slater method

    NASA Technical Reports Server (NTRS)

    Rosen, A.; Ellis, D. E.; Adachi, H.; Averill, F. W.

    1976-01-01

    A numerical-variational method for performing self-consistent molecular calculations in the Hartree-Fock-Slater (HFS) model is presented. Molecular wavefunctions are expanded in terms of basis sets constructed from numerical HFS solutions of selected one-center atomlike problems. Binding energies and wavefunctions for the molecules are generated using a discrete variational method for a given molecular potential. In the self-consistent-charge (SCC) approximation to the complete self-consistent-field (SCF) method, results of a Mulliken population analysis of the molecular eigenfunctions are used in each iteration to produce 'atomic' occupation numbers. The simplest SCC potential is then obtained from overlapping spherical atomlike charge distributions. Molecular ionization energies are calculated using the transition-state procedure; results are given for CO, H2O, H2S, AlCl, InCl, and the Ni5O surface complex. Agreement between experimental and theoretical ionization energies for the free-molecule valence levels is generally within 1 eV. The simple SCC procedure gives a reasonably good approximation to the molecular potential, as shown by comparison with experiment, and with complete SCF calculations for CO, H2O, and H2S.

  12. Potential Energy Curves and Collisions Integrals of Air Components. 2; Interactions Involving Ionized Atoms

    NASA Technical Reports Server (NTRS)

    Stallcop, James R.; Partridge, Harry; Levin, Eugene; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    Collision integrals are fundamental quantities required to determine the transport properties of the environment surrounding aerospace vehicles in the upper atmosphere. These collision integrals can be determined as a function of temperature from the potential energy curves describing the atomic and molecular collisions. Ab initio calculations provide a practical method of computing the required interaction potentials. In this work we will discuss recent advances in scattering calculations with an emphasis on the accuracy that is obtainable. Results for interactions of the atoms and ionized atoms of nitrogen and oxygen will be reviewed and their application to the determination of transport properties, such as diffusion and viscosity coefficients, will be examined.

  13. COMPREHENSIVE OBSERVATIONS OF THE ULTRAVIOLET SPECTRUM AND IMPROVED ENERGY LEVELS FOR SINGLY IONIZED CHROMIUM (Cr II)

    SciTech Connect

    Sansonetti, Craig J.; Nave, Gillian; Reader, Joseph; Kerber, Florian

    2012-10-15

    We report new observations of the spectrum of singly ionized chromium (Cr II) in the region 1142-3954 A. The spectra were recorded with the National Institute of Standards and Technology 10.7 m normal-incidence vacuum spectrograph and FT700 vacuum ultraviolet Fourier transform spectrometer. More than 3600 lines are classified as transitions among 283 even and 368 odd levels. The new spectral data are used to re-optimize the energy levels, reducing their uncertainties by a typical factor of 20.

  14. Comprehensive Observations of the Ultraviolet Spectrum and Improved Energy Levels for Singly Ionized Chromium (Cr II)

    NASA Astrophysics Data System (ADS)

    Sansonetti, Craig J.; Nave, Gillian; Reader, Joseph; Kerber, Florian

    2012-10-01

    We report new observations of the spectrum of singly ionized chromium (Cr II) in the region 1142-3954 Å. The spectra were recorded with the National Institute of Standards and Technology 10.7 m normal-incidence vacuum spectrograph and FT700 vacuum ultraviolet Fourier transform spectrometer. More than 3600 lines are classified as transitions among 283 even and 368 odd levels. The new spectral data are used to re-optimize the energy levels, reducing their uncertainties by a typical factor of 20.

  15. Low-energy triple differential cross sections for electron-impact ionization of helium

    NASA Astrophysics Data System (ADS)

    Chen, Zhangjin; Zhang, Suimeng; Shi, Qicun; Chen, Ji; Xu, Kezun

    1997-11-01

    The BBK model is modified by the introduction of effective Sommerfeld parameters for both symmetric and asymmetric geometries on an empirical basis, while still maintaining the philosophy that all three Coulomb interactions are included on an equal footing. The triple differential cross sections for electron-impact ionization of atomic helium at an incident energy of 40 eV in an asymmetric geometry are calculated. Results of this approach are compared with the absolute measurements and the only existing theoretical results of the convergent close-coupling method.

  16. Quantitative analysis of molecular surfaces: areas, volumes, electrostatic potentials and average local ionization energies.

    PubMed

    Bulat, Felipe A; Toro-Labbé, Alejandro; Brinck, Tore; Murray, Jane S; Politzer, Peter

    2010-11-01

    We describe a procedure for performing quantitative analyses of fields f(r) on molecular surfaces, including statistical quantities and locating and evaluating their local extrema. Our approach avoids the need for explicit mathematical representation of the surface and can be implemented easily in existing graphical software, as it is based on the very popular representation of a surface as collection of polygons. We discuss applications involving the volumes, surface areas and molecular surface electrostatic potentials, and local ionization energies of a group of 11 molecules.

  17. Potential Energy Curves and Collisions Integrals of Air Components. 2; Interactions Involving Ionized Atoms

    NASA Technical Reports Server (NTRS)

    Stallcop, James R.; Partridge, Harry; Levin, Eugene; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    Collision integrals are fundamental quantities required to determine the transport properties of the environment surrounding aerospace vehicles in the upper atmosphere. These collision integrals can be determined as a function of temperature from the potential energy curves describing the atomic and molecular collisions. Ab initio calculations provide a practical method of computing the required interaction potentials. In this work we will discuss recent advances in scattering calculations with an emphasis on the accuracy that is obtainable. Results for interactions of the atoms and ionized atoms of nitrogen and oxygen will be reviewed and their application to the determination of transport properties, such as diffusion and viscosity coefficients, will be examined.

  18. Determination of Formation and Ionization Energies of Charged Defects in Two-Dimensional Materials

    NASA Astrophysics Data System (ADS)

    Wang, Dan; Han, Dong; Li, Xian-Bin; Xie, Sheng-Yi; Chen, Nian-Ke; Tian, Wei Quan; West, Damien; Sun, Hong-Bo; Zhang, S. B.

    2015-05-01

    We present a simple and efficient approach to evaluate the formation energy and, in particular, the ionization energy (IE) of charged defects in two-dimensional (2D) systems using the supercell approximation. So far, first-principles results for such systems can scatter widely due to the divergence of the Coulomb energy with vacuum dimension, denoted here as Lz . Numerous attempts have been made in the past to fix the problem under various approximations. Here, we show that the problem can be resolved without any such assumption, and a converged IE can be obtained by an extrapolation of the asymptotic IE expression at large Lz (with a fixed lateral area S ) back to the value at Lz=0 . Application to defects in monolayer boron nitride reveal that defects in 2D systems can be unexpectedly deep, much deeper than the bulk.

  19. The threshold photoelectron spectrum of cyanovinylacetylene leads to an upward revision of the ionization energy

    NASA Astrophysics Data System (ADS)

    Holzmeier, Fabian; Lang, Melanie; Fischer, Ingo; Hemberger, Patrick

    2015-10-01

    Cyanovinylacetylene C5H3N was investigated by threshold photoelectron spectroscopy. The ionization energy (IE) was determined to be 10.04 eV. This value constitutes an upward revision of the earlier value of 9.33 eV. For both stereoisomers (trans and cis) computations predict very similar IEs and spectra. At 11.08 eV and 11.17 eV excited cationic states are observed. For the precursor 3-bromopyridine an IE of 9.34 eV was obtained. The appearance energy AE0K (3-bromopyridine, 3-pyridyl+) was determined to be 11.71 eV and a bond dissociation energy of the Csbnd Br bond in the 3-bromopyridine cation of 229 kJ mol-1 was derived.

  20. Ab initio Study on Ionization Energies of 3-Amino-1-propanol

    NASA Astrophysics Data System (ADS)

    Wang, Ke-dong; Jia, Ying-bin; Lai, Zhen-jiang; Liu, Yu-fang

    2011-06-01

    Fourteen conformers of 3-amino-1-propanol as the minima on the potential energy surface are examined at the MP2/6-311++G** level. Their relative energies calculated at B3LYP, MP3 and MP4 levels of theory indicated that two most stable conformers display the intramolecular OH···N hydrogen bonds. The vertical ionization energies of these conformers calculated with ab initio electron propagator theory in the P3/aug-cc-pVTZ approximation are in agreement with experimental data from photoelectron spectroscopy. Natural bond orbital analyses were used to explain the differences of IEs of the highest occupied molecular ortibal of conformers. Combined with statistical mechanics principles, conformational distributions at various temperatures are obtained and the temperature dependence of photoelectron spectra is interpreted.

  1. Theoretical study of γ-aminobutyric acid conformers: Intramolecular interactions and ionization energies

    NASA Astrophysics Data System (ADS)

    Wang, Ke-Dong; Wang, Mei-Ting; Meng, Ju

    2014-10-01

    Allowing for all combinations of internal single-bond rotamers, 1,296 unique trial structures of γ-Aminobutyric acid (GABA) are obtained. All of these structures are optimized at the M06-2X level of theory and a total of 68 local minimal conformers are found. The nine low-lying conformers are used for further studies. According to the calculated relative Gibbs free energies at M06-2X level of theory, we find that the dispersion is important for the relative energy of GABA. The intramolecular hydrogen bonds and hyperconjugative interaction and their effects on the conformational stability are studied. The results show that both of them have great influence on the conformers. The vertical ionization energies (VIE) are calculated and match the experimental data well. The results show that the neutral GABA in the gas phase is a multi-conformer system and at least four conformations exist.

  2. An interaction energy driven biased sampling technique: A faster route to ionization spectra in condensed phase.

    PubMed

    Bose, Samik; Ghosh, Debashree

    2017-10-05

    We introduce a computationally efficient approach for calculating spectroscopic properties, such as ionization energies (IEs) in the condensed phase. Discrete quantum mechanical/molecular mechanical (QM/MM) approaches for spectroscopic properties in a dynamic system, such as aqueous solution, need a large sample space to obtain converged estimates, especially for the cases where particle (electron) number is not conserved, such as IEs or electron affinities (EAs). We devise a biased sampling technique based on an approximate estimate of interaction energy between the solute and solvent, that accelerates the convergence and therefore, reduces the computational cost significantly. The approximate interaction energy also provides a good measure of the spectral width of the chromophores in the condensed phase. This technique has been tested and benchmarked for (i) phenol, (ii) HBDI anion (hydroxybenzylidene dimethyl imidazolinone), and (iii) thymine in water. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  3. Radiation and ionization energy loss simulation for the GDH sum rule experiment in Hall-A at Jefferson Lab

    DOE PAGES

    Yan, Xin -Hu; Ye, Yun -Xiu; Chen, Jian -Ping; ...

    2015-07-17

    The radiation and ionization energy loss are presented for single arm Monte Carlo simulation for the GDH sum rule experiment in Hall-A at Jefferson Lab. Radiation and ionization energy loss are discussed formore » $$^{12}C$$ elastic scattering simulation. The relative momentum ratio $$\\frac{\\Delta p}{p}$$ and $$^{12}C$$ elastic cross section are compared without and with radiation energy loss and a reasonable shape is obtained by the simulation. The total energy loss distribution is obtained, showing a Landau shape for $$^{12}C$$ elastic scattering. This simulation work will give good support for radiation correction analysis of the GDH sum rule experiment.« less

  4. Radiation and ionization energy loss simulation for the GDH sum rule experiment in Hall-A at Jefferson Lab

    SciTech Connect

    Yan, Xin -Hu; Ye, Yun -Xiu; Chen, Jian -Ping; Lu, Hai -Jiang; Zhu, Peng -Jia; Jiang, Feng -Jian

    2015-07-17

    The radiation and ionization energy loss are presented for single arm Monte Carlo simulation for the GDH sum rule experiment in Hall-A at Jefferson Lab. Radiation and ionization energy loss are discussed for $^{12}C$ elastic scattering simulation. The relative momentum ratio $\\frac{\\Delta p}{p}$ and $^{12}C$ elastic cross section are compared without and with radiation energy loss and a reasonable shape is obtained by the simulation. The total energy loss distribution is obtained, showing a Landau shape for $^{12}C$ elastic scattering. This simulation work will give good support for radiation correction analysis of the GDH sum rule experiment.

  5. Manipulating internal energy of protonated biomolecules in electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Guo, Xinghua; Duursma, Marc C; Kistemaker, Piet G; Nibbering, Nico M M; Vekey, Karoly; Drahos, Laszlo; Heeren, Ron M A

    2003-06-01

    The internal energy of protonated leucine enkephalin has been manipulated in electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry with two newly designed pump-probe experiments. Blackbody infrared radiation was applied to pump an ion population into a well-defined internal energy distribution below the dissociation threshold. Following this pumping stage, the internal energy distribution was probed using on-resonance collisional activation to dissociate the ions. These pump-probe experiments were carried out in two different ways: (a) using on-resonance collisional activation with variable kinetic energies to dissociate the ions at a constant initial ion temperature (determining the precursor ion survival percentage as a function of kinetic energy) and (b) using on-resonance collisional activation with a constant kinetic energy to dissociate the ions at variable initial ion temperatures (to investigate the ion survival yield-initial ion temperature dependence). Using this approach, a detailed study of the effects of the initial ion temperature, the probing kinetic energy and the internal energy loss rate on the effective conversion efficiency of (laboratory-frame) kinetic energy to internal energy was conducted. This conversion efficiency was found to be dependent on the initial ion temperature. Depending on the experimental conditions the conversion efficiency (for collisions with argon) was estimated to be about 4.0 +/- 1.7%, which agrees with that obtained from a theoretical modeling. Finally, the reconstructed curves of the ion survival yield versus the mode of the (final) total internal energy distribution of the activated ion population (after pump and probe events) at different pump-probe conditions reveal the internal energy content of the activated ions. Copyright 2003 John Wiley & Sons, Ltd.

  6. K-shell ionization cross section of aluminium induced by low-energy highly charged argon ions

    NASA Astrophysics Data System (ADS)

    Chen, X. M.; Shao, J. X.; Yang, Z. H.; Zhang, H. Q.; Cui, Y.; Xu, X.; Xiao, G. Q.; Zhao, Y. T.; Zhang, X. A.; Zhang, Y. P.

    2007-02-01

    Al K-shell X-ray yields are measured with highly charged Arq+ ions (q=12 16) bombarding against aluminium. The energy range of the Ar ions is from 180 to 380 keV. K-shell ionization cross sections of aluminium are also obtained from the yields data. The experimental data is explained within the framework of 2pπ -2pσ rotational coupling. When Ar ions with 2p-shell vacancies are incident on aluminium, the vacancies begin to reduce. Meanwhile, collisions against Al atoms lead to the production of new 2p-shell vacancies of Ar ions. These Ar 2p-shell vacancies will transfer to the 1s orbit of an Al atom via 2pπ-2pσ rotational coupling leading to the emission of a K-shell X-ray of aluminiun. A model is constructed based on the base of the above physical scenario. The calculation results of the model are in agreement with the experimental results.

  7. Cross sections for ionization of tetrahydrofuran by protons at energies between 300 and 3000 keV

    NASA Astrophysics Data System (ADS)

    Wang, Mingjie; Rudek, Benedikt; Bennett, Daniel; de Vera, Pablo; Bug, Marion; Buhr, Ticia; Baek, Woon Yong; Hilgers, Gerhard; Rabus, Hans

    2016-05-01

    Double-differential cross sections for ionization of tetrahydrofuran by protons with energies from 300 to 3000 keV were measured at the Physikalisch-Technische Bundesanstalt ion accelerator facility. The electrons emitted at angles between 15∘ and 150∘ relative to the ion-beam direction were detected with an electrostatic hemispherical electron spectrometer. Single-differential and total ionization cross sections have been derived by integration. The experimental results are compared to the semiempirical Hansen-Kocbach-Stolterfoht model as well as to the recently reported method based on the dielectric formalism. The comparison to the latter showed good agreement with experimental data in a broad range of emission angles and energies of secondary electrons. The scaling property of ionization cross sections for tetrahydrofuran was also investigated. Compared to molecules of different size, the ionization cross sections of tetrahydrofuran were found to scale with the number of valence electrons at large impact parameters.

  8. Energy and momentum correlation in dissociative ionization D2 by 1 MeV/u F^8+ ions*

    NASA Astrophysics Data System (ADS)

    Landers, A. L.; Robison, A.; Naser, A. Al; Tanis, J. A.; Wells, E.; Osipov, T.; Carnes, K. D.; Ben-Itzhak, I.; Cocke, C. L.

    2003-05-01

    Dissociative ionization of D2 molecules by 19 MeV F^8+ ions was studied using an imaging technique. We have measured in coincidence the vector momentum of at least one molecule fragment and one electron produced in these ionizing collisions. Measurement of the molecule fragment(s) yields both the alignment at the time of the collision and the final dissociation energy. In addition to previous results that indicate the double-ionization cross section has an unexpectedly strong dependence on molecular orientation, we have new evidence of states populated by double excitation which ultimately decay to the disscociative single ionization channel. Further investigations include the dependence of this doubly excited state upon molecule orientation and electron emission in the fixed molecule frame. *Supported by U.S. Department of Energy

  9. Direct determination of the ionization energies of FeO and CuO with VUV radiation.

    PubMed

    Metz, Ricardo B; Nicolas, Christophe; Ahmed, Musahid; Leone, Stephen R

    2005-09-15

    Photoionization efficiency curves were measured for gas-phase FeO and CuO using tunable vacuum-ultraviolet radiation at the Advanced Light Source. The molecules are prepared using laser ablation of a metal-oxide powder in a novel high-repetition-rate source and are thermally moderated in a supersonic expansion. These measurements provide the first directly measured ionization energy for CuO, IE(CuO)=9.41 +/- 0.01 eV. The direct measurement also gives a greatly improved ionization energy for FeO, IE(FeO) = 8.56 +/- 0.01 eV. The ionization energy connects the dissociation energies of the neutral and cation, leading to a refined bond strength for the FeO cation: D0(Fe(+)-O)=3.52 +/- 0.02 eV. A dramatic increase in the photoionization cross section at energies of 0.36 eV above the threshold ionization energy is assigned to autoionization and direct ionization involving one or more low-lying quartet states of FeO+. The interaction between the sextet ground state and low-lying quartet states of FeO+ is key to understanding the oxidation of hydrogen and methane by FeO+, and these experiments provide the first experimental observation of the low-lying quartet states of FeO+.

  10. Inhibition of G{sub 1}-phase arrest induced by ionizing radiation in hematopoietic cells by overexpression of genes involved in the G{sub 1}/S-phase transition

    SciTech Connect

    Epperly, M.; Berry, L.; Halloran, A.; Greenberger, J.S. |

    1995-09-01

    D-type cyclins and cyclin-dependent kinase (cdk-4) are likely involved in regulating passage of cells through the G{sub 1} phase of the cell cycle. A decrease in the proportion of cells in G{sub 1}, a relatively radiation-sensitive phase of the cell cycle, should result in increased resistance to ionizing radiation; however, the effect of such overexpression on X-ray-induced G{sub 1}-phase arrest is not known. Radiation survival curves were obtained at a dose rate of either 8 cGy/min or 1 Gy/min for subclones of the IL-3-dependent hematopoietic progenitor cell line 32D cl 3 expressing transgenes for either cyclin-D1, D2 or D3 or cdk-4. We compared the results to those with overexpression of the transgene for Bcl-2, whose expression enhances radiation survival and delays apoptosis. Cells overexpressing transgenes for each D-type cyclin or Bcl-2 had an increased number of cells in S phase compared to parent line 32D cl 3; however, overexpression of cdk-4 had no effect on cell cycle distribution. Cell death resulting from withdrawal of IL-3 was not affected by overexpression of D2, cdk-4 or Bcl-2. Flow cytometry 24 h after 5 Gy irradiation demonstrated that overexpression of each G{sub 1}-phase regulatory transgene decreased the proportion of cells at the G{sub 1}/S-phase border. Western analysis revealed induction of cyclin-D protein levels by irradiation, but no change in the D{sub O}, but a significant increase in the {rvec n} for cyclin-D or cdk-4 transgene-overexpressing clones at 1 Gy/min (P<0.017). At a lower dose rate of 8 cGy/min, the {rvec n} for cyclin or cdk-4-overexpressing clones was also increased (P<0.7). Thus overexpression of cyclin-D or cdk-4 in hematopoietic cells induces detectable effects on hematopoietic cell radiation biology including a broadening of the shoulder on the radiation survival curve and a decrease in radiation-induced G{sub 1}/S-phase arrest. 31 refs., 4 figs., 4 tabs.

  11. Potential Energy Surfaces of Core-Hole and Shake-Up States for Dissociative Ionization Studies.

    PubMed

    Corral, Inés; González-Vázquez, Jesús; Martín, Fernando

    2017-04-11

    The theoretical description of core-hole and core-hole excited (shake-up) states resulting from the interaction of a molecule with X-ray free-electron lasers, attosecond pulses, and synchrotron radiation is a challenging task, as these states lie in the ionization continuum and, therefore, are subject to variational collapse. Although much effort has been devoted in the past to describe core-hole states in the Franck-Condon (FC) region, very few attempts, even less for shake-up states, have been reported near the dissociation threshold, where multistate degeneracy introduces additional complications. Knowledge of the whole potential energy surface (PES) is, however, essential when dissociative ionization resulting from the interaction with XUV or X-ray light occurs. In this work, we gauge the accuracy of two widely used multiconfigurational methods, CASSCF and MRCI, to obtain the potential energy curves of core-hole states of CO, N2, and the small polyatomic molecule BF3, from the FC region up to the dissociation limit, and show that CASSCF in combination with a triple-ζ basis set provides a very reasonable compromise between accuracy and computational cost to correctly describe core-hole and shake-up states in the entire PES. Besides providing the vibrational spectroscopic constants associated with these states, we also analyze the corresponding bonding and dissociation properties, which, in some cases, are counterintuitive and significantly different from those of bound states.

  12. Direct Determination of the Ionization Energies of PtC, PtO, and PtO2 with VUVRadiation

    SciTech Connect

    Citir, Murat; Metz, Ricardo B.; Belau, Leonid; Ahmed, Musahid

    2008-07-21

    Photoionization efficiency curves were measured for gas-phase PtC, PtO, and PtO2 using tunable vacuum ultraviolet (VUV) radiation at the Advanced Light Source. The molecules were prepared by laser ablation of a platinum tube, followed by reaction with CH4 or N2O and supersonic expansion. These measurements providethe first directly measured ionization energy for PtC, IE(PtC) = 9.45 +- 0.05 eV. The direct measurement also gives greatly improved ionization energies for the platinum oxides, IE(PtO) = 10.0 +- 0.1 eV and IE(PtO2) = 11.35 +- 0.05 eV. The ionization energy connects the dissociation energies of the neutral and cation, leading to greatly improved 0 K bond dissociation energies for the neutrals: D0(Pt-C) = 5.95 +- 0.07 eV, D0(Pt-O)= 4.30 +- 0.12 eV, and D0(OPt-O) = 4.41 +- 0.13 eV, as well as enthalpies of formation for the gas-phase molecules Delta H0 f,0(PtC(g)) = 701 +- 7 kJ/mol, Delta H0f,0(PtO(g)) = 396 +- 12 kJ/mol, and Delta H0f,0(PtO2(g)) = 218 +- 11 kJ/mol. Much of the error in previous Knudsen cell measurements of platinum oxide bond dissociation energies is due to the use of thermodynamic second law extrapolations. Third law values calculated using statistical mechanical thermodynamic functions are in much better agreement with values obtained from ionization energies and ion energetics. These experiments demonstrate that laser ablation production with direct VUV ionization measurements is a versatile tool to measure ionization energies and bond dissociation energies for catalytically interesting species such as metal oxides and carbides.

  13. Displacement damage and predicted non-ionizing energy loss in GaAs

    NASA Astrophysics Data System (ADS)

    Gao, Fei; Chen, Nanjun; Hernandez-Rivera, Efrain; Huang, Danhong; LeVan, Paul D.

    2017-03-01

    Large-scale molecular dynamics (MD) simulations, along with bond-order interatomic potentials, have been applied to study the defect production for lattice atom recoil energies from 500 eV to 20 keV in gallium arsenide (GaAs). At low energies, the most surviving defects are single interstitials and vacancies, and only 20% of the interstitial population is contained in clusters. However, a direct-impact amorphization in GaAs occurs with a high degree of probability during the cascade lifetime for Ga PKAs (primary knock-on atoms) with energies larger than 2 keV. The results reveal a non-linear defect production that increases with the PKA energy. The damage density within a cascade core is evaluated, and used to develop a model that describes a new energy partition function. Based on the MD results, we have developed a model to determine the non-ionizing energy loss (NIEL) in GaAs, which can be used to predict the displacement damage degradation induced by space radiation on electronic components. The calculated NIEL predictions are compared with the available data, thus validating the NIEL model developed in this study.

  14. Lookup tables to compute high energy cosmic ray induced atmospheric ionization and changes in atmospheric chemistry

    SciTech Connect

    Atri, Dimitra; Melott, Adrian L.; Thomas, Brian C. E-mail: melott@ku.edu

    2010-05-01

    A variety of events such as gamma-ray bursts and supernovae may expose the Earth to an increased flux of high-energy cosmic rays, with potentially important effects on the biosphere. Existing atmospheric chemistry software does not have the capability of incorporating the effects of substantial cosmic ray flux above 10 GeV. An atmospheric code, the NASA-Goddard Space Flight Center two-dimensional (latitude, altitude) time-dependent atmospheric model (NGSFC), is used to study atmospheric chemistry changes. Using CORSIKA, we have created tables that can be used to compute high energy cosmic ray (10 GeV–1 PeV) induced atmospheric ionization and also, with the use of the NGSFC code, can be used to simulate the resulting atmospheric chemistry changes. We discuss the tables, their uses, weaknesses, and strengths.

  15. Energy-Dependent Ionization States of Shock-Accelerated Particles in the Solar Corona

    NASA Technical Reports Server (NTRS)

    Reames, Donald V.; Ng, C. K.; Tylka, A. J.

    2000-01-01

    We examine the range of possible energy dependence of the ionization states of ions that are shock-accelerated from the ambient plasma of the solar corona. If acceleration begins in a region of moderate density, sufficiently low in the corona, ions above about 0.1 MeV/amu approach an equilibrium charge state that depends primarily upon their speed and only weakly on the plasma temperature. We suggest that the large variations of the charge states with energy for ions such as Si and Fe observed in the 1997 November 6 event are consistent with stripping in moderately dense coronal. plasma during shock acceleration. In the large solar-particle events studied previously, acceleration occurs sufficiently high in the corona that even Fe ions up to 600 MeV/amu are not stripped of electrons.

  16. Development of thin gaseous ionization detectors for measurements of high-energy hadron beams

    NASA Astrophysics Data System (ADS)

    Lee, Kyong Sei; Hong, Byungsik; Lee, Kisoo; Park, Sung Keun; Yu, Jaehee; Kim, Sang Yeol

    2014-04-01

    Thin gaseous ionization detectors have been developed based on a current-integration mode for measurements of high-energy hadron beams. In the present detector R&D, two different types of prototype detectors with an active area of 16 × 16 cm2, each equipped with 256-signal processing channels, were manufactured and tested with 43-MeV protons provided by the MC50 proton cyclotron at the Korea Institute of Radiological and Medical Science (KIRAMS). The first one was equipped with a single gas electron multiplier (GEM), and the second one was a thin-plane ionization detector without the GEM foil loaded. The linearities of the detector responses for both detectors were examined for various proton-beam intensities. The quantitative accuracies for the channel-response data and for the total detector responses measured for 43-MeV protons were 0.4% and 0.34%, respectively. We conclude from the beam test that operating both types of detectors in the current-integration mode will allow quality measurements of dynamic-mode hadron beams to be performed with accuracies of better than 1%.

  17. Photoelectron angular distributions of H ionization in low energy regime: Comparison between different potentials

    NASA Astrophysics Data System (ADS)

    Song, Shu-Na; Liang, Hao; Peng, Liang-You; Jiang, Hong-Bing

    2016-09-01

    We theoretically investigate the low energy part of the photoelectron spectra in the tunneling ionization regime by numerically solving the time-dependent Schrdinger equation for different atomic potentials at various wavelengths. We find that the shift of the first above-threshold ionization (ATI) peak is closely related to the interferences between electron wave packets, which are controlled by the laser field and largely independent of the potential. By gradually changing the short-range potential to the long-range Coulomb potential, we show that the long-range potential’s effect is mainly to focus the electrons along the laser’s polarization and to generate the spider structure by enhancing the rescattering process with the parent ion. In addition, we find that the intermediate transitions and the Rydberg states have important influences on the number and the shape of the lobes near the threshold. Project supported by the National Natural Science Foundation of China (Grant Nos. 11322437 and 11574010) and the National Basic Research Program of China (Grant No. 2013CB922402).

  18. Theoretical and experimental investigation of (e,2e) ionization of argon 3p in asymmetric kinematics at intermediate energy

    NASA Astrophysics Data System (ADS)

    Amami, Sadek; Ulu, Melike; Ozer, Zehra Nur; Yavuz, Murat; Kazgoz, Suay; Dogan, Mevlut; Zatsarinny, Oleg; Bartschat, Klaus; Madison, Don

    2014-07-01

    The field of electron-impact ionization of atoms, or (e,2e), has provided significant detailed information about the physics of collisions. For ionization of hydrogen and helium, essentially exact numerical methods have been developed which can correctly predict what will happen. For larger atoms, we do not have theories of comparable accuracy. Considerable attention has been given to ionization of inert gases and, of the inert gases, argon seems to be the most difficult target for theory. There have been several studies comparing experiment and perturbative theoretical approaches over the last few decades, and generally qualitative but not quantitative agreement is found for intermediate energy incident electrons. Recently a nonperturbative method, the B-spline R-matrix (BSR) method, was introduced which appears to be very promising for ionization of heavier atoms. We have recently performed an experimental and theoretical investigation for ionization of argon, and we found that, although the BSR gave reasonably good agreement with experiment, there were also some cases of significant disagreement. The previous study was performed for 200-eV incident electrons and ejected electron energies of 15 and 20 eV. The purpose of the present work is to extend this study to a much larger range of ejected electron energies (15-50 eV) to see if theory gets better with increasing energy as would be expected for a perturbative calculation. The experimental results are compared with both the BSR and two different perturbative calculations.

  19. Comprehensive Wavelengths, Energy Levels, and Hyperfine Structure Parameters of Singly-Ionized Iron-Group Elements

    NASA Astrophysics Data System (ADS)

    Nave, Gillian

    We propose to measure wavelengths, energy levels, and hyperfine structure parameters of Ni II, Mn II, Sc II and other singly-ionized iron-group elements, covering the wavelength range 80 nm to 5500 nm. We shall use archival data from spectrometers at NIST and Kitt Peak National Observatory for spectra above 140 nm. Additional experimental observations will be taken if needed using Fourier transform spectrometers at NIST. Spectra will be taken using our normal incidence grating spectrograph to provide better sensitivity than the FT spectra and to extend the wavelength range down to 80 nm. We aim to produce a comprehensive description of the spectra of all singly-ionized iron- group elements. The wavelength uncertainty of the strong lines will be better than 1 part in 10^7. For most singly-ionized iron-group elements available laboratory data have uncertainties an order of magnitude larger than astronomical observations over wide spectra ranges. Some of these laboratory measurements date back to the 1960's. Since then, Fourier transform spectroscopy has made significant progress in improving the accuracy and quantity of data in the UV-vis-IR region, but high quality Fourier transform spectra are still needed for Mn II, Ni II and Sc II. Fourier transform spectroscopy has low sensitivity in the VUV region and is limited to wavelengths above 140 nm. Spectra measured with high-resolution grating spectrographs are needed in this region in order to obtain laboratory data of comparable quality to the STIS and COS spectrographs on the Hubble Space Telescope. Currently, such data exist only for Fe II and Cr II. Lines of Sc II, V II, and Mn II show hyperfine structure, but hyperfine structure parameters have been measured for relatively few lines of these elements. Significant errors can occur if hyperfine structure is neglected when abundances are determined from stellar spectra. Measurements of hyperfine structure parameters will be made using Fourier transform spectroscopy

  20. Thermometer ions for matrix-enhanced laser desorption/ionization internal energy calibration.

    PubMed

    Greisch, J-F; Gabelica, V; Remacle, F; De Pauw, E

    2003-01-01

    This work describes a method to use relative fragmentation yields to characterize the internal energy distribution of ions produced by matrix-enhanced laser desorption/ionization mass spectrometry (MELDI-MS, see: Wright LG, Cooks RG, Wood KL. Biomed. Mass Spectrom. 1985; 12: 153-162). Assuming that the fragmentation proceeds statistically and that the collisions in the source lead to a Boltzmann-like distribution of the internal energy, a characteristic parameter, the effective temperature, is introduced to describe the internal energy distribution of the ions observed. The hypotheses, advantages and drawbacks of the implementation of the method that uses substituted benzylpyridinium salts as thermometer ions are discussed. Use is made of two matrices that produce no matrix cations in MELDI and are suitable for small cationic salts. The actual value of this effective temperature significantly depends on an accurate determination of the threshold dissociation energies and on the time spent in the source, in addition to the statistical hypothesis itself. The method could be applied to normalize spectra in order to compare results issued from different instruments.

  1. Detection of High Energy Cosmic Rays with Advanced Thin Ionization Calorimeter, ATIC

    NASA Technical Reports Server (NTRS)

    Adams, J. H.; Ahn, E. J.; Ahn, H. S.; Bashindzhagyan, G.; Case, G.; Chang, J.; Christl, M.; Ellison, S.; Fazely, A. R.; Ganel, O.

    2002-01-01

    The author presents preliminary results of the first flight of the Advanced Thin Ionization Calorimeter (ATIC). ATIC is a multiple, long duration balloon flight, investigation for the study of cosmic ray spectra from below 50 GeV to near 100 TeV total energy, using a fully active Bismuth Germanate (BGO) calorimeter. It is equipped with the first large area mosaic of small fully depleted silicon detector pads capable of charge identification of cosmic rays from H to Fe. As a redundancy check for the charge identification and a coarse particle tracking system, three projective layers of x-y scintillator hodoscopes were employed, above, in the center and below a Carbon interaction 'target'.

  2. Dynamics of transfer ionization in p -He collisions at intermediate energies

    NASA Astrophysics Data System (ADS)

    Guo, D. L.; Ma, X.; Zhang, S. F.; Zhu, X. L.; Feng, W. T.; Zhang, R. T.; Gao, Y.; Hai, B.; Zhang, M.; Qian, D. B.; Yan, S.; Zhang, P.

    2017-02-01

    We have performed a kinematically complete experiment for transfer ionization, i.e., the capture of one target electron by the projectile accompanied by the ejection of a second electron, for 50-100 keV p -He collisions by means of a reaction microscope. It was found that the electron momentum distribution projected onto the scattering plane is consistent with the prediction of an independent two-step mechanism involving a binary encounter. The deviation of the electron momentum distribution from the ideal binary ridge is attributed to binding energy effects and the interaction between the electron and the residual recoil ion. The good agreement between our measurements with the dynamic-screening classical trajectory Monte-Carlo calculations strongly suggests that electron-electron correlations play an important role in this two-electron process.

  3. Electron Impact K-shell Ionization Cross Sections at high energies

    NASA Astrophysics Data System (ADS)

    Haque, A. K. F.; Sarker, M. S. I.; Patoary, M. A. R.; Shahjahan, M.; Ismail Hossain, M.; Alfaz Uddin, M.; Basak, A. K.; Saha, Bidhan

    2008-10-01

    A simple modification of the empirical model of Deutsh et. al. [1] by incorporating both the ionic [2] and relativistic corrections [3] is proposed for evaluating the electron impact K -shell ionization cross sections of neutral atomic targets. Present results for 30 atomic targets with atomic number Z=1 -- 92 for incident energies up to E=2 GeV, agree well with available experimental cross sections. Comparisons with other theoretical findings will also be presented at the conference. [1] H. Deutsh, K. Becker, T. D. Mark, Int. J. Mass Spect. 177, 47 (1998). [2] M. A. Uddin, A. K. F. Haque, M. M. Billah, A. K. Basak, K. R. Karim, B. C. Saha, Phys. Rev. A 71, 032715 (2005).; Phys. Rev. A 73, 012708 (2006). [3] M. Gryzinski, Phys. Rev 138, 336 (1965).

  4. Energy levels of neutral and singly ionized berkelium, /sup 249/Bk I and II

    SciTech Connect

    Worden, E.F.; Conway, J.G.; Blaise, J.

    1987-09-01

    Energy-level analyses of the observed emission spectrum of berkelium have yielded 179 odd and 186 even levels of neutral berkelium Bk I, and 42 odd and 117 even levels of singly ionized berkelium Bk II. The levels are tabulated with the J value, the g value, the configuration and hyperfine constants A and B, and the width given for many of the levels. The ground states of Bk I and Bk II are (Rn)5f/sup 9/7s/sup 2/ /sup 6/H/sup 0//sub 15/2/ and (Rn)5f/sup 9/7s /sup 7/H/sup 0//sub 8/, respectively. A table lists the lowest level of each identified electronic configuration of Bk I and Bk II.

  5. Complete description of ionization energy and electron affinity in organic solids: Determining contributions from electronic polarization, energy band dispersion, and molecular orientation

    NASA Astrophysics Data System (ADS)

    Yoshida, Hiroyuki; Yamada, Kazuto; Tsutsumi, Jun'ya; Sato, Naoki

    2015-08-01

    Ionization energy and electron affinity in organic solids are understood in terms of a single molecule perturbed by solid-state effects such as polarization energy, band dispersion, and molecular orientation as primary factors. However, no work has been done to determine the individual contributions experimentally. In this work, the electron affinities of thin films of pentacene and perfluoropentacene with different molecular orientations are determined to a precision of 0.1 eV using low-energy inverse photoemission spectroscopy. Based on the precisely determined electron affinities in the solid state together with the corresponding data of the ionization energies and other energy parameters, we quantitatively evaluate the contribution of these effects. It turns out that the bandwidth as well as the polarization energy contributes to the ionization energy and electron affinity in the solid state while the effect of the surface dipole is at most a few eV and does not vary with the molecular orientation. As a result, we conclude that the molecular orientation dependence of the ionization energy and electron affinity of organic solids originates from the orientation-dependent polarization energy in the film.

  6. Towards More Accurate Measurements of the Ionization Energy of Molecular Hydrogen

    NASA Astrophysics Data System (ADS)

    Sprecher, D.; Beyer, M.; Liu, J.; Merkt, F.; Salumbides, E.; Eikema, K. S. E.; Ubachs, W.; Jungen, Ch.

    2013-06-01

    With two electrons and two protons, molecular hydrogen is the simplest molecule displaying all features of a chemical bond. H_2 is therefore a fundamental system for testing molecular quantum mechanics and quantum electrodynamics in molecules. The test can be performed by comparing measured and calculated intervals between different rovibronic states of H_2. Two further quantities that can be used for this test are the dissociation and ionization energies of H_2, and considerable efforts have been invested over more than 80 years to improve the precision and accuracy of experimental and theoretical determination of these two quantities. The current status of the comparison is that the theoretical and experimental values of the ionization and dissociation energies of H_2 agree within the combined uncertainty of 30 MHz (see also). The factors currently limiting the precision of the experimental determination will be discussed and the strategies that are being implemented towards overcoming these limitations will be presented. A long-term goal is to achieve a precision of better than 15 kHz, which is the ultimate limit imposed on the accuracy of the theoretical determination by the current uncertainty of the proton-to-electron mass ratio. E. J. Salumbides, G. D. Dickenson, T. I. Ivanov and W. Ubachs, {Phys. Rev. Lett.} 107 (4), 043005 (2011). K. Piszczatowski, G. Lach, M. Przybytek, J. Komasa, K. Pachuckiand and B. Jeziorski, {J. Chem. Theory Comput.} 5 (11), 3039 (2009). J. Liu, E. J. Salumbides, U. Hollenstein, J. C. J. Koelemeij, K. S. E. Eikema, W. Ubachs and F. Merkt, {J. Chem. Phys.} 130 (17), 174306 (2009). D. Sprecher, Ch. Jungen, W. Ubachs and F. Merkt, {Faraday Discuss.} 150, 51 (2011).

  7. Electron ionization cross-section calculations for liquid water at high impact energies

    NASA Astrophysics Data System (ADS)

    Bousis, C.; Emfietzoglou, D.; Hadjidoukas, P.; Nikjoo, H.; Pathak, A.

    2008-04-01

    Cross-sections for the ionization of liquid water is perhaps the most essential set of data needed for modeling electron transport in biological matter. The complexity of ab initio calculations for any multi-electron target has led to largely heuristic semi-empirical models which take advantage elements of the Bethe, dielectric and binary collision theories. In this work we present various theoretical models for calculating total ionization cross-sections (TICSs) for liquid water over the 10 keV-1 MeV electron energy range. In particular, we extend our recent dielectric model calculations for liquid water to relativistic energies using both the appropriate kinematic corrections and the transverse part. Comparisons are made with widely used atomic and molecular TICS models such as those of Khare and co-workers, Kim-Rudd, Deutsch-Märk, Vriens and Gryzinski. The required dipole oscillator strength was provided by our recent optical-data model which is based on the latest experimental data for liquid water. The TICSs computed by the above models differ by up to 40% from the dielectric results. The best agreement (to within ∼10%) was obtained by Khare's original model and an approximate form of Gryzinski's model. In contrast, the binary-encounter-dipole (BED) models of both Kim-Rudd and Khare and co-workers resulted in ∼10-20% higher TICS values, while discrepancies increased to ∼30-40% when their simpler binary-encounter-Bethe (BEB) versions were used. Finally, we discuss to what extent the accuracy of the TICS is indicative of the reliability of the underlying differential cross-sections.

  8. Ionization probabilities of Ne, Ar, Kr, and Xe by proton impact for different initial states and impact energies

    NASA Astrophysics Data System (ADS)

    Montanari, C. C.; Miraglia, J. E.

    2017-09-01

    In this contribution we present ab initio results for ionization total cross sections, probabilities at zero impact parameter, and impact parameter moments of order +1 and -1 of Ne, Ar, Kr, and Xe by proton impact in an extended energy range from 100 keV up to 10 MeV. The calculations were performed by using the continuum distorted wave eikonal initial state approximation (CDW-EIS) for energies up to 1 MeV, and using the first Born approximation for larger energies. The convergence of the CDW-EIS to the first Born above 1 MeV is clear in the present results. Our inner-shell ionization cross sections are compared with the available experimental data and with the ECPSSR results. We also include in this contribution the values of the ionization probabilities at the origin, and the impact parameter dependence. These values have been employed in multiple ionization calculations showing very good description of the experimental data. Tables of the ionization probabilities are presented, disaggregated for the different initial bound states, considering all the shells for Ne and Ar, the M-N shells of Kr and the N-O shells of Xe.

  9. Uncovering the Spectral Energy Distribution in Active Galaxies Using High Ionization Mid-Infrared Emission Lines

    NASA Technical Reports Server (NTRS)

    Melendez, M.; Kraemer, S. B.; Weaver, K. A.; Mushotzky, R. F.

    2011-01-01

    The shape of the spectral energy distribution of active galaxies in the EUV soft X-ray band (13.6 eV to 1 keV) is uncertain because obscuration by dust and gas can hamper our view of the continuum. To investigate the shape of the spectral energy distribution in this energy band, we have generated a set of photoionization models which reproduce the small dispersion found in correlations between high-ionization mid-infrared emission lines in a sample of hard X-ray selected AGN. Our calculations show that a broken power-law continuum model is sufficient to reproduce the [Ne V]14.32 microns/[Ne III], [Ne V]24.32 microns/[O IV]25.89 micron and [O IV] 25.89 microns/[Ne III] ratios, and does not require the addition of a "big bump" EUV model component. We constrain the EUV-soft X-ray slope, alpha(sub i), to be between 1.5 - 2.0 and derive a best fit of alpha(sub i) approx. 1.9 for Seyfert 1 galaxies, consistent with previous studies of intermediate redshift quasars. If we assume a blue bump model, most sources in our sample have derived temperatures between T(sub BB) = 10(exp 5.18) K to 10(exp 5.7) K, suggesting that the peak of this component spans a large range of energies extending from approx. (Lambda)600 A to > (Lambda)1900 A. In this case, the best fitting peak energy that matches the mid-infrared line ratios of Seyfert 1 galaxies occurs between approx. (Lambda)700-(Lambda)1000 A. Despite the fact that our results do not rule out the presence of an EUV bump, we conclude that our power-law model produces enough photons with energies > 4 Ry to generate the observed amount of mid-infrared emission in our sample of BAT AGN.

  10. Indirect dark matter signatures in the cosmic dark ages. II. Ionization, heating, and photon production from arbitrary energy injections

    NASA Astrophysics Data System (ADS)

    Slatyer, Tracy R.

    2016-01-01

    Any injection of electromagnetically interacting particles during the cosmic dark ages will lead to increased ionization, heating, production of Lyman-α photons and distortions to the energy spectrum of the cosmic microwave background, with potentially observable consequences. In this paper we describe numerical results for the low-energy electrons and photons produced by the cooling of particles injected at energies from keV to multi-TeV scales, at arbitrary injection redshifts (but focusing on the post-recombination epoch). We use these data, combined with existing calculations modeling the cooling of these low-energy particles, to estimate the resulting contributions to ionization, excitation and heating of the gas, and production of low-energy photons below the threshold for excitation and ionization. We compute corrected deposition-efficiency curves for annihilating dark matter, and demonstrate how to compute equivalent curves for arbitrary energy-injection histories. These calculations provide the necessary inputs for the limits on dark matter annihilation presented in the accompanying paper I, but also have potential applications in the context of dark matter decay or deexcitation, decay of other metastable species, or similar energy injections from new physics. We make our full results publicly available at http://nebel.rc.fas.harvard.edu/epsilon, to facilitate further independent studies. In particular, we provide the full low-energy electron and photon spectra, to allow matching onto more detailed codes that describe the cooling of such particles at low energies.

  11. Satellite structure in the Argon 1s photoelectron spectrum

    SciTech Connect

    Azuma, Y.; LeBrun, T.; MacDonald, M.; Southworth, S.H.

    1995-08-01

    Atomic inner-shell photoelectron spectra typically display several relatively weak {open_quotes}satellite peaks{close_quotes} at higher ionization energy than the primary peak. Such satellite peaks are associated with final-state configurations corresponding to ionization of an inner-shell electron and excitation or ionization of one or more valence electrons. The observation of satellite peaks demonstrates that the independent-electron picture is inadequate to describe atomic structure and the photoionization process. The measured energies and intensities of photoelectron satellites provide sensitive tests of many-electron theoretical models. We recorded the Ar 1s photoelectron spectrum on beam line X-24A at an X-ray energy of 3628 eV. The primary peak at 3206 eV ionization energy was recorded at an observed resolution of 1.8 eV (FWHM). The satellite structure shows remarkable similarity to that recorded in the suprathreshold region of the Ar K photoabsorption cross section, demonstrating the manner in which these techniques complement each other. Surprisingly, while the region just above the K threshold in Ar was the subject of several theoretical studies using multi-configuration calculations, we find good agreement between our results and those of Dyall and collaborators using a shake model.

  12. Quantum mechanics/molecular mechanics modeling of photoelectron spectra: the carbon 1s core-electron binding energies of ethanol-water solutions.

    PubMed

    Löytynoja, T; Niskanen, J; Jänkälä, K; Vahtras, O; Rinkevicius, Z; Ågren, H

    2014-11-20

    Using ethanol-water solutions as illustration, we demonstrate the capability of the hybrid quantum mechanics/molecular mechanics (QM/MM) paradigm to simulate core photoelectron spectroscopy: the binding energies and the chemical shifts. An integrated approach with QM/MM binding energy calculations coupled to preceding molecular dynamics sampling is adopted to generate binding energies averaged over the solute-solvent configurations available at a particular temperature and pressure and thus allowing for a statistical assessment with confidence levels for the final binding energies. The results are analyzed in terms of the contributions in the molecular mechanics model-electrostatic, polarization, and van der Waals-with atom or bond granulation of the corresponding MM charge and polarizability force-fields. The role of extramolecular charge transfer screening of the core-hole and explicit hydrogen bonding is studied by extending the QM core to cover the first solvation shell. The results are compared to those obtained from pure electrostatic and polarizable continuum models. Particularly, the dependence of the carbon 1s binding energies with respect to the ethanol concentration is studied. Our results indicate that QM/MM can be used as an all-encompassing model to study photoelectron binding energies and chemical shifts in solvent environments.

  13. Energy-sharing (e ,2 e ) collisions: Ionization of the inert gases in the perpendicular plane

    NASA Astrophysics Data System (ADS)

    Miller, F. K.; Walters, H. R. J.; Whelan, Colm T.

    2015-01-01

    The triple differential cross section for ionization of the inert gases He, Ne, Ar, Kr, and Xe in energy-sharing perpendicular plane geometry is investigated. Encouraging agreement with recent experiments is found using the distorted-wave Born approximation (DWBA). Mechanisms are discussed which explain the He and Ne data but which seem to be masked by the greater distortion effects in the heavier targets. The inclusion of postcollisional interaction is explored using Gamow, Ne e, and Ward-Macek, Me e, factors. While both help to improve the shape of the cross section for He and Ne at the lower energies, they are not successful for the other targets, and both factors prove to be too strong for all the inert gases with increasing impact energy. It is well known that Ne e destroys normalization. Comparing DWBA +Me e results with some absolute experimental points at 1 and 2 eV indicates that it is also not to be trusted on normalization. An interesting situation with Ar is highlighted near 25 eV, where the cross section may be tending towards a strong interference minimum or zero.

  14. Three-dimensional Čerenkov tomography of energy deposition from ionizing radiation beams.

    PubMed

    Glaser, Adam K; Voigt, William H A; Davis, Scott C; Zhang, Rongxiao; Gladstone, David J; Pogue, Brian W

    2013-03-01

    Since its discovery during the 1930s the Čerenkov effect (light emission from charged particles traveling faster than the local speed of light in a dielectric medium) has been paramount in the development of high-energy physics research. The ability of the emitted light to describe a charged particle's trajectory, energy, velocity, and mass has allowed scientists to study subatomic particles, detect neutrinos, and explore the properties of interstellar matter. However, to our knowledge, all applications of the process to date have focused on the identification of particles themselves, rather than their effect upon the surroundings through which they travel. Here we explore a novel application of the Čerenkov effect for the recovery of the spatial distribution of ionizing radiation energy deposition in a medium and apply it to the issue of dose determination in medical physics. By capturing multiple projection images of the Čerenkov light induced by a medical linear accelerator x-ray photon beam, we demonstrate the successful three-dimensional tomographic reconstruction of the imparted dose distribution.

  15. Determination of ionization energies of small silicon clusters with vacuum?ultraviolet (VUV) radiation

    SciTech Connect

    Kostko, Oleg; Leone, Stephen R.; Duncan, Michael A.; Ahmed, Musahid

    2009-09-23

    In this work we report on single photon vacuum ultraviolet photoionization of small silicon clusters (n=1-7) produced via laser ablation of Si. The adiabatic ionization energies (AIE) are extracted from experimental photoionization efficiency (PIE) curves with the help of Frank?Condon simulations, used to interpret the shape and onset of the PIE curves. The obtained AIEs are (all energies are in eV): Si (8.13+-0.05), Si2 (7.92+-0.05), Si3 (8.12+-0.05), Si4 (8.2+-0.1), Si5 (7.96+-0.07), Si6 (7.8+-0.1), and Si7 (7.8+-0.1). Most of the experimental AIE values are in good agreement with ab initio electronic structure calculations. To explain observed deviations between the experimental and theoretical AIEs for Si4 and Si6, a theoretical search of different isomers of these species is performed. Electronic structure calculations aid in the interpretation of the a2PIu state of Si2+ dimer in the PIE spectrum. Time dependent density functional theory (TD-DFT) calculations are performed to reveal the energies of electronically excited states in the cations for a number of Si clusters.

  16. Three-dimensional Čerenkov tomography of energy deposition from ionizing radiation beams

    PubMed Central

    Glaser, Adam K.; Voigt, William H.A.; Davis, Scott C.; Zhang, Rongxiao; Gladstone, David J.; Pogue, Brian W.

    2013-01-01

    Since its discovery during the 1930’s, the Čerenkov effect (light emission from charged particles traveling faster than the local speed of light in a dielectric medium) has been paramount in the development of high-energy physics research. The ability of the emitted light to describe a charged particle’s trajectory, energy, velocity, and mass has allowed scientists to study subatomic particles, detect neutrinos, and explore the properties of interstellar matter. However, all applications of the process to date have focused on identification of particle’s themselves, rather than their effect upon the surroundings through which they travel. Here, we explore a novel application of the Čerenkov effect for the recovery of the spatial distribution of ionizing radiation energy deposition in a medium, and apply it to the issue of dose determination in medical physics. By capturing multiple projection images of the Čerenkov light induced by a medical linear accelerator (LINAC) x-ray photon beam, we demonstrate the successful three-dimensional (3D) tomographic reconstruction of the imparted dose distribution for the first time. PMID:23455248

  17. Radiation and ionization energy loss simulation for the GDH sum rule experiment in Hall-A at Jefferson Lab

    NASA Astrophysics Data System (ADS)

    Yan, Xin-Hu; Ye, Yun-Xiu; Chen, Jian-Ping; Lu, Hai-Jiang; Zhu, Peng-Jia; Jiang, Feng-Jian

    2015-07-01

    The radiation and ionization energy loss are presented for single arm Monte Carlo simulation for the GDH sum rule experiment in Hall-A at the Jefferson Lab. Radiation and ionization energy loss are discussed for 12C elastic scattering simulation. The relative momentum ratio \\frac{{Δ p}}{p} and 12C elastic cross section are compared without and with radiative energy loss and a reasonable shape is obtained by the simulation. The total energy loss distribution is obtained, showing a Landau shape for 12C elastic scattering. This simulation work will give good support for radiation correction analysis of the GDH sum rule experiment. Supported by National Natural Science Foundation of China (11135002, 11275083), US Department of Energy contract DE-AC05-84ER-40150 under which Jefferson Science Associates operates the Thomas Jefferson National Accelerator Facility and Natural Science Foundation of An'hui Educational Committee (KJ2012B179)

  18. Deregulated G1-S control and energy stress contribute to the synthetic-lethal interactions between inactivation of RB and TSC1 or TSC2.

    PubMed

    Gordon, Gabriel M; Zhang, Tianyi; Zhao, Jiong; Du, Wei

    2013-05-01

    Synthetic lethality is a potential strategy for cancer treatment by specifically promoting the death of cancer cells with particular defects such as the loss of the RB (RB1) tumor suppressor. We previously showed that inactivation of both RB and TSC2 induces synergistic apoptosis during the development of Drosophila melanogaster and in cancer cells. However, the in vivo mechanism of this synthetic-lethal interaction is not clear. Here, we show that synergistic cell death in tissues that have lost the RB and TSC orthologs rbf and dtsc1/gig, respectively, or overexpress Rheb and dE2F1, are correlated with synergistic defects in G1-S control, which causes cells to accumulate DNA damage. Coexpression of the G1-S inhibitor Dap, but not the G2-M inhibitor dWee1, decreases DNA damage and reduces cell death. In addition, we show that rbf and dtsc1 mutant cells are under energy stress, are sensitive to decreased energy levels and depend on the cellular energy stress-response pathway for survival. Decreasing mitochondrial ATP synthesis by inactivating cova or abrogating the energy-stress response by removing the metabolic regulator LKB1 both enhance the elimination of cells lacking either rbf or dtsc1. These observations, in conjunction with the finding that deregulation of TORC1 induces activation of JNK, indicate that multiple cellular stresses are induced and contribute to the synthetic-lethal interactions between RB and TSC1/TSC2 inactivation. The insights gained from this study suggest new approaches for targeting RB-deficient cancers.

  19. The kinetic energy spectrum of protons produced by the dissociative ionization of H2 by electron impact

    NASA Technical Reports Server (NTRS)

    Khakoo, M. A.; Srivastava, S. K.

    1985-01-01

    The kinetic energy spectra of protons resulting from the dissociative ionization of H2 by electron impact have been measured for electron impact energies from threshold (approximately 17 eV) to 160 eV at 90 deg and 30 deg detection angles, using a crossed-beam experimental arrangement. To check reliability, two separate proton energy analysis methods have been employed, i.e., a time-of-flight proton energy analysis and an electrostatic hemispherical energy analyzer. The present results are compared with previous measurements.

  20. The kinetic energy spectrum of protons produced by the dissociative ionization of H2 by electron impact

    NASA Technical Reports Server (NTRS)

    Khakoo, M. A.; Srivastava, S. K.

    1985-01-01

    The kinetic energy spectra of protons resulting from the dissociative ionization of H2 by electron impact have been measured for electron impact energies from threshold (approximately 17 eV) to 160 eV at 90 deg and 30 deg detection angles, using a crossed-beam experimental arrangement. To check reliability, two separate proton energy analysis methods have been employed, i.e., a time-of-flight proton energy analysis and an electrostatic hemispherical energy analyzer. The present results are compared with previous measurements.

  1. Double L{sub 3}M ionization of Pd induced by impact with medium-energy electrons

    SciTech Connect

    Cao, W.; Dousse, J.-Cl.; Hoszowska, J.; Kayser, Y.; Schenker, J.-L.; Kavcic, M.; Zitnik, M.

    2011-02-15

    The electron-induced L{sub 3}M two-step double ionization cross sections of metallic Pd were determined experimentally for incident electron beam energies ranging from the double ionization threshold up to 18 keV. The double L{sub 3}M ionization cross sections were derived from the intensity ratios (I{sub L{alpha}M}:I{sub L{alpha}}) of the resolved M satellites to the parent diagram lines. The sample was bombarded with monoenergetic electrons from an energy-tunable 20-kV electron gun. The diagram and M-satellite x-ray lines were measured by means of high-resolution x-ray spectroscopy, using a reflection-type von Hamos bent crystal spectrometer. The two-step partial cross sections were determined by subtracting from the measured total double ionization cross sections the contributions due to the shake process and L{sub 1}-L{sub 3}M{sub 4,5} Coster-Kronig transitions. Despite the thick target employed in the present study, the dependence of the two-step cross sections on the incoming electron energy could be derived using a target slice decomposition method. It is shown that the obtained energy dependence can be well reproduced by the semiempirical parametrization model of Pattard and Rost.

  2. Quantitatively identical orientation-dependent ionization energy and electron affinity of diindenoperylene

    SciTech Connect

    Han, W. N.; Yonezawa, K.; Makino, R.; Kato, K.; Hinderhofer, A.; Ueno, N.; Kera, S.; Murdey, R.; Shiraishi, R.; Yoshida, H.; Sato, N.

    2013-12-16

    Molecular orientation dependences of the ionization energy (IE) and the electron affinity (EA) of diindenoperylene (DIP) films were studied by using ultraviolet photoemission spectroscopy and inverse photoemission spectroscopy. The molecular orientation was controlled by preparing the DIP films on graphite and SiO{sub 2} substrates. The threshold IE and EA of DIP thin films were determined to be 5.81 and 3.53 eV for the film of flat-lying DIP orientation, respectively, and 5.38 and 3.13 eV for the film of standing DIP orientation, respectively. The result indicates that the IE and EA for the flat-lying film are larger by 0.4 eV and the frontier orbital states shift away from the vacuum level compared to the standing film. This rigid energy shift is ascribed to a surface-electrostatic potential produced by the intramolecular polar bond (>C{sup −}-H{sup +}) for standing orientation and π-electron tailing to vacuum for flat-lying orientation.

  3. Relation between molecule ionization energy, film thickness and morphology of two indandione derivatives thin films

    NASA Astrophysics Data System (ADS)

    Grzibovskis, Raitis; Vembris, Aivars; Pudzs, Kaspars

    2016-08-01

    Nowadays most organic devices consist of thin (below 100 nm) layers. Information about the morphology and energy levels of thin films at such thickness is essential for the high efficiency devices. In this work we have investigated thin films of 2-(4-[N,N-dimethylamino]-benzylidene)-indene-1,3-dione (DMABI) and 2-(4-(bis(2-(trityloxy)ethyl)amino)benzylidene)-2H-indene-1,3-dione (DMABI-6Ph). DMABI-6Ph is the same DMABI molecule with attached bulky groups which assist formation of amorphous films from solutions. Polycrystalline structure was obtained for the DMABI thin films prepared by thermal evaporation in vacuum and amorphous structure for the DMABI-6Ph films prepared by spin-coating method. Images taken by SEM showed separate crystals or islands at the thickness of the samples below 100 nm. The ionization energy of the studied compounds was determined using photoemission yield spectroscopy. A vacuum level shift of 0.40 eV was observed when ITO electrode was covered with the thin film of the organic compound. Despite of the same active part of the investigated molecules the ITO/DMABI interface is blocking electrons while ITO/DMABI-6Ph interface is blocking holes.

  4. Numerical studies of the behavior of ionized residual gas in an energy recovering linac

    NASA Astrophysics Data System (ADS)

    Pöplau, Gisela; van Rienen, Ursula; Meseck, Atoosa

    2015-04-01

    Next generation light sources such as energy recovering linacs (ERLs) are highly sensitive to instabilities due to ionized residual gas, which must be mitigated for successful operation. Vacuum pumps are insufficient for removal of the ions, as the ions are trapped by the beam's electrical potential. Two effective measures are (i) introducing clearing gaps in the bunch train, and (ii) installing clearing electrodes which pull out the trapped ions from the electrical potential of the beam. In this paper, we present numerical studies on the behavior of ion clouds that interact with bunch trains in an ERL taking into account the effects of the clearing gaps and clearing electrodes. We present simulations with different compositions of the residual gas. Simulations are done using the MOEVE PIC Tracking software package developed at Rostock University, which has been upgraded to include the behavior of ion clouds in the environment of additional electromagnetic fields, such as generated by clearing electrodes. The simulations use the parameters of the Berlin Energy Recovery Linac Project (bERLinPro) to allow for the deduction of appropriate measures for bERLinPro 's design and operation.

  5. Experimental evidence of resonant energy collisional transfers between argon 1s and 2p states and ground state H atoms by laser collisional induced fluorescence

    NASA Astrophysics Data System (ADS)

    Carbone, Emile; van Dijk, Jan; Kroesen, Gerrit

    2015-04-01

    In this paper, laser collisional induced fluorescence (LCIF) is used to probe resonant excitation transfers in an argon/hydrogen plasma resulting from heavy particle collisions. Different radiative transitions between the 1s and 2p states (in Paschen's notation) of argon are optically pumped by a nanosecond laser pulse. The spontaneous fluorescence and collisional responses of the argon and hydrogen systems are monitored by optical emission spectroscopy. A surfatron plasma source is used to generate an argon plasma with a few per cent hydrogen addition at pressures between 0.65 and 20 mbar. The electron density is measured independently by means of Thomson scattering. The overall response of the plasma due to optical pumping of argon is briefly discussed and an overview of the known heteronuclear excitation transfers in an argon/hydrogen plasma is given. The propagation of the shortcut in the Ar(1s) to H(n = 2) excitation transfer due to the optical pumping of the Ar(1s) states is seen in the atomic hydrogen LCIF responses. For the first time, we give direct experimental evidence of the existence of an efficient excitation transfer: Additionally, measurements are performed in order to estimate the resonant energy transfer between the resonant argon 1s states and hydrogen atoms: for which no previously measured cross sections could be found in the literature. These are extra quenching channels of argon 1s and 2p states that should be included in collisional-radiative modeling of argon-hydrogen discharges. The high repetition rate of the dye laser allows us to obtain a high sensitivity in the measurements. LCIF is shown to be a powerful tool for unraveling electron and also heavy particle excitation channels in situ in the plasma phase. The technique was previously developed for measuring electron or species densities locally in the plasma, but we show that it can be advantageously used to probe collisional transfers between very short-lived species which exist

  6. K-italic-shell ionization cross sections for Al, Ti, V, Cr, Fe, Ni, Cu, and Ag by protons and oxygen ions in the energy range 0. 3--6. 4 MeV

    SciTech Connect

    Geretschlaeger, M.; Benka, O.

    1986-08-01

    Absolute K-italic-shell ionization cross sections have been measured for thin targets of Al, Ti, and Cu for protons in the energy range 0.3--2.0 MeV and for thin targets of Ti, V, Cr, Fe, Ni, Cu, and Ag for oxygen ions in the energy range 1.36--6.4 Mev. The experimental results are compared to the perturbed-stationary-state (PSS) approximation with energy-loss (E), Coulomb (C), and relativistic (R) corrections, i.e., the ECPSSR approximation (Brandt and Lapicki), to the semiclassical approximation (Laegsgaard, Andersen, and Lund), and to a theory for direct Coulomb ionization of the 1s-italicsigma molecular orbital (Montenegro and Sigaud (MS)). The proton results agree within 3% with empirical reference cross sections. Also, the ECPSSR provides best overall agreement for protons. For oxygen ions, ECPSSR and MS predict experimental results satisfactorily for scaled velocities xi> or =0.4. For lower scaled velocities, the experimental cross sections become considerably higher than theoretical predictions for Coulomb ionization. This deviation increases with increasing Z-italic/sub 1//Z/sub 2/; it cannot be explained by electron transfer to the projectile or by ionization due to target recoil atoms.

  7. Dissociative Ionization Mechanism and Appearance Energies in Adipic Acid Revealed by Imaging Photoelectron Photoion Coincidence, Selective Deuteration, and Calculations.

    PubMed

    Heringa, Maarten F; Slowik, Jay G; Prévôt, André S H; Baltensperger, Urs; Hemberger, Patrick; Bodi, Andras

    2016-05-26

    Adipic acid, a model compound for oxygenated organic aerosol, has been studied at the VUV beamline of the Swiss Light Source. Internal energy selected cations were prepared by threshold photoionization using vacuum ultraviolet synchrotron radiation and imaging photoelectron photoion coincidence spectroscopy (iPEPICO). The threshold photoelectron spectrum yields a vertical ionization energy (IE) of 10.5 eV, significantly above the calculated adiabatic IE of 8.6 eV. The cationic minimum is accessible after vertical ionization by H-transfer from one of the γ-carbons to a carbonyl oxygen and is sufficiently energetic to decay by water loss at the ionization onset. The slope of the breakdown curves, quantum chemical calculations, and selective deuteration of the carboxylic hydrogens establish the dissociative photoionization mechanism. After ionization, one γ-methylene hydrogen and the two carboxylic hydrogens are randomized prior to H2O loss. On the basis of the deuteration degree in the H2O + CO-loss product at higher energies, a direct water-loss channel without complete randomization also exists. The breakdown diagram and center of gravity of the H2O + CO-loss peak were modeled to obtain 0 K appearance energies of 10.77, 10.32, and 11.53 eV for H2O + CO loss, CH2COOH loss, and H2O + CH2COOH loss from adipic acid. These agree well with the CBS-QB3 calculated values of 10.68, 10.45, and 11.57 eV, respectively, which shows that threshold photoionization can yield energetics data as long as the dissociation is statistical, even when the parent ion cannot be observed. The results can be used as a starting point for a deeper understanding of the ionization and low-energy fragmentation of organic aerosol components.

  8. Valence ionized states of iron pentacarbonyl and eta5-cyclopentadienyl cobalt dicarbonyl studied by symmetry-adapted cluster-configuration interaction calculation and collision-energy resolved Penning ionization electron spectroscopy.

    PubMed

    Fukuda, Ryoichi; Ehara, Masahiro; Nakatsuji, Hiroshi; Kishimoto, Naoki; Ohno, Koichi

    2010-02-28

    Valence ionized states of iron pentacarbonyl Fe(CO)(5) and eta(5)-cyclopentadienyl cobalt dicarbonyl Co(eta(5)-C(5)H(5))(CO)(2) have been studied by ultraviolet photoelectron spectroscopy, two-dimensional Penning ionization electron spectroscopy (2D-PIES), and symmetry-adapted cluster-configuration interaction calculations. Theory provided reliable assignments for the complex ionization spectra of these molecules, which have metal-carbonyl bonds. Theoretical ionization energies agreed well with experimental observations and the calculated wave functions could explain the relative intensities of PIES spectra. The collision-energy dependence of partial ionization cross sections (CEDPICS) was obtained by 2D-PIES. To interpret these CEDPICS, the interaction potentials between the molecules and a Li atom were examined in several coordinates by calculations. The relation between the slope of the CEDPICS and the electronic structure of the ionized states, such as molecular symmetry and the spatial distribution of ionizing orbitals, was analyzed. In Fe(CO)(5), an attractive interaction was obtained for the equatorial CO, while the interaction for the axial CO direction was repulsive. For Co(eta(5)-C(5)H(5))(CO)(2), the interaction potential in the direction of both Co-C-O and Co-Cp ring was attractive. These anisotropic interactions and ionizing orbital distributions consistently explain the relative slopes of the CEDPICS.

  9. Coupled-Sturmian and perturbative treatments of electron transfer and ionization in high-energy p -He sup + collisions

    SciTech Connect

    Winter, T.G. Department of Physics, Rice University, Houston, Texas 77251 ); Alston, S.G. )

    1992-02-01

    Cross sections have been determined for electron transfer and ionization in collisions between protons and He{sup +} ions at proton energies from several hundred kilo-electron-volts to 2 MeV. A coupled-Sturmian approach is taken, extending the work of Winter (Phys. Rev. A 35, 3799 (1987)) and Stodden {ital et} {ital al}. (Phys. Rev. A 41, 1281 (1990)) to high energies where perturbative approaches are expected to be valid. An explicit connection is made with the first-order Born approximation for ionization and the impulse version of the distorted, strong-potential Born approximation for electron transfer. The capture cross section is shown to be affected by the presence of target basis functions of positive energy near {ital v}{sup 2}/2, corresponding to the Thomas mechanism.

  10. Structure of the Thermosphere during Energy Input through the Magnetospheric cusp: Measurements from the RENU2 Ionization Gauge

    NASA Astrophysics Data System (ADS)

    Clemmons, J. H.; Hecht, J. H.; Brinkman, D. G.; Lessard, M.; Hysell, D. L.; Lynch, K. A.; Harrington, M. I.; Oksavik, K.; Moen, J. I.; Sigernes, F.; Yeoman, T. K.; Fritz, B.

    2016-12-01

    Measurements returned by the ionization gauge on the Rocket Experiment for Neutral Upwelling 2 (RENU2) are presented and discussed. The RENU2 mission was launched from the rocket range at the Andøya Space Center on 13 December 2015 into the ionosphere-thermosphere beneath the magnetospheric cusp. Significant structured energy input from high altitudes was observed during the launch. The ionization gauge, which is a sensitive gas sensor, also measured significant horizontal and vertical structure. This presentation reports on the measurements, the data treatment, and the resulting inferred thermospheric structure. The structure is interpreted in the context of the structured energy input and is taken to be a response to that energy input.

  11. Ionization processes in small quasimolecules: He{sub 2}{sup 2+} (He{sup 2+}+ He)

    SciTech Connect

    Ogurtsov, G. N.; Mikoushkin, V. M.; Ovchinnikov, S. Yu.; Macek, J. H.

    2011-09-15

    The energy spectra of electrons ejected in He{sup 2+}-He collisions were measured in the ion energy range 6-30 keV. Theoretical analysis of the ionization mechanisms has been performed on the basis of the advanced adiabatic approximation for one-electron processes and perturbation theory for two-electron processes. The ionization channel 2p{sigma}{sup 2}{yields} 1s{sigma}nd{sigma}{yields} 1s{sigma}{epsilon}d{sigma} has been revealed, which makes a considerable contribution to the ionization cross section in the keV ion energy range.

  12. Electron-impact excitation and ionization of atomic boron at low and intermediate energies

    NASA Astrophysics Data System (ADS)

    Wang, Kedong; Zatsarinny, Oleg; Bartschat, Klaus

    2016-05-01

    We present a comprehensive study of electron collisions with neutral boron atoms. The calculations were performed with the B-Spline R-matrix (close-coupling) method, by employing a parallelized version of the associated computer code. Elastic, excitation, and ionization cross sections were obtained for all transitions involving the lowest 11 states of boron, for incident electron energies ranging from threshold to 100 eV. A multiconfiguration Hartree-Fock method with nonorthogonal term-dependent orbitals was used to generate accurate wave functions for the target states. Close-coupling expansions including 13, 51, and 999 physical and pseudo states were set up to check the sensitivity of the predictions to variations in the theoretical model. The cross-section dataset generated in this work is expected to be the most accurate one available today and should be sufficiently comprehensive for most modeling applications involving neutral boron. Work supported by the China Scholarship Council and the United States National Science Foundation under Grants PHY-1403245 and PHY-1520970, and by the XSEDE allocation PHY-090031.

  13. Near-coincident K-line and K-edge energies as ionization diagnostics for some high atomic number plasmas

    SciTech Connect

    Pereira, N. R.; Weber, B. V.; Phipps, D. G.; Schumer, J. W.; Seely, J. F.; Carroll, J. J.; Vanhoy, J. R.; Slabkowska, K.; Polasik, M.

    2012-10-15

    For some high atomic number atoms, the energy of the K-edge is tens of eVs higher than the K-line energy of another atom, so that a few eV increase in the line's energy results in a decreasing transmission of the x-ray through a filter of the matching material. The transmission of cold iridium's Asymptotically-Equal-To 63.287 keV K{alpha}{sub 2} line through a lutetium filter is 7% lower when emitted by ionized iridium, consistent with an energy increase of {Delta}{epsilon} Asymptotically-Equal-To 10{+-}1 eV associated with the ionization. Likewise, the transmission of the K{beta}{sub 1} line of ytterbium through a near-coincident K-edge filter changes depending on plasma parameters that should affect the ionization. Systematic exploration of filter-line pairs like these could become a unique tool for diagnostics of suitable high energy density plasmas.

  14. Influence of the ionization-energy losses of high-energy bismuth ions on the development of helium blisters in silicon

    SciTech Connect

    Reutov, V. F. Dmitriev, S. N.; Sohatsky, A. S.; Zaluzhnyi, A. G.

    2015-10-15

    Understanding the behavior of helium in solids under conditions of intense ionizing radiation is of particular interest in solving many problems of nuclear, fusion, and space materials science and also in microelectronics. The observed effect of suppressing the formation of helium blisters on the surface of helium ion-doped silicon as a result of irradiation with high-energy bismuth ions is reported in this publication. It is suggested that a possible decrease in the concentration of helium atoms in silicon is due to their radiationinduced desorption from the area of doping in terms of the high-impact ionization of bismuth ions.

  15. A Critical Compilation of Energy Levels, Spectral Lines, and Transition Probabilities of Singly Ionized Silver, Ag II.

    PubMed

    Kramida, Alexander

    2013-01-01

    All available experimental measurements of the spectrum of the Ag(+) ion are critically reviewed. Systematic shifts are removed from the measured wavelengths. The compiled list of critically evaluated wavelengths is used to derive a comprehensive list of energy levels with well-defined uncertainties. Eigenvector compositions and level designations are found in two alternate coupling schemes. Some of the older work is found to be incorrect. A revised value of the ionization energy, 173283(7) cm(-1), equivalent to 21.4844(8) eV, is derived from the new energy levels. A set of critically evaluated transition probabilities is given.

  16. Ion kinetic energy distributions and cross sections for the electron impact ionization of ethyl tert-butyl ether

    NASA Astrophysics Data System (ADS)

    Di Palma, T. M.; Apicella, B.; Armenante, M.; Velotta, R.; Wang, X.; Spinelli, N.

    2005-11-01

    The kinetic energy distributions and the cross sections of the ions produced in the electron impact of ethyl tert-butyl ether (ETBE) have been studied by time of flight (TOF) mass spectrometry. The kinetic energy distributions have been deduced from the TOF peak shape analysis and a Montecarlo simulation method of the ion trajectories has been used to evaluate the collection efficiency of the spectrometer as a function of the ion initial kinetic energy. The measured ion yields have been corrected for the collection efficiency and the partial and total ionization cross sections of ETBE determined in the range 20-150 eV.

  17. A Critical Compilation of Energy Levels, Spectral Lines, and Transition Probabilities of Singly Ionized Silver, Ag II

    PubMed Central

    Kramida, Alexander

    2013-01-01

    All available experimental measurements of the spectrum of the Ag+ ion are critically reviewed. Systematic shifts are removed from the measured wavelengths. The compiled list of critically evaluated wavelengths is used to derive a comprehensive list of energy levels with well-defined uncertainties. Eigenvector compositions and level designations are found in two alternate coupling schemes. Some of the older work is found to be incorrect. A revised value of the ionization energy, 173283(7) cm−1, equivalent to 21.4844(8) eV, is derived from the new energy levels. A set of critically evaluated transition probabilities is given. PMID:26401429

  18. Construction of an ionization chamber for the measurement of dose of low energy x-rays

    SciTech Connect

    Perez, Y. B. Alcantara; Jimenez, F. J. Ramirez

    2008-08-11

    We designed and constructed the prototype of an ionization chamber to measure the dose of an X-ray tube with Molybdenum anode. This X-ray tube is located in the Physics department at CINVESTAV and is used for medical physics purposes in the imaging area. The ionization chamber is designed to measure doses on biological samples exposed to X-rays and will be applied in radiation protection studies.

  19. Testing an excited-state energy density functional and the associated potential with the ionization potential theorem

    NASA Astrophysics Data System (ADS)

    Hemanadhan, M.; Shamim, Md; Harbola, Manoj K.

    2014-06-01

    The modified local spin density (MLSD) functional and the related local potential for excited states is tested by employing the ionization potential theorem. The exchange functional for an excited state is constructed by splitting k-space. Since its functional derivative cannot be obtained easily, the corresponding exchange potential is given by an analogy to its ground-state counterpart. Further, to calculate the highest occupied orbital energy ɛmax accurately, the potential is corrected for its asymptotic behaviour by employing the van Leeuwen and Baerends (LB) correction to it. ɛmax so obtained is then compared with the ΔSCF ionization energy calculated using the MLSD functional with self-interaction correction for the orbitals involved in the transition. It is shown that the two match quite accurately. The match becomes even better by tuning the LB correction with respect to a parameter in it.

  20. Low-energy structure of above-threshold-ionization electron spectra: Role of the Coulomb threshold effect

    NASA Astrophysics Data System (ADS)

    Telnov, Dmitry A.; Chu, Shih-I.

    2011-06-01

    Recent experimental observations of above-threshold ionization of rare gas atoms and diatomic molecules by midinfrared laser fields [C. I. Blaga , Nat. Phys.PRLTAO1745-247310.1038/nphys1228 5, 335 (2009); W. Quan , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.103.093001 103, 093001 (2009)] revealed a prominent maximum in the electron energy spectrum very close to the ionization threshold which is not reproduced by widely used Keldysh-Faisal-Reiss theories. We have performed fully ab initio theoretical analysis and precision calculations to explore the quantum origin of the low-energy structure (LES) observed in the experiments. Our study shows that an important role in shaping of LES is played by the effect of Coulomb attraction in the final electron state and the Coulomb threshold effect.

  1. Pulsed-field ionization zero electron kinetic energy spectrum of the ground electronic state of BeOBe+.

    PubMed

    Antonov, Ivan O; Barker, Beau J; Heaven, Michael C

    2011-01-28

    The ground electronic state of BeOBe(+) was probed using the pulsed-field ionization zero electron kinetic energy photoelectron technique. Spectra were rotationally resolved and transitions to the zero-point level, the symmetric stretch fundamental and first two bending vibrational levels were observed. The rotational state symmetry selection rules confirm that the ground electronic state of the cation is (2)Σ(g)(+). Detachment of an electron from the HOMO of neutral BeOBe results in little change in the vibrational or rotational constants, indicating that this orbital is nonbonding in nature. The ionization energy of BeOBe [65480(4) cm(-1)] was refined over previous measurements. Results from recent theoretical calculations for BeOBe(+) (multireference configuration interaction) were found to be in good agreement with the experimental data.

  2. Single differential electron impact ionization cross sections in the binary-encounter-Bethe approximation for the low binding energy regime

    NASA Astrophysics Data System (ADS)

    Guerra, M.; Amaro, P.; Machado, J.; Santos, J. P.

    2015-09-01

    An analytical expression based on the binary-encounter-Bethe model for energy differential cross sections in the low binding energy regime is presented. Both the binary-encounter-Bethe model and its modified counterpart are extended to shells with very low binding energy by removing the constraints in the interference term of the Mott cross section, originally introduced by Kim et al. The influence of the ionic factor is also studied for such targets. All the binary-encounter-Bethe based models presented here are checked against experimental results of low binding energy targets, such as the total ionization cross sections of alkali metals. The energy differential cross sections for H and He, at several incident energies, are also compared to available experimental and theoretical values.

  3. Benzylammonium Thermometer Ions: Internal Energies of Ions Formed by Low Temperature Plasma and Atmospheric Pressure Chemical Ionization

    NASA Astrophysics Data System (ADS)

    Stephens, Edward R.; Dumlao, Morphy; Xiao, Dan; Zhang, Daming; Donald, William A.

    2015-12-01

    The extent of internal energy deposition upon ion formation by low temperature plasma and atmospheric pressure chemical ionization was investigated using novel benzylammonium thermometer ions. C-N heterolytic bond dissociation enthalpies of nine 4-substituted benzylammoniums were calculated using CAM-B3LYP/6-311++G(d,p), which was significantly more accurate than B3LYP/6-311++G(d,p), MP2/6-311++G(d,p), and CBS-QB3 for calculating the enthalpies of 20 heterolytic dissociation reactions that were used to benchmark theory. All 4-substituted benzylammonium thermometer ions fragmented by a single pathway with comparable dissociation entropies, except 4-nitrobenzylammonium. Overall, the extent of energy deposition into ions formed by low temperature plasma was significantly lower than those formed by atmospheric pressure chemical ionization under these conditions. Because benzylamines are volatile, this new suite of thermometer ions should be useful for investigating the extent of internal energy deposition during ion formation for a wide range of ionization methods, including plasma, spray and laser desorption-based techniques.

  4. Benzylammonium Thermometer Ions: Internal Energies of Ions Formed by Low Temperature Plasma and Atmospheric Pressure Chemical Ionization.

    PubMed

    Stephens, Edward R; Dumlao, Morphy; Xiao, Dan; Zhang, Daming; Donald, William A

    2015-12-01

    The extent of internal energy deposition upon ion formation by low temperature plasma and atmospheric pressure chemical ionization was investigated using novel benzylammonium thermometer ions. C-N heterolytic bond dissociation enthalpies of nine 4-substituted benzylammoniums were calculated using CAM-B3LYP/6-311++G(d,p), which was significantly more accurate than B3LYP/6-311++G(d,p), MP2/6-311++G(d,p), and CBS-QB3 for calculating the enthalpies of 20 heterolytic dissociation reactions that were used to benchmark theory. All 4-substituted benzylammonium thermometer ions fragmented by a single pathway with comparable dissociation entropies, except 4-nitrobenzylammonium. Overall, the extent of energy deposition into ions formed by low temperature plasma was significantly lower than those formed by atmospheric pressure chemical ionization under these conditions. Because benzylamines are volatile, this new suite of thermometer ions should be useful for investigating the extent of internal energy deposition during ion formation for a wide range of ionization methods, including plasma, spray and laser desorption-based techniques. Graphical Abstract ᅟ.

  5. Long-range energy transfer and ionization in extended quantum systems driven by ultrashort spatially shaped laser pulses.

    PubMed

    Paramonov, Guennaddi K; Bandrauk, André D; Kühn, Oliver

    2011-05-21

    The processes of ionization and energy transfer in a quantum system composed of two distant H atoms with an initial internuclear separation of 100 atomic units (5.29 nm) have been studied by the numerical solution of the time-dependent Schrödinger equation beyond the Born-Oppenheimer approximation. Thereby it has been assumed that only one of the two H atoms was excited by temporally and spatially shaped laser pulses at various laser carrier frequencies. The quantum dynamics of the extended H-H system, which was taken to be initially either in an unentangled or an entangled ground state, has been explored within a linear three-dimensional model, including the two z coordinates of the electrons and the internuclear distance R. An efficient energy transfer from the laser-excited H atom (atom A) to the other H atom (atom B) and the ionization of the latter have been found. It has been shown that the physical mechanisms of the energy transfer as well as of the ionization of atom B are the Coulomb attraction of the laser driven electron of atom A by the proton of atom B and a short-range Coulomb repulsion of the two electrons when their wave functions strongly overlap in the domain of atom B.

  6. Application of high-resolution photoelectron spectroscopy: Vibrational resolved C 1s and O 1s spectra of CO adsorbed on Ni(100)

    SciTech Connect

    Foehlisch, A.; Nilsson, A.; Martensson, N.

    1997-04-01

    There are various effects which determine the line shape of a core-level electron spectrum. These are due to the finite life-time of the core hole, inelastic scattering of the outgoing photoelectron, electronic shake-up and shake-off processes and vibrational excitations. For free atoms and molecules the different contributions to the observed line shapes can often be well separated. For solids, surfaces and adsorbates the line shapes are in general much broader and it has in the past been assumed that no separation of the various contributions can be made. In the present report the authors will show that this is indeed not the case. Surprisingly, the vibrational fine structure of CO adsorbed on Ni(100) can be resolved in the C 1s and O 1s electron spectra. This was achieved by the combination of highly monochromatized soft X-rays from B18.0 with a high resolution Scienta 200 mm photoelectron spectrometer. X-ray photoelectron spectroscopy (XPS) with tunable excitation energy yields as a core level spectroscopy atomic and site-specific information. The presented measurements allow for a determination of internuclear distances and potential energy curves in corehole ionized adsorbed molecules. The authors analysis of the c(2x2) phase CO/Ni(100) on {open_quotes}top{close_quotes} yielded a vibrational splitting of 217 +/- 2 meV for C 1s ionization. For O 1s ionization a splitting of 173 +/- 8 meV was found.

  7. Measurements of neutron energy using a recoil-proton telescope and a high-pressure ionization chamber.

    PubMed

    Folkard, M; Makrigiorgos, G; Roper, M J; Waker, A J; Michael, B D

    1989-04-01

    Two very different techniques for measuring the energy of neutrons in the energy range 0.1-10 MeV are presented and compared. A recoil-proton spectrometer is used to determine the energy spectra of neutrons produced by the d(4)-Be and p(4)-Be reactions down to the low-energy threshold of 0.7 MeV. The same radiation fields are also measured with a recently developed method using a high-pressure ionization chamber that can be used to determine the mean energy of the neutrons in a mixed neutron-gamma radiation field provided the gamma-ray absorbed dose fraction is determined independently. An intercomparison of the two methods shows that the high-pressure ionization chamber compares well and supplements the established recoil-proton spectrometer technique. The almost isotropic response of the chamber has enabled measurements to be made of the variation of mean neutron energy with depth in water for the two radiation fields.

  8. Agrp neurons mediate Sirt1's action on the melanocortin system and energy balance: roles for Sirt1 in neuronal firing and synaptic plasticity.

    PubMed

    Dietrich, Marcelo O; Antunes, Catiele; Geliang, Gan; Liu, Zhong-Wu; Borok, Erzsebet; Nie, Yongzhan; Xu, Allison W; Souza, Diogo O; Gao, Qian; Diano, Sabrina; Gao, Xiao-Bing; Horvath, Tamas L

    2010-09-01

    Sirt1 has been associated with various effects of calorie restriction, including an increase in lifespan. Here we show in mice that a central regulatory component in energy metabolism, the hypothalamic melanocortin system, is affected by Sirt1, which promotes the activity and connectivity of this system resulting in negative energy balance. In adult mice, the pharmacological inhibition of brain Sirt1 activity decreased Agrp neuronal activity and the inhibitory tone on the anorexigenic POMC neurons, as measured by the number of synaptic inputs to these neurons. When a Sirt1 inhibitor (EX-527) was injected either peripherally (i.p., 10 mg/kg) or directly into the brain (i.c.v., 1.5 nmol/mouse), it decreased both food intake during the dark cycle and ghrelin-induced food intake. This effect on feeding is mediated by upstream melanocortin receptors, because the MC4R antagonist, SHU9119, reversed Sirt1's effect on food intake. This action of Sirt1 required an appropriate shift in the mitochondrial redox state: in the absence of such an adaptation enabled by the mitochondrial protein, UCP2, Sirt1-induced cellular and behavioral responses were impaired. In accordance with the pharmacological results, the selective knock-out of Sirt1 in hypothalamic Agrp neurons through the use of Cre-Lox technology decreased electric responses of Agrp neurons to ghrelin and decreased food intake, leading to decreased lean mass, fat mass, and body weight. The present data indicate that Sirt1 has a central mode of action by acting on the NPY/Agrp neurons to affect body metabolism.

  9. Metal-Sulfur Valence Orbital Interaction Energies in Metal–Dithiolene Complexes: Determination of Charge and Overlap Interaction Energies by Comparison of Core and Valence Ionization Energy Shifts

    PubMed Central

    Wiebelhaus, Nicholas J.; Cranswick, Matthew A.; Klein, Eric L.; Lockett, L. Tori; Lichtenberger, Dennis L.; Enemark, John H.

    2011-01-01

    The electronic interactions between metals and dithiolenes are important in the biological processes of many metalloenzymes as well as in diverse chemical and material applications. Of special note is the ability of the dithiolene ligand to support metal centers in multiple coordination environments and oxidation states. To better understand the nature of metal-dithiolene electronic interactions, new capabilities in gas-phase core photoelectron spectroscopy for molecules with high sublimation temperatures have been developed and applied to a series of molecules of the type Cp2M(bdt) (Cp = η5-cyclopentadienyl, M = Ti, V, Mo, and bdt = benzenedithiolato). Comparison of the gas-phase core and valence ionization energy shifts provides a unique quantitative energy measure of valence orbital overlap interactions between the metal and sulfur orbitals that is separated from the effects of charge redistribution. The results explain the large amount of sulfur character in the redox-active orbitals and the ‘leveling’ of oxidation state energies in metal-dithiolene systems. The experimentally-determined orbital interaction energies reveal a previously unidentified overlap interaction of the predominantly sulfur HOMO of the bdt ligand with filled π orbitals of the Cp ligands, suggesting that direct dithiolene interactions with other ligands bound to the metal could be significant for other metal-dithiolene systems in chemistry and biology. PMID:21988484

  10. Scaling Laws of the Two-Electron Sum-Energy Spectrum in Strong-Field Double Ionization.

    PubMed

    Ye, Difa; Li, Min; Fu, Libin; Liu, Jie; Gong, Qihuang; Liu, Yunquan; Ullrich, J

    2015-09-18

    The sum-energy spectrum of two correlated electrons emitted in nonsequential strong-field double ionization (SFDI) of Ar was studied for intensities of 0.3 to 2×10^{14} W/cm^{2}. We find the mean sum energy, the maximum of the distributions as well as the high-energy tail of the scaled (to the ponderomotive energy) spectra increase with decreasing intensity below the recollision threshold (BRT). At higher intensities the spectra collapse into a single distribution. This behavior can be well explained within a semiclassical model providing clear evidence of the importance of multiple recollisions in the BRT regime. Here, ultrafast thermalization between both electrons is found occurring within three optical cycles only and leaving its clear footprint in the sum-energy spectra.

  11. Penning type of ionizing energy transfer collisions in a Hg-Ar discharge detected by the optogalvanic effect

    NASA Technical Reports Server (NTRS)

    Reddy, B. R.; Venkateswarlu, P.; George, M. C.

    1989-01-01

    The temporal evolution of the optogalvanic signals has been investigated in detail in a Hg-argon discharge by irradiating it with an excimer pumped dye laser. The signals at 4510.7, 4596 and 4628.4 A exhibited anomalous behavior. Analysis of the data revealed that the excited Ar and Hg atoms respectively in the 1P1 and 3P1 states participated in energy transfer collisions, causing atomic mercury to excite to an ionized energy state, while simultaneously the argon atom relaxes to its ground state.

  12. Dependence with air density of the response of the PTW SourceCheck ionization chamber for low energy brachytherapy sources.

    PubMed

    Tornero-López, Ana M; Guirado, Damián; Perez-Calatayud, Jose; Ruiz-Arrebola, Samuel; Simancas, Fernando; Gazdic-Santic, Maja; Lallena, Antonio M

    2013-12-01

    Air-communicating well ionization chambers are commonly used to assess air kerma strength of sources used in brachytherapy. The signal produced is supposed to be proportional to the air density within the chamber and, therefore, a density-independent air kerma strength is obtained when the measurement is corrected to standard atmospheric conditions using the usual temperature and pressure correction factor. Nevertheless, when assessing low energy sources, the ionization chambers may not fulfill that condition and a residual density dependence still remains after correction. In this work, the authors examined the behavior of the PTW 34051 SourceCheck ionization chamber when measuring the air kerma strength of (125)I seeds. Four different SourceCheck chambers were analyzed. With each one of them, two series of measurements of the air kerma strength for (125)I selectSeed(TM) brachytherapy sources were performed inside a pressure chamber and varying the pressure in a range from 747 to 1040 hPa (560 to 780 mm Hg). The temperature and relative humidity were kept basically constant. An analogous experiment was performed by taking measurements at different altitudes above sea level. Contrary to other well-known ionization chambers, like the HDR1000 PLUS, in which the temperature-pressure correction factor overcorrects the measurements, in the SourceCheck ionization chamber they are undercorrected. At a typical atmospheric situation of 933 hPa (700 mm Hg) and 20 °C, this undercorrection turns out to be 1.5%. Corrected measurements show a residual linear dependence on the density and, as a consequence, an additional density dependent correction must be applied. The slope of this residual linear density dependence is different for each SourceCheck chamber investigated. The results obtained by taking measurements at different altitudes are compatible with those obtained with the pressure chamber. Variations of the altitude and changes in the weather conditions may produce

  13. Particle and energy dependence of the statistical fluctuations of an ionization chamber current

    NASA Astrophysics Data System (ADS)

    Purghel, Lidia; Vaˆlcov, Nicolae

    For the purpose of getting more detailed information concerning the processes leading to statistical fluctuations of an ionization chamber current, measurements with various radioactive sources have been done. By using the experimental arrangement described elsewhere [A. Necula et al. Nucl. Instr. and Meth. A 332 (1993) 501] the mean value and the standard deviation of the ionization current for 3H (water vapours), 60Co (sealed source), 85Kr (gas), 204Tl (8 mm diameter disk) and 239Pu (10 mm diameter disk), beta, gamma and alpha sources have been measured. A statistical model explaining the experimental data is proposed.

  14. Inner-shell ionization of potassium atoms ionized by a femtosecond laser

    SciTech Connect

    Hertlein, M. P.; Adaniya, H.; Amini, J.; Feinberg, B.; Prior, M. H.; Belkacem, A.; Bressler, C.; Kaiser, M.; Neumann, N.

    2006-06-15

    With a femtosecond laser pulse we rapidly ionize potassium atoms (K{sup 0}) in the gas phase, generating potassium ions (K{sup +}), and monitor the altered energy-level scheme with a subsequent hard x-ray pulse. Removal of the potassium 4s valence electron increases the binding energies of both the valence and the 1s core levels, and induces an ultrafast change of the 1s-4p x-ray transition energy by about 2.8 eV. We simultaneously observe a 50% increase in oscillator strength of K{sup +} over K{sup 0} for that transition.

  15. Inner-shell ionization of potassium atoms ionized by a femtosecond laser

    NASA Astrophysics Data System (ADS)

    Hertlein, M. P.; Adaniya, H.; Amini, J.; Bressler, C.; Feinberg, B.; Kaiser, M.; Neumann, N.; Prior, M. H.; Belkacem, A.

    2006-06-01

    With a femtosecond laser pulse we rapidly ionize potassium atoms (K0) in the gas phase, generating potassium ions (K+) , and monitor the altered energy-level scheme with a subsequent hard x-ray pulse. Removal of the potassium 4s valence electron increases the binding energies of both the valence and the 1s core levels, and induces an ultrafast change of the 1s-4p x-ray transition energy by about 2.8eV . We simultaneously observe a 50% increase in oscillator strength of K+ over K0 for that transition.

  16. Atmospheric energy input and ionization by energetic electrons during the geomagnetic storm of 8-9 November 1991

    NASA Technical Reports Server (NTRS)

    Chenette, D. L.; Datlowe, D. W.; Robinson, R. M.; Schumaker, T. L.; Vondrak, R. R.; Winningham, J. D.

    1993-01-01

    The Atmospheric X-ray Imaging Spectrometer (AXIS) of the Particle Environment Monitor investigation aboard the Upper Atmosphere Research Satellite monitors energy input to the upper atmosphere due to energetic electrons. Analysis of the AXIS data from the major geomagnetic storm of 8-9 November 1991 is presented. During the November storm, electrons above a few keV flowing into a substantially expanded auroral zone provided the bulk of the ionizing power to the upper atmosphere. At the peak of the disturbance the total AXIS-observed power reached 40 GW. On 9 November the whole day average atmospheric ionization rate in the auroral zone at 80 km altitude exceeded the rate due to solar UV and solar X-rays by a factor of over 10 to 100.

  17. Electron energy enhancement by frequency chirp of a radially polarized laser pulse during ionization of low-density gases

    NASA Astrophysics Data System (ADS)

    Pal Singh, Kunwar; Arya, Rashmi; Malik, Anil K.; Fisch, N. J.

    2016-11-01

    A scheme is proposed to enhance the energy of the electrons generated during the ionization of low-density krypton ions \\text{K}{{\\text{r}}32+} and argon ions \\text{A}{{\\text{r}}16+} by a radially polarized laser pulse using a negative frequency chirp. If a suitable frequency chirp is introduced then the energy of the electrons increases significantly and scattering decreases. The optimum value of the frequency chirp decreases with laser intensity and as well as spot size. The laser spot size also has an optimum value. The electron energy shows strong initial phase dependence. The scheme can be used to obtain quasi-monoenergetic collimated \\text{MeV}/\\text{GeV} electrons using the right choice of parameters. The chirped radially polarized laser pulse is more efficient than a chirped circularly polarized laser pulse to enhance energy and obtain quasi-monoenergetic electron beams.

  18. Calculating pH-dependent free energy of proteins by using Monte Carlo protonation probabilities of ionizable residues.

    PubMed

    Huang, Qiang; Herrmann, Andreas

    2012-03-01

    Protein folding, stability, and function are usually influenced by pH. And free energy plays a fundamental role in analysis of such pH-dependent properties. Electrostatics-based theoretical framework using dielectric solvent continuum model and solving Poisson-Boltzmann equation numerically has been shown to be very successful in understanding the pH-dependent properties. However, in this approach the exact computation of pH-dependent free energy becomes impractical for proteins possessing more than several tens of ionizable sites (e.g. > 30), because exact evaluation of the partition function requires a summation over a vast number of possible protonation microstates. Here we present a method which computes the free energy using the average energy and the protonation probabilities of ionizable sites obtained by the well-established Monte Carlo sampling procedure. The key feature is to calculate the entropy by using the protonation probabilities. We used this method to examine a well-studied protein (lysozyme) and produced results which agree very well with the exact calculations. Applications to the optimum pH of maximal stability of proteins and protein-DNA interactions have also resulted in good agreement with experimental data. These examples recommend our method for application to the elucidation of the pH-dependent properties of proteins.

  19. Evidence for e+e-→γ ηc(1 S ) at center-of-mass energies between 4.01 and 4.60 GeV

    NASA Astrophysics Data System (ADS)

    Ablikim, M.; Achasov, M. N.; Ahmed, S.; Albrecht, M.; Alekseev, M.; Amoroso, A.; An, F. F.; An, Q.; Bai, J. Z.; Bai, Y.; Bakina, O.; Baldini Ferroli, R.; Ban, Y.; Bennett, D. W.; Bennett, J. V.; Berger, N.; Bertani, M.; Bettoni, D.; Bian, J. M.; Bianchi, F.; Boger, E.; Boyko, I.; Briere, R. A.; Cai, H.; Cai, X.; Cakir, O.; Calcaterra, A.; Cao, G. F.; Cetin, S. A.; Chai, J.; Chang, J. F.; Chelkov, G.; Chen, G.; Chen, H. S.; Chen, J. C.; Chen, M. L.; Chen, S. J.; Chen, X. R.; Chen, Y. B.; Chu, X. K.; Cibinetto, G.; Dai, H. L.; Dai, J. P.; Dbeyssi, A.; Dedovich, D.; Deng, Z. Y.; Denig, A.; Denysenko, I.; Destefanis, M.; de Mori, F.; Ding, Y.; Dong, C.; Dong, J.; Dong, L. Y.; Dong, M. Y.; Dorjkhaidav, O.; Dou, Z. L.; Du, S. X.; Duan, P. F.; Fang, J.; Fang, S. S.; Fang, X.; Fang, Y.; Farinelli, R.; Fava, L.; Fegan, S.; Feldbauer, F.; Felici, G.; Feng, C. Q.; Fioravanti, E.; Fritsch, M.; Fu, C. D.; Gao, Q.; Gao, X. L.; Gao, Y.; Gao, Y. G.; Gao, Z.; Garillon, B.; Garzia, I.; Goetzen, K.; Gong, L.; Gong, W. X.; Gradl, W.; Greco, M.; Gu, M. H.; Gu, S.; Gu, Y. T.; Guo, A. Q.; Guo, L. B.; Guo, R. P.; Guo, Y. P.; Haddadi, Z.; Han, S.; Hao, X. Q.; Harris, F. A.; He, K. L.; He, X. Q.; Heinsius, F. H.; Held, T.; Heng, Y. K.; Holtmann, T.; Hou, Z. L.; Hu, C.; Hu, H. M.; Hu, T.; Hu, Y.; Huang, G. S.; Huang, J. S.; Huang, S. H.; Huang, X. T.; Huang, X. Z.; Huang, Z. L.; Hussain, T.; Ikegami Andersson, W.; Ji, Q.; Ji, Q. P.; Ji, X. B.; Ji, X. L.; Jiang, X. S.; Jiang, X. Y.; Jiao, J. B.; Jiao, Z.; Jin, D. P.; Jin, S.; Jin, Y.; Johansson, T.; Julin, A.; Kalantar-Nayestanaki, N.; Kang, X. L.; Kang, X. S.; Kavatsyuk, M.; Ke, B. C.; Khan, T.; Khoukaz, A.; Kiese, P.; Kliemt, R.; Koch, L.; Kolcu, O. B.; Kopf, B.; Kornicer, M.; Kuemmel, M.; Kuhlmann, M.; Kupsc, A.; Kühn, W.; Lange, J. S.; Lara, M.; Larin, P.; Lavezzi, L.; Leithoff, H.; Leng, C.; Li, C.; Li, Cheng; Li, D. M.; Li, F.; Li, F. Y.; Li, G.; Li, H. B.; Li, H. J.; Li, J. C.; Li, Jin; Li, K.; Li, K.; Li, K. J.; Li, Lei; Li, P. L.; Li, P. R.; Li, Q. Y.; Li, T.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. N.; Li, X. Q.; Li, Z. B.; Liang, H.; Liang, Y. F.; Liang, Y. T.; Liao, G. R.; Lin, D. X.; Liu, B.; Liu, B. J.; Liu, C. X.; Liu, D.; Liu, F. H.; Liu, Fang; Liu, Feng; Liu, H. B.; Liu, H. H.; Liu, H. H.; Liu, H. M.; Liu, J. B.; Liu, J. Y.; Liu, K.; Liu, K. Y.; Liu, Ke; Liu, L. D.; Liu, P. L.; Liu, Q.; Liu, S. B.; Liu, X.; Liu, Y. B.; Liu, Z. A.; Liu, Zhiqing; Long, Y. F.; Lou, X. C.; Lu, H. J.; Lu, J. G.; Lu, Y.; Lu, Y. P.; Luo, C. L.; Luo, M. X.; Luo, X. L.; Lyu, X. R.; Ma, F. C.; Ma, H. L.; Ma, L. L.; Ma, M. M.; Ma, Q. M.; Ma, T.; Ma, X. N.; Ma, X. Y.; Ma, Y. M.; Maas, F. E.; Maggiora, M.; Malik, Q. A.; Mao, Y. J.; Mao, Z. P.; Marcello, S.; Meng, Z. X.; Messchendorp, J. G.; Mezzadri, G.; Min, J.; Min, T. J.; Mitchell, R. E.; Mo, X. H.; Mo, Y. J.; Morales Morales, C.; Morello, G.; Muchnoi, N. Yu.; Muramatsu, H.; Mustafa, A.; Nefedov, Y.; Nerling, F.; Nikolaev, I. B.; Ning, Z.; Nisar, S.; Niu, S. L.; Niu, X. Y.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Pan, Y.; Papenbrock, M.; Patteri, P.; Pelizaeus, M.; Pellegrino, J.; Peng, H. P.; Peters, K.; Pettersson, J.; Ping, J. L.; Ping, R. G.; Pitka, A.; Poling, R.; Prasad, V.; Qi, H. R.; Qi, M.; Qi, T. Y.; Qian, S.; Qiao, C. F.; Qin, N.; Qin, X. S.; Qin, Z. H.; Qiu, J. F.; Rashid, K. H.; Redmer, C. F.; Richter, M.; Ripka, M.; Rolo, M.; Rong, G.; Rosner, Ch.; Sarantsev, A.; Savrié, M.; Schnier, C.; Schoenning, K.; Shan, W.; Shao, M.; Shen, C. P.; Shen, P. X.; Shen, X. Y.; Sheng, H. Y.; Shepherd, M. R.; Song, J. J.; Song, W. M.; Song, X. Y.; Sosio, S.; Sowa, C.; Spataro, S.; Sun, G. X.; Sun, J. F.; Sun, L.; Sun, S. S.; Sun, X. H.; Sun, Y. J.; Sun, Y. K.; Sun, Y. Z.; Sun, Z. J.; Sun, Z. T.; Tang, C. J.; Tang, G. Y.; Tang, X.; Tapan, I.; Tiemens, M.; Tsednee, B. T.; Uman, I.; Varner, G. S.; Wang, B.; Wang, B. L.; Wang, D.; Wang, D. Y.; Wang, Dan; Wang, K.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, W. P.; Wang, X. F.; Wang, Y.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Z.; Wang, Z. G.; Wang, Z. H.; Wang, Z. Y.; Wang, Z. Y.; Weber, T.; Wei, D. H.; Wei, J. H.; Weidenkaff, P.; Wen, S. P.; Wiedner, U.; Wolke, M.; Wu, L. H.; Wu, L. J.; Wu, Z.; Xia, L.; Xia, Y.; Xiao, D.; Xiao, H.; Xiao, Y. J.; Xiao, Z. J.; Xie, X. H.; Xie, Y. G.; Xie, Y. H.; Xiong, X. A.; Xiu, Q. L.; Xu, G. F.; Xu, J. J.; Xu, L.; Xu, Q. J.; Xu, Q. N.; Xu, X. P.; Yan, L.; Yan, W. B.; Yan, W. C.; Yan, Y. H.; Yang, H. J.; Yang, H. X.; Yang, L.; Yang, Y. H.; Yang, Y. X.; Ye, M.; Ye, M. H.; Yin, J. H.; You, Z. Y.; Yu, B. X.; Yu, C. X.; Yu, J. S.; Yuan, C. Z.; Yuan, Y.; Yuncu, A.; Zafar, A. A.; Zeng, Y.; Zeng, Z.; Zhang, B. X.; Zhang, B. Y.; Zhang, C. C.; Zhang, D. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J.; Zhang, J. L.; Zhang, J. Q.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, K.; Zhang, L.; Zhang, S. Q.; Zhang, X. Y.; Zhang, Y.; Zhang, Y.; Zhang, Y. H.; Zhang, Y. T.; Zhang, Yu; Zhang, Z. H.; Zhang, Z. P.; Zhang, Z. Y.; Zhao, G.; Zhao, J. W.; Zhao, J. Y.; Zhao, J. Z.; Zhao, Lei; Zhao, Ling; Zhao, M. G.; Zhao, Q.; Zhao, S. J.; Zhao, T. C.; Zhao, Y. B.; Zhao, Z. G.; Zhemchugov, A.; Zheng, B.; Zheng, J. P.; Zheng, W. J.; Zheng, Y. H.; Zhong, B.; Zhou, L.; Zhou, X.; Zhou, X. K.; Zhou, X. R.; Zhou, X. Y.; Zhu, J.; Zhu, K.; Zhu, K. J.; Zhu, S.; Zhu, S. H.; Zhu, X. L.; Zhu, Y. C.; Zhu, Y. S.; Zhu, Z. A.; Zhuang, J.; Zou, B. S.; Zou, J. H.; Besiii Collaboration

    2017-09-01

    We present first evidence for the process e+e-→γ ηc(1 S ) at six center-of-mass energies between 4.01 and 4.60 GeV using data collected by the BESIII experiment operating at BEPCII. We measure the Born cross section at each energy using a combination of twelve ηc(1 S ) decay channels. We also combine all six energies under various assumptions for the energy-dependence of the cross section. If the process is assumed to proceed via the Y (4260 ), we measure a peak Born cross section σpeak(e+e-→γ ηc(1 S ))=2.11 ±0.49 (stat . )±0.36 (syst . ) pb with a statistical significance of 4.2 σ .

  20. Site-specific fragmentation caused by core-level photoionization in F(3)SiCH(2)CH(2)Si(CH(3))(3) vapor: comparison between Si:1s and 2p photoionizations by means of photoelectron-photoion-photoion triple-coincidence spectroscopy.

    PubMed

    Nagaoka, Shin-ichi; Takemoto, Mai; Prümper, Georg; Fukuzawa, Hironobu; Tamenori, Yusuke; Suzuki, Isao H; Ueda, Kiyoshi

    2008-11-28

    Site-specific fragmentation caused by Si:1s and 2p core-level photoionizations in F(3)SiCH(2)CH(2)Si(CH(3))(3) vapor was studied by energy-selected-photoelectron photoion-photoion triple-coincidence spectroscopy. The difference between the chemical shifts of the two Si sites is larger for the 1s ionization than for the 2p (2s) ionization. The fragmentation caused by the Si:1s ionization is more violent than that caused by the Si:2p ionization. The ions and ion pairs showing high site specificity for the Si:1s ionization belong to small fragments compared to those in the Si:2p ionization. Criteria for high site-specificity in fragmentation are discussed in conjunction with the present results.

  1. Direct Delta-MBPT(2) method for ionization potentials, electron affinities, and excitation energies using fractional occupation numbers

    SciTech Connect

    Beste, Ariana; Vazquez-Mayagoitia, Alvaro; Ortiz, J. Vincent

    2013-01-01

    A direct method (D-Delta-MBPT(2)) to calculate second-order ionization potentials (IPs), electron affinities (EAs), and excitation energies is developed. The Delta-MBPT(2) method is defined as the correlated extension of the Delta-HF method. Energy differences are obtained by integrating the energy derivative with respect to occupation numbers over the appropriate parameter range. This is made possible by writing the second-order energy as a function of the occupation numbers. Relaxation effects are fully included at the SCF level. This is in contrast to linear response theory, which makes the D-Delta-MBPT(2) applicable not only to single excited but also higher excited states. We show the relationship of the D-Delta-MBPT(2) method for IPs and EAs to a second-order approximation of the effective Fock-space coupled-cluster Hamiltonian and a second-order electron propagator method. We also discuss the connection between the D-Delta-MBPT(2) method for excitation energies and the CIS-MP2 method. Finally, as a proof of principle, we apply our method to calculate ionization potentials and excitation energies of some small molecules. For IPs, the Delta-MBPT(2) results compare well to the second-order solution of the Dyson equation. For excitation energies, the deviation from EOM-CCSD increases when correlation becomes more important. When using the numerical integration technique, we encounter difficulties that prevented us from reaching the Delta-MBPT(2) values. Most importantly, relaxation beyond the Hartree Fock level is significant and needs to be included in future research.

  2. Pulsed-field ionization electron spectroscopy and binding energies of alkali metal-dimethyl ether and -dimethoxyethane complexes.

    PubMed

    Sohnlein, Bradford R; Li, Shenggang; Fuller, Jason F; Yang, Dong-Sheng

    2005-07-01

    Lithium and sodium complexes of dimethyl ether (DME) and dimethoxyethane (DXE) were produced by reactions of laser-vaporized metal atoms with organic vapors in a pulsed nozzle cluster source. The mono-ligand complexes were studied by photoionization and pulsed field ionization zero electron kinetic energy (ZEKE) spectroscopy. Vibrationally resolved ZEKE spectra were obtained for Li(DME), Na(DME) and Li(DXE) and a photoionization efficiency spectrum for Na(DXE). The ZEKE spectra were analyzed by comparing with the spectra of other metal-ether complexes and with electronic structure calculations and spectral simulations. Major vibrations measured for the M(DME) (M=Li,Na) ions were M-O and C-O stretches and M-O-C and C-O-C bends. These vibrations and additional O-Li-O and O-C-C-O bends were observed for the Li(DXE) ion. The M(DME) complexes were in C2v symmetry with the metal atom binding to oxygen, whereas Li(DXE) was in a C2 ring configuration with the Li atom attaching to both oxygen atoms. Moreover, the ionization energies of these complexes were measured from the ZEKE or photoionization spectra and bond dissociation energies were derived from a thermodynamic cycle.

  3. Pulsed-field ionization electron spectroscopy and binding energies of alkali metal-dimethyl ether and -dimethoxyethane complexes

    NASA Astrophysics Data System (ADS)

    Sohnlein, Bradford R.; Li, Shenggang; Fuller, Jason F.; Yang, Dong-Sheng

    2005-07-01

    Lithium and sodium complexes of dimethyl ether (DME) and dimethoxyethane (DXE) were produced by reactions of laser-vaporized metal atoms with organic vapors in a pulsed nozzle cluster source. The mono-ligand complexes were studied by photoionization and pulsed field ionization zero electron kinetic energy (ZEKE) spectroscopy. Vibrationally resolved ZEKE spectra were obtained for Li(DME), Na(DME) and Li(DXE) and a photoionization efficiency spectrum for Na(DXE). The ZEKE spectra were analyzed by comparing with the spectra of other metal-ether complexes and with electronic structure calculations and spectral simulations. Major vibrations measured for the M(DME) (M=Li,Na) ions were M-O and C-O stretches and M-O-C and C-O-C bends. These vibrations and additional O-Li-O and O-C-C-O bends were observed for the Li(DXE) ion. The M(DME) complexes were in C2v symmetry with the metal atom binding to oxygen, whereas Li(DXE) was in a C2 ring configuration with the Li atom attaching to both oxygen atoms. Moreover, the ionization energies of these complexes were measured from the ZEKE or photoionization spectra and bond dissociation energies were derived from a thermodynamic cycle.

  4. Ionization potentials, electron affinities, resonance excitation energies, oscillator strengths, and ionic radii of element Uus (Z = 117) and astatine.

    PubMed

    Chang, Zhiwei; Li, Jiguang; Dong, Chenzhong

    2010-12-30

    Multiconfiguration Dirac-Fock (MCDF) method was employed to calculate the first five ionization potentials, electron affinities, resonance excitation energies, oscillator strengths, and radii for the element Uus and its homologue At. Main valence correlation effects were taken into account. The Breit interaction and QED effects were also estimated. The uncertainties of calculated IPs, EAs, and IR for Uus and At were reduced through an extrapolation procedure. The good consistency with available experimental and other theoretical values demonstrates the validity of the present results. These theoretical data therefore can be used to predict some unknown physicochemical properties of element Uus, Astatine, and their compounds.

  5. Ab initio approaches for the determination of heavy element energetics: Ionization energies of trivalent lanthanides (Ln = La-Eu)

    SciTech Connect

    Peterson, Charles; Penchoff, Deborah A.; Wilson, Angela K.

    2015-11-21

    An effective approach for the determination of lanthanide energetics, as demonstrated by application to the third ionization energy (in the gas phase) for the first half of the lanthanide series, has been developed. This approach uses a combination of highly correlated and fully relativistic ab initio methods to accurately describe the electronic structure of heavy elements. Both scalar and fully relativistic methods are used to achieve an approach that is both computationally feasible and accurate. The impact of basis set choice and the number of electrons included in the correlation space has also been examined.

  6. A balloon-borne ionization spectrometer with very large aperture for the detection of high energy cosmic rays

    NASA Technical Reports Server (NTRS)

    Atallah, K.; Modlinger, A.; Schmidt, W. K. H.; Cleghorn, T. F.

    1975-01-01

    A balloon experiment which was used to determine the chemical composition of very high-energy cosmic rays up to and beyond 100 GeV/nucleon is described. The detector had a geometric factor of 1 sq m sr and a total weight on the balloon of 2100 kg. The apparatus consisted of an ionization spectrometer, spark chambers, and plastic scintillation and Cherenkov counters. It was calibrated at CERN up to 24 GeV/c protons and at DESY up to 7 GeV/c electrons. In October 1972 it was flown successfully on a stratospheric balloon.

  7. Two-photon double ionization of helium in the region of photon energies 42-50eV

    NASA Astrophysics Data System (ADS)

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

    2007-03-01

    We report the total integrated cross section (TICS) of two-photon double ionization of helium in the photon energy range from 42to50eV . Our computational procedure relies on a numerical solution of the time-dependent Schrödinger equation on a square-integrable basis and subsequent projection of this solution on a set of final field-free states describing correlation in the two-electron continuum. Our results suggest that the TICS grows monotonically as a function of photon energy in the region of 42-50eV , possibly reaching a maximum in the vicinity of 50eV . We also present fully resolved triple-differential cross sections for selected photon energies.

  8. Diagnostic signature of low-energy secondary electron emission at the boundary of a partially-ionized plasma

    NASA Astrophysics Data System (ADS)

    Demidov, V. I.; Adams, S. F.; Kaganovich, I. D.; Koepke, M. E.; Kurlyandskaya, I. P.

    2015-09-01

    Effects of secondary electron emission (SEE) from a solid surface in contact with plasma are important for conducting and interpreting plasma experiments and modeling. Those effects are especially strong for contaminated surfaces. Measurements of SEE reported here are conducted in a plasma having a nearly mono-energetic population of electrons that is energetically well resolved and separated from a broader-energy-range electron population. By performing the SEE measurement in an afterglow or afterglow-like plasma, we take advantage of the nearly mono-energetic electron population that arises in ionizing plasma-chemical reactions, such as binary like-particle collisions of metastable atoms. We demonstrate a diagnostic method for measuring the low-energy electron absorption coefficient across the broader energy range and the effects of contamination on the swept-bias probe characteristic trace. A part of this research was performed while VID held a National Research Council Research Associateship Award at AFRL.

  9. Two-photon double ionization of helium in the region of photon energies 42-50 eV

    SciTech Connect

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

    2007-03-15

    We report the total integrated cross section (TICS) of two-photon double ionization of helium in the photon energy range from 42 to 50 eV. Our computational procedure relies on a numerical solution of the time-dependent Schroedinger equation on a square-integrable basis and subsequent projection of this solution on a set of final field-free states describing correlation in the two-electron continuum. Our results suggest that the TICS grows monotonically as a function of photon energy in the region of 42-50 eV, possibly reaching a maximum in the vicinity of 50 eV. We also present fully resolved triple-differential cross sections for selected photon energies.

  10. LETTER TO THE EDITOR: Correlations between ionization cross sections and threshold energies in electron-, positron-, proton- and antiproton-atom collisions

    NASA Astrophysics Data System (ADS)

    Van Reeth, P.; Humberston, J. W.; Laricchia, G.

    2001-04-01

    Strong correlations between the direct single-ionization cross sections and the target ionization energies are found for electron, positron, proton and antiproton impact on the noble gases. These correlations, extending from near threshold to high projectile energies, are similar to those previously observed for positronium formation, namely σ = Aexp (-BEth), where σ is the cross section for each process, Eth is the relevant threshold energy and A and B are functions of the excess energy of the projectile. The generality of this form for the four projectiles is suggestive of a common underlying fundamental aspect of the collisions.

  11. Inner-Shell Ionization of potassium atoms ionized by a femtosecondlaser

    SciTech Connect

    Hertlein, Marcus P.; Adaniya, Hidehito; Amini, Jason; Bressler,Christian; Feinberg, Benedict; Kaiser, Maik; Neumann, Nadine; Prior,Michael H.; Belkacem, Ali

    2006-06-07

    With a femtosecond laser pulse we rapidly ionize potassiumatoms (K0) in the gas phase, generating potassium ions (K+), and monitorthe altered energy-level scheme with a subsequent hard x-ray pulse.Removal of the potassium 4s valence electron increases the bindingenergies of both the valence and the 1s core levels, and induces anultrafast change of the 1s-4p x-ray transition energy by about 2.8 eV. Wesimultaneously observe a 50 percent increase in oscillator strength of K+over K0 for that transition.

  12. A validation of a simple model for the calculation of the ionization energies in X-ray laser-cluster interactions

    SciTech Connect

    White, Jeff; Ackad, Edward

    2015-02-15

    The outer-ionization of an electron from a cluster is an unambiguous quantity, while the inner-ionization threshold is not, resulting in different microscopic quantum-classical hybrid models used in laser-cluster interactions. A simple local ionization threshold model for the change in the ionization energy is proposed and examined, for atoms and ions, at distances in between the initial configuration of the cluster to well into the cluster's disintegration. This model is compared with a full Hartree-Fock energy calculation which accounts for the electron correlation effects using the coupled cluster method with single and double excitations with perturbative triples (CCSD(T)). Good agreement is found between the two lending a strong theoretical support to works which rely on such models for the final and transient properties of the laser-cluster interaction.

  13. Assessment of small volume ionization chambers as reference dosimeters in high-energy photon beams

    NASA Astrophysics Data System (ADS)

    Le Roy, M.; de Carlan, L.; Delaunay, F.; Donois, M.; Fournier, P.; Ostrowsky, A.; Vouillaume, A.; Bordy, J. M.

    2011-09-01

    LNE-LNHB is involved in a European project aiming at establishing absorbed dose-to-water standards for photon-radiation fields down to 2 × 2 cm2. This requires the calibration of reference ionization chambers of small volume. Twenty-four ionization chambers of eight different types with volume ranging from 0.007 to 0.057 cm3 were tested in a 60Co beam. For each chamber, two major characteristics were investigated: (1) the stability of the measured current as a function of the irradiation time under continuous irradiation. At LNE-LNHB, the variation of the current should be less than ±0.1% in comparison with its first value (over a 16 h irradiation time); (2) the variation of the ionization current with the applied polarizing voltage and polarity. Leakage currents were also measured. Results show that (1) every tested PTW (31015, 31016 and 31014) and Exradin A1SL chambers demonstrate a satisfying stability under irradiation. Other types of chambers have a stability complying with the stability criterion for some or none of them. (2) IBA CC01, IBA CC04 and Exradin A1SL show a proper response as a function of applied voltage for both polarities. PTW, Exradin A14SL and Exradin A16 do not. Only three types of chambers were deemed suitable as reference chambers according to LNE-LNHB requirements and specifications from McEwen (2010 Med. Phys. 37 2179-93): Exradin A1SL chambers (3/3), IBA CC04 (2/3) and IBA CC01 (1/3). The Exradin A1SL type with an applied polarizing voltage of 150 V was chosen as an LNE-LNHB reference chamber type in 2 × 2 cm2 radiation fields.

  14. Coulomb three-body effects in low-energy impact ionization of H(1{ital s})

    SciTech Connect

    Roeder, J.; Rasch, J.; Jung, K.; Whelan, C.T.; Ehrhardt, H.; Allan, R.J.; Walters, H.R. |||

    1996-01-01

    The different kinematical and geometrical arrangements that may be used in ({ital e},2{ital e}) studies are briefly reviewed. The ionization of H(1{ital s}) is considered, and within the confines of a relatively simple theoretical model, it is shown how to define experimental setups where one may extract information on the role of Coulomb three-body effects in the incident and final channels. Theoretical and experimental results are presented for coplanar constant geometry where the focus is primarily on incident channel effects. {copyright} {ital 1996 The American Physical Society.}

  15. Ionization, negative ion formation, elastic scattering and spin exchange in H + H collisions at low- to intermediate-energies

    NASA Astrophysics Data System (ADS)

    Ovchinnikov, S. Yu; Kamyshkov, Y.; Zaman, T.; Schultz, D. R.

    2017-04-01

    A new, two-electron transition mechanism is identified that provides the dominant pathway for negative ion formation in 1-20 keV H + H collisions revealed by use of the so-called ‘hidden crossings’ theoretical framework. This transition is made via a branch point between sheets of the complex, quasi-molecular, electronic potential energy surface for singlet states. Good agreement between measurements and the theoretically predicted cross sections is obtained. This mechanism also provides a pathway for ionization in this energy range adding to that previously identified (Bent et al 1998 J. Chem. Phys. 108 1459) involving hidden crossings among the triplet quasi-molecular states, improving the agreement of the resulting theoretical predictions with measurements between 2 and 20 keV. Also improving agreement with measurements is the addition of the effect of Rosenthal oscillations that are superposed upon the ionization and negative ion formation cross sections. We note that in addition to fundamental new insight provided by these calculations, the resulting data support modeling of hydrogen gases and plasmas such as in astrophysical environments and terrestrial laboratory experiments. Further supporting such needs for H + H collision data, we have also created a new and more comprehensive data set that significantly updates previous work (Krstic and Schultz 1999 J. Phys. B: At. Mol. Opt. Phys. 32 3485 and references therein) of elastic scattering and spin exchange integral and differential cross sections.

  16. Direct determination of the ionization energies of PtC, PtO, and PtO2 with VUV radiation.

    PubMed

    Citir, Murat; Metz, Ricardo B; Belau, Leonid; Ahmed, Musahid

    2008-10-02

    Photoionization efficiency curves were measured for gas-phase PtC, PtO, and PtO2 using tunable vacuum ultraviolet (VUV) radiation at the Advanced Light Source. The molecules were prepared by laser ablation of a platinum tube, followed by reaction with CH4 or N2O and supersonic expansion. These measurements provide the first directly measured ionization energy for PtC, IE(PtC) = 9.45 +/- 0.05 eV. The direct measurement also gives greatly improved ionization energies for the platinum oxides, IE(PtO) = 10.0 +/- 0.1 eV and IE(PtO2) = 11.35 +/- 0.05 eV. The ionization energy connects the dissociation energies of the neutral and cation, leading to greatly improved 0 K bond dissociation energies for the neutrals: D0(Pt-C) = 5.95 +/- 0.07 eV, D0(Pt-O) = 4.30 +/- 0.12 eV, and D0(OPt-O) = 4.41 +/- 0.13 eV, as well as enthalpies of formation for the gas-phase molecules DeltaH(0)(f,0)(PtC(g)) = 701 +/- 7 kJ/mol, DeltaH(0)(f,0)(PtO(g)) = 396 +/- 12 kJ/mol, and DeltaH(0)(f,0)(PtO2(g)) = 218 +/- 11 kJ/mol. Much of the error in previous Knudsen cell measurements of platinum oxide bond dissociation energies is due to the use of thermodynamic second law extrapolations. Third law values calculated using statistical mechanical thermodynamic functions are in much better agreement with values obtained from ionization energies and ion energetics. These experiments demonstrate that laser ablation production with direct VUV ionization measurements is a versatile tool to measure ionization energies and bond dissociation energies for catalytically interesting species such as metal oxides and carbides.

  17. Electron-impact ionization of neon at low projectile energy: an internormalized experiment and theory for a complex target.

    PubMed

    Pflüger, Thomas; Zatsarinny, Oleg; Bartschat, Klaus; Senftleben, Arne; Ren, Xueguang; Ullrich, Joachim; Dorn, Alexander

    2013-04-12

    As a fundamental test for state-of-the-art theoretical approaches, we have studied the single ionization (2p) of neon at a projectile energy of 100 eV. The experimental data were acquired using an advanced reaction microscope that benefits from high efficiency and a large solid-angle acceptance of almost 4π. We put special emphasis on the ability to measure internormalized triple-differential cross sections over a large part of the phase space. The data are compared to predictions from a second-order hybrid distorted-wave plus R-matrix model and a fully nonperturbative B-spline R-matrix (BSR) with pseudostates approach. For a target of this complexity and the low-energy regime, unprecedented agreement between experiment and the BSR model is found. This represents a significant step forward in the investigation of complex targets.

  18. Momentum Distribution of Near-Zero-Energy Photoelectrons in the Strong-Field Tunneling Ionization in the Long Wavelength Limit

    PubMed Central

    Xia, Q. Z.; Ye, D. F.; Fu, L. B.; Han, X. Y.; Liu, J.

    2015-01-01

    We investigate the ionization dynamics of Argon atoms irradiated by an ultrashort intense laser of a wavelength up to 3100 nm, addressing the momentum distribution of the photoelectrons with near-zero-energy. We find a surprising accumulation in the momentum distribution corresponding to meV energy and a “V”-like structure at the slightly larger transverse momenta. Semiclassical simulations indicate the crucial role of the Coulomb attraction between the escaping electron and the remaining ion at an extremely large distance. Tracing back classical trajectories, we find the tunneling electrons born in a certain window of the field phase and transverse velocity are responsible for the striking accumulation. Our theoretical results are consistent with recent meV-resolved high-precision measurements. PMID:26081971

  19. Does non-ionizing radiant energy affect determination of the evaporation rate by the gradient method?

    PubMed

    Kjartansson, S; Hammarlund, K; Oberg, P A; Sedin, G

    1991-01-01

    A study was performed to investigate whether measurements of the evaporation rate from the skin of newborn infants by the gradient method are affected by the presence of non-ionizing radiation from phototherapy equipment or a radiant heater. The evaporation rate was measured experimentally with the measuring sensors either exposed to or protected from non-ionizing radiation. Either blue light (phototherapy) or infrared light (radiant heater) was used; in the former case the evaporation rate was measured from a beaker of water covered with a semipermeable membrane, and in the latter case from the hand of an adult subject, aluminium foil or with the measuring probe in the air. No adverse effect on the determinations of the evaporation rate was found in the presence of blue light. Infrared radiation caused an error of 0.8 g/m2h when the radiant heater was set at its highest effect level or when the ambient humidity was high. At low and moderate levels the observed evaporation rate was not affected. It is concluded that when clinical measurements are made from the skin of newborn infants nursed under a radiant heater, the evaporation rate can appropriately be determined by the gradient method.

  20. Electron energy balance and ionization in the channel of a stationary plasma thruster

    SciTech Connect

    Veselovzorov, A. N. Pogorelov, A. A.; Svirskiy, E. B.; Smirnov, V. A.

    2016-03-15

    The paper presents results of numerical simulations of the electron dynamics in the field of the azimuthal and longitudinal waves excited in the channel of a stationary plasma thruster (SPT). The simulations are based on the experimentally determined wave characteristics. The simulation results show that the azimuthal wave displayed as ionization instability enhances electron transport along the thruster channel. It is established that the electron transport rate in the azimuthal wave increases as compared to the rate of diffusion caused by electron scattering from neutral atoms in proportion to the ratio between the times of electron− neutral collisions responsible for ionization and elastic electron scattering, respectively. An expression governing the plasma conductivity is derived with allowance for electron interaction with the azimuthal wave. The Hall parameter, the electron component of the discharge current, and the electron heating power in the thruster channel are calculated for two model SPTs operating with krypton and xenon. The simulation results agree well with the results of experimental studies of these two SPTs.

  1. A generic π* shape resonance observed in energy-dependent photoelectron angular distributions from two-colour, resonant multiphoton ionization of difluorobenzene isomers.

    PubMed

    Staniforth, Michael; Daly, Steven; Reid, Katharine L; Powis, Ivan

    2013-08-14

    We present new evidence for the existence of a near threshold π* shape resonance as a common feature in the photoionization of each isomer of difluorobenzene. Experimentally, this is revealed by significant changes in the anisotropy of the photoelectron angular distributions (PADs) following the ionization of the optically aligned S1 state of these molecules at varying photon energies. Continuum multiple scattering Xα calculations reproduce this behaviour well, and allow the visualisation of the continuum shape resonances. The resonances are unusually narrow in energy (<1 eV), but nevertheless appear to extend right down to the ionization thresholds--exactly the low energy range typically accessed in laser-based resonance enhanced multiphoton ionization (REMPI) schemes. The anticipation of such pronounced energy dependence in the PADs and cross-sections sought for other molecules, and an ability to accurately predict such features, should be important for the reliable application and interpretation of experiments involving REMPI probing of those molecules.

  2. Dependence with air density of the response of the PTW SourceCheck ionization chamber for low energy brachytherapy sources

    SciTech Connect

    Tornero-López, Ana M.; Guirado, Damián; Ruiz-Arrebola, Samuel; Perez-Calatayud, Jose; Simancas, Fernando; Lallena, Antonio M.; Gazdic-Santic, Maja

    2013-12-15

    Purpose: Air-communicating well ionization chambers are commonly used to assess air kerma strength of sources used in brachytherapy. The signal produced is supposed to be proportional to the air density within the chamber and, therefore, a density-independent air kerma strength is obtained when the measurement is corrected to standard atmospheric conditions using the usual temperature and pressure correction factor. Nevertheless, when assessing low energy sources, the ionization chambers may not fulfill that condition and a residual density dependence still remains after correction. In this work, the authors examined the behavior of the PTW 34051 SourceCheck ionization chamber when measuring the air kerma strength of {sup 125}I seeds.Methods: Four different SourceCheck chambers were analyzed. With each one of them, two series of measurements of the air kerma strength for {sup 125}I selectSeed{sup TM} brachytherapy sources were performed inside a pressure chamber and varying the pressure in a range from 747 to 1040 hPa (560 to 780 mm Hg). The temperature and relative humidity were kept basically constant. An analogous experiment was performed by taking measurements at different altitudes above sea level.Results: Contrary to other well-known ionization chambers, like the HDR1000 PLUS, in which the temperature-pressure correction factor overcorrects the measurements, in the SourceCheck ionization chamber they are undercorrected. At a typical atmospheric situation of 933 hPa (700 mm Hg) and 20 °C, this undercorrection turns out to be 1.5%. Corrected measurements show a residual linear dependence on the density and, as a consequence, an additional density dependent correction must be applied. The slope of this residual linear density dependence is different for each SourceCheck chamber investigated. The results obtained by taking measurements at different altitudes are compatible with those obtained with the pressure chamber.Conclusions: Variations of the altitude and

  3. The effect of conformation on the ionization energetics of n-butylbenzene. I. A threshold ionization study

    NASA Astrophysics Data System (ADS)

    Tong, Xin; Ford, Mark S.; Dessent, Caroline E. H.; Müller-Dethlefs, Klaus

    2003-12-01

    Conformational isomers of the aromatic hydrocarbon n-butylbenzene have been studied using two-color REMPI (resonance enhanced multiphoton ionization) and MATI (mass analyzed threshold ionization) spectroscopy to explore the effect of conformation on ionization dynamics. Gauche- and anti-cationic conformers were selectively produced by two-color excitation via the respective S1 origins. Adiabatic ionization potentials of the gauche- and anti-conformations were determined to be 70 148 and 69 955±5 cm-1, respectively. Analysis of the REMPI and MATI spectra allowed the determination of the S0 (38 cm-1), S1 (100 cm-1), and D0 (-155 cm-1) gauche- and anti-conformer energy differences. Spectral features and vibrational modes are interpreted with the aid of MP2/cc-pVDZ ab initio calculations, and ionization-induced changes in the molecular conformations discussed.

  4. PFI-ZEKE (Pulsed Field Ionization-Zero Electron Kinetic Energy) para el estudio de iones

    NASA Astrophysics Data System (ADS)

    Castaño, F.; Fernández, J. A.; Basterretxea, A. Longarte. F.; Sánchez Rayo, M. N.; Martínez, R.

    Entre las áreas hacia donde ha evolucionado la Química en los últimos años están los estudios de sistemas con especies reactivas de alta energía y los dominados por fuerzas intermoleculares débiles, con energías de unas pocas kcal/mol. En efecto, el estudio de las propiedades de los iones, comenzando por su relación con la molécula neutra de la que procede, la energía de ionización, los estados vibracionales y rotacionales, energías de enlace de Van der Waals entre el ión y una amplia variedad de otras moléculas, sus confórmeros o isómeros y sus reacciones o semi-reacciones químicas están en la raíz de la necesidad de la espectroscopía conocida como PFI-ZEKE, Pulsed Field Ionization-Zero Electron Kinetic Energy. Entre las aplicaciones que requieren estos conocimientos se encuentran la generación de plasmas para la fabricación de semiconductores, memorias magnéticas, etc, así como los sistemas astrofísicos, la ionosfera terrestre, etc. La espectroscopía ZEKE es una evolución de las de fluorescencia inducida por láser, LIF, ionización multifotónica acrecentada por resonancia, REMPI, con uno y dos colores y acoplada a un sistema de tiempo de vuelo, REMPI-TOF-MS, y las espectroscopías de doble resonancia IR-UV y UV-UV. Sus espectros y la ayuda de cálculos ab inicio permite determinar las energías de enlace de complejos de van der Waals en estados fundamental y excitados, identificar confórmeros e isómeros, obtener energías de ionización experimentales aproximadas (100 cm-1) y otras variables de interés. Al igual que con LIF, REMPI y dobles resonancias, es posible utilizar muestras gaseosas, pero los espectros están muy saturados de bandas y su interpretación es difícil o imposible. Se evitan estas dificultades estudiando las moléculas o complejos en expansiones supersónicas, donde la T de los grados de libertad solo alcanzan unos pocos K. Para realizar experimentos de ZEKE hay que utilizar una propiedad recientemente

  5. Dose measurement using Al2O3 dosimeter in comparison to LiF:Mg,Ti dosimeter and ionization chamber at low and high energy x-ray

    NASA Astrophysics Data System (ADS)

    Yusof, Mohd Fahmi Mohd; Yahya, Muhammad Hadzmi; Rosnan, Muhammad Syazwan; Abdullah, Reduan; Kadir, Ahmad Bazlie Abdul

    2017-01-01

    The dose measurement using Al2O3 OSL dosimeter (OSLD) was carried out at low and high energy x-ray. The dose at low energy x-ray was measured at 40, 71 and 125 kVp x-ray energies. The dose ar high energy x-ray was measured at 6 and 10 MV x-ray energies measured at the depth of maximum dose (Zmax). The results were compared to that in ionization chamber and LiF: Mg,Ti thermoluminescent dosimeters (TLD100). The results showed that the dose of OSLD were less in agreement to ionization chamber compared to that in TLD100. The dose of OSLD however was in good agreement to that in ionization chamber at high energy x-ray. The dose measured using OSLD were found to be more consistence at high energy x-ray shown by the standard deviation of the readings. The measurement of x2 showed that the readings of OSLD were close to that in ionization chamber with values of 2.21 and 4.63 for 6 and 10 MV respectively. The results indicated that OSLD is more suitable for dose measurement at high energy x-ray.

  6. High-energy and low-energy collision-induced dissociation of protonated flavonoids generated by MALDI and by electrospray ionization

    NASA Astrophysics Data System (ADS)

    March, Raymond E.; Li, Hongxia; Belgacem, Omar; Papanastasiou, Dimitris

    2007-04-01

    Product ion mass spectra of a series of nine protonated flavonoids have been observed by electrospray ionization combined with quadrupole/time-of-flight (ESI QTOF), and matrix-assisted laser desorption ionization combined either with quadrupole ion trap (MALDI QIT) tandem mass spectrometry or time-of-flight tandem mass spectrometry (MALDI TOF ReTOF). The compounds examined are 3,6-, 3,2'-, and 3,3'-dihydoxyflavone, apigenin (5,7,4'-trihydroxyflavone), luteolin (5,7,3',4'-tetrahydroxyflavone), apigenin-7-O-glucoside, hesperidin (5,7,3'-trihydroxy-4'-methoxyflavanone), daidzen (7,4'-dihydroxyisoflavone), and rutin (quercitin-3-O-rutinoside) where quercitin is 3,5,7,3',4'-pentahydroxyflavone; sodiated rutin was examined also. The center-of-mass energies in ESI QTOF and MALDI QIT are similar (1-4 eV) and their product ion mass spectra are virtually identical. In the MALDI TOF ReTOF instrument, center-of-mass energies range from 126-309 eV for sodiated rutin to protonated dihydroxyflavones, respectively. Due to the high center-of-mass energies available with the MALDI TOF ReTOF instrument, some useful structural information may be obtained; however, with increasing precursor mass/charge ratio, product ion mass spectra become simplified so as to be of limited structural value. Electronic excitation of the protonated (and sodiated) species examined here offers an explanation for the very simple product ion mass spectra observed particularly for glycosylated flavonoids.

  7. Recombination processes in a flowing magnetized plasma: Application to ionization energy recovery in the variable specific impulse magnetoplasma rocket (VASIMR)

    NASA Astrophysics Data System (ADS)

    Chavers, Donald Gregory

    Electric propulsion involves the acceleration of charged particles (ions and electrons) through electric and magnetic body forces. The collection of these charged particles, or plasma, cannot be stored but must be created in-situ. Therefore, energy must be supplied to a neutral gas to create the plasma that is accelerated by the body forces. The energy that is used to create the plasma, i.e., ionization energy, is typically lost, "frozen" in the exhaust of the thruster. When the kinetic energy in the plasma flow is much larger than the energy used to create the plasma, this frozen-flow loss is negligible. Conversely, if the frozen-flow loss is a major fraction of the total plasma energy, its recovery, even in a partial way, may improve the energy efficiency of the thruster while also providing a potential means for thrust augmentation. This dissertation investigates the underlying physics, which could enable the practical recovery of frozen-flow losses by processes such as surface and volume recombination. For surface recombination, the ions approach the surface of the metal and are neutralized by electrons from the metal via the Auger neutralization process. For volume recombination, the ions and electrons recombine, with energy released via line radiation or by transferring energy to a third body such as another electron. Since the total energy of the neutralized ion, an atom, is less than the total energy of the ion and electron pair before recombination, conservation of energy requires the release of energy as the ion and electron recombine. The measurements described in this dissertation were performed on the VX-10 experiment, a plasma device supporting the development of the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) concept and located at the Advanced Space Propulsion Laboratory of the Johnson Space Center. Results suggest that the recombination energy can be recovered. The available energy and power recovered depends on the local plasma

  8. The effect of air cavity size in cylindrical ionization chambers on the measurements in high-energy radiotherapy photon beams—an experimental study

    NASA Astrophysics Data System (ADS)

    Swanpalmer, John; Johansson, Karl-Axel

    2012-07-01

    The present investigation is a continuation of a previous study on the effect of the diameter of the air cavity in cylindrical ionization chambers on perturbation correction factors. Measurements were made using high-energy radiotherapy photon beams (4, 6 and 15 MV) in a water phantom. Two different pairs of cylindrical ionization chambers were used. The chambers in each pair had identical materials and construction but different air cavity diameters. The same methods were employed as in our previous investigation. The diameter of the air cavity in cylindrical ionization chambers influences the mass ionization (the measured ionization expressed per unit mass of air in the chamber air cavity) at the depth where the maximum ionization is observed and a normalization at this depth is therefore not correct. The corrections obtained at depths of 50 and 100 mm in the phantom showed that the air cavity diameter in cylindrical ionization chambers has a greater effect on the perturbation effects than the photon beam quality. The corrections found at depths of 50 and 100 mm are smaller than those currently used in dosimetry protocols.

  9. Experimental and theoretical triple differential cross sections for electron-impact ionization of Ar (3p) for equal energy final state electrons

    NASA Astrophysics Data System (ADS)

    Amami, Sadek; Ozer, Zehra N.; Dogan, Mevlut; Yavuz, Murat; Varol, Onur; Madison, Don

    2016-09-01

    There have been several studies of electron-impact ionization of inert gases for asymmetric final state energy sharing and normally one electron has an energy significantly higher than the other. However, there have been relatively few studies examining equal energy final state electrons. Here we report experimental and theoretical triple differential cross sections for electron impact ionization of Ar (3p) for equal energy sharing of the outgoing electrons. Previous experimental results combined with some new measurements are compared with distorted wave born approximation (DWBA) results, DWBA results using the Ward-Macek (WM) approximation for the post collision interaction (PCI), and three-body distorted wave (3DW) which includes PCI without approximation. The results show that it is crucially important to include PCI in the calculation particularly for lower energies and that the WM approximation is valid only for high energies. The 3DW, on the other hand, is in reasonably good agreement with data down to fairly low energies.

  10. Slalom in complex time: Emergence of low-energy structures in tunnel ionization via complex-time contours

    NASA Astrophysics Data System (ADS)

    Pisanty, Emilio; Ivanov, Misha

    2016-04-01

    The ionization of atoms by strong, low-frequency fields can generally be described well by assuming that the photoelectron is, after the ionization step, completely at the mercy of the laser field. However, certain phenomena, like the recent discovery of low-energy structures (LESs) in the long-wavelength regime, require the inclusion of the Coulomb interaction with the ion once the electron is in the continuum. We explore the first-principles inclusion of this interaction, known as analytical R -matrix theory, and its consequences on the corresponding quantum orbits. We show that the trajectory must have an imaginary component, and that this causes branch cuts in the complex time plane when the real trajectory revisits the neighborhood of the ionic core. We provide a framework for consistently navigating these branch cuts based on closest-approach times, which satisfy the equation r (t ).v (t )=0 in the complex plane. We explore the geometry of these roots and describe the geometrical structures underlying the emergence of LESs in both the classical and quantum domains.

  11. Computational Calculation Of The Ionization Energies Of The Human Prion Protein By The Coarse-grain Method

    NASA Astrophysics Data System (ADS)

    Lyu, Justin; Andrianarijaona, V. M.

    2016-05-01

    The causes of the misfolding of prion protein -i.e. the transformation of PrPC to PrPSc - have not been clearly elucidated. Many studies have focused on identifying possible chemical conditions, such as pH, temperature and chemical denaturation, that may trigger the pathological transformation of prion proteins (Weiwei Tao, Gwonchan Yoon, Penghui Cao, `` β-sheet-like formation during the mechanical unfolding of prion protein'', The Journal of Chemical Physics, 2015, 143, 125101). Here, we attempt to calculate the ionization energies of the prion protein, which will be able to shed light onto the possible causes of the misfolding. We plan on using the coarse-grain method which allows for a more feasible calculation time by means of approximation. We believe that by being able to approximate the ionization potential, particularly that of the regions known to form stable β-strands of the PrPSc form, the possible sources of denaturation, be it chemical or mechanical, may be narrowed down.

  12. A VUV photoionization measurement and ab-initio calculation of the ionization energy of gas phase SiO2

    SciTech Connect

    Kostko, Oleg; Ahmed, Musahid; Metz, Ricardo B.

    2008-12-05

    In this work we report on the detection and vacuum-ultraviolet (VUV) photoionization of gas phase SiO2 generated in situ via laser ablation of silicon in a CO2 molecular beam. The resulting species are investigated by single photon ionization with tunable VUV synchrotron radiation and mass analyzed using reflectron mass spectrometry. Photoionization efficiency (PIE) curves are recorded for SiO and SiO2 and ionization energy estimates are revealed from such measurements. A state-to-state ionizationenergy of 12.60 (+-0.05) eV is recorded by fitting two prominent peaks in the PIE curve for the following process: 1SUM O-Si-O --> 2PRODg [O-Si-O]+. Electronic structure calculations aid in the interpretation of the photoionization process and allow for identification of the symmetric stretch of 2PRODg [O-Si-O]+ which is observed in the PIE spectrum to be 0.11 eV (890 cm-1) above the ground state of the cation and agrees with the 892 cm-1 symmetric stretch frequency calculated at the CCSD(T)/aug-cc-pVTZ level.

  13. Multiphoton inner-shell ionization of the carbon atom

    NASA Astrophysics Data System (ADS)

    Rey, H. F.; van der Hart, H. W.

    2015-07-01

    We apply time-dependent R -matrix theory to study inner-shell ionization of C atoms in ultrashort high-frequency light fields with a photon energy between 170 and 245 eV. At an intensity of 1017 W /cm2, ionization is dominated by single-photon emission of a 2 ℓ electron, with two-photon emission of a 1 s electron accounting for about 2-3% of all emission processes, and two-photon emission of 2 ℓ contributing about 0.5-1%. Three-photon emission of a 1 s electron is estimated to contribute about 0.01-0.03%. Around a photon energy of 225 eV, two-photon emission of a 1 s electron, leaving C+ in either 1 s 2 s 2 p3 or 1 s 2 p4 , is resonantly enhanced by intermediate 1 s 2 s22 p3 states. The results demonstrate the capability of time-dependent R -matrix theory to describe inner-shell ionization processes including rearrangement of the outer electrons.

  14. Ionization By Impact Electrons in Solids: Electron Mean Free Path Fitted Over A Wide Energy Range

    SciTech Connect

    Ziaja, B; London, R A; Hajdu, J

    2005-06-09

    We propose a simple formula for fitting the electron mean free paths in solids both at high and at low electron energies. The free-electron-gas approximation used for predicting electron mean free paths is no longer valid at low energies (E < 50 eV), as the band structure effects become significant at those energies. Therefore we include the results of the band structure calculations in our fit. Finally, we apply the fit to 9 elements and 2 compounds.

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

    NASA Astrophysics Data System (ADS)

    McLaughlin, Brendan M.

    2017-01-01

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

  16. Evaluation of highly ionizing components in high-energy nucleon radiation fields

    NASA Technical Reports Server (NTRS)

    Wilson, John W.; Townsend, Lawrence W.; Khan, Ferdous

    1989-01-01

    The data and models for nuclear fragment recoil distribution produced by high-energy nuclear events in tissue are reviewed. Results for linear energy transfer distributions in soft tissue are derived, and a simple model is developed for use in radiation studies and risk estimates.

  17. Evaluation of highly ionizing components in high-energy nucleon radiation fields

    NASA Technical Reports Server (NTRS)

    Wilson, John W.; Townsend, Lawrence W.; Khan, Ferdous

    1989-01-01

    The data and models for nuclear fragment recoil distribution produced by high-energy nuclear events in tissue are reviewed. Results for linear energy transfer distributions in soft tissue are derived, and a simple model is developed for use in radiation studies and risk estimates.

  18. A State-Specific PCM-DFT method to include dynamic solvent effects in the calculation of ionization energies: Application to DNA bases

    NASA Astrophysics Data System (ADS)

    Muñoz-Losa, Aurora; Markovitsi, Dimitra; Improta, Roberto

    2015-08-01

    A State-Specific PCM-DFT method taking into account dynamical solvent effects in the calculation of ionization energies (IEs) is reported. Mono-methylated nucleobases, representative of DNA blocks, are used as a test case. The accuracy of several functionals is tested, the M05-2X functional providing the most consistent performance. The inclusion of some molecules of the first hydration shell does not significantly affect the computed IE. The obtained vertical and adiabatic IEs are in good agreement with the available experimental and computational results, supporting the reliability of our method, enabling the calculation of first and upper ionization energies by using a single approach.

  19. Monte Carlo aided design of an improved well-type ionization chamber for low energy brachytherapy sources

    SciTech Connect

    Bohm, Tim D.; Micka, John A.; De Werd, Larry A.

    2007-04-15

    The determination of the air kerma strength of a brachytherapy seed is necessary for effective treatment planning. Well-type ionization chambers are used on site at therapy clinics to determine the air kerma strength of seeds. In this work, an improved well-type ionization chamber for low energy, low dose rate brachytherapy sources is designed using Monte Carlo transport calculations to aid in the design process. The design improvements are the elimination of the air density induced over-response effect seen in other air-communicating chambers for low energy photon sources, and a larger signal strength (response or current) for {sup 103}Pd and {sup 125}I based seeds. A prototype well chamber based on the Monte Carlo aided design but using graphite coated acrylic walls rather than the design basis air equivalent plastic (C-552) walls was constructed and experimentally evaluated. The prototype chamber produced an 85% stronger signal when measuring a commonly used {sup 103}Pd seed and a 26% stronger signal when measuring a commonly used {sup 125}I seed when compared to another commonly used well chamber. The normalized P{sub TP} corrected chamber response is, at most, 1.3% and 2.4% over unity for air densities/pressures corresponding to an elevation of 3048 m (10 000 feet) above sea level for the commonly used {sup 103}Pd and {sup 125}I based seeds respectively. Comparing calculated and measured chamber responses for common {sup 103}Pd and {sup 125}I based brachytherapy seeds show agreement within 0.6% and 0.2%, respectively. We conclude that Monte Carlo transport calculations accurately model the response of this new well chamber and in general can be used to predict the response of well chambers. The prototype chamber built in this work responds as predicted by the Monte Carlo calculations.

  20. The efficiency of ionizing photon production and the radiation energy balance in compact star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Izotov, Y. I.; Guseva, N. G.; Fricke, K. J.; Henkel, C.; Schaerer, D.

    2017-06-01

    We derive apparent and absolute ultraviolet (UV) magnitudes, and luminosities in the infrared (IR) range of a large sample of low-redshift (0 < z < 1) compact star-forming galaxies (CSFGs) selected from the Data Release 12 of the Sloan Digital Sky Survey. These data are used to constrain the extinction law in the UV for our galaxies and to compare the absorbed radiation in the UV range with the emission in the IR range. We find that the modelled far- and near-UV apparent magnitudes are in good agreement with the observed Galaxy Evolution Explorer magnitudes. It is found that galaxies with low and high equivalent widths EW(Hβ) of the Hβ emission line require different reddening laws with steeper slopes for galaxies with higher EW(Hβ). This implies that an important role of the hard ionizing radiation in shaping the dust grain size distribution. The IR emission in the range of 8-1000 μm is determined by using existing data obtained by various IR space telescopes. We find that the radiation energy absorbed in the UV range is nearly equal to the energy emitted in the IR range leaving very little room for hidden star formation in our galaxies. Using extinction-corrected Hβ luminosities and modelled SEDs in the UV range, we derive efficiencies of ionizing photon production ξ for the entire sample of CSFGs. It is found that ξ in CSFGs with high EW(Hβ) are among the highest known for low- and high-redshift galaxies. If galaxies with similar properties existed at redshifts z = 5-10, they could be considered as promising candidates for the reionization of the Universe.

  1. State selective Rydberg charge transfer and ionization in low energy ion-atom collisions

    NASA Astrophysics Data System (ADS)

    Perumal, A. N.; Tripathi, D. N.

    1998-10-01

    The Classical Trajectory Monte Carlo (CTMC) simulation method with a core modified interaction potential has been used to study the single charge transfer in Na +and Ar + ions colliding with a variety of state selected Na Rydberg atom targets ( n=24, 28, 33, 40 and l=2) in the reduced velocity region v=0.2-2.0. The experimentally observed structures in the total capture cross section versus reduced velocity curves are reproduced by CTMC method. The n-distribution of final capture state has got two peaks viz. first one at nf= ni and the second one at a higher nf depending on the initial angular momentum in the velocity regime 0.4-0.6. These structures have been explained in terms of quasimolecular-ion formation and a classical model proposed by Roy et al. (B.N. Roy, D.N. Tripathi, D.K. Rai, Phys. Rev. A 5 (1972) 1252). The CTMC ionization cross section results are benchmarked with the recent experimental measurement of Makarov et al. (O.P. Makarov, D.M. Homan, O.P. Sorokina, K.B. MacAdam, in: F. Aumayr, G. Betz, H.P. Winter (Eds.), Proceedings of the 20th International Conference on the Physics of Electronics and Atomic Collisions, Vienna, 1997, p. FR052) for Na +-Na(24 d).

  2. Asymmetric electron energy sharing in electron-impact double ionization of helium

    NASA Astrophysics Data System (ADS)

    Silenou Mengoue, M.; Tetchou Nganso, H. M.

    2016-12-01

    We present the fully fivefold differential cross sections (FDCSs) for (e ,3 e ) processes in helium within the first Born approximation. The calculation is performed for a coplanar geometry in which the incident electron is fast (˜6 keV), the momentum transfer is small (0.24 a.u.), and for an asymmetric energy sharing between both slow ejected electrons at excess energy of 20 eV. Two cases have been considered: E1=15 eV, E2=5 eV and E1=8 eV, E2=12 eV. While waiting for new theoretical and experimental results for confrontations, in particular for asymmetric energy sharing, our results clearly demonstrate that, for the same incident energy, the same momentum transfer and the same excess energy, the (e ,3 e ) process in helium with asymmetric energy sharing between ejected electrons is more likely than the case with symmetric energy sharing. The two- and three-dimensional representation of the FDCSs covering all possible values of the angle of ejections are presented and discussed. The theoretical cross sections are calculated by using a compact-kernel-integral-equation approach associated with the Jacobi matrix method to calculate a three-body wave function and which leads to a full convergence in terms of the basis size.

  3. Internal energy distribution of peptides in electrospray ionization : ESI and collision-induced dissociation spectra calculation.

    PubMed

    Pak, Alireza; Lesage, Denis; Gimbert, Yves; Vékey, Károly; Tabet, Jean-Claude

    2008-04-01

    The internal energy of ions and the timescale play fundamental roles in mass spectrometry. The main objective of this study is to estimate and compare the internal energy distributions of different ions (different nature, degree of freedom 'DOF' and fragmentations) produced in an electrospray source (ESI) of a triple-quadrupole instrument (Quattro I Micromass). These measurements were performed using both the Survival Yield method (as proposed by De Pauw) and the MassKinetics software (kinetic model introduced by Vékey). The internal energy calibration is the preliminary step for ESI and collision-induced dissociation (CID) spectra calculation. meta-Methyl-benzylpyridinium ion and four protonated peptides (YGGFL, LDIFSDF, LDIFSDFR and RLDIFSDF) were produced using an electrospray source. These ions were used as thermometer probe compounds. Cone voltages (V(c)) were linearly correlated with the mean internal energy values () carried by desolvated ions. These mean internal energy values seem to be slightly dependent on the size of the studied ion. ESI mass spectra and CID spectra were then simulated using the MassKinetics software to propose an empirical equation for the mean internal energy () versus cone voltage (V(c)) for different source temperatures (T): < E(int) > = [405 x 10(-6) - 480 x 10(-9) (DOF)] V(c)T + E(therm)(T). In this equation, the E(therm)(T) parameter is the mean internal energy due to the source temperature at 0 V(c).

  4. Detection of High Energy Cosmic Ray with the Advanced Thin Ionization Calorimeter (ATIC)

    NASA Technical Reports Server (NTRS)

    Fazely, Ali R.

    2003-01-01

    ATIC is a balloon-borne investigation of cosmic ray spectra, from below 50 GeV to near 100 TeV total energy, using a fully active Bismuth Gemmate (BGO) calorimeter. It is equipped with the first large area mosaic of small fully depleted silicon detector pixels capable of charge identification in cosmic rays from H to Fe. As a redundancy check for the charge identification and a coarse particle tracking system, three projective layers of x-y scintillator hodoscopes were employed, above, in the center and below a Carbon interaction 'target'. Very high energy gamma-rays and their energy spectrum may provide insight to the flux of extremely high energy neutrinos which will be investigated in detail with several proposed cubic kilometer scale neutrino observatories in the next decade.

  5. Holes bound as small polarons to acceptor defects in oxide materials: why are their thermal ionization energies so high?

    NASA Astrophysics Data System (ADS)

    Schirmer, O. F.

    2011-08-01

    Holes bound to acceptor defects in oxide materials usually need comparatively high energies, of the order of 0.5-1.0 eV, to be ionized thermally to the valence band maximum. It is discussed that this has to be attributed to the stabilization of such holes by mainly short range interactions with the surrounding lattice, leading to the formation of small O - polarons. This is tantamount to the localization of the hole at only one of several equivalent oxygen ions next to the defect. The hole stabilizing energies can be determined experimentally from the related intense optical absorption bands. This paper exploits previous phenomenological studies of bound-hole small polarons in order to account for the large hole stabilization energies on this basis. A compilation demonstrates that bound-hole small polarons occur rather often in oxides and also in some related materials. The identification of such systems is based on EPR and optical studies and also on recent advanced electronic structure calculations.

  6. Quantum and classical dynamics of H + CaCl(X (2)Σ(+)) → HCl + Ca((1)S) reaction and vibrational energy levels of the HCaCl complex.

    PubMed

    Tan, Rui Shan; Zhai, Huan Chen; Gao, Feng; Tong, Dianmin; Lin, Shi Ying

    2016-06-21

    We carried out accurate quantum wave packet as well as quasi-classical trajectory (QCT) calculations for H + CaCl (νi = 0, ji = 0) reaction occurring on an adiabatic ground state using the recent ab initio potential energy surface to obtain the quantum and QCT reaction probabilities for several partial waves (J = 0, 10, and 20) as well as state resolved QCT integral and differential cross sections. The complete list of vibrational energy levels supported by the intermediate HCaCl complex is also obtained using the Lanczos algorithm. The QCT reaction probabilities show excellent agreement with the quantum ones except for the failure in reproducing the highly oscillatory resonance structure. Despite the fact that the reaction is exothermic and the existence of a barrier that is energetically lower than the bottom of the reactant valley, the reaction probability for J = 0 shows threshold-like behavior and the reactivity all through the energies is very low (<0.1). The dynamical features at two different energy regions (<0.35 eV and >0.35 eV) are found to be different drastically from each other. The analyses of these results suggest that the reaction is governed by one of the two different types of reaction mechanism, one is the direct mechanism at the high energy region and the other is the indirect mechanism at the low energy region by which the reaction proceeds through the long-lived intermediate complex followed by a statistical dissociation into asymptotic channels.

  7. Above-threshold ionization of Mg by linearly and circularly polarized laser fields: Origin of the subpeaks in the photoelectron energy spectra

    SciTech Connect

    Nakajima, Takashi; Buica, Gabriela

    2006-08-15

    We theoretically investigate above-threshold ionization of Mg by linearly and circularly polarized fs laser pulses. We find that the above-threshold ionization peaks are accompanied by small subpeaks for both linearly and circularly polarized pulses. We interpret the physical origin of the subpeaks as above-threshold ionization from the low-lying bound states which are far off-resonantly excited by the spectral wing of the pulse. This interpretation is confirmed by our comparative numerical studies. Furthermore, we provide a clear explanation of why this kind of subpeak in the photoelectron energy spectra has not been reported for smaller photon energies with Mg and other commonly used atoms such as H and rare gas atoms.

  8. Site-specific recoil-induced effects on inner-shell photoionization of linear triatomic molecules: N 1 s photoelectron spectra of N2 O

    NASA Astrophysics Data System (ADS)

    Krivosenko, Yu. S.; Pavlychev, A. A.

    2016-11-01

    We investigate hard X-ray ionization of linear triatomic molecules accenting recoil-induced effects on the dynamics of molecular frame. This dynamics is studied within the two-springs and harmonic approximations. The mode-channel relationship connecting the excitations of vibrational, rotational and translational degrees of freedom with the Σ → Σ and Σ → Π photoionization channels is applied to compute the N 1s-1 photoelectron spectra of molecular N2 O for various photon energies. The distinct ionized-site- and molecular-orientation-specific changes in the vibration structure of the 1 s photoelectron lines of terminal and central nitrogen atoms are revealed and discussed.

  9. An (e, 2e + ion) study of low-energy electron-impact ionization and fragmentation of tetrahydrofuran with high mass and energy resolutions

    SciTech Connect

    Ren, Xueguang Pflüger, Thomas; Weyland, Marvin; Baek, Woon Yoon; Rabus, Hans; Ullrich, Joachim; Dorn, Alexander

    2014-10-07

    We study the low-energy (E{sub 0} = 26 eV) electron-impact induced ionization and fragmentation of tetrahydrofuran using a reaction microscope. All three final-state charged particles, i.e., two outgoing electrons and one fragment ion, are detected in triple coincidence such that the momentum vectors and, consequently, the kinetic energies for charged reaction products are determined. The ionic fragments are clearly identified in the experiment with a mass resolution of 1 amu. The fragmentation pathways of tetrahydrofuran are investigated by measuring the ion kinetic energy spectra and the binding energy spectra where an energy resolution of 1.5 eV has been achieved using the recently developed photoemission electron source. Here, we will discuss the fragmentation reactions for the cations C{sub 4}H{sub 8}O{sup +}, C{sub 4}H{sub 7}O{sup +}, C{sub 2}H{sub 3}O{sup +}, C{sub 3}H{sub 6}{sup +}, C{sub 3}H{sub 5}{sup +}, C{sub 3}H{sub 3}{sup +}, CH{sub 3}O{sup +}, CHO{sup +}, and C{sub 2}H{sub 3}{sup +}.

  10. An (e, 2e + ion) study of low-energy electron-impact ionization and fragmentation of tetrahydrofuran with high mass and energy resolutions.

    PubMed

    Ren, Xueguang; Pflüger, Thomas; Weyland, Marvin; Baek, Woon Yoon; Rabus, Hans; Ullrich, Joachim; Dorn, Alexander

    2014-10-07

    We study the low-energy (E0 = 26 eV) electron-impact induced ionization and fragmentation of tetrahydrofuran using a reaction microscope. All three final-state charged particles, i.e., two outgoing electrons and one fragment ion, are detected in triple coincidence such that the momentum vectors and, consequently, the kinetic energies for charged reaction products are determined. The ionic fragments are clearly identified in the experiment with a mass resolution of 1 amu. The fragmentation pathways of tetrahydrofuran are investigated by measuring the ion kinetic energy spectra and the binding energy spectra where an energy resolution of 1.5 eV has been achieved using the recently developed photoemission electron source. Here, we will discuss the fragmentation reactions for the cations C4H8O(+), C4H7O(+), C2H3O(+), C3H6(+), C3H5(+), C3H3(+), CH3O(+), CHO(+), and C2H3(+).

  11. Observation of atomic oxygen O(1S) green-line emission in the summer polar upper mesosphere associated with high-energy (≥30 keV) electron precipitation during high-speed solar wind streams

    NASA Astrophysics Data System (ADS)

    Lee, Young-Sook; Kwak, Young-Sil; Kim, Kyung-Chan; Solheim, Brian; Lee, Regina; Lee, Jaejin

    2017-01-01

    The auroral green-line emission at 557.7 nm wavelength as arising from the atomic oxygen O(1S → 1D) transition typically peaks at an altitude of 100 km specifically in the nightside oval, induced by auroral electrons within an energy range of 100 eV-30 keV. Intense aurora is known as being suppressed by sunlight in summer daytime but usually occurs in low electrical background conductivity. However, in the present study in summer (July) sunlit condition, enhancements of O(1S) emission rates observed by using the Wind Imaging Interferometer/UARS were frequently observed at low altitudes below 90 km, where ice particles are created initially as subvisible and detected as polar mesosphere summer echoes, emerging to be an optical phenomenon of polar mesospheric clouds. The intense O(1S) emission occurring in summer exceeds those occurring in the daytime in other seasons both in occurrence and in intensity, frequently accompanied by occurrences of supersonic neutral velocity (300-1500 m s-1). In the mesosphere, ion motion is controlled by electric field and the momentum is transferred to neutrals. The intense O(1S) emission is well associated with high-energy electron precipitation as observed during an event of high-speed solar wind streams. Meanwhile, since the minimum occurrences of O(1S) emission and supersonic velocity are maintained even in the low precipitation flux, the mechanism responsible is not only related to high-energy electron precipitation but also presumably to the local conditions, including the composition of meteoric-charged ice particles and charge separation expected in extremely low temperatures (<150 K).

  12. Direct effects of ionizing radiation on integral membrane proteins. Noncovalent energy transfer requires specific interpeptide interactions

    SciTech Connect

    Jhun, E.; Jhun, B.H.; Jones, L.R.; Jung, C.Y. )

    1991-05-25

    The 12 transmembrane alpha helices (TMHs) of human erythrocyte glucose transporter were individually cut by pepsin digestion as membrane-bound 2.5-3.5-kDa peptide fragments. Radiation-induced chemical degradation of these fragments showed an average target size of 34 kDa. This is 10-12 x larger than the average size of an individual TMH, demonstrating that a significant energy transfer occurs among these TMHs in the absence of covalent linkage. Heating this TMH preparation at 100{degree}C for 15 min reduced the target size to 5 kDa or less, suggesting that the noncovalent energy transfer requires specific helix-helix interactions. Purified phospholamban, a small (6-kDa) integral membrane protein containing a single TMH, formed a pentameric assembly in sodium dodecyl sulfate. The chemical degradation target size of this phospholamban pentamer was 5-6 kDa, illustrating that not all integral membrane protein assemblies permit intersubunit energy transfer. These findings together with other published observations suggest strongly that significant noncovalent energy transfer can occur within the tertiary and quaternary structure of membrane proteins and that as yet undefined proper molecular interactions are required for such covalent energy transfer. Our results with pepsin-digested glucose transporter also illustrate the importance of the interhelical interaction as a predominating force in maintaining the tertiary structure of a transmembrane protein.

  13. K -shell ionization cross sections of Al, Si, S, Ca, and Zn for oxygen ions in the energy range 1. 1--8 MeV

    SciTech Connect

    Geretschlaeger, M. ); Smit, Z. ); Steinbauer, E. )

    1992-03-01

    {ital K}-shell ionization cross sections induced by 1.1--8-MeV oxygen ions in Al, Si, S, Ca, and Zn were measured using different target thicknesses. The cross sections for vanishingly thin and for charge-equilibrium targets were obtained by extrapolation. The experimental results are compared to the perturbed stationary-state approximation with energy-loss, Coulomb, and relativistic corrections (ECPSSR) cross sections (Brandt and Lapicki, Phys. Rev. A 23, 1717 (1981)), to the modification of the ECPSSR theory (MECPSSR) (Benka, Geretschlaeger, and Paul, J. Phys. (Paris) Colloq. Suppl. 12, C9-251 (1987)), to the theory for direct Coulomb ionization of the 1{ital s}{sigma} molecular orbital (Montenegro and Sigaud, J. Phys. B 18, 299 (1985)), and to several semiclassical approximation codes using either the united atom binding procedure or the variational approach of Andersen {ital et} {ital al}. (Nucl. Instrum. Methods 192, 79 (1982)). The cross sections were also compared to the statistical molecular-orbital theory of inner-shell ionization for (nearly) symmetric atomic collisions (Mittelman and Wilets, Phys. Rev. 154, 12 (1967)). For fast collisions ({xi}{similar to}1), the ionization cross sections are well reproduced by theories for direct Coulomb ionization. For slower collisions ({xi}{lt}1), the experimental cross sections are systematically higher than the direct-ionization values, but they agree satisfactorily with the summed cross sections for direct Coulomb ionization and for molecular-orbital ionization. Best agreement (within a factor of 2) was found for the sums of MECPSSR and statistical cross sections.

  14. Low-energy structures in strong field ionization revealed by quantum orbits.

    PubMed

    Yan, Tian-Min; Popruzhenko, S V; Vrakking, M J J; Bauer, D

    2010-12-17

    Experiments on atoms in intense laser pulses and the corresponding exact ab initio solutions of the time-dependent Schrödinger equation (TDSE) yield photoelectron spectra with low-energy features that are not reproduced by the otherwise successful work horse of strong field laser physics: the "strong field approximation" (SFA). In the semiclassical limit, the SFA possesses an appealing interpretation in terms of interfering quantum trajectories. It is shown that a conceptually simple extension towards the inclusion of Coulomb effects yields very good agreement with exact TDSE results. Moreover, the Coulomb quantum orbits allow for a physically intuitive interpretation and detailed analysis of all low-energy features in the semiclassical regime, in particular, the recently discovered "low-energy structure" [C. I. Blaga, Nature Phys. 5, 335 (2009) and W. Quan, Phys. Rev. Lett. 103, 093001 (2009).

  15. Low-Energy Structures in Strong Field Ionization Revealed by Quantum Orbits

    SciTech Connect

    Yan, Tian-Min; Popruzhenko, S. V.; Vrakking, M. J. J.; Bauer, D.

    2010-12-17

    Experiments on atoms in intense laser pulses and the corresponding exact ab initio solutions of the time-dependent Schroedinger equation (TDSE) yield photoelectron spectra with low-energy features that are not reproduced by the otherwise successful work horse of strong field laser physics: the 'strong field approximation' (SFA). In the semiclassical limit, the SFA possesses an appealing interpretation in terms of interfering quantum trajectories. It is shown that a conceptually simple extension towards the inclusion of Coulomb effects yields very good agreement with exact TDSE results. Moreover, the Coulomb quantum orbits allow for a physically intuitive interpretation and detailed analysis of all low-energy features in the semiclassical regime, in particular, the recently discovered 'low-energy structure' [C. I. Blaga et al., Nature Phys. 5, 335 (2009) and W. Quan et al., Phys. Rev. Lett. 103, 093001 (2009)].

  16. A vacuum ultraviolet pulsed field ionization-photoelectron study of cyanogen cation in the energy range of 13.2-15.9 eVa)

    NASA Astrophysics Data System (ADS)

    Hochlaf, M.; Baer, Tomas; Qian, X.-M.; Ng, C. Y.

    2005-10-01

    The vacuum ultraviolet pulsed field ionization-photoelectron and photoionization efficiency spectra of NCCN have been measured in the energy region of 13.25-17.75 eV. The analyses of these spectra have provided accurate ionization energy (IE) values of 13.371±0.001, 14.529±0.001, 14.770±0.001, and 15.516±0.001eV for the formation of NCCN+ in the X˜Πg2, ÃΣg+2, B˜Σu+2, and C˜Πu2 states, respectively. The ionization energy [NCCN+(B˜Σu+2)] value determined here indicates that the origin of the NCCN+(B˜Σu+2) state lies lower in energy by 25 meV than previously reported. A set of spectroscopic parameters for NCCN+(X˜Πg2) has been calculated using high level ab initio calculations. The experimental spectra are found to consist of ionizing transitions populating the vibronic levels of NCCN+, which consist of pure vibronic progressions, combination modes involving the symmetric CN stretch, the CC stretch, and even quanta of the antisymmetric CN stretch, and bending vibrations. These bands are identified with the guidance of the present ab initio calculations.

  17. The Effects of the Pauli Exclusion Principle in Determining the Ionization Energies of the Helium Atom and Helium-Like Ions

    ERIC Educational Resources Information Center

    Deeney, F. A.; O'Leary, J. P.

    2012-01-01

    For helium and helium-like ions, we have examined the differences between the values of the ionization energies as calculated from the Bohr theory and those measured in experiments. We find that these differences vary linearly with the atomic number of the system. Using this result, we show how the Bohr model for single-electron systems may be…

  18. The Effects of the Pauli Exclusion Principle in Determining the Ionization Energies of the Helium Atom and Helium-Like Ions

    ERIC Educational Resources Information Center

    Deeney, F. A.; O'Leary, J. P.

    2012-01-01

    For helium and helium-like ions, we have examined the differences between the values of the ionization energies as calculated from the Bohr theory and those measured in experiments. We find that these differences vary linearly with the atomic number of the system. Using this result, we show how the Bohr model for single-electron systems may be…

  19. Large-scale relativistic calculations of ionization energies and total binding energies of all atoms and positive atomic ions with nuclear charge Z = 1-110

    NASA Astrophysics Data System (ADS)

    Kramida, Alexander; Froese Fischer, Charlotte; Reader, Joseph; Indelicato, Paul

    2015-05-01

    The latest versions of advanced multiconfiguration Dirac-Fock atomic codes, MCDFGME and Grasp2K, are used to calculate ionization energies (IE) and total binding energies of all atomic systems. Comparison with experiment and other benchmark data shows an excellent accuracy achieved in these calculations for H-, He-, and Li-like ions. In particular, our results for H-like ions with Z >2, obtained with the MCDFGME code, are the most accurate available today. For multi-electron ions, we combine the accurate single-configuration MCDFGME calculations with the correlation-difference energy (difference between the multiconfiguration and single-configuration total energies) calculated with Grasp2K. This approach results in a dramatically improved agreement of calculated IEs with experiment (less than 0.7 eV on average) for all systems, excluding those involving open f-shells. The most probable ground states are found for most systems, leaving questionable only about 100 out of total 6105 considered systems.

  20. Experimental determination of the effective point of measurement of cylindrical ionization chambers for high-energy photon and electron beams.

    PubMed

    Huang, Yanxiao; Willomitzer, Christian; Zakaria, Golam Abu; Hartmann, Guenther H

    2010-01-01

    Measurements of depth-dose curves in water phantom using a cylindrical ionization chamber require that its effective point of measurement is located at the measuring depth. Recommendations for the position of the effective point of measurement with respect to the central axis valid for high-energy electron and photon beams are given in dosimetry protocols. According to these protocols, the use of a constant shift P(eff) is currently recommended. However, this is still based on a very limited set of experimental results. It is therefore expected that an improved knowledge of the exact position of the effective point of measurement will further improve the accuracy of dosimetry. Recent publications have revealed that the position of the effective point of measurement is indeed varying with beam energy, field size and also with chamber geometry. The aim of this study is to investigate whether the shift of P(eff) can be taken to be constant and independent from the beam energy. An experimental determination of the effective point of measurement is presented based on a comparison between cylindrical chambers and a plane-parallel chamber using conventional dosimetry equipment. For electron beams, the determination is based on the comparison of halfvalue depth R(50) between the cylindrical chamber of interest and a well guarded plane-parallel Roos chamber. For photon beams, the depth of dose maximum, d(max), the depth of 80% dose, d(80), and the dose parameter PDD(10) were used. It was again found that the effective point of measurement for both, electron and photon beams Dosimetry, depends on the beam energy. The deviation from a constant value remains very small for photons, whereas significant deviations were found for electrons. It is therefore concluded that use of a single upstream shift value from the centre of the cylindrical chamber as recommended in current dosimetry protocols is adequate for photons, however inadequate for accurate electron beam dosimetry.

  1. Double-electron capture by highly-ionized atoms isolated at very low energy

    NASA Astrophysics Data System (ADS)

    Fogwell Hoogerheide, Shannon; Dreiling, Joan M.; Sahiner, Arda; Tan, Joseph N.

    2016-05-01

    Charge exchange with background gases, also known as electron capture processes, is important in the study of comets, controlled fusion energy, anti-matter atoms, and proposed one-electron ions in Rydberg states. However, there are few experiments in the very low energy regime that could be useful for further theoretical development. At NIST, highly-charged ions extracted from an electron-beam ion trap can be isolated with energy < 10 eV in a compact Penning trap. By controlling the background gas pressure and composition, the charge exchange rates can be studied. Fully stripped neon or other ions are held in the trap for varying lengths of time and allowed to interact with different background gases at multiple pressures. The ions are then pulsed to a time-of-flight detector to count the population of each charge state. Analysis using a system of rate equations yields information about the ion cloud expansion and single-electron capture rates. A substantial amount of double-electron capture is also observed. We present the relative rates and discuss the error budget. SFH and JMD were funded by National Research Council Research Associateship Awards during some of this work.

  2. Accurate ab initio predictions of ionization energies and heats of formation for the 2-propyl, phenyl, and benzyl radicals

    NASA Astrophysics Data System (ADS)

    Lau, K.-C.; Ng, C. Y.

    2006-01-01

    The ionization energies (IEs) for the 2-propyl (2-C3H7), phenyl (C6H5), and benzyl (C6H5CH2) radicals have been calculated by the wave-function-based ab initio CCSD(T)/CBS approach, which involves the approximation to the complete basis set (CBS) limit at the coupled cluster level with single and double excitations plus quasiperturbative triple excitation [CCSD(T)]. The zero-point vibrational energy correction, the core-valence electronic correction, and the scalar relativistic effect correction have been also made in these calculations. Although a precise IE value for the 2-C3H7 radical has not been directly determined before due to the poor Franck-Condon factor for the photoionization transition at the ionization threshold, the experimental value deduced indirectly using other known energetic data is found to be in good accord with the present CCSD(T)/CBS prediction. The comparison between the predicted value through the focal-point analysis and the highly precise experimental value for the IE(C6H5CH2) determined in the previous pulsed field ionization photoelectron (PFI-PE) study shows that the CCSD(T)/CBS method is capable of providing an accurate IE prediction for C6H5CH2, achieving an error limit of 35 meV. The benchmarking of the CCSD(T)/CBS IE(C6H5CH2) prediction suggests that the CCSD(T)/CBS IE(C6H5) prediction obtained here has a similar accuracy of 35 meV. Taking into account this error limit for the CCSD(T)/CBS prediction and the experimental uncertainty, the CCSD(T)/CBS IE(C6H5) value is also consistent with the IE(C6H5) reported in the previous HeI photoelectron measurement. Furthermore, the present study provides support for the conclusion that the CCSD(T)/CBS approach with high-level energy corrections can be used to provide reliable IE predictions for C3-C7 hydrocarbon radicals with an uncertainty of +/-35 meV. Employing the atomization scheme, we have also computed the 0 K (298 K) heats of formation in kJ/mol at the CCSD(T)/CBS level for 2-C3H7

  3. Optical selection rules for shallow donors in 4H-SiC and ionization energy of the nitrogen donor at the hexagonal site

    NASA Astrophysics Data System (ADS)

    Ivanov, I. G.; Magnusson, B.; Janzén, E.

    2003-04-01

    The selection rules for transitions between the electronic levels of shallow donors in 4H-SiC in the dipole approximation are derived. The ionization energy of the shallow nitrogen donor (at hexagonal site) is determined to be 61.4±0.5 meV by analyzing the photothermal ionization and infrared absorption spectra of nitrogen doped samples in the frame of model that approximates the effective-mass Hamiltonian in 4H-SiC with Hamiltonian of cylindric symmetry (Faulkner’s model).

  4. Soft x-ray ionization induced fragmentation of glycine

    NASA Astrophysics Data System (ADS)

    Itälä, E.; Kooser, K.; Rachlew, E.; Huels, M. A.; Kukk, E.

    2014-06-01

    X-ray absorption commonly involves dissociative core ionization producing not only momentum correlated charged fragments but also low- and high-energy electrons capable of inducing damage in living tissue. This gives a natural motivation for studying the core ionization induced fragmentation processes in biologically important molecules such as amino acids. Here the fragmentation of amino acid glycine following carbon 1s core ionization has been studied. Using photoelectron-photoion-photoion coincidence technique, a detailed analysis on fragmentation of the sample molecule into pairs of momentum correlated cations has been carried out. The main characteristics of core ionization induced fragmentation of glycine were found to be the rupture of the C-Cα bond and the presence of the CNH_2^+ fragment.

  5. Soft x-ray ionization induced fragmentation of glycine.

    PubMed

    Itälä, E; Kooser, K; Rachlew, E; Huels, M A; Kukk, E

    2014-06-21

    X-ray absorption commonly involves dissociative core ionization producing not only momentum correlated charged fragments but also low- and high-energy electrons capable of inducing damage in living tissue. This gives a natural motivation for studying the core ionization induced fragmentation processes in biologically important molecules such as amino acids. Here the fragmentation of amino acid glycine following carbon 1s core ionization has been studied. Using photoelectron-photoion-photoion coincidence technique, a detailed analysis on fragmentation of the sample molecule into pairs of momentum correlated cations has been carried out. The main characteristics of core ionization induced fragmentation of glycine were found to be the rupture of the C-Cα bond and the presence of the CNH(2)(+) fragment.

  6. Soft x-ray ionization induced fragmentation of glycine

    SciTech Connect

    Itälä, E.; Kooser, K.; Rachlew, E.; Huels, M. A.; Kukk, E.

    2014-06-21

    X-ray absorption commonly involves dissociative core ionization producing not only momentum correlated charged fragments but also low- and high-energy electrons capable of inducing damage in living tissue. This gives a natural motivation for studying the core ionization induced fragmentation processes in biologically important molecules such as amino acids. Here the fragmentation of amino acid glycine following carbon 1s core ionization has been studied. Using photoelectron-photoion-photoion coincidence technique, a detailed analysis on fragmentation of the sample molecule into pairs of momentum correlated cations has been carried out. The main characteristics of core ionization induced fragmentation of glycine were found to be the rupture of the C–C{sub α} bond and the presence of the CNH{sub 2}{sup +} fragment.

  7. X-alpha calculation of transition energies in multiply ionized atoms

    NASA Technical Reports Server (NTRS)

    Ringers, D. A.; Chen, M. H.

    1974-01-01

    It is shown that the accuracy of calculations can be improved if appropriate (different) values of alpha are used for each configuration. Alternatively, the Slater Transition state can be used, wherein a total energy difference is related to a difference in single electron eigenvalues. By a series expansion, the value of alpha for an excited configuration can be related to its value for the ground state configuration. The terms Delta alpha (delta Epsilon/delta alpha) exhibit a similar dependence on atomic number as the ground state values of alpha. Results of sample calculations are reported and compared with experiment.

  8. Elastic scattering of low energy electrons in partially ionized dense semiclassical plasma

    SciTech Connect

    Dzhumagulova, K. N. Shalenov, E. O.; Ramazanov, T. S.

    2015-08-15

    Elastic scattering of electrons by hydrogen atoms in a dense semiclassical hydrogen plasma for low impact energies has been studied. Differential scattering cross sections were calculated within the effective model of electron-atom interaction taking into account the effect of screening as well as the quantum mechanical effect of diffraction. The calculations were carried out on the basis of the phase-function method. The influence of the diffraction effect on the Ramsauer–Townsend effect was studied on the basis of a comparison with results made within the effective polarization model of the Buckingham type.

  9. Elastic scattering of low energy electrons in partially ionized dense semiclassical plasma

    NASA Astrophysics Data System (ADS)

    Dzhumagulova, K. N.; Shalenov, E. O.; Ramazanov, T. S.

    2015-08-01

    Elastic scattering of electrons by hydrogen atoms in a dense semiclassical hydrogen plasma for low impact energies has been studied. Differential scattering cross sections were calculated within the effective model of electron-atom interaction taking into account the effect of screening as well as the quantum mechanical effect of diffraction. The calculations were carried out on the basis of the phase-function method. The influence of the diffraction effect on the Ramsauer-Townsend effect was studied on the basis of a comparison with results made within the effective polarization model of the Buckingham type.

  10. {{\\rm{H}}}_{2}\\,X{}^{1}{{\\rm{\\Sigma }}}_{g}^{+}-c{}^{3}{{\\rm{\\Pi }}}_{u} Excitation by Electron Impact: Energies, Spectra, Emission Yields, Cross-sections, and H(1s) Kinetic Energy Distributions

    NASA Astrophysics Data System (ADS)

    Liu, Xianming; Shemansky, Donald E.; Yoshii, Jean; Liu, Melinda J.; Johnson, Paul V.; Malone, Charles P.; Khakoo, Murtadha A.

    2017-10-01

    The c{}3{{{\\Pi }}}u state of the hydrogen molecule has the second largest triplet-state excitation cross-section, and plays an important role in the heating of the upper thermospheres of outer planets by electron excitation. Precise energies of the H2, D2, and HD c{}3{{{\\Pi }}}u-(v,N) levels are calculated from highly accurate ab initio potential energy curves that include relativistic, radiative, and empirical non-adiabatic corrections. The emission yields are determined from predissociation rates and refined radiative transition probabilities. The excitation function and excitation cross-section of the c{}3{{{\\Pi }}}u state are extracted from previous theoretical calculations and experimental measurements. The emission cross-section is determined from the calculated emission yield and the extracted excitation cross-section. The kinetic energy (E k ) distributions of H atoms produced via the predissociation of the c{}3{{{\\Pi }}}u state, the c{}3{{{\\Pi }}}u- – b{}3{{{Σ }}}u+ dissociative emission by the magnetic dipole and electric quadrupole, and the c{}3{{{\\Pi }}}u – a{}3{{{Σ }}}g+ – b{}3{{{Σ }}}u+ cascade dissociative emission by the electric dipole are obtained. The predissociation of the c{}3{{{\\Pi }}}u+ and c{}3{{{\\Pi }}}u- states both produce H(1s) atoms with an average E k of ∼4.1 eV/atom, while the c{}3{{{\\Pi }}}u- – b{}3{{{Σ }}}u+ dissociative emissions by the magnetic dipole and electric quadrupole give an average E k of ∼1.0 and ∼0.8 eV/atom, respectively. The c{}3{{{\\Pi }}}u – a{}3{{{Σ }}}g+ – b{}3{{{Σ }}}u+ cascade and dissociative emission gives an average E k of ∼1.3 eV/atom. On average, each H2 excited to the c{}3{{{\\Pi }}}u state in an H2-dominated atmosphere deposits ∼7.1 eV into the atmosphere while each H2 directly excited to the a{}3{{{Σ }}}g+ and d{}3{{{\\Pi }}}u states contribute ∼2.3 and ∼3.3 eV, respectively, to the atmosphere. The spectral distribution of the calculated continuum emission

  11. A discharge flow-photoionization mass spectrometric study of the FO(X 2 Pi i) radical. Photoionization efficiency spectrum and ionization energy

    NASA Technical Reports Server (NTRS)

    Zhang, Zhengyu; Kuo, Szu-Cherng; Klemm, R. Bruce; Monks, Paul S.; Stief, Louis J.

    1994-01-01

    Photoionization efficiency spectra of FO were measured over the wavelength range 80.0-100.0 nm and in the ionization threshold region, 94.0-100.0 nm, using a discharge flow-photoionization mass spectrometer apparatus coupled to a synchrotron radiation source. FO was generated by the reaction of F2P atoms with NO3 and via a F2O2 discharge. A value of 12.78 +/- 0.03 eV was obtained for the adiabatic ionization energy of FO from photoion thresholds which corresponds to FO(+)(X 3 Sigma -) from FO(X 2 Pi i). These results, which are the first to be obtained by direct Photo-ionization mass spectrometry (PIMS) measurements, corroborate those of a photoelectron spectroscopy (PES) study; however, the ionization energy determined here is free from interferences due to other species which complicated the PES measurement. A value of 109.5 +/- 8.0 kJ/mol for Delta f H 0 298(FO) is computed from the present value of IE(FO) and a previous appearance energy measurement, and a value for the proton affinity of FO is calculated to be 511.5 +/- 10.0 kJ/mol.

  12. A discharge flow-photoionization mass spectrometric study of the FO(X 2 Pi i) radical. Photoionization efficiency spectrum and ionization energy

    NASA Technical Reports Server (NTRS)

    Zhang, Zhengyu; Kuo, Szu-Cherng; Klemm, R. Bruce; Monks, Paul S.; Stief, Louis J.

    1994-01-01

    Photoionization efficiency spectra of FO were measured over the wavelength range 80.0-100.0 nm and in the ionization threshold region, 94.0-100.0 nm, using a discharge flow-photoionization mass spectrometer apparatus coupled to a synchrotron radiation source. FO was generated by the reaction of F2P atoms with NO3 and via a F2O2 discharge. A value of 12.78 +/- 0.03 eV was obtained for the adiabatic ionization energy of FO from photoion thresholds which corresponds to FO(+)(X 3 Sigma -) from FO(X 2 Pi i). These results, which are the first to be obtained by direct Photo-ionization mass spectrometry (PIMS) measurements, corroborate those of a photoelectron spectroscopy (PES) study; however, the ionization energy determined here is free from interferences due to other species which complicated the PES measurement. A value of 109.5 +/- 8.0 kJ/mol for Delta f H 0 298(FO) is computed from the present value of IE(FO) and a previous appearance energy measurement, and a value for the proton affinity of FO is calculated to be 511.5 +/- 10.0 kJ/mol.

  13. Atomic ionization by intense laser pulses of short duration: Photoelectron energy and angular distributions

    SciTech Connect

    Dondera, M.

    2010-11-15

    We introduce an adequate integral representation of the wave function in the asymptotic region, valid for the stage postinteraction between a one-electron atom and a laser pulse of short duration, as a superposition of divergent radial spherical waves. Starting with this representation, we derive analytic expressions for the energy and angular distributions of the photoelectrons and we show their connection with expressions used before in the literature. Using our results, we propose a method to extract the photoelectron distributions from the time dependence of the wave function at large distances. Numerical results illustrating the method are presented for the photoionization of hydrogenlike atoms from the ground state and several excited states by extreme ultraviolet pulses with a central wavelength of 13.3 nm and several intensities around the value I{sub 0}{approx_equal}3.51x10{sup 16} W/cm{sup 2}.

  14. CNT Sensors for Detecting Gases with Low Adsorption Energy by Ionization

    PubMed Central

    Kim, Seongjeen

    2006-01-01

    In case of typical chemical gas sensors reacted by gas adsorption on surface of an active layer, it is difficult to detect some gases which have low chemical adsorption energy like inert gases. In this paper, we report a gas sensor using carbon nanotube(CNT) array as electron emitters for the purpose of detecting these gases. Specifically, sensors were fabricated with applications of glass patterning by a sand-blast process and of anodic bonding between glass and silicon to improve the compactness of the structure and the reliability in process. The proposed sensor, based on an electrical discharge theory known as Paschen's law, worked by figuring the changes of dark discharge current and initial breakdown voltage depending on the concentration and the identity of gases. In this work, air and Ar gases were examined and discussed.

  15. Multiply-ionized atoms isolated at low energy in a unitary Penning trap

    SciTech Connect

    Tan, Joseph N. Hoogerheide, Shannon Fogwell Guise, Nicholas D.; Brewer, Samuel M.

    2015-01-09

    Ions extracted from the EBIT at NIST are slowed and captured in a Penning trap that is made very compact (< 150 cm{sup 3}) by a unitary architecture [1]. Measurements after 1 ms of ion storage indicate that the isolated ions are distributed with 5.5(5) eV of energy spread, which is roughly 2 orders of magnitude lower than expected in the ion source, without implementing any active cooling [2]. Some experiments are discussed. One goal is to produce one-electron ions in high angular momentum states for studying optical transitions between Rydberg states that could potentially enable new tests of quantum electrodynamics (QED) and determinations of fundamental constants [3].

  16. Photo-Double Ionization: Threshold Law and Low-Energy Behavior

    NASA Technical Reports Server (NTRS)

    Bhatia, A. K.; Temkin, A.

    2007-01-01

    The threshold law for photoejection of two electrons from atoms (PDI) is derived from a modification of the Coulomb-dipole (C-D) theory. The C-D theory applies to two-electron ejection from negative ions (photo-double detachment:PDD). The modification consists of correctly accounting for the fact that in PDI that the two escaping electrons see a Coulomb field, asymptotically no matter what their relative distances from the residual ion are. We find in the contralinear spherically symmetric model that the analytic threshold law Q(E), i.e. the yield of residual ions, to be Q Integral of (E) varies as E + (C(sub w) E(sup gamma W)) +CE(sup 5/4) sin [1/2 ln E + phi]/ln(E). The first and third terms are beyond the Wannier law. Our threshold law can only be rigorously justified for residual energies <= 10(exp -3) eV. Nevertheless in the present experimental range (0.1 - 4 eV), the form, even without the second term, can be fitted to experimental results of PDI for He, Li, and Be, in contrast to the Wannier law which has a larger deviation from the data for Li and Be.

  17. Photo-Double Ionization: Threshold Law and Low-Energy Behavior

    NASA Technical Reports Server (NTRS)

    Bhatia, Anand

    2008-01-01

    The threshold law for photoejection of two electrons from atoms (PDI) is derived from a modification of the Coulomb-dipole (C-D) theory. The C-D theory applies to two-electron ejection from negative ions (photo-double detachment:PDD). The modification consists of correctly accounting for the fact that in PDI that the two escaping electrons see a Coulomb field, asymptotically no matter what their relative distances from the residual ion are. We find in the contralinear spherically symmetric model that the analytic threshold law Q(E),i. e. the yield of residual ions, to be Qf(E)approaches E + CwE(sup gamma(w)) + CE(sup 5/4)sin[1/2 ln(E + theta)]/ln(E). The first and third terms are beyond the Wannier law. Our threshold law can only be rigorously justified for residual energies less than or equal to 10(exp -3) eV. Nevertheless in the present experimental range (0.1 - 4 eV), the form, even without the second term, can be fitted to experimental results of PDI for He, Li, and Be, in contrast to the Wannier law which has a larger deviation from the data for Li and Be, for both of which the data show signs of modulation.

  18. Photo-Double Ionization: Threshold Law and Low-Energy Behavior

    NASA Technical Reports Server (NTRS)

    Bhatia, Anand

    2008-01-01

    The threshold law for photoejection of two electrons from atoms (PDI) is derived from a modification of the Coulomb-dipole (C-D) theory. The C-D theory applies to two-electron ejection from negative ions (photo-double detachment:PDD). The modification consists of correctly accounting for the fact that in PDI that the two escaping electrons see a Coulomb field, asymptotically no matter what their relative distances from the residual ion are. We find in the contralinear spherically symmetric model that the analytic threshold law Q(E),i. e. the yield of residual ions, to be Qf(E)approaches E + CwE(sup gamma(w)) + CE(sup 5/4)sin[1/2 ln(E + theta)]/ln(E). The first and third terms are beyond the Wannier law. Our threshold law can only be rigorously justified for residual energies less than or equal to 10(exp -3) eV. Nevertheless in the present experimental range (0.1 - 4 eV), the form, even without the second term, can be fitted to experimental results of PDI for He, Li, and Be, in contrast to the Wannier law which has a larger deviation from the data for Li and Be, for both of which the data show signs of modulation.

  19. Photo-Double Ionization: Threshold Law and Low-Energy Behavior

    NASA Technical Reports Server (NTRS)

    Bhatia, A. K.; Temkin, A.

    2007-01-01

    The threshold law for photoejection of two electrons from atoms (PDI) is derived from a modification of the Coulomb-dipole (C-D) theory. The C-D theory applies to two-electron ejection from negative ions (photo-double detachment:PDD). The modification consists of correctly accounting for the fact that in PDI that the two escaping electrons see a Coulomb field, asymptotically no matter what their relative distances from the residual ion are. We find in the contralinear spherically symmetric model that the analytic threshold law Q(E), i.e. the yield of residual ions, to be Q Integral of (E) varies as E + (C(sub w) E(sup gamma W)) +CE(sup 5/4) sin [1/2 ln E + phi]/ln(E). The first and third terms are beyond the Wannier law. Our threshold law can only be rigorously justified for residual energies <= 10(exp -3) eV. Nevertheless in the present experimental range (0.1 - 4 eV), the form, even without the second term, can be fitted to experimental results of PDI for He, Li, and Be, in contrast to the Wannier law which has a larger deviation from the data for Li and Be.

  20. Generation of 500 MeV-1 GeV energy electrons from laser wakefield acceleration via ionization induced injection using CO{sub 2} mixed in He

    SciTech Connect

    Mo, M. Z.; Ali, A.; Fedosejevs, R.; Fourmaux, S.; Lassonde, P.; Kieffer, J. C.

    2013-04-01

    Laser wakefield acceleration of 500 MeV to 1 GeV electron bunches has been demonstrated using ionization injection in mixtures of 4% to 10% of CO{sub 2} in He. 80 TW laser pulses were propagated through 5 mm gas jet targets at electron densities of 0.4-1.5 Multiplication-Sign 10{sup 19}cm{sup -3}. Ionization injection led to lower density thresholds, a higher total electron charge, and an increased probability of producing electrons above 500 MeV in energy compared to self-injection in He gas alone. Electrons with GeV energies were also observed on a few shots and indicative of an additional energy enhancement mechanism.

  1. Effective ionization coefficients, limiting electric fields, and electron energy distributions in CF{sub 3}I + CF{sub 4} + Ar ternary gas mixtures

    SciTech Connect

    Tezcan, S. S.; Dincer, M. S.; Bektas, S.

    2016-07-15

    This paper reports on the effective ionization coefficients, limiting electric fields, electron energy distribution functions, and mean energies in ternary mixtures of (Trifluoroiodomethane) CF{sub 3}I + CF{sub 4} + Ar in the E/N range of 100–700 Td employing a two-term solution of the Boltzmann equation. In the ternary mixture, CF{sub 3}I component is increased while the CF{sub 4} component is reduced accordingly and the 40% Ar component is kept constant. It is seen that the electronegativity of the mixture increases with increased CF{sub 3}I content and effective ionization coefficients decrease while the limiting electric field values increase. Synergism in the mixture is also evaluated in percentage using the limiting electric field values obtained. Furthermore, it is possible to control the mean electron energy in the ternary mixture by changing the content of CF{sub 3}I component.

  2. UNCOVERING THE SPECTRAL ENERGY DISTRIBUTION IN ACTIVE GALAXIES USING HIGH-IONIZATION MID-INFRARED EMISSION LINES

    SciTech Connect

    Melendez, M.; Weaver, K. A.; Kraemer, S. B.; Mushotzky, R. F.

    2011-09-01

    The shape of the spectral energy distribution (SED) of active galaxies in the extreme-ultraviolet (EUV)-soft X-ray band (13.6 eV-1 keV) is uncertain because obscuration by dust and gas can hamper our view of the continuum. To investigate the shape of the SED in this energy band, we have generated a set of photoionization models which reproduce the small dispersion found in correlations between high-ionization mid-infrared emission lines in a sample of hard X-ray-selected active galactic nuclei (AGNs). Our calculations show that a broken power-law continuum model is sufficient to reproduce the [Ne V]{sub 14.32{mu}m}/[Ne III], [Ne V]{sub 24.32{mu}m}/[O IV]{sub 25.89{mu}m}, and [O IV]{sub 25.89{mu}m}/[Ne III] ratios and does not require the addition of a 'big bump' EUV model component. We constrain the EUV-soft X-ray slope, {alpha}{sub i}, to be between 1.5 and 2.0 and derive a best fit of {alpha}{sub i} {approx} 1.9 for Seyfert 1 galaxies, consistent with previous studies of intermediate-redshift quasars. If we assume a blue bump model, most sources in our sample have derived temperatures between T{sub BB} = 10{sup 5.18} K and 10{sup 5.7} K, suggesting that the peak of this component spans a large range of energies extending from {approx}600 A to 1900 A. In this case, the best-fitting peak energy that matches the mid-infrared line ratios of Seyfert 1 galaxies occurs between {approx}700 and 1000 A. Despite the fact that our results do not rule out the presence of an EUV bump, we conclude that our power-law model produces enough photons with energies >4 Ry to generate the observed amount of mid-infrared emission in our sample of Burst Alert Telescope AGNs.

  3. Intensity and Energy Level Analysis of the Vacuum Ultraviolet Spectrum of Four Times Ionize Nickel (Ni V)

    NASA Astrophysics Data System (ADS)

    Ward, Jacob Wolfgang; Nave, Gillian

    2016-01-01

    Recent measurements of four times ionized iron and nickel (Fe V & Ni V) wavelengths in the vacuum ultraviolet (VUV) have been taken using the National Institute for Standards and Technology (NIST) Normal Incidence Vacuum Spectrograph (NIVS) with a sliding spark light source with invar electrodes. The wavelengths observed in those measurements make use of high resolution photographic plates with the majority of observed lines having uncertainties of approximately 3mÅ. In addition to observations made with photographic plates, the same wavelength region was observed with phosphor image plates, which have been demonstrated to be accurate as a method of intensity calibration when used with a deuterium light source. This work will evaluate the use of phosphor image plates and deuterium lamps as an intensity calibration method for the Ni V spectrum in the 1200-1600Å region of the VUV. Additionally, by pairing the observed wavelengths of Ni V with accurate line intensities, it is possible to create an energy level optimization for Ni V providing high accuracy Ritz wavelengths. This process has previously been applied to Fe V and produced Ritz wavelengths that agreed with the above experimental observations.

  4. Zero kinetic energy photoelectron spectroscopy of jet cooled benzo[a]pyrene from resonantly enhanced multiphoton ionization

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Harthcock, Colin; Han, Fangyuan; Kong, Wei

    2011-12-01

    We report zero kinetic energy (ZEKE) photoelectron spectroscopy of benzo[a]pyrene (BaP) via resonantly enhanced multiphoton ionization (REMPI). Our analysis concentrates on the vibrational modes of the first excited state (S1) and those of the ground cationic state (D0). Similar to pyrene, another peri-condensed polycyclic aromatic hydrocarbon we have investigated, the first two electronically excited states of BaP exhibit extensive configuration interactions. However, the two electronic states are of the same symmetry, hence vibronic coupling does not introduce any out-of-plane modes in the REMPI spectrum, and Franck-Condon analysis is qualitatively satisfactory. The ZEKE spectra from the in-plane modes observed in the REMPI spectrum demonstrate strong propensity in preserving the vibrational excitation of the intermediate state. Although several additional bands in combination with the vibrational mode of the intermediate state are identifiable, they are much lower in intensity. This observation implies that the molecular structure of BaP has a tremendous capability to accommodate changes in charge density. All observed bands of the cation are IR active, establishing the role of ZEKE spectroscopy in mapping out far infrared bands for astrophysical applications.

  5. The average local ionization energy as a tool for identifying reactive sites on defect-containing model graphene systems.

    PubMed

    Murray, Jane S; Shields, Zenaida Peralta-Inga; Lane, Pat; Macaveiu, Laura; Bulat, Felipe A

    2013-07-01

    In a continuing effort to further explore the use of the average local ionization energy [Formula: see text] as a computational tool, we have investigated how well [Formula: see text] computed on molecular surfaces serves as a predictive tool for identifying the sites of the more reactive electrons in several nonplanar defect-containing model graphene systems, each containing one or more pentagons. They include corannulene (C20H10), two inverse Stone-Thrower-Wales defect-containing structures C26H12 and C42H16, and a nanotube cap model C22H6, whose end is formed by three fused pentagons. Coronene (C24H12) has been included as a reference planar defect-free graphene model. We have optimized the structures of these systems as well as several monohydrogenated derivatives at the B3PW91/6-31G* level, and have computed their I(r) on molecular surfaces corresponding to the 0.001 au, 0.003 au and 0.005 au contours of the electronic density. We find that (1) the convex sides of the interior carbons of the nonplanar models are more reactive than the concave sides, and (2) the magnitudes of the lowest I(r) surface minima (the I S, min) correlate well with the interaction energies for hydrogenation at these sites. These I S, min values decrease in magnitude as the nonplanarity of the site increases, consistent with earlier studies. A practical benefit of the use of I(r) is that a single calculation suffices to characterize the numerous sites on a large molecular system, such as graphene and defect-containing graphene models.

  6. The effects of the electric and intense laser field on the binding energies of donor impurity states (1s and 2p±) and optical absorption between the related states in an asymmetric parabolic quantum well

    NASA Astrophysics Data System (ADS)

    Kasapoglu, E.; Sakiroglu, S.; Sökmen, I.; Restrepo, R. L.; Mora-Ramos, M. E.; Duque, C. A.

    2016-10-01

    We have calculated the effects of electric and intense laser fields on the binding energies of the ground and some excited states of conduction electrons coupled to shallow donor impurities as well as the total optical absorption coefficient for transitions between 1s and 2p± electron-impurity states in a asymmetric parabolic GaAs/Ga1-x AlxAs quantum well. The binding energies were obtained using the effective-mass approximation within a variational scheme. Total absorption coefficient (linear and nonlinear absorption coefficient) for the transitions between any two impurity states were calculated from first- and third-order dielectric susceptibilities derived within a perturbation expansion for the density matrix formalism. Our results show that the effects of the electric field, intense laser field, and the impurity location on the binding energy of 1s-impurity state are more pronounced compared with other impurity states. If the well center is changed to be Lc<0 (Lc>0), the effective well width decreases (increases), and thus we can obtain the red or blue shift in the resonant peak position of the absorption coefficient by changing the intensities of the electric and non-resonant intense laser field as well as dimensions of the well and impurity positions.

  7. Collision-energy-resolved penning ionization electron spectroscopy of HCOOH, CH3COOH, and HCOOCH3 by collision with He*(2(3)S) metastable atoms.

    PubMed

    Borodin, Andriy; Yamazaki, Masakazu; Kishimoto, Naoki; Ohno, Koichi

    2005-06-02

    Penning ionization of formic acid (HCOOH), acetic acid (CH3COOH), and methyl formate (HCOOCH3) upon collision with metastable He*(2(3)S) atoms was studied by collision-energy/electron-energy-resolved two-dimensional Penning ionization electron spectroscopy (2D-PIES). Anisotropy of interaction between the target molecule and He*(2(3)S) was investigated based on the collision energy dependence of partial ionization cross sections (CEDPICS) obtained from 2D-PIES as well as ab initio molecular orbital calculations for the access of a metastable atom to the target molecule. For the interaction potential calculations, a Li atom was used in place of He*(2(3)S) metastable atom because of its well-known similarity in interaction with targets. The results indicate that in the studied collision energy range the attractive potential localizes around the oxygen atoms and that the potential well at the carbonyl oxygen atom is at least twice as much as that at the hydroxyl oxygen. Moreover we can notice that attractive potential is highly anisotropic. Repulsive interactions can be found around carbon atoms and the methyl group.

  8. Study of dust particle charging in weakly ionized inert gases taking into account the nonlocality of the electron energy distribution function

    SciTech Connect

    Filippov, A. V. Dyatko, N. A.; Kostenko, A. S.

    2014-11-15

    The charging of dust particles in weakly ionized inert gases at atmospheric pressure has been investigated. The conditions under which the gas is ionized by an external source, a beam of fast electrons, are considered. The electron energy distribution function in argon, krypton, and xenon has been calculated for three rates of gas ionization by fast electrons: 10{sup 13}, 10{sup 14}, and 10{sup 15} cm{sup −1}. A model of dust particle charging with allowance for the nonlocal formation of the electron energy distribution function in the region of strong plasma quasi-neutrality violation around the dust particle is described. The nonlocality is taken into account in an approximation where the distribution function is a function of only the total electron energy. Comparative calculations of the dust particle charge with and without allowance for the nonlocality of the electron energy distribution function have been performed. Allowance for the nonlocality is shown to lead to a noticeable increase in the dust particle charge due to the influence of the group of hot electrons from the tail of the distribution function. It has been established that the screening constant virtually coincides with the smallest screening constant determined according to the asymptotic theory of screening with the electron transport and recombination coefficients in an unperturbed plasma.

  9. An Experimental and Theoretical Study on the Ionization Energies of Polyynes (H-(C = C)n-H; n = 1 - 9)

    SciTech Connect

    Kaiser, Ralf I.; Sun, Bian Jian; Lin, Hong Mao; Chang, Agnes H. H.; Mebel, Alexander M.; Kostko, Oleg; Ahmed, Musahid

    2010-05-17

    We present a combined experimental and theoretical work on the ionization energies of polyacetylene -- organic molecules considered as important building blocks to form polycyclic aromatic hydrocarbons (PAHs) in the proto planetary nebulae such as of CRL 618. This set of astrophysical data can be utilized with significant confidence in future astrochemical models of photon-dominated regions and also of the proto planetary nebulae CRL 618. We recommend ionization energies of polyacetylenes from diacetylene up to heptaacetylene with an experimental accuracy of +- 0.05 eV: 10.03 eV (diacetylene), 9.45 eV (triacetylene), 9.08 eV (tetraacetylene), 8.75 eV (pentaacetylene), 8.65 eV (hexaacetylene), and 8.50 eV (heptaacetylene); further, ionization energies and with an accuracy of +- 0.1 eV: 8.32 eV (octaacetylene) and 8.24 eV (nonaacetylene) were computed. Implications of these energies to the redox chemistry involved in the multiply charged metal-ion mediated chemistry of hydrocarbon-rich atmospheres of planets and their moons such as Titan are also discussed.

  10. Ionization Phenomena in Ion-Atom Collisions

    NASA Astrophysics Data System (ADS)

    Deveney, Edward Francis

    Two many-electron ion-atom collision systems are used to investigate atomic and molecular structure and collisional interactions. Electrons emitted from MeV/u C^{3+} projectile target -atom collisions were measured with a high-resolution position -sensitive electron spectrometer at Oak Ridge National Laboratory. The electrons are predominantly ionized by direct projectile -target interactions or autoionizing (AI) from doubly excited AI levels of the ion which were excited in the collision. The energy dependence of directly scattered target electrons, binary-encounter electrons (BEE), is investigated and compared with theory. AI levels of the projectile 1s to nl single electron excited series, (1s2snl) n = 2,3,4,....infty, including the series limit are identified uniquely using energy level calculations. Original Auger yield calculations using a code by Cowan were used to discover a 1/{n^3} scaling in intensities of Auger peaks in the aforementioned series. This is explained using scattering theory. A nonstatistical population of the terms in the (1s2s2l) configuration was identified and investigated as a function of the beam energy and for four different target atoms. Two electron excited configurations are identified and investigated. The angular distribution of a correlated transfer and excitation AI state is measured and compared to theory. The final scattered charge state distributions of Kr^ {n+}, n = 1, 2, 3, 4, 5, projectiles are measured following collisions with Kr targets in the Van de Graaff Laboratory here at The University of Connecticut. Average scattered charge states as high as 12 are observed. It appears that these electrons are ionized during the lifetime of the quasimolecular state but a complete picture of the ionization mechanism(s) is not known. Calculations using a statistical model of ionization, modified in several ways, are compared with the experimental results to see if it is possible to isolate whether or not the electrons originate

  11. Collision-energy-resolved Penning ionization electron spectroscopy of p-benzoquinone: Study of electronic structure and anisotropic interaction with He*(2 3S) metastable atoms

    NASA Astrophysics Data System (ADS)

    Kishimoto, Naoki; Okamura, Kohji; Ohno, Koichi

    2004-06-01

    Collision energy dependence of partial ionization cross sections (CEDPICS) of p-benzoquinone with He*(2 3S) metastable atoms indicates that interaction potentials between p-benzoquinone and He*(2 3S) are highly anisotropic in the studied collision energy range (100-250 meV). Attractive interactions were found around the C=O groups for in-plane and out-of-plane directions, while repulsive interactions were found around CH bonds and the benzenoid ring. Assignment of the first four ionic states of p-benzoquinone and an analogous methyl-substituted compound was examined with CEDPICS and anisotropic distributions of the corresponding two nonbonding oxygen orbitals (nO+,nO-) and two πCC orbitals (πCC+,πCC-). An extra band that shows negative CEDPICS was observed at ca. 7.2 eV in Penning ionization electron spectrum.

  12. Cross sections for ionization of K, L and M shells of atoms by impact of electrons and positrons with energies up to 1 GeV: Analytical formulas

    SciTech Connect

    Bote, David; Salvat, Francesc Jablonski, Aleksander

    2009-11-15

    Analytical formulas are presented for the easy calculation of cross sections for ionization of K, L and M shells of neutral atoms by impact of electrons and positrons with kinetic energies up to 1 GeV. Each formula contains a number of parameters that are characteristic of the element, the active electron shell and the projectile particle. The values of these parameters were determined by fitting the cross section values in an extensive database that was calculated recently by means of a composite algorithm that combines the distorted-wave and plane-wave Born approximations. Tables of parameter values are given for all elements, from hydrogen (Z=1) to einsteinium (Z=99). The proposed analytical expressions yield ionization cross sections that agree with those in the numerical database to within about 1%, except for projectiles with near-threshold energies.

  13. Wall correction factors for calibration of plane-parallel ionization chambers with high-energy photon beams.

    PubMed

    Araki, F; Ikeda, R; Shirakawa, Y; Shimonobou, T; Moribe, N; Takada, T; Takahashi, M; Oura, H; Matoba, M

    2000-09-01

    Most dosimetry protocols recommend that calibration of plane-parallel ionization chambers be performed in an electron beam of sufficiently high energy by comparison with cylindrical chambers. For various plane-parallel chambers, the 1997 IAEA TRS-381 protocol includes an overall perturbation factor pQ for electron beams, a wall correction factor p(wall) for a 60Co beam and the product of two wall corrections k(att)k(m) for 60Co in-air calibration. The recommended values of p(wall) for plane-parallel chambers, however, are limited to certain phantom materials and a 60Co beam, and are not given for other phantom materials and x-ray beams. In this work, the p(wall) values of the commercially available NACP, PTW/Markus and PTW/Roos plane-parallel chambers in a solid water phantom have been determined with 60Co and 4 and 10 MV photon beams. The k(att)k(m) values for the NACP and PTW/Markus chambers have also been obtained. The wall correction factors p(wall) and k(att)k(m) have been determined by intercomparison with a calibrated Farmer chamber. The average value of p(wall) for these plane-parallel chambers was 1.005 +/- 0.1% (1 SD) for 60Co beams and 1.007 +/- 0.2% (1 SD) for both 4 MV and 10 MV photons. The k(att)k(m) values for the NACP and PTW/Markus chambers were about 1.5% lower than other published data.

  14. Experimental analysis of general ion recombination in a liquid-filled ionization chamber in high-energy photon beams

    SciTech Connect

    Chung, Eunah; Seuntjens, Jan; Davis, Stephen

    2013-06-15

    Purpose: To study experimentally the general ion recombination effect in a liquid-filled ionization chamber (LIC) in high-energy photon beams. Methods: The general ion recombination effect on the response of a micro liquid ion chamber (microLion) was investigated with a 6 MV photon beam in normal and SRS modes produced from a Varian{sup Registered-Sign} Novalis Tx{sup TM} linear accelerator. Dose rates of the linear accelerator were set to 100, 400, and 1000 MU/min, which correspond to pulse repetition frequencies of 60, 240, and 600 Hz, respectively. Polarization voltages applied to the microLion were +800 and +400 V. The relative collection efficiency of the microLion response as a function of dose per pulse was experimentally measured with changing polarization voltage and pulse repetition frequencies and was compared with the theoretically calculated value. Results: For the 60 Hz pulse repetition frequency, the experimental relative collection efficiency was not different from the theoretical one for a pulsed beam more than 0.3% for both polarization voltages. For a pulsed radiation beam with a higher pulse repetition frequency, the experimental relative collection efficiency converged to the theoretically calculated efficiency for continuous beams. This result indicates that the response of the microLion tends toward the response to a continuous beam with increasing pulse repetition frequency of a pulsed beam because of low ion mobility in the liquid. Conclusions: This work suggests an empirical method to correct for differences in general ion recombination of a LIC between different radiation fields. More work is needed to quantitatively explain the LIC general ion recombination behavior in pulsed beams generated from linear accelerators.

  15. Experimental analysis of general ion recombination in a liquid-filled ionization chamber in high-energy photon beams.

    PubMed

    Chung, Eunah; Davis, Stephen; Seuntjens, Jan

    2013-06-01

    To study experimentally the general ion recombination effect in a liquid-filled ionization chamber (LIC) in high-energy photon beams. The general ion recombination effect on the response of a micro liquid ion chamber (microLion) was investigated with a 6 MV photon beam in normal and SRS modes produced from a Varian(®) Novalis Tx(TM) linear accelerator. Dose rates of the linear accelerator were set to 100, 400, and 1000 MU∕min, which correspond to pulse repetition frequencies of 60, 240, and 600 Hz, respectively. Polarization voltages applied to the microLion were +800 and +400 V. The relative collection efficiency of the microLion response as a function of dose per pulse was experimentally measured with changing polarization voltage and pulse repetition frequencies and was compared with the theoretically calculated value. For the 60 Hz pulse repetition frequency, the experimental relative collection efficiency was not different from the theoretical one for a pulsed beam more than 0.3% for both polarization voltages. For a pulsed radiation beam with a higher pulse repetition frequency, the experimental relative collection efficiency converged to the theoretically calculated efficiency for continuous beams. This result indicates that the response of the microLion tends toward the response to a continuous beam with increasing pulse repetition frequency of a pulsed beam because of low ion mobility in the liquid. This work suggests an empirical method to correct for differences in general ion recombination of a LIC between different radiation fields. More work is needed to quantitatively explain the LIC general ion recombination behavior in pulsed beams generated from linear accelerators.

  16. Electron ionization of acetylene.

    PubMed

    King, Simon J; Price, Stephen D

    2007-11-07

    Relative partial ionization cross sections and precursor specific relative partial ionization cross sections for fragment ions formed by electron ionization of C2H2 have been measured using time-of-flight mass spectrometry coupled with a 2D ion-ion coincidence technique. We report data for the formation of H+, H+2, C2+, C+/C2+ 2, CH+/C2H+2, CH+2, C+2, and C2H+ relative to the formation of C2H+2, as a function of ionizing electron energy from 30-200 eV. While excellent agreement is found between our data and one set of previously published absolute partial ionization cross sections, some discrepancies exist between the results presented here and two other recent determinations of these absolute partial ionization cross sections. We attribute these differences to the loss of some translationally energetic fragment ions in these earlier studies. Our relative precursor-specific partial ionization cross sections enable us, for the first time, to quantify the contribution to the yield of each fragment ion from single, double, and triple ionization. Analysis shows that at 50 eV double ionization contributes 2% to the total ion yield, increasing to over 10% at an ionizing energy of 100 eV. From our ion-ion coincidence data, we have derived branching ratios for charge separating dissociations of the acetylene dication. Comparison of our data to recent ab initio/RRKM calculations suggest that close to the double ionization potential C2H2+2 dissociates predominantly on the ground triplet potential energy surface (3Sigma*g) with a much smaller contribution from dissociation via the lowest singlet potential energy surface (1Delta g). Measurements of the kinetic energy released in the fragmentation reactions of C2H2+2 have been used to obtain precursor state energies for the formation of product ion pairs, and are shown to be in good agreement with available experimental data and with theory.

  17. The ionization energy of Be2, and spectroscopic characterization of the (1)3Sigmau+, (2)3Pig, and (3)3Pig states.

    PubMed

    Merritt, Jeremy M; Kaledin, Alexey L; Bondybey, Vladimir E; Heaven, Michael C

    2008-07-21

    Low lying electronic states of the beryllium dimer were investigated by laser induced fluorescence (LIF) and resonance enhanced multiphoton ionization (REMPI) techniques. Be(2) was formed by pulsed laser ablation of Be metal in the presence of helium carrier gas, followed by a free jet expansion into vacuum. Several previously unobserved states of the dimer were characterized. These included transitions of the triplet manifold (2)(3)Pi(g) <-- (1)(3)Sigma(u)+ and (3)(3)Pi(g) <-- (1)(3)Sigma(u)+, for which rotationally resolved bands were obtained. In addition, transitions to the v' = 10-18 vibrational levels of the A (1)Pi(u) state were recorded. Photoionization efficiency (PIE) measurements were used to determine an accurate ionization energy (IE) for Be(2) of 7.418(5) eV and the term energy for (1)(3)Sigma(u)+. Above the ionization threshold the PIE spectrum was found to be highly structured, consisting of overlapping Rydberg series that converged on excited vibrational levels of Be(2)+. Analysis of these series yielded a vibration frequency for the X(2)Sigma(u)+ state of 498(20) cm(-1). The bond dissociation energy for Be(2)+, deduced from the IE measurement, was 16 072(40) cm(-1). Multi-reference configuration interaction (MRCI) calculations were carried out for Be(2) and Be(2)+, yielding results that were in excellent agreement with the experimental observations.

  18. Charge and energy-dependence of the Gaussian description of the triply differential cross sections for equal-energy sharing photo-double-ionization of two-electrons ions

    SciTech Connect

    Otranto, S.; Garibotti, C.R.

    2005-03-01

    We evaluate triply differential cross sections (TDCSs) for the photo-double-ionization (PDI) of He-like ions, and equal electron energy sharing, by using the SC3 model for the three-body final state. These cross sections are fitted with the usual dipolar Gaussian form which is found able to describe the theoretical TDCS, and could be applied for the interpretation of experimental data even at intermediate photon energies. We determine the dependence of the correlation factor on the excess energy (E{sub f}) and target nuclear charge (Z). We find that its width has an E{sub f}{sup 1/4} dependence near the atomic double-ionization threshold but departs from this law and attains a plateau as the excess energy increases. We compare our results with the predictions of classical and semiclassical Wannier approaches.

  19. Measurements of K-shell ionization cross sections of Al and L-shell x-ray production cross sections of Se by intermediate-energy electron impact

    NASA Astrophysics Data System (ADS)

    Mei, C. S.; Wu, Y.; Yuan, Y.; Chang, C. H.; Qian, Z. C.; Zhu, J. J.; Moharram, Khalid

    2016-12-01

    The K-shell ionization cross sections of Al (Z = 13) and the total L-shell x-ray production cross sections of Se (Z = 34) from electron impacts with kinetic energies ranging from several keV to several tenths of keV have been measured by using an improved experimental setup. An Al target of monoatomic and grid carbon substrate, which consisted of ultrathin Al film (∼3 nm) deposited onto grid carbon substrate (∼200 nm) with a layer of monoatomic carbon between the film and the grid substrate, was first proposed and measured. In addition, targets of Al film (∼3 nm) and Se film (∼7.8 nm) deposited respectively onto thick carbon substrate (∼2 mm) were also measured. Our experimental results are compared with the distorted-wave Born approximation (DWBA) theory and experimental data from the literature. It has been observed that within the uncertainties, the DWBA agrees with our experimental measurements of K-shell ionization cross sections of Al and the total L-shell x-ray production cross sections of Se, and our measured data of Al K-shell ionization cross sections are consistent with the available experimental data. This is the first time that experimental data of Se-L-shell x-ray production cross sections in the intermediate-energy region have been published.

  20. Mass analyzed threshold ionization spectroscopy of deuterium substituted N-methylaniline and N-ethylaniline cations: isotope effect on transition energy and large amplitude vibrations

    NASA Astrophysics Data System (ADS)

    Lin, Jieli; Lin, Jung Lee; Tzeng, Wen Bih

    2003-12-01

    We have recorded the resonant two-photon ionization (R2PI) and mass analyzed threshold ionization (MATI) spectra of deuterium substituted N-methylaniline (NMA-d1) and N-ethylaniline (NEA-d1) to investigate the influence of the N-deuteration on the transition energy and the large amplitude alkyl vibration. The origin of the S 1←S 0 electronic transition (EE) and the adiabatic ionization energy (IE) of NMA-d1 are determined to be 33,294 ± 1 and 59,801 ± 5 cm -1, whereas those of NEA-d1 are 33,301 ± 1 and 59,185 ± 5 cm -1, respectively. Comparing these data with those of NMA and NEA suggests that N-deuteration give rise to a blue shift of 2-4 cm -1 in the EE and a red shift of 19-21 cm -1 in the IE. These isotope shifts are little affected by the length of the alkyl group attached to the nitrogen atom. The present results also show that the N-deuteration influences more on the large amplitude motions of the CH 3 torsion, the C 2H 5 bending, and the N-inversion than the localized benzene ring vibrations.

  1. Three-dimensional modeling of ionized gas. II. Spectral energy distributions of massive and very massive stars in stationary and time-dependent modeling of the ionization of metals in H II regions

    NASA Astrophysics Data System (ADS)

    Weber, J. A.; Pauldrach, A. W. A.; Hoffmann, T. L.

    2015-11-01

    Context. H II regions play a crucial role in the measurement of the chemical composition of the interstellar medium and provide fundamental data about element abundances that constrain models of galactic chemical evolution. Discrepancies that still exist between observed emission line strengths and those predicted by nebular models can be partly attributed to the spectral energy distributions (SEDs) of the sources of ionizing radiation used in the models as well as to simplifying assumptions made in nebular modeling. Aims: One of the main influences on the nebular spectra is the metallicity, both nebular and stellar, which shows large variations even among nearby galaxies. Although nebular modeling often involves testing of different nebular metallicities against their influence on the predicted spectra, adequate grids of stellar atmospheres and realistic SEDs for different metallicities are still lacking. This is unfortunate because the influence of stellar metallicity on nebular line strength ratios, via its effect on the SEDs, is of similar importance as variations in the nebular metallicity. To overcome this deficiency we have computed a grid of model atmosphere SEDs for massive and very massive O-type stars covering a range of metallicities from significantly subsolar (0.1 Z⊙) to supersolar (2 Z⊙). Methods: The SEDs have been computed using a state-of-the-art model atmosphere code that takes into account the attenuation of the ionizing flux by the spectral lines of all important elements and the hydrodynamics of the radiatively driven winds and their influence on the SEDs. For the assessment of the SEDs in nebular simulations we have developed a (heretofore not available) 3D radiative transfer code that includes a time-dependent treatment of the metal ionization. Results: Using the SEDs in both 1D and 3D nebular models we explore the relative influence of stellar metallicity, gas metallicity, and inhomogeneity of the gas on the nebular ionization structure

  2. A discharge flow-photoionization mass spectrometric study of hydroxymethyl radicals (H{sub 2}COH and H{sub 2}COD): Photoionization spectrum and ionization energy

    SciTech Connect

    Tao, W.; Klemm, R.B.; Nesbitt, F.L.; Stief, L.J.

    1992-01-09

    The photoionization spectrum of H{sub 2}COH was measured over the wavelength range 140-170 nm by using a discharge flow-photoionization mass spectrometer apparatus with synchrotron radiation. Hydroxymethyl radicals (H{sub 2}COH and H{sub 2}COD) were generated in a flow tube by the reaction of F atoms with CH{sub 3}OH(D). Ionization energies (IE) were determined directly from photoion thresholds. The IE values, 7.56 {plus_minus} 0.02 and 7.55 {plus_minus} 0.02 eV for H{sub 2}COH and H{sub 2}COD, respectively, are consistent with previous measurements. Also, the dissociative ionization process, presumed to be H{sub 3}CO* {yields} HCO{sup +} + H{sub 2}, was observed with a threshold at 8.61 {plus_minus} 0.06 eV. 44 refs., 5 figs.

  3. Low energy ionizing collisions between N2 and CO beam molecules and CO, N2, NO, CH4, and CO2 target molecules

    NASA Technical Reports Server (NTRS)

    Utterback, N. G.; Van Zyl, B.

    1978-01-01

    Absolute total negative charge production cross sections for N2 + CO, CO + N2, CO + CO, N2 + NO, N2 + CH4, and N2 + CO2 collisions are reported, and a simple model of collisions is discussed. The cross sections were measured to within about 1 eV of their thresholds. Specific reaction channels were investigated by referring to mass spectrometric identification of the product ions scattered in the forward direction, and these product ion identifications were used to explain characteristic structures in the total charge production cross sections in the near-threshold regions. The extent of the importance of dissociative ionization and 'simple' ionization in the studied collisions at low energy is considered, and charge transfer cross sections for (CO)+ + CO, CO(+) + CH4, and N2(+) + CH4 are presented.

  4. Low energy ionizing collisions between N2 and CO beam molecules and CO, N2, NO, CH4, and CO2 target molecules

    NASA Technical Reports Server (NTRS)

    Utterback, N. G.; Van Zyl, B.

    1978-01-01

    Absolute total negative charge production cross sections for N2 + CO, CO + N2, CO + CO, N2 + NO, N2 + CH4, and N2 + CO2 collisions are reported, and a simple model of collisions is discussed. The cross sections were measured to within about 1 eV of their thresholds. Specific reaction channels were investigated by referring to mass spectrometric identification of the product ions scattered in the forward direction, and these product ion identifications were used to explain characteristic structures in the total charge production cross sections in the near-threshold regions. The extent of the importance of dissociative ionization and 'simple' ionization in the studied collisions at low energy is considered, and charge transfer cross sections for (CO)+ + CO, CO(+) + CH4, and N2(+) + CH4 are presented.

  5. Ionizing radiation

    USDA-ARS?s Scientific Manuscript database

    This chapter gives a comprehensive review on ionizing irradiation of fresh fruits and vegetables. Topics include principles of ionizing radiation, its effects on pathogenic and spoilage microorganisms, shelf-life, sensory quality, nutritional and phytochemical composition, as well as physiologic and...

  6. The Electronic and Vibrational Energies of the High-Spin States of He2 Which Correspond Asymptotically to the Interaction of Two 1s2s 3S He Atoms.

    DTIC Science & Technology

    1986-06-01

    Scheaffer (GMS)2 treated these same three states in c~nnection with their study of Penning and associative ionization of 2 S atoms. GMS performed a...Helium Atoms," J. Chem. Phys., Vol. 50, p. 5151, 1969. ’V 2. Garrison, B.J., Miller. W.H.. and Scheaffer , H.F., "Penning and Associative Ionization of

  7. Non-ionizing energy loss calculations for modeling electron-induced degradation of Cu(In, Ga)Se2 thin-film solar cells

    NASA Astrophysics Data System (ADS)

    Lu, Ming; Xu, Jing; Huang, Jian-Wei

    2016-09-01

    The lowest energies which make Cu, In, Ga, and Se atoms composing Cu(In, Ga)Se2 (CIGS) material displaced from their lattice sites are evaluated, respectively. The non-ionizing energy loss (NIEL) for electron in CIGS material is calculated analytically using the Mott differential cross section. The relation of the introduction rate (k) of the recombination centers to NIEL is modified, then the values of k at different electron energies are calculated. Degradation modeling of CIGS thin-film solar cells irradiated with various-energy electrons is performed according to the characterization of solar cells and the recombination centers. The validity of the modeling approach is verified by comparison with the experimental data. Project supported by the National Natural Science Foundation of China (Grant No. 11547151).

  8. Two- and three-photon double ionization of lithium

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    Motivated by current FEL experiments at FLASH, we present triple differential cross sections and recoil ion momentum distributions for two- and three-photon double ionization of the 1s^22s ^2S ground state of lithium at a photon energy of 50 eV. The time-dependent close-coupling (TDCC) method is used to solve the two-electron time-dependent Schr"odinger equation in full dimensionality. The double ionization process is treated as a two-active-electron process, where the ``active'' 1s and 2s electrons move in the field of the ``frozen-core'' Li^2+ 1s state. Recent experimental measurements of recoil ion momentum distributions have observed features associated with the absorption of both two and three photons. This work provides the first TDCC calculations to date of such two- and three-photon double ionization processes in lithium. The accurate treatment of these processes requires a detailed description of the final continuum containing both singlet and triplet S, P, D and F waves. We examine triple differential cross sections as a function of electron energy sharing for a variety of angular configurations. We also compare our calculated recoil ion momentum distributions with experimental measurements, providing the first such comparison for two- and three-photon processes.

  9. Electron-impact ionization of H2O at low projectile energy: Internormalized triple-differential cross sections in three-dimensional kinematics

    NASA Astrophysics Data System (ADS)

    Ren, Xueguang; Amami, Sadek; Hossen, Khokon; Ali, Esam; Ning, ChuanGang; Colgan, James; Madison, Don; Dorn, Alexander

    2017-02-01

    We report a combined experimental and theoretical study of the electron-impact ionization of water (H2O ) at the relatively low incident energy of E0=81 eV in which either the 1 b1 or 3 a1 orbitals are ionized leading to the stable H2O+ cation. The experimental data were measured by using a reaction microscope, which can cover nearly the entire 4 π solid angle for the secondary electron emission over a range of ejection energies. We present experimental data for the scattering angles of 6∘ and 10∘ for the faster of the two outgoing electrons as a function of the detection angle of the secondary electron with energies of 5 and 10 eV. The experimental triple-differential cross sections are internormalized across the measured scattering angles and ejected energies. The experimental data are compared with predictions from two molecular three-body distorted-wave approaches: one applying the orientation-averaged molecular orbital (OAMO) approximation and one using a proper average (PA) over orientation-dependent cross sections. The PA calculations are in better agreement with the experimental data than the OAMO calculations for both the angular dependence and the relative magnitude of the observed cross-section structures.

  10. Ionization spectroscopies and theoretical calculations of cis and trans 3-fluoro-N-methylaniline-Arn(n = 1,2) van der Waals clusters: Structures and binding energies

    NASA Astrophysics Data System (ADS)

    Zhang, Lijuan; Li, Dazhi; Cheng, Min; Du, Yikui; Zhu, Qihe

    2017-08-01

    The ab initio and dispersion-corrected density functional theory (DFT) calculations of the van der Waals (vdW) clusters of cis and trans 3-fluoro-N-methylaniline-Arn (3FNMA-Arn) (n = 1,2) predict that, for cis and trans 3FNMA-Ar1 clusters, the π-bound geometry with the Ar atom sitting over the ring is the global minimum in both neutral and cationic states, while for cis and trans 3FNMA-Ar2 clusters, the [π | π]-bound sandwich structure with two Ar ligands occupying nearly equivalent π-bound positions above and below the ring plane is the global minimum. The vibronic spectra of cis and trans 3FNMA-Ar1 clusters in the S1 state were recorded by using one-color and two-color resonant two-photon ionization (R2PI) techniques, the comparison of which yields an estimate of the binding energy of cluster in the S1 state. It is found that the linear correlation between the redshift of the S1 ← S0 electronic transition energy (E1) of cluster and the E1 of the monomer also holds for the Ar clusters of hetero-di-substituted aromatics. By recording the photoionization efficiency (PIE) curves and mass-analyzed threshold ionization (MATI) dissociation spectra of cis and trans 3FNMA-Ar1 clusters, the ionization energies (IE) and binding energies of clusters in the D0 state are obtained. The MATI spectra of the cis and trans 3FNMA-Ar1 cations exhibit significant progressions of the vdW bending mode (bx), indicating the structural changes of the clusters in the bending coordinate upon ionization. The combination of the three kinds of spectroscopic methods provides the binding energies of cis and trans 3FNMA-Ar1 clusters in the S0, S1 and D0 states with good accuracy, and the values estimated by dispersion-corrected DFT calculations compare well with the experimental results. From our studies, the ωB97X-D and TD-ωB97X-D methods using high quality basis set are recommended for studying the intermolecular interaction of such vdW clusters in the ground and excited states.

  11. Ionization spectroscopies and theoretical calculations of cis and trans 3-fluoro-N-methylaniline-Arn(n=1,2) van der Waals clusters: Structures and binding energies.

    PubMed

    Zhang, Lijuan; Li, Dazhi; Cheng, Min; Du, Yikui; Zhu, Qihe

    2017-08-05

    The ab initio and dispersion-corrected density functional theory (DFT) calculations of the van der Waals (vdW) clusters of cis and trans 3-fluoro-N-methylaniline-Arn (3FNMA-Arn) (n=1,2) predict that, for cis and trans 3FNMA-Ar1 clusters, the π-bound geometry with the Ar atom sitting over the ring is the global minimum in both neutral and cationic states, while for cis and trans 3FNMA-Ar2 clusters, the [π|π]-bound sandwich structure with two Ar ligands occupying nearly equivalent π-bound positions above and below the ring plane is the global minimum. The vibronic spectra of cis and trans 3FNMA-Ar1 clusters in the S1 state were recorded by using one-color and two-color resonant two-photon ionization (R2PI) techniques, the comparison of which yields an estimate of the binding energy of cluster in the S1 state. It is found that the linear correlation between the redshift of the S1←S0 electronic transition energy (E1) of cluster and the E1 of the monomer also holds for the Ar clusters of hetero-di-substituted aromatics. By recording the photoionization efficiency (PIE) curves and mass-analyzed threshold ionization (MATI) dissociation spectra of cis and trans 3FNMA-Ar1 clusters, the ionization energies (IE) and binding energies of clusters in the D0 state are obtained. The MATI spectra of the cis and trans 3FNMA-Ar1 cations exhibit significant progressions of the vdW bending mode (bx), indicating the structural changes of the clusters in the bending coordinate upon ionization. The combination of the three kinds of spectroscopic methods provides the binding energies of cis and trans 3FNMA-Ar1 clusters in the S0, S1 and D0 states with good accuracy, and the values estimated by dispersion-corrected DFT calculations compare well with the experimental results. From our studies, the ωB97X-D and TD-ωB97X-D methods using high quality basis set are recommended for studying the intermolecular interaction of such vdW clusters in the ground and excited states. Copyright

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

    PubMed

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

    2015-06-11

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

  13. Preliminary Measurement of the K-Shell Ionization Cross Sections of Ti by Positron Impact in the Low Energy Region

    NASA Astrophysics Data System (ADS)

    Tian, Lixia; Liu, Mantian; Zhu, Jingjun; An, Zhu; Wang, Baoyi; Qin, Xiubo

    2012-05-01

    Measurements were performed of K-shell ionization cross sections of Ti element by 10~30 keV positron impact using the thick-target method. The effects of multiple scattering of incident positron and from bremsstrahlung photons and annihilation photons with the thick-target method are discussed with the Monte Carlo code PENELOPE. Meanwhile, the Monte Carlo method is also applied to determine the detection efficiencies of X- and γ-ray detectors. Our experimental K-shell ionization cross sections for Ti element are compared with the distorted-wave Born approximation (DWBA) theoretical predictions, and it is found that the agreement of the experimental data and theoretical values is good and this indicates that the experimental method adopted in this study is applicable.

  14. Excitational energy transfer enhancing ionization and spatial-temporal evolution of air breakdown with UV laser radiation

    SciTech Connect

    Hummelt, Jason S.; Scharer, John E.

    2010-11-15

    This paper examines the role multiphoton excitation of oxygen has on the ionization of nitrogen in laser air breakdown. Plasma is created by focusing a 193 nm ArF excimer laser using an 18 cm focal length lens, producing a cylindrical 540 {mu}m wide spot of intensity 6.5 GW/cm{sup 2}, well below the classical limit for collisional cascade (CC) breakdown. By spectroscopically monitoring the B {sup 2{Sigma}}{sub u}{sup +} to X {sup 2{Sigma}}{sub g}{sup +} transition at 391.4 nm of N{sub 2}{sup +} in N{sub 2} and O{sub 2} mixes, collisions between N{sub 2} and metastable O{sub 2} states that have undergone 1+1 absorption processes are shown to lower the degree of nonlinearity (i.e., the number of photons involved in the rate limiting multiphoton absorption process) in the ionization of N{sub 2}. This process is also found to dominate the 2+1 resonant enhanced multiphoton ionization of N{sub 2} in air and be the primary source for ionization of N{sub 2} to the B {sup 2{Sigma}}{sub u}{sup +} state. Plasma formation and evolution is also examined using a 1.3 cm focal length objective lens creating a 40 {mu}m wide spot of intensity 1.25 TW/cm{sup 2}, above the classical limit for breakdown. This plasma is imaged with a fast (1.2 ns) gating intensified charge coupled device camera. Early plasma formation is seen to be inhomogeneous in nature, and significant ion density is found to exist up to 20 {mu}s after the laser pulse.

  15. Internal energy effects on the solvation and reactivity of multiply charged biomolecules for electrospray ionization mass spectroscopy. [Bovine ubiquitin

    SciTech Connect

    Light-Wahl, K.J.; Winger, B.E.; Rockwood, A.L.; Smith, R.D.

    1992-06-01

    Mild (capillary) interface conditions which do not completely desolvate the ions of proteins in electrospray ionization mass spectrometry (ESI-MS) may be required to probe the higher order structures and weak associations. For the small protein bovine ubiquitin, two ion distributions (unsolvated ions and unresolved solvated ions) were observed. The resolvable solvation for leucine-enkephalin with methanol and water shows that the use of countercurrent N{sub 2} flow at the capillary affects the solvation observed. 2 figs. (DLC)

  16. Internal energy effects on the solvation and reactivity of multiply charged biomolecules for electrospray ionization mass spectroscopy

    SciTech Connect

    Light-Wahl, K.J.; Winger, B.E.; Rockwood, A.L.; Smith, R.D.

    1992-06-01

    Mild (capillary) interface conditions which do not completely desolvate the ions of proteins in electrospray ionization mass spectrometry (ESI-MS) may be required to probe the higher order structures and weak associations. For the small protein bovine ubiquitin, two ion distributions (unsolvated ions and unresolved solvated ions) were observed. The resolvable solvation for leucine-enkephalin with methanol and water shows that the use of countercurrent N{sub 2} flow at the capillary affects the solvation observed. 2 figs. (DLC)

  17. Determination of ionization energies of CnN (n=4-12): Vacuum-ultraviolet (VUV) photoionization experiments and theoretical calculations

    SciTech Connect

    Kostko, Oleg; Zhou, Jia; Sun, Bian Jian; Lie, Jie Shiuan; Chang, Agnes H.H.; Kaiser, Ralf I.; Ahmed, Musahid

    2010-06-10

    Results from single photon vacuum ultraviolet photoionization of astrophysically relevant CnN clusters, n = 4 - 12, in the photon energy range of 8.0 eV to 12.8 eV are presented. The experimental photoionization efficiency curves, combined with electronic structure calculations, provide improved ionization energies of the CnN species. A search through numerous nitrogen-terminated CnN isomers for n=4-9 indicates that the linear isomer has the lowest energy, and therefore should be the most abundant isomer in the molecular beam. Comparison with calculated results also shed light on the energetics of the linear CnN clusters, particularly in the trends of the even-carbon and the odd-carbon series. These results can help guide the search of potential astronomical observations of these neutral molecules together with their cations in highly ionized regions or regions with a high UV/VUV photon flux (ranging from the visible to VUV with flux maxima in the Lyman- region) in the interstellar medium.

  18. Determination of ionization energies of CnN (n=4-12): Vacuum-ultraviolet (VUV) photoionization experiments and theoretical calculations

    SciTech Connect

    Kostko, Oleg; Zhou, Jia; Sun, Bian Jian; Lie, Jie Shiuan; Chang, Agnes H.H.; Kaiser, Ralf I.; Ahmed, Musahid

    2010-03-02

    Results from single photon vacuum ultraviolet photoionization of astrophysically relevant CnN clusters, n = 4 - 12, in the photon energy range of 8.0 eV to 12.8 eV are presented. The experimental photoionization efficiency curves, combined with electronic structure calculations, provide improved ionization energies of the CnN species. A search through numerous nitrogen-terminated CnN isomers for n=4-9 indicates that the linear isomer has the lowest energy, and therefore should be the most abundant isomer in the molecular beam. Comparison with calculated results also shed light on the energetics of the linear CnN clusters, particularly in the trends of the even-carbon and the odd-carbon series. These results can help guide the search of potential astronomical observations of these neutral molecules together with their cations in highly ionized regions or regions with a high UV/VUV photon flux (ranging from the visible to VUV with flux maxima in the Lyman-a region) in the interstellar medium.

  19. Electron-impact-ionization cross sections of H{sub 2} for low outgoing electron energies from 1 to 10 eV

    SciTech Connect

    Al-Hagan, Ola; Madison, D. H.; Murray, A. J.; Kaiser, C.; Colgan, J.

    2010-03-15

    Theoretical and experimental fully differential cross sections are presented for electron-impact ionization of molecular hydrogen in a plane perpendicular to the incident beam direction. The experimental data exhibit a maximum for 1-eV electrons detected 180 deg. apart and a minimum for 10-eV electrons. We investigate the different physical effects which cause back-to-back scattering and demonstrate that, over the energy range from 10 to 1 eV, a direct transition is observed from a region where Wannier threshold physics is essentially unimportant to where it completely dominates.

  20. CORRECTION FACTORS FOR ATTENUATION AND SCATTERING OF THE WALL OF A CYLINDRICAL IONIZATION CHAMBER IN THE 6-7 MeV HIGH-ENERGY PHOTON REFERENCE FIELD.

    PubMed

    Kowatari, M; Zutz, H; Hupe, O

    2017-06-07

    In high-energy photon reference fields the value of the air kerma rate is determined by using ionization chambers (ICs). From the charge collected inside the IC the dose can be calculated using a set of calibration and correction factors according to ISO 4037-2. A crucial parameter is the correction for the attenuation and scattering of the primary radiation due to the chamber wall. This parameter can be determined using Monte Carlo calculations. The evaluation of the factor was performed for a commercially available IC of the type Victoreen 550-3 under different build-up conditions. The results were verified by measurements in the R-F high-energy photon fields according to ISO 4037-1 at the Physikalisch-Technische Bundesanstalt (PTB) and the Japan Atomic Energy Agency (JAEA). © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  1. High energy photon reference for radiation protection: technical design of the LINAC beam and ionization chambers; and calculation of monoenergetic conversion coefficients

    NASA Astrophysics Data System (ADS)

    Dusciac, D.; Bordy, J.-M.; Daures, J.; Blideanu, V.

    2016-09-01

    In this work, we present the results of the first part of a research project aimed at offering a complete response to dosimeters providers and nuclear physicists' demands for high-energy (6 - 9 MeV) photon beams for radiation protection purposes. Classical facilities allowing the production of high-energy photonic radiation (proton accelerators, nuclear reactors) are very rare and need large investment for development and use. A novel solution is proposed, consisting in the use of a medical linear accelerator, allowing a significant decrease of all costs.Using Monte Carlo simulations (MCNP5 and PENELOPE codes), a specifically designed electron-photon conversion target allowing for obtaining a high energy photon beam (with an average energy weighted by fluence of about 6 MeV) has been built for radiation protection purposes. Due to the specific design of the target, this "realistic" radiation protection high-energy photon beam presents a uniform distribution of air kerma rate at a distance of 1 m, over a 30 × 30 cm2 surface. Two graphite cavity ionizing chambers for ionometric measurements have been built. For one of these chambers, the charge collection volume has been measured allowing for its use as a primary standard. The second ionizing chamber is used as a transfer standard; as such it has been calibrated in a 60Co beam, and in the high energy photon beam for radiation protection.The measurements with these ionizing chambers allowed for an evaluation of the air kerma rate in the LINAC based high-energy photon beam for radiation protection: the values cover a range between 36 mGy/h and 210 mGy/h, compatible with radiation protection purposes.Finally, using Monte Carlo simulations, conversion coefficients from air kerma to dose equivalent quantities have been calculated in the range between 10 keV and 22.4 MeV, for the spectral distribution of the fluence corresponding to the beam produced by the linear accelerator of the LNE-LNHB.

  2. "Magic" Ionization Mass Spectrometry.

    PubMed

    Trimpin, Sarah

    2016-01-01

    The systematic study of the temperature and pressure dependence of matrix-assisted ionization (MAI) led us to the discovery of the seemingly impossible, initially explained by some reviewers as either sleight of hand or the misinterpretation by an overzealous young scientist of results reported many years before and having little utility. The “magic” that we were attempting to report was that with matrix assistance, molecules, at least as large as bovine serum albumin (66 kDa), are lifted into the gas phase as multiply charged ions simply by exposure of the matrix:analyte sample to the vacuum of a mass spectrometer. Applied heat, a laser, or voltages are not necessary to achieve charge states and ion abundances only previously observed with electrospray ionization (ESI). The fundamentals of how solid phase volatile or nonvolatile compounds are converted to gas-phase ions without added energy currently involves speculation providing a great opportunity to rethink mechanistic understanding of ionization processes used in mass spectrometry. Improved understanding of the mechanism(s) of these processes and their connection to ESI and matrix-assisted laser desorption/ionization may provide opportunities to further develop new ionization strategies for traditional and yet unforeseen applications of mass spectrometry. This Critical Insights article covers developments leading to the discovery of a seemingly magic ionization process that is simple to use, fast, sensitive, robust, and can be directly applied to surface characterization using portable or high performance mass spectrometers.

  3. "Magic" Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Trimpin, Sarah

    2016-01-01

    The systematic study of the temperature and pressure dependence of matrix-assisted ionization (MAI) led us to the discovery of the seemingly impossible, initially explained by some reviewers as either sleight of hand or the misinterpretation by an overzealous young scientist of results reported many years before and having little utility. The "magic" that we were attempting to report was that with matrix assistance, molecules, at least as large as bovine serum albumin (66 kDa), are lifted into the gas phase as multiply charged ions simply by exposure of the matrix:analyte sample to the vacuum of a mass spectrometer. Applied heat, a laser, or voltages are not necessary to achieve charge states and ion abundances only previously observed with electrospray ionization (ESI). The fundamentals of how solid phase volatile or nonvolatile compounds are converted to gas-phase ions without added energy currently involves speculation providing a great opportunity to rethink mechanistic understanding of ionization processes used in mass spectrometry. Improved understanding of the mechanism(s) of these processes and their connection to ESI and matrix-assisted laser desorption/ionization may provide opportunities to further develop new ionization strategies for traditional and yet unforeseen applications of mass spectrometry. This Critical Insights article covers developments leading to the discovery of a seemingly magic ionization process that is simple to use, fast, sensitive, robust, and can be directly applied to surface characterization using portable or high performance mass spectrometers.

  4. Amorphous silicon ionizing particle detectors

    DOEpatents

    Street, Robert A.; Mendez, Victor P.; Kaplan, Selig N.

    1988-01-01

    Amorphous silicon ionizing particle detectors having a hydrogenated amorphous silicon (a--Si:H) thin film deposited via plasma assisted chemical vapor deposition techniques are utilized to detect the presence, position and counting of high energy ionizing particles, such as electrons, x-rays, alpha particles, beta particles and gamma radiation.

  5. Amorphous silicon ionizing particle detectors

    DOEpatents

    Street, R.A.; Mendez, V.P.; Kaplan, S.N.

    1988-11-15

    Amorphous silicon ionizing particle detectors having a hydrogenated amorphous silicon (a--Si:H) thin film deposited via plasma assisted chemical vapor deposition techniques are utilized to detect the presence, position and counting of high energy ionizing particles, such as electrons, x-rays, alpha particles, beta particles and gamma radiation. 15 figs.

  6. Search for metastable heavy charged particles with large ionization energy loss in pp collisions at s=13TeV using the ATLAS experiment

    DOE PAGES

    Aaboud, M.; Aad, G.; Abbott, B.; ...

    2016-06-28

    This study presents a search for massive charged long-lived particles produced in pp collisions at √s = 13TeV at the LHC using the ATLAS experiment. The data set used corresponds to an integrated luminosity of 3.2 fb–1. Many extensions of the Standard Model predict the existence of massive charged long-lived particles, such as R-hadrons. These massive particles are expected to be produced with a velocity significantly below the speed of light, and therefore to have a specific ionization higher than any Standard Model particle of unit charge at high momenta. The Pixel subsystem of the ATLAS detector is used tomore » measure the ionization energy loss of reconstructed charged particles and to search for such highly ionizing particles. The search presented here has much greater sensitivity than a similar search performed using the ATLAS detector in the √s = 8TeV data set, thanks to the increase in expected signal cross section due to the higher center-of-mass energy of collisions, to an upgraded detector with a new silicon layer close to the interaction point, and to analysis improvements. No significant deviation from Standard Model background expectations is observed, and lifetime-dependent upper limits on R-hadron production cross sections and masses are set. Gluino R-hadrons with lifetimes above 0.4 ns and decaying to qq¯ plus a 100 GeV neutralino are excluded at the 95% confidence level, with lower mass limit ranging between 740 and 1590 GeV. In the case of stable R-hadrons the lower mass limit at the 95% confidence level is 1570 GeV.« less

  7. Search for metastable heavy charged particles with large ionization energy loss in p p collisions at √{s }=13 TeV using the ATLAS experiment

    NASA Astrophysics Data System (ADS)

    Aaboud, M.; Aad, G.; Abbott, B.; Abdallah, J.; Abdinov, O.; Abeloos, B.; Aben, R.; Abouzeid, O. S.; Abraham, N. L.; Abramowicz, H.; Abreu, H.; Abreu, R.; Abulaiti, Y.; Acharya, B. S.; Adamczyk, L.; Adams, D. L.; Adelman, J.; Adomeit, S.; Adye, T.; Affolder, A. A.; Agatonovic-Jovin, T.; Agricola, J.; Aguilar-Saavedra, J. A.; Ahlen, S. P.; Ahmadov, F.; Aielli, G.; Akerstedt, H.; Åkesson, T. P. A.; Akimov, A. V.; Alberghi, G. L.; Albert, J.; Albrand, S.; Alconada Verzini, M. J.; Aleksa, M.; Aleksandrov, I. N.; Alexa, C.; Alexander, G.; Alexopoulos, T.; Alhroob, M.; Aliev, M.; Alimonti, G.; Alison, J.; Alkire, S. P.; Allbrooke, B. M. M.; Allen, B. W.; Allport, P. P.; Aloisio, A.; Alonso, A.; Alonso, F.; Alpigiani, C.; Alstaty, M.; Alvarez Gonzalez, B.; Álvarez Piqueras, D.; Alviggi, M. G.; Amadio, B. T.; Amako, K.; Amaral Coutinho, Y.; Amelung, C.; Amidei, D.; Amor Dos Santos, S. P.; Amorim, A.; Amoroso, S.; Amundsen, G.; Anastopoulos, C.; Ancu, L. S.; Andari, N.; Andeen, T.; Anders, C. F.; Anders, G.; Anders, J. K.; Anderson, K. J.; Andreazza, A.; Andrei, V.; Angelidakis, S.; Angelozzi, I.; Anger, P.; Angerami, A.; Anghinolfi, F.; Anisenkov, A. V.; Anjos, N.; Annovi, A.; Antonelli, M.; Antonov, A.; Anulli, F.; Aoki, M.; Aperio Bella, L.; Arabidze, G.; Arai, Y.; Araque, J. P.; Arce, A. T. H.; Arduh, F. A.; Arguin, J.-F.; Argyropoulos, S.; Arik, M.; Armbruster, A. J.; Armitage, L. J.; Arnaez, O.; Arnold, H.; Arratia, M.; Arslan, O.; Artamonov, A.; Artoni, G.; Artz, S.; Asai, S.; Asbah, N.; Ashkenazi, A.; Åsman, B.; Asquith, L.; Assamagan, K.; Astalos, R.; Atkinson, M.; Atlay, N. B.; Augsten, K.; Avolio, G.; Axen, B.; Ayoub, M. K.; Azuelos, G.; Baak, M. A.; Baas, A. E.; Baca, M. J.; Bachacou, H.; Bachas, K.; Backes, M.; Backhaus, M.; Bagiacchi, P.; Bagnaia, P.; Bai, Y.; Baines, J. T.; Baker, O. K.; Baldin, E. M.; Balek, P.; Balestri, T.; Balli, F.; Balunas, W. K.; Banas, E.; Banerjee, Sw.; Bannoura, A. A. E.; Barak, L.; Barberio, E. L.; Barberis, D.; Barbero, M.; Barillari, T.; Barklow, T.; Barlow, N.; Barnes, S. L.; Barnett, B. M.; Barnett, R. M.; Barnovska, Z.; Baroncelli, A.; Barone, G.; Barr, A. J.; Barranco Navarro, L.; Barreiro, F.; Barreiro Guimarães da Costa, J.; Bartoldus, R.; Barton, A. E.; Bartos, P.; Basalaev, A.; Bassalat, A.; Bates, R. L.; Batista, S. J.; Batley, J. R.; Battaglia, M.; Bauce, M.; Bauer, F.; Bawa, H. S.; Beacham, J. B.; Beattie, M. D.; Beau, T.; Beauchemin, P. H.; Bechtle, P.; Beck, H. P.; Becker, K.; Becker, M.; Beckingham, M.; Becot, C.; Beddall, A. J.; Beddall, A.; Bednyakov, V. A.; Bedognetti, M.; Bee, C. P.; Beemster, L. J.; Beermann, T. A.; Begel, M.; Behr, J. K.; Belanger-Champagne, C.; Bell, A. S.; Bella, G.; Bellagamba, L.; Bellerive, A.; Bellomo, M.; Belotskiy, K.; Beltramello, O.; Belyaev, N. L.; Benary, O.; Benchekroun, D.; Bender, M.; Bendtz, K.; Benekos, N.; Benhammou, Y.; Benhar Noccioli, E.; Benitez, J.; Benjamin, D. P.; Bensinger, J. R.; Bentvelsen, S.; Beresford, L.; Beretta, M.; Berge, D.; Bergeaas Kuutmann, E.; Berger, N.; Beringer, J.; Berlendis, S.; Bernard, N. R.; Bernius, C.; Bernlochner, F. U.; Berry, T.; Berta, P.; Bertella, C.; Bertoli, G.; Bertolucci, F.; Bertram, I. A.; Bertsche, C.; Bertsche, D.; Besjes, G. J.; Bessidskaia Bylund, O.; Bessner, M.; Besson, N.; Betancourt, C.; Bethke, S.; Bevan, A. J.; Bhimji, W.; Bianchi, R. M.; Bianchini, L.; Bianco, M.; Biebel, O.; Biedermann, D.; Bielski, R.; Biesuz, N. V.; Biglietti, M.; Bilbao de Mendizabal, J.; Bilokon, H.; Bindi, M.; Binet, S.; Bingul, A.; Bini, C.; Biondi, S.; Bjergaard, D. M.; Black, C. W.; Black, J. E.; Black, K. M.; Blackburn, D.; Blair, R. E.; Blanchard, J.-B.; Blanco, J. E.; Blazek, T.; Bloch, I.; Blocker, C.; Blum, W.; Blumenschein, U.; Blunier, S.; Bobbink, G. J.; Bobrovnikov, V. S.; Bocchetta, S. S.; Bocci, A.; Bock, C.; Boehler, M.; Boerner, D.; Bogaerts, J. A.; Bogavac, D.; Bogdanchikov, A. G.; Bohm, C.; Boisvert, V.; Bokan, P.; Bold, T.; Boldyrev, A. S.; Bomben, M.; Bona, M.; Boonekamp, M.; Borisov, A.; Borissov, G.; Bortfeldt, J.; Bortoletto, D.; Bortolotto, V.; Bos, K.; Boscherini, D.; Bosman, M.; Bossio Sola, J. D.; Boudreau, J.; Bouffard, J.; Bouhova-Thacker, E. V.; Boumediene, D.; Bourdarios, C.; Boutle, S. K.; Boveia, A.; Boyd, J.; Boyko, I. R.; Bracinik, J.; Brandt, A.; Brandt, G.; Brandt, O.; Bratzler, U.; Brau, B.; Brau, J. E.; Braun, H. M.; Breaden Madden, W. D.; Brendlinger, K.; Brennan, A. J.; Brenner, L.; Brenner, R.; Bressler, S.; Bristow, T. M.; Britton, D.; Britzger, D.; Brochu, F. M.; Brock, I.; Brock, R.; Brooijmans, G.; Brooks, T.; Brooks, W. K.; Brosamer, J.; Brost, E.; Broughton, J. H.; Bruckman de Renstrom, P. A.; Bruncko, D.; Bruneliere, R.; Bruni, A.; Bruni, G.; Brunt, Bh; Bruschi, M.; Bruscino, N.; Bryant, P.

    2016-06-01

    This paper presents a search for massive charged long-lived particles produced in p p collisions at √{s }=13 TeV at the LHC using the ATLAS experiment. The data set used corresponds to an integrated luminosity of 3.2 fb-1. Many extensions of the Standard Model predict the existence of massive charged long-lived particles, such as R -hadrons. These massive particles are expected to be produced with a velocity significantly below the speed of light, and therefore to have a specific ionization higher than any Standard Model particle of unit charge at high momenta. The Pixel subsystem of the ATLAS detector is used to measure the ionization energy loss of reconstructed charged particles and to search for such highly ionizing particles. The search presented here has much greater sensitivity than a similar search performed using the ATLAS detector in the √{s }=8 TeV data set, thanks to the increase in expected signal cross section due to the higher center-of-mass energy of collisions, to an upgraded detector with a new silicon layer close to the interaction point, and to analysis improvements. No significant deviation from Standard Model background expectations is observed, and lifetime-dependent upper limits on R -hadron production cross sections and masses are set. Gluino R -hadrons with lifetimes above 0.4 ns and decaying to q q ¯ plus a 100 GeV neutralino are excluded at the 95% confidence level, with lower mass limit ranging between 740 and 1590 GeV. In the case of stable R -hadrons the lower mass limit at the 95% confidence level is 1570 GeV.

  8. Comparison of the Internal Energy Deposition of Venturi-Assisted Electrospray Ionization and a Venturi-Assisted Array of Micromachined UltraSonic Electrosprays (AMUSE)

    PubMed Central

    Hampton, Christina Y.; Silvestri, Catherine J.; Forbes, Thomas P.; Varady, Mark J.; Meacham, J. Mark; Fedorov, Andrei G.; Degertekin, F. Levent; Fernández, Facundo M.

    2008-01-01

    The internal energy deposition of a Venturi-assisted array of micromachined ultrasonic electrosprays (AMUSE), with and without the application of a DC charging potential, is compared with equivalent experiments for Venturi-assisted electrospray ionization (ESI) using the “survival yield” method on a series of para-substituted benzylpyridinium salts. Under conditions previously shown to provide maximum ion yields for standard compounds, the observed mean internal energies were nearly identical (1.93–2.01eV). Operation of AMUSE without nitrogen flow to sustain the air amplifier focusing effect generated energetically-colder ions with mean internal energies that were up to 39% lower than those for ESI. A balance between improved ion transfer, adequate desolvation and favorable ion energetics was achieved by selection of optimum operational ranges for the parameters that most strongly influence the ion population, namely the air amplifier gas flow rate and API capillary temperature. Examination of the energy landscapes obtained for combinations of these parameters showed that a low internal energy region (≤ 1.0 eV) was present at nitrogen flow rates between 2 – 4 L min−1 and capillary temperatures up to 250°C using ESI (9% of all parameter combinations tested). Using AMUSE, this region was present at nitrogen flow rates up to 2.5 L min−1 and all capillary temperatures (13% of combinations tested). The signal-to-noise ratio (S/N) of the intact p-methylbenzylpyridinium ion obtained from a 5 μM mixture of thermometer compounds using AMUSE at the extremes of the studied temperature range was at least 5 times higher than that of ESI demonstrating the potential of AMUSE ionization as a soft method for the characterization of labile species by mass spectrometry. PMID:18650100

  9. Comparison of the internal energy deposition of Venturi-assisted electrospray ionization and a Venturi-assisted array of micromachined ultrasonic electrosprays (AMUSE).

    PubMed

    Hampton, Christina Y; Silvestri, Catherine J; Forbes, Thomas P; Varady, Mark J; Meacham, J Mark; Fedorov, Andrei G; Degertekin, F Levent; Fernández, Facundo M

    2008-09-01

    The internal energy deposition of a Venturi-assisted array of micromachined ultrasonic electrosprays (AMUSE), with and without the application of a DC charging potential, is compared with equivalent experiments for Venturi-assisted electrospray ionization (ESI) using the "survival yield" method on a series of para-substituted benzylpyridinium salts. Under conditions previously shown to provide maximum ion yields for standard compounds, the observed mean internal energies were nearly identical (1.93-2.01 eV). Operation of AMUSE without nitrogen flow to sustain the air amplifier focusing effect generated energetically colder ions with mean internal energies that were up to 39% lower than those for ESI. A balance between improved ion transfer, adequate desolvation, and favorable ion energetics was achieved by selection of optimum operational ranges for the parameters that most strongly influence the ion population: the air amplifier gas flow rate and API capillary temperature. Examination of the energy landscapes obtained for combinations of these parameters showed that a low internal energy region (ionization as a soft method for the characterization of labile species by mass spectrometry.

  10. Plasma Production via Field Ionization

    SciTech Connect

    O'Connell, C.L.; Barnes, C.D.; Decker, F.; Hogan, M.J.; Iverson, R.; Krejcik, P.; Siemann, R.; Walz, D.R.; Clayton, C.E.; Huang, C.; Johnson, D.K.; Joshi, C.; Lu, W.; Marsh, K.A.; Mori, W.; Zhou, M.; Deng, S.; Katsouleas, T.; Muggli, P.; Oz, E.; /Southern California U.

    2007-01-02

    Plasma production via field ionization occurs when an incoming particle beam is sufficiently dense that the electric field associated with the beam ionizes a neutral vapor or gas. Experiments conducted at the Stanford Linear Accelerator Center explore the threshold conditions necessary to induce field ionization by an electron beam in a neutral lithium vapor. By independently varying the transverse beam size, number of electrons per bunch or bunch length, the radial component of the electric field is controlled to be above or below the threshold for field ionization. Additional experiments ionized neutral xenon and neutral nitric oxide by varying the incoming beam's bunch length. A self-ionized plasma is an essential step for the viability of plasma-based accelerators for future high-energy experiments.

  11. Absolute dose measurements by means of a small cylindrical ionization chamber for very high dose per pulse high energy electron beams

    SciTech Connect

    Karaj, E.; Righi, S.; Di Martino, F.

    2007-03-15

    Very high dose per pulse (3-13 cGy/pulse) high energy electron beams are currently produced by special linear accelerators (linac) dedicated to Intra Operative Radiation Therapy (IORT). The electron beams produced by such linacs are collimated by special Perspex applicators of various size and cylindrically shaped. The biggest problems from the dosimetric point of view are caused by the high dose-per-pulse values and the use of inclined applicators. In this work measurements of absolute dose for the inclined applicators were done by using a small cylindrical ionization chamber, type CC01 (Wellhofer), a parallel plane ionization chamber type Markus (PTW 23343) and radiochromic films type EBT. We show a method which allows calculating the quality correction factors for CC01 chamber with an uncertainty of 1% and the absolute dose value for the inclined applicators using CC01 with an uncertainty of 3.1% for electron beams of energy of 6 and 7 MeV produced by the linac dedicated to IORT Novac7.

  12. A first-principle protocol for calculating ionization energies and redox potentials of solvated molecules and ions: Theory and application to aqueous phenol and phenolate

    PubMed Central

    Ghosh, Debashree; Roy, Anirban; Seidel, Robert; Winter, Bernd; Bradforth, Stephen; Krylov, Anna I.

    2012-01-01

    The effect of hydration on the lowest vertical ionization energy (VIE) of phenol and phenolate solvated in bulk water was characterized using the equation-of-motion ionization potential coupled-cluster (EOM-IP-CCSD) and effective fragment potential (EFP) methods (referred to as EOM/EFP), and determined experimentally by valence photo-emission measurements using microjets and synchrotron radiation. The computed solvent-induced shifts in VIEs (ΔVIE) are −0.66 eV and +5.72 eV for phenol and phenolate, respectively. Our best estimates of the absolute values of VIEs (7.9 and 7.7 eV for phenol and phenolate) agree reasonably well with the respective experimental values (7.8±0.1 eV and 7.1±0.1 eV). The EOM/EFP scheme was benchmarked against full EOM-IP-CCSD using micro-solvated phenol and phenolate clusters. A protocol for calculating redox potentials with EOM/EFP was developed based on linear response approximation (LRA) of free energy determination. The oxidation potentials of phenol and phenolate calculated using LRA and EOM/EFP are 1.32 V and 0.89 V, respectively; they agree well with experimental values. PMID:22497288

  13. Ionization energies, proton affinities, and pKa values of a large series of edaravone derivatives: implication for their free radical scavenging activity.

    PubMed

    Pérez-González, Adriana; Galano, Annia

    2011-09-01

    The electron-donating capability (EDC) and the ease of deprotonation (ED) of 26 edaravone derivatives have been evaluated. Their first ionization energies have been used to assess their EDC. Four different approaches to obtain vertical ionization energies were tested, using a set of structurally related compounds. Those based on the electron propagator theory (EPT) were identified as the best ones. In particular, the partial third order (P3) approximation led to the lowest mean unsigned error (MUE = 0.10 eV). Two descriptors were used to evaluate ED: the proton affinity (PA) and the pK(a). It was found that pK(a) values are better descriptors than PA values. Ideal candidates to perform as efficiently as, or even better than, edaravone itself are proposed. The recommendations were based on the simultaneous analyses of EDC and ED, and they should be particularly valid when the electron transfer mechanism plays an important role in the antioxidant activity of the studied compounds. © 2011 American Chemical Society

  14. A comparative study on carbon, boron-nitride, boron-phosphide and silicon-carbide nanotubes based on surface electrostatic potentials and average local ionization energies.

    PubMed

    Esrafili, Mehdi D; Behzadi, Hadi

    2013-06-01

    A density functional theory study was carried out to predict the electrostatic potentials as well as average local ionization energies on both the outer and the inner surfaces of carbon, boron-nitride (BN), boron-phosphide (BP) and silicon-carbide (SiC) single-walled nanotubes. For each nanotube, the effect of tube radius on the surface potentials and calculated average local ionization energies was investigated. It is found that SiC and BN nanotubes have much stronger and more variable surface potentials than do carbon and BP nanotubes. For the SiC, BN and BP nanotubes, there are characteristic patterns of positive and negative sites on the outer lateral surfaces. On the other hand, a general feature of all of the systems studied is that stronger potentials are associated with regions of higher curvature. According to the evaluated surface electrostatic potentials, it is concluded that, for the narrowest tubes, the water solubility of BN tubes is slightly greater than that of SiC followed by carbon and BP nanotubes.

  15. Precision Measurement of the Ionization Energy of the GK ^1Σ_g^+ (v=1,N=1) State of Molecular Hydrogen.

    NASA Astrophysics Data System (ADS)

    Beyer, M.; Sprecher, D.; Merkt, F.

    2013-06-01

    The ionization energy of the GK ^1Σ_g^+ (v=1,N=1) state of ortho H_2 has been determined at a precision of 1.2 MHz by near-infrared laser spectroscopy. The measurement was performed by first exciting molecular hydrogen from the X ^1Σ_g^+ (v=0,N=1) state to the GK ^1Σ_g^+ (v=1,N=1) state in a resonant two-photon process via the B ^1Σ_u^+ (v=3,N=2) state and then measuring the frequency of the transition between the GK ^1Σ_g^+ (v=1,N=1) state and the 56p (S=0,N=1) Rydberg state belonging to the series converging on the X^+ ^2Σ_g^+ (v^+=0,N^+=1) ground state of ortho H_2^+. The ionization energy of the GK ^1Σ_g^+ (v=1,N=1) state was obtained by adding this frequency to the binding energy of the 56p (S=0,N=1) Rydberg state which has been determined previously by millimeter-wave spectroscopy and multichannel quantum-defect theory. For the measurement we used a homebuilt pulsed NIR laser with Fourier-transform-limited linewidth and adjustable pulse duration. To reach the desired accuracy, systematic errors originating from ac and dc Stark shifts, from pressure shifts, and from the frequency shifts and chirps accompanying the generation of the NIR laser pulses were quantified. The ionization energy of the GK ^1Σ_g^+ (v=1,N=1) state will be compared with earlier results. New attempts of measuring the binding energy of the EF ^1Σ_g^+ state will also be mentioned. A. Osterwalder, A. Wüest, F. Merkt and Ch. Jungen, {J. Chem. Phys.} 121 (23), 11810 (2004). D. Sprecher, Ch. Jungen, W. Ubachs and F. Merkt, {Faraday Discuss.} 150, 51 (2011). Ch. Jungen, I. Dabrowski, G. Herzberg and M. Vervloet, {J. Chem. Phys.} 93 (4), 2289 (1990). D. Bailly, E. J. Salumbides, M. Vervloet and W. Ubachs, {Mol. Phys.} 108 (7-9), 827 (2010).

  16. The C 1s and N 1s near edge x-ray absorption fine structure spectra of five azabenzenes in the gas phase

    SciTech Connect

    Vall-llosera, G.; Gao, B.; Kivimaeki, A.; Coreno, M.; Alvarez Ruiz, J.; Simone, M. de; Aagren, H.; Rachlew, E.

    2008-01-28

    Near edge x-ray absorption fine structure spectra have been measured and interpreted by means of density functional theory for five different azabenzenes (pyridine, pyridazine, pyrimidine, pyrazine, and s-triazine) in the gas phase. The experimental and theoretical spectra at the N 1s and C 1s edges show a strong resonance assigned to the transition of the 1s electron in the respective N or C atoms to the lowest unoccupied molecular orbital with {pi}* symmetry. As opposed to the N 1s edge, at the C 1s edge this resonance is split due to the different environments of the core hole atom in the molecule. The shift in atomic core-level energy due to a specific chemical environment is explained with the higher electronegativity of the N atom compared to the C atom. The remaining resonances below the ionization potential (IP) are associated to {sigma} or {pi} orbitals with mixed valence/Rydberg character. Upon N addition, a reduction of intensity is observed in the Rydberg region at both edges as compared to the intensity in the continuum. Above the IP one or more resonances are seen and ascribed here to transitions to {sigma}* orbitals. Calculating the experimental and theoretical {delta}{sub {pi}} term values at both edges, we observe that they are almost the same within {+-}1 eV as expected for isoelectronic bonded pairs. The term values of the {pi}* and {sigma}* resonances are discussed in terms of the total Z number of the atoms participating in the bond.

  17. Electron transfer, excitation, and ionization in {alpha}-H collisions studied with a Sturmian basis

    SciTech Connect

    Winter, Thomas G.

    2007-12-15

    Cross sections have been determined for electron transfer, direct excitation, and ionization in collisions between {alpha} particles and H(1s) atoms at {alpha} energies 3 keV-38.4 MeV, extending earlier work [Phys. Rev. A 25, 697 (1982)] restricted to total transfer at 20-200 keV. Transfer as well as excitation cross sections into individual states up to 3d have been determined with several coupled-Sturmian pseudostate bases, and tests of basis sensitivity have been carried out. These and ionization cross sections have been compared with existing experimental and other coupled-state results. Structure is observed in the lower-energy excitation cross sections, which is believed not to be an artifact of the bases used. Ionization and excitation cross sections have also been compared with corresponding Born results at higher energies.

  18. IONIZATION CHAMBER

    DOEpatents

    Redman, W.C.; Shonka, F.R.

    1958-02-18

    This patent describes a novel ionization chamber which is well suited to measuring the radioactivity of the various portions of a wire as the wire is moved at a uniform speed, in order to produce the neutron flux traverse pattern of a reactor in which the wire was previously exposed to neutron radiation. The ionization chamber of the present invention is characterized by the construction wherein the wire is passed through a tubular, straight electrode and radiation shielding material is disposed along the wire except at an intermediate, narrow area where the second electrode of the chamber is located.

  19. Photoelectron angular distributions from two-photon ionizations of atoms

    NASA Astrophysics Data System (ADS)

    Haber, Louis Hamilton

    Photoelectron angular distributions provide detailed information about interferences between different quantum pathways of photoionization. Measurements of photoelectron energies and angular distributions from two-color two-photon ionizations of atoms using ultrashort pulses of extreme ultraviolet and optical light are performed using a novel, homebuilt experimental instrument. The setup is composed of an amplified femtosecond laser system, a high-order harmonic generation source, and an interaction region with photoelectron velocity map imaging The experimental temporal resolution is determined to be approximately 100 fs. Two different types of two-photon ionizations are investigated. Photoelectron angular distributions from resonant two-photon ionizations of helium are measured using the 15th high-order harmonic to excite from the ground state to either the 1s3p 1P1 state at 23.1 eV or to the 1s4p 1 P1 state at 23.7 eV and either 800, 400, or 267 nm to ionize. The anisotropy parameters allow for the determination of the energy-dependent ratios of radial dipole matrix elements and the phase shift differences between the S and D partial waves. Using available total cross section measurements, the absolute partial cross sections of the 1s3p1P 1 state are obtained, providing the complete information on photoionization. The experimental results are in excellent agreement with theoretical predictions using the one-electron model. Additional experiments are aimed at studying atomic free-free transitions. Two-color two-photon above threshold ionizations of helium and argon are investigated using selected high-order harmonics and perturbative infrared dressing fields. The measured anisotropy parameters and cross section ratios of the positive and negative above threshold ionization sidebands are compared to theoretical predictions using second-order perturbation theory and the soft-photon approximation. In general, deviations between the experimental results and the

  20. Angular momentum reorientation in CO(A 1Π)-He rotational energy transfer studied by optical-optical double resonance multiphoton ionization spectroscopy

    NASA Astrophysics Data System (ADS)

    Sha, Guohe; Sun, Weizhong; Jiang, Bo; Hintsa, Eric; Zhang, Cunhao

    1993-06-01

    An optical-optical double resonance multiphoton ionization (OODR-MPI) technique has been developed for measuring the angular momentum reorientation in CO(A 1Π)-He inelastic thermal collisions. In this scheme, two-photon pumping of CO(A 1Π) by using a circularly polarized laser creates a highly anisotropic oriented angular momentum distribution in CO(A 1Π). A second counterpropagating circularly polarized laser probes the oriented CO(A 1Π) via 1+1 photon resonance ionization. A depolarization factor (D), which can be calculated from the measured intensity ratios between R and P branches in the OODR-MPI spectrum, is introduced to characterize the amount of collisional reorientation in the J→J' rotational energy transfer (RET). This method has the advantage of both high sensitivity and simplicity in data processing. The experimental results show the propensities that the depolarization factor D increases with ΔJ but decreases with increasing initial J. The D's are asymmetric with respect to ±ΔJ. For comparison, theoretical D's have been computed by an irreducible tensor formalism under the infinite-order-sudden approximation by Alexander and Davis [J. Chem. Phys. 78, 6754 (1983)] which is further simplified by using an exponential energy gap term to represent the dynamic effects. The computed curves of D vs ΔJ/J reproduce the experimental propensities. The best fit between theory and experiment is obtained with an average impact parameter b=2.9 Å, corresponding to a cross section of 26.4 Å2, which is close to the experimental total cross section of CO(A 1Π)-He rotational energy transfer (˜28 Å2).

  1. SU-D-19A-01: Can Farmer-Type Ionization Chambers Be Used to Improve the Accuracy of Low-Energy Electron Beam Reference Dosimetry?

    SciTech Connect

    Muir, B R; McEwen, M R

    2014-06-01

    Purpose: To investigate the use of cylindrical Farmer-type ionization chambers to improve the accuracy of low-energy electron beam calibration. Historically, these chamber types have not been used in beams with incident energies less than 10 MeV (R{sub 5} {sub 0} < 4.3 cm) because early investigations suggested large (up to 5 %) fluence perturbation factors in these beams, implying that a significant component of uncertainty would be introduced if used for calibration. More recently, the assumptions used to determine perturbation corrections for cylindrical chambers have been questioned. Methods: Measurements are made with cylindrical chambers in Elekta Precise 4, 8 and 18 MeV electron beams. Several chamber types are investigated that employ graphite walls and aluminum electrodes with very similar specifications (NE2571, NE2505/3, FC65-G). Depth-ionization scans are measured in water in the 8 and 18 MeV beams. To reduce uncertainty from chamber positioning, measurements in the 4 MeV beam are made at the reference depth in Virtual Water™. The variability of perturbation factors is quantified by comparing normalized response of various chambers. Results: Normalized ion chamber response varies by less than 0.7 % for similar chambers at average electron energies corresponding to that at the reference depth from 4 or 6 MeV beams. Similarly, normalized measurements made with similar chambers at the reference depth in the 4 MeV beam vary by less than 0.4 %. Absorbed dose calibration coefficients derived from these results are stable within 0.1 % on average over a period of 6 years. Conclusion: These results indicate that the uncertainty associated with differences in fluence perturbations for cylindrical chambers with similar specifications is only 0.2 %. The excellent long-term stability of these chambers in both photon and electron beams suggests that these chambers might offer the best performance for all reference dosimetry applications.

  2. [Cytogenetic damage to the corneal epithelium of mice due to the in vivo exposure to ionizing radiation with different levels of linear energy transfer].

    PubMed

    Vorozhtsova, S V; Bulynina, T M; Molokanov, A G; Ivanov, A A

    2015-01-01

    Damages to corneal epithelium cells were studied in mice irradiated by protons with the energies of 10, 25, 50 and 645 MeV, 60Co γ-quanta and accelerated ions of boron, carbon and neon with the energies of 7.5; 2.5 and 6.0 MeV/nucleon, respectively. X-rays (180 keV) were used as a standard radiation. Animals were exposed to a single dose in the range from 25 to 760 cGy. The mitotic index and aberrant mitoses were counted in corneal preparations in 24 hrs after irradiation. No matter the type of radiation, the mitotic index had an inverse dose dependence, i.e. the higher the dose, the lower the mitotic index. Exposure to all types of radiation resulted in a sharp increase in the number of chromosomal aberrations in the corneal epithelium; frequency of aberrations was a function of dose and type of radiation. The number of chromosomal aberrations displayed a peculiar direct dose dependence irrespective of type of radiation; however, heavy ions of carbon and boron are the most damaging to the cytogenetic apparatus of epithelial cells. Protons at the Bragg peak and ensuing fall, and of 50 MeV also contribute to the production of chromosomal aberrations as compared with sparsely ionizing gamma- and X-rays and high-energy protons with low linear energy transfer. Coefficients of relative biological effectiveness were calculated based on the mitotic index and evidence of aberrant mitosis.

  3. Energy deficit of pulsed-laser field-ionized and field-emitted ions from non-metallic nano-tips

    SciTech Connect

    Arnoldi, L.; Silaeva, E. P.; Gaillard, A.; Vurpillot, F.; Blum, I.; Rigutti, L.; Deconihout, B.; Vella, A.

    2014-05-28

    The energy deficit of pulsed-laser field-evaporated ions and field-ionized atoms of an inert gas from the surface of a non-metallic nano-metric tip is reported as a function of the laser intensity, ion current, and temperature. A new model is proposed to explain these results, taking into account the resistive properties of non-metallic nano-tips. A good agreement between the theoretical predictions and the experimental results is obtained for all parameters investigated experimentally. This model is also used to discuss the evaporation behavior of oxides analyzed in laser-assisted atom probe tomography. New insight into the contribution of the electrostatic field and the laser illumination on the evaporation process of non-metallic materials is given.

  4. Comprehensive metabolite profiling of Plantaginis Semen using ultra high performance liquid chromatography with electrospray ionization quadrupole time-of-flight tandem mass spectrometry coupled with elevated energy technique.

    PubMed

    Wang, Dandan; Qi, Meng; Yang, Qiming; Tong, Renchao; Wang, Rui; Bligh, S W Annie; Yang, Li; Wang, Zhengtao

    2016-05-01

    Plantaginis Semen is commonly used in traditional medicine to treat edema, hypertension, and diabetes. The commercially available Plantaginis Semen in China mainly comes from three species. To clarify the chemical composition and distinct different species of Plantaginis Semen, we established a metabolite profiling method based on ultra high performance liquid chromatography with electrospray ionization quadrupole time-of-flight tandem mass spectrometry coupled with elevated energy technique. A total of 108 compounds, including phenylethanoid glycosides, flavonoids, guanidine derivatives, terpenoids, organic acids, and fatty acids, were identified from Plantago asiatica L., P. depressa Willd., and P. major L. Results showed significant differences in chemical components among the three species, particularly flavonoids. This study is the first to provide a comprehensive chemical profile of Plantaginis Semen, which could be involved into the quality control, medication guide, and developing new drug of Plantago seeds. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. New insights into the mechanism underlying the synergistic action of ionizing radiation with platinum chemotherapeutic drugs: the role of low-energy electrons.

    PubMed

    Rezaee, Mohammad; Hunting, Darel John; Sanche, Léon

    2013-11-15

    To investigate the efficiencies of platinum chemotherapeutic drugs (Pt-drugs) in the sensitization of DNA to the direct effects of ionizing radiation and to determine the role of low-energy electrons (LEEs) in this process. Complexes of supercoiled plasmid DNA covalently bound to either cisplatin, carboplatin, or oxaliplatin were prepared in different molar ratios. Solid films of DNA and DNA modified by Pt-drugs were irradiated with either 10-KeV or 10-eV electrons. Damages to DNA were quantified by gel electrophoresis, and the yields for damage formation were obtained from exposure-response curves. The presence of an average of 2 Pt-drug-DNA adducts (Pt-adducts) in 3199-bp plasmid DNA increases the probability of a double-strand break by factors of 3.1, 2.5, and 2.4 for carboplatin, cisplatin, and oxaliplatin, respectively. Electrons with energies of 10 eV and 10 KeV interact with Pt-adducts to preferentially enhance the formation of cluster lesions. The maximum increase in radiosensitivity per Pt-adduct is found at ratios up to 3.1×10(-4) Pt-adducts per nucleotide, which is equivalent to an average of 2 adducts per plasmid. Carboplatin and oxaliplatin show higher efficiencies than cisplatin in the radiosensitization of DNA. Because carboplatin and cisplatin give rise to identical reactive species that attach to DNA, carboplatin must be considered as a better radiosensitizer for equal numbers of Pt-adducts. Platinum chemotherapeutic drugs preferentially enhance the formation of cluster damage to DNA induced by the direct effect of ionizing radiation, and LEEs are the main species responsible for such an enhancement via the formation of electron resonances. Copyright © 2013 Elsevier Inc. All rights reserved.

  6. New Insights into the Mechanism Underlying the Synergistic Action of Ionizing Radiation With Platinum Chemotherapeutic Drugs: The Role of Low-Energy Electrons

    SciTech Connect

    Rezaee, Mohammad Hunting, Darel John; Sanche, Léon

    2013-11-15

    Purpose: To investigate the efficiencies of platinum chemotherapeutic drugs (Pt-drugs) in the sensitization of DNA to the direct effects of ionizing radiation and to determine the role of low-energy electrons (LEEs) in this process. Methods and Materials: Complexes of supercoiled plasmid DNA covalently bound to either cisplatin, carboplatin, or oxaliplatin were prepared in different molar ratios. Solid films of DNA and DNA modified by Pt-drugs were irradiated with either 10-KeV or 10-eV electrons. Damages to DNA were quantified by gel electrophoresis, and the yields for damage formation were obtained from exposure–response curves. Results: The presence of an average of 2 Pt-drug–DNA adducts (Pt-adducts) in 3199-bp plasmid DNA increases the probability of a double-strand break by factors of 3.1, 2.5, and 2.4 for carboplatin, cisplatin, and oxaliplatin, respectively. Electrons with energies of 10 eV and 10 KeV interact with Pt-adducts to preferentially enhance the formation of cluster lesions. The maximum increase in radiosensitivity per Pt-adduct is found at ratios up to 3.1 × 10{sup −4} Pt-adducts per nucleotide, which is equivalent to an average of 2 adducts per plasmid. Carboplatin and oxaliplatin show higher efficiencies than cisplatin in the radiosensitization of DNA. Because carboplatin and cisplatin give rise to identical reactive species that attach to DNA, carboplatin must be considered as a better radiosensitizer for equal numbers of Pt-adducts. Conclusion: Platinum chemotherapeutic drugs preferentially enhance the formation of cluster damage to DNA induced by the direct effect of ionizing radiation, and LEEs are the main species responsible for such an enhancement via the formation of electron resonances.

  7. Fast analysis of high-energy compounds and agricultural chemicals in water with desorption electrospray ionization mass spectrometry.

    PubMed

    Mulligan, Christopher C; MacMillan, Denise K; Noll, Robert J; Cooks, R Graham

    2007-01-01

    Novel sampling and detection methods using desorption electrospray ionization (DESI) are examined in the detection of explosives (RDX, TNT, HMX, and TNB) and agricultural chemicals (atrazine, alachlor and acetochlor) from aqueous matrices and authentic contaminated groundwater samples. DESI allows analysis of solid and liquid compounds directly from surfaces of interest with little or no sample preparation. Significant savings in analysis time and sample preparation are realized. The methods investigated here include (i) immediate analysis of filter paper wetted with contaminated water samples without further sample preparation, (ii) rapid liquid-liquid extraction (LLE), and (iii) analyte extraction from contaminated groundwater samples on-site using solid-phase extraction (SPE) membranes, followed by direct DESI analysis of the membrane. The wetted filter paper experiment demonstrates the maximum sample throughput for DESI analysis of aqueous matrices but has inadequate sensitivity for some of these analytes. Both the LLE and the SPE methods have adequate sensitivity. The resulting SPE membranes and/or small volume solvent extracts produced in these experiments are readily transported to off-site facilities for direct analysis by DESI. This realizes a significant reduction in the costs of sample shipping compared with those for typical liter-sized samples of groundwater. Total analysis times for these preliminary DESI analyses are comparable with or shorter than those for GC/MS and limits of detection approach environmental action levels for these compounds while maintaining a modest relative standard deviation. Tandem mass spectrometric data is used to provide additional specificity as needed.

  8. VUV and soft x-ray ionization of a plant volatile: Vanillin (C8H8O3).

    PubMed

    Betancourt, A Moreno; Coutinho, L H; Bernini, R B; de Moura, C E V; Rocha, A B; de Souza, G G B

    2016-03-21

    Plant volatiles are emitted by plants in response to several forms of stress, including interaction with energetic photons. In the present work, we discuss the interaction of extreme UV and soft X-ray photons with a plant volatile, vanillin. The single and double (multiple) ionization of the vanillin molecule have been studied for the first time using time-of-flight mass spectrometry and VUV and soft X-ray photons (synchrotron radiation, at 12.0 eV, 21.2 eV, 130 eV, 310 eV, 531 eV, and 550 eV). At 12.0 and 21.2 eV, only singly charged species are observed and the parent ion, C8H8O3 (+), is the dominant species. Energy differences for some selected fragments were calculated theoretically in this energy region. At 130 eV, direct double and triple ionization of the valence electrons may occur. The fragmentation increases and CHO(+) becomes one of the main cations in the mass spectrum. The molecular ion is still the dominant species, but other fragments, such as C6H5O(+), begin to present similar intensities. At 310 eV, C 1s electrons may be ionized and Auger processes give rise to dissociative doubly ionized cations. Ionization around the O 1s edge has been studied both at the 531 eV resonance and above the ionization edge. Resonant and normal Auger processes play a significant role in each case and a large fragmentation of the molecule is observed at both photon energies, with intense fragments such as CHO(+) and CH3 (+) being clearly observed. A near edge X-ray absorption fine structure spectrum of the vanillin molecule was obtained around the O 1s ionization threshold. In addition, the fragmentation of vanillin has also been studied using a fast beam of electrons (800 eV), for the sake of comparison.

  9. VUV and soft x-ray ionization of a plant volatile: Vanillin (C8H8O3)

    NASA Astrophysics Data System (ADS)

    Betancourt, A. Moreno; Coutinho, L. H.; Bernini, R. B.; de Moura, C. E. V.; Rocha, A. B.; de Souza, G. G. B.

    2016-03-01

    Plant volatiles are emitted by plants in response to several forms of stress, including interaction with energetic photons. In the present work, we discuss the interaction of extreme UV and soft X-ray photons with a plant volatile, vanillin. The single and double (multiple) ionization of the vanillin molecule have been studied for the first time using time-of-flight mass spectrometry and VUV and soft X-ray photons (synchrotron radiation, at 12.0 eV, 21.2 eV, 130 eV, 310 eV, 531 eV, and 550 eV). At 12.0 and 21.2 eV, only singly charged species are observed and the parent ion, C8H8O3+, is the dominant species. Energy differences for some selected fragments were calculated theoretically in this energy region. At 130 eV, direct double and triple ionization of the valence electrons may occur. The fragmentation increases and CHO+ becomes one of the main cations in the mass spectrum. The molecular ion is still the dominant species, but other fragments, such as C6H5O+, begin to present similar intensities. At 310 eV, C 1s electrons may be ionized and Auger processes give rise to dissociative doubly ionized cations. Ionization around the O 1s edge has been studied both at the 531 eV resonance and above the ionization edge. Resonant and normal Auger processes play a significant role in each case and a large fragmentation of the molecule is observed at both photon energies, with intense fragments such as CHO+ and CH3+ being clearly observed. A near edge X-ray absorption fine structure spectrum of the vanillin molecule was obtained around the O 1s ionization threshold. In addition, the fragmentation of vanillin has also been studied using a fast beam of electrons (800 eV), for the sake of comparison.

  10. Gridded electron reversal ionizer

    NASA Technical Reports Server (NTRS)

    Chutjian, Ara (Inventor)

    1993-01-01

    A gridded electron reversal ionizer forms a three dimensional cloud of zero or near-zero energy electrons in a cavity within a filament structure surrounding a central electrode having holes through which the sample gas, at reduced pressure, enters an elongated reversal volume. The resultant negative ion stream is applied to a mass analyzer. The reduced electron and ion space-charge limitations of this configuration enhances detection sensitivity for material to be detected by electron attachment, such as narcotic and explosive vapors. Positive ions may be generated by generating electrons having a higher energy, sufficient to ionize the target gas and pulsing the grid negative to stop the electron flow and pulsing the extraction aperture positive to draw out the positive ions.

  11. Gadolinium (Gd) Oxide, Carbide, and Carbonyl Cation Bond Energies and Evaluation of the Gd + O → GdO(+) + e(-) Chemi-Ionization Reaction Enthalpy.

    PubMed

    Demireva, Maria; Kim, JungSoo; Armentrout, P B

    2016-11-03

    Guided ion beam mass spectrometry (GIBMS) is used to measure the kinetic energy dependent product ion cross sections for reactions of the lanthanide metal gadolinium cation (Gd(+)) with O2, CO2, and CO and for reactions of GdO(+) with CO, O2, and Xe. GdO(+) is formed through barrierless and exothermic processes in the reactions of Gd(+) with O2 and CO2. All other reactions observed are endothermic, and analyses of their kinetic energy dependent cross sections yield 0 K bond dissociation energies (BDEs) for GdO(+), GdC(+), and GdCO(+). The 0 K BDE for GdO(+) is determined from five different reactions to be 7.69 ± 0.10 eV, and this value is combined with literature data to derive the ionization energy (IE) of GdO as 5.82 ± 0.16 eV. Additionally, GdC(+) and GdCO(+) BDEs of 3.18 ± 0.18 eV and 0.65 ± 0.06 eV are obtained from analysis of the Gd(+) reactions with CO and CO2, respectively. Theoretical GdO(+), GdC(+), and GdCO(+) BDEs are calculated for comparison with experiment using various Gd basis sets with an effective core potential and several levels of theory. For calculations that correctly predict a (10)D ground state for Gd(+), good agreement between theoretical and measured GdC(+) and GdCO(+) BDEs is obtained, whereas the GdO(+) BDE is underestimated in these calculations by about 0.8 eV. Additional BDEs for GdO(+) and GdC(+) are calculated using triple- and quadruple-ζ correlation consistent all-electron basis sets for Gd. Calculations with these basis sets provide better agreement with experiment for GdO(+) but not for GdC(+). The measured Gd(+) oxide, carbide, and carbonyl BDEs are similar to those for the group 3 metal ions, Sc(+) and Y(+). This is attributed to similarities in the ground state electronic configurations of these metal ions leading to similar interaction strengths. The experimental GdO(+) BDE measured here combined with the known IE of Gd is used to determine an exothermicity of 1.54 ± 0.10 eV for the Gd chemi-ionization reaction

  12. WE-EF-207-11: Energy and Depth Response of Thermoluminescent Dosimeters and Ionization Chambers in Water for Kilovoltage X-Ray Beams

    SciTech Connect

    Lawless, M; Palmer, B; DeWerd, L

    2015-06-15

    Purpose: To assess the effects of changes in beam quality on detector response in the kilovoltage energy range by modulating the x-ray tube voltage and the measurement depth in water. Methods: Measurements were performed with TLD-100 and TLD-100H thermoluminescent dosimeters and an A12 farmer-type ionization chamber. To assess the energy response of the detectors, irradiations were performed at a depth of 3 cm in a custom-built thin-window water phantom using the moderately filtered x-ray beams at the UWADCL (20 kVp-250 kVp) and a Co-60 beam.The x-ray beams and detectors were modeled using the EGSnrc Monte Carlo code. The model was validated by simulating dose to the collecting volume of an A12 farmer chamber and comparing it with measured A12 signal as a function of depth. Dose was tallied to each detector and to water for comparison with measurements. Simulations were used to calculate the predicted energy response, which was compared to the measured response of each detector. Dose to each detector and dose to water as a function of depth were also simulated. Results: Detector output per dose to water was found to deviate by up to 15%, 20% and 30% as a function of energy relative to Co-60 for the A12, TLD-100H and TLD-100, respectively. The EGSnrc simulations produced results similar to the measurements for ionization chambers, but discrepancies of up to 30% were observed for TLD-100H. Simulated detector response as a function of depth was found to vary by up to 3%. Conclusion: These results suggest that changes in beam quality in kilovoltage x-ray beams can have a significant impact on detector response. In-water detector response was found to differ from the previously investigated in-air response. Deviations in detector response as a function of depth were less significant, but could potentially cause dosimetric errors if ignored.

  13. NR2 and P3+: Accurate, Efficient Electron-Propagator Methods for Calculating Valence, Vertical Ionization Energies of Closed-Shell Molecules.

    PubMed

    Corzo, H H; Galano, Annia; Dolgounitcheva, O; Zakrzewski, V G; Ortiz, J V

    2015-08-20

    Two accurate and computationally efficient electron-propagator (EP) methods for calculating the valence, vertical ionization energies (VIEs) of closed-shell molecules have been identified through comparisons with related approximations. VIEs of a representative set of closed-shell molecules were calculated with EP methods using 10 basis sets. The most easily executed method, the diagonal, second-order (D2) EP approximation, produces results that steadily rise as basis sets are improved toward values based on extrapolated coupled-cluster singles and doubles plus perturbative triples calculations, but its mean errors remain unacceptably large. The outer valence Green function, partial third-order and renormalized partial third-order methods (P3+), which employ the diagonal self-energy approximation, produce markedly better results but have a greater tendency to overestimate VIEs with larger basis sets. The best combination of accuracy and efficiency with a diagonal self-energy matrix is the P3+ approximation, which exhibits the best trends with respect to basis-set saturation. Several renormalized methods with more flexible nondiagonal self-energies also have been examined: the two-particle, one-hole Tamm-Dancoff approximation (2ph-TDA), the third-order algebraic diagrammatic construction or ADC(3), the renormalized third-order (3+) method, and the nondiagonal second-order renormalized (NR2) approximation. Like D2, 2ph-TDA produces steady improvements with basis set augmentation, but its average errors are too large. Errors obtained with 3+ and ADC(3) are smaller on average than those of 2ph-TDA. These methods also have a greater tendency to overestimate VIEs with larger basis sets. The smallest average errors occur for the NR2 approximation; these errors decrease steadily with basis augmentations. As basis sets approach saturation, NR2 becomes the most accurate and efficient method with a nondiagonal self-energy.

  14. Initial results of positron ionization mass spectrometry

    NASA Technical Reports Server (NTRS)

    Donohue, D. L.; Hulett, L. D., Jr.; Mcluckey, S. A.; Glish, G. L.; Eckenrode, B. A.

    1990-01-01

    The use of monoenergetic positrons for the ionization of organic molecules in the gas phase is described. The ionic products are analyzed with a time-of-flight mass spectrometer and detected to produce a mass spectrum. The ionization mechanisms which can be studied in this way include positron impact at energies above the ionization limit of the target molecules, positronium formation in the Ore gap energy range, and positron attachment at energies less than 1eV. The technique of positron ionization mass spectrometry (PIMS) may have analytical utility in that chemical selectivity is observed for one or more of these processes.

  15. Inner-shell ionization of lithium-like chromium ions

    SciTech Connect

    Vogel, D.A.; Beiersdorfer, P.; Marrs, R.E.; Wong, K.L.; Zasadzinski, R.

    1990-09-07

    We have used high-resolution x-ray spectroscopy to investigate inner-shell ionization of Cr{sup 21+} ions by electron impact using the Electron Beam Ion Trap at Lawrence Livermore Laboratory. Our measurements indicate that inner-shell ionization enhances the intensity of the radiative transition 1s2s {sup 3}S{sub 1}{yields}1s{sup 2}{sup 1}S{sub 0}. 7 refs., 4 figs., 1 tab.

  16. A G/NARRLI Effort. Measuring the Ionization Yield of Low-Energy Nuclear Recoils in Liquid Argon

    SciTech Connect

    Joshi, Tenzing Henry Yatish

    2014-01-01

    Liquid argon has long been used for particle detection due to its attractive drift properties, ample abundance, and reasonable density. The response of liquid argon to lowenergy O(102 -1044 eV) interactions is, however, largely unexplored. Weakly interacting massive particles such as neutrinos and hypothetical dark-matter particles (WIMPs) are predicted to coherently scatter on atomic nuclei, leaving only an isolated low-energy nuclear recoil as evidence. The response of liquid argon to low-energy nuclear recoils must be studied to determine the sensitivity of liquid argon based detectors to these unobserved interactions. Detectors sensitive to coherent neutrino-nucleus scattering may be used to monitor nuclear reactors from a distance, to detect neutrinos from supernova, and to test the predicted behavior of neutrinos. Additionally, direct detection of hypothetical weakly interacting dark matter would be a large step toward understanding the substance that accounts for nearly 27% of the universe. In this dissertation I discuss a small dual-phase (liquid-gas) argon proportional scintillation counter built to study the low-energy regime and several novel calibration and characterization techniques developed to study the response of liquid argon to low-energy O(102 -104 eV) interactions.

  17. Measurement of low energy ionization signals from Compton scattering in a charge-coupled device dark matter detector

    NASA Astrophysics Data System (ADS)

    Ramanathan, K.; Kavner, A.; Chavarria, A. E.; Privitera, P.; Amidei, D.; Chou, T.-L.; Matalon, A.; Thomas, R.; Estrada, J.; Tiffenberg, J.; Molina, J.

    2017-08-01

    An important source of background in direct searches for low-mass dark matter particles are the energy deposits by small-angle scattering of environmental γ rays. We report detailed measurements of low-energy spectra from Compton scattering of γ rays in the bulk silicon of a charge-coupled device (CCD). Electron recoils produced by γ rays from 57Co and 241Am radioactive sources are measured between 60 eV and 4 keV. The observed spectra agree qualitatively with theoretical predictions, and characteristic spectral features associated with the atomic structure of the silicon target are accurately measured for the first time. A theoretically motivated parametrization of the data that describes the Compton spectrum at low energies for any incident γ -ray flux is derived. The result is directly applicable to background estimations for low-mass dark matter direct-detection experiments based on silicon detectors, in particular for the DAMIC experiment down to its current energy threshold.

  18. The effect of pi-stacking, h-bonding, and electrostatic interactions on the ionization energies of nucleic acid bases: adenine-adenine, thymine-thymine and adenine-thymine dimers

    SciTech Connect

    Bravaya, Ksenia B.; Kostko, Oleg; Ahmed, Musahid; Krylov, Anna I.

    2009-09-02

    A combined theoretical and experimental study of the ionized dimers of thymine and adenine, TT, AA, and AT, is presented. Adiabatic and vertical ionization energies(IEs) for monomers and dimers as well as thresholds for the appearance of the protonated species are reported and analyzed. Non-covalent interactions stronglyaffect the observed IEs. The magnitude and the nature of the effect is different for different isomers of the dimers. The computations reveal that for TT, the largestchanges in vertical IEs (0.4 eV) occur in asymmetric h-bonded and symmetric pi- stacked isomers, whereas in the lowest-energy symmetric h-bonded dimer the shiftin IEs is much smaller (0.1 eV). The origin of the shift and the character of the ionized states is different in asymmetric h-bonded and symmetric stacked isomers. Inthe former, the initial hole is localized on one of the fragments, and the shift is due to the electrostatic stabilization of the positive charge of the ionized fragment by thedipole moment of the neutral fragment. In the latter, the hole is delocalized, and the change in IE is proportional to the overlap of the fragments' MOs. The shifts in AAare much smaller due to a less effcient overlap and a smaller dipole moment. The ionization of the h-bonded dimers results in barrierless (or nearly barrierless) protontransfer, whereas the pi-stacked dimers relax to structures with the hole stabilized by the delocalization or electrostatic interactions.

  19. Energy calculation of 2s2 1S, 2p2 1D, 3s2 1S, 3p2 1D, 3d2 1G, 4p2 1D, 4d2 1D, 4f2 1I doubly excited states using a new wave function to four terms for 2 ≤ Z ≤ 15

    NASA Astrophysics Data System (ADS)

    Sow, B.; Sow, M.; Gning, Y.; Traore, A.; Ndao, A. S.; Wague, A.

    2016-06-01

    Calculation of the energy levels of atoms and ions with 2 ≤ Z ≤ 15 are carried out in this paper using a Hyllerass approximation. The method used is one of Screen Constant by Nuclear Charge Unit to calculate the total energy of two-electron atomic systems in ground and different doubly excited states. Employing a new wave function including correlation, we were able to calculate excited states (nl)2 (n ≤ 4). The Comparison of these results with the ones of other methods shows a good agreement.

  20. Zero kinetic energy spectroscopy: mass-analyzed threshold ionization spectra of chromium sandwich complexes with alkylbenzenes, (η(6)-RPh)(2)Cr (R = Me, Et, i-Pr, t-Bu).

    PubMed

    Ketkov, Sergey Y; Selzle, Heinrich L; Cloke, F Geoffrey N; Markin, Gennady V; Shevelev, Yury A; Domrachev, Georgy A; Schlag, Edward W

    2010-10-28

    For over 25 years zero kinetic energy (ZEKE) spectroscopy has yielded a rich foundation of high-resolution results of molecular ions. This was based on the discovery in the late 60's of long-lived ion states throughout the ionization continuum of molecular ions. Here, an example is chosen from another fundamental system pioneered at this university. The mass-analyzed threshold ionization (MATI) spectra of jet-cooled chromium bisarene complexes (η(6)-RPh)(2)Cr (R = Me (1), Et (2), i-Pr (3), and t-Bu (4)) have been measured and interpreted on the basis of DFT calculations. The MATI spectra of complexes 1 and 2 appear to reveal features arising from ionizations of the isomers formed by the rotation of one arene ring relative to the other. The 1 and 2 MATI spectra show two intense peaks corresponding to the 0(0)(0) ionizations with inverse intensity ratios. As indicated by the DFT calculations, the intensity ratio change on going from 1 to 2 results from different isomers contributing to each MATI peak. The ionization energies corresponding to the 0(0)(0) peaks are 42746 ± 5 and 42809 ± 5 cm(-1) for compound 1 and 42379 ± 5 and 42463 ± 5 cm(-1) for complex 2. The 1 and 2 spectra show also the weaker features representing transitions to the vibrationally excited cationic levels, the signals of individual rotamers being detected and assigned on the basis of calculated vibrational frequencies. The MATI spectra of compounds 3 and 4 reveal only one strong peak because of close ionization potentials of the isomers contributing to the MATI signal. The 3 and 4 ionization energies are 42104 ± 5 and 41917 ± 5 cm(-1), respectively. The precise values of ionization energies obtained from the MATI spectra reveal a nonlinear dependence of the IE on the number of Me groups in the alkyl substituents of (η(6)-RPh)(2)Cr. This can be explained by an increase in the molecular zero point energies on methylation of the substituents.

  1. Resonance ionization for analytical spectroscopy

    DOEpatents

    Hurst, George S.; Payne, Marvin G.; Wagner, Edward B.

    1976-01-01

    This invention relates to a method for the sensitive and selective analysis of an atomic or molecular component of a gas. According to this method, the desired neutral component is ionized by one or more resonance photon absorptions, and the resultant ions are measured in a sensitive counter. Numerous energy pathways are described for accomplishing the ionization including the use of one or two tunable pulsed dye lasers.

  2. Influence of renormalization shielding on the electron-impact ionization process in dense partially ionized plasmas

    SciTech Connect

    Song, Mi-Young; Yoon, Jung-Sik; Jung, Young-Dae

    2015-04-15

    The renormalization shielding effects on the electron-impact ionization of hydrogen atom are investigated in dense partially ionized plasmas. The effective projectile-target interaction Hamiltonian and the semiclassical trajectory method are employed to obtain the transition amplitude as well as the ionization probability as functions of the impact parameter, the collision energy, and the renormalization parameter. It is found that the renormalization shielding effect suppresses the transition amplitude for the electron-impact ionization process in dense partially ionized plasmas. It is also found that the renormalization effect suppresses the differential ionization cross section in the peak impact parameter region. In addition, it is found that the influence of renormalization shielding on the ionization cross section decreases with an increase of the relative collision energy. The variations of the renormalization shielding effects on the electron-impact ionization cross section are also discussed.

  3. Correlation of Hydrogen-Atom Abstraction Reaction Efficiencies for Aryl Radicals with their Vertical Electron Affinities and the Vertical Ionization Energies of the Hydrogen Atom Donors

    PubMed Central

    Jing, Linhong; Nash, John J.

    2009-01-01

    The factors that control the reactivities of aryl radicals toward hydrogen-atom donors were studied by using a dual-cell Fourier-transform ion cyclotron resonance mass spectrometer (FT – ICR). Hydrogen-atom abstraction reaction efficiencies for two substrates, cyclohexane and isopropanol, were measured for twenty-three structurally different, positively-charged aryl radicals, which included dehydrobenzenes, dehydronaphthalenes, dehydropyridines, and dehydro(iso)quinolines. A logarithmic correlation was found between the hydrogen-atom abstraction reaction efficiencies and the (calculated) vertical electron affinities (EA) of the aryl radicals. Transition state energies calculated for three of the aryl radicals with isopropanol were found to correlate linearly with their (calculated) EAs. No correlation was found between the hydrogen-atom abstraction reaction efficiencies and the (calculated) enthalpy changes for the reactions. Measurement of the reaction efficiencies for the reactions of several different hydrogen-atom donors with a few selected aryl radicals revealed a logarithmic correlation between the hydrogen-atom abstraction reaction efficiencies and the vertical ionization energies (IE) of the hydrogen-atom donors, but not the lowest homolytic X – H (X = heavy atom) bond dissociation energies of the hydrogen-atom donors. Examination of the hydrogen-atom abstraction reactions of twenty-nine different aryl radicals and eighteen different hydrogen-atom donors showed that the reaction efficiency increases (logarithmically) as the difference between the IE of the hydrogen-atom donor and the EA of the aryl radical decreases. This dependence is likely to result from the increasing polarization, and concomitant stabilization, of the transition state as the energy difference between the neutral and ionic reactants decreases. Thus, the hydrogen-atom abstraction reaction efficiency for an aryl radical can be “tuned” by structural changes that influence either

  4. A coupled cluster theory with iterative inclusion of triple excitations and associated equation of motion formulation for excitation energy and ionization potential

    NASA Astrophysics Data System (ADS)

    Maitra, Rahul; Akinaga, Yoshinobu; Nakajima, Takahito

    2017-08-01

    A single reference coupled cluster theory that is capable of including the effect of connected triple excitations has been developed and implemented. This is achieved by regrouping the terms appearing in perturbation theory and parametrizing through two different sets of exponential operators: while one of the exponentials, involving general substitution operators, annihilates the ground state but has a non-vanishing effect when it acts on the excited determinant, the other is the regular single and double excitation operator in the sense of conventional coupled cluster theory, which acts on the Hartree-Fock ground state. The two sets of operators are solved as coupled non-linear equations in an iterative manner without significant increase in computational cost than the conventional coupled cluster theory with singles and doubles excitations. A number of physically motivated and computationally advantageous sufficiency conditions are invoked to arrive at the working equations and have been applied to determine the ground state energies of a number of small prototypical systems having weak multi-reference character. With the knowledge of the correlated ground state, we have reconstructed the triple excitation operator and have performed equation of motion with coupled cluster singles, doubles, and triples to obtain the ionization potential and excitation energies of these molecules as well. Our results suggest that this is quite a reasonable scheme to capture the effect of connected triple excitations as long as the ground state remains weakly multi-reference.

  5. Ionization of He, Ne, Ar, Kr, and Xe by proton impact: Single differential distributions in energy and angles

    NASA Astrophysics Data System (ADS)

    Miraglia, J. E.

    2009-02-01

    In this paper we report energy and angular distributions of electrons emitted in collisions of protons with neon-(F-,Ne0,Na+) , argon-(Cl-,Ar0,K+) , krypton-(Br-,Kr0,Rb+) , and xenon-(I-,Xe0) isoelectronic series for high and intermediate impact energies. Calculations were performed within the continuum distorted wave-eikonal initial-state method using an angular expansion in spherical harmonics and a numerical evaluation of the radial functions corresponding to both: the initial (bound) and the final (continuum) states in the same central potential. The first Born approximation was calculated on equal footing. The shellwise local plasma approximation was also calculated when possible. A complete and exhaustive comparison with the available experimental data is carried out. We have spanned almost all the published experiments in our range of interest. Successes and failures of the different theoretical methods are pointed out. Possible signatures of many-electron effects are noticed.

  6. Stepwise hydration of ionized aromatics. Energies, structures of the hydrated benzene cation, and the mechanism of deprotonation reactions.

    PubMed

    Ibrahim, Yehia M; Meot-Ner Mautner, Michael; Alshraeh, Edreese H; El-Shall, M Samy; Scheiner, Steve

    2005-05-18

    The stepwise binding energies (DeltaHdegree(n-1,n)) of 1-8 water molecules to benzene(.+) [Bz(.+)(H2O)n] were determined by equilibrium measurements using an ion mobility cell. The stepwise hydration energies, DeltaHdegree(n-1,n), are nearly constant at 8.5 +/- 1 kcal mol-1 from n = 1-6. Calculations show that in the n = 1-4 clusters, the benzene(.+) ion retains over 90% of the charge, and it is extremely solvated, that is, hydrogen bonded to an (H2O)n cluster. The binding energies and entropies are larger in the n = 7 and 8 clusters, suggesting cyclic or cage-like water structures. The concentration of the n = 3 cluster is always small, suggesting that deprotonation depletes this ion, consistent with the thermochemistry since associative deprotonation Bz(.+)(H2O)(n-1) + H2O-->C6H5. + (H2O)nH+ is thermoneutral or exothermic for n > or = 4. Associative intracluster proton transfer Bz(.+)(H2O)(n+1) + H2O-->C6H5.(H2O)nH+ would also be exothermic for n > or = 4, but lack of H/D exchange with D2O shows that the proton remains on C6H6(.+) in the observed Bz(.+)(H2O)n clusters. This suggests a barrier to intracluster proton transfer, and as a result, the [Bz(.+)(H2O)n]* activated complexes either undergo dissociative proton transfer, resulting in deprotonation and generation of (H2O)nH+, or become stabilized. The rate constant for the deprotonation reaction shows a uniquely large negative temperature coefficient of K = cT(-67+/-4) (or activation energy of -34+/- 1 kcal mol-1), caused by a multibody mechanism in which five or more components need to be assembled for the reaction.

  7. Fluorescence resonance energy transfer (FRET) indicates that association with the type I ryanodine receptor (RyR1) causes reorientation of multiple cytoplasmic domains of the dihydropyridine receptor (DHPR) α(1S) subunit.

    PubMed

    Polster, Alexander; Ohrtman, Joshua D; Beam, Kurt G; Papadopoulos, Symeon

    2012-11-30

    The skeletal muscle dihydropyridine receptor (DHPR) in the t-tubular membrane serves as the Ca(2+) channel and voltage sensor for excitation-contraction (EC) coupling, triggering Ca(2+) release via the type 1 ryanodine receptor (RyR1) in the sarcoplasmic reticulum (SR). The two proteins appear to be physically linked, and both the α(1S) and β(1a) subunits of the DHPR are essential for EC coupling. Within α(1S), cytoplasmic domains of importance include the I-II loop (to which β(1a) binds), the II-III and III-IV loops, and the C terminus. However, the spatial relationship of these domains to one another has not been established. Here, we have taken the approach of measuring FRET between fluorescent proteins inserted into pairs of α(1S) cytoplasmic domains. Expression of these constructs in dyspedic (RyR1 null) and dysgenic (α(1S) null) myotubes was used to test for function and targeting to plasma membrane/SR junctions and to test whether the presence of RyR1 caused altered FRET. We found that in the absence of RyR1, measureable FRET occurred between the N terminus and C terminus (residue 1636), and between the II-III loop (residue 626) and both the N and C termini; the I-II loop (residue 406) showed weak FRET with the II-III loop but not with the N terminus. Association with RyR1 caused II-III loop FRET to decrease with the C terminus and increase with the N terminus and caused I-II loop FRET to increase with both the II-III loop and N terminus. Overall, RyR1 appears to cause a substantial reorientation of the cytoplasmic α(1S) domains consistent with their becoming more closely packed.

  8. Measurement of the muonium 1S-2S transition frequency

    SciTech Connect

    Jungmann, K.; Baird, P.E.G.; Barr, J.R.M.; Berkeland, D.; Boshier, M.G.; Braun, B.; Eaton, G.H.; Ferguson, A.I.; Geerds, H.; Hughes, V.W.; Maas, F.; Matthias, B.E.; Matousek, P.; Persaud, M.; zu Putlitz, G.; Reinhard, I.; Riis, E.; Sandars, P.G.H.; Schwarz, W.; Toner, W.T.; Towrie, M.; Willmann, L.; Woodle, K.A.; Woodman, G.

    1995-04-01

    Resonant ionization spectroscopy has been employed for measuring the 1{sup 2}{ital S}{sub 1/2}{minus}2{sup 2}{ital S}{sub 1/2} frequency difference in the hydrogen-like muonium atom to 2 455 529 002(33)(46) MHz. The 1S-2S two-photon transition was induced Doppler-free using two counter-propagating laser beams. The 2S state was photo-ionized by a third photon from the same laser field. The measurement agrees with QED theory within two standard deviations. The mass of the positive muon can be extracted from the isotope shifts in this transition to hydrogen and deuterium to 105.658 80(29)(43) MeV/c{sup 2}. {copyright} 1995 {ital American} {ital Institute} {ital of} {ital Physics}

  9. Measurement of the muonium 1S-2S transition frequency

    SciTech Connect

    Jungmann, K.; Baird, P. E. G.; Barr, J. R. M.; Berkeland, D.; Boshier, M. G.; Braun, B.; Eaton, G. H.; Ferguson, A. I.; Geerds, H.; Hughes, V. W.; Maas, F.; Matthias, B. E.; Matousek, P.; Persaud, M.; Putlitz, G. zu; Reinhard, I.; Riis, E.; Sandars, P. G. H.; Schwarz, W.; Toner, W. T.

    1995-04-01

    Resonant ionization spectroscopy has been employed for measuring the 1{sup 2}S1/2-2{sup 2}S1/2 frequency difference in the hydrogen-like muonium atom to 2 455 529 002(33)(46) MHz. The 1S-2S two-photon transition was induced Doppler-free using two counter-propagating laser beams. The 2S state was photo-ionized by a third photon from the same laser field. The measurement agrees with QED theory within two standard deviations. The mass of the positive muon can be extracted from the isotope shifts in this transition to hydrogen and deuterium to 105.658 80(29)(43) MeV/c{sup 2}.

  10. Two-Source Double-Slit Interference in Angle-Resolved High-Energy Above-Threshold Ionization Spectra of Diatoms

    SciTech Connect

    Okunishi, M.; Itaya, R.; Shimada, K.; Pruemper, G.; Ueda, K.; Busuladzic, M.; Gazibegovic-Busuladzic, A.; Milosevic, D. B.; Becker, W.

    2009-07-24

    When an electron from a diatomic molecule undergoes tunneling-rescattering ionization, a novel form of destructive interference can be realized that involves all four geometric orbits that are available to the electron when it is freed, because both ionization and rescattering may take place at the same or at different centers. We find experimentally and confirm theoretically that in orientation-averaged angle-resolved high-order above-threshold ionization spectra the corresponding destructive interference is visible for O{sub 2} but not for N{sub 2}. This effect is different from the suppression of ionization that is well known to occur for O{sub 2}.

  11. Atomic alignment effect on reactivity and on product alignment in the energy-transfer reaction of oriented Ar (3P2, 4s [3/2]2, M(J) = 2) + Kr (4p6, 1S0) → Ar (3p6, 1S0) + Kr (5p [3/2]2).

    PubMed

    Ohoyama, H

    2015-03-12

    Steric effect for the formation of Kr (5p [3/2]₂) in the energy transfer reaction of Ar (³P₂, 4s [3/2]₂) + Kr has been studied by using an oriented Ar (³P₂, 4s [3/2]₂, M(J) = 2) beam at a collision energy of ∼0.09 eV. The emission intensity of Kr (5p [3/2]₂) is ca. 2 times enhanced when the angular momentum (J(Ar)) of Ar (³P₂) is aligned perpendicular to the relative velocity vector (v(R)). In addition, the Kr (5p [3/2]₂) emission is highly polarized parallel to v(R) (I(∥)/I(⊥) ∼ 1.2) when JAr is aligned perpendicular to v(R). The observed polarization moments indicate that the alignment of the unpaired Ar (3p) orbital of Ar (³P₂) to v(R), (Σ (|L′| = 0), Π (|L′| = 1)), dominates the energy transfer probability (σ(Π)(∥): σ(Σ)(∥): σ(Π)(⊥): σ(Σ)(⊥) = 0.49:1.33:0.55:1.23) and also the alignment of the Kr (5p) orbital of Kr (5p [3/2]₂) to v(R): the Σ-configuration of the Ar (3p) orbital leads to the parallel alignment (Σ-configuration) of the Kr(5p) orbital to v(R), conversely, the Π-configuration of Ar (3p) orbital leads to the perpendicular alignment (Π-configuration) of the Kr(5p) orbital. In addition, the selectivity of the alignment of the Kr (5p) orbital turns out to vary from perpendicular to parallel as the collision energy increases after a threshold down to 0.03 eV.

  12. Monte Carlo simulation of the nuclear-electromagnetic cascade development and the energy response of ionization spectrometers

    NASA Technical Reports Server (NTRS)

    Jones, W. V.

    1973-01-01

    Modifications to the basic computer program for performing the simulations are reported. The major changes include: (1) extension of the calculations to include the development of cascades initiated by heavy nuclei, (2) improved treatment of the nuclear disintegrations which occur during the interactions of hadrons in heavy absorbers, (3) incorporation of accurate multi-pion final-state cross sections for various interactions at accelerator energies, (4) restructuring of the program logic so that calculations can be made for sandwich-type detectors, and (5) logic modifications related to execution of the program.

  13. Multiple measurements of time of flight, position and energy deposit of ionizing particles by solid state detectors.

    NASA Astrophysics Data System (ADS)

    Codino, Antonio

    1997-03-01

    A telescope made of silicon strip detectors performing simultaneous measurements of position, time and energy deposit has been constructed and operated. The telescope has been tested with a pion beam of 4 GeV/c at the CERN Proton Synchrotron. The intrinsic time resolution of the telescope measured in the beam test is 61+/-7 ps. This unprecedented time resolution is achieved by the multiple sampling of the time of flight. Future developments of this telescope aiming at the construction of a new, analogous instrument of large sensitive area are considered (LATIN project).

  14. Inelastic electronic excitation and electron transfer processes in collisions between Mg(3 {sup 1}S{sub 0}) atoms and K{sup +}({sup 1}S{sub 0}) ions studied by crossed beams in the 0.10-3.80-keV energy range

    SciTech Connect

    Sabido, M.; Andres, J. de; Sogas, J.; Lucas, J.M.; Alberti, M.; Bofill, J.M.; Aguilar, A.

    2005-09-22

    Inelastic and charge-transfer excitation processes in collisions between ground-state neutral Mg atoms and K{sup +} ions have been studied by means of a crossed molecular-beam technique. Decay fluorescent emissions from Mg(3 {sup 1}P{sub 1}),Mg(4 {sup 3}S{sub 1}), and Mg(3s{sup 1}3d{sup 1},3 {sup 3}D{sub 3,2,1}) as well as the phosphorescent emission due to Mg(3 {sup 3}P{sub 1}) have been observed from excited Mg atoms and the charge-transfer emission decays from K(4 {sup 2}P{sub 3/2,1/2}),K(5 {sup 2}P{sub 3/2,1/2}),K(6 {sup 2}S{sub 1/2}), and K(4 {sup 2}D{sub 5/2,3/2}) for excited K atoms. The corresponding absolute cross-sections values versus collision energy functions were determined in the 0.10-3.80 keV laboratory energy range. In order to interpret the experimental results, accurate ab initio full configuration-interaction calculations using pseudopotentials have been performed for the (Mg-K){sup +} system, giving a manifold of adiabatic singlet and triplet potential-energy curves correlating with the different collision channels, which allow a qualitative interpretation of the emission excitation functions measured for the different processes studied. A comparative study with other Mg-alkali ion systems previously studied is also included.

  15. Correlation of hydrogen-atom abstraction reaction efficiencies for aryl radicals with their vertical electron affinities and the vertical ionization energies of the hydrogen-atom donors.

    PubMed

    Jing, Linhong; Nash, John J; Kenttämaa, Hilkka I

    2008-12-31

    The factors that control the reactivities of aryl radicals toward hydrogen-atom donors were studied by using a dual-cell Fourier-transform ion cyclotron resonance mass spectrometer. Hydrogen-atom abstraction reaction efficiencies for two substrates, cyclohexane and isopropyl alcohol, were measured for 23 structurally different, positively charged aryl radicals, which included dehydrobenzenes, dehydronaphthalenes, dehydropyridines, and dehydro(iso)quinolines. A logarithmic correlation was found between the hydrogen-atom abstraction reaction efficiencies and the (calculated) vertical electron affinities (EA) of the aryl radicals. Transition state energies calculated for the reaction of three of the aryl radicals with isopropyl alcohol were found to correlate linearly with their (calculated) EAs. No correlation was found between the hydrogen-atom abstraction reaction efficiencies and the (calculated) enthalpy changes for the reactions. Measurement of the reaction efficiencies for the reactions of 15 different hydrogen-atom donors with two selected aryl radicals revealed a logarithmic correlation between the hydrogen-atom abstraction reaction efficiencies and the vertical ionization energies (IE) of the hydrogen-atom donors, but not the lowest homolytic X-H (X = heavy atom) bond dissociation energies of the hydrogen-atom donors. Examination of the hydrogen-atom abstraction reactions of 29 different aryl radicals and 18 different hydrogen-atom donors showed that the reaction efficiency increases (logarithmically) as the difference between the IE of the hydrogen-atom donor and the EA of the aryl radical decreases. This dependence is likely to result from the increasing polarization, and concomitant stabilization, of the transition state. Thus, the hydrogen-atom abstraction reaction efficiency for an aryl radical can be "tuned" by structural changes that influence either the vertical EA of the aryl radical or the vertical IE of the hydrogen atom donor.

  16. The effect of a compression paddle on energy response, calibration and measurement with mammographic dosimeters using ionization chambers and solid-state detectors.

    PubMed

    Hourdakis, C J; Boziari, A; Koumbouli, E

    2009-02-21

    A compression paddle is always used in mammography x-ray examinations, in order to improve image quality and reduce patient doses. Although clinical dose measurements should be performed with the paddle to interfere with the x-ray beam, calibration of mammography dosimeters is performed free in air without the presence of the paddle. The paddle hardens the x-ray beam, which has an impact on a dosimeter performance, particularly on high-energy-dependent detectors. Due to the paddle, clinical mammography x-ray systems may exhibit beams with HVL values exceeding those of the IEC 61267 RQR-M series qualities at which dosimeters are usually calibrated. In this study, the influence of the paddle in mammography dosimetry is examined, in Mo/Mo anode/filter x-ray qualities. PMMA slabs of 1, 2 and 3 mm thickness and Al foils of 0.05, 0.10 and 0.15 mm thicknesses were used to simulate the paddles, producing beams with HVL values from 0.28 up to 0.43 mmAl. In these qualities, four solid-state (ST) detectors and three ionizations chambers (IC) were calibrated in terms of Kair and N(K) and k(Q) were deduced. The results showed that all IC and two modern-type ST dosimeters have a flat energy response in the above HVL range (less than 3%), so their calibration factor at RQR-M2 quality could be safely used for clinical measurements. Two other ST dosimeters exhibit up to 20% energy response, so differences up to 15% in dose measurement may be observed if the effect of paddle on their performance is ignored. Finally, the need of additional mammographic calibration qualities to the existing IEC 61267 RQR-M series is examined and discussed.

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

    SciTech Connect

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

    2002-07-18

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

  18. Laser-induced dissociative ionization of H2 from the near-infrared to the mid-infrared regime

    NASA Astrophysics Data System (ADS)

    Jing, Qingli; Madsen, Lars Bojer

    2016-12-01

    We apply the Monte Carlo wave packet (MCWP) approach to investigate the kinetic energy release (KER) spectra of the protons following double ionization in H2 when interacting with laser pulses with central wavelengths ranging from the near-infrared (IR) (800 nm) to the mid-IR (6400 nm) regions and with durations of 3-21 laser cycles. We uncover the physical origins of the peaks in the nuclear KER spectra and ascribe them to mechanisms such as ionization following a resonant dipole transition, charge-resonance-enhanced ionization, and ionization in the dissociative limit of large internuclear distances. For relatively large pulse durations, i.e., for 15 or more laser cycles at 3200 nm and 10 or more at 6400 nm, it is possible for the nuclear wave packet in H2+ to reach very large separations. Ionization of this part of the wave packet results in peaks in the KER spectra with very low energies. These peaks give direct information about the dissociative energy in the 2 p σu potential energy curve of H2+ at the one- and three-photon resonances between the 2 p σu and 1 s σg curves in H2+ . With the MCWP approach, we perform a trajectory analysis of the contributions to the KER peaks and identify the dominant ionization pathways. Finally, we consider a pump-probe scheme by applying two delayed pulses to track the nuclear dynamics in a time-resolved setting. Low-energy peaks appear for large delays and these are used to obtain the 2 p σu dissociative energy values at the one-photon resonance between the 2 p σu and 1 s σg curves in H2+ for different wavelengths.

  19. Biomolecular damage induced by ionizing radiation: the direct and indirect effects of low-energy electrons on DNA.

    PubMed

    Alizadeh, Elahe; Orlando, Thomas M; Sanche, Léon

    2015-04-01

    Many experimental and theoretical advances have recently allowed the study of direct and indirect effects of low-energy electrons (LEEs) on DNA damage. In an effort to explain how LEEs damage the human genome, researchers have focused efforts on LEE interactions with bacterial plasmids, DNA bases, sugar analogs, phosphate groups, and longer DNA moieties. Here, we summarize the current understanding of the fundamental mechanisms involved in LEE-induced damage of DNA and complex biomolecule films. Results obtained by several laboratories on films prepared and analyzed by different methods and irradiated with different electron-beam current densities and fluencies are presented. Despite varied conditions (e.g., film thicknesses and morphologies, intrinsic water content, substrate interactions, and extrinsic atmospheric compositions), comparisons show a striking resemblance in the types of damage produced and their yield functions. The potential of controlling this damage using molecular and nanoparticle targets with high LEE yields in targeted radiation-based cancer therapies is also discussed.

  20. Biomolecular Damage Induced by Ionizing Radiation: The Direct and Indirect Effects of Low-Energy Electrons on DNA

    NASA Astrophysics Data System (ADS)

    Alizadeh, Elahe; Orlando, Thomas M.; Sanche, Léon

    2015-04-01

    Many experimental and theoretical advances have recently allowed the study of direct and indirect effects of low-energy electrons (LEEs) on DNA damage. In an effort to explain how LEEs damage the human genome, researchers have focused efforts on LEE interactions with bacterial plasmids, DNA bases, sugar analogs, phosphate groups, and longer DNA moieties. Here, we summarize the current understanding of the fundamental mechanisms involved in LEE-induced damage of DNA and complex biomolecule films. Results obtained by several laboratories on films prepared and analyzed by different methods and irradiated with different electron-beam current densities and fluencies are presented. Despite varied conditions (e.g., film thicknesses and morphologies, intrinsic water content, substrate interactions, and extrinsic atmospheric compositions), comparisons show a striking resemblance in the types of damage produced and their yield functions. The potential of controlling this damage using molecular and nanoparticle targets with high LEE yields in targeted radiation-based cancer therapies is also discussed.

  1. Response of liquid xenon to low-energy ionizing radiation and its use in the XENON10 dark matter search

    NASA Astrophysics Data System (ADS)

    Manalaysay, Aaron Gosta

    This dissertation focuses on developments aimed at improving the effectiveness and understanding of liquid xenon particle detectors in their use in the field of dark matter direct detection. Chapter 3 covers the XENON10 experiment, which searches for evidence of direct interactions between Weakly Interacting Massive Particles (WIMPs) and Xe nuclei. The 3-D position sensitive liquid xenon time projection chamber acquired 58.6 live days of WIMP search data from October, 2006 through February, 2007. The results of these data set new limits on both spin-independent and spin-dependent interactions. The spin-independent WIMP-nucleon cross section is constrained to be less than 4.5 x 10-44 cm2 for WIMPs of mass 30 GeV/ c2 and less than 8.8 x 10-44 cm2 for WIMPs of mass 100 GeV/c2 at the 90% confidence level. The spin-dependent WIMP-neutron and WIMP-proton cross sections are constrained to be less than 10-39 cm 2 and 10-36 cm2, respectively. Finally, the mass of the heavy Majorana neutrino, in the context of a dark matter candidate, is excluded for masses in the range 10 GeV/c2 to 2.2TeV/c2. Chapter 4 discusses the study of the relative scintillation efficiency of nuclear recoils in liquid xenon. The two existing measurements of the relative scintillation efficiency of nuclear recoils below 20 keV lead to inconsistent extrapolations at lower energies. This results in a different energy scale and thus sensitivity reach of liquid xenon dark matter detectors. A new measurement of the relative scintillation efficiency below 10 keV, performed with a liquid xenon scintillation detector and optimized for maximum light collection is discussed. Greater than 95% of the interior surface of this detector was instrumented with photomultiplier tubes, giving a scintillation yield of 19.6 photoelectrons/keV electron equivalent for 122 keV gamma rays. The relative scintillation efficiency for nuclear recoils of 5 keV is found to be 0.14, staying constant around this value up to 10 keV. For

  2. Single ionization of molecular iodine

    NASA Astrophysics Data System (ADS)

    Smith, Dale L.; Tagliamonti, Vincent; Dragan, James; Gibson, George N.

    2017-01-01

    We performed a study of the single ionization of iodine, I2 over a range of wavelengths. Single ionization of I2 is unexpectedly found to have a contribution from inner molecular orbitals involving the 5 s electrons. The I+I+ dissociation channel was recorded through velocity map imaging, and the kinetic-energy release of each channel was determined with two-dimensional fitting of the images. Most of the measured kinetic-energy data were inconsistent with ionization to the X , A , and B states of I2 + , implying ionization from deeper orbitals. A pump-probe Fourier transform technique was used to look for modulation at the X - and A -state vibrational frequencies to see if they were intermediate states in a two-step process. X - and A -state modulation was seen only for kinetic-energy releases below 0.2 eV, consistent with dissociation through the B state. From these results and intensity-, polarization-, and wavelength-dependent experiments we found no evidence of bond softening, electron rescattering, or photon mediation through the X or A states to higher-energy single-ionization channels.

  3. Fluorescence spectroscopy of UV-MALDI matrices and implications of ionization mechanisms

    NASA Astrophysics Data System (ADS)

    Lin, Hou-Yu; Hsu, Hsu Chen; Lu, I.-Chung; Hsu, Kuo-Tung; Liao, Chih-Yu; Lee, Yin-Yu; Tseng, Chien-Ming; Lee, Yuan-Tseh; Ni, Chi-Kung

    2014-10-01

    Matrix-assisted laser desorption ionization (MALDI) has been widely used in the mass analysis of biomolecules; however, there are a lot of debates about the ionization mechanisms. Previous studies have indicated that S1-S1 annihilation might be a key process in the generation of primary ions. This study investigates S1-S1 annihilation by examining the time-resolved fluorescence spectra of 12 matrices. No S1-S1 annihilation was observed in six of these matrices (3-hydroxy-picolinic acid, 6-aza-2-thiothymine, 2,4-dihydroxy-acetophenone, 2,6-dihydroxy-acetophenone, 2,4,6-trihydroxy-acetophenone, and ferulic acid). We observed two matrix molecules reacting in an electronically excited state (S1) in five of these matrices (2,5-dihydroxybenzoic acid, α-cyano-4-hydroxycinnamic acid, 2,5-dihydroxy-acetophenone, 2,3-dihydroxybenzoic acid, and 2,6-dihydroxybenzoic acid), and S1-S1 annihilation was a possible reaction. Among these five matrices, no S1-S1 annihilation was observed for 2,3-dihydroxybenzoic acid in typical peak power region of nanosecond laser pulses in MALDI, but a very small value of reaction rate constant was observed only in the high peak power region. The excited-state lifetime of sinapinic acid was too short to determine whether the molecules reacted in an electronically excited state. No correlation was observed between the ion generation efficiency of MALDI and S1-S1 annihilation. The results indicate that the proposal of S1-S1 annihilation is unnecessary in MALDI and energy pooling model for MALDI ionization mechanism has to be modified.

  4. Fluorescence spectroscopy of UV-MALDI matrices and implications of ionization mechanisms

    SciTech Connect

    Lin, Hou-Yu; Hsu, Hsu Chen; Lu, I-Chung; Lee, Yuan-Tseh; Ni, Chi-Kung; Hsu, Kuo-Tung; Liao, Chih-Yu; Lee, Yin-Yu; Tseng, Chien-Ming

    2014-10-28

    Matrix-assisted laser desorption ionization (MALDI) has been widely used in the mass analysis of biomolecules; however, there are a lot of debates about the ionization mechanisms. Previous studies have indicated that S{sub 1}-S{sub 1} annihilation might be a key process in the generation of primary ions. This study investigates S{sub 1}-S{sub 1} annihilation by examining the time-resolved fluorescence spectra of 12 matrices. No S{sub 1}-S{sub 1} annihilation was observed in six of these matrices (3-hydroxy-picolinic acid, 6-aza-2-thiothymine, 2,4-dihydroxy-acetophenone, 2,6-dihydroxy-acetophenone, 2,4,6-trihydroxy-acetophenone, and ferulic acid). We observed two matrix molecules reacting in an electronically excited state (S{sub 1}) in five of these matrices (2,5-dihydroxybenzoic acid, α-cyano-4-hydroxycinnamic acid, 2,5-dihydroxy-acetophenone, 2,3-dihydroxybenzoic acid, and 2,6-dihydroxybenzoic acid), and S{sub 1}-S{sub 1} annihilation was a possible reaction. Among these five matrices, no S{sub 1}-S{sub 1} annihilation was observed for 2,3-dihydroxybenzoic acid in typical peak power region of nanosecond laser pulses in MALDI, but a very small value of reaction rate constant was observed only in the high peak power region. The excited-state lifetime of sinapinic acid was too short to determine whether the molecules reacted in an electronically excited state. No correlation was observed between the ion generation efficiency of MALDI and S{sub 1}-S{sub 1} annihilation. The results indicate that the proposal of S{sub 1}-S{sub 1} annihilation is unnecessary in MALDI and energy pooling model for MALDI ionization mechanism has to be modified.

  5. Turbulence and the ionization of interstellar gas

    NASA Astrophysics Data System (ADS)

    Hill, Alex S.

    2015-08-01

    Turbulence is widely observed in the ionized gas in the interstellar media of star-forming galaxies. Observations in the Milky Way indicate emission from that the warm ionized medium -- ionized gas far from massive stars, the most likely source of the ionization -- has a lognormal intensity distribution. This and other measurements indicate that the gas is well-described as a transonic turbulent fluid. Such a fluid can be produced by feedback from supernovae in the Galaxy. Understanding of this turbulence has also led to a natural explanation for a long-standing puzzle: how do ionizing photons travel through the largely-neutral interstellar medium and produce the ionization? In the turbulent gas, low-density pathways allow ionizing photons to propagate for kiloparsecs, with implications for radiative energy transport in star-forming galaxies.

  6. Absolute triple-differential cross sections for ionization-excitation of helium

    SciTech Connect

    Bartschat, K.; Bray, I.; Fursa, D. V.; Stelbovics, A. T.

    2007-08-15

    Triple-differential cross sections (TDCSs) for electron-impact ionization of He(1s{sup 2}){sup 1}S leading to He{sup +}(1s) are calculated using the highly accurate convergent close-coupling (CCC) method for incident projectile energies of 268.6 and 112.6 eV, with at least one of the outgoing electrons having an energy of 44 eV. These results are used to obtain absolute TDCSs from the recent experimental data [Bellm et al., Phys. Rev. A 75, 042704 (2007)] for TDCS ratios of ionization with no excitation to ionization with excitation resulting in He{sup +}(n=2,3,4). The TDCSs can be used as comparison benchmarks in future studies, and already allow us to test the accuracy of the TDCSs obtained from the hybrid distorted-wave+R-matrix (close-coupling) model, which was fairly successful in predicting the ratios, using CCC for n=1 and experimental results for n=2,3,4.

  7. Fluid hydrogen at high density - Pressure ionization

    NASA Technical Reports Server (NTRS)

    Saumon, Didier; Chabrier, Gilles

    1992-01-01

    The Helmholtz-free-energy model for nonideal mixtures of hydrogen atoms and molecules by Saumon and Chabrier (1991) is extended to describe dissociation and ionization in similar mixtures in chemical equilibrium. A free-energy model is given that describes partial ionization in the pressure and temperature ionization region. The plasma-phase transition predicted by the model is described for hydrogen mixtures including such components as H2, H, H(+), and e(-). The plasma-phase transition has a critical point at Tc = 15,300 K and Pc = 0.614 Mbar, and thermodynamic instability is noted in the pressure-ionization regime. The pressure dissociation and ionization of fluid hydrogen are described well with the model yielding information on the nature of the plasma-phase transition. The model is shown to be valuable for studying dissociation and ionization in astrophysical objects and in high-pressure studies where pressure and temperature effects are significant.

  8. Electron ionization of H2O

    NASA Astrophysics Data System (ADS)

    King, Simon J.; Price, Stephen D.

    2008-11-01

    Relative partial ionization cross-sections and precursor-specific relative partial ionization cross-sections for fragment ions formed by electron ionization of H2O have been measured using time-of-flight mass spectrometry coupled with a 2D ion coincidence technique. We report data for the formation of H+, H2+, O2+, O+ and OH+ relative to the formation of H2O+, as a function of ionizing electron energy from 30 to 200 eV. This data includes, for the first time, measurements on the formation all positive ion pairs and ion triples by dissociative multiple electron ionization of H2O. Through determinations of the kinetic energy release involved in ion pair formation we provide further evidence that indirect processes contribute significantly to the yield of H+ + OH+ ion pairs below the vertical double ionization threshold.

  9. Correction factors for the NMi free-air ionization chamber for medium-energy x-rays calculated with the Monte Carlo method.

    PubMed

    Grimbergen, T W; van Dijk, E; de Vries, W

    1998-11-01

    A new method is described for the determination of x-ray quality dependent correction factors for free-air ionization chambers. The method is based on weighting correction factors for mono-energetic photons, which are calculated using the Monte Carlo method, with measured air kerma spectra. With this method, correction factors for electron loss, scatter inside the chamber and transmission through the diaphragm and front wall have been calculated for the NMi free-air chamber for medium-energy x-rays for a wide range of x-ray qualities in use at NMi. The newly obtained correction factors were compared with the values in use at present, which are based on interpolation of experimental data for a specific set of x-ray qualities. For x-ray qualities which are similar to this specific set, the agreement between the correction factors determined with the new method and those based on the experimental data is better than 0.1%, except for heavily filtered x-rays generated at 250 kV. For x-ray qualities dissimilar to the specific set, differences up to 0.4% exist, which can be explained by uncertainties in the interpolation procedure of the experimental data. Since the new method does not depend on experimental data for a specific set of x-ray qualities, the new method allows for a more flexible use of the free-air chamber as a primary standard for air kerma for any x-ray quality in the medium-energy x-ray range.

  10. Molecular-orbital decomposition of the ionization continuum for a diatomic molecule by angle- and energy-resolved photoelectron spectroscopy. I. Formalism

    NASA Astrophysics Data System (ADS)

    Park, Hongkun; Zare, Richard N.

    1996-03-01

    A theoretical formalism is developed for the quantum-state-specific photoelectron angular distributions (PADs) from the direct photoionization of a diatomic molecule in which both the ionizing state and the state of the ion follow Hund's case (b) coupling. The formalism is based on the molecular-orbital decomposition of the ionization continuum and therefore fully incorporates the molecular nature of the photoelectron-ion scattering within the independent electron approximation. The resulting expression for the quantum-state-specific PADs is dependent on two distinct types of dynamical quantities, one that pertains only to the ionization continuum and the other that depends both on the ionizing state and the ionization continuum. Specifically, the electronic dipole-moment matrix element rlλ exp(iηlλ) for the ejection of a photoelectron with orbital angular momentum quantum number l making a projection λ on the internuclear axis is expressed as ΣαλŪlαλλ exp (iπτ¯αλλ) Mαλλ, where Ūλ is the electronic transformation matrix, τ¯αλλ is the scattering phase shift associated with the αλth continuum molecular orbital, and Mαλλ is the real electronic dipole-moment matrix element that connects the ionizing orbital to the αλth continuum molecular orbital. Because Ūλ and τ¯αλλ depend only on the dynamics in the ionization continuum, this formalism allows maximal exploitation of the commonality between photoionization processes from different ionizing states. It also makes possible the direct experimental investigation of scattering matrices for the photoelectron-ion scattering and thus the dynamics in the ionization continuum by studying the quantum-state-specific PADs, as illustrated in the companion article on the photoionization of NO.

  11. Electronic states, ionization potentials, and bond energies of TlHn, InHn, TlH + n, and InH + n (n=1-3)

    NASA Astrophysics Data System (ADS)

    Balasubramanian, K.; Tao, J. X.

    1991-02-01

    Potential energy surfaces of 6 electronic states of TlH2 and InH2 and 8 electronic states of TlH+2 and InH+2 are computed. In addition the ground states of TlH3, InH3, TlH+3, InH+3, TlH, and TlH+ are investigated. A complete active space multiconfiguration self-consistent field (CAS-MCSCF) followed by second-order configuration interaction (SOCI) and relativistic configuration interaction (RCI) including spin-orbit coupling calculations are carried out. The step-wise bond energies, De(Hn-1M-H) and adiabatic ionization potentials are computed. The ground states of TlH2 and InH2 are found to be bent (2A1; θe˜121.5 °, 120 °) while the ground states of TlH+2 and InH+2 are linear (1Σ+g). The ground states of TlH3 and InH3 are found to be 1A1 (D3h ) states while the ground states of TlH+3 and InH+3 are Jahn-Teller distorted 2B2(C2v ) states. The unique bond length of TlH+3 and InH+3 is shorter than the two equal bond lengths. The bond angles (H-M-H) for TlH+3 and InH+3 deviate considerably from the neutral θe=120 ° to near 69 °. The TlH+ ion is found to be only 0.04 eV stable. Periodic trends in the geometries, bond energies and IPs are studied. Spin-orbit effects were found to be significant for TlHn species. The IPs of InHn and TlHn exhibit odd-even alternation. The bond energies also show an interesting trend as a function of n.

  12. Multiphoton Ionization Mass and Photoelectron Spectroscopy.

    DTIC Science & Technology

    1984-07-01

    narro , band. tunable. frequency doubled dye laser Their relative importance depend% on the sample being studied ha- led to an cnormou, improcment in...block number) Mult iphoton Ionization Photoelectron Spectroscopy Laser Induced Ionization Ultraviolet Laser Radiation ft ArITAcr (camthIe i rvee ehl N...molecular ions generated by laser ionization have been monitored. Using a time of flight photoelectron spectrometer, the kinetic energy distribution of the

  13. Field ionization of high-Rydberg fragments produced after inner-shell photoexcitation and photoionization of the methane molecule

    SciTech Connect

    Kivimäki, A.; Sankari, A.; Kettunen, J. A.; Stråhlman, C.; Álvarez Ruiz, J.; Richter, R.

    2015-09-21

    We have studied the production of neutral high-Rydberg (HR) fragments from the CH{sub 4} molecule at the C 1s → 3p excitation and at the C 1s ionization threshold. Neutral fragments in HR states were ionized using a pulsed electric field and the resulting ions were mass-analyzed using an ion time-of-flight spectrometer. The atomic fragments C(HR) and H(HR) dominated the spectra, but molecular fragments CH{sub x}(HR), x = 1-3, and H{sub 2}(HR) were also observed. The production of HR fragments is attributed to dissociation of CH{sub 4}{sup +} and CH{sub 4}{sup 2+} ions in HR states. Just above the C 1s ionization threshold, such molecular ionic states are created when the C 1s photoelectron is recaptured after single or double Auger decay. Similar HR states may be reached directly following resonant Auger decay at the C 1s → 3p resonance. The energies and geometries of the parent and fragment ions have been calculated in order to gain insight into relevant dissociation pathways.

  14. Field ionization of high-Rydberg fragments produced after inner-shell photoexcitation and photoionization of the methane molecule

    NASA Astrophysics Data System (ADS)

    Kivimäki, A.; Sankari, A.; Kettunen, J. A.; Strâhlman, C.; Álvarez Ruiz, J.; Richter, R.

    2015-09-01

    We have studied the production of neutral high-Rydberg (HR) fragments from the CH4 molecule at the C 1s → 3p excitation and at the C 1s ionization threshold. Neutral fragments in HR states were ionized using a pulsed electric field and the resulting ions were mass-analyzed using an ion time-of-flight spectrometer. The atomic fragments C(HR) and H(HR) dominated the spectra, but molecular fragments CHx(HR), x = 1-3, and H2(HR) were also observed. The production of HR fragments is attributed to dissociation of CH4+ and CH42+ ions in HR states. Just above the C 1s ionization threshold, such molecular ionic states are created when the C 1s photoelectron is recaptured after single or double Auger decay. Similar HR states may be reached directly following resonant Auger decay at the C 1s → 3p resonance. The energies and geometries of the parent and fragment ions have been calculated in order to gain insight into relevant dissociation pathways.

  15. Field ionization of high-Rydberg fragments produced after inner-shell photoexcitation and photoionization of the methane molecule.

    PubMed

    Kivimäki, A; Sankari, A; Kettunen, J A; Stråhlman, C; Álvarez Ruiz, J; Richter, R

    2015-09-21

    We have studied the production of neutral high-Rydberg (HR) fragments from the CH4 molecule at the C 1s → 3p excitation and at the C 1s ionization threshold. Neutral fragments in HR states were ionized using a pulsed electric field and the resulting ions were mass-analyzed using an ion time-of-flight spectrometer. The atomic fragments C(HR) and H(HR) dominated the spectra, but molecular fragments CH(x)(HR), x = 1-3, and H2(HR) were also observed. The production of HR fragments is attributed to dissociation of CH4(+) and CH4(2+) ions in HR states. Just above the C 1s ionization threshold, such molecular ionic states are created when the C 1s photoelectron is recaptured after single or double Auger decay. Similar HR states may be reached directly following resonant Auger decay at the C 1s → 3p resonance. The energies and geometries of the parent and fragment ions have been calculated in order to gain insight into relevant dissociation pathways.

  16. Scintillation and ionization responses of liquid xenon to low energy electronic and nuclear recoils at drift fields from 236 V /cm to 3.93 kV /cm

    NASA Astrophysics Data System (ADS)

    Lin, Qing; Fei, Jialing; Gao, Fei; Hu, Jie; Wei, Yuehuan; Xiao, Xiang; Wang, Hongwei; Ni, Kaixuan

    2015-08-01

    We present new measurements of the scintillation and ionization yields in liquid xenon for low energy electronic (about 3 - 7 keVe e ) and nuclear recoils (about 8 - 20 keVn r ) at different drift fields from 236 V /cm to 3.93 kV /cm , using a three-dimensional sensitive liquid xenon time projection chamber with high energy and position resolutions. Our measurement of signal responses to nuclear recoils agrees with predictions from the NEST model. However, our measured ionization (scintillation) yields for electronic recoils are consistently higher (lower) than those from the NEST model by about 5 e-/keVe e (ph /keVe e) at all scanned drift fields. New recombination parameters based on the Thomas-Imel box model are derived from our data. Given the lack of precise measurement of scintillation and ionization yields for low energy electronic recoils in liquid xenon previously, our new measurement provides so far the best available data covering low energy regions at different drift fields for liquid xenon detectors relevant to dark matter searches.

  17. Penning ionization electron spectroscopy of hydrogen sulfide by metastable helium and neon atoms.

    PubMed

    Falcinelli, Stefano; Candori, Pietro; Bettoni, Marta; Pirani, Fernando; Vecchiocattivi, Franco

    2014-08-21

    The dynamics of the Penning ionization of hydrogen sulfide molecules by collision with helium and metastable neon atoms, occurring in the thermal energy range, has been studied by analyzing the energy spectra of the emitted electrons obtained in our laboratory in a crossed beam experiment. These spectra are compared with the photoelectron spectra measured by using He(I) and Ne(I) photons under the same experimental conditions. In this way we obtained the negative energy shifts for the formation of H2S(+) ions in the first three accessible electronic states by He*(2(3,1)S1,0) and Ne*((3)P2,0) Penning ionization collisions: the 2b1 (X̃(2)B1) fundamental one, the first 5a1 (Ã(2)A1), and the second 2b2 (B̃(2)B2) excited states, respectively. The recorded energy shifts indicate that in the case of He* and Ne*-H2S the autoionization dynamics depends on the features of the collision complex and is mainly driven by an effective global attraction that comes from a balance among several non covalent intermolecular interaction components. This suggests that the Penning ionization should take place, in a specific range of intermolecular distances, as we have already observed in the case of Penning ionization of water molecules [Brunetti, B. G.; Candori, P.; Falcinelli, S.; Pirani, F.; Vecchiocattivi, F. J. Chem. Phys. 2013, 139, 164305-1-164305-8].

  18. Method for estimating ionicities of oxides using O1s photoelectron spectra

    SciTech Connect

    Wu, L. Q.; Li, Z. Z.; Tang, G. D. Qi, W. H.; Xue, L. C.; Ge, X. S.; Ding, L. L.; Li, Y. C.; Li, S. Q.

    2015-09-15

    The average valence, V{sub alO}, of the oxygen anions in the perovskite oxide BaTiO{sub 3}, was found using O1s photoelectron spectra to be −1.55. This experimental result is close to the theoretical value for BaTiO{sub 3} (−1.63) calculated by Cohen [Nature 358, 136 (1992)] using density functional theory. Using the same approach, we obtained values of V{sub alO} for several monoxides, and investigated the dependence of V{sub alO} and the ionicity on the second ionization energy, V(M{sup 2+}), of the metal cation. We found that the dependence of the ionicity on V(M{sup 2+}) in this work is close to that reported by Phillips [Rev. Mod. Phys. 42, 317 (1970)]. We therefore suggest that O1s photoelectron spectrum measurements should be accepted as a general experimental method for estimating the ionicity and average valence of oxygen anions.

  19. Carbon dioxide ion dissociations after inner shell excitation and ionization: The origin of site-specific effects

    SciTech Connect

    Eland, J. H. D.; Zagorodskikh, S.; Mucke, M.; Squibb, R. J.; Feifel, R.; Sorensen, S. L.

    2014-05-14

    Multi-coincidence experiments with detection of both electrons and ions from decay of core-excited and core-ionized states of CO{sub 2} confirm that O{sub 2}{sup +} is formed specifically in Auger decay from the C1s-π* and O1s-π* resonances. Molecular rearrangement occurs by bending in the resonant states, and O{sub 2}{sup +} is produced by both single and double Auger decay. It is suggested that electron capture by C{sup +} after partial dissociation in the doubly ionized core of excited CO{sub 2}{sup +}, formed by shake-up in spectator resonant Auger decay, accounts for high kinetic energy and high internal energy in some C + O{sub 2}{sup +} fragments.

  20. Two-Color Laser Resonance Ionization Spectroscopy of Zirconium Atoms

    NASA Astrophysics Data System (ADS)

    Hasegawa, Shuichi; Nagamoto, Daisuke

    2017-10-01

    We have performed two-color laser resonance ionization spectroscopy of zirconium atoms to measure the energies of excited states below the third ionization limit. The number of intermediate states that we observed is 19, and energies deduced from the experiments agree with previous data. Complex ionization spectra of the excited states were observed through the intermediate states. The values of the first, second, and third ionization limits were derived from the Rydberg series of the spectra with quantum defect theory.

  1. Regulation of ATM in DNA double strand break repair accounts for the radiosensitivity in human cells exposed to high linear energy transfer ionizing radiation.

    PubMed

    Xue, Lian; Yu, Dong; Furusawa, Yoshiya; Okayasu, Ryuichi; Tong, Jian; Cao, Jianping; Fan, Saijun

    2009-11-02

    High linear energy transfer (LET) radiation shows different biological effects from low-LET radiation. The complex nature of high LET radiation-induced damage, especially the clustered DNA damage, brings about slow repair of DNA double strand breaks (DSBs), which finally lead to higher lethality and chromosome aberration. Ionizing radiation (IR) induced DNA DSBs are repaired by both non-homologous end-joining (NHEJ) and homologous recombination repair (HRR) pathways in mammalian cells. The novel function of ataxia telangiectasia-mutated (ATM) protein is its involvement in the DSB repair of slow kinetics for "dirty" breaks rejoining by NHEJ, this suggests that ATM may play a more important role in high LET radiation-induced DNA damage. We show here that KU55933, an ATM inhibitor could distinctly lower the clonogenic survival in normal human skin fibroblast cells exposed to carbon ion radiation and dramatically impair the normal process for DSB repair. We also implicated the involvement of ATM in the two pathways of DNA DSB repair, with DNA-PKcs and Rad51 as the representative proteins. The phosphorylation of DNA-PKcs at Thr-2609 with both immunoblotting and immunofluorescent staining indicated an ATM-dependent change, while for Rad51, KU55933 pretreatment could postpone the formation of nuclear Rad51 foci. Interestingly, we also found that pretreatment with chloroquine, an ATM stimulator could protect cells from carbon ion radiation only at lower doses. For doses over 1Gy, protection was no longer observed. There was a dose-dependent increase for ATM kinase activity, with saturation at about 1Gy. Chloroquine pretreatment prior to 1Gy of carbon ion radiation did not enhance the autophosphorylation of ATM at serine 1981. The function of ATM in G2/M checkpoint arrest facilitated DSB repair in high-LET irradiation. Our results provide a possible mechanism for the direct involvement of ATM in DSB repair by high-LET irradiation.

  2. Measurement of the He 1s2s (1)S(0) isotopic shift using a tunable VUV anti-Stokes light source.

    PubMed

    Falcone, R W; Willison, J R; Young, J F; Harris, S E

    1978-11-01

    We describe a high-resolution, vacuum-ultraviolet spectroscopic technique based on a tunable, narrow-band, VUV, spontaneous anti-Stokes light source. The technique was used to measure the absolute energies of the 1s2s (1)S(0) states of (3)He and (4)He; the 1s2s (1)S(0) level of (3)He is 7.8 +/- 0.5 cm(-1) below that of (4)He.

  3. Ionization Potentials for Isoelectronic Series.

    ERIC Educational Resources Information Center

    Agmon, Noam

    1988-01-01

    Presents a quantitative treatment of ionization potentials of isoelectronic atoms. By looking at the single-electron view of calculating the total energy of an atom, trends in the screening and effective quantum number parameters are examined. Approaches the question of determining electron affinities. (CW)

  4. Hard X-Ray Emission and the Ionizing Source in LINERs

    NASA Technical Reports Server (NTRS)

    Terashima, Yuichi; Ho, Luis C.; Ptak, Andrew F.

    2000-01-01

    We report X-ray fluxes in the 2-10 keV band from LINERs (low-ionization nuclear emission-line regions) and low-luminosity Seyfert galaxies obtained with the ASCA satellite. Observed X-ray luminosities are in the range between 4 x 10(exp 39) and 5 x 10(exp 41) ergs/s, which are significantly smaller than that of the "classical" low-luminosity Seyfert 1 galaxy NGC 4051. We found that X-ray luminosities in 2-10 keV of LINERs with broad H.alpha emission in their optical spectra (LINER 1s) are proportional to their Ha luminosities. This correlation strongly supports the hypothesis that the dominant ionizing source in LINER 1s is photoionization by hard photons from low-luminosity AGNs. On the other hand, the X-ray luminosities of most LINERs without broad H.alpha emission (LINER 2s) in our sample are lower than LINER 1s at a given H.alpha luminosity. The observed X-ray luminosities in these objects are insufficient to power their H.alpha luminosities, suggesting that their primary ionizing source is other than an AGN, or that an AGN, if present, is obscured even at energies above 2 keV.

  5. Ionized cluster beam deposition

    NASA Technical Reports Server (NTRS)

    Kirkpatrick, A. R.

    1983-01-01

    Ionized Cluster Beam (ICB) deposition, a new technique originated by Takagi of Kyoto University in Japan, offers a number of unique capabilities for thin film metallization as well as for deposition of active semiconductor materials. ICB allows average energy per deposited atom to be controlled and involves impact kinetics which result in high diffusion energies of atoms on the growth surface. To a greater degree than in other techniques, ICB involves quantitative process parameters which can be utilized to strongly control the characteristics of films being deposited. In the ICB deposition process, material to be deposited is vaporized into a vacuum chamber from a confinement crucible at high temperature. Crucible nozzle configuration and operating temperature are such that emerging vapor undergoes supercondensation following adiabatic expansion through the nozzle.

  6. Low energy photoelectron resonance capture ionization aerosol mass spectrometry of small peptides with cysteine residues: Cys-Gly, [gamma]-Glu-Cys, and glutathione ([gamma]-Glu-Cys-Gly)

    NASA Astrophysics Data System (ADS)

    Geddes, Scott; Zahardis, James; Eisenhauer, Jessica; Petrucci, Giuseppe A.

    2009-04-01

    The photoelectron resonance capture ionization (PERCI) of cysteine (Cys) and small gas-phase neutral peptides that contain the Cys residue (Cys-Gly, [gamma]-Glu-Cys, and glutathione ([gamma]-Glu-Cys-Gly)) is reported. At an ionization energy less than 1 eV two types of dissociative electron attachment ionization were observed for Cys: hydrogen atom loss, resulting in formation of the ion [Cys-H]-, and dissociation of the CH2-SH bond, resulting in formation of the ion [SH]-. The presence of these ions suggests that both the [pi]*(-CO2H) and [sigma]*(C-S) orbitals can act as low energy electrophores on Cys. This ionization trend was observed for the dipeptides Cys-Gly and [gamma]-Glu-Cys as well as glutathione, with evidence that dissociation of the CH2-SH bond in these peptides can also result in ions of the form [M-SH]-. Also measured were ions resulting from bond dissociation of the amide linkage as well as for the amide N-C[alpha] bond. In both of these cases the charge is retained on the fragment containing the nitrogen of the amide bond, indicating that ion formation by the PERCI process is directed by the electron affinity (EA) of the fragments. The backbone fragmentation of the PERCI process appears distinct from other low energy processes, including electron detachment dissociation and electron capture dissociation, as evidenced by the lack of amide C[alpha]-C cleavage; the dependence of ion formation on the EA of the fragments, not their H affinity; and the observation that PERCI is not a directionally restricted mechanism.

  7. Description of ionization in the molecular approach to atomic collisions

    SciTech Connect

    Harel, C.; Jouin, H.; Pons, B.; Errea, L.F.; Mendez, L.; Riera, A.

    1997-01-01

    Molecular treatments of atomic collisions have traditionally been restricted to low nuclear velocities because of their failure to reproduce the fall of the capture cross sections at higher velocities. The limitation has recently been seen to be due to their description of ionizing processes. This feature is shown here to be a general one for multicharged ion-atom collisions. Its origin and characteristics are described and illustrated for the prototypical Li{sup 3+}+H(1s) reaction. Ionization appears as a result of the inertia of the electron cloud to adiabatically follow the nuclear motion. This gives rise to nonadiabatic transitions, which represent an ionizing flux whenever the nuclear velocity is high enough that the energy of the traveling molecular orbitals involved is positive in both moving atomic reference frames. Two strongly connected mechanisms appear, corresponding to the relative translational and rotational nuclear motions. Because of the finiteness of the basis, these mechanisms terminate with unphysical trapping effects. While interesting {ital per se}, knowledge of these features is also useful with respect to improving molecular treatments of atomic collisions with the addition of pseudostates. {copyright} {ital 1996} {ital The American Physical Society}

  8. Oxidation of atomic gold ions: thermochemistry for the activation of O(2) and N(2)O BY Au(+) ((1)S(0) and (3)D).

    PubMed

    Li, Feng-Xia; Gorham, Katrine; Armentrout, P B

    2010-10-28

    Reaction of Au(+) ((1)S(0) and (3)D) with O(2) and N(2)O is studied as a function of kinetic energy using guided ion beam tandem mass spectrometry. A flow tube ion source produces Au(+) primarily in its (1)S(0) (5d(10)) electronic ground state level but with some (3)D and perhaps higher lying excited states. The distribution of states can be altered by adding N(2)O, which completely quenches the excited states, or CH(4) to the flow gases. Cross sections as a function of kinetic energy are measured for both neutral reagents and both ground and excited states of Au(+). Formation of AuO(+) is common to both systems with the N(2)O system also exhibiting AuN(2)(+) and AuNO(+) formation. All reactions of Au(+) ((1)S(0)) are observed to be endothermic, whereas the excitation energy available to the (3)D state allows some reactions to be exothermic. Because of the closed shell character of ground state Au(+) ((1)S(0), 5d(10)), the reactivity of these systems is low and has cross sections with onsets and peaks at higher energies than expected from the known thermochemistry but lower than energies expected from impulsive processes. Analyses of the endothermic reaction cross sections yield the 0 K bond dissociation energy (BDE) in eV of D(0)(Au(+)-O) = 1.12 ± 0.08, D(0)(Au(+)-N(2)) ≥ 0.30 ± 0.04, and D(0)(Au(+)-NO) = 0.89 ± 0.17, values that are all speculative because of the unusual experimental behavior. Combining the AuO(+) BDE measured here with literature data also yields the ionization energy of AuO as 10.38 ± 0.23 eV. Quantum chemical calculations show reasonable agreement with the experimental bond energies and provide the electronic structures of these species.

  9. Astatine and Yttrium Resonant Ionization Laser Spectroscopy

    NASA Astrophysics Data System (ADS)

    Teigelhoefer, Andrea

    Providing intense, contamination-free beams of rare isotopes to experiments is a challenging task. At isotope separator on-line facilities such as ISAC at TRIUMF, the choice of production target and ion source are key to the successful beam delivery. Due to their element-selectivity, high efficiency and versatility, resonant ionization laser ion sources (RILIS) gain increasingly in importance. The spectroscopic data available are typically incomplete in the region of excited- and autoionizing atomic states. In order to find the most efficient ionization scheme for a particular element, further spectroscopy is often required. The development of efficient laser resonant ionization schemes for yttrium and astatine is presented in this thesis. For yttrium, two ionization schemes with comparable relative intensities were found. Since for astatine, only two transitions were known, the focus was to provide data on atomic energy levels using resonance ionization spectroscopy. Altogether 41 previously unknown astatine energy levels were found.

  10. Vibrational structure and partial rates of resonant Auger decay ofthe N 1s ->2pi core excitations in nitric oxide

    SciTech Connect

    Kukk, Edwin; Snell, Gyorgy; Bozek, John D.; Cheng, Wei-T.; Berrah, N.

    2000-07-06

    High-resolution resonant Auger electron spectra of NO measured in the vicinity of the N 1s {yields} 2{pi} core excitations are presented. The open shell electronic configuration of the molecule results in four excited electronic states, three of which are populated in the photoabsorption spectrum, {sup 2}{Delta}, {sup 2}{Sigma}{sup -} and {sup 2}{Sigma}{sup +}. Electron emission spectra obtained at different vibrational levels of the three N 1s core-excited states of NO are reported. Recently reported ab initio calculations [J. Chem. Phys. 106, 4038(1997)] are used to generate theoretical spectra for comparison with the experimental results taking lifetime vibration interference and Auger resonant Raman effects into account. Very good agreement is found for the lowest energy X {sup 1}{Sigma}{sup +} final ionic state. Spectra of the higher energy final ionic states are decomposed into contributions from the different 5{sigma}{sup -1}2{pi}{sup 1} and 1{pi}{sup -1}2{pi}{sup 1} configurations for comparison of the calculated and experimental partial Auger decay rates. A revised value for the adiabatic ionization energy of the {sup 1}{Delta} ionic state results from the deconvolution.

  11. QED based on self-energy: The relativistic 2 S sub 1/2 r arrow 1 S sub 1/2 +1. gamma. decay rates of hydrogenlike atoms

    SciTech Connect

    Barut, A.O.; Salamin, Y.I. )

    1991-03-01

    Within the framework of the recently advanced formulation of QED based on self-energy, we calculate the relativistic rates of the 2{ital S}{sub 1/2}{r arrow}1{ital S}{sub 1/2}+1{gamma} transition in the hydrogen isoelectronic sequence for values of {ital Z} ranging between 1 and 92. We compare our results with those of Johnson (Phys. Rev. Lett. 29, 1123 (1972)) and Parpia and Johnson (Phys. Rev. A 26, 1142 (1982)), analytically and numerically. Although the two approaches are quite different, the formulas for decay rates are shown to be equivalent.

  12. Theoretical study of intermolecular energy transfer involving electronically excited molecules: He(/sup 1/S) + H/sub 2/(B /sup 1/. sigma. /sub u//sup +/). [Solution for coupled channel equations

    SciTech Connect

    Grimes, R.M.

    1986-11-01

    To further understanding of gas phase collision dynamics involving electronically-excited molecules, a fully quantum mechanical study of He + H/sub 2/(B /sup 1/..sigma../sub u//sup +/) was undertaken. Iterative natural orbital configuration interaction (CI) calculations were performed to obtain the interaction potential between He and H/sub 2/(B /sup 1/..sigma../sub u//sup +/). The potential energy surface (PES) is highly anisotropic and has a van der Waals well of about 0.03 eV for C/sub 2v/ approach. Avoided PES crossings occur with He + H/sub 2/(E,F /sup 1/..sigma../sub g//sup +/) and with He + H/sub 2/(X /sup 1/..sigma../sub g//sup +/) and cause a local maximum and a deep minimum in the He + H/sub 2/(B /sup 1/..sigma../sub u//sup +/) PES, respectively. The crossing with He + H/sub 2/(X /sup 1/..sigma../sub g//sup +/) provides a mechanism for fluorescence quenching. The computed CI energies were combined with previous multi-reference double excitation CI calculations and fit with analytic functions for convenience in scattering calculations. Accurate dipole polarizabilities and quadrupole moment of H/sub 2/(B /sup 1/..sigma../sub u//sup +/) were computed for use in the multipole expansion, which is the analytic form of the long-range PES. 129 refs., 28 figs., 35 tabs.

  13. Bis[(1S)-1 4-azanediyl-1-(9-deazaadenin-9-yl)-1 4-dideoxy-5-methylsulfanyl-D-ribitol] tetrakis(hydrochloride) monohydrate: structure DFT energy and ligand docking results of a potent methylthioadenosine phosphorylase inhibitor found in different

    SciTech Connect

    G Gainsford; G Evans; K Johnston; M Seth

    2011-12-31

    The title compound, abbreviated as 5'ThiomethylImmA, is a potent inhibitor of methylthioadenosine phosphorylase [Singh et al. (2004). Biochemistry, 43, 9-18]. The synchrotron study reported here shows that the hydrochloride salt crystallizes with two independent, nearly superimposable, dications as a monohydrate with formula 2C{sub 12}H{sub 19}N{sub 5}O{sub 2}S{sup 2+}{center_dot}4Cl{sup -}{center_dot}H{sub 2}O. Hydrogen bonding utilizing the H atoms of the dication is found to favor certain molecular conformations in the salt, which are significantly different from those found as bound in the enzyme. Ligand docking studies starting from either of these dications or related neutral structures successfully place the conformationally revised structures in the enzyme active site but only under particular hydrogen-bonding and molecular flexibility criteria. Density functional theory calculations verify the energy similarity of the indendent cations and confirm the significant energy cost of the required conformation change to the enzyme bound form. The results suggest the using crystallographically determined free ligand coordinates as starting parameters for modelling may have serious limitations.

  14. Roles of the major, small, acid-soluble spore proteins and spore-specific and universal DNA repair mechanisms in resistance of Bacillus subtilis spores to ionizing radiation from X rays and high-energy charged-particle bombardment.

    PubMed

    Moeller, Ralf; Setlow, Peter; Horneck, Gerda; Berger, Thomas; Reitz, Günther; Rettberg, Petra; Doherty, Aidan J; Okayasu, Ryuichi; Nicholson, Wayne L

    2008-02-01

    The role of DNA repair by nonhomologous end joining (NHEJ), homologous recombination, spore photoproduct lyase, and DNA polymerase I and genome protection via alpha/beta-type small, acid-soluble spore proteins (SASP) in Bacillus subtilis spore resistance to accelerated heavy ions (high-energy charged [HZE] particles) and X rays has been studied. Spores deficient in NHEJ and alpha/beta-type SASP were significantly more sensitive to HZE particle bombardment and X-ray irradiation than were the recA, polA, and splB mutant and wild-type spores, indicating that NHEJ provides an efficient DNA double-strand break repair pathway during spore germination and that the loss of the alpha/beta-type SASP leads to a significant radiosensitivity to ionizing radiation, suggesting the essential function of these spore proteins as protectants of spore DNA against ionizing radiation.

  15. Measurement of complex DNA damage induction and repair in human cellular systems after exposure to ionizing radiations of varying linear energy transfer (LET).

    PubMed

    Nikitaki, Zacharenia; Nikolov, Vladimir; Mavragani, Ifigeneia V; Mladenov, Emil; Mangelis, Anastasios; Laskaratou, Danae A; Fragkoulis, Georgios I; Hellweg, Christine E; Martin, Olga A; Emfietzoglou, Dimitris; Hatzi, Vasiliki I; Terzoudi, Georgia I; Iliakis, George; Georgakilas, Alexandros G

    2016-11-01

    Detrimental effects of ionizing radiation (IR) are correlated to the varying efficiency of IR to induce complex DNA damage. A double strand break (DSB) can be considered the simpler form of complex DNA damage. These types of damage can consist of DSBs, single strand breaks (SSBs) and/or non-DSB lesions such as base damages and apurinic/apyrimidinic (AP; abasic) sites in different combinations. Enthralling theoretical (Monte Carlo simulations) and experimental evidence suggests an increase in the complexity of DNA damage and therefore repair resistance with linear energy transfer (LET). In this study, we have measured the induction and processing of DSB and non-DSB oxidative clusters using adaptations of immunofluorescence. Specifically, we applied foci colocalization approaches as the most current methodologies for the in situ detection of clustered DNA lesions in a variety of human normal (FEP18-11-T1) and cancerous cell lines of varying repair efficiency (MCF7, HepG2, A549, MO59K/J) and radiation qualities of increasing LET, that is γ-, X-rays 0.3-1 keV/μm, α-particles 116 keV/μm and (36)Ar ions 270 keV/μm. Using γ-H2AX or 53BP1 foci staining as DSB probes, we calculated a DSB apparent rate of 5-16 DSBs/cell/Gy decreasing with LET. A similar trend was measured for non-DSB oxidized base lesions detected using antibodies against the human repair enzymes 8-oxoguanine-DNA glycosylase (OGG1) or AP endonuclease (APE1), that is damage foci as probes for oxidized purines or abasic sites, respectively. In addition, using colocalization parameters previously introduced by our groups, we detected an increasing clustering of damage for DSBs and non-DSBs. We also make correlations of damage complexity with the repair efficiency of each cell line and we discuss the biological importance of these new findings with regard to the severity of IR due to the complex nature of its DNA damage.

  16. Multiple ionization of argon by helium ions

    NASA Astrophysics Data System (ADS)

    Montanari, C. C.; Miraglia, J. E.

    2016-09-01

    We apply the continuum distorted-wave eikonal initial state and the independent electron model to describe the multiple ionization of Ar by He2+ and He+ in the energy range 0.1-10 Mev amu-1. Auger-like post collisional processes are included, which enhance the high energy multiple ionization cross sections via ionization of the inner shells. All Ar electrons (K, L and M-shells) have been included in these calculations. The results agree well with the experimental data at high energies, where the post-collisional ionization is the main contribution. At intermediate impact energies the description is also good though it tends to overestimate the triple and quadruple ionization data at intermediate energies. We analyze this by comparing the present results for He+2 in Ar, with previous ones for He+2 in Ne and Kr. It was found that the theoretical description improves from Ne to Ar and Kr, with the latter being nicely described even at intermediate energies. The present formalism is also tested for Ar inner shell and total ionization cross sections. In all the cases the results above 0.1 MeV amu-1 are quite reasonable, as compared with the experimental data available and with the ECPSSR values.

  17. Ionization potentials of seaborgium

    SciTech Connect

    Johnson, E.; Pershina, V.; Fricke, B.

    1999-10-21

    Multiconfiguration relativistic Dirac-Fock values were calculated for the first six ionization potentials of seaborgium and of the other group 6 elements. No experimental ionization potentials are available for seaborgium. Accurate experimental values are not available for all of the other ionization potentials. Ionic radii for the 4+ through 6+ ions of seaborgium are also presented. The ionization potentials and ionic radii obtained will be used to predict some physiochemical properties of seaborgium and its compounds.

  18. Evidence for the eta_b(1S) in the Decay Upsilon(2S)-> gamma eta_b(1S)

    SciTech Connect

    Aubert, B.; Bona, M.; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Prencipe, E.; Prudent, X.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Lopez, L.; Palano, A.; Pappagallo, M.; Eigen, G.; Stugu, B.; Sun, L.; Battaglia, M.; Brown, D.N.; Kerth, L.T.; Kolomensky, Yu.G.; Lynch, G.; /LBL, Berkeley /UC, Berkeley /Birmingham U. /Ruhr U., Bochum /British Columbia U. /Brunel U. /Novosibirsk, IYF /UC, Irvine /UCLA /UC, Riverside /UC, San Diego /UC, Santa Barbara /UC, Santa Cruz /Caltech /Cincinnati U. /Colorado U. /Colorado State U. /Dortmund U. /Dresden, Tech. U. /Ecole Polytechnique /Edinburgh U. /INFN, Ferrara /Ferrara U. /INFN, Ferrara /INFN, Ferrara /Ferrara U. /INFN, Ferrara /INFN, Ferrara /Ferrara U. /Frascati /INFN, Genoa /Genoa U. /INFN, Genoa /INFN, Genoa /Genoa U. /INFN, Genoa /INFN, Genoa /Genoa U. /Harvard U. /Heidelberg U. /Humboldt U., Berlin /Imperial Coll., London /Iowa U. /Iowa State U. /Johns Hopkins U. /Orsay, LAL /LLNL, Livermore /Liverpool U. /Queen Mary, U. of London /Royal Holloway, U. of London /Louisville U. /Karlsruhe U., EKP /Manchester U. /Maryland U. /Massachusetts U., Amherst /MIT, LNS /McGill U. /INFN, Milan /Milan U. /INFN, Milan /INFN, Milan /Milan U. /Mississippi U. /Montreal U. /Mt. Holyoke Coll. /INFN, Naples /Naples U. /INFN, Naples /INFN, Naples /Naples U. /NIKHEF, Amsterdam /Notre Dame U. /Ohio State U. /Oregon U. /INFN, Padua /Padua U. /INFN, Padua /INFN, Padua /Padua U. /Paris U., VI-VII /Pennsylvania U. /INFN, Perugia /Perugia U. /INFN, Pisa /Pisa U. /INFN, Pisa /Pisa, Scuola Normale Superiore /INFN, Pisa /Pisa U. /INFN, Pisa /Princeton U. /INFN, Rome /INFN, Rome /Rome U. /INFN, Rome /INFN, Rome /Rome U. /INFN, Rome /INFN, Rome /Rome U. /INFN, Rome /INFN, Rome /Rome U. /INFN, Rome /Rostock U. /Rutherford /DSM, DAPNIA, Saclay /South Carolina U. /SLAC /Stanford U., Phys. Dept. /SUNY, Albany /Tennessee U. /Texas U. /Texas U., Dallas /INFN, Turin /Turin U. /INFN, Trieste /Trieste U. /Valencia U., IFIC /Victoria U. /Warwick U. /Wisconsin U., Madison

    2009-12-14

    We have performed a search for the {eta}{sub b}(1S) meson in the radiative decay of the {Upsilon}(2S) resonance using a sample of 91.6 million {Upsilon}(2S) events recorded with the BABAR detector at the PEP-II B factory at the SLAC National Accelerator Laboratory. We observe a peak in the photon energy spectrum at E{sub {gamma}} = 610.5{sub -4.3}{sup +4.5}(stat) {+-} 1.8(syst) MeV, corresponding to an {eta}{sub b}(1S) mass of 9392.9{sub -4.8}{sup +4.6}(stat) {+-} 1.9(syst) MeV/c{sup 2}. The branching fraction for the decay {Upsilon}(2S) {yields} {gamma}{eta}{sub b}(1S) is determined to be (4.2{sub -1.0}{sup +1.1}(stat) {+-} 0.9(syst)) x 10{sup -4}. The ratio {Beta}({Upsilon}(2S) {yields} {gamma}{eta}{sub b}(1S))/{Beta}({Upsilon}(3S) {yields} {gamma}{eta}{sub b}(1S)) = 0.89{sub -0.23}{sup +0.25}(stat){sub -0.16}{sup +0.12}(syst) is consistent with the ratio expected for magnetic dipole transitions to the {eta}{sub b}(1S) meson.

  19. C 1s and N 1s core excitation of aniline: Experiment by electron impact and ab initio calculations

    SciTech Connect

    Duflot, D.; Flament, J.-P.; Giuliani, A.; Heinesch, J.; Grogna, M.; Hubin-Franskin, M.-J.

    2007-05-15

    Core shell excitation spectra of aniline at the carbon and nitrogen 1s edges have been obtained by inner-shell electron energy-loss spectroscopy recorded under scattering conditions where electric dipolar conditions dominate, with higher resolution than in the previous studies. They are interpreted with the aid of ab initio configuration interaction calculations. The spectrum at the C 1s edge is dominated by an intense {pi}{sup *} band. The calculated chemical shift due to the different chemical environment at the carbon 1s edge calculated is in agreement with the experimental observations within a few tenths of an eV. The transition energies of the most intense bands in the C 1s excitation spectrum are discussed at different levels of calculations. In the nitrogen 1s excitation spectrum the most intense bands are due to Rydberg-valence transitions involving the {sigma}{sup *}-type molecular orbitals, in agreement with the experiment. This assignment is different from that of extended Hueckel molecular orbital calculations. The geometries of the core excited states have been calculated and compared to their equivalent core molecules and benzene.

  20. High-level ab initio predictions for the ionization energy, bond dissociation energies, and heats of formation of cobalt carbide (CoC) and its cation (CoC+).

    PubMed

    Lau, Kai-Chung; Pan, Yi; Lam, Chow-Shing; Huang, Huang; Chang, Yih-Chung; Luo, Zhihong; Shi, Xiaoyu; Ng, C Y

    2013-03-07

    The ionization energy (IE) of CoC and the 0 K bond dissociation energies (D0) and the heats of formation at 0 K (ΔH°f0) and 298 K (ΔH°f298) for CoC and CoC(+) are predicted by the wavefunction based coupled-cluster theory with single, double, triple and quadruple excitations (CCSDTQ) and complete basis set (CBS) approach. The CCSDTQ∕CBS calculations presented here involve the approximation to the CBS limit at the coupled cluster level up to full quadruple excitations along with the zero-point vibrational energy, high-order correlation, core-valence (CV) electronic, spin-orbit coupling, and scalar relativistic effect corrections. The present calculations provide the correct symmetry, (1)Σ(+), for the ground state of CoC(+). The CCSDTQ∕CBS IE(CoC) = 7.740 eV is found in good agreement with the experimental IE value of 7.73467 ± 0.00007 eV, determined in a two-color laser photoion and pulsed field ionization-photoelectron study. This work together with the previous experimental and theoretical investigations support the conclusion that the CCSDTQ∕CBS method is capable of providing reliable IE predictions for 3d-transition metal carbides, such as FeC, CoC, and NiC. Among the single-reference based coupled-cluster methods and multi-reference configuration interaction (MRCI) approach, the CCSDTQ and MRCI methods give the best predictions to the harmonic frequencies ωe (ωe (+)) = 956 (992) and 976 (1004) cm(-1) and the bond lengths re (re (+)) = 1.560 (1.528) and 1.550 (1.522) Å, respectively, for CoC (CoC(+)) in comparison with the experimental values. The CCSDTQ∕CBS calculations give the prediction of D0(Co(+)-C) - D0(Co-C) = 0.175 eV, which is also consistent with the experimental determination of 0.14630 ± 0.00014 eV. The theoretical results show that the CV and valence-valence electronic correlations beyond CCSD(T) wavefunction and the relativistic effect make significant contributions to the calculated thermochemical properties of Co

  1. High-level ab initio predictions for the ionization energy, bond dissociation energies, and heats of formation of cobalt carbide (CoC) and its cation (CoC+)

    NASA Astrophysics Data System (ADS)

    Lau, Kai-Chung; Pan, Yi; Lam, Chow-Shing; Huang, Huang; Chang, Yih-Chung; Luo, Zhihong; Shi, Xiaoyu; Ng, C. Y.

    2013-03-01

    The ionization energy (IE) of CoC and the 0 K bond dissociation energies (D0) and the heats of formation at 0 K (ΔH°f0) and 298 K (ΔH°f298) for CoC and CoC+ are predicted by the wavefunction based coupled-cluster theory with single, double, triple and quadruple excitations (CCSDTQ) and complete basis set (CBS) approach. The CCSDTQ/CBS calculations presented here involve the approximation to the CBS limit at the coupled cluster level up to full quadruple excitations along with the zero-point vibrational energy, high-order correlation, core-valence (CV) electronic, spin-orbit coupling, and scalar relativistic effect corrections. The present calculations provide the correct symmetry, 1Σ+, for the ground state of CoC+. The CCSDTQ/CBS IE(CoC) = 7.740 eV is found in good agreement with the experimental IE value of 7.73467 ± 0.00007 eV, determined in a two-color laser photoion and pulsed field ionization-photoelectron study. This work together with the previous experimental and theoretical investigations support the conclusion that the CCSDTQ/CBS method is capable of providing reliable IE predictions for 3d-transition metal carbides, such as FeC, CoC, and NiC. Among the single-reference based coupled-cluster methods and multi-reference configuration interaction (MRCI) approach, the CCSDTQ and MRCI methods give the best predictions to the harmonic frequencies ωe (ωe+) = 956 (992) and 976 (1004) cm-1 and the bond lengths re (re+) = 1.560 (1.528) and 1.550 (1.522) Å, respectively, for CoC (CoC+) in comparison with the experimental values. The CCSDTQ/CBS calculations give the prediction of D0(Co+-C) - D0(Co-C) = 0.175 eV, which is also consistent with the experimental determination of 0.14630 ± 0.00014 eV. The theoretical results show that the CV and valence-valence electronic correlations beyond CCSD(T) wavefunction and the relativistic effect make significant contributions to the calculated thermochemical properties of CoC/CoC+. For the experimental D0 and ΔHof0

  2. K -shell ionization cross sections for Si, P, K, Ca, Zn, and Ga by protons and carbon ions in the energy range 1--6. 4 MeV

    SciTech Connect

    Geretschlaeger, M. ); Smit, Z. ); Benka, O. )

    1990-01-01

    Absolute {ital K}-shell ionization cross sections have been measured for thin targets of Si, P, S, K, Ca, Zn, and Ga using carbon ions between 1.0 and 6.4 MeV and protons of 1 and 2 MeV. The dependence of x-ray production cross sections on target thickness was determined. The experimental results are compared to the semiclassical approximation (Laegsgaard, Andersen, and Lund in 3 Proceedings of the Tenth International Conference on the Physics of Electron and Atomic Collisions, Paris, 1977, edited by G. Watel (North-Holland, Amsterdam 1977)), to the theory for direct Coulomb ionization of the 1{ital s}{sigma} molecular orbital (Montenegro and Sigaud, J. Phys. B. 18, 299 (1985)), to the perturbed stationary-state approximation with energy-loss, Coulomb, and relativistic corrections (ECPSSR) (Brandt and Lapicki, Phys. Rev. A 23, 1717 (1981)), and to the modification of the ECPSSR approximation (MECPSSR) (Benka, Geretschlaeger, and Paul, J. Phys. (Paris) Suppl. 12, C9-251 (1987)). The results for carbon ions are also compared to the statistical molecular orbital theory of inner-shell ionization for symmetric or nearly symmetric atomic collisions (Mittelman and Wilets, Phys. Rev. 154, 12 (1967)).

  3. Resonant effects in above-threshold ionization

    NASA Astrophysics Data System (ADS)

    Hertlein, Marcus P.

    2000-09-01

    The ionization of noble gases in high intensity laser fields produces an electron spectrum with characteristic peaks corresponding to atomic levels of the atom. While many of the features in the low energy part of the spectrum have been explained qualitatively, current models are incomplete and are not able to account for the recurrence of ionization probability for higher energy electrons. In particular, one of the basic questions arising is the importance of multiple ionization in these spectra. While the light intensities are in the regime where multiple ionization is known to occur, it was not clear whether the higher energy (or plateau) electrons are a result of this, and whether multiple ionization even leaves a signature in the electron spectrum. In this dissertation, we use several experimental techniques to explore this problem in argon. Our results show that although multiple ionization occurs, electrons from this process do not appear in the observed electron spectrum. Furthermore, the appearance intensities of the peaks visible in the plateau region of the electron spectrum and of the resonance peaks in the well- understood low energy part show a strong correlation, suggestion a common origin of production. Accurate computer simulations of the process, using a single- active-electron model, reproduce all essential features of the experimental spectra. Our results support the conclusion that all high energy electrons observed in our experiments can be explained with single-electron effects.

  4. Double-ionization satellites in the x-ray emission spectrum of Ni metal

    NASA Astrophysics Data System (ADS)

    Valenza, Ryan A.; Jahrman, Evan P.; Kas, Joshua J.; Seidler, Gerald T.

    2017-09-01

    We report measurements of the nonresonant x-ray emission spectroscopy (XES) from Ni metal in an energy range spanning the K β diagram line, valence-to-core emission, and double-ionization (DI) satellites that appear beyond the single-particle Fermi level. We make special use of a laboratory-based x-ray spectrometer capable of both x-ray emission and x-ray absorption measurements to accurately align the XES and x-ray absorption spectra to a common energy scale. The careful alignment of energy scales is requisite for correction of the strong sample absorption of DI fluorescence above the Ni K -edge energy. The successful correction of absorption effects allows a determination of the branching ratios for the [1 s 3 d ], [1 s 3 p ], [1 s 2 p ] and [1 s 2 s ] satellites with respect to their corresponding diagram lines. We compare our results with other work, finding good agreement with prior experiments and with theoretical calculations in the multiconfiguration Dirac-Fock framework.

  5. Reliability of Density Functional and Perturbation Theories for Calculating Core-Ionization Spectra of Free Radicals.

    PubMed

    Ljubić, Ivan

    2014-06-10

    The C 1s, N 1s, and O 1s ionization energies were calculated for the three stable nitroxide free radicals, viz., tempo and its two analogues, and compared to their most recent high-resolution core photoelectron spectra. We compare the performance of unrestricted and restricted open shell based ΔHF, ΔMP2, and ΔB3LYP methods. A mixed basis set is employed in all cases, which consists of the core-valence correlation-consistent triple-ζ basis set (cc-pCVTZ or cc-pwCVTZ) on the atom whose core-electron binding energy is calculated, model core potentials on the remaining first row atoms, and the cc-pVDZ basis set on the hydrogen atoms. The best overall performance for the three free radicals is offered by the restricted open shell based ΔB3LYP method. Surprisingly, both the restricted open and unrestricted second-order perturbation theories perform relatively poorly and typically do not warrant additional computational effort over the reference ΔHF methods. This is particularly true of the ΔZAPT method, which exhibits a number of grave failures that render it unsuitable for calculating the core-ionization spectra.

  6. Advanced Thin Ionization Calorimeter (ATIC)

    NASA Technical Reports Server (NTRS)

    Wefel, John P.

    1998-01-01

    This is the final report for NASA grant NAGW-4577, "Advanced Thin Ionization Calorimeter (ATIC)". This grant covered a joint project between LSU and the University of Maryland for a Concept Study of a new type of fully active calorimeter to be used to measure the energy spectra of very high energy cosmic rays, particularly Hydrogen and Helium, to beyond 1014 eV. This very high energy region has been studied with emulsion chamber techniques, but never investigated with electronic calorimeters. Technology had advanced to the point that a fully active calorimeter based upon Bismuth Germanate (BGO) scintillating crystals appeared feasible for balloon flight (and eventually space) experiments.

  7. Inner-orbital ionization of iodine

    NASA Astrophysics Data System (ADS)

    Gibson, George; Smith, Dale; Tagliamonti, Vincent; Dragan, James

    2016-05-01

    Many coincidence techniques exist to study multiple ionization of molecules by strong laser fields. However, the first ionization step is critical in many experiments, although it is more difficult to obtain information about this initial step. We studied the single electron ionization of I2, as it presents interesting opportunities in that it is heavy and does not expand significantly during the laser pulse. Moreover, there are several distinct low-lying valence orbitals from which the electron may be removed. Most importantly, the kinetic energy release of the I+ + I dissociation channel can be measured and should correspond to well-known valence levels and separated atom limits. As it turns out, we must invoke deep valence orbits, built from the 5s electrons, to explain our data. Ionization from deep orbitals may be possible, as they have a smaller critical internuclear separation for enhanced ionization. We would like to acknowledge support from the NSF under Grant No. PHY-1306845.

  8. Theoretical investigation of the origin of the multipeak structure of kinetic-energy-release spectra from charge-resonance-enhanced ionization of H{sub 2}{sup +} in intense laser fields

    SciTech Connect

    He Haixiang; Guo Yahui; Lu Ruifeng; Zhang Peiyu; Han Keli; He Guozhong

    2011-09-15

    The dynamics of hydrogen molecular ions in intense laser pulses (100 fs, I = 0.77 x 10{sup 14} W/cm{sup 2} to 2.5 x 10{sup 14} W/cm{sup 2}) has been studied, and the kinetic-energy-release spectra of Coulomb explosion channel have been calculated by numerically solving the time-dependent Schroedinger equation. In a recent experiment, a multipeak structure from charge-resonance-enhanced ionization is interpreted by a vibrational 'comb' at a critical nuclear distance. We found that the peaks could not be attributed to a single vibrational level but a collective contribution of some typical vibrational states in our calculated Coulomb explosion spectra, and the main peak shifts toward the low-energy region with increasing vibrational level, which is also different from the explanation in that experiment. We have also discussed the proton's kinetic-energy-release spectra for different durations with the same laser intensity.

  9. The photodouble ionization of the ns shell of rare gases

    NASA Astrophysics Data System (ADS)

    Argenti, L.; Bolognesi, P.; Colle, R.; Feyer, V.; Avaldi, L.

    2009-11-01

    The triple differential cross sections, TDCS, for the photodouble ionization of He, Ne, Ar and Xe leading to the He2+ (1s0 1Se), Ne2+(2s02p6 1Se), Ar2+(3s03p6 1Se)and Xe2+(5s05p6 1Se) states have been measured at about 20 eV above their respective thresholds with the two photoelectrons equally sharing the excess energy. The experimental data are analysed using a novel parametrization recently proposed. A satisfactory representation of the shape of the measured TDCS and their dependence on the increasing correlation with the principal quantum number of the ionised orbital is achieved.

  10. Fragmentation patterns of core-ionized thymine and 5-bromouracil.

    PubMed

    Itälä, E; Ha, D T; Kooser, K; Rachlew, E; Huels, M A; Kukk, E

    2010-10-21

    Photofragmentation of thymine and 5-bromouracil into cation and neutral fragments following the core ionization by soft x-rays using photoelectron-photoion-photoion coincidence technique has been studied. The fragment ion mass spectra were recorded in coincidence with the C 1s photoelectron spectra. In the case of thymine, deuterated samples were used to identify fragments. Deuteration or bromination allowed us to study not only the main fragmentation channels of these pyrimidine bases, but also to investigate if replacement of an exocyclic functional group affects molecular fragmentation. We found that the dominant fragmentation channels involve only one starting geometry, and the base ring and other bond cleavages, leading to the detected fragments, are essentially identical between thymine and 5-bromouracil. In addition, the relative intensities of the strongest fragmentation channels were determined and compared with calculated appearance energies using ab initio unrestricted Hartree-Fock theory.

  11. Angular distributions of molecular Auger electrons: The case of C 1s Auger emission in CO

    SciTech Connect

    Semenov, S. K.; Kuznetsov, V. V.; Cherepkov, N. A.; Bolognesi, P.; Feyer, V.; Lahmam-Bennani, A.; Casagrande, M. E. Staicu; Avaldi, L.

    2007-03-15

    The results of a study of the Auger-electron-photoelectron angular correlations in the case of the C 1s ionization of the CO molecule are presented and compared with theoretical calculations in the Hartree-Fock approximation based on the two-step model. The measurements have been performed at two photon energies, 305 and 318 eV, respectively, and at three angles of photoelectron emission relative to the light polarization vector: namely, 0 degree sign , 30 degree sign , and 60 degree sign . A general agreement is found between theory and experiment for the coincidence angular distributions and the relative magnitudes of the Auger-electron-photoelectron angular correlations. However, both experiment and theory show that the Auger-electron-photoelectron angular correlations are not sufficiently sensitive to the details of the Auger-electron wave function to allow a 'complete' Auger experiment in molecules. On the other hand, our calculations demonstrate that the Auger-electron angular distribution measured in the molecular frame is very sensitive to the individual contributions of different partial waves of the Auger electron. Therefore we conclude that the complete experiment for the Auger decay in molecules can be realized only measuring the Auger-electron angular distributions in the molecular frame.

  12. Multiphoton ionization of the calcium atom by linearly and circularly polarized laser fields

    SciTech Connect

    Buica, Gabriela; Nakajima, Takashi

    2010-04-15

    We theoretically study multiphoton ionization of the Ca atom irradiated by the second (photon energy 3.1 eV) and third (photon energy 4.65 eV) harmonics of Ti:sapphire laser pulses (photon energy 1.55 eV). Because of the dense energy level structure the second and third harmonics of a Ti:sapphire laser are nearly single-photon resonant with the 4s4p {sup 1}P{sup o} and 4s5p {sup 1}P{sup o} states, respectively. Although two-photon ionization takes place through the near-resonant intermediate states with the same symmetry in both cases, it turns out that there are significant differences between them. The photoelectron energy spectra exhibit the absence or presence of substructures. More interestingly, the photoelectron angular distributions clearly show that the main contribution to the ionization processes by the third harmonic arises from the far-off-resonant 4s4p {sup 1}P{sup o} state rather than the near-resonant 4s5p {sup 1}P{sup o} state. These findings can be attributed to the fact that the dipole moment for the 4s{sup 2} {sup 1}S{sup e}-4s5p {sup 1}P{sup o} transition is much smaller than that for the 4s{sup 2} {sup 1}S{sup e}-4s4p {sup 1}P{sup o} transition.

  13. Photo-double-ionization of the ns shell of rare gases

    NASA Astrophysics Data System (ADS)

    Argenti, L.; Bolognesi, P.; Colle, R.; Feyer, V.; Avaldi, L.

    2009-06-01

    The triple differential cross sections (TDCS) for the photodouble ionization of He, Ne, Ar, and Xe leading to the He2+(1s0S1e) , Ne2+(2s02p6S1e) , Ar2+(3s03p6S1e) , and Xe2+(5s05p6S1e) states have been measured at about 20 eV above their respective thresholds with the two photoelectrons equally sharing the excess energy. The experimental data are analyzed using a parametrization recently proposed [J. Phys. B 41, 245205 (2008)] which takes into account experimental uncertainties. The parametrization provides a satisfactory representation of the shape of the measured TDCS. The study of the behavior of the gerade amplitude of the TDCS in the different targets gives hints on the dependence of the electron correlation with the principal quantum number n of the ionized ns orbital.

  14. Intracluster reactions in phenylacetylene ammonia clusters initiated through resonant enhanced ionization

    SciTech Connect

    Breen, J.J.; Tzeng, W.; Kilgore, K.; Keesee, R.G.; Castleman A.W. Jr.

    1989-01-01

    Protonated ammonia clusters of specific size are observed to form following the resonant enhanced ionization of phenylacetylene--ammonia clusters PAx(NH/sub 3/)/sub n/ in the 0/sup 0//sub 0/ region of the S/sub 1/--S/sub 0/ transition of the (unclustered) PA. The resonance enhanced absorption of two photons, approx. =8.8 eV total energy, are found to cause intracluster reactions for ngreater than or equal to5. The findings imply that the adiabatic ionization potential of (NH/sub 3/)/sub 4/ is greater than 8.8 eV, while that of (NH/sub 3/)/sub 5/ is (slightly) less.

  15. Fluctuations of induced charge in ionization detectors

    SciTech Connect

    Samedov, V. V.

    2016-12-15

    Fluctuations of charge induced by charge carriers on the detector electrodes make a significant contribution to the energy resolution of ionization detectors, namely, semiconductor detectors and gas and liquid ionization chambers. These fluctuations are determined by the capture of charge carriers, as they drift in the bulk of the detector under the action of an electric field, by traps. In this study, we give a correct mathematical description of charge induction on electrodes of an ionization detector for an arbitrary electric field distribution in the detector with consideration of charge carrier capture by traps. The characteristic function obtained in this study yields the general expression for the distribution function of the charge induced on the detector electrodes. The formulas obtained in this study are useful for analysis of the influence of charge carrier transport on energy resolution of ionization detectors.

  16. Ionization of excited xenon atoms by electrons

    NASA Astrophysics Data System (ADS)

    Erwin, Daniel A.; Kunc, Joseph A.

    2004-08-01

    Measured cross sections for electron-impact ionization of excited Xe atoms are not presently available. Therefore, we combine in this work the formalisms of the binary encounter approximation and Sommerfeld’s quantization of atomic orbits and derive from first-principles cross sections for ionization of excited atoms by electrons of low and moderate energies (up to a few hundred eV ). The approach of this work can be used to calculate the cross sections for electron-impact ionization of excited atoms and atomic ions other than xenon.

  17. Epicyclic Twin-Helix Ionization Cooling Simulations

    SciTech Connect

    Vasiliy Morozov, Yaroslav Derbenev, A. Afanaciev, R.P. Johnson

    2011-04-01

    Parametric-resonance Ionization Cooling (PIC) is proposed as the final 6D cooling stage of a highluminosity muon collider. For the implementation of PIC, we earlier developed an epicyclic twin-helix channel with correlated behavior of the horizontal and vertical betatron motions and dispersion. We now insert absorber plates with short energy-recovering units located next to them at the appropriate locations in the twin-helix channel. We first demonstrate conventional ionization cooling in such a system with the optics uncorrelated. We then adjust the correlated optics state and induce a parametric resonance to study ionization cooling under the resonant condition.

  18. Analytical instruments, ionization sources, and ionization methods

    DOEpatents

    Atkinson, David A.; Mottishaw, Paul

    2006-04-11

    Methods and apparatus for simultaneous vaporization and ionization of a sample in a spectrometer prior to introducing the sample into the drift tube of the analyzer are disclosed. The apparatus includes a vaporization/ionization source having an electrically conductive conduit configured to receive sample particulate which is conveyed to a discharge end of the conduit. Positioned proximate to the discharge end of the conduit is an electrically conductive reference device. The conduit and the reference device act as electrodes and have an electrical potential maintained between them sufficient to cause a corona effect, which will cause at least partial simultaneous ionization and vaporization of the sample particulate. The electrical potential can be maintained to establish a continuous corona, or can be held slightly below the breakdown potential such that arrival of particulate at the point of proximity of the electrodes disrupts the potential, causing arcing and the corona effect. The electrical potential can also be varied to cause periodic arcing between the electrodes such that particulate passing through the arc is simultaneously vaporized and ionized. The invention further includes a spectrometer containing the source. The invention is particularly useful for ion mobility spectrometers and atmospheric pressure ionization mass spectrometers.

  19. Ground electronic states of RbO2+, CsO2+ and FrO2: the ionization energies of RbO2 and CsO2.

    PubMed

    Lee, Edmond P F; Wright, Timothy G

    2005-04-14

    Calculations are performed to establish the ground electronic states of RbO2+, CsO2+, and FrO2. In the case of the cations, both linear and C2v orientations were considered; for FrO2, the two lowest electronic states, 2A2 and 2B2, were considered in C2v symmetry. In addition, calculations were also performed on the x2 A2 ground states of RbO2 and CsO2 to derive ionization energies. Binding energies and heats of formation are also derived. The bonding in FrO2 is found to be less ionic than that of RbO2 and CsO2.

  20. Electron-impact ionization of ozone

    NASA Astrophysics Data System (ADS)

    Newson, Karl A.; Luc, Stephanie M.; Price, Stephen D.; Mason, Nigel J.

    1995-10-01

    Partial electron ionization cross-sections of ozone for incident electron energies from 40 to 500 eV have been determined using time-of-flight mass spectrometry. The cross-sections are derived by identifying the contribution of ozone to the ion signals recorded following ionization of a mixture of O2 and O3. Only one previous determination of these cross-sections, for energies up to 100 eV, is available in the literature. The cross-sections derived in the present study at these lower electron energies are in good agreement with the previous determination.