WorldWideScience

Sample records for strong ionization results

  1. Identifying the Tunneling Site in Strong-Field Ionization of H_{2}^{+}.

    Science.gov (United States)

    Liu, Kunlong; Barth, Ingo

    2017-12-15

    The tunneling site of the electron in a molecule exposed to a strong laser field determines the initial position of the ionizing electron and, as a result, has a large impact on the subsequent ultrafast electron dynamics on the polyatomic Coulomb potential. Here, the tunneling site of the electron of H_{2}^{+} ionized by a strong circularly polarized (CP) laser pulse is studied by numerically solving the time-dependent Schrödinger equation. We show that the electron removed from the down-field site is directly driven away by the CP field and the lateral photoelectron momentum distribution (LPMD) exhibits a Gaussian-like distribution, whereas the corresponding LPMD of the electron removed from the up-field site differs from the Gaussian shape due to the Coulomb focusing and scattering by the down-field core. Our current study presents the direct evidence clarifying a long-standing controversy over the tunneling site in H_{2}^{+} and raises the important role of the tunneling site in strong-field molecular ionization.

  2. Classical trajectory perspective of atomic ionization in strong laser fields. Semiclassical modeling

    International Nuclear Information System (INIS)

    Liu, Jie

    2014-01-01

    Dealing with timely and interesting issues in strong laser physics. Illustrates complex strong field atomic ionization with the simple semiclassical model of classical trajectory perspective for the first time. Provides a theoretical model that can be used to account for recent experiments. The ionization of atoms and molecules in strong laser fields is an active field in modern physics and has versatile applications in such as attosecond physics, X-ray generation, inertial confined fusion (ICF), medical science and so on. Classical Trajectory Perspective of Atomic Ionization in Strong Laser Fields covers the basic concepts in this field and discusses many interesting topics using the semiclassical model of classical trajectory ensemble simulation, which is one of the most successful ionization models and has the advantages of a clear picture, feasible computing and accounting for many exquisite experiments quantitatively. The book also presents many applications of the model in such topics as the single ionization, double ionization, neutral atom acceleration and other timely issues in strong field physics, and delivers useful messages to readers with presenting the classical trajectory perspective on the strong field atomic ionization. The book is intended for graduate students and researchers in the field of laser physics, atom molecule physics and theoretical physics. Dr. Jie Liu is a professor of Institute of Applied Physics and Computational Mathematics, China and Peking University.

  3. Spin and Angular Momentum in Strong-Field Ionization

    Science.gov (United States)

    Trabert, D.; Hartung, A.; Eckart, S.; Trinter, F.; Kalinin, A.; Schöffler, M.; Schmidt, L. Ph. H.; Jahnke, T.; Kunitski, M.; Dörner, R.

    2018-01-01

    The spin polarization of electrons from multiphoton ionization of Xe by 395 nm circularly polarized laser pulses at 6 ×1013 W /cm2 has been measured. At this photon energy of 3.14 eV the above-threshold ionization peaks connected to Xe+ ions in the ground state (J =3 /2 , ionization potential Ip=12.1 eV ) and the first excited state (J =1 /2 , Ip=13.4 eV ) are clearly separated in the electron energy distribution. These two combs of above-threshold ionization peaks show opposite spin polarizations. The magnitude of the spin polarization is a factor of 2 higher for the J =1 /2 than for the J =3 /2 final ionic state. In turn, the data show that the ionization probability is strongly dependent on the sign of the magnetic quantum number.

  4. Dynamics of dissociation versus ionization in strong laser fields

    International Nuclear Information System (INIS)

    DiMauro, L.F.; Yang, B.

    1993-01-01

    In this paper, experimental results are presented which clearly demonstrate the effectiveness that an external field has in altering the dissociation dynamics. The experiment examines the strong-field dissociation dynamics of molecular hydrogen ions and its deuterated isotopes. These studies involve multiphoton excitation in the intensity regime of 10 11-14 W/cm 2 with the fundamental and second harmonic of a ND:YAG or ND:YLF laser system. Measurements include energy resolved electron and mass spectroscopy which provide useful probes in elucidating the interaction dynamics predicted by existing models. The example this in this paper, examines the strong-field dissociation of H 2 + , HD + , and D 2 + at green (0.5 μm) and (1μm) frequencies. The diatomic ions are formed via multiphonon ionization of the neutral precursor which is physically separable from the dissociation process. This study provides the first observation of the dynamics associated with the above threshold dissociation (ATD) process and analogies will be made with the more familiar above threshold ionization (ATI) phenomenon

  5. Angle-dependent strong-field molecular ionization rates with tuned range-separated time-dependent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Sissay, Adonay [Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Abanador, Paul; Mauger, François; Gaarde, Mette; Schafer, Kenneth J. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Lopata, Kenneth, E-mail: klopata@lsu.edu [Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Center for Computation and Technology, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)

    2016-09-07

    Strong-field ionization and the resulting electronic dynamics are important for a range of processes such as high harmonic generation, photodamage, charge resonance enhanced ionization, and ionization-triggered charge migration. Modeling ionization dynamics in molecular systems from first-principles can be challenging due to the large spatial extent of the wavefunction which stresses the accuracy of basis sets, and the intense fields which require non-perturbative time-dependent electronic structure methods. In this paper, we develop a time-dependent density functional theory approach which uses a Gaussian-type orbital (GTO) basis set to capture strong-field ionization rates and dynamics in atoms and small molecules. This involves propagating the electronic density matrix in time with a time-dependent laser potential and a spatial non-Hermitian complex absorbing potential which is projected onto an atom-centered basis set to remove ionized charge from the simulation. For the density functional theory (DFT) functional we use a tuned range-separated functional LC-PBE*, which has the correct asymptotic 1/r form of the potential and a reduced delocalization error compared to traditional DFT functionals. Ionization rates are computed for hydrogen, molecular nitrogen, and iodoacetylene under various field frequencies, intensities, and polarizations (angle-dependent ionization), and the results are shown to quantitatively agree with time-dependent Schrödinger equation and strong-field approximation calculations. This tuned DFT with GTO method opens the door to predictive all-electron time-dependent density functional theory simulations of ionization and ionization-triggered dynamics in molecular systems using tuned range-separated hybrid functionals.

  6. Angle-dependent strong-field molecular ionization rates with tuned range-separated time-dependent density functional theory

    International Nuclear Information System (INIS)

    Sissay, Adonay; Abanador, Paul; Mauger, François; Gaarde, Mette; Schafer, Kenneth J.; Lopata, Kenneth

    2016-01-01

    Strong-field ionization and the resulting electronic dynamics are important for a range of processes such as high harmonic generation, photodamage, charge resonance enhanced ionization, and ionization-triggered charge migration. Modeling ionization dynamics in molecular systems from first-principles can be challenging due to the large spatial extent of the wavefunction which stresses the accuracy of basis sets, and the intense fields which require non-perturbative time-dependent electronic structure methods. In this paper, we develop a time-dependent density functional theory approach which uses a Gaussian-type orbital (GTO) basis set to capture strong-field ionization rates and dynamics in atoms and small molecules. This involves propagating the electronic density matrix in time with a time-dependent laser potential and a spatial non-Hermitian complex absorbing potential which is projected onto an atom-centered basis set to remove ionized charge from the simulation. For the density functional theory (DFT) functional we use a tuned range-separated functional LC-PBE*, which has the correct asymptotic 1/r form of the potential and a reduced delocalization error compared to traditional DFT functionals. Ionization rates are computed for hydrogen, molecular nitrogen, and iodoacetylene under various field frequencies, intensities, and polarizations (angle-dependent ionization), and the results are shown to quantitatively agree with time-dependent Schrödinger equation and strong-field approximation calculations. This tuned DFT with GTO method opens the door to predictive all-electron time-dependent density functional theory simulations of ionization and ionization-triggered dynamics in molecular systems using tuned range-separated hybrid functionals.

  7. Hole dynamics and spin currents after ionization in strong circularly polarized laser fields

    International Nuclear Information System (INIS)

    Barth, Ingo; Smirnova, Olga

    2014-01-01

    We apply the time-dependent analytical R-matrix theory to develop a movie of hole motion in a Kr atom upon ionization by strong circularly polarized field. We find rich hole dynamics, ranging from rotation to swinging motion. The motion of the hole depends on the final energy and the spin of the photoelectron and can be controlled by the laser frequency and intensity. Crucially, hole rotation is a purely non-adiabatic effect, completely missing in the framework of quasistatic (adiabatic) tunneling theories. We explore the possibility to use hole rotation as a clock for measuring ionization time. Analyzing the relationship between the relative phases in different ionization channels we show that in the case of short-range electron-core interaction the hole is always initially aligned along the instantaneous direction of the laser field, signifying zero delays in ionization. Finally, we show that strong-field ionization in circular fields creates spin currents (i.e. different flow of spin-up and spin-down density in space) in the ions. This phenomenon is intimately related to the production of spin-polarized electrons in strong laser fields Barth and Smirnova (2013 Phys. Rev. A 88 013401). We demonstrate that rich spin dynamics of electrons and holes produced during strong field ionization can occur in typical experimental conditions and does not require relativistic intensities or strong magnetic fields. (paper)

  8. Tunneling Time and Weak Measurement in Strong Field Ionization.

    Science.gov (United States)

    Zimmermann, Tomáš; Mishra, Siddhartha; Doran, Brent R; Gordon, Daniel F; Landsman, Alexandra S

    2016-06-10

    Tunneling delays represent a hotly debated topic, with many conflicting definitions and little consensus on when and if such definitions accurately describe the physical observables. Here, we relate these different definitions to distinct experimental observables in strong field ionization, finding that two definitions, Larmor time and Bohmian time, are compatible with the attoclock observable and the resonance lifetime of a bound state, respectively. Both of these definitions are closely connected to the theory of weak measurement, with Larmor time being the weak measurement value of tunneling time and Bohmian trajectory corresponding to the average particle trajectory, which has been recently reconstructed using weak measurement in a two-slit experiment [S. Kocsis, B. Braverman, S. Ravets, M. J. Stevens, R. P. Mirin, L. K. Shalm, and A. M. Steinberg, Science 332, 1170 (2011)]. We demonstrate a big discrepancy in strong field ionization between the Bohmian and weak measurement values of tunneling time, and we suggest this arises because the tunneling time is calculated for a small probability postselected ensemble of electrons. Our results have important implications for the interpretation of experiments in attosecond science, suggesting that tunneling is unlikely to be an instantaneous process.

  9. Complete single ionization momentum spectra for strong perturbation collisions

    International Nuclear Information System (INIS)

    Olson, R.E.; Wood, C.J.

    1997-09-01

    The combination of recoil ion and ionized electron momentum spectroscopy provides an unparalleled method to investigate the details of ion-atom collision dynamics in kinematically complete experiments. To predict singleionization scattering behavior at the level now realized by experiment, the classical trajectory three-body Monte Carlo method has been used to obtain complete momenta information for the ionized electron, recoil ion, and projectile in the collision plane defined by the incident projectile and outgoing recoil ion. Strongly coupled systems were considered where the charge state of the projectile divided by the speed of the collision q/v is greater than unity. Illustrated are 3.6 MeV/u Se 28+ and 9.5 MeV/u Ni 26+ collisions on He where experimental data are available. The theoretical results are in good agreement with these data and calculations have been performed for 165 keV/u and 506 keV/u C 6+ +He to compare results for the same q/v perturbation strengths. (orig.)

  10. Spin dynamics in relativistic ionization with highly charged ions in super-strong laser fields

    International Nuclear Information System (INIS)

    Klaiber, Michael; Yakaboylu, Enderalp; Bauke, Heiko; Hatsagortsyan, Karen Z; Müller, Carsten; Paulus, Gerhard G

    2014-01-01

    Spin dynamics and induced spin effects in above-threshold ionization of hydrogenlike highly charged ions in super-strong laser fields are investigated. Spin-resolved ionization rates in the tunnelling regime are calculated by employing two versions of a relativistic Coulomb-corrected strong-field approximation (SFA). An intuitive simpleman model is developed which explains the derived scaling laws for spin flip and spin asymmetry effects. The intuitive model as well as our ab initio numerical simulations support the analytical results for the spin effects obtained in the dressed SFA where the impact of the laser field on the electron spin evolution in the bound state is taken into account. In contrast, the standard SFA is shown to fail in reproducing spin effects in ionization even at a qualitative level. The anticipated spin-effects are expected to be measurable with modern laser techniques combined with an ion storage facility. (paper)

  11. Keldysh theory of strong field ionization: history, applications, difficulties and perspectives

    International Nuclear Information System (INIS)

    V Popruzhenko, S

    2014-01-01

    The history and current status of the Keldysh theory of strong field ionization are reviewed. The focus is on the fundamentals of the theory, its most important applications and those aspects which still raise difficulties and remain under discussion. The Keldysh theory is compared with other nonperturbative analytic methods of strong field atomic physics and its important generalizations are discussed. Among the difficulties, the gauge invariance problem, the tunneling time concept, the conditions of applicability and the application of the theory to ionization of systems more complex than atoms, including molecules and dielectrics, are considered. Possible prospects for the future development of the theory are also discussed. (review article)

  12. Recent attoclock measurements of strong field ionization

    International Nuclear Information System (INIS)

    Pfeiffer, Adrian N.; Cirelli, Claudio; Smolarski, Mathias; Keller, Ursula

    2013-01-01

    Highlights: ► The attoclock measures time by electron streaking with elliptically polarized light. ► Precision measurements reveal details about the laser-induced tunneling current flow. ► Multielectron effects play an important role when the polarizability is large. ► Double ionization experiments show evidence of novel electron correlation mechanisms. - Abstract: The attoclock is a powerful, new, and unconventional experimental tool to study fundamental attosecond dynamics on an atomic scale. We have demonstrated the first attoclock with the goal to measure the tunneling delay time in laser-induced ionization of helium and argon atoms, with surprising results. It was found that the time delay in tunneling is zero for helium and argon atoms within the experimental uncertainties of a few 10’s of attoseconds. Furthermore we showed that the single active electron approximation is not sufficient even for atoms such as argon and the parent-ion interaction is much more complex than normally assumed. For double ionization of argon we found again surprising results because the ionization time of the first electron is in good agreement with the predictions, whereas the ionization of the second electron occurs significantly earlier than predicted and the two electrons exhibit some unexpected correlation

  13. Recent attoclock measurements of strong field ionization

    Energy Technology Data Exchange (ETDEWEB)

    Pfeiffer, Adrian N., E-mail: apfeiff@phys.ethz.ch [Physics Department, ETH Zurich, 8093 Zurich (Switzerland); Cirelli, Claudio; Smolarski, Mathias; Keller, Ursula [Physics Department, ETH Zurich, 8093 Zurich (Switzerland)

    2013-03-12

    Highlights: ► The attoclock measures time by electron streaking with elliptically polarized light. ► Precision measurements reveal details about the laser-induced tunneling current flow. ► Multielectron effects play an important role when the polarizability is large. ► Double ionization experiments show evidence of novel electron correlation mechanisms. - Abstract: The attoclock is a powerful, new, and unconventional experimental tool to study fundamental attosecond dynamics on an atomic scale. We have demonstrated the first attoclock with the goal to measure the tunneling delay time in laser-induced ionization of helium and argon atoms, with surprising results. It was found that the time delay in tunneling is zero for helium and argon atoms within the experimental uncertainties of a few 10’s of attoseconds. Furthermore we showed that the single active electron approximation is not sufficient even for atoms such as argon and the parent-ion interaction is much more complex than normally assumed. For double ionization of argon we found again surprising results because the ionization time of the first electron is in good agreement with the predictions, whereas the ionization of the second electron occurs significantly earlier than predicted and the two electrons exhibit some unexpected correlation.

  14. Multiphoton ionization processes in strong laser

    International Nuclear Information System (INIS)

    Krstic, P.

    1982-01-01

    Multiphoton ionization of hydrogen in ultrastrong laser fields is studied. The previous calculations of this process yield differing result for the transition rate. We show the relations between them and difficulties with each of them. One difficulty is that the finite spatial and time extent of the laser field has been omitted. It is also found that a laser field, which is sufficiently intense to be labeled ultrastrong, makes the electron move relativistically so that it becomes necessary to use Volkov states to describe the electron in the laser field. The transition rate is obtained, using a CO laser as an example, and it is found that the transition rate rises as the laser intensity rises. This is a consequence of the use of relativistic kinematics and is not true nonrelativistically. We also discuss the multiple peaks observed in the energy spectrum of electrons resulting from multiphoton ionization of atoms by lasers. When the laser intensity is large enough for the ponderomotive force to result in appreciable broading of the peaks we show the shape of the broadened peaks contains useful information. We show that the multiphoton ionization probability as a function of laser intensity can be obtained but that the free-free cross sections, which are in principle also obtainable, are probably not obtainable in practice. Finally, we describe the theory of the absorption of more than minimum numbers of photons needed to ionize an atom by an intense laser. The basic approximation used is that the atom is adiabatically deformed by the laser and an impulsive interaction then results in multiphoton absorption. In our first calculation we allow only one resonant excited state to be included in the adiabatic deformation. In our second we also allow the lowest energy continuum to be included. The two results are then compared

  15. Quantum entanglement in strong-field ionization

    Science.gov (United States)

    Majorosi, Szilárd; Benedict, Mihály G.; Czirják, Attila

    2017-10-01

    We investigate the time evolution of quantum entanglement between an electron, liberated by a strong few-cycle laser pulse, and its parent ion core. Since the standard procedure is numerically prohibitive in this case, we propose a method to quantify the quantum correlation in such a system: we use the reduced density matrices of the directional subspaces along the polarization of the laser pulse and along the transverse directions as building blocks for an approximate entanglement entropy. We present our results, based on accurate numerical simulations, in terms of several of these entropies, for selected values of the peak electric-field strength and the carrier-envelope phase difference of the laser pulse. The time evolution of the mutual entropy of the electron and the ion-core motion along the direction of the laser polarization is similar to our earlier results based on a simple one-dimensional model. However, taking into account also the dynamics perpendicular to the laser polarization reveals a surprisingly different entanglement dynamics above the laser intensity range corresponding to pure tunneling: the quantum entanglement decreases with time in the over-the-barrier ionization regime.

  16. Internuclear Separation Dependent Ionization of the Valence Orbitals of I2 by Strong Laser Fields

    Science.gov (United States)

    Chen, H.; Tagliamonti, V.; Gibson, G. N.

    2012-11-01

    Using a pump-dump-probe technique and Fourier-transform spectroscopy, we study the internuclear separation R dependence and relative strength of the ionization rates of the π and σ electrons of I2, whose valence orbitals are σg2πu4πg4σu0. We find that ionization of the highest occupied molecular orbital (HOMO)-2 (σg) has a strong dependence on R while the HOMO and HOMO-1 do not. Surprisingly, the ionization rate of the HOMO-2 exceeds the combined ionization rate of the less bound orbitals and this branching ratio increases with R. Since our technique produces target molecules that are highly aligned with the laser polarization, the σ orbitals will be preferentially ionized and undergo enhanced ionization at larger R compared to the π orbitals. Nevertheless, it is highly unusual that an inner orbital provides the dominant strong field ionization pathway in a small molecule.

  17. Unraveling nonadiabatic ionization and Coulomb potential effect in strong-field photoelectron holography.

    Science.gov (United States)

    Song, Xiaohong; Lin, Cheng; Sheng, Zhihao; Liu, Peng; Chen, Zhangjin; Yang, Weifeng; Hu, Shilin; Lin, C D; Chen, Jing

    2016-06-22

    Strong field photoelectron holography has been proposed as a means for interrogating the spatial and temporal information of electrons and ions in a dynamic system. After ionization, part of the electron wave packet may directly go to the detector (the reference wave), while another part may be driven back and scatters off the ion(the signal wave). The interference hologram of the two waves may be used to extract target information embedded in the collision process. Unlike conventional optical holography, however, propagation of the electron wave packet is affected by the Coulomb potential as well as by the laser field. In addition, electrons are emitted over the whole laser pulse duration, thus multiple interferences may occur. In this work, we used a generalized quantum-trajectory Monte Carlo method to investigate the effect of Coulomb potential and the nonadiabatic subcycle ionization on the photoelectron hologram. We showed that photoelectron hologram can be well described only when the effect of nonadiabatic ionization is accounted for, and Coulomb potential can be neglected only in the tunnel ionization regime. Our results help paving the way for establishing photoelectron holography for probing spatial and dynamic properties of atoms and molecules.

  18. Fast Atom Ionization in Strong Electromagnetic Radiation

    Science.gov (United States)

    Apostol, M.

    2018-05-01

    The Goeppert-Mayer and Kramers-Henneberger transformations are examined for bound charges placed in electromagnetic radiation in the non-relativistic approximation. The consistent inclusion of the interaction with the radiation field provides the time evolution of the wavefunction with both structural interaction (which ensures the bound state) and electromagnetic interaction. It is shown that in a short time after switching on the high-intensity radiation the bound charges are set free. In these conditions, a statistical criterion is used to estimate the rate of atom ionization. The results correspond to a sudden application of the electromagnetic interaction, in contrast with the well-known ionization probability obtained by quasi-classical tunneling through classically unavailable non-stationary states, or other equivalent methods, where the interaction is introduced adiabatically. For low-intensity radiation the charges oscillate and emit higher-order harmonics, the charge configuration is re-arranged and the process is resumed. Tunneling ionization may appear in these circumstances. Extension of the approach to other applications involving radiation-induced charge emission from bound states is discussed, like ionization of molecules, atomic clusters or proton emission from atomic nuclei. Also, results for a static electric field are included.

  19. Ionizing gas breakdown waves in strong electric fields.

    Science.gov (United States)

    Klingbeil, R.; Tidman, D. A.; Fernsler, R. F.

    1972-01-01

    A previous analysis by Albright and Tidman (1972) of the structure of an ionizing potential wave driven through a dense gas by a strong electric field is extended to include atomic structure details of the background atoms and radiative effects, especially, photoionization. It is found that photoionization plays an important role in avalanche propagation. Velocities, electron densities, and temperatures are presented as a function of electric field for both negative and positive breakdown waves in nitrogen.

  20. Strong eld ionization of naphthalene: angular shifts and molecular potential

    DEFF Research Database (Denmark)

    Dimitrovski, Darko; Maurer, Jochen; Christensen, Lauge

    We analyze the photoelectron momentum distributions from strong eld ionization of xed-in-space naphthalene molecules by circularly polarized laser pulses. By direct comparison between experiment and theory, we show that the angular shifts in the photoelectron momentum distributions are very...... sensitive to the exact form of the molecular potential....

  1. Footprints of electron correlation in strong-field double ionization of Kr close to the sequential-ionization regime

    Science.gov (United States)

    Li, Xiaokai; Wang, Chuncheng; Yuan, Zongqiang; Ye, Difa; Ma, Pan; Hu, Wenhui; Luo, Sizuo; Fu, Libin; Ding, Dajun

    2017-09-01

    By combining kinematically complete measurements and a semiclassical Monte Carlo simulation we study the correlated-electron dynamics in the strong-field double ionization of Kr. Interestingly, we find that, as we step into the sequential-ionization regime, there are still signatures of correlation in the two-electron joint momentum spectrum and, more intriguingly, the scaling law of the high-energy tail is completely different from early predictions on the low-Z atom (He). These experimental observations are well reproduced by our generalized semiclassical model adapting a Green-Sellin-Zachor potential. It is revealed that the competition between the screening effect of inner-shell electrons and the Coulomb focusing of nuclei leads to a non-inverse-square central force, which twists the returned electron trajectory at the vicinity of the parent core and thus significantly increases the probability of hard recollisions between two electrons. Our results might have promising applications ranging from accurately retrieving atomic structures to simulating celestial phenomena in the laboratory.

  2. Ion-sound oscillations in strongly non-isotherm weakly ionized nonuniform hydrogen plasma

    International Nuclear Information System (INIS)

    Leleko, Ya.F.; Stepanov, K.N.

    2010-01-01

    A stationary distribution of strongly non-isotherm weakly ionized hydrogen plasma parameters is obtained in the hydrodynamic approximation in a quasi neutrality region in the transient layer between the plasma and dielectric taking the ionization, charge exchange, diffusion, viscosity, and a self-consistent field potential distribution. The ion-sound oscillation frequency and the collisional damping decrement as functions of the wave vector in the plasma with the obtained parameters are found in the local approximation.

  3. Self-probing spectroscopy of XUV photo-ionization dynamics in atoms subjected to a strong-field environment.

    Science.gov (United States)

    Azoury, Doron; Krüger, Michael; Orenstein, Gal; Larsson, Henrik R; Bauch, Sebastian; Bruner, Barry D; Dudovich, Nirit

    2017-11-13

    Single-photon ionization is one of the most fundamental light matter interactions in nature, serving as a universal probe of the quantum state of matter. By probing the emitted electron, one can decode the full dynamics of the interaction. When photo-ionization is evolving in the presence of a strong laser field, the fundamental properties of the mechanism can be signicantly altered. Here we demonstrate how the liberated electron can perform a self-probing measurement of such interaction with attosecond precision. Extreme ultraviolet attosecond pulses initiate an electron wavepacket by photo-ionization, a strong infrared field controls its motion, and finally electron-ion collision maps it into re-emission of attosecond radiation bursts. Our measurements resolve the internal clock provided by the self-probing mechanism, obtaining a direct insight into the build-up of photo-ionization in the presence of the strong laser field.

  4. Theory of strong-field ionization of aligned CO2

    DEFF Research Database (Denmark)

    Abu-Samha, Mahmoud; Madsen, Lars Bojer

    2009-01-01

    resonance states, and the alignment-dependent ionization yields do not follow the electron density of the initial states. The theory explains the breakdown of semianalytical theories, such as the molecular tunneling theory and strong-field approximation, where excited electronic structure is neglected....

  5. Ionization, photoelectron dynamics and elastic scattering in relativistic, ultra-strong field

    Science.gov (United States)

    Luo, Sui

    Ultrastrong laser-matter interaction has direct bearing to next generation technologies including plasma acceleration, laser fusion and attosecond X-ray generation. The commonly known physics in strong field becomes different as one progress to ultrastrong field. The works presented in this dissertation theoretically study the influence of relativistic effect and magnetic component of the laser field on the ionization, photoelectron dynamics and elastic scattering processes. The influence of magnetic component (B laser) of circularly polarized (CP) ultrastrong fields (up to3 x 1022 W/cm2) on atomic bound state dynamics is investigated. The Poincare plots are used to find the changes in trajectory energies are on the order of a few percent for intensities up to1 x 1022 W/cm2. It is found that at intensities where ionization approaches 50% for the bound state, the small changes from Blaser of the circular polarized light can actually result in a several-fold decrease in ionization probability. The force on the bound electron exerted by the Lorentz force from B laser is perpendicular to the rotating plane of the circular polarized light, and this nature makes those trajectories which are aligned away from the minimum in the potential barrier stabilized against tunneling ionization. Our results provide a classical understanding for ionization in ultrastrong fields and indicate that relativistic effects in ultrastrong field ionization may most easily be seen with CP fields. The photoelectron energy spectra from elastic rescattering in ultrastrong laser fields (up to 2x1019 W/cm2) is studied by using a relativistic adaption of a semi-classical three-step recollision model. The Hartree-Fock scattering potentials are used in calculating the elastic rescattering for both hydrogenlike and noble gas species. It is found that there is a reduction in elastic rescattering for intensities beyond 6 x 1016 W/cm2 when the laser Lorentz deflection of the photoelectron exceeds its

  6. Studies of the wavelength dependence of non-sequential double ionization of xenon in strong fields

    International Nuclear Information System (INIS)

    Kaminski, P.; Wiehle, R.; Kamke, W.; Helm, H.; Witzele, B.

    2005-01-01

    Full text: The non-sequential double ionization of noble gases in strong fields is still a process which is not completely understood. The most challenging question is: what is the dominant physical process behind the knee structure in the yield of doubly charged ions which are produced in the focus of an ultrashort laser pulse in dependence of the intensity? Numerous studies can be explained with the so-called rescattering model, where an electron is freed by the strong laser field and then driven back to its parent ion due to the oscillation of the field. Through this backscattering process it is possible to kick out a second electron. However in the low intensity or multiphoton (MPI) region this model predicts that the first electron can not gain enough energy in the oscillating electric field to further ionize or excite the ion. We present experimental results for xenon in the MPI region which show a significant contribution of doubly charged ions. A Ti:sapphire laser system (800 nm, 100 fs) is used to ionize the atoms. The coincident detection of the momentum distribution of the photoelectrons with an imaging spectrometer and the time of flight spectrum of the ions allows a detailed view into the ionization process. For the first time we also show a systematic study of the wavelength dependence (780-830 nm and 1180-1550 nm) on the non-sequential double ionization. The ratio Xe 2+ /Xe + shows a surprising oscillatory behavior with varying wavelength. Ref. 1 (author)

  7. Strong-field ionization of xenon dimers: The effect of two-equivalent-center interference and of driving ionic transitions

    Science.gov (United States)

    Zhang, C.; Feng, T.; Raabe, N.; Rottke, H.

    2018-02-01

    Strong-field ionization (SFI) of the homonuclear noble gas dimer Xe2 is investigated and compared with SFI of the Xe atom and of the ArXe heteronuclear dimer by using ultrashort Ti:sapphire laser pulses and photoelectron momentum spectroscopy. The large separation of the two nuclei of the dimer allows the study of two-equivalent-center interference effects on the photoelectron momentum distribution. Comparing the experimental results with a new model calculation, which is based on the strong-field approximation, actually reveals the influence of interference. Moreover, the comparison indicates that the presence of closely spaced gerade and ungerade electronic state pairs of the Xe2 + ion at the Xe2 ionization threshold, which are strongly dipole coupled, affects the photoelectron momentum distribution.

  8. Few-Photon Multiple Ionization of Ne and Ar by Strong Free-Electron-Laser Pulses

    International Nuclear Information System (INIS)

    Moshammer, R.; Jiang, Y. H.; Rudenko, A.; Ergler, Th.; Schroeter, C. D.; Luedemann, S.; Zrost, K.; Dorn, A.; Ferger, T.; Kuehnel, K. U.; Ullrich, J.; Foucar, L.; Titze, J.; Jahnke, T.; Schoeffler, M.; Doerner, R.; Fischer, D.; Weber, T.; Zouros, T. J. M.; Duesterer, S.

    2007-01-01

    Few-photon multiple ionization of Ne and Ar atoms by strong vacuum ultraviolet laser pulses from the free-electron laser at Hamburg was investigated differentially with the Heidelberg reaction microscope. The light-intensity dependence of Ne 2+ production reveals the dominance of nonsequential two-photon double ionization at intensities of I 12 W/cm 2 and significant contributions of three-photon ionization as I increases. Ne 2+ recoil-ion-momentum distributions suggest that two electrons absorbing ''instantaneously'' two photons are ejected most likely into opposite hemispheres with similar energies

  9. Effect of an improved molecular potential on strong-field tunneling ionization of molecules

    International Nuclear Information System (INIS)

    Zhao Songfeng; Jin Cheng; Le, Anh-Thu; Lin, C. D.

    2010-01-01

    We study the effect of one-electron model potentials on the tunneling ionization rates of molecules in strong fields. By including electron correlation using the modified Leeuwen-Baerends (LB α) model, the binding energies of outer shells of molecules are significantly improved. However, we show that the tunneling ionization rates from the LB α do not differ much from the earlier calculations [Phys. Rev. A 81, 033423 (2010)], in which the local correlation potential was neglected.

  10. Strong-field ionization with twisted laser pulses

    Science.gov (United States)

    Paufler, Willi; Böning, Birger; Fritzsche, Stephan

    2018-04-01

    We apply quantum trajectory Monte Carlo computations in order to model strong-field ionization of atoms by twisted Bessel pulses and calculate photoelectron momentum distributions (PEMD). Since Bessel beams can be considered as an infinite superposition of circularly polarized plane waves with the same helicity, whose wave vectors lie on a cone, we compared the PEMD of such Bessel pulses to those of a circularly polarized pulse. We focus on the momentum distributions in propagation direction of the pulse and show how these momentum distributions are affected by experimental accessible parameters, such as the opening angle of the beam or the impact parameter of the atom with regard to the beam axis. In particular, we show that we can find higher momenta of the photoelectrons, if the opening angle is increased.

  11. Modeling strong-field above-threshold ionization

    International Nuclear Information System (INIS)

    Sundaram, B.; Armstrong, L. Jr.

    1990-01-01

    Above-threshold ionization (ATI) by intense, short-pulse lasers is studied numerically, using the stretched hydrogen atom Hamiltonian. Within our model system, we isolate several mechanisms that contribute to the ATI process. These mechanisms, which involve both excited bound states and continuum states, all invoke intermediate, off-energy shell transitions. In particular, the importance of excited bound states and off-energy shell bound-free processes to the ionization mechanism are shown to relate to a simple physical criterion. These processes point to importance differences in the interpretation of ionization characteristics for short pulses from that for longer pulses. Our analysis concludes that although components of ATI admit of simple, few-state modeling, the ultimate synthesis points to a highly complex mechanism

  12. Interplay between Coulomb-focusing and non-dipole effects in strong-field ionization with elliptical polarization

    Science.gov (United States)

    Daněk, J.; Klaiber, M.; Hatsagortsyan, K. Z.; Keitel, C. H.; Willenberg, B.; Maurer, J.; Mayer, B. W.; Phillips, C. R.; Gallmann, L.; Keller, U.

    2018-06-01

    We study strong-field ionization and rescattering beyond the long-wavelength limit of the dipole approximation with elliptically polarized mid-IR laser pulses. Full three-dimensional photoelectron momentum distributions (PMDs) measured with velocity map imaging and tomographic reconstruction revealed an unexpected sharp ridge structure in the polarization plane (2018 Phys. Rev. A 97 013404). This thin line-shaped ridge structure for low-energy photoelectrons is correlated with the ellipticity-dependent asymmetry of the PMD along the beam propagation direction. The peak of the projection of the PMD onto the beam propagation axis is shifted from negative to positive values when the sharp ridge fades away with increasing ellipticity. With classical trajectory Monte Carlo simulations and analytical analysis, we study the underlying physics of this feature. The underlying physics is based on the interplay between the lateral drift of the ionized electron, the laser magnetic field induced drift in the laser propagation direction, and Coulomb focusing. To apply our observations to emerging techniques relying on strong-field ionization processes, including time-resolved holography and molecular imaging, we present a detailed classical trajectory-based analysis of our observations. The analysis leads to the explanation of the fine structure of the ridge and its non-dipole behavior upon rescattering while introducing restrictions on the ellipticity. These restrictions as well as the ionization and recollision phases provide additional observables to gain information on the timing of the ionization and recollision process and non-dipole properties of the ionization process.

  13. Virtual detector theory for strong-field atomic ionization

    Science.gov (United States)

    Wang, Xu; Tian, Justin; Eberly, J. H.

    2018-04-01

    A virtual detector (VD) is an imaginary device located at a fixed position in space that extracts information from the wave packet passing through it. By recording the particle momentum and the corresponding probability current at each time, the VDs can accumulate and build the differential momentum distribution of the particle, in a way that resembles real experiments. A mathematical proof is given for the equivalence of the differential momentum distribution obtained by the VD method and by Fourier transforming the wave function. In addition to being a tool for reducing the computational load, VDs have also been found useful in interpreting the ultrafast strong-field ionization process, especially the controversial quantum tunneling process.

  14. Strong-field non-sequential ionization: The vector momentum distribution of multiply charged Ne ions

    International Nuclear Information System (INIS)

    Rottke, H.; Trump, C.; Wittmann, M.; Korn, G.; Becker, W.; Hoffmann, K.; Sandner, W.; Moshammer, R.; Feuerstein, B.; Dorn, A.; Schroeter, C.D.; Ullrich, J.; Schmitt, W.

    2000-01-01

    COLTRIMS (COLd Target Recoil-Ion Momentum Spectroscopy) was used to measure the vector momentum distribution of Ne n+ (n=1,2,3) ions formed in ultrashort (30 fsec) high-intensity (≅10 15 W/cm 2 ) laser pulses with center wavelength at 795 nm. To a high degree of accuracy the length of the Ne n+ ion momentum vector is equal to the length of the total momentum vector of the n photoelectrons released, with both vectors pointing into opposite directions. At a light intensity where non-sequential ionization of the atom dominates the Ne 2+ and Ne 3+ momentum distributions show distinct maxima at 4.0 a.u. and 7.5 a.u. along the polarization axis of the linearly polarized light beam. First, this is a clear signature of non-sequential multiple ionization. Second, it indicates that instantaneous emission of two (or more) electrons at electric field strength maxima of the light wave can be ruled out as main mechanism of non-sequential strong-field multiple ionization. In contrast, this experimental result is in accordance with the kinematical constraints of the 'rescattering model'

  15. Ratios of double to single ionization of He and Ne by strong 400-nm laser pulses using the quantitative rescattering theory

    Science.gov (United States)

    Chen, Zhangjin; Li, Xiaojin; Zatsarinny, Oleg; Bartschat, Klaus; Lin, C. D.

    2018-01-01

    We present numerical simulations of the ratio between double and single ionization of He and Ne by intense laser pulses at wavelengths of 390 and 400 nm, respectively. The yields of doubly charged ions due to nonsequential double ionization (NSDI) are obtained by employing the quantitative rescattering (QRS) model. In this model, the NSDI ionization probability is expressed as a product of the returning electron wave packet (RWP) and the total scattering cross sections for laser-free electron impact excitation and electron impact ionization of the parent ion. According to the QRS theory, the same RWP is also responsible for the emission of high-energy above-threshold ionization photoelectrons. To obtain absolute double-ionization yields, the RWP is generated by solving the time-dependent Schrödinger equation (TDSE) within a one-electron model. The same TDSE results can also be taken to obtain single-ionization yields. By using the TDSE results to calibrate single ionization and the RWP obtained from the strong-field approximation, we further simplify the calculation such that the nonuniform laser intensity distribution in the focused laser beam can be accounted for. In addition, laser-free electron impact excitation and ionization cross sections are calculated using the state-of-the-art many-electron R -matrix theory. The simulation results for double-to-single-ionization ratios are found to compare well with experimental data and support the validity of the nonsequential double-ionization mechanism for the covered intensity region.

  16. Atomic-structure effects in strong-field multiphoton detachment and ionization

    International Nuclear Information System (INIS)

    AAberg, T.; Mu, X.; Ruscheinski, J.; Crasemann, B.

    1994-01-01

    Above-threshold photoelectron detachment and ionization spectra are investigated theoretically in the tunneling and over-barrier regime as a function of wavelength (≥ 1.064 μm) and polarization of the electromagnetic field. It is found that the zeros in the initial-state wave function can drastically affect the shape of the high-energy photoelectron distribution. The phenomenon is not predicted by tunneling and related models and hence can test their validity and reveal whether Keldysh-type theories are in general applicable to strong-field multiphoton dynamics. (orig.)

  17. Research on the degradation mechanism of dimethyl phthalate in drinking water by strong ionization discharge

    Science.gov (United States)

    Hong, ZHAO; Chengwu, YI; Rongjie, YI; Huijuan, WANG; Lanlan, YIN; I, N. MUHAMMAD; Zhongfei, MA

    2018-03-01

    The degradation mechanism of dimethyl phthalate (DMP) in the drinking water was investigated using strong ionization discharge technology in this study. Under the optimized condition, the degradation efficiency of DMP in drinking water was up to 93% in 60 min. A series of analytical techniques including high-performance liquid chromatography, liquid chromatography mass spectrometry, total organic carbon analyzer and ultraviolet-visible spectroscopy were used in the study. It was found that a high concentration of ozone (O3) produced by dielectric barrier discharge reactor was up to 74.4 mg l-1 within 60 min. Tert-butanol, isopropyl alcohol, carbonate ions ({{{{CO}}}3}2-) and bicarbonate ions ({{{{HCO}}}3}-) was added to the sample solution to indirectly prove the presence and effect of hydroxyl radicals (·OH). These analytical findings indicate that mono-methyl phthalate, phthalic acid (PA) and methyl ester PA were detected as the major intermediates in the process of DMP degradation. Finally, DMP and all products were mineralized into carbon dioxide (CO2) and water (H2O) ultimately. Based on these analysis results, the degradation pathway of DMP by strong ionization discharge technology were proposed.

  18. Electron-impact ionization of atomic ions: Theoretical results

    Energy Technology Data Exchange (ETDEWEB)

    Loch, S D; Burgos, J M Munoz; Ballance, C P; Ludlow, J; Lee, T-G; Fogle, M; Pindzola, M S [Auburn University, Auburn, AL 36849 (United States); Griffin, D C [Rollins College, Winter Park, FL 32789 (United States); Yumak, A; Yavuz, I; Altun, Z, E-mail: loch@physics.auburn.ed [Marmara University, Istanbul (Turkey)

    2009-11-15

    A brief overview is given of theoretical results for electron-impact ionization of atoms and ions. A description is given of the main theoretical methods, along with the databases where the data are archived. It is shown that for light species, ground and metastable ionization cross sections are in reasonable agreement with experiment when non-perturbative data are used for the near neutrals and distorted wave data are used for ions greater than a few times ionized. Some discrepancies between theory and experiment still remain for systems with open d and open p subshells. The sensitivity of ionization rate coefficients to the near threshold part of the ionization cross section is shown. The role of excited states in effective ionization rate coefficients is demonstrated and recent excited state ionization cross section results for H, He, He{sup +}, B{sup 2+} and Ne are presented.

  19. Ehrenfest's theorem and the validity of the two-step model for strong-field ionization

    DEFF Research Database (Denmark)

    Shvetsov-Shilovskiy, Nikolay; Dimitrovski, Darko; Madsen, Lars Bojer

    By comparison with the solution of the time-dependent Schrodinger equation we explore the validity of the two-step semiclassical model for strong-field ionization in elliptically polarized laser pulses. We find that the discrepancy between the two-step model and the quantum theory correlates...

  20. Weak-field asymptotic theory of tunneling ionization: benchmark analytical results for two-electron atoms

    International Nuclear Information System (INIS)

    Trinh, Vinh H; Morishita, Toru; Tolstikhin, Oleg I

    2015-01-01

    The recently developed many-electron weak-field asymptotic theory of tunneling ionization of atoms and molecules in an external static electric field (Tolstikhin et al 2014, Phys. Rev. A 89, 013421) is extended to the first-order terms in the asymptotic expansion in field. To highlight the results, here we present a simple analytical formula giving the rate of tunneling ionization of two-electron atoms H − and He. Comparison with fully-correlated ab initio calculations available for these systems shows that the first-order theory works quantitatively in a wide range of fields up to the onset of over-the-barrier ionization and hence is expected to find numerous applications in strong-field physics. (fast track communication)

  1. Tunneling time, exit time and exit momentum in strong field tunnel ionization

    International Nuclear Information System (INIS)

    Teeny, Nicolas

    2016-01-01

    Tunnel ionization belongs to the fundamental processes of atomic physics. It is still an open question when does the electron tunnel ionize and how long is the duration of tunneling. In this work we solve the time-dependent Schroedinger equation in one and two dimensions and use ab initio quantum calculations in order to answer these questions. Additionally, we determine the exit momentum of the tunnel ionized electron from first principles. We find out results that are different from the assumptions of the commonly employed two-step model, which assumes that the electron ionizes at the instant of electric field maximum with a zero momentum. After determining the quantum final momentum distribution of tunnel ionized electrons we show that the two-step model fails to predict the correct final momentum. Accordingly we suggest how to correct the two-step model. Furthermore, we determine the instant at which tunnel ionization starts, which turns out to be different from the instant usually assumed. From determining the instant at which it is most probable for the electron to enter the tunneling barrier and the instant at which it exits we determine the most probable time spent under the barrier. Moreover, we apply a quantum clock approach in order to determine the duration of tunnel ionization. From the quantum clock we determine an average tunneling time which is different in magnitude and origin with respect to the most probable tunneling time. By defining a probability distribution of tunneling times using virtual detectors we relate both methods and explain the apparent discrepancy. The results found have in general an effect on the interpretation of experiments that measure the spectra of tunnel ionized electrons, and specifically on the calibration of the so called attoclock experiments, because models with imprecise assumptions are usually employed in order to interpret experimental results.

  2. Tunneling time, exit time and exit momentum in strong field tunnel ionization

    Energy Technology Data Exchange (ETDEWEB)

    Teeny, Nicolas

    2016-10-18

    Tunnel ionization belongs to the fundamental processes of atomic physics. It is still an open question when does the electron tunnel ionize and how long is the duration of tunneling. In this work we solve the time-dependent Schroedinger equation in one and two dimensions and use ab initio quantum calculations in order to answer these questions. Additionally, we determine the exit momentum of the tunnel ionized electron from first principles. We find out results that are different from the assumptions of the commonly employed two-step model, which assumes that the electron ionizes at the instant of electric field maximum with a zero momentum. After determining the quantum final momentum distribution of tunnel ionized electrons we show that the two-step model fails to predict the correct final momentum. Accordingly we suggest how to correct the two-step model. Furthermore, we determine the instant at which tunnel ionization starts, which turns out to be different from the instant usually assumed. From determining the instant at which it is most probable for the electron to enter the tunneling barrier and the instant at which it exits we determine the most probable time spent under the barrier. Moreover, we apply a quantum clock approach in order to determine the duration of tunnel ionization. From the quantum clock we determine an average tunneling time which is different in magnitude and origin with respect to the most probable tunneling time. By defining a probability distribution of tunneling times using virtual detectors we relate both methods and explain the apparent discrepancy. The results found have in general an effect on the interpretation of experiments that measure the spectra of tunnel ionized electrons, and specifically on the calibration of the so called attoclock experiments, because models with imprecise assumptions are usually employed in order to interpret experimental results.

  3. Coupled-cluster treatment of molecular strong-field ionization

    Science.gov (United States)

    Jagau, Thomas-C.

    2018-05-01

    Ionization rates and Stark shifts of H2, CO, O2, H2O, and CH4 in static electric fields have been computed with coupled-cluster methods in a basis set of atom-centered Gaussian functions with a complex-scaled exponent. Consideration of electron correlation is found to be of great importance even for a qualitatively correct description of the dependence of ionization rates and Stark shifts on the strength and orientation of the external field. The analysis of the second moments of the molecular charge distribution suggests a simple criterion for distinguishing tunnel and barrier suppression ionization in polyatomic molecules.

  4. Channel-closing effects in strong-field ionization by a bicircular field

    Science.gov (United States)

    Milošević, D. B.; Becker, W.

    2018-03-01

    Channel-closing effects, such as threshold anomalies and resonantlike intensity-dependent enhancements in strong-field ionization by a bicircular laser field are analyzed. A bicircular field consists of two coplanar corotating or counter-rotating circularly polarized fields having different frequencies. For the total detachment rate of a negative ion by a bicircular field we observe threshold anomalies and explain them using the Wigner threshold law and energy and angular momentum conservation. For the corotating bicircular case, these effects are negligible, while for the counter-rotating case they are pronounced and their position depends on the magnetic quantum number of the initial state. For high-order above-threshold ionization of rare-gas atoms by a counter-rotating bicircular laser field we observe very pronounced intensity-dependent enhancements. We find all four types of threshold anomalies known from collision theory. Contrary to the case of linear polarization, channel-closing effects for a bicircular field are visible also in the cutoff region of the electron energy spectrum, which is explained using quantum-orbit theory.

  5. Multiorbital effects in strong-field ionization and dissociation of aligned polar molecules CH3I and CH3Br

    Science.gov (United States)

    Luo, Sizuo; Zhou, Shushan; Hu, Wenhui; Li, Xiaokai; Ma, Pan; Yu, Jiaqi; Zhu, Ruihan; Wang, Chuncheng; Liu, Fuchun; Yan, Bing; Liu, Aihua; Yang, Yujun; Guo, Fuming; Ding, Dajun

    2017-12-01

    Controlling the molecular axis offers additional ways to study molecular ionization and dissociation in strong laser fields. We measure the ionization and dissociation yields of aligned polar CH3X (X =I , Br) molecules in a linearly polarized femtosecond laser field. The current data show that maximum ionization occurs when the laser polarization is perpendicular to the molecular C -X axis, and dissociation prefers to occur at the laser polarization parallel to the C -X axis. The observed angular distributions suggest that the parent ions are generated by ionization from the HOMO. The angular distribution of fragment ions indicates that dissociation occurs mainly from an ionic excited state produced by ionization from the HOMO-1.

  6. Ionization dynamics of a xenon atom in super-strong laser fields

    International Nuclear Information System (INIS)

    Yamakawa, Koichi; Akahane, Yutaka; Fukuda, Yuji; Aoyama, Makoto; Inoue, Norihiro; Ueda, Hideki; Utsumi, Takayuki

    2003-12-01

    We report on detailed investigations of ionization dynamics of a xenon atom exposed to intense 800-nm pulses of 20-fs duration in the extensive intensity range from 10 13 to 10 18 W/cm 2 . Ion yields of Xe + to Xe 20+ were observed as a function of laser intensity and compared with the results from a single active electron (SAE) based Ammosov-Delone-Krainov (ADK) model. Unexpected ionization probabilities for lower charge states and also no interplay between the inner- and outer-shells by screening are inferred. Suppression of nonsequential ionization towards higher intensity and few optical cycle regimes is also proved. (author)

  7. Ionization equilibrium in dense plasmas

    International Nuclear Information System (INIS)

    Ying, R.

    1987-01-01

    The average degree of ionization for a strongly coupled plasma is investigated and calculated. Two widely used approaches: the Saha equation method and the Thomas-Fermi (TF) statistical atomic model are adopted to determine the degree of ionization. Both methods are modified in a number of ways to include the strong-coupling effect in the plasma. In the Saha equation approach, the strong-coupling effects are introduced through: (i) a replacement of the Coulomb potential by a screened Debye potential; (ii) adoption of the Planck-Larkin partition function; (iii) description of the electron component by Fermi-Dirac statistics. The calculated degree of ionization exceeds that obtained from the original Saha equation, exhibits a minimum as a function of the density and shows an abrupt phase transition from weakly ionized to a fully ionized state. The zero-temperature TF model for compressed ions and the finite-temperature TF model for ions are investigated for the first time. In order to take into account the strong-coupling effect in a systematic way, a strong-coupling TF model is set up. Favorable results with the relatively simple approximations indicate that the newly established strong-coupling TF model is a more systematic and physically consistent approach

  8. Enhancement of strong-field multiple ionization in the vicinity of the conical intersection in 1,3-cyclohexadiene ring opening

    International Nuclear Information System (INIS)

    Petrovic, Vladimir S.; Kim, Jaehee; Schorb, Sebastian; White, James; Cryan, James P.; Zipp, Lucas; Glownia, J. Michael; Broege, Douglas; Miyabe, Shungo; Tao, Hongli; Martinez, Todd; Bucksbaum, Philip H.

    2013-01-01

    Nonradiative energy dissipation in electronically excited polyatomic molecules proceeds through conical intersections, loci of degeneracy between electronic states. We observe a marked enhancement of laser-induced double ionization in the vicinity of a conical intersection during a non-radiative transition. We measured double ionization by detecting the kinetic energy of ions released by laser-induced strong-field fragmentation during the ring-opening transition between 1,3-cyclohexadiene and 1,3,5-hexatriene. The enhancement of the double ionization correlates with the conical intersection between the HOMO and LUMO orbitals

  9. Methods for Creation and Detection of Ultra-Strong Artificial Ionization in the Upper Atmosphere (Invited)

    Science.gov (United States)

    Bernhardt, P. A.; Siefring, C. L.; Briczinski, S. J.; Kendall, E. A.; Watkins, B. J.; Bristow, W. A.; Michell, R.

    2013-12-01

    The High Frequency Active Auroral Research Program (HAARP) transmitter in Alaska has been used to produce localized regions of artificial ionization at altitudes between 150 and 250 km. High power radio waves tuned near harmonics of the electron gyro frequency were discovered by Todd Pederson of the Air Force Research Laboratory to produce ionosonde traces that looked like artificial ionization layers below the natural F-region. The initial regions of artificial ionization (AI) were not stable but had moved down in altitude over a period of 15 minutes. Recently, artificial ionization has been produced by the 2nd, 3rd, 4th and 6th harmonics transmissions by the HAARP. In march 2013, the artificial ionization clouds were sustained for more the 5 hours using HAARP tuned to the 4 fce at the full power of 3.6 Mega-Watts with a twisted-beam antenna pattern. Frequency selection with narrow-band sweeps and antenna pattern shaping has been employed for optimal generation of AI. Recent research at HAARP has produced the longest lived and denser artificial ionization clouds using HF transmissions at the harmonics of the electron cyclotron frequency and ring-shaped radio beams tailored to prevent the descent of the clouds. Detection of artificial ionization employs (1) ionosonde echoes, (2) coherent backscatter from the Kodiak SuperDARN radar, (3) enhanced ion and plasma line echoes from the HAARP MUIR radar at 400 MHz, (4) high resolution optical image from ground sites, and (5) unique stimulated electromagnetic emissions, and (6) strong UHF and L-Band scintillation induced into trans-ionospheric signals from satellite radio beacons. Future HAARP experiments will determine the uses of long-sustained AI for enhanced HF communications.

  10. Study on the plasma reaction process of hydroxyl generation by strong electric field ionization discharge

    International Nuclear Information System (INIS)

    Bai Mindi; Deng Shufang; Bai Xiyao; Zhang Zhitao

    2004-01-01

    Considering the change in the structure of reaction room, dielectric materials and process technology, authors have specifically studied the plasma reaction process of creating hydroxyl radical OH * and e aq - from ionization of O 2 and H 2 O through a strong electric field discharge. The production volume of hydroxyl radical OH * is up to the project application level, and process technology meets the 12 laws of green chemistry, free from environmental pollution from the source. The authors have emphatically researched on the green method of flue gas desulfurization, which will ionize SO 2 , H 2 O and O 2 in the flue gas to synthesis H 2 SO 4 in molecular level within 0.8 s without absorbent and catalyst. (author)

  11. Photoelectron angular distributions from strong-field ionization of oriented molecules

    DEFF Research Database (Denmark)

    Holmegaard, Lotte; Hansen, Jonas Lerche; Kalhøj, Line

    2010-01-01

    The combination of ultrafast light sources with detection of molecular-frame photoelectron angular distributions (MFPADs) is setting new standards for detailed interrogation of molecular dynamics. However, until recently measurement of MFPADs relied on determining the molecular orientation after...... ionization, which is limited to species and processes where ionization leads to fragmentation. An alternative is to fix the molecular frame before ionization. The only demonstrations of such spatial orientation involved aligned small linear nonpolar molecules. Here we extend these techniques to the general...... class of polar molecules. Carbonylsulphide and benzonitrile molecules, fixed in space by combined laser and electrostatic fields, are ionized with intense, circularly polarized 30-fs laser pulses. For carbonylsulphide and benzonitrile oriented in one dimension, the MFPADs exhibit pronounced anisotropies...

  12. Research on killing Escherichia Coli by reactive oxygen species based on strong ionization discharging plasma

    International Nuclear Information System (INIS)

    Li, Y J; Tian, Y P; Zhang, Z T; Li, R H; Cai, L J; Gao, J Y

    2013-01-01

    Reactive oxygen species solution produced by strong ionization discharging plasma was used to kill Escherichia coli by spraying. Several effect factors such as pH value, solution temperature, spraying time and exposure time were observed in this study, and their effects on killing rate of Escherichia coli were discussed and analysed. Results show that the treating efficiency of ROS solution for Escherichia coli is higher in alkaline solution than that in acid solution. The killing rate of Escherichia coli increases while the spraying time and exposure time are longer and the temperature is lower. The effects of different factors on killing rate of Escherichia coli are as follows: spraying time > pH value > exposure time > solution temperature.

  13. Five-photon ionization of atomic hydrogen at wavelengths around the threshold for four-photon ionization

    International Nuclear Information System (INIS)

    Gontier, Y.; Trahin, M.; Wolff-Rottke, B.; Rottke, H.; Welge, K.H.; Feldmann, D.

    1992-01-01

    Theoretical and experimental studies show the strong influence of the three-photon nearly resonant 2p state on four- and five-photon ionization of atomic hydrogen near the threshold for four-photon ionization. Changes in five-photon ionization occur when the four-photon ionization channel opens. The angular distributions of photoelectrons from five-photon ionization of H are studied at five wavelengths which cover the range from four-photon resonance with high-lying Rydberg states (n≥10) to direct four-photon ionization into the continuum. The role of resonances in this ionization process is discussed. A fair agreement is found in comparing experimental and theoretical results

  14. Multi-photon resonant effects in strong-field ionization: origin of the dip in experimental longitudinal momentum distributions

    International Nuclear Information System (INIS)

    Alnaser, A S; Maharjan, C M; Wang, P; Litvinyuk, I V

    2006-01-01

    We studied ionization of neon and argon by intense linearly polarized femtosecond laser pulses of different wavelengths (400 nm and 800 nm) and peak intensities, and by measuring momentum distributions of singly charged positive ions in the direction parallel to laser polarization. For Ne the momentum distributions exhibited a characteristic dip at zero momentum at 800 nm and a complex multipeak structure at 400 nm. Similarly, for Ar the momentum distributions evolved from a complex multipeak structure with a pronounced dip in the centre at 400 nm, to a smooth distribution characteristic of pure tunneling ionization (800 nm, high intensities). In the intermediate regime (800 nm, medium to low intensities), for both atoms we observed recoil ion momentum distributions modulated by quasi-periodic structures usually seen in the photoelectron energy spectra in a multi-photon regime (ATI spectra). Ne did show a characteristic 'dip' at low momentum, while the longitudinal momentum distribution for Ar exhibited a spike at zero momentum instead. The spectra did dramatically change at 400 nm, where both ions show the pronounced dip near zero momentum. Based on our results, we conclude that the structures observed in Ne and Ar momentum distributions reflect the specifics of atomic structure of the two targets and should not be attributed to effects of electron recollision, as was suggested earlier. Instead, as our results indicate, they are due to the effects of multi-photon resonant enhancement of strong-field ionization. (letter to the editor)

  15. Holding molecular dications together in strong laser fields

    International Nuclear Information System (INIS)

    Guo Chunlei

    2006-01-01

    Metastable channel of doubly ionized carbon monoxide, CO 2+ , was scantly seen in previous strong-field experiments at the visible wavelength region, but was commonly observed using single high-energy photon or electron excitation. For the first time with near-IR ultrashort-pulse radiation, we observe an abundance of CO 2+ . We show that CO 2+ results from nonsequential double ionization, while its dissociation counterpart, C + +O + , results from sequential processes, and CO 2+ can be obtained through either single high-energy photon or electron excitation or multiphoton ionization with ultrashort pulses before a critical internuclear distance is reached. Our study demonstrates the experimental conditions to converge the outcomes from two vastly different regimes, namely, multiphoton excitation and ionization in strong fields and single high-energy photon or electron excitation and ionization in weak fields

  16. Imprints of the Molecular Electronic Structure in the Photoelectron Spectra of Strong-Field Ionized Asymmetric Triatomic Model Molecules

    Science.gov (United States)

    Paul, Matthias; Yue, Lun; Gräfe, Stefanie

    2018-06-01

    We examine the circular dichroism in the angular distribution of photoelectrons of triatomic model systems ionized by strong-field ionization. Following our recent work on this effect [Paul, Yue, and Gräfe, J. Mod. Opt. 64, 1104 (2017), 10.1080/09500340.2017.1299883], we demonstrate how the symmetry and electronic structure of the system is imprinted into the photoelectron momentum distribution. We use classical trajectories to reveal the origin of the threefolded pattern in the photoelectron momentum distribution, and show how an asymmetric nuclear configuration of the triatomic system effects the photoelectron spectra.

  17. Limitations of the strong field approximation in ionization of the hydrogen atom by ultrashort pulses

    International Nuclear Information System (INIS)

    Arbo, D.G.; Toekesi, K.; Miraglia, J.E.; FCEN, University of Buenos Aires

    2008-01-01

    Complete text of publication follows. We presented a theoretical study of the ionization of hydrogen atoms as a result of the interaction with an ultrashort external electric field. Doubly-differential momentum distributions and angular momentum distributions of ejected electrons calculated in the framework of the Coulomb-Volkov and strong field approximations, as well as classical calculations are compared with the exact solution of the time dependent Schroedinger equation. We have shown that the Coulomb-Volkov approximation (CVA) describes the quantum atomic ionization probabilities exactly when the external field is described by a sudden momentum transfer [1]. The velocity distribution of emitted electrons right after ionization by a sudden momentum transfer is given through the strong field approximation (SFA) within both the CVA and CTMC methods. In this case, the classical and quantum time dependent evolutions of an atom subject to a sudden momentum transfer are identical. The difference between the classical and quantum final momentum distributions resides in the time evolution of the escaping electron under the subsequent action of the Coulomb field. Furthermore, classical mechanics is incapable of reproducing the quantum angular momentum distribution due to the improper initial radial distribution used in the CTMC calculations, i.e., the microcanonical ensemble. We find that in the limit of high momentum transfer, based on the SFA, there is a direct relation between the cylindrical radial distribution dP/dρ and the final angular momentum distribution dP/dL. This leads to a close analytical expression for the partial wave populations (dP/dL) SFA-Q given by dP SFA-Q / dL = 4Z 3 L 2 / (Δp) 3 K 1 (2ZL/Δp) which, together with the prescription L = l + 1/2, reproduces quite accurately the quantum (CVA) results. Considering the inverse problem, knowing the final angular momentum distribution can lead to the inference of the initial probability distribution

  18. Polarization effects in above-threshold ionization with a mid-infrared strong laser field

    Science.gov (United States)

    Kang, Hui-Peng; Xu, Song-Po; Wang, Yan-Lan; Yu, Shao-Gang; Zhao, Xiao-Yun; Hao, Xiao-Lei; Lai, Xuan-Yang; Pfeifer, Thomas; Liu, Xiao-Jun; Chen, Jing; Cheng, Ya; Xu, Zhi-Zhan

    2018-05-01

    Using a semiclassical approach, we theoretically study the above-threshold ionization of magnesium by intense, mid-infrared laser pulses. The formation of low-energy structures in the photoelectron spectrum is found to be enhanced by comparing with a calculation based on the single-active electron approximation. By performing electron trajectory and recollision-time distribution analysis, we demonstrate that this phenomenon is due to the laser-induced ionic core polarization effects on the recolliding electrons. We also show that the polarization effects should be experimentally detectable. Our finding provides new insight into ultrafast control of strong-field photoionization and imaging of polar molecules.

  19. Interpreting tunneling time in circularly polarized strong-laser ionization

    OpenAIRE

    Yuan, MingHu; Xin, PeiPei; Chu, TianShu; Liu, HongPing

    2016-01-01

    We propose a method to study the tunneling process by analyzing the time-dependent ionization yield in circularly polarized laser. A numerical calculation shows that for an atom exposed to a long laser pulse, if its initial electronic state wave function is non-spherical symmetric, the delayed phase shift of the ionization rate vs. the laser cycle period in real time in the region close to the peak intensity of the laser pulse can be used to probe the tunneling time. In this region, an obviou...

  20. Convergence of high-intensity expansions for atomic ionization

    International Nuclear Information System (INIS)

    Antunes Neto, H.S.; Davidovich, L.

    1984-01-01

    It is shown that a frequently used nonperturbative approximation for atomic ionization rates is cancelled out when corrections are taken into account. This explains the strong gauge dependence of previous results. A convergent and gauge invariant expansion is obtained. Numerical results show that its first term, which may be calculated analytically in many cases, describes very well the time-dependent behaviour of the ionization probability, for very strong fields. (Author) [pt

  1. Ionization of a two-electron atom in a strong electromagnetic field

    International Nuclear Information System (INIS)

    Ovodova, O.V.; Popov, A.M.; Tikhonova, O.V.

    1997-01-01

    A one-dimensional model of a helium atom in an intense field of a femtosecond electromagnetic pulse has been constructed using the Hartree technique. 'Exact' calculations have been compared to the approximations of 'frozen' and 'passive' electrons. A nonmonotonic dependence of the single-electron ionization probability on the radiation intensity has been detected. Minima in the ionization probability are due to multiphoton resonances between different atomic states due to the dynamic Stark effect. We suggest that the ionization suppression is due to the interference stabilization in this case

  2. Laser-assisted electron scattering in strong-field ionization of dense water vapor by ultrashort laser pulses

    International Nuclear Information System (INIS)

    Wilke, M; Al-Obaidi, R; Moguilevski, A; Kothe, A; Engel, N; Metje, J; Kiyan, I Yu; Aziz, E F

    2014-01-01

    We report on strong-field ionization of dense water gas in a short infrared laser pulse. By employing a unique combination of photoelectron spectroscopy with a liquid micro-jet technique, we observe how the character of electron emission at high kinetic energies changes with the increase of the medium density. This change is associated with the process of laser-assisted electron scattering (LAES) on neighboring particles, which becomes a dominant mechanism of hot electron emission at higher medium densities. The manifestation of this mechanism is found to require densities that are orders of magnitude lower than those considered for heating the laser-generated plasmas via the LAES process. The experimental results are supported by simulations of the LAES yield with the use of the Kroll–Watson theory. (paper)

  3. Double atom ionization by multicharged ions and strong electromagnetic field: correlation effects in a continuous spectrum

    International Nuclear Information System (INIS)

    Presnyakov, L.P.; Uskov, D.B.

    1997-01-01

    The nonstationary theory of double ionization of two-electron atoms in collisions with multicharged ions or under the impact of intensive electromagnetic field is developed. The approach, making it possible to study both problems by uniform method, is formulated. The two-electron wave function of continuous spectrum, accounting for interaction of electrons with atomic nucleus, external ionizer and between themselves is obtained. The calculation results on the helium atoms double ionization by multicharged ions is a good quantitative agreement with available experimental data

  4. Possible effect of strong solar energetic particle events on polar stratospheric aerosol: a summary of observational results

    International Nuclear Information System (INIS)

    Mironova, I A; Usoskin, I G

    2014-01-01

    This letter presents a summary of a phenomenological study of the response of the polar stratosphere to strong solar energetic particle (SEP) events corresponding to ground level enhancements (GLEs) of cosmic rays. This work is focused on evaluation of the possible influence of the atmospheric ionization caused by SEPs upon formation of aerosol particles in the stratosphere over polar regions. Following case studies of two major SEP/GLE events, in January 2005 and September 1989, and their possible effects on polar stratospheric aerosols, we present here the results of an analysis of variations of the daily profiles of the stratospheric aerosol parameters (aerosol extinction for different wavelengths, as well as Ångstrom exponent) for both polar hemispheres during SEP/GLE events of July 2000, April 2001 and October 2003, which form already five clear cases corresponding to extreme and strong SEP/GLE events. The obtained results suggest that an enhancement of ionization rate by a factor of about two in the polar region with night/cold/winter conditions can lead to the formation/growing of aerosol particles in the altitude range of 10–25 km. We also present a summary of the investigated effects based on the phenomenological study of the atmospheric application of extreme SEP events. (paper)

  5. Collisional ionization of Na by HBr in weak to strong electric fields

    International Nuclear Information System (INIS)

    Safinya, K.A.; Gallagher, T.F.; Sandner, W.; Gounand, F.

    1985-01-01

    We report the effect of static electric fields on the collisional ionization of highly excited sodium atoms by HBr. The binding energy dependence of the collisional ionization cross section is measured at zero field and in static electric fields up to that point at which the atom field ionizes. The applied electric field lowers the ionization threshold of the atom from its zero field value. Therefore an atom near the ionization threshold in an electric field is of smaller size than a free field atom with the same binding energy. Thus measuring the binding energy dependence of the cross section at different values of the electric field allows us to study the effects of the physical size of the atom on the cross section. The effect of the electric field was to lower the measured ionization cross section. However, the binding energy dependence of the cross section remains unchanged at the level of our measurement accuracy. The measured cross sections are larger for larger atoms, exhibit a drop with increasing binding energy characteristic of rotational to electronic excitation transfer, and are of order 10 -12 --10 -11 cm 2 . A simple calculation based on dipole (J→ J-1) excitation transfer from the molecule to the atom predicts, with good agreement, the binding energy dependence of the cross section. The electric field dependence of the data however, is not shown in the theory

  6. Ionization Processes in the Atmosphere of Titan (Research Note). III. Ionization by High-Z Nuclei Cosmic Rays

    Science.gov (United States)

    Gronoff, G.; Mertens, C.; Lilensten, J.; Desorgher, L.; Fluckiger, E.; Velinov, P.

    2011-01-01

    Context. The Cassini-Huygens mission has revealed the importance of particle precipitation in the atmosphere of Titan thanks to in-situ measurements. These ionizing particles (electrons, protons, and cosmic rays) have a strong impact on the chemistry, hence must be modeled. Aims. We revisit our computation of ionization in the atmosphere of Titan by cosmic rays. The high-energy high-mass ions are taken into account to improve the precision of the calculation of the ion production profile. Methods. The Badhwahr and O Neill model for cosmic ray spectrum was adapted for the Titan model. We used the TransTitan model coupled with the Planetocosmics model to compute the ion production by cosmic rays. We compared the results with the NAIRAS/HZETRN ionization model used for the first time for a body that differs from the Earth. Results. The cosmic ray ionization is computed for five groups of cosmic rays, depending on their charge and mass: protons, alpha, Z = 8 (oxygen), Z = 14 (silicon), and Z = 26 (iron) nucleus. Protons and alpha particles ionize mainly at 65 km altitude, while the higher mass nucleons ionize at higher altitudes. Nevertheless, the ionization at higher altitude is insufficient to obscure the impact of Saturn s magnetosphere protons at a 500 km altitude. The ionization rate at the peak (altitude: 65 km, for all the different conditions) lies between 30 and 40/cu cm/s. Conclusions. These new computations show for the first time the importance of high Z cosmic rays on the ionization of the Titan atmosphere. The updated full ionization profile shape does not differ significantly from that found in our previous calculations (Paper I: Gronoff et al. 2009, 506, 955) but undergoes a strong increase in intensity below an altitude of 400 km, especially between 200 and 400 km altitude where alpha and heavier particles (in the cosmic ray spectrum) are responsible for 40% of the ionization. The comparison of several models of ionization and cosmic ray spectra (in

  7. Ionization of oriented carbonyl sulfide molecules by intense circularly polarized laser pulses

    DEFF Research Database (Denmark)

    Dimitrovski, Darko; Abu-Samha, Mahmoud; Madsen, Lars Bojer

    2011-01-01

    We present combined experimental and theoretical results on strong-field ionization of oriented carbonyl sulfide molecules by circularly polarized laser pulses. The obtained molecular frame photoelectron angular distributions show pronounced asymmetries perpendicular to the direction of the molec......We present combined experimental and theoretical results on strong-field ionization of oriented carbonyl sulfide molecules by circularly polarized laser pulses. The obtained molecular frame photoelectron angular distributions show pronounced asymmetries perpendicular to the direction......-dimensionally-oriented polar molecules, in particular asymmetries in the emission direction of the photoelectrons. In the following article [Phys. Rev. A 83, 023406 (2011)] the focus is to understand strong-field ionization from three-dimensionally-oriented asymmetric top molecules, in particular the suppression of electron...

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

    KAUST Repository

    Efimov, D K

    2016-05-18

    We consider Penning ionization of Rydberg atom pairs as an Auger-type process induced by the dipole-dipole interaction and employ semiclassical formulae for dipole transitions to calculate the autoionization width as a function of the principal quantum numbers, n d, n i, of both atoms. While for symmetric atom pairs with the well-known increase of the autoionization width with increasing n 0 is obtained, the result for asymmetric pairs is counterintuitive - for a fixed n i of the ionizing atom of the pair, the autoionization width strongly increases with decreasing n d of the de-excited atom. For H Rydberg atoms this increase reaches two orders of magnitude at the maximum of the n d dependence, and the same type of counterintuitive behavior is exhibited also by Na, Rb and Cs atoms. This is a purely quantum-mechanical effect, which points towards existence of optimal (we call them \\'Tom\\' and \\'Jerry\\' for \\'big\\' and \\'small\\') pairs of Rydberg atoms with respect to autoionization efficiency. Building on the model of population redistribution in cold Rydberg gases proposed in [1], we demonstrate that population evolution following the initial laser excitation of Rydberg atoms in state n 0 would eventually lead to the formation of such Tom-Jerry pairs with which feature autoionization widths that are enhanced by several orders of magnitude compared to that of two atoms in the initial laser-excited state n 0. We also show that in the high-density regime of cold Rydberg gas experiments the ionization rate of Tom-Jerry pairs can be substantially larger than the blackbody radiation-induced photoionization rate. © 2016 IOP Publishing Ltd.

  9. Study of the ionization of H+2 ions in strong laser fields

    International Nuclear Information System (INIS)

    Odenweller, Matthias

    2010-01-01

    In the framework of this thesis it has been succeeded to develop a worldwide unique measurement apparatur, by which hydrogen-molecule ions can be ionized by means of short laser pulses and the reaction product kinematically completely measured. For this a detection method following the Coltrims technique, in which both protons and electrons can be detected over the complete spatial angle. The H + 2 ions origin from a high-frequency ion source and are accelerated to 400 keV. This ion beam is overlapped with a 780-nm laser pulse othe pulse length 40 fs. After the reaction the molecule ions fragments either via the dissociation channel H + 2 +nhν→H+H + or via an ionization followed by a Coulomb explosion: H + 2 +nhν→H + +H + +e - . The projectiles are detected after a drift path of about 3 m on an ion detector. For the detection of the electrons a special spectrometer was concipated. In the reaction it comes by the comparatively long pulse length already at low intensities to dissociation processes. The dissociating molecule reaches still during the increasing side of the laser pulse in this way distances, in which the charge-resonance-enhanced-ionization (CREI) can take place. Also the angular distribution of the measured protons lying in a very small angular range around the polarization direction of the laser suggests that CREI is the dominant ionization process. At circular polarization however a netto-acceleration of the electrons perpendicularly to the direction of the electric field at the ionization time takes place, so that the measurement of the electron momenta represents a suited measurement quantity for the study of the ionization process. By this way angular distributions of the electrons relatively to the internuclear axis within the polarization plane could be measured.

  10. Attosecond Electron Wave Packet Dynamics in Strong Laser Fields

    International Nuclear Information System (INIS)

    Johnsson, P.; Remetter, T.; Varju, K.; L'Huillier, A.; Lopez-Martens, R.; Valentin, C.; Balcou, Ph.; Kazamias, S.; Mauritsson, J.; Gaarde, M. B.; Schafer, K. J.; Mairesse, Y.; Wabnitz, H.; Salieres, P.

    2005-01-01

    We use a train of sub-200 attosecond extreme ultraviolet (XUV) pulses with energies just above the ionization threshold in argon to create a train of temporally localized electron wave packets. We study the energy transfer from a strong infrared (IR) laser field to the ionized electrons as a function of the delay between the XUV and IR fields. When the wave packets are born at the zero crossings of the IR field, a significant amount of energy (∼20 eV) is transferred from the field to the electrons. This results in dramatically enhanced above-threshold ionization in conditions where the IR field alone does not induce any significant ionization. Because both the energy and duration of the wave packets can be varied independently of the IR laser, they are valuable tools for studying and controlling strong-field processes

  11. High-intensity ionization approximations: test of convergence in a one-dimensional model

    International Nuclear Information System (INIS)

    Antunes Neto, H.S.; Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro); Davidovich, L.; Marchesin, D.

    1983-06-01

    By solving numerically a one-dimensional model, the range of validity of some non-perturbative treatments proposed for the problem of atomic ionization by strong laser fields is examined. Some scalling properties of the ionization probability are stablished and a new approximation, which converges to the exact results in the limit of very strong fields is proposed. (Author) [pt

  12. Relativistic theory of tunnel and multiphoton ionization of atoms in a strong laser field

    International Nuclear Information System (INIS)

    Popov, V. S.; Karnakov, B. M.; Mur, V. D.; Pozdnyakov, S. G.

    2006-01-01

    Relativistic generalization is developed for the semiclassical theory of tunnel and multiphoton ionization of atoms and ions in the field of an intense electromagnetic wave (Keldysh theory). The cases of linear, circular, and elliptic polarizations of radiation are considered. For arbitrary values of the adiabaticity parameter γ, the exponential factor in the ionization rate for a relativistic bound state is calculated. For low-frequency laser radiation , an asymptotically exact formula for the tunnel ionization rate for the atomic s level is obtained including the Coulomb, spin, and adiabatic corrections and the preexponential factor. The ionization rate for the ground level of a hydrogen-like atom (ion) with Z ≤ 100 is calculated as a function of the laser radiation intensity. The range of applicability is determined for nonrelativistic ionization theory. The imaginary time method is used in the calculations

  13. Bound-Electron Nonlinearity Beyond the Ionization Threshold

    Science.gov (United States)

    Wahlstrand, J. K.; Zahedpour, S.; Bahl, A.; Kolesik, M.; Milchberg, H. M.

    2018-05-01

    We present absolute space- and time-resolved measurements of the ultrafast laser-driven nonlinear polarizability in argon, krypton, xenon, nitrogen, and oxygen up to ionization fractions of a few percent. These measurements enable determination of the strongly nonperturbative bound-electron nonlinear polarizability well beyond the ionization threshold, where it is found to remain approximately quadratic in the laser field, a result normally expected at much lower intensities where perturbation theory applies.

  14. Simulation study of the ionizing front in the critical ionization velocity phenomenon

    International Nuclear Information System (INIS)

    Machida, S.; Goertz, C.K.; Lu, G.

    1988-01-01

    Simulations of the Critical Ionization Velocity (CIV) for a neutral gas cloud moving across the static magnetic field are made. We treat a low-β plasma and use a 2-1/2 D electrostatic code linked with our Plasma and Neutral Interaction Code (PANIC). Our study is focused on the understanding of the interface between the neutral gas cloud and the surrounding plasma where the strong interaction takes place. We assume the existence of some hot electrons in the ambient plasma to provide a seed ionization for CIV. When the ionization starts a sheath-like structure is formed at the surface of the neutral gas (Ionizing Front). In that region the crossfield component of the electric field causes the electron to E x B drift with a velocity of the order of the neutral gas velocity times the square root of the ion to electron mass ratio. Thus the kinetic energy of the drifting electrons can be large enough for electron impact ionization. In addition a diamagnetic drift of the electron occurs due to the number density and temperature inhomogeneity in the ionization front. These drift currents excite the lower-hybrid waves with the wave k-vectors almost perpendicular to the neutral flow and magnetic field again resulting in electron heating and additional ionization. The overall structure is studied by developing a simple analytic model as well as making simulation runs. (author)

  15. Signature of charge migration in modulations of double ionization

    Science.gov (United States)

    Mauger, François; Abanador, Paul M.; Bruner, Adam; Sissay, Adonay; Gaarde, Mette B.; Lopata, Kenneth; Schafer, Kenneth J.

    2018-04-01

    We present a theoretical investigation of charge migration following strong-field ionization in a multielectron system. We study a model homonuclear molecule with two electrons, each restricted to one dimension (1 +1 D ), interacting with a strong, static electric field. We show that in this system charge migration results from the interplay between multiple ionization channels that overlap in space, creating a coherent electron-hole wave packet in the cation. We also find that, in our case, charge migration following the first ionization manifests as a modulation of the subsequent double-ionization signal. We derive a parametrized semiclassical model from the full multielectron system and we discuss the importance of the choice of cation electronic-structure basis for the efficacy of the semiclassical representation. We use the ab initio solution of the full 1 +1 D system as a reference for the qualitative and quantitative results of the parametrized semiclassical model. We discuss the extension of our model to long-wavelength time-dependent fields with full-dimension, many-electron targets.

  16. Cross section data for ionization of important cyanides

    International Nuclear Information System (INIS)

    Kaur, Jaspreet; Antony, Bobby

    2015-01-01

    Highlights: • Multi centre spherical complex optical potential formalism used to find the CS. • Effective method (CSP-ic) to derive ionization contribution from inelastic CS. • Result shows excellent accord with previous results and consistent behaviour. • Maiden attempt to find CS for many cyanide molecules. • Strong correlation observed between peak of ionization with target properties. - Abstract: This article presents cross section calculations for interactions of important cyanides with electrons possessing energies beginning from ionization threshold of the target molecule to 5 keV. These data are pursued to meet the ever increasing demand for cross sections by the relevant atomic and molecular community for modelling astrophysical, atmospheric and technological domains. The calculations have been executed using an amalgam of multi centre spherical complex optical potential (MSCOP) formalism and complex scattering potential-ionization contribution (CSP-ic) method. Cross sections are compared with experimental and theoretical data wherever available. Strong correlations are observed for the cross sections which affirms consistent and reliable cross sections. Isomeric effect has been interpreted using variation of cross section with structure and target properties. Our cross sections will be tabulated in atomic collision database for use in modelling various statistical and dynamical quantities.

  17. Cross section data for ionization of important cyanides

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Jaspreet; Antony, Bobby, E-mail: bka.ism@gmail.com

    2015-11-15

    Highlights: • Multi centre spherical complex optical potential formalism used to find the CS. • Effective method (CSP-ic) to derive ionization contribution from inelastic CS. • Result shows excellent accord with previous results and consistent behaviour. • Maiden attempt to find CS for many cyanide molecules. • Strong correlation observed between peak of ionization with target properties. - Abstract: This article presents cross section calculations for interactions of important cyanides with electrons possessing energies beginning from ionization threshold of the target molecule to 5 keV. These data are pursued to meet the ever increasing demand for cross sections by the relevant atomic and molecular community for modelling astrophysical, atmospheric and technological domains. The calculations have been executed using an amalgam of multi centre spherical complex optical potential (MSCOP) formalism and complex scattering potential-ionization contribution (CSP-ic) method. Cross sections are compared with experimental and theoretical data wherever available. Strong correlations are observed for the cross sections which affirms consistent and reliable cross sections. Isomeric effect has been interpreted using variation of cross section with structure and target properties. Our cross sections will be tabulated in atomic collision database for use in modelling various statistical and dynamical quantities.

  18. Modeling ionization by helicon waves

    International Nuclear Information System (INIS)

    Degeling, A.W.; Boswell, R.W.

    1997-01-01

    The response of the electron distribution function in one dimension to a traveling wave electric field is modeled for parameters relevant to a low-pressure helicon wave plasma source, and the resulting change in the ionization rate calculated. This is done by calculating the trajectories of individual electrons in a given wave field and assuming no collisions to build up the distribution function as the distance from the antenna is increased. The ionization rate is calculated for argon by considering the ionization cross section and electron flux at a specified position and time relative to the left-hand boundary, where the distribution function is assumed to be Maxwellian and the wave travels to the right. The simulation shows pulses in the ionization rate that move away from the antenna at the phase velocity of the wave, demonstrating the effect of resonant electrons trapped in the wave close-quote s frame of reference. It is found that the ionization rate is highest when the phase velocity of the wave is between 2 and 3x10 6 m/s, where the electrons interacting strongly with the wave (i.e., electrons with velocities inside the wave close-quote s open-quotes trapping widthclose quotes) have initial energies just below the ionization threshold. Results from the model are compared with experimental data and show reasonable qualitative agreement. copyright 1997 American Institute of Physics

  19. Strong suppression of the positronium channel in double ionization of noble gases by positron impact

    DEFF Research Database (Denmark)

    Bluhme, H.; Knudsen, H.; Merrison, J.P.

    1998-01-01

    Positron-induced double ionization of helium and neon has been studied at energies from threshold to 900 eV. A remarkable difference between the near-threshold behavior of the single and double ionization cross sections is found: Single ionization is dominated by positronium (Ps) formation, while...

  20. Stability results of a free air ionization chamber in standard mammography beams

    International Nuclear Information System (INIS)

    Silva, Natalia F.; Xavier, Marcos; Vivolo, Vitor; Caldas, Linda V.E.

    2015-01-01

    Free air ionization chambers are absolute dosimeters, because they can measure basic physical quantities directly without the need of their calibration in a standard radiation beam. They are used for measuring exposure and air kerma in X and gamma radiation beams. The Calibration Laboratory (LCI) of IPEN has a free air ionization chamber of the cylindrical type for low energies. The characterization of this ionization chamber was already performed and reported in a previous study. After a modification in the support of the micrometers used for the movement of the internal cylinder devices, the tests were redone. The objective of this work was to present the new alignment protocol of the free air ionization chamber in low energies of X-ray beams of standard mammography qualities, assuring the positioning reproducibility, and new results of stability tests performed with the application of this protocol will be presented. (author)

  1. Investigations of multiphoton excitation and ionization in a short range potential

    International Nuclear Information System (INIS)

    Susskind, S.M.; Cowley, S.C.; Valeo, E.J.

    1989-02-01

    We introduce an approach to the study of excitation and ionization for a system with a short range potential. In particular, analytical and numerical results are presented for the multiphoton ionization rate, under strong field conditions, of an electron confined by a δ-function potential. 9 refs., 3 figs

  2. Investigations of multiphoton excitation and ionization in a short range potential

    Energy Technology Data Exchange (ETDEWEB)

    Susskind, S.M.; Cowley, S.C.; Valeo, E.J.

    1989-02-01

    We introduce an approach to the study of excitation and ionization for a system with a short range potential. In particular, analytical and numerical results are presented for the multiphoton ionization rate, under strong field conditions, of an electron confined by a delta-function potential. 9 refs., 3 figs.

  3. Analytical Estimates of the Dispersion Curve in Planar Ionization Fronts

    International Nuclear Information System (INIS)

    Arrayas, Manuel; Trueba, Jose L.; Betelu, Santiago; Fontelos, Marco A.

    2009-01-01

    Fingers from ionization fronts for a hydrodynamic plasma model result from a balance between impact ionization and electron diffusion in a non-attaching gas. An analytical estimation of the size of the fingers and its dependence on both the electric field and electron diffusion coefficient can be done when the diffusion is low and the electric field is strong.

  4. Rapid ionization of the environment of SN 1987A

    International Nuclear Information System (INIS)

    Raga, A.C.

    1987-01-01

    It has been suggested by some authors that IUE observations of the supernova SN 1987A show the presence of a strong component of the interstellar C IV 1550 and Si IV 1393 absorption lines at a velocity that approximately corresponds to the velocity of the LMC. It is possible that this component might come from originally neutral (or at least not very highly ionized) gas which has been photoionized by the initially very strong ionizing radiation field of the supernova. Theoretical considerations of this scenario lead to the study of fast (with velocities of about c) ionization fronts. It is shown that for reasonable model parameters it is possible to obtain considerably large C IV column densities, in agreement with the IUE observations. On the other hand, the models do not so easily predict the large Si IV column densities that are also obtained from the IUE observations. It is found that only models in which the interstellar medium surrounding SN 1987A is initially composed of already ionized hydrogen and helium predict substantial Si IV column densities. This result provides an interesting prediction of the ionization state of the environment of the presupernova star. 9 references

  5. Rapid ionization of the environment of SN 1987A

    Science.gov (United States)

    Raga, A. C.

    1987-01-01

    It has been suggested by some authors that IUE observations of the supernova SN 1987A show the presence of a strong component of the interstellar C IV 1550 and Si IV 1393 absorption lines at a velocity that approximately corresponds to the velocity of the LMC. It is possible that this component might come from originally neutral (or at least not very highly ionized) gas which has been photoionized by the initially very strong ionizing radiation field of the supernova. Theoretical considerations of this scenario lead to the study of fast (with velocities of about c) ionization fronts. It is shown that for reasonable model parameters it is possible to obtain considerably large C IV column densities, in agreement with the IUE observations. On the other hand, the models do not so easily predict the large Si IV column densities that are also obtained from the IUE observations. It is found that only models in which the interstellar medium surrounding SN 1987A is initially composed of already ionized hydrogen and helium predict substantial Si IV column densities. This result provides an interesting prediction of the ionization state of the environment of the presupernova star.

  6. Ionization and Coulomb explosion of small uranium oxide clusters

    International Nuclear Information System (INIS)

    Ross, Matt W; Castleman, A W Jr

    2012-01-01

    Femtosecond pulses are used to study the strong-field ionization and subsequent Coulomb explosion of small uranium oxide clusters. The resulting high atomic charge states are explored as a function of laser intensity and compared to ionization rates calculated using semi-classical tunneling theory with sequential ionization potential values. The gap in laser intensity between saturation intensity values for the 7s, 6d, and 5f orbitals are identified and quantified. Extreme charge states of oxygen up to O 4+ are observed indicating multiple ionization enhancement processes occurring within the clusters. The peak splittings of the atomic charge states are explored and compared to previous results on transition metal oxide species. Participation of the 5f orbitals in bonding is clearly identified based on the saturation intensity dependence of oxygen to uranium metal.

  7. Molecular single photon double K-shell ionization

    International Nuclear Information System (INIS)

    Penent, F.; Nakano, M.; Tashiro, M.; Grozdanov, T.P.; Žitnik, M.; Carniato, S.; Selles, P.; Andric, L.; Lablanquie, P.; Palaudoux, J.; Shigemasa, E.; Iwayama, H.; Hikosaka, Y.; Soejima, K.; Suzuki, I.H.; Kouchi, N.; Ito, K.

    2014-01-01

    We have studied single photon double K-shell ionization of small molecules (N 2 , CO, C 2 H 2n (n = 1–3), …) and the Auger decay of the resulting double core hole (DCH) molecular ions thanks to multi-electron coincidence spectroscopy using a magnetic bottle time-of-flight spectrometer. The relative cross-sections for single-site (K −2 ) and two-site (K −1 K −1 ) double K-shell ionization with respect to single K-shell (K −1 ) ionization have been measured that gives important information on the mechanisms of single photon double ionization. The spectroscopy of two-site (K −1 K −1 ) DCH states in the C 2 H 2n (n = 1–3) series shows important chemical shifts due to a strong dependence on the C-C bond length. In addition, the complete cascade Auger decay following single site (K −2 ) ionization has been obtained

  8. Interaction of strong electromagnetic fields with atoms

    International Nuclear Information System (INIS)

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

    1982-06-01

    Several non-linear processes involvoing the interaction of atoms with strong laser fields are discussed, with particular emphasis on the ionization problem. Non-perturbative methods which have been proposed to tackle this problem are analysed, and shown to correspond to an expansion in the intra-atomic potential. The relation between tunneling and multiphoton absorption as ionization mechanisms, and the generalization of Einstein's photoelectric equation to the strong-field case are discussed. (Author) [pt

  9. Strong-field dissociation dynamics

    International Nuclear Information System (INIS)

    DiMauro, L.F.; Yang, Baorui.

    1993-01-01

    The strong-field dissociation behavior of diatomic molecules is examined under two distinctive physical scenarios. In the first scenario, the dissociation of the isolated hydrogen and deuterium molecular ions is discussed. The dynamics of above-threshold dissociation (ATD) are investigated over a wide range of green and infrared intensities and compared to a dressed-state model. The second situation arises when strong-field neutral dissociation is followed by ionization of the atomic fragments. The study results in a direct measure of the atomic fragment's ac-Stark shift by observing the intensity-dependent shifts in the electron or nuclear fragment kinetic energy. 8 figs., 14 refs

  10. Probing the ionization wave packet and recollision dynamics with an elliptically polarized strong laser field in the nondipole regime

    Science.gov (United States)

    Maurer, J.; Willenberg, B.; Daněk, J.; Mayer, B. W.; Phillips, C. R.; Gallmann, L.; Klaiber, M.; Hatsagortsyan, K. Z.; Keitel, C. H.; Keller, U.

    2018-01-01

    We explore ionization and rescattering in strong mid-infrared laser fields in the nondipole regime over the full range of polarization ellipticity. In three-dimensional photoelectron momentum distributions (3D PMDs) measured with velocity map imaging spectroscopy, we observe the appearance of a sharp ridge structure along the major polarization axis. Within a certain range of ellipticity, the electrons in this ridge are clearly separated from the two lobes that commonly appear in the PMD with elliptically polarized laser fields. In contrast to the well-known lobes of direct electrons, the sharp ridge is created by Coulomb focusing of the softly recolliding electrons. These ridge electrons are directly related to a counterintuitive shift of the PMD peak opposite to the laser beam propagation direction when the dipole approximation breaks down. The ellipticity-dependent 3D PMDs give access to different ionization and recollision dynamics with appropriate filters in the momentum space. For example, we can extract information about the spread of the initial wave packet and the Coulomb momentum transfer of the rescattering electrons.

  11. Strong-Field Control of Laser Filamentation Mechanisms

    Science.gov (United States)

    Levis, Robert; Romanov, Dmitri; Filin, Aleskey; Compton, Ryan

    2008-05-01

    The propagation of short strong-file laser pulses in gas and solution phases often result in formation of filaments. This phenomenon involves many nonlinear processes including Kerr lensing, group velocity dispersion, multi-photon ionization, plasma defocusing, intensity clamping, and self-steepening. Of these, formation and dynamics of pencil-shape plasma areas plays a crucial role. The fundamental understanding of these laser-induced plasmas requires additional effort, because the process is highly nonlinear and complex. We studied the ultrafast laser-generated plasma dynamics both experimentally and theoretically. Ultrafast plasma dynamics was probed using Coherent Anti-Stokes Raman Scattering. The measurements were made in a room temperature gas maintained at 1 atm in a flowing cell. The time dependent scattering was measured by delaying the CARS probe with respect to the intense laser excitation pulse. A general trend is observed between the spacing of the ground state and the first allowed excited state with the rise time for the noble gas series and the molecular gases. This trend is consistent with our theoretical model, which considers the ultrafast dynamics of the strong field generated plasma as a three-step process; (i) strong-field ionization followed by the electron gaining considerable kinetic energy during the pulse; (ii) immediate post-pulse dynamics: fast thermalization, impact-ionization-driven electron multiplication and cooling; (iii) ensuing relaxation: evolution to electron-ion equilibrium and eventual recombination.

  12. Exciton ionization in multilayer transition-metal dichalcogenides

    DEFF Research Database (Denmark)

    Pedersen, Thomas Garm; Latini, Simone; Thygesen, Kristian Sommer

    2016-01-01

    Photodetectors and solar cells based on materials with strongly bound excitons rely crucially on field-assisted exciton ionization. We study the ionization process in multilayer transition-metal dichalcogenides (TMDs) within the Mott-Wannier model incorporating fully the pronounced anisotropy...

  13. Ionization induced by strong electromagnetic field in low dimensional systems bound by short range forces

    Energy Technology Data Exchange (ETDEWEB)

    Eminov, P.A., E-mail: peminov@mail.ru [Moscow State University of Instrument Engineering and Computer Sciences, 20 Stromynka Street, Moscow 2107996 (Russian Federation); National Research University Higher School of Economics, 3/12 Bolshoy Trekhsvyatskiy pereulok, Moscow 109028 (Russian Federation)

    2013-10-01

    Ionization processes for a two dimensional quantum dot subjected to combined electrostatic and alternating electric fields of the same direction are studied using quantum mechanical methods. We derive analytical equations for the ionization probability in dependence on characteristic parameters of the system for both extreme cases of a constant electric field and of a linearly polarized electromagnetic wave. The ionization probabilities for a superposition of dc and low frequency ac electric fields of the same direction are calculated. The impulse distribution of ionization probability for a system bound by short range forces is found for a superposition of constant and alternating fields. The total probability for this process per unit of time is derived within exponential accuracy. For the first time the influence of alternating electric field on electron tunneling probability induced by an electrostatic field is studied taking into account the pre-exponential term.

  14. Atoms in strong laser fields

    International Nuclear Information System (INIS)

    L'Huillier, A.

    2002-01-01

    When a high-power laser focuses into a gas of atoms, the electromagnetic field becomes of the same magnitude as the Coulomb field which binds a 1s electron in a hydrogen atom. 3 highly non-linear phenomena can happen: 1) ATI (above threshold ionization): electrons initially in the ground state absorb a large number of photons, many more than the minimum number required for ionization; 2) multiple ionization: many electrons can be emitted one at a time, in a sequential process, or simultaneously in a mechanism called direct or non-sequential; and 3) high order harmonic generation (HHG): efficient photon emission in the extreme ultraviolet range, in the form of high-order harmonics of the fundamental laser field can occur. The theoretical problem consists in solving the time dependent Schroedinger equation (TDSE) that describes the interaction of a many-electron atom with a laser field. A number of methods have been proposed to solve this problem in the case of a hydrogen atom or a single-active electron atom in a strong laser field. A large effort is presently being devoted to go beyond the single-active approximation. The understanding of the physics of the interaction between atoms and strong laser fields has been provided by a very simple model called ''simple man's theory''. A unified view of HHG, ATI, and non-sequential ionization, originating from the simple man's model and the strong field approximation, expressed in terms of electrons trajectories or quantum paths is slowly emerging. (A.C.)

  15. An approximate method to calculate ionization of LTE and non-LTE plasma

    International Nuclear Information System (INIS)

    Zhang Jun; Gu Peijun

    1987-01-01

    When matter, especially high Z element, is heated to high temperature, it will be ionized many times. The degree of ionization has a strong effect on many plasma properties. So an approximate method to calculate the mean ionization degree is needed for solving many practical problems. An analytical expression which is convenient for the approximate numerical calculation is given by fitting it to the scaling law and numerical results of the ionization potential of Thomas-Fermi statistical model. In LTE case, the ionization degree of Au calculated by using the approximate method is in agreement with that of the average ion model. By extending the approximate method to non-LTE case, the ionization degree of Au is similarly calculated according to Corona model and Collision-Radiatoin model(C-R). The results of Corona model agree with the published data quite well, while the results of C-R approach those of Corona model as the density is reduced and approach those of LTE as the density is increased. Finally, all approximately calculated results of ionization degree of Au and the comparision of them are given in figures and tables

  16. Further 'comment on 'Generalized Bessel functions in tunnelling ionization''

    International Nuclear Information System (INIS)

    Reiss, H R; Krainov, V P

    2005-01-01

    J Bauer, in commenting on our tunnelling approximation for the generalized Bessel function, points out that when the approximation is applied to strong-field ionization, it is suitable only for the lowest-energy part of an ionization spectrum. We do not disagree. We point out several things: the results of Bauer are to be expected; linear polarization results are dominated by the lowest part of the multiphoton spectrum; and we do not recommend practical use of this tunnelling approximation, since the asymptotic approximation is so much better. We show comparisons of momentum distributions calculated with the tunnelling approximation and those with the complete strong-field approximation, which show in more detail than spectrum comparisons that the tunnelling approximation to the generalized Bessel function is applicable only to the low-momentum part of the distribution, and neglects altogether the high-momentum portion. (reply)

  17. Propagation of sound and thermal waves in an ionizing-recombining hydrogen plasma: Revision of results

    International Nuclear Information System (INIS)

    Di Sigalotti, Leonardo G.; Sira, Eloy; Tremola, Ciro

    2002-01-01

    The propagation of acoustic and thermal waves in a heat conducting, hydrogen plasma, in which photoionization and photorecombination [H + +e - H+hν(χ)] processes are progressing, is re-examined here using linear analysis. The resulting dispersion equation is solved analytically and the results are compared with previous solutions for the same plasma model. In particular, it is found that wave propagation in a slightly and highly ionized hydrogen plasma is affected by crossing between acoustic and thermal modes. At temperatures where the plasma is partially ionized, waves of all frequencies propagate without the occurrence of mode crossing. These results disagree with those reported in previous work, thereby leading to a different physical interpretation of the propagation of small linear disturbances in a conducting, ionizing-recombining, hydrogen plasma

  18. Influence of Dust Loading on Atmospheric Ionizing Radiation on Mars

    Science.gov (United States)

    Norman, Ryan B.; Gronoff, Guillaume; Mertens, Christopher J.

    2014-01-01

    Measuring the radiation environment at the surface of Mars is the primary goal of the Radiation Assessment Detector on the NASA Mars Science Laboratory's Curiosity rover. One of the conditions that Curiosity will likely encounter is a dust storm. The objective of this paper is to compute the cosmic ray ionization in different conditions, including dust storms, as these various conditions are likely to be encountered by Curiosity at some point. In the present work, the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety model, recently modified for Mars, was used along with the Badhwar & O'Neill 2010 galactic cosmic ray model. In addition to galactic cosmic rays, five different solar energetic particle event spectra were considered. For all input radiation environments, radiation dose throughout the atmosphere and at the surface was investigated as a function of atmospheric dust loading. It is demonstrated that for galactic cosmic rays, the ionization depends strongly on the atmosphere profile. Moreover, it is shown that solar energetic particle events strongly increase the ionization throughout the atmosphere, including ground level, and can account for the radio blackout conditions observed by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument on the Mars Express spacecraft. These results demonstrate that the cosmic rays' influence on the Martian surface chemistry is strongly dependent on solar and atmospheric conditions that should be taken into account for future studies.

  19. Some of the results of the protection measures in the field of ionizing radiation at FRY border crossings

    International Nuclear Information System (INIS)

    Benderac, R.; Kokotovic, J.; Kolundzija, V.

    2002-01-01

    Full text: SUMMARY: The paper describes some of the results of the protection measures in the field of ionizing radiation at FRY border crossings where there were placed stationary monitors of gamma-radiation. The Institute of Security as licensed institution for ionizing radiation detection, designed and placed stationary devices MZ - 100 at border crossings check points named Kelebija, Horgos, Vatin, Gradina, Presevo, Djeneral Jankovic, Batrovci and the ship lock 'Djerdap-I'. CONCLUSION: Over the several years ago IAEA and its member states as well as other international organizations have become increasingly aware of the consequences which might result from illegal activities involving these materials. Therefore initiatives to strengthen physical protection regime are strongly supported and steps towards improving security of nuclear and other radioactive material have already been taken. Yugoslavia as IAEA member state wishes to contribute to the all together efforts in reducing the possibility of illegal activities such as theft, sabotage and trafficking, involving nuclear materials and other radioactive materials, and on the associated proliferation threat and radiation risks. Therefore relevant national bodies prepare project proposal titled 'PREVENTION OF ILLICIT TRAFFICKING IN NUCLEAR AND RADIOACTIVE MATERIALS IN THE FEDERAL REPUBLIC OF YUGOSLAVIA'. Significant work is ahead in this field, since harmonization of radiological control at our border crossings must be achieved. (author)

  20. Dynamic conductivity and partial ionization in dense fluid hydrogen

    Science.gov (United States)

    Zaghoo, Mohamed

    2018-04-01

    A theoretical description for optical conduction experiments in dense fluid hydrogen is presented. Different quantum statistical approaches are used to describe the mechanism of electronic transport in hydrogen's high-temperature dense phase. We show that at the onset of the metallic transition, optical conduction could be described by a strong rise in atomic polarizability, due to increased ionization, whereas in the highly degenerate limit, the Ziman weak scattering model better accounts for the observed saturation of reflectance. The inclusion of effects of partial ionization in the highly degenerate region provides great agreement with experimental results. Hydrogen's fluid metallic state is revealed to be a partially ionized free-electron plasma. Our results provide some of the first theoretical transport models that are experimentally benchmarked, as well as an important guide for future studies.

  1. Update of NIST half-life results corrected for ionization chamber source-holder instability.

    Science.gov (United States)

    Unterweger, M P; Fitzgerald, R

    2014-05-01

    As reported at the ICRM 2011, it was discovered that the source holder used for calibrations in the NIST 4πγ ionization chamber (IC) was not stable. This has affected a large number of half-life measurement results previously reported and used in compilations of nuclear data. Corrections have been made on all of the half-life data based on the assumption that the changes to the ionization chamber response were gradual. The corrections are energy dependent and therefore radionuclide specific. This presentation will review our results and present the recommended changes in half-life values and/or uncertainties. © 2013 Published by Elsevier Ltd.

  2. Atomic processes in strong bichromatic elliptically polarized laser fields

    Energy Technology Data Exchange (ETDEWEB)

    Odžak, S., E-mail: senad.odzak@gmail.com; Hasović, E.; Gazibegović-Busuladžić, A.; Čerkić, A., E-mail: anercerkic@yahoo.com; Fetić, B. [Faculty of Science, University of Sarajevo, Zmaja od Bosne 35, 71000 Sarajevo (Bosnia and Herzegovina); Kramo, A. [BHANSA, Aeronautical Meteorology Department, Kurta Schorka 36, 71000 Sarajevo (Bosnia and Herzegovina); Busuladžić, M. [Medical Faculty, University of Sarajevo, Čekaluša 90, 71000 Sarajevo (Bosnia and Herzegovina); Milošević, D. B. [Faculty of Science, University of Sarajevo, Zmaja od Bosne 35, 71000 Sarajevo (Bosnia and Herzegovina); Academy of Sciences and Arts of Bosnia and Herzegovina, Bistrik 7, 71000 Sarajevo (Bosnia and Herzegovina); Max-Born-Institut, Max-Born-Strasse 2a, 12489 Berlin (Germany)

    2016-03-25

    Nonlinear quantum-mechanical phenomena in strong laser fields, such as high-order harmonic generation (HHG) and above-threshold ionization (ATI) are significantly modified if the applied laser field is bichromatic and/or elliptically polarized. Numerical results obtained within the strong-field approximation are presented for two special cases. We show results for HHG by plasma ablation in a bichromatic linearly polarized laser field. We also consider the ATI process in bicircular field which consists of two coplanar counter-rotating circularly polarized fields.

  3. Ionizing and non-ionizing radiations

    International Nuclear Information System (INIS)

    1994-01-01

    The monograph is a small manual to get a knowledge of ionizing and non-ionizing radiations. The main chapters are: - Electromagnetic radiations - Ionizing and non-ionizing radiations - Non-ionizing electromagnetic radiations - Ionizing electromagnetic radiation - Other ionizing radiations - Ionizing radiation effects - The Nuclear Safety Conseil

  4. Effect of negative ions on current growth and ionizing wave propagation in air

    International Nuclear Information System (INIS)

    Kline, L.E.

    1975-01-01

    The spatiotemporal development of electron and ion densities, electric fields, and luminosity are calculated for electron pulse experiments in overvolted parallel-plane gaps by numerically solving continuity equations together with Poisson's equation. Experimental coefficients for primary ionization, cathode photoemission, photoionization, and luminosity are used. Unambiguous determination of the coefficients for attachment, detachment, and charge transfer is not possible from available experimental results. Therefore, the calculations are repeated for three sets of coefficients for these processes, corresponding to the following assumptions: unstable negative ions, stable negative ions, and no negative ions. The results of the calculations show, in each case, that the electron pulse initiates an avalanche which grows exponentially until the onset of space-charge effects. The calculated growth rate is strongly affected by the assumed attachment, detachment, and charge-transfer coefficients. When the total number of electrons in the avalanche reaches approx.10 8 , anode- and cathode-directed ionizing waves, or streamers, develop from the avalanche and produce a weakly ionized filamentary plasma. The calculated ionizing wave velocities are strongly increasing functions of the space-charge--enhanced electric field within the waves and are insensitive to the assumed attachment, detachment, and charge-transfer coefficients. The numerically calculated ionizing wave velocities are in approximate agreement with a simple analytical theory

  5. Dynamics of tunneling ionization using Bohmian mechanics

    Science.gov (United States)

    Douguet, Nicolas; Bartschat, Klaus

    2018-01-01

    Recent attoclock experiments and theoretical studies regarding the strong-field ionization of atoms by few-cycle infrared pulses revealed features that have attracted much attention. Here we investigate tunneling ionization and the dynamics of the electron probability using Bohmian mechanics. We consider a one-dimensional problem to illustrate the underlying mechanisms of the ionization process. It is revealed that in the major part of the below-the-barrier ionization regime, in an intense and short infrared pulse, the electron does not tunnel through the entire barrier, but rather starts already from the classically forbidden region. Moreover, we highlight the correspondence between the probability of locating the electron at a particular initial position and its asymptotic momentum. Bohmian mechanics also provides a natural definition of mean tunneling time and exit position, taking account of the time dependence of the barrier. Finally, we find that the electron can exit the barrier with significant kinetic energy, thereby corroborating the results of a recent study [N. Camus et al., Phys. Rev. Lett. 119, 023201 (2017), 10.1103/PhysRevLett.119.023201].

  6. Update of NIST half-life results corrected for ionization chamber source-holder instability

    International Nuclear Information System (INIS)

    Unterweger, M.P.; Fitzgerald, R.

    2014-01-01

    As reported at the ICRM 2011, it was discovered that the source holder used for calibrations in the NIST 4πγ ionization chamber (IC) was not stable. This has affected a large number of half-life measurement results previously reported and used in compilations of nuclear data. Corrections have been made on all of the half-life data based on the assumption that the changes to the ionization chamber response were gradual. The corrections are energy dependent and therefore radionuclide specific. This presentation will review our results and present the recommended changes in half-life values and/or uncertainties. - Highlights: • The NIST half-life data is corrected for sample positioning variations and refitted. • These results are reported and increased errors in the reported values are given. • Longer lived radionuclides are discussed

  7. On possible structures of transverse ionizing shock waves

    International Nuclear Information System (INIS)

    Liberman, M.A.; Velikovich, A.L.

    1978-01-01

    The possible structures of ionizing shock waves propagating in gases across the magnetic field are investigated taking account of both ionization kinetics and the non-isothermality of the plasma which is formed within the shock front. It is shown that a definite factor in shaping the structure of the transverse ionizing shock wave is photo-ionization of the neutral gas across the front. The paper includes a study of the evolution of the transverse ionizing shock front with regard to photo-ionization, disclosing that a stable stationary shock structure emerges only in boundary conditions which are close to magnetohydrodynamic ones, i.e. upsilon 1 H 1 = upsilon 2 H 2 . In the case of strong transverse ionizing shock waves, when the flux of ionizing radiation across the front is great, the shock structure is obviously magnetohydrodynamic. (author)

  8. Microwave ionization of hydrogen atoms below the classical chaos border

    Energy Technology Data Exchange (ETDEWEB)

    Bluemel, R; Smilansky, U

    1987-01-01

    We present and discuss theoretical predictions for the occurrence of radiation induced ionization of hydrogen atoms in fields which are well below the classical ionization threshold. Strong ionization occurs due to enhanced population of a band of high n states which ionize easily. This enhancement happens only at rather narrowly defined field values, and is explained in terms of avoided crossings of Floquet levels.

  9. X-RAY SIGNATURES OF NON-EQUILIBRIUM IONIZATION EFFECTS IN GALAXY CLUSTER ACCRETION SHOCK REGIONS

    International Nuclear Information System (INIS)

    Wong, Ka-Wah; Sarazin, Craig L.; Ji Li

    2011-01-01

    The densities in the outer regions of clusters of galaxies are very low, and the collisional timescales are very long. As a result, heavy elements will be under-ionized after they have passed through the accretion shock. We have studied systematically the effects of non-equilibrium ionization for relaxed clusters in the ΛCDM cosmology using one-dimensional hydrodynamic simulations. We found that non-equilibrium ionization effects do not depend on cluster mass, but depend strongly on redshift which can be understood by self-similar scaling arguments. The effects are stronger for clusters at lower redshifts. We present X-ray signatures such as surface brightness profiles and emission lines in detail for a massive cluster at low redshift. In general, soft emission (0.3-1.0 keV) is enhanced significantly by under-ionization, and the enhancement can be nearly an order of magnitude near the shock radius. The most prominent non-equilibrium ionization signature we found is the O VII and O VIII line ratio. The ratios for non-equilibrium ionization and collisional ionization equilibrium models are different by more than an order of magnitude at radii beyond half of the shock radius. These non-equilibrium ionization signatures are equally strong for models with different non-adiabatic shock electron heating efficiencies. We have also calculated the detectability of the O VII and O VIII lines with the future International X-ray Observatory (IXO). Depending on the line ratio measured, we conclude that an exposure of ∼130-380 ks on a moderate-redshift, massive regular cluster with the X-ray Microcalorimeter Spectrometer (XMS) on the IXO will be sufficient to provide a strong test for the non-equilibrium ionization model.

  10. III. Penning ionization, associative ionization and chemi-ionization processes

    International Nuclear Information System (INIS)

    Cermak, V.

    1975-01-01

    Physical mechanisms of three important ionization processes in a cold plasma and the methods of their experimental study are discussed. An apparatus for the investigation of the Penning ionization using ionization processes of long lived metastable rare gas atoms is described. Methods of determining interaction energies and ionization rates from the measured energy spectra of the originating electrons are described and illustrated by several examples. Typical associative ionization processes are listed and the ionization rates are compared with those of the Penning ionization. Interactions with short-lived excited particles and the transfer of excitation without ionization are discussed. (J.U.)

  11. Impact of Coulomb potential on peak structures arising in momentum and low-energy photoelectron spectra produced in strong-field ionization of laser-irradiated atoms

    Science.gov (United States)

    Pyak, P. E.; Usachenko, V. I.

    2018-03-01

    The phenomenon of pronounced peak structure(s) of longitudinal momentum distributions as well as a spike-like structure of low-energy spectra of photoelectrons emitted from laser-irradiated Ar and Ne atoms in a single ionization process is theoretically studied in the tunneling and multiphoton regimes of ionization. The problem is addressed assuming only the direct above-threshold ionization (ATI) as a physical mechanism underlying the phenomenon under consideration (viz. solely contributing to observed photoelectron momentum distributions (PMD)) and using the Coulomb-Volkov (CV) ansatz within the frame of conventional strong-field approximation (SFA) applied in the length-gauge formulation. The developed CV-SFA approach also incorporates the density functional theory essentially exploited for numerical composition of initial (laser-free) atomic state(s) constructed from atomic orbitals of Gaussian type. Our presented CV-SFA based (and laser focal-volume averaged) calculation results proved to be well reproducing both the pronounced double-peak and/or ATI-like multi-peak structure(s) experimentally observed in longitudinal PMD under conditions of tunneling and/or multiphoton regime, respectively. In addition, our CV-SFA results presented for tunneling regime also suggest and remarkably reproduce a pronounced structure observed in relevant experiments as a ‘spike-like’ enhanced maximum arising in low-energy region (around the value of about 1 eV) of photoelectron spectra. The latter consistency allows to identify and interpret these results as the so-called low-energy structure (LES) since the phenomenon proved to appear as the most prominent if the influence of Coulomb potential on photoelectron continuum states is maximally taken into account under calculations (viz. if the parameter Z in CV’s functions is put equal to 1). Moreover, the calculated LES proved to correspond (viz., established as closely related) to the mentioned double-peak structure arising

  12. Charge correlation effects on ionization of weak polyelectrolytes

    International Nuclear Information System (INIS)

    Panagiotopoulos, A Z

    2009-01-01

    Ionization curves of weak polyelectrolytes were obtained as a function of the charge coupling strength from Monte Carlo simulations. In contrast to many earlier studies, the present work treats counterions explicitly, thus allowing the investigation of charge correlation effects at strong couplings. For conditions representing typical weak polyelectrolytes in water near room temperature, ionization is suppressed because of interactions between nearby dissociated groups, as also seen in prior work. A novel finding here is that, for stronger couplings, relevant for non-aqueous environments in the absence of added salt, the opposite behavior is observed-ionization is enhanced relative to the behavior of the isolated groups due to ion-counterion correlation effects. The fraction of dissociated groups as a function of position along the chain also behaves non-monotonically. Dissociation is highest near the ends of the chains for aqueous polyelectrolytes and highest at the chain middle segments for non-aqueous environments. At intermediate coupling strengths, dissociable groups appear to behave in a nearly ideal fashion, even though chain dimensions still show strong expansion effects due to ionization. These findings provide physical insights on the impact of competition between acid/base chemical equilibrium and electrostatic attractions in ionizable systems.

  13. Atom ionization in a nonclassical intense electromagnetic field

    International Nuclear Information System (INIS)

    Popov, A.M.; Tikhonova, O.V.

    2002-01-01

    The atoms ionization process in the intense nonclassical electromagnetic field is considered. It is shown that depending on the field quantum state the probability of ionization may essentially change even by one and the same average quantum number in the radiation mode, whereby the difference in the ionization rates is especially significant in the case, when the ionization process is of a multiphoton character. It is demonstrates in particular, that the nonclassical field may be considerably more intensive from the viewpoint of the atoms ionization, than the classical field with the same intensity. The peculiarities of the decay, related to the atomic system state in the strong nonclassical field beyond the perturbation theory frames are studied [ru

  14. Microwave Ionization of an Atomic Electron Wave Packet

    International Nuclear Information System (INIS)

    Noel, Michael W.; Ko, Lung; Gallagher, T. F.

    2001-01-01

    A short microwave pulse is used to ionize a lithium Rydberg wave packet launched from the core at a well-defined phase of the field. We observe a strong dependence on the relative phase between the motion of the wave packet and the oscillations of the field. This phase dependent ionization is also studied as a function of the relative frequency. Our experimental observations are in good qualitative agreement with a one-dimensional classical model of wave packet ionization

  15. Subcycle dynamics of Coulomb asymmetry in strong elliptical laser fields.

    Science.gov (United States)

    Li, Min; Liu, Yunquan; Liu, Hong; Ning, Qicheng; Fu, Libin; Liu, Jie; Deng, Yongkai; Wu, Chengyin; Peng, Liang-You; Peng, Liangyou; Gong, Qihuang

    2013-07-12

    We measure photoelectron angular distributions of noble gases in intense elliptically polarized laser fields, which indicate strong structure-dependent Coulomb asymmetry. Using a dedicated semiclassical model, we have disentangled the contribution of direct ionization and multiple forward scattering on Coulomb asymmetry in elliptical laser fields. Our theory quantifies the roles of the ionic potential and initial transverse momentum on Coulomb asymmetry, proving that the small lobes of asymmetry are induced by direct ionization and the strong asymmetry is induced by multiple forward scattering in the ionic potential. Both processes are distorted by the Coulomb force acting on the electrons after tunneling. Lowering the ionization potential, the relative contribution of direct ionization on Coulomb asymmetry substantially decreases and Coulomb focusing on multiple rescattering is more important. We do not observe evident initial longitudinal momentum spread at the tunnel exit according to our simulation.

  16. Strong-field ionization of linear molecules by a bicircular laser field: Symmetry considerations

    Science.gov (United States)

    Gazibegović-Busuladžić, A.; Busuladžić, M.; Hasović, E.; Becker, W.; Milošević, D. B.

    2018-04-01

    Using the improved molecular strong-field approximation, we investigate (high-order) above-threshold ionization [(H)ATI] of various linear polyatomic molecules by a two-color laser field of frequencies r ω and s ω (with integer numbers r and s ) having coplanar counter-rotating circularly polarized components (a so-called bicircular field). Reflection and rotational symmetries for molecules aligned in the laser-field polarization plane, analyzed for diatomic homonuclear molecules in Phys. Rev. A 95, 033411 (2017), 10.1103/PhysRevA.95.033411, are now considered for diatomic heteronuclear molecules and symmetric and asymmetric linear triatomic molecules. There are additional rotational symmetries for (H)ATI spectra of symmetric linear molecules compared to (H)ATI spectra of the asymmetric ones. It is shown that these symmetries manifest themselves differently for r +s odd and r +s even. For example, HATI spectra for symmetric molecules with r +s even obey inversion symmetry. For ATI spectra of linear molecules, reflection symmetry appears only for certain molecular orientation angles ±90∘-j r 180∘/(r +s ) (j integer). For symmetric linear molecules, reflection symmetry appears also for the angles -j r 180∘/(r +s ) . For perpendicular orientation of molecules with respect to the laser-field polarization plane, the HATI spectra are very similar to those of the atomic targets, i.e., both spectra are characterized by the same type of the (r +s )-fold symmetry.

  17. Resonance ionization spectroscopy in dysprosium

    Energy Technology Data Exchange (ETDEWEB)

    Studer, D., E-mail: dstuder@uni-mainz.de; Dyrauf, P.; Naubereit, P.; Heinke, R.; Wendt, K. [Johannes Gutenberg-Universität Mainz, Institut für Physik (Germany)

    2017-11-15

    We report on resonance ionization spectroscopy (RIS) of high-lying energy levels in dysprosium. We developed efficient excitation schemes and re-determined the first ionization potential (IP) via analysis of Rydberg convergences. For this purpose both two- and three-step excitation ladders were investigated. An overall ionization efficiency of 25(4) % could be demonstrated in the RISIKO mass separator of Mainz University, using a three-step resonance ionization scheme. Moreover, an extensive analysis of the even-parity 6sns- and 6snd-Rydberg-series convergences, measured via two-step excitation was performed. To account for strong perturbations in the observed s-series, the approach of multichannel quantum defect theory (MQDT) was applied. Considering all individual series limits we extracted an IP-value of 47901.76(5) cm{sup −1}, which agrees with the current literature value of 47901.7(6) cm{sup −1}, but is one order of magnitude more precise.

  18. Magnetic Reconnection in Strongly Magnetized Regions of the Low Solar Chromosphere

    Science.gov (United States)

    Ni, Lei; Lukin, Vyacheslav S.; Murphy, Nicholas A.; Lin, Jun

    2018-01-01

    Magnetic reconnection in strongly magnetized regions around the temperature minimum region of the low solar atmosphere is studied by employing MHD-based simulations of a partially ionized plasma within a reactive 2.5D multi-fluid model. It is shown that in the absence of magnetic nulls in a low β plasma, the ionized and neutral fluid flows are well-coupled throughout the reconnection region. However, non-equilibrium ionization–recombination dynamics play a critical role in determining the structure of the reconnection region, leading to much lower temperature increases and a faster magnetic reconnection rate as compared to simulations that assume plasma to be in ionization–recombination equilibrium. The rate of ionization of the neutral component of the plasma is always faster than recombination within the current sheet region even when the initial plasma β is as high as {β }0=1.46. When the reconnecting magnetic field is in excess of a kilogauss and the plasma β is lower than 0.0145, the initially weakly ionized plasmas can become fully ionized within the reconnection region and the current sheet can be strongly heated to above 2.5× {10}4 K, even as most of the collisionally dissipated magnetic energy is radiated away. The Hall effect increases the reconnection rate slightly, but in the absence of magnetic nulls it does not result in significant asymmetries or change the characteristics of the reconnection current sheet down to meter scales.

  19. Initial test results of an ionization chamber shower detector for a LHC luminosity monitor

    International Nuclear Information System (INIS)

    Datte, P.; Beche, J.-F.; Haguenauer, M.; Manfredi, P.F.; Manghisoni, M.; Millaud, J.; Placidi, M.; Ratti, L.; Riot, V.; Schmickler, H.; Speziali, V.; Turner, W.

    2002-01-01

    A novel, segmented, multi-gap, pressurized gas ionization chamber is being developed for optimization of the luminosity of the LHC. The ionization chambers are to be installed in the front quadrupole and zero degree neutral particle absorbers in the high luminosity IRs and sample the energy deposited near the maxima of the hadronic/electromagnetic showers in these absorbers. The ionization chambers are instrumented with low noise, fast, pulse shaping electronics to be capable of resolving individual bunch crossings at 40 MHz. In this paper we report the initial results of our second test of this instrumentation in an SPS external proton beam. Single 300 GeV protons are used to simulate the hadronic/electromagnetic shower produced by the forward collision products from the interaction regions of the LHC. The capability of instrumentations to measure the luminosity of individual bunches in a 40 MHz bunch train is demonstrated

  20. Phase Structure of Strong-Field Tunneling Wave Packets from Molecules.

    Science.gov (United States)

    Liu, Ming-Ming; Li, Min; Wu, Chengyin; Gong, Qihuang; Staudte, André; Liu, Yunquan

    2016-04-22

    We study the phase structure of the tunneling wave packets from strong-field ionization of molecules and present a molecular quantum-trajectory Monte Carlo model to describe the laser-driven dynamics of photoelectron momentum distributions of molecules. Using our model, we reproduce and explain the alignment-dependent molecular frame photoelectron spectra of strong-field tunneling ionization of N_{2} reported by M. Meckel et al. [Nat. Phys. 10, 594 (2014)]. In addition to modeling the low-energy photoelectron angular distributions quantitatively, we extract the phase structure of strong-field molecular tunneling wave packets, shedding light on its physical origin. The initial phase of the tunneling wave packets at the tunnel exit depends on both the initial transverse momentum distribution and the molecular internuclear distance. We further show that the ionizing molecular orbital has a critical effect on the initial phase of the tunneling wave packets. The phase structure of the photoelectron wave packet is a key ingredient for modeling strong-field molecular photoelectron holography, high-harmonic generation, and molecular orbital imaging.

  1. <strong>Relative Biological Effect of Antiprotonsstrong>> strong>

    DEFF Research Database (Denmark)

    Bassler, Niels; Holzscheiter, Michael

    nuclear research facility CERN. A beam of 126 MeV antiprotons, corresponding to about 12 cm range in water, was spread out to a SOBP with a width of 1 cm. Dosimetry experiments were carried out with ionization chambers, alanine pellets and radiochromic film, and the results were used for benchmarking...

  2. Atomic and free electrons in a strong light field

    CERN Document Server

    Fedorov, Mikhail V

    1997-01-01

    This book presents and describes a series of unusual and striking strong-field phenomena concerning atoms and free electrons. Some of these phenomena are: multiphoton stimulated bremsstrahlung, free-electron lasers, wave-packet physics, above-threshold ionization, and strong-field stabilization in Rydberg atoms. The theoretical foundations and causes of the phenomena are described in detail, with all the approximations and derivations discussed. All the known and relevant experiments are described too, and their results are compared with those of the existing theoretical models.An extensive ge

  3. Communication: Strong laser alignment of solvent-solute aggregates in the gas-phase

    Science.gov (United States)

    Trippel, Sebastian; Wiese, Joss; Mullins, Terry; Küpper, Jochen

    2018-03-01

    Strong quasi-adiabatic laser alignment of the indole-water-dimer clusters, an amino-acid chromophore bound to a single water molecule through a hydrogen bond, was experimentally realized. The alignment was visualized through ion and electron imaging following strong-field ionization. Molecular-frame photoelectron angular distributions showed a clear suppression of the electron yield in the plane of the ionizing laser's polarization, which was analyzed as strong alignment of the molecular cluster with ⟨cos2 θ2D⟩ ≥ 0.9.

  4. Guided ionization waves: Theory and experiments

    International Nuclear Information System (INIS)

    Lu, X.; Naidis, G.V.; Laroussi, M.; Ostrikov, K.

    2014-01-01

    This review focuses on one of the fundamental phenomena that occur upon application of sufficiently strong electric fields to gases, namely the formation and propagation of ionization waves–streamers. The dynamics of streamers is controlled by strongly nonlinear coupling, in localized streamer tip regions, between enhanced (due to charge separation) electric field and ionization and transport of charged species in the enhanced field. Streamers appear in nature (as initial stages of sparks and lightning, as huge structures—sprites above thunderclouds), and are also found in numerous technological applications of electrical discharges. Here we discuss the fundamental physics of the guided streamer-like structures—plasma bullets which are produced in cold atmospheric-pressure plasma jets. Plasma bullets are guided ionization waves moving in a thin column of a jet of plasma forming gases (e.g., He or Ar) expanding into ambient air. In contrast to streamers in a free (unbounded) space that propagate in a stochastic manner and often branch, guided ionization waves are repetitive and highly-reproducible and propagate along the same path—the jet axis. This property of guided streamers, in comparison with streamers in a free space, enables many advanced time-resolved experimental studies of ionization waves with nanosecond precision. In particular, experimental studies on manipulation of streamers by external electric fields and streamer interactions are critically examined. This review also introduces the basic theories and recent advances on the experimental and computational studies of guided streamers, in particular related to the propagation dynamics of ionization waves and the various parameters of relevance to plasma streamers. This knowledge is very useful to optimize the efficacy of applications of plasma streamer discharges in various fields ranging from health care and medicine to materials science and nanotechnology

  5. Multiple ionization and coupling effects in L-subshell ionization of heavy atoms by oxygen ions

    International Nuclear Information System (INIS)

    Pajek, M.; Banas, D.; Semaniak, J.; Braziewicz, J.; Majewska, U.; Chojnacki, S.; Czyzewski, T.; Fijal, I.; Jaskola, M.; Glombik, A.; Kretschmer, W.; Trautmann, D.; Lapicki, G.; Mukoyama, T.

    2003-01-01

    The multiple-ionization and coupling effects in L-shell ionization of atoms by heavy-ion impact have been studied by measuring the L x-ray production cross sections in solid targets of Au, Bi, Th, and U bombarded by oxygen ions in the energy range 6.4-70 MeV. The measured L x-ray spectra were analyzed using the recently proposed method accounting for the multiple-ionization effects, such as x-ray line shifting and broadening, which enables one to obtain the ionization probabilities for outer shells. The L-subshell ionization cross sections have been obtained from measured x-ray production cross sections for resolved Lα 1,2 , Lγ 1 , and Lγ 2,3 transitions using the L-shell fluorescence and Coster-Kronig yields being substantially modified by the multiple ionization in the M and N shells. In particular, the effect of closing of strong L 1 -L 3 M 4,5 Coster-Kronig transitions in multiple-ionized atoms was evidenced and discussed. The experimental ionization cross sections for the L 1 , L 2 , and L 3 subshells have been compared with the predictions of the semiclassical approximation (SCA) and the ECPSSR theory that includes the corrections for the binding-polarization effect within the perturbed stationary states approximation, the projecticle energy loss, and Coulomb deflection effects as well as the relativistic description of inner-shell electrons. These approaches were further modified to include the L-subshell couplings within the ''coupled-subshell model'' (CSM). Both approaches, when modified for the coupling effects, are in better agreement with the data. Particularly, the predictions of the SCA-CSM calculations reproduce the experimental L-subshell ionization cross section reasonably well. Remaining discrepancies are discussed qualitatively, in terms of further modifications of the L-shell decay rates caused by a change of electronic wave functions in multiple-ionized atoms

  6. NON-EQUILIBRIUM HELIUM IONIZATION IN AN MHD SIMULATION OF THE SOLAR ATMOSPHERE

    International Nuclear Information System (INIS)

    Golding, Thomas Peter; Carlsson, Mats; Leenaarts, Jorrit

    2016-01-01

    The ionization state of the gas in the dynamic solar chromosphere can depart strongly from the instantaneous statistical equilibrium commonly assumed in numerical modeling. We improve on earlier simulations of the solar atmosphere that only included non-equilibrium hydrogen ionization by performing a 2D radiation-magnetohydrodynamics simulation featuring non-equilibrium ionization of both hydrogen and helium. The simulation includes the effect of hydrogen Lyα and the EUV radiation from the corona on the ionization and heating of the atmosphere. Details on code implementation are given. We obtain helium ion fractions that are far from their equilibrium values. Comparison with models with local thermodynamic equilibrium (LTE) ionization shows that non-equilibrium helium ionization leads to higher temperatures in wavefronts and lower temperatures in the gas between shocks. Assuming LTE ionization results in a thermostat-like behavior with matter accumulating around the temperatures where the LTE ionization fractions change rapidly. Comparison of DEM curves computed from our models shows that non-equilibrium ionization leads to more radiating material in the temperature range 11–18 kK, compared to models with LTE helium ionization. We conclude that non-equilibrium helium ionization is important for the dynamics and thermal structure of the upper chromosphere and transition region. It might also help resolve the problem that intensities of chromospheric lines computed from current models are smaller than those observed

  7. Ionization effects in electronic inner-shells of ionized atoms

    International Nuclear Information System (INIS)

    Shchornak, G.

    1983-01-01

    A review of the atomic physics of ionization atoms has been presented. Interaction and structure effects in atomic shells, correlated to the occurrence of vacancies in several subshells of the atom have been considered. The methods of calculations of atomic states and wave functions have been reviewed. The energy shift of characteristic X-rays is discussed as a function of the ionization stage of the atom. The influence of inner and outer-shell vacancies on the energy of the X-rays is shown in detail. The influence of chemical effects on the parameters of X-rays is also taken into account. Further on, the change of transition probabilities in radiative and non-radiative transitions by changing stage of ionization is discussed; and among them the leading part of Auger and Coster-Kronig transitions by the arearrangement of the atomic states is shown. The influence of non-radiative electronic transitions on ionization cross-sections for multiple ionization is discussed. Using these results, ionization cross-sections for direct and indirect processes for several ionization stages are given

  8. Electron impact ionization of heavy ions: some surprises

    International Nuclear Information System (INIS)

    Younger, S.M.

    1986-01-01

    This paper reports the results of calculations of electron impact ionization cross sections for a variety of heavy ions using a distorted wave Born-exchange approximation. The target is described by a Hartree-Fock wavefunction. The scattering matrix element is represented by a triple partial wave expansion over incident, scattered, and ejected (originally bound) continuum states. These partial waves are computed in the potentials associated with the initial target (incident and scattered waves) and the residual ion (ejected waves). A Gauss integration was performed over the distribution of energy between the two final state continuum electrons. For ionization of closed d- and f-subshells, the ejected f-waves were computed in frozen-core term-dependent Hartree-Fock potentials, which include the strong repulsive contribution in singlet terms which arises from the interaction of an excited orbital with an almost closed shell. Ground state correlation was included in some calculations of ionization of d 10 subshells

  9. Binary and Recoil Collisions in Strong Field Double Ionization of Helium

    International Nuclear Information System (INIS)

    Staudte, A.; Villeneuve, D. M.; Corkum, P. B.; Ruiz, C.; Becker, A.; Schoeffler, M.; Schoessler, S.; Meckel, M.; Doerner, R.; Zeidler, D.; Weber, Th.

    2007-01-01

    We have investigated the correlated momentum distribution of both electrons from nonsequential double ionization of helium in a 800 nm, 4.5x10 14 W/cm 2 laser field. Using very high resolution coincidence techniques, we find a so-far unobserved fingerlike structure in the correlated electron momentum distribution. The structure can be interpreted as a signature of the microscopic dynamics in the recollision process. We identify features corresponding to the binary and recoil lobe in field-free (e,2e) collisions. This interpretation is supported by analyzing ab initio solutions of a fully correlated three-dimensional helium model

  10. ASYMMETRIC MAGNETIC RECONNECTION IN WEAKLY IONIZED CHROMOSPHERIC PLASMAS

    International Nuclear Information System (INIS)

    Murphy, Nicholas A.; Lukin, Vyacheslav S.

    2015-01-01

    Realistic models of magnetic reconnection in the solar chromosphere must take into account that the plasma is partially ionized and that plasma conditions within any two magnetic flux bundles undergoing reconnection may not be the same. Asymmetric reconnection in the chromosphere may occur when newly emerged flux interacts with pre-existing, overlying flux. We present 2.5D simulations of asymmetric reconnection in weakly ionized, reacting plasmas where the magnetic field strengths, ion and neutral densities, and temperatures are different in each upstream region. The plasma and neutral components are evolved separately to allow non-equilibrium ionization. As in previous simulations of chromospheric reconnection, the current sheet thins to the scale of the neutral–ion mean free path and the ion and neutral outflows are strongly coupled. However, the ion and neutral inflows are asymmetrically decoupled. In cases with magnetic asymmetry, a net flow of neutrals through the current sheet from the weak-field (high-density) upstream region into the strong-field upstream region results from a neutral pressure gradient. Consequently, neutrals dragged along with the outflow are more likely to originate from the weak-field region. The Hall effect leads to the development of a characteristic quadrupole magnetic field modified by asymmetry, but the X-point geometry expected during Hall reconnection does not occur. All simulations show the development of plasmoids after an initial laminar phase

  11. Penning ionization cross sections of excited rare gas atoms

    International Nuclear Information System (INIS)

    Ukai, Masatoshi; Hatano, Yoshihiko.

    1988-01-01

    Electronic energy transfer processes involving excited rare gas atoms play one of the most important roles in ionized gas phenomena. Penning ionization is one of the well known electronic energy transfer processes and has been studied extensively both experimentally and theoretically. The present paper reports the deexcitation (Penning ionization) cross sections of metastable state helium He(2 3 S) and radiative He(2 1 P) atoms in collision with atoms and molecules, which have recently been obtained by the authors' group by using a pulse radiolysis method. Investigation is made of the selected deexcitation cross sections of He(2 3 S) by atoms and molecules in the thermal collisional energy region. Results indicate that the cross sections are strongly dependent on the target molecule. The deexcitation probability of He(2 3 S) per collision increases with the excess electronic energy of He(2 3 S) above the ionization potential of the target atom or molecule. Another investigation, made on the deexcitation of He(2 1 P), suggests that the deexcitation cross section for He(2 1 P) by Ar is determined mainly by the Penning ionization cross section due to a dipole-dipole interaction. Penning ionization due to the dipole-dipole interaction is also important for deexcitation of He(2 1 P) by the target molecules examined. (N.K.)

  12. Hyperthermal surface ionization mass spectrometry of organic molecules: monoterpenes

    International Nuclear Information System (INIS)

    Kishi, Hiroshi; Fujii, Toshihiro.

    1997-01-01

    This paper describes an experimental study on the influence of kinetic energy of fast monoterpene molecules on the surface ionization efficiency and on the mass spectral patterns, using rhenium oxide (ReO 2 ) surface. Molecular kinetic energy, given to the molecules through the acceleration in the seeded supersonic molecular beam, ranged from 1 to 10 eV. Hyperthermal surface ionization mass spectra (HSIMS) were taken for various incident kinetic energies and surface temperatures. The observed mass spectra were interpreted in a purely empirical way, by means of evidence from the previous investigations, and they were compared with conventional EI techniques and with the thermal energy surface ionization technique (SIOMS; Surface Ionization Organic Mass Spectrometry). Ionization efficiency (β) was also studied. Under hyperthermal surface ionization (HSI) conditions, many kinds of fragment ions, including quite abundant odd electron ions (OE +· ) are observed. HSIMS patterns of monoterpenes are different among 6-isomers, contrary to those of SIOMS and EIMS, where very similar patterns for isomers are observed. HSIMS patterns are strongly dependent on the molecular kinetic energies. The surface temperature does not affect much the spectral patterns, but it controls the total amount of ion formation. We conclude from these mass spectral findings, HSI-mechanism contains an impulsive process of ion formation, followed by the fragmentation process as a results of the internal energies acquired through the collision processes. (author)

  13. Generalized Bessel functions in tunnelling ionization

    International Nuclear Information System (INIS)

    Reiss, H R; Krainov, V P

    2003-01-01

    We develop two new approximations for the generalized Bessel function that frequently arises in the analytical treatment of strong-field processes, especially in non-perturbative multiphoton ionization theories. Both these new forms are applicable to the tunnelling environment in atomic ionization, and are analytically much simpler than the currently used low-frequency asymptotic approximation for the generalized Bessel function. The second of the new forms is an approximation to the first, and it is the second new form that exhibits the well-known tunnelling exponential

  14. In-Source Laser Resonance Ionization at ISOL Facilities

    CERN Document Server

    Marsh, Bruce; Feddosseev, Valentin

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

  15. Ionizing radiation

    International Nuclear Information System (INIS)

    Kruger, J.

    1989-01-01

    Ionizing radiation results in biological damage that differs from other hazardous substances and is highly dangerous to man. Ionizing radiation cannot be perceived by man's sense organs and the biological damage cannot be detected immediately afterwards (except in very high doses). Every human being is exposed to low doses of radiation. The structure of the atom; sources of ionizing radiation; radiation units; biological effects; norms for radiation protection; and the national control in South Africa are discussed. 1 fig., 5 refs

  16. THE NONLINEAR OHM'S LAW: PLASMA HEATING BY STRONG ELECTRIC FIELDS AND ITS EFFECTS ON THE IONIZATION BALANCE IN PROTOPLANETARY DISKS

    Energy Technology Data Exchange (ETDEWEB)

    Okuzumi, Satoshi [Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551 (Japan); Inutsuka, Shu-ichiro, E-mail: okuzumi@geo.titech.ac.jp [Department of Physics, Nagoya University, Nagoya, Aichi 464-8602 (Japan)

    2015-02-10

    The ionization state of the gas plays a key role in the magnetohydrodynamics (MHD) of protoplanetary disks. However, the ionization state can depend on the gas dynamics, because electric fields induced by MHD turbulence can heat up plasmas and thereby affect the ionization balance. To study this nonlinear feedback, we construct an ionization model that includes plasma heating by electric fields and impact ionization by heated electrons, as well as charging of dust grains. We show that when plasma sticking onto grains is the dominant recombination process, the electron abundance in the gas decreases with increasing electric field strength. This is a natural consequence of electron-grain collisions whose frequency increases with the electron's random velocity. The decreasing electron abundance may lead to a self-regulation of MHD turbulence. In some cases, not only the electron abundance but also the electric current decreases with increasing field strength in a certain field range. The resulting N-shaped current-field relation violates the fundamental assumption of the non-relativistic MHD that the electric field is uniquely determined by the current density. At even higher field strengths, impact ionization causes an abrupt increase of the electric current as expected by previous studies. We find that this discharge current is multi-valued (i.e., the current-field relation is S-shaped) under some circumstances, and that the intermediate branch is unstable. The N/S-shaped current-field relations may yield hysteresis in the evolution of MHD turbulence in some parts of protoplanetary disks.

  17. Current-voltage characteristic of parallel-plane ionization chamber with inhomogeneous ionization

    International Nuclear Information System (INIS)

    Stoyanov, D G

    2007-01-01

    The balances of particles and charges in the volume of parallel-plane ionization chamber are considered. Differential equations describing the distribution of current densities in the chamber volume are obtained. As a result of the differential equations solution an analytical form of the current-voltage characteristic of parallel-plane ionization chamber with inhomogeneous ionization in the volume is obtained

  18. Current-voltage characteristic of parallel-plane ionization chamber with inhomogeneous ionization

    Energy Technology Data Exchange (ETDEWEB)

    Stoyanov, D G [Faculty of Engineering and Pedagogy in Sliven, Technical University of Sofia, 59, Bourgasko Shaussee Blvd, 8800 Sliven (Bulgaria)

    2007-08-15

    The balances of particles and charges in the volume of parallel-plane ionization chamber are considered. Differential equations describing the distribution of current densities in the chamber volume are obtained. As a result of the differential equations solution an analytical form of the current-voltage characteristic of parallel-plane ionization chamber with inhomogeneous ionization in the volume is obtained.

  19. Explosives vapour identification in ion mobility spectrometry using a tunable laser ionization source: a comparison with conventional 63Ni ionization

    International Nuclear Information System (INIS)

    Clark, A.; Deas, R.M.; Kosmidis, C.; Ledingham, K.W.D.; Marshall, A.; Singhal, R.P.

    1995-01-01

    Laser multiphoton ionization (MPI) is used to produce ions from explosive vapours at atmospheric pressure in air for analysis by ion mobility spectrometry (IMS). In the positive ion mode of detection, NO + ions, generated directly by multiphoton dissociation/ionization of the explosive compounds, show strong variation with laser wavelength. This provides a means of identifying the presence of nitro-containing compounds. Moreover, electrons formed in the MPI of gaseous components in the air carrier stream, primarily O 2 , are transferred via neutral molecular oxygen (O 2 ) to trace explosive vapour, forming negative ions which give rise to characteristic and identifiable ion mobility spectra. Further, negative ion mobility spectra of several explosive vapours are presented using conventional 63 Ni ionization and are compared qualitatively with the laser ionization approach. (author)

  20. Sequential nonadiabatic excitation of large molecules and ions driven by strong laser fields

    International Nuclear Information System (INIS)

    Markevitch, Alexei N.; Levis, Robert J.; Romanov, Dmitri A.; Smith, Stanley M.; Schlegel, H. Bernhard; Ivanov, Misha Yu.

    2004-01-01

    Electronic processes leading to dissociative ionization of polyatomic molecules in strong laser fields are investigated experimentally, theoretically, and numerically. Using time-of-flight ion mass spectroscopy, we study the dependence of fragmentation on laser intensity for a series of related molecules and report regular trends in this dependence on the size, symmetry, and electronic structure of a molecule. Based on these data, we develop a model of dissociative ionization of polyatomic molecules in intense laser fields. The model is built on three elements: (i) nonadiabatic population transfer from the ground electronic state to the excited-state manifold via a doorway (charge-transfer) transition; (ii) exponential enhancement of this transition by collective dynamic polarization of all electrons, and (iii) sequential energy deposition in both neutral molecules and resulting molecular ions. The sequential nonadiabatic excitation is accelerated by a counterintuitive increase of a large molecule's polarizability following its ionization. The generic theory of sequential nonadiabatic excitation forms a basis for quantitative description of various nonlinear processes in polyatomic molecules and ions in strong laser fields

  1. Ionization of nitrogen cluster beam

    International Nuclear Information System (INIS)

    Yano, Katsuki; Be, S.H.; Enjoji, Hiroshi; Okamoto, Kosuke

    1975-01-01

    A nitrogen cluster beam (neutral particle intensity of 28.6 mAsub(eq)) is ionized by electron collisions in a Bayard-Alpert gauge type ionizer. The extraction efficiency of about 65% is obtained at an electron current of 10 mA with an energy of 50 eV. The mean cluster size produced at a pressure of 663 Torr and temperature of 77.3 K is 2x10 5 molecules per cluster. By the Coulomb repulsion force, multiply ionized cluster ions are broken up into smaller fragments and the cluster ion size reduces to one-fourth at an electron current of 15 mA. Mean neutral cluster sizes depend strongly on the initial degree of saturation PHI 0 and are 2x10 5 , 7x10 4 and 3x10 4 molecules per cluster at PHI 0 's of 0.87, 0.66 and 0.39, respectively. (auth.)

  2. Chemical changes in food packaging resulting from ionizing irradiation

    International Nuclear Information System (INIS)

    Thayer, D.W.

    1988-01-01

    Recent approvals of food irradiation processes by the U.S. Food and Drug Administration have led to a search for packaging approved for use with ionizing radiation. Though 13 packaging materials were approved several years ago as food contactants for gamma irradiation up to 10 kGy at refrigeration temperatures and 4 packaging materials were approved for up to 60 kGy at cryogenic temperatures, no currently used packaging is approved for irradiated foods. Extensive research was conducted by the U.S. Army and others on the suitability of both flexible packaging and metal cans for packaging irradiated foods. The results of the studies of packaging for irradiated foods will be described and discussed in context of currently used packaging materials for non-irradiated meats and poultry

  3. Heating and ionization in MHD shock waves propagating into partially ionized plasma

    International Nuclear Information System (INIS)

    Bighel, L.; Collins, A.R.; Cramer, N.F.; Watson-Munro, C.N.

    1975-09-01

    A model of the structure of MHD switch-on shocks propagating in a partially ionized plasma, in which the primary dissipation mechanism is friction between ions and neutrals, is here compared favourably with experimental results. Four degrees of upstream ionization were studied, ranging from almost complete to very small ionization. (author)

  4. Heating and ionization in MHD shock wave propagating into partially ionized plasma

    International Nuclear Information System (INIS)

    Bighel, L.; Collins, A.R.; Cramer, N.F.; Watson-Munro, C.N.

    1975-09-01

    A model of the structure of MHD switch-on shocks propagating in a partially ionized plasma, in which the primary dissipation mechanism is friction between ions and neutrals, is here compared favourably with experimental results. Four degrees of upstream ionization were studied, ranging from almost complete to very small ionization. (author)

  5. Nonadiabatic theory of strong-field atomic effects under elliptical polarization

    International Nuclear Information System (INIS)

    Wang Xu; Eberly, J. H.

    2012-01-01

    Elliptically polarized laser fields provide a new channel for access to strong-field processes that are either suppressed or not present under linear polarization. Quantum theory is mostly unavailable for their analysis, and we report here results of a systematic study based on a classical ensemble theory with solution of the relevant ab inito time-dependent Newton equations for selected model atoms. The study's approach is necessarily nonadiabatic, as it follows individual electron trajectories leading to single, double, and triple ionizations. Of particular interest are new results bearing on open questions concerning experimental reports of unexplained species dependences as well as double-electron release times that are badly matched by a conventional adiabatic quantum tunneling theory. We also report the first analysis of electron trajectories for sequential and non-sequential triple ionization.

  6. First ionization potential of the heaviest actinide lawrencium, element 103

    Directory of Open Access Journals (Sweden)

    Sato Tetsuya K.

    2016-01-01

    Full Text Available The first ionization potential (IP1 of element 103, lawrencium (Lr, has been successfully determined for the first time by using a newly developed method based on a surface ionization process. The measured IP1 value is 4.9630.080.07 eV. This value is the smallest among those of actinide elements and is in excellent agreement with the value of 4.963(15 eV predicted by state-of-the-art relativistic calculations also performed in this work. Our results strongly support that the Lr atom has an electronic configuration of [Rn]7s25f147p11/2, which is influenced by strong relativistic effects. The present work provides a reliable benchmark for theoretical calculations and also opens the way for studies on atomic properties of heavy elements with atomic number Z > 100. Moreover, the present achievement has triggered a controversy on the position of lutetium (Lu and Lr in the Periodic Table of Elements.

  7. Coherent combs in ionization by intense and short laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Krajewska, K., E-mail: Katarzyna.Krajewska@fuw.edu.pl [Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warszawa (Poland); Department of Physics and Astronomy, University of Nebraska, Lincoln, NE 68588-0299 (United States); Kamiński, J.Z., E-mail: Jerzy.Kaminski@fuw.edu.pl [Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warszawa (Poland)

    2016-03-22

    Photoionization of positive ions by a train of intense, short laser pulses is investigated within the relativistic strong field approximation, using the velocity gauge. The formation of broad peak structures in the high-energy domain of photoelectrons is observed and interpreted. The emergence of coherent photoelectron energy combs within these structures is demonstrated, and it is interpreted as the consequence of the Fraunhofer-type interference/diffraction of probability amplitudes of ionization from individual pulses comprising the train. Extensions to the coherent angular combs are also studied, and effects related to the radiation pressure are presented. - Highlights: • We develop relativistic Strong-Field Approximation for ionization by intense and short laser pulses of arbitrary spectral compositions. • We show that the consistent interpretation of results is provided by the Keldysh-type saddle point analysis of probability amplitudes. • We derive a general Fraunhofer-type interference/diffraction formula for finite train of pulses. • We study the coherent combs in photoelectron probability distributions.

  8. Bond rearrangement caused by sudden single and multiple ionization of water molecules

    International Nuclear Information System (INIS)

    Ben-Itzhak, I.; Sayler, A. Max; Leonard, M.; Maseberg, J.W.; Hathiramani, D.; Wells, E.; Smith, M.A.; Xia, Jiangfan; Wang, Pengqian; Carnes, K.D.; Esry, B.D.

    2005-01-01

    Bond rearrangement, namely the dissociation of water into H 2 + +O q+ following ionization by fast proton and highly charged ion impact, was investigated. Single ionization by fast proton impact exhibits a strong isotopic effect, the dissociation of H 2 O + ->H 2 + +O being about twice as likely as D 2 O + ->D 2 + +O, with HDO + ->HD + +O in between. This suggests that the bond rearrangement does not happen during the slow dissociation, but rather during the very fast ionization, and thus H 2 + should also be produced when the water molecule is multiply ionized. We observed that the H 2 + +O + and H 2 + +O 2+ production in 1MeV/amu F 7+ +H 2 O collisions are 0.209+/-0.006% and 0.0665+/-0.003%, respectively, of the main double-ionization dissociation product, H 2 O 2+ ->H + +OH + . This ratio is similar to the triple to double ionization ratio in similar collisions with atomic targets thus suggesting that the bond-rearrangement fraction out of each ionization level is approximately constant. Similar dissociation channels in the heavier water isotopes, which are expected to be smaller, are under study. Finally, the fragmentation of HDO exhibits very strong isotopic preference for breaking the OH bond over the OD bond

  9. Resonances above the ionization threshold in positron-hydrogen scattering

    International Nuclear Information System (INIS)

    Kernoghan, A.A.; Walters, H.R.J.; McAlinden, M.T.

    1994-01-01

    Resonances appearing above the ionization threshold in coupled-state calculations of positron-atom scattering are discussed. Calculations in the six state approximation Ps(1s, 2s, 2p) + H(1s, 2s, 2p), which show such resonance structure, are compared with a more extensive 18-state approximation Ps(1s, 2s, 3s, 4s, 2p, 3p, 4p, 3d, 4d) + H(1s, 2s, 3s, 4s, 2p, 3p, 4p, 3d, 4d) in which channels other than 1s, 2s and 2p are represented by pseudostates. The results strongly indicate that the above ionization threshold resonances observed in the six-state approximation, and in other small basis set calculations, are not real. It is suggested that they are a consequence of the neglect, or inadequate representation in other approximations, of ionization channels. In the six-state approximation the positronium component of the system wavefunction attempts to represent the missing ionization channels but in so doing produces unreal resonances above the ionization threshold. More generally it is suggested that, in coupled-state calculations of positron-atom scattering, the atom part of the system wavefunction will try to compensate for defects in the positronium component and vice versa. When the defects are serious, for example, the omission of important ionization channels, unusual spurious behaviour is to be expected. (Author)

  10. Theory of steady-state plane tunneling-assisted impact ionization waves

    International Nuclear Information System (INIS)

    Kyuregyan, A. S.

    2013-01-01

    The effect of band-to-band and trap-assisted tunneling on the properties of steady-state plane ionization waves in p + -n-n + structures is theoretically analyzed. It is shown that such tunneling-assisted impact ionization waves do not differ in a qualitative sense from ordinary impact ionization waves propagating due to the avalanche multiplication of uniformly distributed seed electrons and holes. The quantitative differences of tunneling-assisted impact ionization waves from impact ionization waves are reduced to a slightly different relation between the wave velocity u and the maximum field strength E M at the front. It is shown that disregarding impact ionization does not exclude the possibility of the existence of tunneling-assisted ionization waves; however, their structure radically changes, and their velocity strongly decreases for the same E M . A comparison of the dependences u(E M ) for various ionization-wave types makes it possible to determine the conditions under which one of them is dominant. In conclusion, unresolved problems concerning the theory of tunneling-assisted impact ionization waves are discussed and the directions of further studies are outlined

  11. Ionization Efficiency in the Dayside Martian Upper Atmosphere

    Science.gov (United States)

    Cui, J.; Wu, X.-S.; Xu, S.-S.; Wang, X.-D.; Wellbrock, A.; Nordheim, T. A.; Cao, Y.-T.; Wang, W.-R.; Sun, W.-Q.; Wu, S.-Q.; Wei, Y.

    2018-04-01

    Combining the Mars Atmosphere and Volatile Evolution measurements of neutral atmospheric density, solar EUV/X-ray flux, and differential photoelectron intensity made during 240 nominal orbits, we calculate the ionization efficiency, defined as the ratio of the secondary (photoelectron impact) ionization rate to the primary (photon impact) ionization rate, in the dayside Martian upper atmosphere under a range of solar illumination conditions. Both the CO2 and O ionization efficiencies tend to be constant from 160 km up to 250 km, with respective median values of 0.19 ± 0.03 and 0.27 ± 0.04. These values are useful for fast calculation of the ionization rate in the dayside Martian upper atmosphere, without the need to construct photoelectron transport models. No substantial diurnal and solar cycle variations can be identified, except for a marginal trend of reduced ionization efficiency approaching the terminator. These observations are favorably interpreted by a simple scenario with ionization efficiencies, as a first approximation, determined by a comparison between relevant cross sections. Our analysis further reveals a connection between regions with strong crustal magnetic fields and regions with high ionization efficiencies, which are likely indicative of more efficient vertical transport of photoelectrons near magnetic anomalies.

  12. Ionizing potential waves and high-voltage breakdown streamers.

    Science.gov (United States)

    Albright, N. W.; Tidman, D. A.

    1972-01-01

    The structure of ionizing potential waves driven by a strong electric field in a dense gas is discussed. Negative breakdown waves are found to propagate with a velocity proportional to the electric field normal to the wavefront. This causes a curved ionizing potential wavefront to focus down into a filamentary structure, and may provide the reason why breakdown in dense gases propagates in the form of a narrow leader streamer instead of a broad wavefront.

  13. Pressure of a partially ionized hydrogen gas : numerical results from exact low temperature expansions

    OpenAIRE

    Alastuey , Angel; Ballenegger , Vincent

    2010-01-01

    8 pages; International audience; We consider a partially ionized hydrogen gas at low densities, where it reduces almost to an ideal mixture made with hydrogen atoms in their ground-state, ionized protons and ionized electrons. By performing systematic low-temperature expansions within the physical picture, in which the system is described as a quantum electron-proton plasma interacting via the Coulomb potential, exact formulae for the first five leading corrections to the ideal Saha equation ...

  14. Ionizing radiations

    International Nuclear Information System (INIS)

    Anon.

    1999-01-01

    This is an update about the radiological monitoring in base nuclear installations. A departmental order of the 23. march 1999 (J.O.28. april, p.6309) determines the enabling rules by the Office of Protection against Ionizing Radiations of person having at one's disposal the results with names of individual exposure of workers put through ionizing radiations. (N.C.)

  15. MAGNETOACOUSTIC WAVES IN A PARTIALLY IONIZED TWO-FLUID PLASMA

    Energy Technology Data Exchange (ETDEWEB)

    Soler, Roberto; Ballester, Jose Luis [Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain); Carbonell, Marc, E-mail: roberto.soler@uib.es, E-mail: joseluis.ballester@uib.es, E-mail: marc.carbonell@uib.es [Departament de Matemàtiques i Informàtica, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)

    2013-11-01

    Compressible disturbances propagate in a plasma in the form of magnetoacoustic waves driven by both gas pressure and magnetic forces. In partially ionized plasmas the dynamics of ionized and neutral species are coupled due to ion-neutral collisions. As a consequence, magnetoacoustic waves propagating through a partially ionized medium are affected by ion-neutral coupling. The degree to which the behavior of the classic waves is modified depends on the physical properties of the various species and on the relative value of the wave frequency compared to the ion-neutral collision frequency. Here, we perform a comprehensive theoretical investigation of magnetoacoustic wave propagation in a partially ionized plasma using the two-fluid formalism. We consider an extensive range of values for the collision frequency, ionization ratio, and plasma β, so that the results are applicable to a wide variety of astrophysical plasmas. We determine the modification of the wave frequencies and study the frictional damping due to ion-neutral collisions. Approximate analytic expressions for the frequencies are given in the limit case of strongly coupled ions and neutrals, while numerically obtained dispersion diagrams are provided for arbitrary collision frequencies. In addition, we discuss the presence of cutoffs in the dispersion diagrams that constrain wave propagation for certain combinations of parameters. A specific application to propagation of compressible waves in the solar chromosphere is given.

  16. MAGNETOACOUSTIC WAVES IN A PARTIALLY IONIZED TWO-FLUID PLASMA

    International Nuclear Information System (INIS)

    Soler, Roberto; Ballester, Jose Luis; Carbonell, Marc

    2013-01-01

    Compressible disturbances propagate in a plasma in the form of magnetoacoustic waves driven by both gas pressure and magnetic forces. In partially ionized plasmas the dynamics of ionized and neutral species are coupled due to ion-neutral collisions. As a consequence, magnetoacoustic waves propagating through a partially ionized medium are affected by ion-neutral coupling. The degree to which the behavior of the classic waves is modified depends on the physical properties of the various species and on the relative value of the wave frequency compared to the ion-neutral collision frequency. Here, we perform a comprehensive theoretical investigation of magnetoacoustic wave propagation in a partially ionized plasma using the two-fluid formalism. We consider an extensive range of values for the collision frequency, ionization ratio, and plasma β, so that the results are applicable to a wide variety of astrophysical plasmas. We determine the modification of the wave frequencies and study the frictional damping due to ion-neutral collisions. Approximate analytic expressions for the frequencies are given in the limit case of strongly coupled ions and neutrals, while numerically obtained dispersion diagrams are provided for arbitrary collision frequencies. In addition, we discuss the presence of cutoffs in the dispersion diagrams that constrain wave propagation for certain combinations of parameters. A specific application to propagation of compressible waves in the solar chromosphere is given

  17. Measurements of ion velocity separation and ionization in multi-species plasma shocks

    Science.gov (United States)

    Rinderknecht, Hans G.; Park, H.-S.; Ross, J. S.; Amendt, P. A.; Wilks, S. C.; Katz, J.; Hoffman, N. M.; Kagan, G.; Vold, E. L.; Keenan, B. D.; Simakov, A. N.; Chacón, L.

    2018-05-01

    The ion velocity structure of a strong collisional shock front in a plasma with multiple ion species is directly probed in laser-driven shock-tube experiments. Thomson scattering of a 263.25 nm probe beam is used to diagnose ion composition, temperature, and flow velocity in strong shocks ( M ˜6 ) propagating through low-density ( ρ˜0.1 mg/cc) plasmas composed of mixtures of hydrogen (98%) and neon (2%). Within the preheat region of the shock front, two velocity populations of ions are observed, a characteristic feature of strong plasma shocks. The ionization state of the Ne is observed to change within the shock front, demonstrating an ionization-timescale effect on the shock front structure. The forward-streaming proton feature is shown to be unexpectedly cool compared to predictions from ion Fokker-Planck simulations; the neon ionization gradient is evaluated as a possible cause.

  18. Dark Matter Detection Using Helium Evaporation and Field Ionization.

    Science.gov (United States)

    Maris, Humphrey J; Seidel, George M; Stein, Derek

    2017-11-03

    We describe a method for dark matter detection based on the evaporation of helium atoms from a cold surface and their subsequent detection using field ionization. When a dark matter particle scatters off a nucleus of the target material, elementary excitations (phonons or rotons) are produced. Excitations which have an energy greater than the binding energy of helium to the surface can result in the evaporation of helium atoms. We propose to detect these atoms by ionizing them in a strong electric field. Because the binding energy of helium to surfaces can be below 1 meV, this detection scheme opens up new possibilities for the detection of dark matter particles in a mass range down to 1  MeV/c^{2}.

  19. Dark Matter Detection Using Helium Evaporation and Field Ionization

    Science.gov (United States)

    Maris, Humphrey J.; Seidel, George M.; Stein, Derek

    2017-11-01

    We describe a method for dark matter detection based on the evaporation of helium atoms from a cold surface and their subsequent detection using field ionization. When a dark matter particle scatters off a nucleus of the target material, elementary excitations (phonons or rotons) are produced. Excitations which have an energy greater than the binding energy of helium to the surface can result in the evaporation of helium atoms. We propose to detect these atoms by ionizing them in a strong electric field. Because the binding energy of helium to surfaces can be below 1 meV, this detection scheme opens up new possibilities for the detection of dark matter particles in a mass range down to 1 MeV /c2 .

  20. IONIZATION IN ATMOSPHERES OF BROWN DWARFS AND EXTRASOLAR PLANETS. V. ALFVÉN IONIZATION

    International Nuclear Information System (INIS)

    Stark, C. R.; Helling, Ch.; Rimmer, P. B.; Diver, D. A.

    2013-01-01

    Observations of continuous radio and sporadic X-ray emission from low-mass objects suggest they harbor localized plasmas in their atmospheric environments. For low-mass objects, the degree of thermal ionization is insufficient to qualify the ionized component as a plasma, posing the question: what ionization processes can efficiently produce the required plasma that is the source of the radiation? We propose Alfvén ionization as a mechanism for producing localized pockets of ionized gas in the atmosphere, having sufficient degrees of ionization (≥10 –7 ) that they constitute plasmas. We outline the criteria required for Alfvén ionization and demonstrate its applicability in the atmospheres of low-mass objects such as giant gas planets, brown dwarfs, and M dwarfs with both solar and sub-solar metallicities. We find that Alfvén ionization is most efficient at mid to low atmospheric pressures where a seed plasma is easier to magnetize and the pressure gradients needed to drive the required neutral flows are the smallest. For the model atmospheres considered, our results show that degrees of ionization of 10 –6 -1 can be obtained as a result of Alfvén ionization. Observable consequences include continuum bremsstrahlung emission, superimposed with spectral lines from the plasma ion species (e.g., He, Mg, H 2 , or CO lines). Forbidden lines are also expected from the metastable population. The presence of an atmospheric plasma opens the door to a multitude of plasma and chemical processes not yet considered in current atmospheric models. The occurrence of Alfvén ionization may also be applicable to other astrophysical environments such as protoplanetary disks

  1. Long-term effects to ionizing radiation in crustacean Daphnia magna

    International Nuclear Information System (INIS)

    Sarapul'tseva, E.I.

    2016-01-01

    The results of this study have provided strong evidence for the trans generational effects of parental exposure to ionizing radiation in crustacean Daphnia magna. To establish whether parental irradiation can affect the survival, life span and fertility of directly exposed organisms and their non-exposed offspring, D. magna were given 10, 100, 1000 and 10,000 mGy of acute γ-rays. MTT-assay was first applied for the investigation in vivo of the mechanisms of trans generational low doses effects of radiation and development of stress in Daphnia. Our dates strongly support MTT assay results as a good bio marker of survival and fertility effects at D. magna. (authors)

  2. Ionization of molecular hydrogen in ultrashort intense laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Vanne, Yulian V.

    2010-03-18

    A novel ab initio numerical approach is developed and applied that solves the time-dependent Schroedinger equation describing two-electron diatomic molecules (e.g. molecular hydrogen) exposed to an intense ultrashort laser pulse. The method is based on the fixed-nuclei and the non-relativistic dipole approximations and aims to accurately describe both correlated electrons in full dimensionality. The method is applicable for a wide range of the laser pulse parameters and is able to describe both few-photon and many-photon single ionization processes, also in a non-perturbative regime. A key advantage of the method is its ability to treat the strong-field response of the molecules with arbitrary orientation of the molecular axis with respect to the linear-polarized laser field. Thus, this work reports on the first successful orientation-dependent analysis of the multiphoton ionization of H{sub 2} performed by means of a full-dimensional numerical treatment. Besides the investigation of few-photon regime, an extensive numerical study of the ionization by ultrashort frequency-doubled Ti:sapphire laser pulses (400 nm) is presented. Performing a series of calculations for different internuclear separations, the total ionization yields of H{sub 2} and D{sub 2} in their ground vibrational states are obtained for both parallel and perpendicular orientations. A series of calculations for 800 nm laser pulses are used to test a popular simple interference model. Besides the discussion of the ab initio numerical method, this work considers different aspects related to the application of the strong-field approximation (SFA) for investigation of a strong-field response of an atomic and molecular system. Thus, a deep analysis of the gauge problem of SFA is performed and the quasistatic limit of the velocity-gauge SFA ionization rates is derived. The applications of the length-gauge SFA are examined and a recently proposed generalized Keldysh theory is criticized. (orig.)

  3. Ionization of molecular hydrogen in ultrashort intense laser pulses

    International Nuclear Information System (INIS)

    Vanne, Yulian V.

    2010-01-01

    A novel ab initio numerical approach is developed and applied that solves the time-dependent Schroedinger equation describing two-electron diatomic molecules (e.g. molecular hydrogen) exposed to an intense ultrashort laser pulse. The method is based on the fixed-nuclei and the non-relativistic dipole approximations and aims to accurately describe both correlated electrons in full dimensionality. The method is applicable for a wide range of the laser pulse parameters and is able to describe both few-photon and many-photon single ionization processes, also in a non-perturbative regime. A key advantage of the method is its ability to treat the strong-field response of the molecules with arbitrary orientation of the molecular axis with respect to the linear-polarized laser field. Thus, this work reports on the first successful orientation-dependent analysis of the multiphoton ionization of H 2 performed by means of a full-dimensional numerical treatment. Besides the investigation of few-photon regime, an extensive numerical study of the ionization by ultrashort frequency-doubled Ti:sapphire laser pulses (400 nm) is presented. Performing a series of calculations for different internuclear separations, the total ionization yields of H 2 and D 2 in their ground vibrational states are obtained for both parallel and perpendicular orientations. A series of calculations for 800 nm laser pulses are used to test a popular simple interference model. Besides the discussion of the ab initio numerical method, this work considers different aspects related to the application of the strong-field approximation (SFA) for investigation of a strong-field response of an atomic and molecular system. Thus, a deep analysis of the gauge problem of SFA is performed and the quasistatic limit of the velocity-gauge SFA ionization rates is derived. The applications of the length-gauge SFA are examined and a recently proposed generalized Keldysh theory is criticized. (orig.)

  4. Effects of previous ionization and excitation on the ionization wave propagation along the dielectric tube

    International Nuclear Information System (INIS)

    Xia, Yang; Liu, Dongping; Bi, Zhenhua; Wang, Xueyang; Niu, Jinhai; Ji, Longfei; Song, Ying; Qi, Zhihua; Wang, Wenchun

    2016-01-01

    In this paper, by using a high precision synchronization system, the ignition time, velocity, and propagation properties of the ionization waves (IWs) have been investigated in detail from the 1st high voltage (HV) pulse to the sequential ones over a large range of the pulse-off time. In order to clarify the effects of previous ionization and excitation on the IW propagation, the density of the residual charges are controlled by varying the pulse-off time from 199 μs to 15 μs. The results show that the formation and propagation of IWs can be strongly affected by previous discharge. For a longer pulse-off time (100 μs–190 μs), the propagation velocity of plasma bullets are decreased from the 1st to the 10th HV pulse, then increased after the 10th pulse, and finally become stable after about 500 pulses. When the pulse-off time is reduced to 15 μs, the propagation velocity of plasma bullets will rapidly increase and become stable after the 1st HV pulse. The ignition voltage is significantly reduced after the 1st HV pulse with the decrease in pulse-off time. Consequently, the generation and propagation of IWs in the tube are strongly affected by the accumulation of long-lived metastable helium (He) species and residual charges from previous discharges, which is important for understanding the plasma bullet behavior. (paper)

  5. Heating of the solar chromosphere by ionization pumping

    Science.gov (United States)

    Lindsey, C. A.

    1981-01-01

    A new theory is proposed to explain the heating of the solar chromosphere, and possibly the corona, by the dissipation of hydrodynamic compression waves. The basis of the dissipative mechanism, here referred to as ionization pumping, is hysteresis caused by irreversible relaxation of the chromospheric medium to ionization equilibrium following pressure perturbations. In the middle chromosphere, where hydrogen is partially ionized, it is shown that ionization pumping will cause strong dissipation of waves whose periods are 200s or less. This could cause heating of the chromosphere sufficient to compensate for the radiative losses. The mechanism retains a high efficiency for waves of arbitrarily small amplitude and, thus, can be more efficient than shock dissipation for small perturbations in pressure. The formation of shocks therefore is not required for the dissipation of waves whose periods are several minutes or less.

  6. Heating of the solar chromosphere by ionization pumping

    International Nuclear Information System (INIS)

    Lindsey, C.A.

    1981-01-01

    A new theory is proposed to explain the heating of the solar chromosphere, and possibly the corona, by the dissipation of hydrodynamic compression waves. The basis of the disspative mechanism, here referred to as ''ionization pumping,'' is hysteresis caused by irresversible relaxation of the chromospheric medium to ionization equilibrium following pressure perturbations. In the middle chromosphere, where hydrogen is partially ionized, it is shown that ionization pumping will cause strong dissipation of waves whose periods are approx.200 s or less. This could cause heating of the chromosphere sufficient to compensate for the radiative losses. The mechanism retains a high efficiency for waves of arbitrarily small amplitude and, thus, can be more efficient than shock dissipation for small perturbations in pressure. The formation of shocks therefore is not required for the dissipation of waves whose periods are several minutes or less

  7. Ionization of atoms by high energy photons

    International Nuclear Information System (INIS)

    Amusia, M.Y.; Ioffe, A.F.

    1994-01-01

    Photoionization of atoms by high energy photons is considered. It is emphasized that in this frequency region the cross section and other characteristics of the process are strongly effected by electron shell polarization and rearrangement effects, including that due to inner vacancy Auger decay. In the effects of nuclear structure could be important and noticeable, i.e. of virtual or real excitation of the nucleus degrees of freedom and of the Quantum Electrodynamics vacuum. Ionization accompanied by secondary photon emission (Compton ionization) is analyzed in the considered domain of energies

  8. Monte Carlo Wave Packet Theory of Dissociative Double Ionization

    DEFF Research Database (Denmark)

    Leth, Henriette Astrup; Madsen, Lars Bojer; Mølmer, Klaus

    2009-01-01

    Nuclear dynamics in strong-field double ionization processes is predicted using a stochastic Monte Carlo wave packet technique. Using input from electronic structure calculations and strong-field electron dynamics the description allows for field-dressed dynamics within a given molecule as well...

  9. Ionization mechanisms in capillary supercritical fluid chromatography-chemical ionization mass spectrometry

    NARCIS (Netherlands)

    Houben, R.J.; Leclercq, P.A.; Cramers, C.A.M.G.

    1991-01-01

    Ionization mechanisms have been studied for supercritical fluid chromatography (SFC) with mass spectrometric (MS) detection. One of the problems associated with SFC-MS is the interference of mobile phase constituents in the ionization process, which complicates the interpretation of the resulting

  10. Electromagnetic modes in cold magnetized strongly coupled plasmas

    OpenAIRE

    Tkachenko, I. M.; Ortner, J.; Rylyuk, V. M.

    1999-01-01

    The spectrum of electromagnetic waves propagating in a strongly coupled magnetized fully ionized hydrogen plasma is found. The ion motion and damping being neglected, the influence of the Coulomb coupling on the electromagnetic spectrum is analyzed.

  11. Comparison of Electrospray Ionization and Atmospheric Chemical Ionization Coupled with the Liquid Chromatography-Tandem Mass Spectrometry for the Analysis of Cholesteryl Esters

    Directory of Open Access Journals (Sweden)

    Hae-Rim Lee

    2015-01-01

    Full Text Available The approach of two different ionization techniques including electrospray ionization (ESI and atmospheric pressure chemical ionization (APCI coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS was tested for the analysis of cholesteryl esters (CEs. The retention time (RT, signal intensity, protonated ion, and product ion of CEs were compared between ESI and APCI. RT of CEs from both ionizations decreased with increasing double bonds, while it increased with longer carbon chain length. The ESI process generated strong signal intensity of precursor ions corresponding to [M+Na]+ and [M+NH4]+ regardless of the number of carbon chains and double bonds in CEs. On the other hand, the APCI process produced a protonated ion of CEs [M+H]+ with a weak signal intensity, and it is selectively sensitive to detect precursor ions of CEs with unsaturated fatty acids. The ESI technique proved to be effective in ionizing more kinds of CEs than the APCI technique.

  12. Chemical data on ionizing and non-ionizing angiographic contrast materials

    International Nuclear Information System (INIS)

    Bonati, F.

    1980-01-01

    The cardiovascular effects of ionizing and non-ionizing contrast media are compared in experimental animals and in isolated heart preparations. The following parameters were recorded: peripheric arterial diastolic pressure, heart rate, duration of asystolic period, respiratory rate, contractility of the myocardium (dp/dt, LVSP, Vsub(max), EDV, ESV, SV). The observed changes are mainly due to the higher osmotic activity of the contrast media, as similar alterations were recorded after the injection of hyperosmotic glucose solution. It is concluded that administration of non-ionizing contrast media results in significantly less cardiovascular side effects. (L.E.)

  13. Characteristics of a Dry Fog Ionizer

    International Nuclear Information System (INIS)

    Murata, Y; Kudo, Y; Yonezawa, M

    2008-01-01

    The newly developed 'Dry Fog Ionizer' generates charged dry fog. The dry fog consists of very fine water droplets 8μm in mean diameter. This system consists of a dry fog nozzle (H.Ikeuchi and Co., LTD.), a ring electrode for induction charging (50mm outside diameter, and 10mm thick) in front of the nozzle, and a fan for dissipating charged dry fog. The ring electrode is DC or AC-biased and fine droplets ejected from the nozzle are electrified by induction charging. The particle size of the charged water droplets are reduced through evaporation during the transporting process by air flow, and completely evaporate approximately 2m from the nozzle under normal atmospheric conditions (25 deg. C, 60%R.H.) leaving high density ions. Using this system, high density ionic space charge can be realized in a remote spot from the ionizer. By this principle, the Dry Fog Ionizer shows strong charge-eliminating ability in the region away from the ionizer. When a dc bias of 5kV was applied to a ring electrode with the rate of water flow from the nozzle being 21/h, an ionic space-charge density of 1200nC /m 3 was able to be obtained at a distance 2m away from the ionizer, which was 10 2 times the value produced by an ordinary corona-type ionizer with an air blower.

  14. Multiphoton above threshold effects in strong-field fragmentation

    DEFF Research Database (Denmark)

    B Madsen, C; Anis, F; B Madsen, L

    2012-01-01

    We present a study of multiphoton dissociative ionization from molecules. By solving the time-dependent Schrödinger equation for H2+ and projecting the solution onto double continuum scattering states, we observe the correlated electron-nuclear ionization dynamics in detail. We show—for the first...... time—how multiphoton structure prevails as long as one accounts for the energies of all the fragments. Our current work provides a new avenue to analyze strong-field fragmentation that leads to a deeper understanding of the correlated molecular dynamics....

  15. The role of multiple ionization and subshell coupling effects in L-shell ionization of Au by oxygen ions

    International Nuclear Information System (INIS)

    Banas, D.; Braziewicz, J.; Pajek, M.; Semaniak, J.; Czyzewski, T.; Fijal, I.; Jaskola, M.; Kretschmer, W.; Mukoyama, T.; Trautmann, D.

    2002-01-01

    The ionization of L-subshell electrons in gold by the impact of 0.4-2.2 MeV amu -1 O ions was studied by observing excited Lγ(L-N, O) x-rays. We demonstrate that both the multiple ionization in outer M- and N-shells as well as the coupling effects in the L-shell play an important role in understanding the measured L-subshell ionization cross sections. The multiple ionization was found to be important in two aspects: first, the analysis of x-ray energy shifts and line broadening was crucial for proper interpretation of measured x-ray spectra; second, the additional vacancies in the M- and N-shells substantially influenced the L 1 -subshell fluorescence and Coster-Kronig (CK) yields, mainly by closing strong L 1 -L 3 M 4,5 CK transitions. The data are compared with the simplified coupled-channels calculations using the 'coupled-subshell model' (CSM) based on the semiclassical approximation (SCA), which describes both direct Coulomb ionization as well as the L-subshell couplings within the same theoretical approach. A good agreement of the present data with the theoretical predictions based on the discussed SCA-CSM approach is observed. Present findings partly explain the long-standing problem of inadequate theoretical description of L-shell ionization by heavy ion impact. (author)

  16. Atomic and Free Electrons in a Strong Light Field

    International Nuclear Information System (INIS)

    Fedorov, Mikhail V.

    1998-02-01

    This book presents and describes a series of unusual and striking strong-field phenomena concerning atoms and free electrons. Some of these phenomena are: multiphoton stimulated Bremsstrahlung, free-electron lasers, ave-packet physics, above-threshold ionization, and strong-field stabilization in Rydberg atoms. The theoretical foundations and causes of the phenomena are described in detail, with all the approximations and derivations discussed. All the known and relevant experiments are described oo, and their results are compared with those of the existing theoretical models. An extensive general theoretical introduction gives a good basis for subsequent parts of the book and is an independent and self-sufficient description of the most efficient theoretical methods of the strong-field and multiphoton physics. This book can serve as a textbook for graduate students

  17. Homozygous mutations in the Fhit gene results in resistance to ionizing radiation and inhibition of apoptosis

    International Nuclear Information System (INIS)

    Turner, B.C.; Potoczek, M.B.; Ottey, M.; Croce, C.M.; Huebner, K.

    2001-01-01

    Purpose: The Fhit gene was identified because it represents the most active constitutive chromosome fragile site and has functions often associated with a tumor suppressor gene. Mutations in the Fhit locus have been identified in many cancer-derived cell lines, primary human tumors including lung, head and neck, colon, breast, and esophagus, and are associated with tobacco-induced lung cancers. In this study, we examined the cellular response of mouse epithelial cells with complete loss of Fhit to therapeutic doses of ionizing radiation and the prognostic importance of Fhit protein in early stage breast cancer patients treated with breast conserving therapy. Materials and Methods: Mouse epithelial cell lines containing either homozygous mutant Fhit -/- or wild-type Fhit +/+ were derived from mice (C57BL/6J X 129/SvJ) with either wild-type or inactivated Fhit gene. Clonogenic cell survival assays were carried out on subconfluent cells in logarithmic growth using a 137 Cs irradiator and survival curves were plotted as the log of the surviving cells versus dose and corrected for cloning efficiency. Apoptosis following ionizing radiation was determined by flow cytometry using the Annexin-V FITC kit and DAPI staining. Paraffin-embedded breast tumor blocks were obtained from 42 women with local breast tumor recurrence and 42 matched breast cancer patients without local cancer relapse treated with breast conserving therapy and stained with a 1:4000 dilution of polyclonal antibody to the Fhit protein and scored based on both intensity and distribution of Fhit staining within the invasive breast cancer component. Results: Treatment of Fhit -/- mouse epithelial cells with single fraction doses of ionizing radiation including 2, 4, 6, and 10 Gy result in 4-6 fold increase in cellular survival compared with isogenic parental cells from Fhit +/+ mice. Fhit -/- epithelial cells displayed 3-5 fold lower levels of apoptosis in response to both low and high doses of ionizing

  18. Transverse MHD shock waves in a partly ionized plasma

    International Nuclear Information System (INIS)

    Mathers, C.D.

    1980-01-01

    The structure of transverse MHD shock waves in a partly ionized hydrogen plasma is studied using a three-fluid model with collisional transport coefficients. The morphology of the various sublayers in the shock front is analyzed in detail and it is shown that strong shock waves have a characteristic viscous structure. Weak to moderate strength shock waves display a resistive structure in which the enhanced transverse resistivity due to ion-slip plays a significant role, leading to a pronounced peak in the ion temperature profile. Calculated shock structure profiles are also compared with experimental temperature data. Results in the form of tables and figures are presented for shock waves with fast Mach number ranging from 1-10 in hydrogen plasma with initial degree of ionization ranging from 5-100%. (author)

  19. Photoexcitation and ionization of hydrogen atom confined in Debye environment

    International Nuclear Information System (INIS)

    Lumb, S.; Lumb, S.; Nautiyal, V.

    2015-01-01

    The dynamics of a hydrogen atom confined in an impenetrable spherical box and under the effect of Debye screening, in the presence of intense short laser pulses of few femtosecond is studied in detail. The energy spectra and wave functions have been calculated using Bernstein polynomial (B-polynomial) method. Variation of transition probabilities for various transitions due to changes in Debye screening length, confinement radius as well as the parameters characterizing applied laser pulse is studied and explained. The results are found to be in good agreement with the results obtained by others. The photoexcitation and ionization of the atom strongly depend on confinement radius and screening parameter. For small confinement radii and for some values of screening parameter the atom is found to be ionized easily. The dynamics of the atom can be easily controlled by varying pulse parameters

  20. Recent Total Ionizing Dose Results and Displacement Damage Results for Candidate Spacecraft Electronics for NASA

    Science.gov (United States)

    Cochran, Donna J.; Buchner, Stephen P.; Irwin, Tim L.; LaBel, Kenneth A.; Marshall, Cheryl J.; Reed, Robert A.; Sanders, Anthony B.; Hawkins, Donald K.; Flanigan, Ryan J.; Cox, Stephen R.

    2005-01-01

    We present data on the vulnerability of a variety of candidate spacecraft electronics to total ionizing dose and displacement damage. Devices tested include optoelectronics, digital, analog, linear bipolar devices, hybrid devices, Analog-to- Digital Converters (ADCs), and Digital-to-Analog Converters (DACs), among others. T

  1. Microwave ionization and excitation of Ba Rydberg atoms

    International Nuclear Information System (INIS)

    Eichmann, U.; Dexter, J.L.; Xu, E.Y.; Gallagher, T.F.

    1989-01-01

    We have investigated ionization and excitation of the Ba 6sn s 1 S 0 and 6snd 1,3 D 2 series in strong microwave fields. The observed microwave ionization threshold fields, scaling as 0.28 n -5 , and the state mixing fields cannot be completely explained in terms of a single cycle Landau-Zener model. However, by taking into account multiphoton resonant transitions driven by many cycles of the microwave field we have been able to interpret the data. In particular multi-photon transitions have been found to be responsible for apparent resonance structures and for the unexpectedly low mixing fields. Not surprisingly, doubly excited valence states introduce irregularities into both the microwave ionization and the state mixing field values. (orig.)

  2. Initial ionization stage of FRC formation

    International Nuclear Information System (INIS)

    Commisso, R.J.; Armstrong, W.T.; Cochrane, J.C.; Ekdahl, C.A.; Lipson, J.; Linford, R.K.; Sherwood, E.G.; Siemon, R.E.; Tuszewski, M.

    1980-01-01

    A Field-Reversed Configuration (FRC) is a prolate compact torus that is confined by poloidal fields only. Theta-pinch formation of an FRC employs an initial bias field, B 1 , whose direction is opposite to that of the main theta-pinch field. Some fraction of the flux associated with this bias field eventually constitutes the closed-field-line flux of the FRC. Experimental and theoretical evidence suggest that the longest-lived FRC's are obtained when the closed flux is maximized. Because the initial ionization is done in the presence of the bias field, the actual bias flux available at the time of application of the main theta-pinch field depends strongly on the initial ionization, or preionization, technique used. In this paper we report on experiments characterizing the previously used theta-pinch preionization technique that employed a net field (bias plus preionization) null, or zero-crossing, of the axial component of the magnetic field to break down the gas. We also discuss results of experiments designed to develop preionization techniques in which the gas breakdown is not accomplished by a zero-crossing

  3. EVIDENCE OF VERY LOW METALLICITY AND HIGH IONIZATION STATE IN A STRONGLY LENSED, STAR-FORMING DWARF GALAXY AT z = 3.417

    International Nuclear Information System (INIS)

    Amorín, R.; Grazian, A.; Castellano, M.; Pentericci, L.; Fontana, A.; Sommariva, V.; Merlin, E.; Van der Wel, A.; Maseda, M.

    2014-01-01

    We investigate the gas-phase metallicity and Lyman continuum (LyC) escape fraction of a strongly gravitationally lensed, extreme emission-line galaxy at z = 3.417, J1000+0221S, recently discovered by the CANDELS team. We derive ionization- and metallicity-sensitive emission-line ratios from H+K band Large Binocular Telescope (LBT)/LUCI medium resolution spectroscopy. J1000+0221S shows high ionization conditions, as evidenced by its enhanced [O III]/[O II] and [O III]/Hβ ratios. Strong-line methods based on the available line ratios suggest that J1000+0221S is an extremely metal-poor galaxy, with a metallicity of 12+log (O/H) < 7.44 (Z < 0.05 Z ☉ ), placing it among the most metal-poor star-forming galaxies at z ≳ 3 discovered so far. In combination with its low stellar mass (2 × 10 8  M ☉ ) and high star formation rate (5 M ☉  yr –1 ), the metallicity of J1000+0221S is consistent with the extrapolation of the mass-metallicity relation traced by Lyman-break galaxies at z ≳ 3 to low masses, but it is 0.55 dex lower than predicted by the fundamental metallicity relation at z ≲ 2.5. These observations suggest a rapidly growing galaxy, possibly fed by massive accretion of pristine gas. Additionally, deep LBT/LBC photometry in the UGR bands are used to derive a limit to the LyC escape fraction, thus allowing us to explore for the first time the regime of sub-L* galaxies at z > 3. We find a 1σ upper limit to the escape fraction of 23%, which adds a new observational constraint to recent theoretical models predicting that sub-L* galaxies at high-z have high escape fractions and thus are the responsible for the reionization of the universe

  4. Atomic excitation and acceleration in strong laser fields

    International Nuclear Information System (INIS)

    Zimmermann, H; Eichmann, U

    2016-01-01

    Atomic excitation in the tunneling regime of a strong-field laser–matter interaction has been recently observed. It is conveniently explained by the concept of frustrated tunneling ionization (FTI), which naturally evolves from the well-established tunneling picture followed by classical dynamics of the electron in the combined laser field and Coulomb field of the ionic core. Important predictions of the FTI model such as the n distribution of Rydberg states after strong-field excitation and the dependence on the laser polarization have been confirmed in experiments. The model also establishes a sound basis to understand strong-field acceleration of neutral atoms in strong laser fields. The experimental observation has become possible recently and initiated a variety of experiments such as atomic acceleration in an intense standing wave and the survival of Rydberg states in strong laser fields. Furthermore, the experimental investigations on strong-field dissociation of molecules, where neutral excited fragments after the Coulomb explosion of simple molecules have been observed, can be explained. In this review, we introduce the subject and give an overview over relevant experiments supplemented by new results. (paper)

  5. Epicyclic helical channels for parametric resonance ionization cooling

    Energy Technology Data Exchange (ETDEWEB)

    Johson, Rolland Paul [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Derbenev, Yaroslav [Muons, Inc., Batavia, IL (United States)

    2015-08-23

    Proposed next-generation muon colliders will require major technical advances to achieve rapid muon beam cooling requirements. Parametric-resonance Ionization Cooling (PIC) is proposed as the final 6D cooling stage of a high-luminosity muon collider. In PIC, a half-integer parametric resonance causes strong focusing of a muon beam at appropriately placed energy absorbers while ionization cooling limits the beam’s angular spread. Combining muon ionization cooling with parametric resonant dynamics in this way should then allow much smaller final transverse muon beam sizes than conventional ionization cooling alone. One of the PIC challenges is compensation of beam aberrations over a sufficiently wide parameter range while maintaining the dynamical stability with correlated behavior of the horizontal and vertical betatron motion and dispersion. We explore use of a coupling resonance to reduce the dimensionality of the problem and to shift the dynamics away from non-linear resonances. PIC simulations are presented.

  6. On the SIMS Ionization Probability of Organic Molecules.

    Science.gov (United States)

    Popczun, Nicholas J; Breuer, Lars; Wucher, Andreas; Winograd, Nicholas

    2017-06-01

    The prospect of improved secondary ion yields for secondary ion mass spectrometry (SIMS) experiments drives innovation of new primary ion sources, instrumentation, and post-ionization techniques. The largest factor affecting secondary ion efficiency is believed to be the poor ionization probability (α + ) of sputtered material, a value rarely measured directly, but estimated to be in some cases as low as 10 -5 . Our lab has developed a method for the direct determination of α + in a SIMS experiment using laser post-ionization (LPI) to detect neutral molecular species in the sputtered plume for an organic compound. Here, we apply this method to coronene (C 24 H 12 ), a polyaromatic hydrocarbon that exhibits strong molecular signal during gas-phase photoionization. A two-dimensional spatial distribution of sputtered neutral molecules is measured and presented. It is shown that the ionization probability of molecular coronene desorbed from a clean film under bombardment with 40 keV C 60 cluster projectiles is of the order of 10 -3 , with some remaining uncertainty arising from laser-induced fragmentation and possible differences in the emission velocity distributions of neutral and ionized molecules. In general, this work establishes a method to estimate the ionization efficiency of molecular species sputtered during a single bombardment event. Graphical Abstract GRAPHICAL ABSTRACT TEXT HERE] -->.

  7. Increased ionization rate in laser enrichment

    International Nuclear Information System (INIS)

    Janes, G.S.; Pike, G.T.

    1977-01-01

    A system employing multiple, upper excitation levels in a technique for isotopically selective ionization to improve the ionization efficiency is described. Laser radiation is employed to excite particles with isotopic selectivity. Excitation is produced to a plurality of excited states below the ionization level with the result of increasing the number of available excited particles for ionization and thereby increasing the ionization cross section for improved system efficiency

  8. Ionization efficiency calculations for cavity thermoionization ion source

    International Nuclear Information System (INIS)

    Turek, M.; Pyszniak, K.; Drozdziel, A.; Sielanko, J.; Maczka, D.; Yuskevich, Yu.V.; Vaganov, Yu.A.

    2009-01-01

    The numerical model of ionization in a thermoionization ion source is presented. The review of ion source ionization efficiency calculation results for various kinds of extraction field is given. The dependence of ionization efficiency on working parameters like ionizer length and extraction voltage is discussed. Numerical simulations results are compared to theoretical predictions obtained from a simplified ionization model

  9. Simulation of ionization effects for high-density positron drivers in future plasma wakefield experiments

    International Nuclear Information System (INIS)

    Bruhwiler, D.L.; Dimitrov, D.A.; Cary, J.R.; Esarey, E.; Leemans, W.P.

    2003-01-01

    The plasma wakefield accelerator (PWFA) concept has been proposed as a potential energy doubler for present or future electron-positron colliders. Recent particle-in-cell (PIC) simulations have shown that the self-fields of the required electron beam driver can tunnel ionize neutral Li, leading to plasma wake dynamics differing significantly from that of a preionized plasma. It has also been shown, for the case of a preionized plasma, that the plasma wake of a positron driver differs strongly from that of an electron driver. We will present new PIC simulations, using the OOPIC code, showing the effects of tunneling ionization on the plasma wake generated by high-density positron drivers. The results will be compared to previous work on electron drivers with tunneling ionization and positron drivers without ionization. Parameters relevant to the energy doubler and the upcoming E-164x experiment at the Stanford Linear Accelerator Center will be considered

  10. Strong nebular line ratios in the spectra of z ∼ 2-3 star forming galaxies: first results from KBSS-MOSFIRE

    Energy Technology Data Exchange (ETDEWEB)

    Steidel, Charles C.; Rudie, Gwen C.; Strom, Allison L.; Trainor, Ryan F.; Konidaris, Nicholas P.; Matthews, Keith [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, 1216 East California Boulevard., MS 249-17, Pasadena, CA 91125 (United States); Pettini, Max [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Reddy, Naveen A. [Department of Physics and Astronomy, University of California, Riverside, 900 University Avenue, Riverside, CA 92521 (United States); Shapley, Alice E.; Kulas, Kristin R.; Mace, Gregory; McLean, Ian S. [University of California, Los Angeles, Department of Physics and Astronomy, 430 Portola Plaza, Los Angeles, CA 90095 (United States); Erb, Dawn K. [Center for Gravitation, Cosmology, and Astrophysics, Department of Physics, University of Wisconsin-Milwaukee, 1900 East Kenwood Boulevard, Milwaukee, WI 53211 (United States); Turner, Monica L. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)

    2014-11-10

    We present initial results of a deep near-IR spectroscopic survey covering the 15 fields of the Keck Baryonic Structure Survey using the recently commissioned MOSFIRE spectrometer on the Keck 1 telescope. We focus on a sample of 251 galaxies with redshifts 2.0 < z < 2.6, star formation rates (SFRs) 2 ≲ SFR ≲ 200 M {sub ☉} yr{sup –1}, and stellar masses 8.6 < log (M {sub *}/M {sub ☉}) < 11.4, with high-quality spectra in both H- and K-band atmospheric windows. We show unambiguously that the locus of z ∼ 2.3 galaxies in the 'BPT' nebular diagnostic diagram exhibits an almost entirely disjointed, yet similarly tight, relationship between the line ratios [N II] λ6585/Hα and [O III]/Hβ as compared to local galaxies. Using photoionization models, we argue that the offset of the z ∼ 2.3 BPT locus relative to that at z ∼ 0 is caused by a combination of harder stellar ionizing radiation field, higher ionization parameter, and higher N/O at a given O/H compared to most local galaxies, and that the position of a galaxy along the z ∼ 2.3 star-forming BPT locus is surprisingly insensitive to gas-phase oxygen abundance. The observed nebular emission line ratios are most easily reproduced by models in which the net stellar ionizing radiation field resembles a blackbody with effective temperature T {sub eff} = 50, 000-60, 000 K, the gas-phase oxygen abundances lie in the range 0.2 < Z/Z {sub ☉} < 1.0, and the ratio of gas-phase N/O is close to the solar value. We critically assess the applicability at high redshift of commonly used strong line indices for estimating gas-phase metallicity, and consider the implications of the small intrinsic scatter of the empirical relationship between excitation-sensitive line indices and M {sub *} (i.e., the 'mass-metallicity' relation) at z ≅ 2.3.

  11. Strong nebular line ratios in the spectra of z ∼ 2-3 star forming galaxies: first results from KBSS-MOSFIRE

    International Nuclear Information System (INIS)

    Steidel, Charles C.; Rudie, Gwen C.; Strom, Allison L.; Trainor, Ryan F.; Konidaris, Nicholas P.; Matthews, Keith; Pettini, Max; Reddy, Naveen A.; Shapley, Alice E.; Kulas, Kristin R.; Mace, Gregory; McLean, Ian S.; Erb, Dawn K.; Turner, Monica L.

    2014-01-01

    We present initial results of a deep near-IR spectroscopic survey covering the 15 fields of the Keck Baryonic Structure Survey using the recently commissioned MOSFIRE spectrometer on the Keck 1 telescope. We focus on a sample of 251 galaxies with redshifts 2.0 < z < 2.6, star formation rates (SFRs) 2 ≲ SFR ≲ 200 M ☉ yr –1 , and stellar masses 8.6 < log (M * /M ☉ ) < 11.4, with high-quality spectra in both H- and K-band atmospheric windows. We show unambiguously that the locus of z ∼ 2.3 galaxies in the 'BPT' nebular diagnostic diagram exhibits an almost entirely disjointed, yet similarly tight, relationship between the line ratios [N II] λ6585/Hα and [O III]/Hβ as compared to local galaxies. Using photoionization models, we argue that the offset of the z ∼ 2.3 BPT locus relative to that at z ∼ 0 is caused by a combination of harder stellar ionizing radiation field, higher ionization parameter, and higher N/O at a given O/H compared to most local galaxies, and that the position of a galaxy along the z ∼ 2.3 star-forming BPT locus is surprisingly insensitive to gas-phase oxygen abundance. The observed nebular emission line ratios are most easily reproduced by models in which the net stellar ionizing radiation field resembles a blackbody with effective temperature T eff = 50, 000-60, 000 K, the gas-phase oxygen abundances lie in the range 0.2 < Z/Z ☉ < 1.0, and the ratio of gas-phase N/O is close to the solar value. We critically assess the applicability at high redshift of commonly used strong line indices for estimating gas-phase metallicity, and consider the implications of the small intrinsic scatter of the empirical relationship between excitation-sensitive line indices and M * (i.e., the 'mass-metallicity' relation) at z ≅ 2.3.

  12. Profile distortion by beam space-charge in Ionization Profile Monitors

    CERN Document Server

    Vilsmeier, D; Wettig, T

    Measuring the transverse beam size in the Large Hadron Collider by using Ionization Profile Monitors is a difficult task for energies above injection during the energy ramp from 450 GeV to 6.5TeV. The beam size decreases from around 1mm to 200um and the brightness of the beam is high enough to destroy the structure of any form of interacting matter. While the electron trajectories are confined by an external electro-magnetic field which forces the electrons accordingly on helix paths with certain gyroradii, this gyration is heavily increased under the influence of the electric field of the beam. Smaller beam sizes, which go hand in hand with increased bunch electric fields, lead to larger gyroradii of the ionized electrons, which results in strongly distorted profiles. In addition, this distortion becomes more visible for smaller beam sizes as the extent of gyration grows compared to the actual beam size. Depending on the initial momentum distribution of the electrons, emerging from the ionization process wit...

  13. Impact-ionization autosolitons in compensated silicon

    International Nuclear Information System (INIS)

    Musaev, A.M.

    2004-01-01

    The results of the experimental identification and study on the autosolitons with the charge carriers self-production by the impact ionization of the indium deep acceptor levels in silicon in the strong electric fields at the temperature of 77 K are presented. The role of the activator in the considered autosolitons excitation model is played by the free charge carriers concentration and the role of the inhibitor by the carriers temperature. The solitons existence is determined by the fact, that the area of the carriers high concentration in the autosolitons center does not spread, while the diffusion flow from the autosolitons center is counterbalanced by the thermodiffusion flow [ru

  14. Physically sound parameterization of incomplete ionization in aluminum-doped silicon

    Directory of Open Access Journals (Sweden)

    Heiko Steinkemper

    2016-12-01

    Full Text Available Incomplete ionization is an important issue when modeling silicon devices featuring aluminum-doped p+ (Al-p+ regions. Aluminum has a rather deep state in the band gap compared to boron or phosphorus, causing strong incomplete ionization. In this paper, we considerably improve our recent parameterization [Steinkemper et al., J. Appl. Phys. 117, 074504 (2015]. On the one hand, we found a fundamental criterion to further reduce the number of free parameters in our fitting procedure. And on the other hand, we address a mistake in the original publication of the incomplete ionization formalism in Altermatt et al., J. Appl. Phys. 100, 113715 (2006.

  15. Estimate of electrical potential difference between plasmas with different degrees of ionization

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Chong [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-01-12

    The electrical potential difference has been estimated across the mixing region of two plasmas with different degrees of ionization. The estimation has been carried out in two different contexts of a charge neutral mixing region and a charge non-neutral sheath. Ion energy gained due to the potential difference has also been estimated. In both analyses, ion energy gain is proportional to the degree of ionization, and a fairly large ionization appears to be needed for overcoming the potential energy barrier of strongly coupled plasmas.

  16. Thin films deposited by laser ablation for the measurement of the ionizing and non-ionizing radiation

    International Nuclear Information System (INIS)

    Villarreal B, J.E.; Escobar A, L.; Camps, E.; Romero, S.; Gonzalez, P.; Salinas, B.

    2001-01-01

    In this work the obtained results to synthesize thin films of amorphous carbon with incorporated nitrogen and hydrogen are presented, as well as thin films of aluminium oxide using the laser ablation technique. The thin films were exposed to ionizing radiation (gamma rays of a 60 Co source, beta radiation of a 90 Sr source) and a non-ionizing radiation (UV radiation). The obtained results show that it is possible to obtain materials in thin film form with thickness of hundreds of nanometers, which present thermoluminescent response when being irradiated with ionizing radiation and non-ionizing radiation. (Author)

  17. Frustrated incomplete donor ionization in ultra-low resistivity germanium films

    International Nuclear Information System (INIS)

    Xu, Chi; Menéndez, J.; Senaratne, C. L.; Kouvetakis, J.

    2014-01-01

    The relationship between carrier concentration and donor atomic concentration has been determined in n-type Ge films doped with P. The samples were carefully engineered to minimize non-active dopant incorporation by using specially designed P(SiH 3 ) 3 and P(GeH 3 ) 3 hydride precursors. The in situ nature of the doping and the growth at low temperatures, facilitated by the Ge 3 H 8 and Ge 4 H 10 Ge sources, promote the creation of ultra-low resistivity films with flat doping profiles that help reduce the errors in the concentration measurements. The results show that Ge deviates strongly from the incomplete ionization expected when the donor atomic concentration exceeds N d  = 10 17  cm −3 , at which the energy separation between the donor and Fermi levels ceases to be much larger than the thermal energy. Instead, essentially full ionization is seen even at the highest doping levels beyond the solubility limit of P in Ge. The results can be explained using a model developed for silicon by Altermatt and coworkers, provided the relevant model parameter is properly scaled. The findings confirm that donor solubility and/or defect formation, not incomplete ionization, are the major factors limiting the achievement of very high carrier concentrations in n-type Ge. The commercially viable chemistry approach applied here enables fabrication of supersaturated and fully ionized prototypes with potential for broad applications in group-IV semiconductor technologies

  18. K-shell ionization by antiprotons

    International Nuclear Information System (INIS)

    Mehler, G.; Mueller, B.; Greiner, W.; Soff, G.

    1987-01-01

    We present first calculations for the impact parameter dependence of K-shell ionization rates in anti pCu and in anti pAg collisions at various projectile energies. We show that the effect of the attractive Coulomb potential on the Rutherford trajectory and the anti-binding effect caused by the negative charge of the antiproton result in a considerable increase of the ionization probability. Total ionization cross-sections for proton and antiproton projectiles are compared with each other and with experimental ionization cross-sections for protons. (orig.)

  19. A rapid novel derivatization of amphetamine and methamphetamine using 2,2,2-trichloroethyl chloroformate for gas chromatography electron ionization and chemical ionization mass spectrometric analysis.

    Science.gov (United States)

    Dasgupta, A; Spies, J

    1998-05-01

    Amphetamine and methamphetamine are commonly abused central nervous system stimulants. We describe a rapid new derivatization of amphetamine and methamphetamine using 2,2,2-trichloroethyl chloroformate for gas chromatography-mass spectrometric analysis. Amphetamine and methamphetamine, along with N-propyl amphetamine (internal standard), were extracted from urine using 1-chlorobutane. The derivatization with 2,2,2-trichloroethyl chloroformate can be achieved at room temperature in 10 minutes. The electron ionization mass spectrum of amphetamine 2,2,2-trichloroethyl carbamate showed two weak molecular ions at m/z 309 and 311, but showed diagnostic strong peaks at m/z 218, 220, and 222. In contrast, chemical ionization of the mass spectrum of amphetamine 2,2,2-trichloroethyl carbamate showed strong (M + 1) ions at m/z 310 and 312 and other strong diagnostic peaks at m/z 274 and 276. The major advantages of this derivative are the presence of a diagnostic cluster of peaks due to the isotopic effect of three chlorine atoms (isotopes 35 and 37) in the derivatized molecule and the relative ease of its preparation. We also observed strong molecular ions for derivatized methamphetamine in the chemical ionization mass spectrum, but the molecular ions were very weak in the electron ionization mass spectrum. We used the scan mode of mass spectrometry in all analyses. When using a urine standard containing 1,000 ng/mL of amphetamine (a 7.4-micromol/L concentration) and methamphetamine (a 6.7-micromol/L concentration), the within-run precisions were 4.8% for amphetamine and 3.6% for methamphetamine. The corresponding between-run precisions were 5.3% for amphetamine and 6.7% for methamphetamine. The assay was linear for amphetamine and methamphetamine concentrations of 250 to 5,000 ng/mL (amphetamine, 1.9-37.0 micromol/L; methamphetamine, 1.7-33.6 micromol/L). The detection limit was 100 ng/mL (amphetamine, 0.74 micromol/L; methamphetamine, 0.67 micromol/L) using the scan mode

  20. Control and dynamics of attosecond electron wave packets in strong laser fields

    International Nuclear Information System (INIS)

    Johnsson, P.; Remetter, T.; Varju, K.; L'Huillier; Lopez-Martens, R.; Valentin, C.; Balcou, P.; Kazamias, S.; Mauritsson, J.; Gaarde, M.B.; Schafer, K.J.; Mairess, Y.; Wabnitz, H.; Boutu, W.; Salieres, P.

    2005-01-01

    of 160 as duration. In the second experiment, we use these pulses to create electron wave packets of duration 180 as in argon and study the energy transfer from a strong infrared (IR) laser field to the ionized electrons as a function of the delay between the XUV and IR fields. At the zero crossings of the laser field, a significant energy (∼ 20 eV) is transferred from the IR field to the electrons resulting in dramatically enhanced above-threshold-ionization in conditions where the IR field alone does not induce any significant ionization of the medium. Further, by increasing the pulse length of the individual attosecond pulses, using a different thickness of the aluminum filter, a clear effect is seen in the delay-dependence of the photoelectron spectrum. In conclusion, the manipulations of the XUV amplitudes and phases that we have performed are the first step towards the production of arbitrary attosecond waveforms, which will facilitate broadband coherent control in the XUV range. Using these pulses as the injection mechanism of electron wave packets through ionization, we have studied the interaction between the EWPs and a strong IR field. With the pulse parameters used, the ionization is dominated by the APT, and tunable ATI plateaus appear as an effect of the dressing field. The strong delay dependence seen for these ATI spectra, is a direct consequence of the temporal localization of the EWPs to a time range much shorter than the period of the IR field. Because both the energy and duration of the EWPs can be varied independent of the IR laser, they should be very useful for the study and control of strong field processes. Refs. 2 (author)

  1. A four-component Dirac theory of ionization of a hydrogen molecular ion in a super-intense laser field

    International Nuclear Information System (INIS)

    Faisal, F H M

    2009-01-01

    In this communication, a four-component Dirac theory of ionization of a hydrogen molecular ion, H + 2 , in a super-intense laser field is presented. Analytic expressions for the spin-specific as well as the total ionization currents emitted from the ground state of the ion are derived. The results are given for arbitrary intensity, frequency, wavenumber and polarization of the field, and for the up or down spin of the bound and ionized states of the electron. They also apply for the case of inner-shell ionization of analogous heavier diatomic molecular ions. The presence of molecular two-slit interference effect, first found in the non-relativistic case, the spin-flip ionization current, and an asymmetry of the up- and down-spin currents similar to that predicted in the atomic case, is found to hold for the present relativistic molecular ionic case as well. The possibility of controlling the spin of the dominant ionization current in any direction by simply selecting the handedness of a circularly polarized incident laser field is pointed out. Finally, we note that the present results obtained within the strong field 'KFR' ansatz open up the way for an analogous fully relativistic four-component treatment for ionization of polyatomic molecules and clusters in super-intense laser fields. (fast track communication)

  2. Rydberg excitation of neutral nitric oxide molecules in strong UV and near-IR laser fields

    International Nuclear Information System (INIS)

    Lv Hang; Zhang Jun-Feng; Zuo Wan-Long; Xu Hai-Feng; Jin Ming-Xing; Ding Da-Jun

    2015-01-01

    Rydberg state excitations of neutral nitric oxide molecules are studied in strong ultraviolet (UV) and near-infra-red (IR) laser fields using a linear time-of-flight (TOF) mass spectrometer with the pulsed electronic field ionization method. The yield of Rydberg molecules is measured as a function of laser intensity and ellipticity, and the results in UV laser fields are compared with those in near-IR laser fields. The present study provides the first experimental evidence of neutral Rydberg molecules surviving in a strong laser field. The results indicate that a rescattering-after-tunneling process is the main contribution to the formation of Rydberg molecules in strong near-IR laser fields, while multi-photon excitation may play an important role in the strong UV laser fields. (paper)

  3. Effect of ionizing radiation on radionuclide speciation: Preliminary results from site-specific experiments in a basaltic system

    International Nuclear Information System (INIS)

    Reed, D.T.; Burnell, J.R.

    1986-01-01

    Rockwell Hanford Operations, under contract to the Department of Energy, is investigating the suitability of the Hanford site in the state of Washington as a high level nuclear waste repository. An important consideration in these investigations is the effect of ionizing radiation on the speciation of radionuclides in the groundwater after the high-level-waste container has been breached and there is direct contact between the groundwater and the waste form (controlled released period). The effect of ionizing radiation on radionuclide speciation depends on the radiation environment and site-specific chemistry near the waste container. With respect to these two aspects, the following results will be presented: a definition of the radiation environment during the controlled release period; preliminary site-specific experimental results: (1) basaltic systems spiked with radionuclides; (2) spent fuel-groundwater-basalt experiments

  4. Electron-electron correlation in two-photon double ionization of He-like ions

    Science.gov (United States)

    Hu, S. X.

    2018-01-01

    Electron correlation plays a crucial role in quantum many-body physics ranging from molecular bonding and strong-field-induced multielectron ionization, to superconducting in materials. Understanding the dynamic electron correlation in the photoionization of relatively simple quantum three-body systems, such as He and He-like ions, is an important step toward manipulating complex systems through photoinduced processes. Here we have performed ab initio investigations of two-photon double ionization (TPDI) of He and He-like ions (L i+,B e2 + , and C4 +) exposed to intense attosecond x-ray pulses. Results from such fully correlated quantum calculations show weaker and weaker electron correlation effects in TPDI spectra as the ionic charge increases, which is opposite to the intuition that the absolute increase of correlation in the ground state should lead to more equal energy sharing in photoionization. These findings indicate that the final-state electron-electron correlation ultimately determines the energy sharing of the two ionized electrons in TPDI.

  5. Continuum Lowering and Fermi-Surface Rising in Strongly Coupled and Degenerate Plasmas

    International Nuclear Information System (INIS)

    Hu, S. X.

    2017-01-01

    Here, continuum lowering is a well-known and important physics concept that describes the ionization potential depression (IPD) in plasmas caused by thermal-/pressure-induced ionization of outer-shell electrons. The existing IPD models are often used to characterize plasma conditions and to gauge opacity calculations. Recent precision measurements have revealed deficits in our understanding of continuum lowering in dense hot plasmas. However, these investigations have so far been limited to IPD in strongly coupled but nondegenerate plasmas. Here, we report a first-principles study of the K-edge shifting in both strongly coupled and fully degenerate carbon plasmas, with quantum molecular dynamics (QMD) calculations based on the all-electron density-functional theory (DFT). The resulted K-edge shifting versus plasma density, as a probe to the continuum lowering and the Fermi-surface rising, is found to be significantly different from predictions of existing IPD models. In contrast, a simple model of “single atom in box” (SAIB), developed in this work, accurately predicts K-edge locations as what ab-initio calculations provide.

  6. Tunneling Ionization of Diatomic Molecules

    DEFF Research Database (Denmark)

    Svensmark, Jens Søren Sieg

    2016-01-01

    When a molecule is subject to a strong laser field, there is a probability that an electron can escape, even though the electrons are bound by a large potential barrier. This is possible because electrons are quantum mechanical in nature, and they are therefore able to tunnel through potential...... barriers, an ability classical particles do not possess. Tunnelling is a fundamental quantum mechanical process, a process that is distinctly non-classical, so solving this tunnelling problem is not only relevant for molecular physics, but also for quantum theory in general. In this dissertation the theory...... of tunneling ionizaion of molecules is presented and the results of numerical calculations are shown. One perhaps surprising result is, that the frequently used Born-Oppenheimer approximation breaks down for weak fields when describing tunneling ionization. An analytic theory applicable in the weak-field limit...

  7. A new class of strongly coupled plasmas inspired by sonoluminescence

    Science.gov (United States)

    Bataller, Alexander; Plateau, Guillaume; Kappus, Brian; Putterman, Seth

    2014-10-01

    Sonoluminescence originates in a strongly coupled plasma with a near liquid density and a temperature of ~10,000 K. This plasma is in LTE and therefore, it should be a general thermodynamic state. To test the universality of sonoluminescence, similar plasma conditions were generated using femtosecond laser breakdown in high pressure gases. Calibrated streak spectroscopy reveals both transport and thermodynamic properties of a strongly coupled plasma. A blackbody spectrum, which persists long after the exciting laser has turned off, indicates the presence of a highly ionized LTE microplasma. In parallel with sonoluminescence, this thermodynamic state is achieved via a considerable reduction in the ionization potential. We gratefully acknowledge support from DARPA MTO for research on microplasmas. We thank Brian Naranjo, Keith Weninger, Carlos Camara, Gary Williams, and John Koulakis for valuable discussions.

  8. On possible structures of normal ionizing shock waves in electromagnetic shock tubes

    International Nuclear Information System (INIS)

    Liberman, M.A.; Synakh, V.S.; Zakajdakhov, V.V.; Velikovich, A.L.

    1982-01-01

    The problem of possible structures of normal ionizing shock waves is studied. On the basis of the general theory of ionizing shock waves in magnetic fields, a similarity solution of the piston problem for an impenetrable piston and a magnetic piston is described and a numerical solution of the non-stationary piston problem is obtained. It is shown that precursor photo-ionization of the neutral gas by the radiation of the shock-heated gas is the dominant factor in shaping normal ionizing shock structures. In particular, it is shown that the strong overheating of atoms and ions in shock fronts is due to the tensor form of Ohm's law in the precursor region. (author)

  9. Volatile sulfur compounds in foods as a result of ionizing radiation

    Science.gov (United States)

    Ionizing radiation improves food safety and extends shelf life by inactivating food-borne pathogens and spoilage microorganisms. However, irradiation may induce the development of an off-odor, particularly at high doses. The off-odor has been called “irradiation odor”. Substantial evidence suggests ...

  10. Neutral Atom Diffusion in a Partially Ionized Prominence Plasma

    Science.gov (United States)

    Gilbert, Holly

    2010-01-01

    The support of solar prominences is normally described in terms of a magnetic force on the prominence plasma that balances the solar gravitational force. Because the prominence plasma is only partially ionized. it is necessary to consider in addition the support of the neutral component of the prominence plasma. This support is accomplished through a frictional interaction between the neutral and ionized components of the plasma, and its efficacy depends strongly on the degree of ionization of the plasma. More specifically, the frictional force is proportional to the relative flow of neutral and ion species, and for a sufficiently weakly ionized plasma, this flow must be relatively large to produce a frictional force that balances gravity. A large relative flow, of course, implies significant draining of neutral particles from the prominence. We evaluate the importance of this draining effect for a hydrogen-helium plasma, and consider the observational evidence for cross-field diffusion of neutral prominence material,

  11. Highly ionized plasma plume generation by long-pulse CO2 laser irradiation of solid targets in strong axial magnetic fields

    International Nuclear Information System (INIS)

    Hoffman, A.L.; Crawford, E.A.

    1982-01-01

    The present work utilizes high f number optics and is directed primarily at controlling the conditions in the magnetically confined plume. Typically, fully ionized carbon plasmas have been produced with 10 18 cm -3 electron densities and 100 to 150 eV electron temperatures. These carbon plasmas have been doped with high Z atoms in order to study ionization and emission rates at the above conditions

  12. Initial ionization stage of FRC formation

    Energy Technology Data Exchange (ETDEWEB)

    Commisso, R.J.; Armstrong, W.T.; Cochrane, J.C.; Ekdahl, C.A.; Lipson, J.; Linford, R.K.; Sherwood, E.G.; Siemon, R.E.; Tuszewski, M.

    1980-01-01

    A Field-Reversed Configuration (FRC) is a prolate compact torus that is confined by poloidal fields only. Theta-pinch formation of an FRC employs an initial bias field, B/sub 1/, whose direction is opposite to that of the main theta-pinch field. Some fraction of the flux associated with this bias field eventually constitutes the closed-field-line flux of the FRC. Experimental and theoretical evidence suggest that the longest-lived FRC's are obtained when the closed flux is maximized. Because the initial ionization is done in the presence of the bias field, the actual bias flux available at the time of application of the main theta-pinch field depends strongly on the initial ionization, or preionization, technique used. In this paper we report on experiments characterizing the previously used theta-pinch preionization technique that employed a net field (bias plus preionization) null, or zero-crossing, of the axial component of the magnetic field to break down the gas. We also discuss results of experiments designed to develop preionization techniques in which the gas breakdown is not accomplished by a zero-crossing.

  13. Effects of ionizing radiations on insects

    International Nuclear Information System (INIS)

    Goyffon, Max.

    1978-01-01

    The most traditional effects caused by irradiation are development and morphogenesis disorders since on the whole the sensitivity of the developing organism to ionizing radiations is all the greater as the growth rate is faster. During the development of higher insects two categories of cell divide: larval cells on the one hand, which differentiate immediately after segmentation and give rise to larval organisms, and embryonic cells on the other which divide actively to form various islets or imaginal discs destined, each to its own extent, to provide the organs of the adult. Two cell categories thus coexist in the larva, one undergoing differentiation and the other multiplication, the radiosensitivity of which will be quite different for this very reason and will account at least partly, where the lethal effect of ionizing radiations is concerned, for the results observed. Three chapters deal in turn with effects on longevity, on regeneration and restoration and on morphogenesis and development. Strong doses give rise beyond a certain threshold to the appearance of acute radiodermatitis; their clinical signs and different degrees of seriousness liken them to burns of a special type [fr

  14. Technical sheets of ionizing radiations. 2. Non-ionizing radiations

    International Nuclear Information System (INIS)

    Anon.

    1975-01-01

    The biological effects of different non-ionizing radiations are studied: ultra-violet radiation, visible radiation, infrared radiation, micrometric waves, ultrasonics. In spite of their apparent diversity these radiations are similar in their physico-chemical effects, but in view of their widely varying production methods and types of application each type is considered separately. It is pointed out that no organization resembling the CIPR exists in the field of non-ionizing radiations, the result being a great disparity amongst the different legislations in force [fr

  15. Tunnel ionization of atoms and molecules: How accurate are the weak-field asymptotic formulas?

    Science.gov (United States)

    Labeye, Marie; Risoud, François; Maquet, Alfred; Caillat, Jérémie; Taïeb, Richard

    2018-05-01

    Weak-field asymptotic formulas for the tunnel ionization rate of atoms and molecules in strong laser fields are often used for the analysis of strong field recollision experiments. We investigate their accuracy and domain of validity for different model systems by confronting them to exact numerical results, obtained by solving the time dependent Schrödinger equation. We find that corrections that take the dc-Stark shift into account are a simple and efficient way to improve the formula. Furthermore, analyzing the different approximations used, we show that error compensation plays a crucial role in the fair agreement between exact and analytical results.

  16. S-matrix analysis of vibrational and alignment effects in intense-field multiphoton ionization of molecules

    International Nuclear Information System (INIS)

    Requate, A.

    2007-03-01

    Theoretical analysis of the vibrational excitation of small molecules during multiphoton ionization in intense laser fields of optical and infrared frequencies. Analysis of the alignment dependence of the electron impact ionization of diatomic molecules in the presence of an intense laser field as the final step in the process of Nonsequential Double Ionization. Quantum mechanical description using S-matrix theory in Strong Field Approximation (SFA), i.e. beyond perturbation theory. (orig.)

  17. S-matrix analysis of vibrational and alignment effects in intense-field multiphoton ionization of molecules

    Energy Technology Data Exchange (ETDEWEB)

    Requate, A

    2007-03-15

    Theoretical analysis of the vibrational excitation of small molecules during multiphoton ionization in intense laser fields of optical and infrared frequencies. Analysis of the alignment dependence of the electron impact ionization of diatomic molecules in the presence of an intense laser field as the final step in the process of Nonsequential Double Ionization. Quantum mechanical description using S-matrix theory in Strong Field Approximation (SFA), i.e. beyond perturbation theory. (orig.)

  18. The high intensity approximation applied to multiphoton ionization

    International Nuclear Information System (INIS)

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

    1980-08-01

    It is shown that the most commonly used high intensity approximations as applied to ionization by strong electromagnetic fields are related. The applicability of the steepest descent method in these approximations, and the relation between them and first-order perturbation theory, are also discussed. (Author) [pt

  19. Electron-Nuclear Energy Sharing in Above-Threshold Multiphoton Dissociative Ionization of H2

    DEFF Research Database (Denmark)

    Wu, J.; Kunitski, M.; Pitzer, M.

    2013-01-01

    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....

  20. Laser-enhanced ionization spectroscopy around the ionization limit

    International Nuclear Information System (INIS)

    Axner, O.; Berglind, T.; Sjoestroem, S.

    1986-01-01

    Laser-induced photoionization and Laser-Enhanced collision Ionization (LEI) of Na, Tl, and Li in flames are detected by measuring the production of charges following a laser excitation. The ionization signal is investigated for excitations of the atoms from lower lying states both to Rydberg states close to the ionization limit, as well as to continuum states, i.e. the process of collision ionization is compared with that of photoionization. The qualitative behaviour of the ionization signal when scanning across the ionization limit is studied. It is shown that the ionization signal has a smooth behaviour when passing from bound states into continuum states. The laser-induced photoionization signal strength of atoms in flames is both calculated and measured and a good agreement is obtained. A calculation of wavelength dependent photoionization signal strengths for a number of elements is also presented. Photoionization is used to determine flame- and geometry-dependent parameters. An implication of photoionization in connection with LEI spectrometry for trace element analysis is that there will be a significant increase in background noise if the sample contains high concentrations of easily photoionizing elements and short wavelength light is used. (orig.)

  1. Impact ionization in GaAs: A screened exchange density-functional approach

    International Nuclear Information System (INIS)

    Picozzi, S.; Asahi, R.; Geller, C.B.; Continenza, A.; Freeman, A.J.

    2001-01-01

    Results are presented of a fully ab initio calculation of impact ionization rates in GaAs within the density functional theory framework, using a screened-exchange formalism and the highly precise all-electron full-potential linearized augmented plane wave method. The calculated impact ionization rates show a marked orientation dependence in k space, indicating the strong restrictions imposed by the conservation of energy and momentum. This anisotropy diminishes as the impacting electron energy increases. A Keldysh type fit performed on the energy-dependent rate shows a rather soft edge and a threshold energy greater than the direct band gap. The consistency with available Monte Carlo and empirical pseudopotential calculations shows the reliability of our approach and paves the way to ab initio calculations of pair production rates in new and more complex materials

  2. Indirect processes in electron impact ionization of Kr24+ and Kr25+

    International Nuclear Information System (INIS)

    Chen, M.H.; Reed, K.J.

    1992-09-01

    Electron-impact ionization cross sections have been calculated for magnesiumlike Kr 24+ and sodiumlike Kr 25+ . Electron-impact ionization is an important atomic process in hot dense plasmas. It can affect the ionization balance, electron temperature, electron density, and level population in the plasma. In the past decade, theoretical and experimental studies have revealed that indirect processes can make significant contributions to the cross sections for electron impact ionization of positive ions. The most important indirect process is excitation of an inner-shell electron followed by Auger emission. Higher-order processes such as resonant excitation followed by sequential double Auger emission, can also contribute significantly. The contributions of excitation-autoionization and resonant excitation double autoionization (REDA) were included, in addition to the cross sections for direct ionization of a 3s electron. The calculations were carried out using the relativistic distorted wave methods and the multiconfiguration Dirac-Fock model. For Kr 25+ , the total cross section is about 5 times the direct ionization cross section. For the Kr 24+ , the indirect contribution is about 2.5 times the direct ionization cross section. The REDA process produces many strong resonances and contributes about 20% to the average ionization cross section

  3. Semi-classical description of Rydberg atoms in strong, single-cycle electromagnetic pulses

    International Nuclear Information System (INIS)

    Jensen, R.V.; Sanders, M.M.

    1993-01-01

    Recent experimental measurements of the excitation and ionization of Rydberg atoms by single-cycle, electromagnetic pulses have revealed a variety of novel features. Because many quantum states are strongly coupled by the broadband radiation in the short pulse, the traditional methods of quantum mechanics are inadequate to account for the experimental results. We have therefore developed a semi-classical description of the interaction of both hydrogenic and non-hydrogenic atoms with single-cycle pulses of intense, electromagnetic radiation which is based on the strong correspondence theory of Percival and Richards. This theory, which was originally introduced for the description of strong atomic collisions, accounts for some of the surprising features of the experimental measurements and provides new predictions for future experimental studies

  4. Ionization of one- and three-dimensionally-oriented asymmetric-top molecules by intense circularly polarized femtosecond laser pulses

    DEFF Research Database (Denmark)

    Hansen, Jonas Lerche; Holmegaard, Lotte; Kalhøj, Line

    2011-01-01

    are quantum-state selected using a deflector and three-dimensionally (3D) aligned and oriented adiabatically using an elliptically polarized laser pulse in combination with a static electric field. A characteristic splitting in the molecular frame photoelectron momentum distribution reveals the position...... of the nodal planes of the molecular orbitals from which ionization occurs. The experimental results are supported by a theoretical tunneling model that includes and quantifies the splitting in the momentum distribution. The focus of the present article is to understand strong-field ionization from 3D...

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

    Energy Technology Data Exchange (ETDEWEB)

    White, Jeff; Ackad, Edward [Department of Physics, Southern Illinois University Edwardsville, Edwardsville, Illinois 62026 (United States)

    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.

  6. [Ionizing and non-ionizing radiation (comparative risk estimations)].

    Science.gov (United States)

    Grigor'ev, Iu G

    2012-01-01

    The population has widely used mobile communication for already more than 15 years. It is important to note that the use of mobile communication has sharply changed the conditions of daily exposure of the population to EME We expose our brain daily for the first time in the entire civilization. The mobile phone is an open and uncontrollable source of electromagnetic radiation. The comparative risk estimation for the population of ionizing and non-ionizing radiation was carried out taking into account the real conditions of influence. Comparison of risks for the population of ionizing and non-ionizing radiation leads us to a conclusion that EMF RF exposure in conditions of wide use of mobile communication is potentially more harmful than ionizing radiation influence.

  7. Phase and ellipticity dependence of the photoelectron angular distribution in non-resonant two-photon ionization of atomic hydrogen. I

    International Nuclear Information System (INIS)

    Faye, M; Wane, S T

    2011-01-01

    We study the ellipticity and the dependence on the phase lag (lead) (between the semimajor and the semiminor axes of the field components) of the photoelectron angular distribution (PAD) in the non-resonant two-photon ionization of atomic hydrogen. We establish exact analytical expressions for azimuthal PAD for 3s, 3p and 3d excited initial states, marked by the occurrence of an asymmetric term. This term gives rise to elliptic dichroism (ED), which can be obtained in two ways: either with the left (versus right) ellipticity, or with the phase lag (versus lead); for 3s and 3p initial states, it is shown that the quantum phase of continua is directly related to the phase lag, one-photon below-threshold ionization, and indirectly one photon above. Another important result is that the magnetic sublevels, m = 0, for 3p and m = ±1, for 3d, do not contribute to the azimuthal PAD. Our numerical results show, for 3s and 3d, and near-threshold ionization, that the PAD has maxima either along the semimajor or the semiminor axis, while for above-threshold ionization, they are always shifted from these axes. However, the maxima of the corresponding ED coincide with the PAD maxima, while for 3p, they are shifted from the PAD minima. A strong dependence of the ED sign is noted, regardless of the state or the process. However, strong ED signals are obtained for the 3s initial state and below-threshold ionization.

  8. Phase and ellipticity dependence of the photoelectron angular distribution in non-resonant two-photon ionization of atomic hydrogen. I

    Energy Technology Data Exchange (ETDEWEB)

    Faye, M; Wane, S T, E-mail: mamadou.faye@ucad.edu.sn [Departement de Physique, Faculte des Sciences et Techniques, Universite Cheikh Anta Diop, Boulevard Martin Luther King, (Corniche Ouest) BP 5005-Dakar Fann (Senegal)

    2011-03-14

    We study the ellipticity and the dependence on the phase lag (lead) (between the semimajor and the semiminor axes of the field components) of the photoelectron angular distribution (PAD) in the non-resonant two-photon ionization of atomic hydrogen. We establish exact analytical expressions for azimuthal PAD for 3s, 3p and 3d excited initial states, marked by the occurrence of an asymmetric term. This term gives rise to elliptic dichroism (ED), which can be obtained in two ways: either with the left (versus right) ellipticity, or with the phase lag (versus lead); for 3s and 3p initial states, it is shown that the quantum phase of continua is directly related to the phase lag, one-photon below-threshold ionization, and indirectly one photon above. Another important result is that the magnetic sublevels, m = 0, for 3p and m = {+-}1, for 3d, do not contribute to the azimuthal PAD. Our numerical results show, for 3s and 3d, and near-threshold ionization, that the PAD has maxima either along the semimajor or the semiminor axis, while for above-threshold ionization, they are always shifted from these axes. However, the maxima of the corresponding ED coincide with the PAD maxima, while for 3p, they are shifted from the PAD minima. A strong dependence of the ED sign is noted, regardless of the state or the process. However, strong ED signals are obtained for the 3s initial state and below-threshold ionization.

  9. Ionization-potential depression and dynamical structure factor in dense plasmas

    Science.gov (United States)

    Lin, Chengliang; Röpke, Gerd; Kraeft, Wolf-Dietrich; Reinholz, Heidi

    2017-07-01

    The properties of a bound electron system immersed in a plasma environment are strongly modified by the surrounding plasma. The modification of an essential quantity, the ionization energy, is described by the electronic and ionic self-energies, including dynamical screening within the framework of the quantum statistical theory. Introducing the ionic dynamical structure factor as the indicator for the ionic microfield, we demonstrate that ionic correlations and fluctuations play a critical role in determining the ionization potential depression. This is, in particular, true for mixtures of different ions with large mass and charge asymmetry. The ionization potential depression is calculated for dense aluminum plasmas as well as for a CH plasma and compared to the experimental data and more phenomenological approaches used so far.

  10. Measurement of the first ionization potential of astatine by laser ionization spectroscopy

    Science.gov (United States)

    Rothe, S.; Andreyev, A. N.; Antalic, S.; Borschevsky, A.; Capponi, L.; Cocolios, T. E.; De Witte, H.; Eliav, E.; Fedorov, D. V.; Fedosseev, V. N.; Fink, D. A.; Fritzsche, S.; Ghys, L.; Huyse, M.; Imai, N.; Kaldor, U.; Kudryavtsev, Yuri; Köster, U.; Lane, J. F. W.; Lassen, J.; Liberati, V.; Lynch, K. M.; Marsh, B. A.; Nishio, K.; Pauwels, D.; Pershina, V.; Popescu, L.; Procter, T. J.; Radulov, D.; Raeder, S.; Rajabali, M. M.; Rapisarda, E.; Rossel, R. E.; Sandhu, K.; Seliverstov, M. D.; Sjödin, A. M.; Van den Bergh, P.; Van Duppen, P.; Venhart, M.; Wakabayashi, Y.; Wendt, K. D. A.

    2013-01-01

    The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of the minute quantities of artificially produced isotopes or by performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential. Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states enabled the first determination of the ionization potential of the astatine atom, 9.31751(8) eV. New ab initio calculations are performed to support the experimental result. The measured value serves as a benchmark for quantum chemistry calculations of the properties of astatine as well as for the theoretical prediction of the ionization potential of superheavy element 117, the heaviest homologue of astatine. PMID:23673620

  11. Formation and metastable decomposition of unprotonated ammonia cluster ions upon femtosecond ionization

    International Nuclear Information System (INIS)

    Buzza, S.A.; Wei, S.; Purnell, J.; Castleman, A.W. Jr.

    1995-01-01

    The formation and metastable dissociation mechanism of unprotonated ammonia cluster ions, (NH 3 ) + n , produced by multiphoton ionization (MPI) at 624 nm and a nominal pulse width of 350 fs, are investigated through a reflectron time-of-flight (TOF) mass spectrometric technique. Detection of the unprotonated ions after femtosecond and nanosecond multiphoton ionization under various intensity conditions is explained. The role of the energy of the ionizing photons, and the observation of these ions after femtosecond MPI is examined. The formation of the unprotonated series is found to be a function of intensity in the case of ionization on the nanosecond time scale, but not so for the femtosecond time domain. The results can be explained in terms of ionization mechanisms and ionizing pulse durations. The findings of the present study suggest that the unprotonated ions are trapped behind the barrier to intracluster proton transfer and/or concomitant NH 2 loss. The studies of metastable decomposition also reveal that the unprotonated ammonia cluster ions dissociate in the field-free region of the TOF by losing an NH 2 radical rather than via the evaporative loss of NH 3 as occurs for protonated clusters. Additionally, isotopic investigations of the unimolecular decay reveal a strong dependence on the conditions of cluster formation. The cluster formation condition dependence of the unimolecular decay is further investigated by altering formation temperatures and observing the consequences reflected by changes in the spontaneous metastable decay rate constant. This is a unique example of a cluster system whose metastable dissociation does not obey an evaporative ensemble model

  12. Nature of the ionizing source of the nuclear gas in NGC 1052

    International Nuclear Information System (INIS)

    Keel, W.C.; Miller, J.S.

    1983-01-01

    We examine the ionization and physical state of the emission-line region in the nucleus of elliptical galaxy NGC 1052. The [O III] lambda4363/lambda5007 ratio, frequently used as a diagnostic for ionization mechanisms, is very poorly determined because of difficulties in matching the underlying stellar continuum spectrum, which is unusual in having very strong lines for the galaxy luminosity. Within these limitations, we find the [O III] temperature to be only marginally compatible with shock models, and the overall emission spectrum to be better fitted by photoionization models with a very dilute flat-spectrum central source. In any event, the case for NGC 1052 as a shock-heated nucleus is not strong

  13. Screening of ionic cores in partially ionized plasmas within linear response

    International Nuclear Information System (INIS)

    Gericke, D. O.; Vorberger, J.; Wuensch, K.; Gregori, G.

    2010-01-01

    We employ a pseudopotential approach to investigate the screening of ionic cores in partially ionized plasmas. Here, the effect of the tightly bound electrons is condensed into an effective potential between the (free) valence electrons and the ionic cores. Even for weak electron-ion coupling, the corresponding screening clouds show strong modifications from the Debye result for elements heavier than helium. Modifications of the theoretically predicted x-ray scattering signal and implications on measurements are discussed.

  14. Possible ionization ''ignition'' in laser-driven clusters

    International Nuclear Information System (INIS)

    Rose-Petruck, C.; Schafer, K.J.; Barty, C.P.J.

    1995-01-01

    The authors use Classical Trajectory Monte Carlo (CTMC) simulations to study the ionization of small rare gas clusters in short pulse, high intensity laser fields. They calculate, for a cluster of 25 neon atoms, the ionization stage reached and the average kinetic energy of the ionized electrons as functions of time and peak laser intensity. The CTMC calculations mimic the results of the much simpler barrier suppression model in the limit of isolated atoms. At solid density the results give much more ionization in the cluster than that predicted by the barrier suppression model. They find that when the laser intensity reaches a threshold value such that on average one electron is ionized from each atom, the cluster atoms rapidly move to higher ionization stages, approaching Ne +8 in a few femtoseconds. This ignition process creates an ultrafast pulse of energetic electrons in the cluster at quite modest laser intensities

  15. CRESU studies of electron attachment and Penning ionization at temperatures down to 48 K

    International Nuclear Information System (INIS)

    Le Garrec, J.L.; Mitchell, J.B.A.; Rowe, B.R.

    1996-01-01

    The object of the present report is to present results obtained for electron attachment and Penning ionization, obtained with the addition of a Langmuir probe to the measurement apparatus. Measurements of the rate coefficients for electron attachment and Penning ionization are performed using the standard techniques for the flow reactors. Rate coefficients for the Penning ionisation of argon, nitrogen molecule, oxygen molecule by helium metastable are presented. The results obtained concerning the attachment of electrons to SF 6 (non-dissociative), CCl 2 F 2 (producing Cl - ), and CF 3 Br as a function of temperature are presented. The differences observed, and the variation of the value of β below 100 K, provides evidence of the strong influence of the internal state (probably vibrational) of the CF 3 Br molecule on its dissociative attachment

  16. Analytical form of current-voltage characteristic of parallel-plane, cylindrical and spherical ionization chambers with homogeneous ionization

    Energy Technology Data Exchange (ETDEWEB)

    Stoyanov, D G [Faculty of Engineering and Pedagogy in Sliven, Technical University of Sofia, 59, Bourgasko Shaussee Blvd, 8800 Sliven (Bulgaria)

    2007-11-15

    The elementary processes taking place in the formation of charged particles and their flow in parallel-plane, cylindrical and spherical geometry cases of ionization chamber are considered. On the basis of particles and charges balance a differential equation describing the distribution of current densities in the ionization chamber volume is obtained. As a result of the differential equation solution an analytical form of the current-voltage characteristic of an ionization chamber with homogeneous ionization is obtained. For the parallel-plane case comparision with experimental data is performed.

  17. Analytical form of current-voltage characteristic of parallel-plane, cylindrical and spherical ionization chambers with homogeneous ionization

    International Nuclear Information System (INIS)

    Stoyanov, D G

    2007-01-01

    The elementary processes taking place in the formation of charged particles and their flow in parallel-plane, cylindrical and spherical geometry cases of ionization chamber are considered. On the basis of particles and charges balance a differential equation describing the distribution of current densities in the ionization chamber volume is obtained. As a result of the differential equation solution an analytical form of the current-voltage characteristic of an ionization chamber with homogeneous ionization is obtained. For the parallel-plane case comparision with experimental data is performed

  18. Energetic particles and ionization in the nighttime middle and low latitude ionosphere

    International Nuclear Information System (INIS)

    Voss, H.D.; Smith, L.G.

    1977-01-01

    Seven Nike Apache rockets, each equipped with an energetic particle spectrometer (12 E 80 keV) and electron-density experiments, were launched from Wallops Island, Virginia and Chilca, Peru, under varying geomagnetic conditions near midnight. At Wallops Island the energetic particle flux (E 40 keV) is found to be strongly dependent on Kp. The pitch-angle distribution is asymmetrical about a peak at 90 D signifying a predominately quasi-trapped flux and explaining the linear increase of count rate with altitute in the altitude region 120 to 200 km. The height-averaged ionization rates derived from the electron-density profiles are consistent with the rates calculated from the observed total particle flux for magnetic index Kp 3. In the region 90 to 110 km it is found that the nighttime ionization is primarily a result of Ly-beta radiation from the geocorona and interplanetary hydrogen for even very disturbed conditions. Below 90 km during rather disturbed conditions energetic electrons can be a significant ionization source. Two energetic particle precipitation zones have been identified at midlatitudes

  19. Energetic particles and ionization in the nighttime middle and low latitude ionosphere

    Science.gov (United States)

    Voss, H. D.; Smith, L. G.

    1977-01-01

    Seven Nike Apache rockets, each equipped with an energetic particle spectrometer (12 E 80 keV) and electron-density experiments, were launched from Wallops Island, Virginia and Chilca, Peru, under varying geomagnetic conditions near midnight. At Wallops Island the energetic particle flux (E 40 keV) is found to be strongly dependent on Kp. The pitch-angle distribution is asymmetrical about a peak at 90 D signifying a predominately quasi-trapped flux and explaining the linear increase of count rate with altitute in the altitude region 120 to 200 km. The height-averaged ionization rates derived from the electron-density profiles are consistent with the rates calculated from the observed total particle flux for magnetic index Kp 3. In the region 90 to 110 km it is found that the nighttime ionization is primarily a result of Ly-beta radiation from the geocorona and interplanetary hydrogen for even very disturbed conditions. Below 90 km during rather disturbed conditions energetic electrons can be a significant ionization source. Two energetic particle precipitation zones have been identified at midlatitudes.

  20. Cross-Field Current Instabilities in Thin Ionization Layers and the Enhanced Aurora

    International Nuclear Information System (INIS)

    Johnson, Jay R.; Okuda, Hideo

    2008-01-01

    Nearly half of the time, auroral displays exhibit thin, bright layers known as 'enhanced aurora'. There is a substantial body of evidence that connects these displays with thin, dense, heavy ion layers in the E-region. Based on the spectral characteristics of the enhanced layers, it is believed that they result when wave-particle interaction heats ambient electrons to energies at or just above the 17 eV ionization energy of N2. While there are several possible instabilities that could produce suprathermal electrons in thin layers, there has been no clear theoretical investigation which examines in detail how wave instabilities in the thin ionization layers could develop and produce the suprathermal electrons. We examine instabilities which would occur in thin, dense, heavy ion layers using extensive analytical analysis combined with particle simulations. We analyze a cross field current instability that is found to be strongly unstable in the heavy ion layers. Electrostatic simulations show that substantial heating of the ambient electrons occurs with energization at or above the N2 ionization energy.

  1. Equation of state of partially-ionized dense plasmas

    International Nuclear Information System (INIS)

    Rogers, F.J.

    1989-01-01

    This paper describes methods for calculating the equation of state of partially-ionized dense plasmas. The term dense plasma is used rather than strongly coupled plasma, since it is possible that at plasma conditions such that only a few levels can be observed spectroscopically the plasma coupling parameters are not large. Due mainly to their importance in theoretical astrophysics, the properties of partially ionized plasmas have been of interest for a long while. More recently, this interest has intensified due to the development of methods for producing partially ionized plasmas in the laboratory. This has opened up large programs of experimental investigation and of practical application. In this paper we consider detailed statistical mechanical methods that explicitly treat the distribution over ionic species and their energy level structure. These detailed approaches are generally characterized as being in the ''chemical picture'' when a free energy expression is minimized or in the ''physical picture'' when the starting point is the grand canonical ensemble. 52 refs., 2 tabs

  2. Laser ionization of molecular clusters

    International Nuclear Information System (INIS)

    Desai, S.; Feigerle, C.S.

    1995-01-01

    Multiphoton ionization coupled with mass spectrometry was used to investigate molecular cluster distributions. Three examples will be discussed in this presentation. First, in studies of neat nitric oxide clusters, (NO) m , an interesting odd-even intensity alternation was observed and will be discussed in terms of electron-pairing considerations. In a separate study, the binary clusters comprising nitric oxide and methane preferentially form a stoichiometric cluster made up of repeating units of (NO) 2 CH 4 . These presumably represent a particularly strongly bound open-quotes van der Waalsclose quotes subunit. Finally, in similar studies of neat carbon disulfide clusters, (CS 2 ) m , additional photon absorption after the two-photon ionization step stimulates a series of intracluster ion-molecular reactions leading to formation of S m + and (CS) m + polymers, as well as intermediate species such as S m + (CS 2 ). This molecular cluster analogue of open-quotes laser snowclose quotes will be described in detail

  3. Calibration and consistency of results of an ionization-chamber secondary standard measuring system for activity

    International Nuclear Information System (INIS)

    Schrader, Heinrich

    2000-01-01

    Calibration in terms of activity of the ionization-chamber secondary standard measuring systems at the PTB is described. The measurement results of a Centronic IG12/A20, a Vinten ISOCAL IV and a radionuclide calibrator chamber for nuclear medicine applications are discussed, their energy-dependent efficiency curves established and the consistency checked using recently evaluated radionuclide decay data. Criteria for evaluating and transferring calibration factors (or efficiencies) are given

  4. Inner shell ionization accompanying nuclear collisions

    International Nuclear Information System (INIS)

    Sujkowski, Z.

    1987-01-01

    Selected phenomena leading to inner shell ionization and being of relevance for nuclear physics are discussed. The selection emphasizes the K-shell ionization induced in head-on collisions by fast light and medium-heavy ions. Cross-sections are reviewed. Effects of multiple inner shell ionization on the K X-ray spectra are illustrated with recent results. Implications for nuclear experiments are noted. Use of atomic observables as clocks for proton induced nuclear reactions is reviewed. Prospects for H.I. reactions are discussed. Preliminary experimental results on the direct K-shell ionization accompanying H.I. fusion reactions are presented. The post-collisional K-shell ionization due to internal conversion of γ-rays is discussed as the dominating contribution to the ionization for residues of dissipative nuclear reactions with Z > 40. Systematics of the corresponding K X-ray multiplicities are presented for rotational nuclei. These multiplicity values can be used for determining cross-sections for e.g. incomplete fusion reactions. Examples of such applications are given. Also discussed is the use of target K X-rays for normalization purposes and of the post-collisional, residue K X-rays in the studies of high spin phenomena. 96 references, 35 figures, 3 tables

  5. Absorbed dose measurement by using tissue equivalent ionization chamber (pair ionization chamber) in the Yayoi reactor

    International Nuclear Information System (INIS)

    Sasuga, N.; Okamura, K.; Terakado, T.; Mabuchi, Y.; Nakagawa, T.; Sukegawa, Toshio; Aizawa, C.; Saito, I.; Oka, Yoshiaki

    1998-01-01

    Each dose rate of neutron and gamma ray in the thermal column of the Yayoi reactor, in which an epithermal neutron field will be used for the boron neutron capture therapy, was measured by using a tissue equivalent ionization chamber and a graphite chamber. The tissue equivalent ionization chamber has some response to both neutron and gamma ray, but the graphite chamber has a few response to the neutron, so called pair ionization chamber method. The epithermal neutron fluxes of the thermal column were calculated by ANISN (one dimensional neutron-gamma transport code). A measured value for gamma dose rate by the pair ionization chamber agrees relevantly with a calculated result. For neutron dose rate, however, the measured value was too much small in comparison with the calculated result. The discrepancy between the measured value and the calculated result for neutron dose rate is discussed in detail in the report. (M. Suetake)

  6. IONIZATION OF EXTRASOLAR GIANT PLANET ATMOSPHERES

    International Nuclear Information System (INIS)

    Koskinen, Tommi T.; Cho, James Y-K.; Achilleos, Nicholas; Aylward, Alan D.

    2010-01-01

    Many extrasolar planets orbit close in and are subject to intense ionizing radiation from their host stars. Therefore, we expect them to have strong, and extended, ionospheres. Ionospheres are important because they modulate escape in the upper atmosphere and can modify circulation, as well as leave their signatures, in the lower atmosphere. In this paper, we evaluate the vertical location Z I and extent D I of the EUV ionization peak layer. We find that Z I ∼1-10 nbar-for a wide range of orbital distances (a = 0.047-1 AU) from the host star-and D I /H p ∼>15, where H p is the pressure scale height. At Z I , the plasma frequency is ∼80-450 MHz, depending on a. We also study global ion transport, and its dependence on a, using a three-dimensional thermosphere-ionosphere model. On tidally synchronized planets with weak intrinsic magnetic fields, our model shows only a small, but discernible, difference in electron density from the dayside to the nightside (∼9 x 10 13 m -3 to ∼2 x 10 12 m -3 , respectively) at Z I . On asynchronous planets, the distribution is essentially uniform. These results have consequences for hydrodynamic modeling of the atmospheres of close-in extrasolar giant planets.

  7. Investigations of the signal production in liquid-ionization-chambers by the passage of strongly ionizing particles and a now theoretical description of recombination

    International Nuclear Information System (INIS)

    Supper, R.

    1991-12-01

    Starting from the original Onsager-theory an extended theory is presented describing the recombination of charge carriers and of signal production in TMS (tetramethylsilane) liquid ionization chambers. The shielding by the impurities of the liquid is explicitly taken into account. By dedicated measurements various parameter dependencies of the theory are checked and the parameter values are experimentally determined. The studies comprise test procedures of the TMS chamber operation and are in context of a hadron calorimeter set up of the cosmic ray experiment KASCADE. (orig.) [de

  8. New results on strong-interaction effects in antiprotonic hydrogen

    International Nuclear Information System (INIS)

    Anagnostopoulos, D. F.; Augsburger, M.; Borchert, G.; Castelli, C.; Chatellard, D.; El-Khoury, P.; Egger, J.-P.; Gorke, H.; Gotta, D.; Hauser, P.; Indelicato, P.; Kirch, K.; Lenz, S.; Nelms, N.; Rashid, K.; Schult, O. W. B.; Siems, Th.; Simons, L. M.

    1999-01-01

    Lyman and Balmer transitions of antiprotonic hydrogen and deuterium have been measured at the Low-Energy Antiproton Ring LEAR at CERN in order to determine the strong interaction effects. The X-rays were detected using Charge-Coupled Devices (CCDs) and a reflection type crystal spectrometer. The results of the measurements support the meson-exchange models describing the medium and long range part of the nucleon-antinucleon interaction

  9. New ionization fractions for the lithium- and helium-like ionization stages of calcium and iron

    International Nuclear Information System (INIS)

    Doyle, J.G.; Raymond, J.C.

    1981-01-01

    The high resolution X-ray spectra of Ca XIX and Fe XXV observed during a solar flare on 1979 March 25 have been re-interpreted using new ionization fractions for Ca XVIII, Ca XIX, Fe XXIV and Fe XXV. These new calculations substantially change the interpretation of the spectra, implying the flare to be ionizing during the rise phase and recombining during the decay phase. The results favour the ECIP ionization rates over those of Lotz, though other interpretations are possible. (author)

  10. Secondary ionization processes in laser induced breakdown of electronegative gases

    International Nuclear Information System (INIS)

    Gamal Yosr, E.E.D.; Shafik, M.S.; Abdel-Moneim, H.M.

    1990-08-01

    This paper presents an investigation of the stepwise ionization processes which occur during the interaction of laser radiation with electronegative gases. Calculations are carried out adopting a modified version of the electron cascade model previously developed by Evans and Gamal. The modifications of the model are performed for the case of molecular oxygen to account for electron attachment losses. Particular attention is devoted to molecular oxygen at a pressure of 2.8 x 10 4 Torr irradiated by 10 ns pulse of Nd:YAG laser (λ=1.064 μm) at a peak intensity of 1.7x10 11 Wcm -2 . The calculations consider the effect of the secondary ionization processes on the electron energy distribution function and its parameters (evolution of the density of the excited molecules, electrons density as well as the electron mean energy during the laser flash). This analysis shows how the removal of slow electrons by attachment to oxygen molecules creates a strong competition between the stepwise ionization processes. These processes namely photoionization and collisional ionization deplete the electronic excited states and contribute eventually to the ionization growth rate in laser induced breakdown of electronegative gases. (author). 7 refs, 6 figs, 1 tab

  11. Strong effects of ionizing radiation from Chernobyl on mutation rates.

    Science.gov (United States)

    Møller, Anders Pape; Mousseau, Timothy A

    2015-02-10

    In this paper we use a meta-analysis to examine the relationship between radiation and mutation rates in Chernobyl across 45 published studies, covering 30 species. Overall effect size of radiation on mutation rates estimated as Pearson's product-moment correlation coefficient was very large (E = 0.67; 95% confidence intervals (CI) 0.59 to 0.73), accounting for 44.3% of the total variance in an unstructured random-effects model. Fail-safe calculations reflecting the number of unpublished null results needed to eliminate this average effect size showed the extreme robustness of this finding (Rosenberg's method: 4135 at p = 0.05). Indirect tests did not provide any evidence of publication bias. The effect of radiation on mutations varied among taxa, with plants showing a larger effect than animals. Humans were shown to have intermediate sensitivity of mutations to radiation compared to other species. Effect size did not decrease over time, providing no evidence for an improvement in environmental conditions. The surprisingly high mean effect size suggests a strong impact of radioactive contamination on individual fitness in current and future generations, with potentially significant population-level consequences, even beyond the area contaminated with radioactive material.

  12. Comparison among different CT ionization chambers

    International Nuclear Information System (INIS)

    Castro, Maysa C. de; Xavier, Marcos; Caldas, Linda V.E.

    2015-01-01

    The dosimetry in computed tomography (CT) is carried out by the use of a pencil type ionization-chamber, because it has a uniform response at all angles relative to the incident beam of radiation, which is essential for CT equipment since the X-ray tube executes a circular movement around the table during irradiation. The commercial ionization chamber used to perform quality control procedures of this kind of equipment has a length of the sensitive volume of 10 cm. In the Calibration Laboratory of Instruments (LCI) of the IPEN there were already developed some prototypes with small differences in construction, when compared to commercially available ionization chambers. They have been used in previous studies and showed results within internationally acceptable limits. The ionization chambers tested in this study present the sensitive volume lengths of 1 cm, 3 cm and 10 cm. The objective of this study was to present results on the stability test of the three homemade ionization chambers and a commercial chamber, as well to obtain the calibration coefficients for each of them in CT standard X radiation beams. The obtained results for both characterization tests are within the recommended limits, except for the homemade ionization chambers with sensitive volume lengths of 3 cm and 1 cm in the case of the stability test. (author)

  13. RILIS-ionized mercury and tellurium beams at ISOLDE CERN

    Energy Technology Data Exchange (ETDEWEB)

    Day Goodacre, T., E-mail: thomas.day.goodacre@cern.ch [CERN (Switzerland); Billowes, J. [The University of Manchester, School of Physics and Astronomy (United Kingdom); Chrysalidis, K. [CERN (Switzerland); Fedorov, D. V. [Petersburg Nuclear Physics Institute (Russian Federation); Fedosseev, V. N.; Marsh, B. A. [CERN (Switzerland); Molkanov, P. L. [Petersburg Nuclear Physics Institute (Russian Federation); Rossel, R. E.; Rothe, S.; Seiffert, C. [CERN (Switzerland); Wendt, K. D. A. [Johannes Gutenberg Universität, Institut für Physik (Germany)

    2017-11-15

    This paper presents the results of ionization scheme development for application at the ISOLDE Resonance Ionization Laser Ion Source (RILIS). Two new ionization schemes for mercury are presented: a three-step three-resonance ionization scheme, ionizing via an excitation to a Rydberg level and a three-step two-resonance ionization scheme, with a non-resonant final step to the ionization continuum that corresponded to a factor of four higher ionization efficiency. The efficiency of the optimal mercury ionization scheme was measured, together with the efficiency of a new three-step three resonance ionization scheme for tellurium. The efficiencies of the mercury and tellurium ionization schemes were determined to be 6 % and >18 % respectively.

  14. Dynamics of valence-shell electrons and nuclei probed by strong-field holography and rescattering

    Science.gov (United States)

    Walt, Samuel G.; Bhargava Ram, Niraghatam; Atala, Marcos; Shvetsov-Shilovski, Nikolay I; von Conta, Aaron; Baykusheva, Denitsa; Lein, Manfred; Wörner, Hans Jakob

    2017-01-01

    Strong-field photoelectron holography and laser-induced electron diffraction (LIED) are two powerful emerging methods for probing the ultrafast dynamics of molecules. However, both of them have remained restricted to static systems and to nuclear dynamics induced by strong-field ionization. Here we extend these promising methods to image purely electronic valence-shell dynamics in molecules using photoelectron holography. In the same experiment, we use LIED and photoelectron holography simultaneously, to observe coupled electronic-rotational dynamics taking place on similar timescales. These results offer perspectives for imaging ultrafast dynamics of molecules on femtosecond to attosecond timescales. PMID:28643771

  15. Photoionization effects in ionization fronts

    International Nuclear Information System (INIS)

    Arrayas, Manuel; Fontelos, Marco A; Trueba, Jose L

    2006-01-01

    In this paper we study the effects of photoionization processes on the propagation of both negative and positive ionization fronts in streamer discharge. We show that negative fronts accelerate in the presence of photoionization events. The appearance and propagation of positive ionization fronts travelling with constant velocity is explained as the result of the combined effects of photoionization and electron diffusion. The photoionization range plays an important role in the selection of the velocity of the ionization front as we show in this work

  16. Photoionization effects in ionization fronts

    Energy Technology Data Exchange (ETDEWEB)

    Arrayas, Manuel [Departamento de Electromagnetismo, Universidad Rey Juan Carlos, Tulipan s/n, 28933 Mostoles, Madrid (Spain); Fontelos, Marco A [Departamento de Matematicas, Instituto de Matematicas y Fisica Fundamental, Consejo Superior de Investigaciones CientIficas, C/Serrano 123, 28006 Madrid (Spain); Trueba, Jose L [Departamento de Electromagnetismo, Universidad Rey Juan Carlos, Tulipan s/n, 28933 Mostoles, Madrid (Spain)

    2006-12-21

    In this paper we study the effects of photoionization processes on the propagation of both negative and positive ionization fronts in streamer discharge. We show that negative fronts accelerate in the presence of photoionization events. The appearance and propagation of positive ionization fronts travelling with constant velocity is explained as the result of the combined effects of photoionization and electron diffusion. The photoionization range plays an important role in the selection of the velocity of the ionization front as we show in this work.

  17. Spectral measurements of electron temperature in nonequilibrium highly ionized He plasma

    International Nuclear Information System (INIS)

    Korshunov, O V; Chinnov, V F; Kavyrshin, D I; Ageev, A G

    2016-01-01

    It has been experimentally shown that highly ionized He arc plasma does not achieve local thermodynamic equilibrium expected for plasmas with electron concentrations above 1 × 10 16 cm -3 like argon plasma. We have found that the reason for this deviation is strong nonisotropy of plasma. Triple electron recombination with temperatures of 2.5-3 eV is almost absent. Charged particles move from the arc ( r = 1 mm) to chamber walls due to ambipolar diffusion creating ionization nonequilibrium over the excited states rendering Boltzmann distribution and Saha equation inapplicable for determining electron temperature. A method for determining electron temperature is suggested that is based on using the relative intensities of the atomic and ion lines. Its advantage lies in an energy gap between these lines’ states over 50 eV that reduces the influence of nonequilibrium on the result. This influence can be taken into account if the ionization energies of emitting states of atom and ion have close values. The suggested method can be expanded for any media including those with dimensional nonisotropy that have both atomic and ion lines in their emission spectra. (paper)

  18. Ionizing radiation test results for an automotive microcontroller on board the Schiaparelli Mars lander

    Science.gov (United States)

    Tapani Nikkanen, Timo; Hieta, Maria; Schmidt, Walter; Genzer, Maria; Haukka, Harri; Harri, Ari-Matti

    2016-04-01

    The Finnish Meteorological Institute (FMI) has delivered a pressure and a humidity instrument for the ESA ExoMars 2016 Schiaparelli lander mission. Schiaparelli is scheduled to launch towards Mars with the Trace Gas Orbiter on 14th of March 2016. The DREAMS-P (pressure) and DREAMS-H (Humidity) instruments are operated utilizing a novel FMI instrument controller design based on a commercial automotive microcontroller (MCU). A custom qualification program was implemented to qualify the MCU for the relevant launch, cruise and surface operations environment of a Mars lander. Resilience to ionizing radiation is one of the most critical requirements for a digital component operated in space or at planetary bodies. Thus, the expected Total Ionizing Dose accumulated by the MCU was determined and a sample of these components was exposed to a Co-60 gamma radiation source. Part of the samples was powered during the radiation exposure to include the effect of electrical biasing. All of the samples were verified to withstand the expected total ionizing dose with margin. The irradiated test samples were then radiated until failure to determine their ultimate TID.

  19. A liquid ionization chamber using tetramethylsilane

    International Nuclear Information System (INIS)

    Engler, J.; Keim, H.

    1983-12-01

    First results with a liquid ionization chamber using tetramethylsilane (TMS) are presented. A stack of iron plates was tested with cosmic ray muons and the charge output for minimum ionizing particles was measured. (orig.) [de

  20. New results on strong-interaction effects in antiprotonic hydrogen

    CERN Document Server

    Gotta, D; Augsburger, M A; Borchert, G L; Castelli, C M; Chatellard, D; El-Khoury, P; Egger, J P; Gorke, H; Hauser, P R; Indelicato, P J; Kirch, K; Lenz, S; Nelms, N; Rashid, K; Schult, O W B; Siems, T; Simons, L M

    1999-01-01

    Lyman and Balmer transitions of antiprotonic hydrogen and deuterium have been measured at the low-energy antiproton ring LEAR at CERN in order to determine the strong interaction effects. The X-rays were detected using charge-coupled devices (CCDs) and a reflection type crystal spectrometer. The results of the measurements support the meson-exchange models describing the medium and long range part of the nucleon-antinucleon interaction. (33 refs).

  1. Oscillator strength of partially ionized high-Z atom on Hartree-Fock Slater model

    International Nuclear Information System (INIS)

    Nakamura, S.; Nishikawa, T.; Takabe, H.; Mima, K.

    1991-01-01

    The Hartree-Fock Slater (HFS) model has been solved for the partially ionized gold ions generated when an intense laser light is irradiated on a gold foil target. The resultant energy levels are compared with those obtained by a simple screened hydrogenic model with l-splitting effect (SHML). It is shown that the energy levels are poorly model by SHML as the ionization level becomes higher. The resultant wave functions are used to evaluate oscillator strength of important line radiations and compared with those obtained by a simple model using hydrogenic wave functions. Its demonstrated that oscillator strength of the 4p-4d and 4d-4f lines are well modeled by the simple method, while the 4-5 transitions such as 4f-5g, 4d-5f, 4p-5d, and 4f-5p forming the so-called N-band emission are poorly modeled and HFS results less strong line emissions. (author)

  2. Ionization detection system for aerosols

    International Nuclear Information System (INIS)

    Jacobs, M.E.

    1977-01-01

    This invention relates to an improved smoke-detection system of the ionization-chamber type. In the preferred embodiment, the system utilizes a conventional detector head comprising a measuring ionization chamber, a reference ionization chamber, and a normally non-conductive gas triode for discharging when a threshold concentration of airborne particulates is present in the measuring chamber. The improved system utilizes a measuring ionization chamber which is modified to minimize false alarms and reductions in sensitivity resulting from changes in ambient temperature. In the preferred form of the modification, an annular radiation shield is mounted about the usual radiation source provided to effect ionization in the measuring chamber. The shield is supported by a bimetallic strip which flexes in response to changes in ambient temperature, moving the shield relative to the source so as to vary the radiative area of the source in a manner offsetting temperature-induced variations in the sensitivity of the chamber. 8 claims, 7 figures

  3. Ring magnetron ionizer

    International Nuclear Information System (INIS)

    Alessi, J.G.

    1986-01-01

    A ring magnetron D - charge exchange ionizer has been built and tested. An H - current of 500 μA was extracted with an estimated H 0 density in the ionizer of 10 12 cm -3 . This exceeds the performance of ionizers presently in use on polarized H - sources. The ionizer will soon be tested with a polarized atomic beam

  4. Strong-field Photoionization of Sputtered Neutral Molecules for Molecular Depth Profiling

    Science.gov (United States)

    Willingham, D; Brenes, D. A.; Wucher, A

    2009-01-01

    Molecular depth profiles of an organic thin film of guanine vapor deposited onto a Ag substrate are obtained using a 40 keV C60 cluster ion beam in conjunction with time-of-flight secondary ion mass spectrometric (ToF-SIMS) detection. Strong-field, femtosecond photoionization of intact guanine molecules is used to probe the neutral component of the profile for direct comparison with the secondary ion component. The ability to simultaneously acquire secondary ions and photoionized neutral molecules reveals new fundamental information about the factors that influence the properties of the depth profile. Results show that there is an increased ionization probability for protonated molecular ions within the first 10 nm due to the generation of free protons within the sample. Moreover, there is a 50% increase in fragment ion signal relative to steady state values 25 nm before reaching the guanine/Ag interface as a result of interfacial chemical damage accumulation. An altered layer thickness of 20 nm is observed as a consequence of ion beam induced chemical mixing. In general, we show that the neutral component of a molecular depth profile using the strong-field photoionization technique can be used to elucidate the effects of variations in ionization probability on the yield of molecular ions as well as to aid in obtaining accurate information about depth dependent chemical composition that cannot be extracted from TOF-SIMS data alone. PMID:20495665

  5. Results from the development of ionization detection systems for the DRAGON facility

    CERN Document Server

    Chen, A A

    2003-01-01

    We discuss the implementation of an ionization detection system for the focal plane of the DRAGON recoil mass separator. We report recent tests performed with stable beams to test the feasibility of such a system for use in measurements of radiative capture reactions in inverse kinematics with radioactive beams.

  6. Results from the development of ionization detection systems for the DRAGON facility

    International Nuclear Information System (INIS)

    Chen, Alan A.

    2003-01-01

    We discuss the implementation of an ionization detection system for the focal plane of the DRAGON recoil mass separator. We report recent tests performed with stable beams to test the feasibility of such a system for use in measurements of radiative capture reactions in inverse kinematics with radioactive beams

  7. Coulomb frustration of the multiphoton ionization of metallic clusters under intense EUV FEL evidenced by ion spectrometry

    International Nuclear Information System (INIS)

    Mazza, T; Devetta, M; Milani, P; Motomura, K; Liu, X-J; Fukuzawa, H; Yamada, A; Nagaya, K; Iwayama, H; Sugishima, A; Mizoguchi, Y; Saito, N; Coreno, M; Nagasono, M; Tono, K; Togashi, T; Kimura, H; Okunishi, M; Fennel, Th; Senba, Y

    2015-01-01

    Free electron laser light sources delivering high intensity pulses of short wavelength radiation are opening novel possibilities for the investigation of matter at the nanoscale and for the discovery and understanding of new physical processes occurring at the exotic transient states they make accessible. Strong ionization of atomic constituents of a nano-sized sample is a representative example of such processes and the understanding of ionization dynamics is crucial for a realistic description of the experiments. We report here on multiple ionization experiments on free clusters of titanium, a high cohesive energy metal. The time of flight ion spectra reveal a saturation of the cluster ionization at ∼10 16 photons per pulse per cm 2 . Our results also show a clear lack of any explosion process, opposite to what is observed for a rare-gas cluster under similar conditions. A simple and generalized multi-step ionization model including Coulomb frustration of the photoemission process effectively reproduces with a good agreement the main features of the experimental observation and points to an interpretation of the data involving a substantial energy deposition into the cluster through electronic system heating upon scattering events within photoemission. (paper)

  8. Theoretical basal Ca II fluxes for late-type stars: results from magnetic wave models with time-dependent ionization and multi-level radiation treatments

    Science.gov (United States)

    Fawzy, Diaa E.; Stȩpień, K.

    2018-03-01

    In the current study we present ab initio numerical computations of the generation and propagation of longitudinal waves in magnetic flux tubes embedded in the atmospheres of late-type stars. The interaction between convective turbulence and the magnetic structure is computed and the obtained longitudinal wave energy flux is used in a self-consistent manner to excite the small-scale magnetic flux tubes. In the current study we reduce the number of assumptions made in our previous studies by considering the full magnetic wave energy fluxes and spectra as well as time-dependent ionization (TDI) of hydrogen, employing multi-level Ca II atomic models, and taking into account departures from local thermodynamic equilibrium. Our models employ the recently confirmed value of the mixing-length parameter α=1.8. Regions with strong magnetic fields (magnetic filling factors of up to 50%) are also considered in the current study. The computed Ca II emission fluxes show a strong dependence on the magnetic filling factors, and the effect of time-dependent ionization (TDI) turns out to be very important in the atmospheres of late-type stars heated by acoustic and magnetic waves. The emitted Ca II fluxes with TDI included into the model are decreased by factors that range from 1.4 to 5.5 for G0V and M0V stars, respectively, compared to models that do not consider TDI. The results of our computations are compared with observations. Excellent agreement between the observed and predicted basal flux is obtained. The predicted trend of Ca II emission flux with magnetic filling factor and stellar surface temperature also agrees well with the observations but the calculated maximum fluxes for stars of different spectral types are about two times lower than observations. Though the longitudinal MHD waves considered here are important for chromosphere heating in high activity stars, additional heating mechanism(s) are apparently present.

  9. Comparison between radiological protection against ionizing radiation and non-ionizing radiation

    International Nuclear Information System (INIS)

    Jammet, H.P.

    1988-01-01

    The comparison of doctrines concerning protection against ionizing and non-ionizing radiation is a difficult task, because of the many areas in which it is applied. Radiological pollution has grown during the century, but its evolution has not been concomitant. This has resulted in a distortion that can be identified in the successive steps of the evaluation and protection against such radiation. For a better understanding, this discussion deals with the differences in interaction with matter and the induction of the related risks, on the varieties of protection systems and monitoring procedures

  10. Surface-ionization field mass-spectrometry studies of nonequilibrium surface ionization

    International Nuclear Information System (INIS)

    Blashenkov, Nikolai M; Lavrent'ev, Gennadii Ya

    2007-01-01

    The ionization of polyatomic molecules on tungsten and tungsten oxide surfaces is considered for quasiequilibrium or essentially nonequilibrium conditions (in the latter case, the term nonequilibrium surface ionization is used for adsorbate ionization). Heterogeneous reactions are supposed to proceed through monomolecular decay of polyatomic molecules or fragments of multimolecular complexes. The nonequilibrium nature of these reactions is established. The dependences of the current density of disordered ions on the surface temperature, electric field strength, and ionized particle energy distribution are obtained in analytical form. Heterogeneous dissociation energies, the ionization potentials of radicals, and the magnitude of reaction departure from equilibrium are determined from experimental data, as are energy exchange times between reaction products and surfaces, the number of molecules in molecular complexes, and the number of effective degrees of freedom in molecules and complexes. In collecting the data a new technique relying on surface-ionization field mass-spectrometry was applied. (instruments and methods of investigation)

  11. arXiv Recent results from the strong interactions program of NA61/SHINE

    CERN Document Server

    Pulawski, Szymon

    2017-01-01

    The NA61/SHINE experiment studies hadron production in hadron+hadron, hadron+nucleus and nucleus+nucleus collisions. The strong interactions program has two main purposes: study the properties of the onset of deconfinement and search for the signatures of the critical point of strongly interacting matter. This aim is pursued by performing a two-dimensional scan of the phase diagram by varying the energy/momentum (13A-158A GeV/c) and the system size (p+p, Be+Be, Ar+Sc, Xe+La) of the collisions. This publication reviews recent results from p+p, Be+Be and Ar+Sc interactions. Measured particle spectra are discussed and compared to NA49 results from Pb+Pb collisions. The results illustrate the progress towards scanning the phase diagram of strongly interacting matter.

  12. Estimation of the contribution of ionization and excitation to the lethal effect of ionizing radiation

    International Nuclear Information System (INIS)

    Petin, V.G.; Komarov, V.P.

    1982-01-01

    A simple theoretical model is proposed for estimating the differential contribution of ionization and excitation to the lethal effect of ionizing radiation. Numerical results were obtained on the basis of published experimental data on the ability of bacterial cells Escherichia coli to undergo photoreactivation of radiation-induced damage. It was shown that inactivation by excitation may be highly significant for UV-hypersensitive cells capable of photoreactivation; inactivation by excitation increased with the energy of ionizing radiation and the volume of irradiated suspensions. The data are in qualitative agreement with the assumption of a possible contribution of the UV-component of Cerenkov radiation to the formation of excitations responsible for the lethal effect and the phenomenon of photoreactivation after ionizing radiation. Some predictions from the model are discussed. (orig.)

  13. Laser-induced ionization of Na vapor

    International Nuclear Information System (INIS)

    Wu, R.C.Y.; Judge, D.L.; Roussel, F.; Carre, B.; Breger, P.; Spiess, G.

    1982-01-01

    The production of Na 2 + ions by off-resonant laser excitation in the 5800-6200A region mainly results from two-photon absorption by the Na 2 molecule to highly excited gerade states followed by (a) direct ionization by absorbing a third photon or (b) coupling to the molecular Na 2 D 1 PIμ Rydberg state which is subsequently ionized by absorbing a third photon. This mechanism, i.e., a two-photon resonance three photon ionization process, explains a recent experimental observation of Roussel et al. It is suggested that the very same mechanism is also responsible for a similar observation reported by Polak-Dingels et al in their work using two crossed Na beams. In the latter two studies the laser-induced associative ionization processes were reported to be responsible for producing the Na 2 + ion. From the ratio of molecular to atomic concentration in the crossed beam experiment of Polak-Dingels et al we estimate that the cross section for producing Na 2 + through laser-induced associative ionization is at least four orders of magnitude smaller than ionization through the two-photon resonance three photon ionization process in Na 2 molecules

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

    KAUST Repository

    Efimov, D K; Miculis, K; Bezuglov, N N; Ekers, Aigars

    2016-01-01

    with which feature autoionization widths that are enhanced by several orders of magnitude compared to that of two atoms in the initial laser-excited state n 0. We also show that in the high-density regime of cold Rydberg gas experiments the ionization rate

  15. Space-charge-limited ion flow through an ionizing neutral layer

    International Nuclear Information System (INIS)

    Duvall, R.E.; Litwin, C.; Maron, Y.

    1993-01-01

    Space-charge-limited ion flow through an ionizing layer of neutral atoms is studied. The ion flow is between two parallel conducting plates (anode and cathode) with an externally applied voltage between them. An expanding layer of neutral atoms is adjacent to the anode surface, extending a finite distance into the anode--cathode gap. All ions originate either from the anode surface or from the ionization of neutrals; electrons originate only from ionization. Electrons are strongly magnetized by an externally applied, time-independent direct current (dc) magnetic field directed across the ion flow. The ions are unmagnetized, all motion being perpendicular to the conducting plates. Two different models of the anode layer were used to analyze this problem: a multifluid steady-state model and a single fluid time-dependent model. From both models it was found that the anode surface becomes shielded after the ion flux from the ionizing layer becomes larger than the space-charge-limited flux of the reduced gap between the neutral layer and cathode. Comparison was made between the time-dependent model and results from magnetically insulated ion beam diode (MID) experiments. Using an initial areal density of neutral hydrogen and carbon equal to the final observed electron areal density, comparison was made between calculated plasma shielding times and upper bounds on the shielding time observed in experiments. It was found that a layer of neutral hydrogen must contain a minimum of 15% carbon (by number density) to explain the rapid electric field screening observed in experiments

  16. Helium atoms and molecules in strong magnetic fields

    Science.gov (United States)

    Mori, K.

    Recent theoretical studies have shown that the neutron star surface may be composed of helium or heavier elements as hydrogen may be quickly depleted by diffuse nuclear burning Chang Bildsten However while Hydrogen atmospheres have been studied in great details atomic data for helium is available only for He ion Pavlov Bezchastnov 2005 We performed Hartree-Fock type calculation for Helium atom and molecules and computed their binding ionization and dissociation energies in strong magnetic fields B sim10 12 -- 10 15 G We will present ionization balance of Helium atmospheres at typical magnetic field strengths and temperatures to radio-quiet neutron stars and AXPs We will also discuss several implications of helium atmosphere to X-ray data of isolated neutron stars focusing on the detected spectral features

  17. Down syndrome and ionizing radiation.

    Science.gov (United States)

    Verger, P

    1997-12-01

    This review examines the epidemiologic and experimental studies into the possible role ionizing radiation might play in Down Syndrome (trisomy 21). It is prompted by a report of a temporal cluster of cases of this chromosomal disorder observed in West Berlin exactly 9 mo after the radioactive cloud from Chernobyl passed. In approximately 90% of cases, Down Syndrome is due to the nondisjunction of chromosome 21, most often in the oocyte, which may be exposed to ionizing radiation during two separate periods: before the completion of the first meiosis or around the time of ovulation. Most epidemiologic studies into trisomies and exposure to ionizing radiation examine only the first period; the Chernobyl cluster is related to the second. Analysis of these epidemiologic results indicates that the possibility that ionizing radiation might be a risk factor in Down Syndrome cannot be excluded. The experimental results, although sometimes contradictory, demonstrate that irradiation may induce nondisjunction in oogenesis and spermatogenesis; they cannot, however, be easily extrapolated to humans. The weaknesses of epidemiologic studies into the risk factors for Down Syndrome at birth (especially the failure to take into account the trisomy cases leading to spontaneous abortion) are discussed. We envisage the utility and feasibility of new studies, in particular among women exposed to prolonged or repeated artificially-produced ionizing radiation.

  18. Threshold law for electron impact ionization in the model of Temkin and Poet

    International Nuclear Information System (INIS)

    Macek, J.H.

    1996-01-01

    The angle-Sturmian theory is used to derive the threshold law for ionization of atomic hydrogen by electron impact in the model of Temkin and Poet. In this model, the exact electron-electron interaction is replaced by its monopole term. As for Wannier's theory with the real interaction, ionization occurs only for electrons that start out nearly equidistant from the proton. Because there is a high propensity for one electron to be captured into a bound state, ionization is strongly suppressed, giving rise to a threshold law of the form σ ∝ exp[-aE -1/6 + bE 1/6 ], where a and b are constants. The exponential law appears to be the quantal counterpart of the classical offset of the ionization threshold. Relative energy distribution are computed and found to favor configurations with unequal energy sharing

  19. Electronegative Plasma Equilibria with Spatially-Varying Ionization

    Science.gov (United States)

    Lieberman, M. A.; Kawamura, E.; Lichtenberg, A. J.

    2012-10-01

    Electronegative inductive discharges in higher pressure ranges typically exhibit localized ionization near the coil structure, with decay of the ionization into the central discharge. We use a two-dimensional fluid code [1] with chlorine feedstock to determine the spatial profiles of the plasma parameters in a cylindrical transformer-coupled plasma device excited by a planar coil. To compare with one-dimensional (1D) analytic modeling, the results are area-averaged. The ionization is found to decay roughly exponentially along the axial direction, allowing the ansatz of an exponentially decaying ionization to be used in a 1D computational model. The model captures the main features of the axial variations of the area-averaged fluid simulation, indicating that the main diffusion mechanisms act along the axial direction. A simple analytic global discharge model is developed, accounting for the asymmetric density and ionization profiles. The global model gives the scalings with power and pressure of volume-averaged densities, electron temperature, and ionization decay rate, also in reasonable agreement with the scalings obtained by averaging the simulation results. [4pt] [1] E. Kawamura, D.B. Graves, and M.A. Lieberman, Plasma Sources Sci. Technol. 20, 035009 (2012)

  20. Measurement of indoor background ionizing radiation in some ...

    African Journals Online (AJOL)

    Certain types of building materials are known to be radioactive. Exposure to indoor ionizing radiation like exposure to any other type of ionizing radiation results in critical health challenges. Measurement of the background ionizing radiation profile within the Chemistry Research Laboratory and Physics Laboratory III all of ...

  1. Progress on untargeted effects of ionizing irradiation

    International Nuclear Information System (INIS)

    Liu Jing; Chen Jihong; Li Wenjian

    2010-01-01

    The side effect of ionizing irradiation has been paid more attention with its widely using in tumor treating and mutation breeding. In recent years, untargeted effects induced by ionizing irradiation have become a hotspot of radiobiology. Here, according to reported results, we reviewed the types (genomic instability, bystander effect and adaptive response) and mechanisms of untargeted effects of ionizing irradiation in this paper. (authors)

  2. Ionic rotational branching ratios in resonant enhanced multiphoton ionization of NO via the A 2Σ+(3sσ) and D 2Σ+(3pσ) states

    International Nuclear Information System (INIS)

    Rudolph, H.; Dixit, S.N.; McKoy, V.; Huo, W.M.

    1988-01-01

    We present the results of ab initio calculations of the ionic rotational branching ratios in NO for a (1+1) REMPI (resonant enhanced multiphoton ionization) via the A 2 Σ + (3sσ) state and a (2+1) REMPI via the D 2 Σ + (3pσ) state. Despite the atomic-like character of the bound 3sσ and 3pσ orbitals in these resonant states, the photoelectron continuum exhibits strong l mixing. The selection rule ΔN+l = odd (ΔNequivalentN/sub +/-N/sub i/) implies that the peaks in the photoelectron spectrum corresponding to ΔN = odd ( +- 1, +- 3) are sensitive to even partial waves while those corresponding to even ΔN probe the odd partial waves in the photoelectron continuum. Recent experimental high resolution photoelectron studies have shown a strong ΔN = 0 peak for ionization via the A 2 Σ + and the D 2 Σ + states, indicating a dominance of odd-l partial waves. While this seems natural for ionization out of the 3sσ orbital, it is quite anomalous for 3pσ ionization. Based on extensive bound calculations, Viswanathan et al. [J. Phys. Chem. 90, 5078 (1986)] attribute this anomaly to a strong l mixing in the electronic continuum caused by the nonspherical molecular potential

  3. Discovery of Low-ionization Envelopes in the Planetary Nebula NGC 5189: Spatially-resolved Diagnostics from HST Observations

    Science.gov (United States)

    Danehkar, Ashkbiz; Karovska, Margarita; Maksym, Walter Peter; Montez, Rodolfo

    2018-01-01

    The planetary nebula NGC 5189 shows one of the most spectacular morphological structures among planetary nebulae with [WR]-type central stars. Using high-angular resolution HST/WFC3 imaging, we discovered inner, low-ionization structures within a region of 0.3 parsec × 0.2 parsec around the central binary system. We used Hα, [O III], and [S II] emission line images to construct line-ratio diagnostic maps, which allowed us to spatially resolve two distinct low-ionization envelopes within the inner, ionized gaseous environment, extending over a distance of 0.15 pc from the central binary. Both the low-ionization envelopes appear to be expanding along a NE to SW symmetric axis. The SW envelope appears smaller than its NE counterpart. Our diagnostic maps show that highly-ionized gas surrounds these low-ionization envelopes, which also include filamentary and clumpy structures. These envelopes could be a result of a powerful outburst from the central interacting binary, when one of the companions (now a [WR] star) was in its AGB evolutionary stage, with a strong mass-loss generating dense circumstellar shells. Dense material ejected from the progenitor AGB star is likely heated up as it propagates along a symmetric axis into the previously expelled low-density material. Our new diagnostic methodology is a powerful tool for high-angular resolution mapping of low-ionization structures in other planetary nebulae with complex structures possibly caused by past outbursts from their progenitors.

  4. Velocity map imaging of attosecond and femtosecond dynamics in atoms and small molecules in strong laser fields

    International Nuclear Information System (INIS)

    Kling, M.F.; Ni, Yongfeng; Lepine, F.; Khan, J.I.; Vrakking, M.J.J.; Johnsson, P.; Remetter, T.; Varju, K.; Gustafsson, E.; L'Huillier, A.; Lopez-Martens, R.; Boutu, W.

    2005-01-01

    Full text: In the past decade, the dynamics of atomic and small molecular systems in strong laser fields has received enormous attention, but was mainly studied with femtosecond laser fields. We report on first applications of attosecond extreme ultraviolet (XUV) pulse trains (APTs) from high-order harmonic generation (HHG) for the study of atomic and molecular electron and ion dynamics in strong laser fields utilizing the Velocity Map Imaging Technique. The APTs were generated in argon from harmonics 13 to 35 of a 35 fs Ti:sapphire laser, and spatially and temporally overlapped with an intense IR laser field (up to 5x10 13 W/cm 2 ) in the interaction region of a Velocity Map Imaging (VMI) machine. In the VMI setup, electrons and ions that were created at the crossing point of the laser fields and an atomic or molecular beam were accelerated in a dc-electric field towards a two-dimensional position-sensitive detector, allowing to reconstruct the full initial three-dimensional velocity distribution. The poster will focus on results that were obtained for argon atoms. We recorded the velocity distribution of electron wave packets that were strongly driven in the IR laser field after their generation in Ar via single-photon ionization by attosecond XUV pulses. The 3D evolution of the electron wave packets was observed on an attosecond timescale. In addition to earlier experiments with APTs using a magnetic bottle electron time-of-flight spectrometers and with single attosecond pulses, the angular dependence of the electrons kinetic energies can give further insight into the details of the dynamics. Initial results that were obtained for molecular systems like H 2 , D 2 , N 2 , and CO 2 using the same powerful approach will be highlighted as well. We will show, that detailed insight into the dynamics of these systems in strong laser fields can be obtained (e.g. on the alignment, above-threshold ionization, direct vs. sequential two-photon ionization, dissociation, and

  5. Synthesis of refractory organic matter in the ionized gas phase of the solar nebula.

    Science.gov (United States)

    Kuga, Maïa; Marty, Bernard; Marrocchi, Yves; Tissandier, Laurent

    2015-06-09

    In the nascent solar system, primitive organic matter was a major contributor of volatile elements to planetary bodies, and could have played a key role in the development of the biosphere. However, the origin of primitive organics is poorly understood. Most scenarios advocate cold synthesis in the interstellar medium or in the outer solar system. Here, we report the synthesis of solid organics under ionizing conditions in a plasma setup from gas mixtures (H2(O)-CO-N2-noble gases) reminiscent of the protosolar nebula composition. Ionization of the gas phase was achieved at temperatures up to 1,000 K. Synthesized solid compounds share chemical and structural features with chondritic organics, and noble gases trapped during the experiments reproduce the elemental and isotopic fractionations observed in primitive organics. These results strongly suggest that both the formation of chondritic refractory organics and the trapping of noble gases took place simultaneously in the ionized areas of the protoplanetary disk, via photon- and/or electron-driven reactions and processing. Thus, synthesis of primitive organics might not have required a cold environment and could have occurred anywhere the disk is ionized, including in its warm regions. This scenario also supports N2 photodissociation as the cause of the large nitrogen isotopic range in the solar system.

  6. Ionization

    International Nuclear Information System (INIS)

    2002-01-01

    This document reprints the text of the French by-law from January 8, 2002 relative to the approval and to the controls and verifications of facilities devoted to the ionizing of food products for human beings and animals. The by-law imposes the operators of such facilities to perform measurements and dosimetric verifications all along the ionization process. (J.S.)

  7. Influence of gas mixture and primary ionization on the performance of limit streamer mode tubes

    International Nuclear Information System (INIS)

    An Jigang; Anderson, K.J.; Merritt, F.S.; Oreglia, M.; Pilcher, J.E.; Possoz, A.; Schappert, W.; Chicago Univ., IL

    1988-01-01

    We report a study of the dependence of limited streamer mode operation on gas composition. Results are given for the plateau onset voltage, plateau length, charge versus voltage, charge spectra and pulse width for various fractions of (Ar, CO 2 , pentane) and (Ar, isobutane). In addition, a series of argon-free strong quenching gas mixtures has been studied which have very attractive characteristics. Chamber lifetime tests for these are also reported. As part of a study of the nature of the limited streamer mode mechanism, the response to X-rays and minimum ionizing particles are compared and differences noted. The character of the primary ionization is found to have a clear effect on the chamber response even in the streamer region. (orig.)

  8. Two-step laser ionization schemes for in-gas laser ionization and spectroscopy of radioactive isotopesa

    OpenAIRE

    Kudryavtsev, Yuri; Ferrer, Rafael; Huyse, Mark; Van den Bergh, Paul; Van Duppen, Piet; Vermeeren, L.

    2014-01-01

    The in-gas laser ionization and spectroscopy technique has been developed at the Leuven isotope separator on-line facility for the production and in-source laser spectroscopy studies of short-lived radioactive isotopes. In this article, results from a study to identify efficient optical schemes for the two-step resonance laser ionization of 18 elements are presented. © 2013 AIP Publishing LLC.

  9. Ionizing radiation effects on floating gates

    International Nuclear Information System (INIS)

    Cellere, G.; Paccagnella, A.; Visconti, A.; Bonanomi, M.

    2004-01-01

    Floating gate (FG) memories, and in particular Flash, are the dominant among modern nonvolatile memory technologies. Their performance under ionizing radiation was traditionally studied for the use in space, but has become of general interest in recent years. We are showing results on the charge loss from programmed FG arrays after 10 keV x-rays exposure. Exposure to ionizing radiation results in progressive discharge of the FG. More advanced devices, featuring smaller FG, are less sensitive to ionizing radiation that older ones. The reason is identified in the photoemission of electrons from FG, since at high doses it dominates over charge loss deriving from electron/hole pairs generation in the oxides

  10. Possibilities to reduce the effect of ionizing radiation by interaction of two types of radiation into a matter: ionized and non-ionized radiation

    International Nuclear Information System (INIS)

    Tanvir

    2007-01-01

    Full text: At present it has been accepted that ionized radiation can cause biological effects on the human body and the only way of preventing this effect, is by shielding the source of radiation by absorbing materials. On the other hand, the technology of non-ionizing radiation is upgraded. The canalization of radiation through the wave-guide based structures and optical fiber is well established. This reminds us that passing through benzene non-ionized radiation give the 'Raman' effect, which can ensure the secondary generation of non-ionized radiation with the wave length of nanometer and so far. These types of non-ionized radiation can easily be correlated with the gamma radiation, which is ionized. We know that high-energized photon usually interacts with matter and reduces its energy to the matter and generate electro-magnetic waves into the molecules of the matter. It is also well known that through the wave-guide based structures and optical fiber; the path of energy distribution of photon is likely to be optical energetic modes. If two types of photon from two types of radiation (ionized and non-ionized) interact with matter and pass through the optical fiber, they can generate optical modes with various wavelengths and phase velocities. With 'Raman' effect we can generate secondary electromagnetic waves of nanometer; as well as optical modes into the optical fiber. These optical modes from two types of radiation with various phase velocities, having the similar wavelength, can decrease or accelerate some modes. On the view of signal distribution, we can assume that if two similar signals pass through the circuit with phase difference 180P 0 P, then the result posses no signal. We are also reminded that photon of γ - radiation can spread from 0 deg. to 180 deg. C, where the 'Compton' loss of radiation is minimum. In view of the electro-magnetic theory of Maxwell we can assume the energetic field of optical modes, which are generated into the optical

  11. Electron ionization and the Compton effect in double ionization of helium

    International Nuclear Information System (INIS)

    Samson, J.

    1994-01-01

    The author discusses ionization phenomena in helium, both photoionization and electron ionization. In particular he compares double ionization cross sections with total cross sections, as a function of electron energy, and photon energy. Data is discussed over the energy range up to 10 keV

  12. Determination of the first ionization potential of actinides by resonance ionization mass spectroscopy

    International Nuclear Information System (INIS)

    Koehler, S.; Albus, F.; Dibenberger, R.; Erdmann, N.; Funk, H.; Hasse, H.; Herrmann, G.; Huber, G.; Kluge, H.; Nunnemann, M.; Passler, G.; Rao, P.M.; Riegel, J.; Trautmann, N.; Urban, F.

    1995-01-01

    Resonance ionization mass spectroscopy (RIMS) is used for the precise determination of the first ionization potential of transuranium elements. The first ionization potentials (IP) of americium and curium have been measured for the first time to IP Am =5.9738(2) and IP Cm =5.9913(8) eV, respectively, using only 10 12 atoms of 243 Am and 248 Cm. The same technique was applied to thorium, neptunium, and plutonium yielding IP T H =6.3067(2), IP N P =6.2655(2), and IP Pu =6.0257(8) eV. The good agreement of our results with the literature data proves the precision of the method which was additionally confirmed by the analysis of Rydberg seris of americium measured by RIMS. copyright American Institute of Physics 1995

  13. Apparatus for reading and recharging condenser ionization chambers

    International Nuclear Information System (INIS)

    McCall, R.C.

    1977-01-01

    A metering circuit for a condenser ionization chamber is disclosed for simultaneously recharging the ionization chamber and reading out the amount of charge required to recharge the chamber. During the recharging process, the amount of charge necessary to recharge the ionization chamber capacitor is placed on an integrating capacitor in the metering apparatus. The resultant voltage across the integrating capacitor is a measure of the radiation to which the ionization chamber was exposed. 9 claims, 1 figure

  14. Contribution to the study of molecular multi-ionisation and multifragmentation in strong laser field

    International Nuclear Information System (INIS)

    Hering, P.

    1999-12-01

    Molecular multi-ionization in strong laser field is studied using different experimental and theoretical techniques. In the 10 13 -10 16 W/cm 2 laser intensity range, the strong non-linear laser-molecule coupling allows the absorption of energies necessary to the ejection of valence electrons. The double ionization is characterized by the production of doubly charged molecular ions and by charge separation channels such as A + + B + . For molecular charge states greater than two, the multi-ionization dynamics study is based on the observables due to the multifragmentation, which are the fragments charge states and initial momenta. For strong intensities in the 1015-1016 w/cm 2 range, the multicharged atomic ions production efficiency depends on the initial electronic density localization of the molecule. For intensities less than 5 x 10 14 w/cm 2 , double ionization leads to the simultaneous emission of two electrons from the molecule. The two-missing electrons fragmentation channels appear at internuclear equilibrium distance following the Franck-Condon principle. For more than two-missing electrons channels, the internuclear distance of excitation is more difficult to determine. However the reported different experiments show that the multifragmentation dynamics is independent of the electronic emission dynamics. The theoretical approach is based on the Thomas-Fermi equations and allows a non-perturbative description of the laser-molecule coupling. The calculated fragmentation kinetic energies are smaller than the coulombic repulsion energies calculated at the internuclear equilibrium distance because of an electronic screening effect. This model reproduce the experimental fragmentation 'energy releases obtained experimentally for molecules such as N 2 , CO 2 or N 2 O. (author)

  15. Behavior of Rydberg atoms at surfaces: energy level shifts and ionization

    Energy Technology Data Exchange (ETDEWEB)

    Dunning, F.B. E-mail: fbd@rice.edu; Dunham, H.R.; Oubre, C.; Nordlander, P

    2003-04-01

    The ionization of xenon atoms excited to the extreme red and blue states in high-lying Xe(n) Stark manifolds at a metal surface is investigated. The data show that, despite their very different initial spatial characteristics, the extreme members of a given Stark manifold ionize at similar atom/surface separations. This is explained, with the aid of complex scaling calculations, in terms of the strong perturbations in the energies and structure of the atomic states induced by the presence of the surface which lead to avoided crossings between neighboring levels as the surface is approached.

  16. Behavior of Rydberg atoms at surfaces: energy level shifts and ionization

    CERN Document Server

    Dunning, F B; Oubre, C D; Nordlander, P

    2003-01-01

    The ionization of xenon atoms excited to the extreme red and blue states in high-lying Xe(n) Stark manifolds at a metal surface is investigated. The data show that, despite their very different initial spatial characteristics, the extreme members of a given Stark manifold ionize at similar atom/surface separations. This is explained, with the aid of complex scaling calculations, in terms of the strong perturbations in the energies and structure of the atomic states induced by the presence of the surface which lead to avoided crossings between neighboring levels as the surface is approached.

  17. Surface ionization mass spectrometry of opiates

    International Nuclear Information System (INIS)

    Usmanov, D.T.

    2009-07-01

    Key words: surface ionization, adsorption, heterogeneous reactions, surface ionization mass spectrometry, thermodesorption surface ionization spectroscopy, thermoemitter, opiates, extracts of biosamples. Subjects of study. The mass - spectrometric study of thermal - ion emission: surface ionization of opiates by on the surface of oxidized refractory metals. Purpose of work is to establish the regularities of surface ionization (SI) of multi-atomic molecule opiates and their mixtures develop the scientific base of SI methods for high sensitive and selective detection and analysis of these substances in the different objects, including biosamples. Methods of study: surface ionization mass spectrometry, thermodesorption surface ionization spectroscopy. The results obtained and their novelty. For the first time, SI of molecule opiates on the oxidized tungsten surface has been studied and their SI mass-spectra and temperature dependences of ion currents have been obtained, the characteristic heterogeneous reactions of an adsorbed molecules and the channels of monomolecular decays vibrationally-excited ions on their way in mass-spectrometry have been revealed, sublimation energy has been defined, the activation energy of E act , of these decays has been estimated for given period of time. Additivity of the SI mass-spectra of opiate mixtures of has been established under conditions of joint opiate adsorption. High selectivity of SI allows the extracts of biosamples to be analyzed without their preliminary chromatographic separation. The opiates are ionized by SI with high efficiency (from 34 C/mol to 112 C/mol), which provides high sensitivity of opiate detection by SI/MS and APTDSIS methods from - 10 -11 g in the samples under analysis. Practical value. The results of these studies create the scientific base for novel SI methods of high sensitive detection and analysis of the trace amounts of opiates in complicated mixtures, including biosamples without their preliminary

  18. Lithium atoms on helium nanodroplets: Rydberg series and ionization dynamics

    Science.gov (United States)

    Lackner, Florian; Krois, Günter; Ernst, Wolfgang E.

    2017-11-01

    The electronic excitation spectrum of lithium atoms residing on the surface of helium nanodroplets is presented and analyzed employing a Rydberg-Ritz approach. Utilizing resonant two-photon ionization spectroscopy, two different Rydberg series have been identified: one assigned to the nS(Σ) series and the other with predominantly nP(Π) character. For high Rydberg states, which have been resolved up to n = 13, the surrounding helium effectively screens the valence electron from the Li ion core, as indicated by the apparent red-shift of Li transitions and lowered quantum defects on the droplet with respect to their free atom counterparts. For low n states, the screening effect is weakened and the prevailing repulsive interaction gives rise to strongly broadened and blue-shifted transitions. The red-shifts originate from the polarization of nearby He atoms by the positive Li ion core. As a consequence of this effect, the ionization threshold is lowered by 116 ± 10 cm-1 for Li on helium droplets with a radius of about 40 Å. Upon single-photon ionization, heavy complexes corresponding to Li ions attached to intact helium droplets are detected. We conclude that ionization close to the on-droplet ionization threshold triggers a dynamic process in which the Li ion core undergoes a transition from a surface site into the droplet.

  19. A novel magnet focusing plate for matrix-assisted laser desorption/ionization analysis of magnetic bead-bound analytes.

    Science.gov (United States)

    Gode, David; Volmer, Dietrich A

    2013-05-15

    Magnetic beads are often used for serum profiling of peptide and protein biomarkers. In these assays, the bead-bound analytes are eluted from the beads prior to mass spectrometric analysis. This study describes a novel matrix-assisted laser desorption/ionization (MALDI) technique for direct application and focusing of magnetic beads to MALDI plates by means of dedicated micro-magnets as sample spots. Custom-made MALDI plates with magnetic focusing spots were made using small nickel-coated neodymium micro-magnets integrated into a stainless steel plate in a 16 × 24 (384) pattern. For demonstrating the proof-of-concept, commercial C-18 magnetic beads were used for the extraction of a test compound (reserpine) from aqueous solution. Experiments were conducted to study focusing abilities, the required laser energies, the influence of a matrix compound, dispensing techniques, solvent choice and the amount of magnetic beads. Dispensing the magnetic beads onto the micro-magnet sample spots resulted in immediate and strong binding to the magnetic surface. Light microscope images illustrated the homogeneous distribution of beads across the surfaces of the magnets, when the entire sample volume containing the beads was pipetted onto the surface. Subsequent MALDI analysis of the bead-bound analyte demonstrated excellent and reproducible ionization yields. The surface-assisted laser desorption/ionization (SALDI) properties of the strongly light-absorbing γ-Fe2O3-based beads resulted in similar ionization efficiencies to those obtained from experiments with an additional MALDI matrix compound. This feasibility study successfully demonstrated the magnetic focusing abilities for magnetic bead-bound analytes on a novel MALDI plate containing small micro-magnets as sample spots. One of the key advantages of this integrated approach is that no elution steps from magnetic beads were required during analyses compared with conventional bead experiments. Copyright © 2013 John Wiley

  20. Modeling long recovery early events (LOREs) produced by lightning-induced ionization of the nighttime upper mesosphere

    Science.gov (United States)

    Kotovsky, D. A.; Moore, R. C.

    2017-07-01

    We present results of a cylindrically symmetric, coupled electrodynamic, and photochemical model which simulates diffuse ionization of the middle atmosphere induced by strong lightning discharges (peak currents >150 kA). Scattering of subionospherically propagating, very low frequency radio waves is then evaluated using the Long-Wave Propagation Capability code. Some modeled sprite halos exhibit continued electron density growth up to timescales of seconds due to O- detachment, though it is not yet clear how this might relate to the slower onset durations (>20 ms) of some early VLF events. Modeled electron density enhancements in sprite halos, capable of strong VLF scattering, can persist for long periods of time (greater than hundreds of seconds) even at lower altitudes where their recovery is initially controlled by fast attachment processes. Consequently, our modeling results indicate that both typical recovery (20 to 240 s) and long recovery (LOREs, >300 s) VLF scattering events can be explained by scattering from conductivity changes associated with sprite halos. In contrast, modeled scattered fields resulting from elve-associated conductivity changes, though exhibiting long recovery times, are too weak to sufficiently explain typical LORE observations. Theoretical scattering from structured ionization events (e.g., sprites columns and gigantic jets) is not considered in this work.

  1. New constraints on the escape of ionizing photons from starburst galaxies using ionization-parameter mapping

    International Nuclear Information System (INIS)

    Zastrow, Jordan; Oey, M. S.; Veilleux, Sylvain; McDonald, Michael

    2013-01-01

    The fate of ionizing radiation in starburst galaxies is key to understanding cosmic reionization. However, the galactic parameters on which the escape fraction of ionizing radiation depend are not well understood. Ionization-parameter mapping provides a simple, yet effective, way to study the radiative transfer in starburst galaxies. We obtain emission-line ratio maps of [S III]/[S II] for six, nearby, dwarf starbursts: NGC 178, NGC 1482, NGC 1705, NGC 3125, NGC 7126, and He 2-10. The narrowband images are obtained with the Maryland-Magellan Tunable Filter at Las Campanas Observatory. Using these data, we previously reported the discovery of an optically thin ionization cone in NGC 5253, and here we also discover a similar ionization cone in NGC 3125. This latter cone has an opening angle of 40° ± 5° (0.4 sr), indicating that the passageways through which ionizing radiation may travel correspond to a small solid angle. Additionally, there are three sample galaxies that have winds and/or superbubble activity, which should be conducive to escaping radiation, yet they are optically thick. These results support the scenario that an orientation bias limits our ability to directly detect escaping Lyman continuum in many starburst galaxies. A comparison of the star formation properties and histories of the optically thin and thick galaxies is consistent with the model that high escape fractions are limited to galaxies that are old enough (≳3 Myr) for mechanical feedback to have cleared optically thin passageways in the interstellar medium, but young enough (≲5 Myr) that the ionizing stars are still present.

  2. Ionization of H2O molecules through second order collisions in an argon-filled flow ionization chamber

    International Nuclear Information System (INIS)

    Leonhardt, J.

    1976-01-01

    In an argon-filled ionization chamber with a constant radionuclide radiation source, the ionization of H 2 O through second order collisions with 3sub(p) 2 states of argon excited by field-accelerated electrons is considered within the range of discharge caused by external potentials under atmospheric pressure. It is found that the logarithm of the change of ionization current is proportional to power 3/2 of the electric field strength. Possible formation mechanisms are discussed. Most probable is the ionization of H 2 O through collision with Ar 2 argon dimers originating from excited metastable atoms as a result of triple collision. The production cross section for H 2 O + has been estimated to be sigmasub(H 2 O) approximately 5x10 -15 . (author)

  3. Ionization detector

    International Nuclear Information System (INIS)

    Solomon, E.E.

    1980-01-01

    A safe and reliable apparatus for detecting products of combustion and aerosols in the atmosphere was developed which uses a beta source. It is easy to adjust for optimum performance. The ionization detector comprises a double chamber; one of the chambers is the basic sensing chamber. The sensing chamber is ported to both the secondary chambers to account for slow ambient changes in the atmosphere outside of the chamber. The voltages from the ionization chamber are adjusted with electrodes in each chamber. The ionization chamber contains baffles to direct the air to be sensed as well as an electrostatic screen. A unique electronic circuit provides an inexpensive and reliable means for detecting the signal change which occurs in the ionization chamber. The decision level of the alarm circuit can be adjusted to allow for any desired sensitivity. (D.N.)

  4. Ionizing energy in food processing and pest control. 1. Wholesomeness of food treated with ionizing energy

    International Nuclear Information System (INIS)

    Wierbicki, Eugen

    1986-01-01

    Congressional concerns about the use of ionizing energy for food preservation and to control pests in food products for export and domestic use promoted the preparation of this report by a special task force of the Council for Agricultural Science and Technology (CAST). An overview surveys research conducted on the toxicological safety, nutritional quality, and microbiological safety of foods treated with ionizing energy. Background information is provided on various types of electromagnetic radiation, effects of ionizing energy level and dose, sources of natural background radiation and induced radioactivity, and the nature and safety of various radiolytic products. Objectives, methodologies, and problems associated with feeding studies of toxicological safety are outlined; results of scientific studies, U.S. government wholesomeness studies, and international feeding studies are summarized. Studies on the nutritional value of food products processed using ionized energy have examined the effects of ionizing energy on 1) composite diets, 2) carbohydrates, 3) fats, 4) proteins and amino acids, 5) vitamins (potatoes, onions, fruits, meat, seafood, cereals, vegetables, dairy products, oils), 6) antivitamins, and 7) minerals. The report concludes that currently available scientific evidence indicates that foods exposed to ionizing energy under the conditions proposed for commercial application are 1) wholesome (safe to eat) and 2) comparable in nutritional adequacy to fresh or conventionally processed foods

  5. Population of vibrational levels of carbon dioxide by cylindrical fast ionization wave

    KAUST Repository

    Levko, Dmitry

    2017-09-08

    The population of vibrational levels of carbon dioxide (CO2) by a cylindrical fast ionization wave is analyzed using a one-dimensional Particle-in-Cell Monte Carlo collisions model. The model takes into account the inelastic electron-neutral collisions as well as the super-elastic collisions between electrons and excited species. We observe an efficient population of only the first two levels of the symmetric and asymmetric vibrational modes of CO2 by means of a fast ionization wave. The excitation of other higher vibrational modes by the fast ionization wave is inefficient. Additionally, we observe a strong influence of the secondary electron emission on the population of vibrational states of CO2. This effect is associated with the kinetics of high energy electrons generated in the cathode sheath.

  6. Ionizing radiation in environment

    International Nuclear Information System (INIS)

    Jandl, J.; Petr, I.

    1988-01-01

    The basic terms are explained such as the atom, radioactivity, nuclear reaction, interaction of ionizing radiation with matter, etc. The basic dosimetric variables and units and properties of radionuclides and ionizing radiation are given. Natural and artificial sources of ionizing radiation are discussed with regard to the environment and the propagation and migration of radionuclides is described in the environment to man. The impact is explained of ionizing radiation on the cell and the somatic and genetic effects of radiation on man are outlined. Attention is devoted to protection against ionizing radiation and to radiation limits, also to the detection, dosimetry and monitoring of ionizing radiation in the environment. (M.D.). 92 figs., 40 tabs. 74 refs

  7. The requirements for low-temperature plasma ionization support miniaturization of the ion source.

    Science.gov (United States)

    Kiontke, Andreas; Holzer, Frank; Belder, Detlev; Birkemeyer, Claudia

    2018-06-01

    Ambient ionization mass spectrometry (AI-MS), the ionization of samples under ambient conditions, enables fast and simple analysis of samples without or with little sample preparation. Due to their simple construction and low resource consumption, plasma-based ionization methods in particular are considered ideal for use in mobile analytical devices. However, systematic investigations that have attempted to identify the optimal configuration of a plasma source to achieve the sensitive detection of target molecules are still rare. We therefore used a low-temperature plasma ionization (LTPI) source based on dielectric barrier discharge with helium employed as the process gas to identify the factors that most strongly influence the signal intensity in the mass spectrometry of species formed by plasma ionization. In this study, we investigated several construction-related parameters of the plasma source and found that a low wall thickness of the dielectric, a small outlet spacing, and a short distance between the plasma source and the MS inlet are needed to achieve optimal signal intensity with a process-gas flow rate of as little as 10 mL/min. In conclusion, this type of ion source is especially well suited for downscaling, which is usually required in mobile devices. Our results provide valuable insights into the LTPI mechanism; they reveal the potential to further improve its implementation and standardization for mobile mass spectrometry as well as our understanding of the requirements and selectivity of this technique. Graphical abstract Optimized parameters of a dielectric barrier discharge plasma for ionization in mass spectrometry. The electrode size, shape, and arrangement, the thickness of the dielectric, and distances between the plasma source, sample, and MS inlet are marked in red. The process gas (helium) flow is shown in black.

  8. Long term ionization response of several BiCMOS VLSIC technologies

    International Nuclear Information System (INIS)

    Pease, R.L.; Combs, W.; Clark, S.

    1992-01-01

    BiCMOS is emerging as a strong competitor to CMOS for gate arrays and memories because of its performance advantages for the same feature size. In this paper, the authors examine the long term ionization response of five BiCMOS technologies by characterizing test structures which emphasize the various failure modes of CMOS and bipolar. The primary failure modes are found to be associated with the recessed field oxide isolation; edge leakage in the n channel MOSFETs and buried layer to buried layer leakage in the bipolar. The ionization failure thresholds for worst case bias were in the range of 5-20 Krad(Si) for both failure modes in all five technologies

  9. Endoergic chemi-ionization in N-O collisions

    International Nuclear Information System (INIS)

    Nielsen, S.E.; Dahler, J.S.

    1979-01-01

    A semiclassical theory of endoergic chemi-ionization is developed and applied to the ionizing events that occur when ground state oxygen atoms collide with nitrogen atoms in the ground and first excited states. The approach used is an adaptation and extension of earlier theories due to Bardsley, Nakamura, and Miller. The theory relates the experimental associative (AI) and Penning ionization (PI) cross sections to the following events: formation of a stable diatomic ion (AI), neutral and ionized atomic fragments (PI), or of a metastable diatomic rotational resonance (DI, delayed ionization). The heavy particle motions are treated classically in terms of adiabatic potential energy functions, while localized nonadiabatic transitions also are taken into account by using the Landau-Zener approximation. Finally, the theoretical predictions compare well with the results of Ringer and Gentry's (1978) merged beam experiments

  10. Ionization and dissociation dynamics of vinyl bromide probed by femtosecond extreme ultraviolet transient absorption spectroscopy

    International Nuclear Information System (INIS)

    Lin, Ming-Fu; Neumark, Daniel M.; Gessner, Oliver; Leone, Stephen R.

    2014-01-01

    Strong-field induced ionization and dissociation dynamics of vinyl bromide, CH 2 =CHBr, are probed using femtosecond extreme ultraviolet (XUV) transient absorption spectroscopy. Strong-field ionization is initiated with an intense femtosecond, near infrared (NIR, 775 nm) laser field. Femtosecond XUV pulses covering the photon energy range of 50-72 eV probe the subsequent dynamics by measuring the time-dependent spectroscopic features associated with transitions of the Br (3d) inner-shell electrons to vacancies in molecular and atomic valence orbitals. Spectral signatures are observed for the depletion of neutral C 2 H 3 Br, the formation of C 2 H 3 Br + ions in their ground (X ~ ) and first excited (A ~ ) states, the production of C 2 H 3 Br ++ ions, and the appearance of neutral Br ( 2 P 3/2 ) atoms by dissociative ionization. The formation of free Br ( 2 P 3/2 ) atoms occurs on a timescale of 330 ± 150 fs. The ionic A ~ state exhibits a time-dependent XUV absorption energy shift of ∼0.4 eV within the time window of the atomic Br formation. The yield of Br atoms correlates with the yield of parent ions in the A ~ state as a function of NIR peak intensity. The observations suggest that a fraction of vibrationally excited C 2 H 3 Br + (A ~ ) ions undergoes intramolecular vibrational energy redistribution followed by the C–Br bond dissociation. The C 2 H 3 Br + (X ~ ) products and the majority of the C 2 H 3 Br ++ ions are relatively stable due to a deeper potential well and a high dissociation barrier, respectively. The results offer powerful new insights about orbital-specific electronic processes in high field ionization, coupled vibrational relaxation and dissociation dynamics, and the correlation of valence hole-state location and dissociation in polyatomic molecules, all probed simultaneously by ultrafast table-top XUV spectroscopy

  11. Laser ablation/ionization studies in a glow discharge

    International Nuclear Information System (INIS)

    Hess, K.R.; Harrison, W.W.

    1985-01-01

    The pin cathode glow discharge is used in the laboratory as an atomization/ionization source for a variety of applications, including solids mass spectrometry. Coupled with a tunable dye laser, the glow discharge may also serve as an atom reservoir for resonance ionization mass spectrometry in which the laser ionizes the discharge sputtered atoms. By tightly focusing the laser onto solid samples, various ablation effects may also be investigated. The laser may be used to generate an ionized plasma which may be directly analyzed by mass spectrometry. Alternatively, the ablated neutral atoms may be used in post-ablation excitation/ionization processes, in this case the glow discharge. The results of these investigations are the basis of this paper

  12. Perceived Incidence and Importance of Lay-Ideas on Ionizing Radiation: Results of a Delphi-Study among Radiation-Experts.

    Science.gov (United States)

    Eijkelhof, H. M. C.; And Others

    1990-01-01

    Described are lay-ideas which may exist about ionizing radiation, the importance of these ideas for risk management, and the relationships between various lay-ideas. Lay-ideas were used to gain a better insight into the problems of learning about ionizing radiation and to construct appropriate teaching materials and strategies. (KR)

  13. Fundamental studies of molecular multiphoton ionization

    International Nuclear Information System (INIS)

    Miller, J.C.; Compton, R.N.

    1984-04-01

    For several years the authors have performed fundamental studies of molecular multiphoton ionization (MPI). We will present a potpourri of techniques and results chosen to illustrate the interesting complexities of molecular MPI. Techniques used include time-of-flight mass spectroscopy, photoelectron spectroscopy, supersonic expansion cooling of molecular beams, harmonic generation, two-color laser MPI, and polarization spectroscopy. Whenever possible the relevance of these results to resonance ionization spectroscopy schemes will be delineated. 23 references, 10 figures

  14. Transport coefficients in high-temperature ionized air flows with electronic excitation

    Science.gov (United States)

    Istomin, V. A.; Oblapenko, G. P.

    2018-01-01

    Transport coefficients are studied in high-temperature ionized air mixtures using the modified Chapman-Enskog method. The 11-component mixture N2/N2+/N /N+/O2/O2+/O /O+/N O /N O+/e- , taking into account the rotational and vibrational degrees of freedom of molecules and electronic degrees of freedom of both atomic and molecular species, is considered. Using the PAINeT software package, developed by the authors of the paper, in wide temperature range calculations of the thermal conductivity, thermal diffusion, diffusion, and shear viscosity coefficients for an equilibrium ionized air mixture and non-equilibrium flow conditions for mixture compositions, characteristic of those in shock tube experiments and re-entry conditions, are performed. For the equilibrium air case, the computed transport coefficients are compared to those obtained using simplified kinetic theory algorithms. It is shown that neglecting electronic excitation leads to a significant underestimation of the thermal conductivity coefficient at temperatures higher than 25 000 K. For non-equilibrium test cases, it is shown that the thermal diffusion coefficients of neutral species and the self-diffusion coefficients of all species are strongly affected by the mixture composition, while the thermal conductivity coefficient is most strongly influenced by the degree of ionization of the flow. Neglecting electronic excitation causes noticeable underestimation of the thermal conductivity coefficient at temperatures higher than 20 000 K.

  15. Interference effects at photoionization of Rydberg atoms by a strong electromagnetic field

    International Nuclear Information System (INIS)

    Movsesyan, A.M.; Fedorov, M.V.

    1989-01-01

    The photoionization of Rydberg atoms in a strong electromagnetic field is considered. Degeneration of the levels with respect to the orbital moment, their Stark splitting and the possibility of resonant interaction with levels of lower energy are taken into account. The complex quasi-energies of the system, photoelectron spectrum in the limit of an infinite duration of interaction and the time dependence of the total ionization probability are found. It is shown that a narrowing of the quasi-energy levels occurs in a strong field. Against a background of the quasi- continuum the quasi-energy spectrum consists of more or less narrow levels. In this case the photoelectron spectrum acquires a multi-peak form. With increasing field strength the height of the peaks increases, whereas their width decreases. The ionization rate decreases with increasing field strength. The presence of a quasi-continuum is the cause of the partially non-exponential nature of the atomic disintegration

  16. Experimental characterization of a strongly coupled solid density plasma generated in a short-pulse laser target interaction

    International Nuclear Information System (INIS)

    Gregori, G.; Hansen, S.B.; Key, M.H.; King, J.; Mackinnon, A.J.; Park, H.; Patel, P.K.; Shepard, R.; Snavely, R.A.; Wilks, S.C.; Glenzer, S.H.

    2005-01-01

    We have measured high resolution copper Kα spectra from a picosecond high intensity laser produced plasma. By fitting the shape of the experimental spectra with a self-consistent-field model which includes all the relevant line shifts from multiply ionized atoms, we are able to infer time and spatially averaged electron temperatures (T e ) and ionization state (Z) in the foil. Our results show increasing values for T e and Z when the overall mass of the target is reduced. In particular, we measure temperatures in excess of 200 eV with Z ∼ 13-14. For these conditions the ion-ion coupling constant is Λ ii ∼ 8-9, thus suggesting the achievement of a strongly coupled plasma regime

  17. Experimental characterization of a strongly coupled solid density plasma generated in a short-pulse laser target interaction

    Energy Technology Data Exchange (ETDEWEB)

    Gregori, G; Hansen, S B; Key, M H; King, J; Mackinnon, A J; Park, H; Patel, P K; Shepard, R; Snavely, R A; Wilks, S C; Glenzer, S H

    2005-03-17

    We have measured high resolution copper K{alpha} spectra from a picosecond high intensity laser produced plasma. By fitting the shape of the experimental spectra with a self-consistent-field model which includes all the relevant line shifts from multiply ionized atoms, we are able to infer time and spatially averaged electron temperatures (T{sub e}) and ionization state (Z) in the foil. Our results show increasing values for T{sub e} and Z when the overall mass of the target is reduced. In particular, we measure temperatures in excess of 200 eV with Z {approx} 13-14. For these conditions the ion-ion coupling constant is {Lambda}{sub ii} {approx} 8-9, thus suggesting the achievement of a strongly coupled plasma regime.

  18. Ionizing energy treatment of poultry

    International Nuclear Information System (INIS)

    Mulder, R.W.A.W.

    1983-01-01

    The application of an ionizing energy treatment to poultry carcasses results in a decrease of the number of potentially pathogenic microorganisms, e.g. Salmonellae. At the same time the refrigerated shelf life of treated poultry products is considerably increased. To achieve these beneficial effects doses ranging from 2.00 to 9.00 kGy are needed, but in poultry doses over 5.00 kGy may cause undesirable side-effects. To asses the microbiological quality of ionizing radiation treated end-products adequate isolation methods should be used to include all sublethally injured microorganisms in the colony counts. The assessment of the required lethality of an ionizing energy treatment is difficult as D 10 (decimal reduction) - values depend greatly on several parameters

  19. Biological Effects of Ionizing Radiation

    Science.gov (United States)

    Ingram, M.; Mason, W. B.; Whipple, G. H.; Howland, J. W.

    1952-04-07

    This report presents a review of present knowledge and concepts of the biological effects of ionizing radiations. Among the topics discussed are the physical and chemical effects of ionizing radiation on biological systems, morphological and physiological changes observed in biological systems subjected to ionizing radiations, physiological changes in the intact animal, latent changes following exposure of biological systems to ionizing radiations, factors influencing the biological response to ionizing radiation, relative effects of various ionizing radiations, and biological dosimetry.

  20. Efficient ionizer for polarized H- formation

    International Nuclear Information System (INIS)

    Alessi, J.G.

    1985-01-01

    An ionizer is under development for a polarized H - source based on the resonant charge exchange reaction polarized H 0 + D - → polarized H - + D 0 . The polarized H 0 beam passes through the center of a magnetron surface-plasma source having an annular geometry, where it crosses a high current (approx.0.5 A), 200 eV D - beam. Calculations predict an H 0 → H - ionization efficiency of approx.7%, more than an order of magnitude higher than that obtained on present ground state atomic beam sources. In initial experiments using an unpolarized H 0 beam, H - currents in excess of 100 μA have been measured. While the ionization efficiency is now only about the same as other methods (Cs beam, for example), the results are encouraging since it appears that by injecting positive ions to improve the space-charge neutralization, and by improving the extraction optics, considerable gains in intensity will be made. We will then use this ionizer with a polarized H 0 beam, and measure the polarization of the resulting H - beam. If no depolarization is observed this ionizer will be combined with an atomic beam, cooled to 5 to 6 K, to give a polarized H - beam expected to be in the milliampere range for use in the AGS

  1. Ionization chambers

    International Nuclear Information System (INIS)

    Boag, J.W.

    1987-01-01

    Although a variety of solid-state and chemical methods for measuring radiation dose have been developed in recent decades and calorimetry can now provide an absolute standard of reference, ionization dosimetry retains its position as the most widely used, most convenient, and, in most situations, most accurate method of measuring either exposure or absorbed dose. The ionization chamber itself is the central element in this system of dosimetry. In this chapter the principles governing the construction and operation of ionization chambers of various types are examined. Since the ionization chambers now in general use are nearly all of commercial manufacture, the emphasis is on operating characteristics and interpretation of measurements rather than on details of construction, although some knowledge of the latter is often required when applying necessary corrections to the measured quantities. Examples are given of the construction of typical chambers designed for particular purposes, and the methods of calibrating them are discussed

  2. DWARF GALAXIES WITH IONIZING RADIATION FEEDBACK. I. ESCAPE OF IONIZING PHOTONS

    International Nuclear Information System (INIS)

    Kim, Ji-hoon; Krumholz, Mark R.; Goldbaum, Nathan J.; Wise, John H.; Turk, Matthew J.; Abel, Tom

    2013-01-01

    We describe a new method for simulating ionizing radiation and supernova feedback in the analogs of low-redshift galactic disks. In this method, which we call star-forming molecular cloud (SFMC) particles, we use a ray-tracing technique to solve the radiative transfer equation for ultraviolet photons emitted by thousands of distinct particles on the fly. Joined with high numerical resolution of 3.8 pc, the realistic description of stellar feedback helps to self-regulate star formation. This new feedback scheme also enables us to study the escape of ionizing photons from star-forming clumps and from a galaxy, and to examine the evolving environment of star-forming gas clumps. By simulating a galactic disk in a halo of 2.3 × 10 11 M ☉ , we find that the average escape fraction from all radiating sources on the spiral arms (excluding the central 2.5 kpc) fluctuates between 0.08% and 5.9% during a ∼20 Myr period with a mean value of 1.1%. The flux of escaped photons from these sources is not strongly beamed, but manifests a large opening angle of more than 60° from the galactic pole. Further, we investigate the escape fraction per SFMC particle, f esc (i), and how it evolves as the particle ages. We discover that the average escape fraction f esc is dominated by a small number of SFMC particles with high f esc (i). On average, the escape fraction from an SFMC particle rises from 0.27% at its birth to 2.1% at the end of a particle lifetime, 6 Myr. This is because SFMC particles drift away from the dense gas clumps in which they were born, and because the gas around the star-forming clumps is dispersed by ionizing radiation and supernova feedback. The framework established in this study brings deeper insight into the physics of photon escape fraction from an individual star-forming clump and from a galactic disk

  3. Influence of ionizing radiation on the mechanical properties of BisGMA/TEGDMA based experimental resin

    International Nuclear Information System (INIS)

    LMP, Campos; Boaro, LC; LKG, Santos; Parra, DF; Lugão, AB

    2015-01-01

    Dental restorative composites are activated by visible light and the polymerization process, known as direct technique, is initiated by absorbing light in a specific wavelength range (450–500 nm). However this technique presented some disadvantages. If light is not inserted correctly, layers uncured can cause countless damage to restoration, especially with regard to mechanical properties. A clinical alternative used to reduce the shortcomings of direct application is the use of composite resins for indirect application. These composites are adaptations of resins prepared for direct use, with differences mainly in the healing process. Besides the traditional photoactivation, indirect application composites may be submitted to particular curing conditions, such as a slow curing rate, heating, vacuum, and inert-gas pressure leading to an oxygen-free environment. However few studies have been conducted on the process of post-curing by ionizing radiation at low doses. On this sense the purpose of this study was to evaluate possible interactions of ionizing radiation in the post-curing process of the experimental composites based on BisGMA/TEGDMA filled with silica Aerosil OX-50 silanized. Characterization of the experimental composites was performed by thermogravimetry analysis, infrared spectroscopy, elastic modulus and flexural strength. Statistical analysis of results was calculated by one-way ANOVA/Tukey's test. Cross-linking of the polymeric matrix caused by ionizing radiation, influenced the thermal stability of irradiated specimens. FTIR analysis showed that the ionizing radiation induced a post-cure reaction in the specimens. The irradiation dose influenced directly the mechanical properties that showed a strong positive correlation between flexural strength and irradiation and between modulus strength and irradiation. - Highlights: • Interactions of ionizing radiation in BisGMA/TEGDMA experimental dental composites filled with sylanized silica.

  4. Low-dose ionizing radiation limitations to seed germination: Results from a model linking physiological characteristics and developmental-dynamics simulation strategy.

    Science.gov (United States)

    Liu, Hui; Hu, Dawei; Dong, Chen; Fu, Yuming; Liu, Guanghui; Qin, Youcai; Sun, Yi; Liu, Dianlei; Li, Lei; Liu, Hong

    2017-08-01

    There is much uncertainty about the risks of seed germination after repeated or protracted environmental low-dose ionizing radiation exposure. The purpose of this study is to explore the influence mechanism of low-dose ionizing radiation on wheat seed germination using a model linking physiological characteristics and developmental-dynamics simulation. A low-dose ionizing radiation environment simulator was built to investigate wheat (Triticum aestivum L.) seeds germination process and then a kinetic model expressing the relationship between wheat seed germination dynamics and low-dose ionizing radiation intensity variations was developed by experimental data, plant physiology, relevant hypotheses and system dynamics, and sufficiently validated and accredited by computer simulation. Germination percentages were showing no differences in response to different dose rates. However, root and shoot lengths were reduced significantly. Plasma governing equations were set up and the finite element analysis demonstrated H 2 O, CO 2 , O 2 as well as the seed physiological responses to the low-dose ionizing radiation. The kinetic model was highly valid, and simultaneously the related influence mechanism of low-dose ionizing radiation on wheat seed germination proposed in the modeling process was also adequately verified. Collectively these data demonstrate that low-dose ionizing radiation has an important effect on absorbing water, consuming O 2 and releasing CO 2 , which means the risk for embryo and endosperm development was higher. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Lattice Boltzmann method for weakly ionized isothermal plasmas

    International Nuclear Information System (INIS)

    Li Huayu; Ki, Hyungson

    2007-01-01

    In this paper, a lattice Boltzmann method (LBM) for weakly ionized isothermal plasmas is presented by introducing a rescaling scheme for the Boltzmann transport equation. Without using this rescaling, we found that the nondimensional relaxation time used in the LBM is too large and the LBM does not produce physically realistic results. The developed model was applied to the electrostatic wave problem and the diffusion process of singly ionized helium plasmas with a 1-3% degree of ionization under an electric field. The obtained results agree well with theoretical values

  6. Electron impact ionization of large krypton clusters

    Institute of Scientific and Technical Information of China (English)

    Li Shao-Hui; Li Ru-Xin; Ni Guo-Quan; Xu Zhi-Zhan

    2004-01-01

    We show that the detection of ionization of very large van der Waals clusters in a pulsed jet or a beam can be realized by using a fast ion gauge. Rapid positive feedback electron impact ionization and fragmentation processes,which are initially ignited by electron impact ionization of the krypton clusters with the electron current of the ion gauge, result in the appearance of a progressional oscillation-like ion spectrum, or just of a single fast event under critical conditions. Each line in the spectrum represents a correlated explosion or avalanche ionization of the clusters.The phenomena have been analysed qualitatively along with a Rayleigh scattering experiment of the corresponding cluster jet.

  7. Doubly excited helium. From strong correlation to chaos

    International Nuclear Information System (INIS)

    Jiang, Yuhai

    2006-03-01

    In the present dissertation, the double excitation states of helium including the autoionization decay of these states were studied experimentally and theoretically in a broad energy region, which includes the transition from strong correlation below the low single ionization thresholds (SIT) to the region of quantum chaos at energies very close to the double-ionization threshold. Two kind of experiments were performed, namely total-ion-yield measurements with the aim to observe total cross sections (TCS) and electron time-of-flight (TOF) measurements to obtain partial cross sections (PCS) as well as angular distribution parameters (ADP). Both types of measurements were performed at the third generation synchrotron radiation facility BESSY II in Berlin. The TCSs were recorded up to the SIT I 15 , and they were found to be in in excellent agreement with state-of-the-art complex-rotation calculations performed recently by D. Delande. These experimental and theoretical data on the TCSs were analyzed in order to study quantum chaos in doubly excited helium, and interesting signatures of quantum chaos were found. The TOF technique allowed to measure PCSs and ADPs in the energy regions from I 5 to I 9 and I 7 , respectively. These experimental data provide a critical assessment of theoretical models that can be used to explore the dynamics of strong correlation as well as quantum chaos in helium. In the theoretical part of this dissertation, the n- and l-specific PCSs and ADPs below I 4 were calculated employing the R-matrix method. The present theoretical results agree well with a recent experimental study of l-specific PCSs below I 4 by J.R. Harries et al. An analysis of patterns in the PCSs and ADPs on the basis of the present experimental and theoretical l-specific data allowed to improve the present understanding of autoionization decay dynamics in this two-electron atom. (orig.)

  8. Effects of buffer ionization in protein transition volumes.

    Science.gov (United States)

    Lee, Soyoung; Heerklotz, Heiko; Chalikian, Tigran V

    2010-05-01

    Protein denaturation events are generally associated with a change in the state of ionization of abnormally titrating groups and, therefore, are coupled with changes in buffer ionization/neutralization equilibria. Consequently, buffer ionization should influence the measured change in volume accompanying protein denaturation. Changes in volume accompanying protein denaturation reflect the differential packing and hydration of polypeptide chains in their native and denatured conformations while also describing the pressure stability of proteins. A characteristic feature of conformational transitions of globular proteins is a near zero change in volume that is comparable in magnitude with the volume of ionization of biologically relevant buffers. Thus, the impact of buffer ionization on the volume of protein denaturation could be very significant with the potential to affect not only its magnitude but also its sign. To investigate this point quantitatively, we performed pressure perturbation calorimetric (PPC) studies of lysozyme and ribonuclease A at pH 3.0 in four buffers differing in their ionization volumes. Our results identify buffer ionization as an important determinant of protein transition volume that needs to be carefully taken into account. We emphasize that the importance of our results is not limited to PPC measurements but is more general and applies to all volumetric investigations, in particular, extending to the derivation of the pressure-temperature phase diagram of protein stability.

  9. Effects of autoionizing states on two-photon double ionization of the H2 molecule

    International Nuclear Information System (INIS)

    Guan, Xiaoxu; Bartschat, Klaus; Koesterke, Lars; Schneider, Barry I

    2014-01-01

    We report angle-resolved and angle-integrated cross sections for two-photon double-ionization of H by a strong laser pulse. The effect of doubly excited states on the predicted cross sections is addressed.

  10. Pressure of a partially ionized hydrogen gas: numerical results from exact low temperature expansions

    Energy Technology Data Exchange (ETDEWEB)

    Alastuey, A. [Laboratoire de Physique, ENS Lyon, CNRS, Lyon (France); Ballenegger, V. [Institut UTINAM, Universite de Franche-Comte, CNRS, Besancon (France)

    2010-01-15

    We consider a partially ionized hydrogen gas at low densities, where it reduces almost to an ideal mixture made with hydrogen atoms in their ground-state, ionized protons and ionized electrons. By performing systematic low-temperature expansions within the physical picture, in which the system is described as a quantum electron-proton plasma interacting via the Coulomb potential, exact formulae for the first.ve leading corrections to the ideal Saha equation of state have been derived[A. Alastuey, V. Ballenegger et al., J. Stat. Phys. 130, 1119 (2008)]. Those corrections account for all effects of interactions and thermal excitations up to order exp(E{sub H} /kT) included, where E{sub H} {approx_equal} -13.6 eV is the ground state energy of the hydrogen atom. Among the.ve leading corrections, three are easy to evaluate, while the remaining ones involve suitably truncated internal partition functions of H{sub 2} molecules and H{sup -} and H{sub 2}{sup +} ions, for which no analytical formulae are available in closed form. We estimate those partitions functions at.nite temperature via a simple phenomenology based on known values of rotational and vibrational energies. This allows us to compute numerically the leading deviations to the Saha pressure along several isotherms and isochores. Our values are compared with those of the OPAL tables (for pure hydrogen) calculated within the ACTEX method (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Radiation hydrodynamical instabilities in cosmological and galactic ionization fronts

    Science.gov (United States)

    Whalen, Daniel J.; Norman, Michael L.

    2011-11-01

    Ionization fronts, the sharp radiation fronts behind which H/He ionizing photons from massive stars and galaxies propagate through space, were ubiquitous in the universe from its earliest times. The cosmic dark ages ended with the formation of the first primeval stars and galaxies a few hundred Myr after the Big Bang. Numerical simulations suggest that stars in this era were very massive, 25-500 solar masses, with H(II) regions of up to 30,000 light-years in diameter. We present three-dimensional radiation hydrodynamical calculations that reveal that the I-fronts of the first stars and galaxies were prone to violent instabilities, enhancing the escape of UV photons into the early intergalactic medium (IGM) and forming clumpy media in which supernovae later exploded. The enrichment of such clumps with metals by the first supernovae may have led to the prompt formation of a second generation of low-mass stars, profoundly transforming the nature of the first protogalaxies. Cosmological radiation hydrodynamics is unique because ionizing photons coupled strongly to both gas flows and primordial chemistry at early epochs, introducing a hierarchy of disparate characteristic timescales whose relative magnitudes can vary greatly throughout a given calculation. We describe the adaptive multistep integration scheme we have developed for the self-consistent transport of both cosmological and galactic ionization fronts.

  12. Suitability of tunneling ionization produced plasmas for the plasma beat wave accelerator

    International Nuclear Information System (INIS)

    Leeman, W.P.; Clayton, C.E.; Marsh, K.A.; Dyson, A.; Joshi, C.

    1991-01-01

    Tunneling ionization can be thought of as the high intensity, low frequency limit of multi-photon ionization (MPI). Extremely uniform plasmas were produced by the latter process at Rutherford lab for beat wave excitation experiments using a 0.5 μm laser. Plasmas with 100% ionization were produced with densities exceeding 10 17 cm -3 . The experiment uses a CO 2 laser (I max ∼ 5 x 10 14 W/cm 2 ) which allows the formation of plasmas via the tunneling process. For the experiments the authors need plasmas with densities in the range of 5 to 10 x 10 16 cm -3 . Using Thomson scattering as a diagnostic they have explored the density and temperature regime of tunneling ionization produced plasmas. They find that plasmas with densities up to 10 16 cm -3 can indeed be produced and that these plasmas are hot. Beyond this density strong refraction of laser radiation occurs due to the radial profile of the plasma. Implications of this work to the Beat Wave Accelerator program will be discussed

  13. The ionizing treatment of food

    International Nuclear Information System (INIS)

    1998-01-01

    This book of proceedings contains the talks given by the members of the Society of chemical experts of France (SECF) and by various specialists of the ionizing treatment during the scientific days of September 25-26, 1997. The aim of this meeting was to reconsider the effects of ionization from a scientific point of view and apart from the polemics generated by this domain. The following topics were discussed successively: source and characterization of a ionizing treatment, biological effects of ionization on food and the expected consequences, the ionizing treatment and the reduction of the vitamin C content of fruits and vegetables, is it safe to eat irradiated food?, the organoleptic modifications of food after ionization, quality assurance of dosimetry measurements in an industrial installation of food ionization, the French and European regulations in food ionization, the detection of irradiated foodstuffs, processed food and complex lipid matrices, sterilization of dishes for immuno-depressed patients using ionization. (J.S.)

  14. Impact parameter dependence of inner-shell ionization probabilities

    International Nuclear Information System (INIS)

    Cocke, C.L.

    1974-01-01

    The probability for ionization of an inner shell of a target atom by a heavy charged projectile is a sensitive function of the impact parameter characterizing the collision. This probability can be measured experimentally by detecting the x-ray resulting from radiative filling of the inner shell in coincidence with the projectile scattered at a determined angle, and by using the scattering angle to deduce the impact parameter. It is conjectured that the functional dependence of the ionization probability may be a more sensitive probe of the ionization mechanism than is a total cross section measurement. Experimental results for the K-shell ionization of both solid and gas targets by oxygen, carbon and fluorine projectiles in the MeV/amu energy range will be presented, and their use in illuminating the inelastic collision process discussed

  15. 'Saddle-point' ionization

    International Nuclear Information System (INIS)

    Gay, T.J.; Hale, E.B.; Irby, V.D.; Olson, R.E.; Missouri Univ., Rolla; Berry, H.G.

    1988-01-01

    We have studied the ionization of rare gases by protons at intermediate energies, i.e., energies at which the velocities of the proton and the target-gas valence electrons are comparable. A significant channel for electron production in the forward direction is shown to be 'saddle-point' ionization, in which electrons are stranded on or near the saddle-point of electric potential between the receding projectile and the ionized target. Such electrons yield characteristic energy spectra, and contribute significantly to forward-electron-production cross sections. Classical trajectory Monte Carlo calculations are found to provide qualitative agreement with our measurements and the earlier measurements of Rudd and coworkers, and reproduce, in detail, the features of the general ionization spectra. (orig.)

  16. Equipment for handling ionization chamber

    International Nuclear Information System (INIS)

    Altmann, J.

    1988-01-01

    The device consists of an ionization channel with an ionization chamber, of a support ring, axial and radial bearings, a sleeve, a screw gear and an electric motor. The ionization chamber is freely placed on the bottom of the ionization channel. The bottom part of the channel deviates from the vertical axis. The support ring propped against the axial bearing in the sleeve is firmly fixed to the top part of the ionization channel. The sleeve is fixed to the reactor lid. Its bottom part is provided with a recess for the radial bearing which is propped against a screw wheel firmly connected to the ionization channel. In measuring neutron flux, the screw wheel is rotated by the motor, thus rotating the whole ionization channel such that the ionization chamber is displaced into the reactor core.(J.B.). 1 fig

  17. Foodstuffs preservation by ionization

    International Nuclear Information System (INIS)

    1991-12-01

    This document contains all the papers presented at the meeting on foodstuffs preservation by ionization. These papers deal especially with the food ionization process, its development and the view of the food industry on ionization. Refs and figs (F.M.)

  18. First-principles investigations on ionization and thermal conductivity of polystyrene for inertial confinement fusion applications

    Energy Technology Data Exchange (ETDEWEB)

    Hu, S. X., E-mail: shu@lle.rochester.edu; Goncharov, V. N.; McCrory, R. L.; Skupsky, S. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Collins, L. A.; Kress, J. D. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2016-04-15

    Using quantum molecular-dynamics (QMD) methods based on the density functional theory, we have performed first-principles investigations of the ionization and thermal conductivity of polystyrene (CH) over a wide range of plasma conditions (ρ = 0.5 to 100 g/cm{sup 3} and T = 15 625 to 500 000 K). The ionization data from orbital-free molecular-dynamics calculations have been fitted with a “Saha-type” model as a function of the CH plasma density and temperature, which gives an increasing ionization as the CH density increases even at low temperatures (T < 50 eV). The orbital-free molecular dynamics method is only used to gauge the average ionization behavior of CH under the average-atom model in conjunction with the pressure-matching mixing rule. The thermal conductivities (κ{sub QMD}) of CH, derived directly from the Kohn–Sham molecular-dynamics calculations, are then analytically fitted with a generalized Coulomb logarithm [(lnΛ){sub QMD}] over a wide range of plasma conditions. When compared with the traditional ionization and thermal conductivity models used in radiation–hydrodynamics codes for inertial confinement fusion simulations, the QMD results show a large difference in the low-temperature regime in which strong coupling and electron degeneracy play an essential role in determining plasma properties. Hydrodynamic simulations of cryogenic deuterium–tritium targets with CH ablators on OMEGA and the National Ignition Facility using the QMD-derived ionization and thermal conductivity of CH have predicted ∼20% variation in target performance in terms of hot-spot pressure and neutron yield (gain) with respect to traditional model simulations.

  19. Ambient ionization mass spectrometry: A tutorial

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Min-Zong; Cheng, Sy-Chi; Cho, Yi-Tzu [Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Shiea, Jentaie, E-mail: jetea@fac.nsysu.edu.tw [Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Cancer Center, Kaohsiung Medical University, Kaohsiung, Taiwan (China)

    2011-09-19

    Highlights: {yields} Ambient ionization technique allows the direct analysis of sample surfaces with little or no sample pretreatment. {yields} We sort ambient ionization techniques into three main analytical strategies, direct ionization, direct desorption/ionization, and two-step ionization. {yields} The underlying principles of operation, ionization processes, detecting mass ranges, sensitivity, and representative applications of these techniques are described and compared. - Abstract: Ambient ionization is a set of mass spectrometric ionization techniques performed under ambient conditions that allows the direct analysis of sample surfaces with little or no sample pretreatment. Using combinations of different types of sample introduction systems and ionization methods, several novel techniques have been developed over the last few years with many applications (e.g., food safety screening; detection of pharmaceuticals and drug abuse; monitoring of environmental pollutants; detection of explosives for antiterrorism and forensics; characterization of biological compounds for proteomics and metabolomics; molecular imaging analysis; and monitoring chemical and biochemical reactions). Electrospray ionization and atmospheric pressure chemical ionization are the two main ionization principles most commonly used in ambient ionization mass spectrometry. This tutorial paper provides a review of the publications related to ambient ionization techniques. We describe and compare the underlying principles of operation, ionization processes, detecting mass ranges, sensitivity, and representative applications of these techniques.

  20. Ambient ionization mass spectrometry: A tutorial

    International Nuclear Information System (INIS)

    Huang, Min-Zong; Cheng, Sy-Chi; Cho, Yi-Tzu; Shiea, Jentaie

    2011-01-01

    Highlights: → Ambient ionization technique allows the direct analysis of sample surfaces with little or no sample pretreatment. → We sort ambient ionization techniques into three main analytical strategies, direct ionization, direct desorption/ionization, and two-step ionization. → The underlying principles of operation, ionization processes, detecting mass ranges, sensitivity, and representative applications of these techniques are described and compared. - Abstract: Ambient ionization is a set of mass spectrometric ionization techniques performed under ambient conditions that allows the direct analysis of sample surfaces with little or no sample pretreatment. Using combinations of different types of sample introduction systems and ionization methods, several novel techniques have been developed over the last few years with many applications (e.g., food safety screening; detection of pharmaceuticals and drug abuse; monitoring of environmental pollutants; detection of explosives for antiterrorism and forensics; characterization of biological compounds for proteomics and metabolomics; molecular imaging analysis; and monitoring chemical and biochemical reactions). Electrospray ionization and atmospheric pressure chemical ionization are the two main ionization principles most commonly used in ambient ionization mass spectrometry. This tutorial paper provides a review of the publications related to ambient ionization techniques. We describe and compare the underlying principles of operation, ionization processes, detecting mass ranges, sensitivity, and representative applications of these techniques.

  1. Extremely-high vacuum pressure measurement by laser ionization

    International Nuclear Information System (INIS)

    Kokubun, Kiyohide

    1991-01-01

    Laser ionization method has the very high sensitivity for detecting atoms and molecules. Hurst et al. successfully detected a single Cs atom by means of resonance ionization spectroscopy developed by them. Noting this high sensitivity, the authors have attempted to apply the laser ionization method to measure gas pressure, particularly in the range down to extremely high vacuum. At present, hot cathode ionization gauges are used for measuring gas pressure down to ultrahigh vacuum, however, those have a number of disadvantages. The pressure measurement using lasers does not have such disadvantages. The pressure measurement utilizing the laser ionization method is based on the principle that when laser beam is focused through a lens, the amount of atom or molecule ions generated in the focused space region is proportional to gas pressure. In this paper, the experimental results are presented on the nonresonant multiphoton ionization characteristics of various kinds of gases, the ion detection system with high sensitivity and an extremely high vacuum system prepared for the laser ionization experiment. (K.I.)

  2. Mottled Protoplanetary Disk Ionization by Magnetically Channeled T Tauri Star Energetic Particles

    Science.gov (United States)

    Fraschetti, F.; Drake, J. J.; Cohen, O.; Garraffo, C.

    2018-02-01

    The evolution of protoplanetary disks is believed to be driven largely by angular momentum transport resulting from magnetized disk winds and turbulent viscosity. The ionization of the disk that is essential for these processes has been thought to be due to host star coronal X-rays but could also arise from energetic particles produced by coronal flares, or traveling shock waves, and advected by the stellar wind. We have performed test-particle numerical simulations of energetic protons propagating into a realistic T Tauri stellar wind, including a superposed small-scale magnetostatic turbulence. The isotropic (Kolmogorov power spectrum) turbulent component is synthesized along the individual particle trajectories. We have investigated the energy range [0.1–10] GeV, consistent with expectations from Chandra X-ray observations of large flares on T Tauri stars and recent indications by the Herschel Space Observatory of a significant contribution of energetic particles to the disk ionization of young stars. In contrast with a previous theoretical study finding a dominance of energetic particles over X-rays in the ionization throughout the disk, we find that the disk ionization is likely dominated by X-rays over much of its area, except within narrow regions where particles are channeled onto the disk by the strongly tangled and turbulent magnetic field. The radial thickness of such regions is 5 stellar radii close to the star and broadens with increasing radial distance. This likely continues out to large distances from the star (10 au or greater), where particles can be copiously advected and diffused by the turbulent wind.

  3. Ionization of food products

    International Nuclear Information System (INIS)

    Vasseur, J.P.

    1991-01-01

    After general remarks on foods preservation, on international works and on ionization future prospects, main irradiation sources are described. Recalls on radioactivity, on radiation-matter interaction, on toxicology of ionized foods and on ionized foods detection are given. Ionization applications to various products are reviewed, especially in: - Poultry meat - Fishing products - Fresh fruits and vegetables - Dry fruits and vegetables - spices, tea, infusion - prepacked products... An evaluation of economics and sociocultural impacts is presented in connection with recent experiments [fr

  4. Wavelength dependent photoelectron circular dichroism of limonene studied by femtosecond multiphoton laser ionization and electron-ion coincidence imaging

    Science.gov (United States)

    Rafiee Fanood, Mohammad M.; Janssen, Maurice H. M.; Powis, Ivan

    2016-09-01

    Enantiomers of the monoterpene limonene have been investigated by (2 + 1) resonance enhanced multiphoton ionization and photoelectron circular dichroism employing tuneable, circularly polarized femtosecond laser pulses. Electron imaging detection provides 3D momentum measurement while electron-ion coincidence detection can be used to mass-tag individual electrons. Additional filtering, by accepting only parent ion tagged electrons, can be then used to provide discrimination against higher energy dissociative ionization mechanisms where more than three photons are absorbed to better delineate the two photon resonant, one photon ionization pathway. The promotion of different vibrational levels and, tentatively, different electronic ion core configurations in the intermediate Rydberg states can be achieved with different laser excitation wavelengths (420 nm, 412 nm, and 392 nm), in turn producing different state distributions in the resulting cations. Strong chiral asymmetries in the lab frame photoelectron angular distributions are quantified, and a comparison made with a single photon (synchrotron radiation) measurement at an equivalent photon energy.

  5. Kinematics of 3-body in Ionization Collision

    International Nuclear Information System (INIS)

    Della Picca, Renata

    2003-01-01

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

  6. Experiments on Coulomb ionization by charged particles

    International Nuclear Information System (INIS)

    Andersen, J.U.; Laegsgaard, E.; Lund, M.

    1978-01-01

    Inner-shell ionization by light projectiles, i.e., in very asymmetric collisions, is often denoted 'Coulomb ionization' because it is caused by the Coulomb interaction between the electron and the projectile. Although with little justification, the term is also used to distinquish such processes, in which the projectile Coulomb field is a small perturbation, from ionization in more violent, nearly symmetric ion-atom collisions. A discussion of Coulomb ionization of atomic K shells is given, with emphasis on experimental methods and results. The discussion is not intended as a review of the field but rather as a progress report on the anthor's work on the subject. A more detailed account was recently presented at the ICPEAC meeting in Paris. (Auth.)

  7. THE ESCAPE FRACTION OF IONIZING RADIATION FROM GALAXIES

    International Nuclear Information System (INIS)

    Benson, Andrew; Venkatesan, Aparna; Shull, J. Michael

    2013-01-01

    The escape of ionizing radiation from galaxies plays a critical role in the evolution of gas in galaxies, and the heating and ionization history of the intergalactic medium. We present semi-analytic calculations of the escape fraction of ionizing radiation for both hydrogen and helium from galaxies ranging from primordial systems to disk-type galaxies that are not heavily dust-obscured. We consider variations in the galaxy density profile, source type, location, and spectrum, and gas overdensity/distribution factors. For sufficiently hard first-light sources, the helium ionization fronts closely track or advance beyond that of hydrogen. Key new results in this work include calculations of the escape fractions for He I and He II ionizing radiation, and the impact of partial ionization from X-rays from early active galactic nuclei or stellar clusters on the escape fractions from galaxy halos. When factoring in frequency-dependent effects, we find that X-rays play an important role in boosting the escape fractions for both hydrogen and helium, but especially for He II. We briefly discuss the implications of these results for recent observations of the He II reionization epoch at low redshifts, as well as the UV data and emission-line signatures from early galaxies anticipated from future satellite missions.

  8. THE ESCAPE FRACTION OF IONIZING RADIATION FROM GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Benson, Andrew [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Venkatesan, Aparna [Department of Physics and Astronomy, University of San Francisco, San Francisco, CA 94117 (United States); Shull, J. Michael, E-mail: abenson@obs.carnegiescience.edu, E-mail: avenkatesan@usfca.edu, E-mail: michael.shull@colorado.edu [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States)

    2013-06-10

    The escape of ionizing radiation from galaxies plays a critical role in the evolution of gas in galaxies, and the heating and ionization history of the intergalactic medium. We present semi-analytic calculations of the escape fraction of ionizing radiation for both hydrogen and helium from galaxies ranging from primordial systems to disk-type galaxies that are not heavily dust-obscured. We consider variations in the galaxy density profile, source type, location, and spectrum, and gas overdensity/distribution factors. For sufficiently hard first-light sources, the helium ionization fronts closely track or advance beyond that of hydrogen. Key new results in this work include calculations of the escape fractions for He I and He II ionizing radiation, and the impact of partial ionization from X-rays from early active galactic nuclei or stellar clusters on the escape fractions from galaxy halos. When factoring in frequency-dependent effects, we find that X-rays play an important role in boosting the escape fractions for both hydrogen and helium, but especially for He II. We briefly discuss the implications of these results for recent observations of the He II reionization epoch at low redshifts, as well as the UV data and emission-line signatures from early galaxies anticipated from future satellite missions.

  9. Mass flow and the validity of ionization equilibrium on the sun

    International Nuclear Information System (INIS)

    Joselyn, J.; Munro, R.H.; Holzer, T.E.

    1979-01-01

    which have been reported for the Sun, our results strongly suggest caution in using the assumption of ionization equilibrium for interpreting spectral lines produced in the transition region. (orig.)

  10. Radionuclide measurements using resonantly enhanced collisional ionization

    International Nuclear Information System (INIS)

    Whitaker, T.J.; Bushaw, B.A.; Gerke, G.K.

    1987-01-01

    This report describes development of a laser-enhanced collisional ionization method for direct radionuclide measurements that are independent of radioactive decay. The technique uses two nitrogen-laser-pumped dye lasers to selectively excite the target isotope to an electronic state near the ionization threshold. The excited actinide atoms then undergo collisions with a buffer gas and are efficiently ionized. The resulting ions can be detected by conventional methods. The attributes of this approach include highly sensitive isotope analysis with relatively inexpensive lasers and a simple vacuum system. 9 refs., 3 figs

  11. Electron Impact Excitation-Ionization of Molecules

    Science.gov (United States)

    Ali, Esam Abobakr A.

    In the last few decades, the study of atomic collisions by electron-impact has made significant advances. The most difficult case to study is electron impact ionization of molecules for which many approximations have to be made and the validity of these approximations can only be checked by comparing with experiment. In this thesis, I have examined the Molecular three-body distorted wave (M3DW) or Molecular four-body distorted wave (M4DW) approximations for electron-impact ionization. These models use a fully quantum mechanical approach where all particles are treated quantum mechanically and the post collision interaction (PCI) is treated to all orders of perturbation. These electron impact ionization collisions play central roles in the physics and chemistry of upper atmosphere, biofuel, the operation of discharges and lasers, radiation induced damage in biological material like damage to DNA by secondary electrons, and plasma etching processes. For the M3DW model, I will present results for electron impact single ionization of small molecules such as Water, Ethane, and Carbon Dioxide and the much larger molecules Tetrahydrofuran, phenol, furfural, 1-4 Benzoquinone. I will also present results for the four-body problem in which there are two target electrons involved in the collision. M4DW results will be presented for dissociative excitation-ionization of orientated D2. I will show that M4DW calculations using a variational wave function for the ground state that included s- and p- orbital states give better agreement to the experimental measurements than a ground state approximated as a product of two 1s-type Dyson orbitals.

  12. Parametric study of the relaxation zone behind strong normal shock waves in a dusty ionized monatomic gas

    International Nuclear Information System (INIS)

    Igra, O.; Ben-Dor, G.

    1982-01-01

    The conservation equations appropriate to a steady, one-dimensional flow of dusty ionized argon were solved numerically. The specific effect of each of the physical parameters of the dust upon the flow properties in the relaxation zone is studied. It is found that increasing the dust particle mass causes an increase in both the kinematic and thermal relaxation lengths. In addition to these changes, the flow field inside the relaxation zone is also affected. An increase in the dust mass (caused either by an increase in the dust density or its diameter) causes an increase in the plasma velocity, temperature and electron number density and a decrease in its density and pressure. Similar effects are encountered when the specific heat capacity of the dust is changed. An increase in the emissivity of the dust causes an increase in the plasma density and pressure and a decrease in its velocity, temperature and electron number density. Increasing the emissivity of the dust results in a decrease in the relaxation zone length. (author)

  13. Method and apparatus to monitor a beam of ionizing radiation

    Science.gov (United States)

    Blackburn, Brandon W.; Chichester, David L.; Watson, Scott M.; Johnson, James T.; Kinlaw, Mathew T.

    2015-06-02

    Methods and apparatus to capture images of fluorescence generated by ionizing radiation and determine a position of a beam of ionizing radiation generating the fluorescence from the captured images. In one embodiment, the fluorescence is the result of ionization and recombination of nitrogen in air.

  14. Effectiveness of projectile screening in single and multiple ionization of Ne by B{sup 2+}

    Energy Technology Data Exchange (ETDEWEB)

    Wolff, W.; Luna, H.; Santos, A. C. F.; Montenegro, E. C. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro, 21945-970 RJ (Brazil); DuBois, R. D. [Department of Physics, Missouri University of Science and Technology, Rolla, Missouri 65409 (United States); Montanari, C. C.; Miraglia, J. E. [Instituto de Astronomia y Fisica del Espacio, Casilla de Correo 67, Sucursal 28, C1428EGA, Buenos Aires (Argentina)

    2011-10-15

    Pure multiple ionization cross sections of Ne by B{sup 2+} projectiles have been measured in the energy range of 0.75 to 4.0 MeV and calculated using the continuum distorted wave-eikonal initial state approximation. The experiment and calculations show that the ionization cross sections by B{sup 2+}, principally for the production of highly charged recoils, is strongly enhanced when compared to the bare projectile with the same charge state, He{sup 2+}, at the same velocities.

  15. DYNAMICS OF CORONAL RAIN AND DESCENDING PLASMA BLOBS IN SOLAR PROMINENCES. II. PARTIALLY IONIZED CASE

    Energy Technology Data Exchange (ETDEWEB)

    Oliver, R.; Soler, R.; Terradas, J. [Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain); Zaqarashvili, T. V., E-mail: ramon.oliver@uib.es [Institute of Physics, IGAM, University of Graz, Universitätsplatz 5, 8010, Graz (Austria)

    2016-02-20

    Coronal rain clumps and prominence knots are dense condensations with chromospheric to transition region temperatures that fall down in the much hotter corona. Their typical speeds are in the range 30–150 km s{sup −1} and of the order of 10–30 km s{sup −1}, respectively, i.e., they are considerably smaller than free-fall velocities. These cold blobs contain a mixture of ionized and neutral material that must be dynamically coupled in order to fall together, as observed. We investigate this coupling by means of hydrodynamic simulations in which the coupling arises from the friction between ions and neutrals. The numerical simulations presented here are an extension of those of Oliver et al. to the partially ionized case. We find that, although the relative drift speed between the two species is smaller than 1 m s{sup −1} at the blob center, it is sufficient to produce the forces required to strongly couple charged particles and neutrals. The ionization degree has no discernible effect on the main results of our previous work for a fully ionized plasma: the condensation has an initial acceleration phase followed by a period with roughly constant velocity, and, in addition, the maximum descending speed is clearly correlated with the ratio of initial blob to environment density.

  16. Deviations between experimental and theoretical results in Ar (e, 3e) double ionization

    International Nuclear Information System (INIS)

    Jia, C C; Lahmam-Bennani, A; Cappello, C Dal; Duguet, A; Avaldi, L

    2003-01-01

    The coplanar (e, 3e) relative cross sections for double ionization of argon have been measured at an electron impact energy of E 0 = 561.4 eV and under equal energy sharing among the two 'ejected' electrons, E b = E c = 9 eV. The scattering angle is fixed to θ a = 1.5 degrees, corresponding to a momentum transfer K=0.4 au to the target. The experimental results have been compared with calculations in the first Born approximation, which include only first-order processes in the target-projectile interaction. The comparison shows severe deviations between the experimental and theoretical results. These deviations are much larger than the ones previously observed in helium under comparable kinematics. To fill this gap between theory and experiment, a decisive improvement in the theory is needed. This can be achieved by improving the first-order calculations and by including higher-order processes such as the two-step mechanism, or even new mechanisms, for instance the simultaneous ejection of the pair of target electrons. (letter to the editor)

  17. Penning ionization processes studied by electron spectroscopy

    International Nuclear Information System (INIS)

    Yencha, A.J.

    1978-01-01

    The technique of measuring the kinetic energy of electrons ejected from atomic or molecular species as a result of collisional energy transfer between a metastable excited rare gas atom and an atom or molecule is known as Penning ionization spectroscopy. Like the analogous photoionization process of photoelectron spectroscopy, a considerable amount of information has been gained about the ionization potentials of numerous molecular systems. It is, in fact, through the combined analyses of photoelectron and Penning electron spectra that affords a probe of the particle-particle interactions that occur in the Penning process. In this paper a short survey of the phenomenon of Penning ionization, as studied by electron spectroscopy, will be presented as it pertains to the ionization processes of simple molecules by metastable excited atoms. (author)

  18. Ionization due to the interaction between two Rydberg atoms

    International Nuclear Information System (INIS)

    Robicheaux, F

    2005-01-01

    Using a classical trajectory Monte Carlo method, we have computed the ionization resulting from the interaction between two cold Rydberg atoms. We focus on the products resulting from close interaction between two highly excited atoms. We give information on the distribution of ejected electron energies, the distribution of internal atom energies and the velocity distribution of the atoms and ions after the ionization. If the potential for the atom is not purely Coulombic, the average interaction between two atoms can change from attractive to repulsive giving a Van de Graaff-like mechanism for accelerating atoms. In a small fraction of ionization cases, we find that the ionization leads to a positive molecular ion where all of the distances are larger than 1000 Bohr radii

  19. Biological effects of low-level ionizing and non-ionizing radiation

    International Nuclear Information System (INIS)

    Upton, A.C.

    1986-01-01

    Early in this century it was recognized that large doses of ionizing radiation could injure almost any tissue in the body, but small doses were generally thought to be harmless. By the middle of the century however it came to be suspected that even the smallest doses of ionizing radiation to the gonads might increase the risk of hereditary disease in subsequently-conceived offspring. Since then the hypothesis that carcinogenic and teratogenic effects also have no threshold has been adopted for purposes of radiological protection. It is estimated nevertheless that the risks that may be associated with natural background levels of ionizing irradiation are too small to be detectable. Hence validation of such risk estimates will depend on further elucidation of the dose-effect relationships and mechanisms of the effects in question, through studies at higher dose levels. In contrast to the situation with ionizing radiation, exposure to natural background levels of ultraviolet radiation has been implicated definitively in the etiology of skin cancers in fair-skinned individuals. Persons with inherited effects in DNA repair capacity are particularly susceptible. Non-ionizing radiations of other types can also affect health at high dose levels, but whether they can cause injury at low levels of exposure is not known

  20. Numerical solutions of differential equations of an ionization chamber

    International Nuclear Information System (INIS)

    Novkovic, D.; Tomasevic, M.; Subotic, K.; Manic, S.

    1998-01-01

    A system of reduced differential equations generally valid for plane-parallel, cylindrical, and spherical ionization chambers filled with air, which is appropriate for numerical solution, has been derived. The system has been solved for all three geometries. The comparison of the calculated results of Armstrong and Tate, for plane-parallel ionization chambers, and Sprinkle and Tate, for spherical ionization chambers, with the present calculations has shown a good agreement. The calculated values for ionization chambers filled with CO 2 were also in good agreement with the experimental data of Moriuchi et al (author)

  1. Results from ATLAS and CMS: Strong Interactions and New Physics

    CERN Document Server

    AUTHOR|(INSPIRE)INSPIRE-00179262

    2016-01-01

    Measurements on global properties and precision results on fundamental parameters related to the Strong Interaction sector of the Standard Model of particle physics, and searches for new phenomena beyond the Standard Model, performed by the two large multi-purpose particle detectors at the Large Hadron Collider (LHC), are summarised in this review. Special attention is payed to the new data obtained at $\\sqrt{s}$ = 13~TeV in 2015, which offer a first glimpse at the large physics potential offered by the high-energy running of the LHC.

  2. Signatures of tunneling and multiphoton ionization in the electron-momentum distributions of atoms by intense few-cycle laser pulses

    International Nuclear Information System (INIS)

    Wickenhauser, M.; Tong, X. M.; Arbo, D. G.; Burgdoerfer, J.; Lin, C. D.

    2006-01-01

    Electron-momentum distributions for above-threshold ionization of argon in a few-cycle, linearly polarized laser pulse are investigated. Spectral features characteristic of multiphoton as well as tunneling ionization coexist over a range of the Keldysh parameter γ in the transition regime γ∼1. Surprisingly, the simple strong-field approximation (SFA) is capable of reproducing the key features of the two-dimensional momentum distributions found in the full solution of the time-dependent Schroedinger equation, despite the fact that SFA is known to severely underestimate the total ionization probability

  3. Structure factors for tunneling ionization rates of molecules: General Hartree-Fock-based integral representation

    Science.gov (United States)

    Madsen, Lars Bojer; Jensen, Frank; Dnestryan, Andrey I.; Tolstikhin, Oleg I.

    2017-07-01

    In the leading-order approximation of the weak-field asymptotic theory (WFAT), the dependence of the tunneling ionization rate of a molecule in an electric field on its orientation with respect to the field is determined by the structure factor of the ionizing molecular orbital. The WFAT yields an expression for the structure factor in terms of a local property of the orbital in the asymptotic region. However, in general quantum chemistry approaches molecular orbitals are expanded in a Gaussian basis which does not reproduce their asymptotic behavior correctly. This hinders the application of the WFAT to polyatomic molecules, which are attracting increasing interest in strong-field physics. Recently, an integral-equation approach to the WFAT for tunneling ionization of one electron from an arbitrary potential has been developed. The structure factor is expressed in an integral form as a matrix element involving the ionizing orbital. The integral is not sensitive to the asymptotic behavior of the orbital, which resolves the difficulty mentioned above. Here, we extend the integral representation for the structure factor to many-electron systems treated within the Hartree-Fock method and show how it can be implemented on the basis of standard quantum chemistry software packages. We validate the methodology by considering noble-gas atoms and the CO molecule, for which accurate structure factors exist in the literature. We also present benchmark results for CO2 and for NH3 in the pyramidal and planar geometries.

  4. K-shell ionization and double-ionization of Au atoms with 1.33 MeV photons

    International Nuclear Information System (INIS)

    Belkacem, A.; Dauvergne, D.; Feinberg, B.; Ionescu, D.; Maddi, J.; Sorensen, A.H.

    2000-01-01

    At relativistic energies, the cross section for the atomic photoelectric effect drops off as does the cross section for liberating any bound electron through Compton scattering. However, when the photon energy exceeds twice the rest mass of the electron, ionization may proceed via electron-positron pair creation. We used 1.33 MeV photons impinging on Au thin foils to study double K-shell ionization and vacuum-assisted photoionization. The preliminary results yield a ratio of vacuum-assisted photoionization and pair creation of 2x10 -3 , a value that is substantially higher than the ratio of photo double ionization to single photoionization that is found to be 0.5-1x10 -4 . Because of the difficulties and large error bars associated with the small cross sections additional measurements are needed to minimize systematic errors

  5. Development of a Portable Single Photon Ionization-Photoelectron Ionization Time-of-Flight Mass Spectrometer

    Directory of Open Access Journals (Sweden)

    Yunguang Huang

    2015-01-01

    Full Text Available A vacuum ultraviolet lamp based single photon ionization- (SPI- photoelectron ionization (PEI portable reflecting time-of-flight mass spectrometer (TOFMS was designed for online monitoring gas samples. It has a dual mode ionization source: SPI for analyte with ionization energy (IE below 10.6 eV and PEI for IE higher than 10.6 eV. Two kinds of sampling inlets, a capillary inlet and a membrane inlet, are utilized for high concentration and trace volatile organic compounds, respectively. A mass resolution of 1100 at m/z 64 has been obtained with a total size of 40 × 31 × 29 cm, the weight is 27 kg, and the power consumption is only 70 W. A mixture of benzene, toluene, and xylene (BTX, SO2, and discharging products of SF6 were used to test its performance, and the result showed that the limit of quantitation for BTX is as low as 5 ppbv (S/N = 10 : 1 with linear dynamic ranges greater than four orders of magnitude. The portable TOFMS was also evaluated by analyzing volatile organic compounds from wine and decomposition products of SF6 inside of a gas-insulated switchgear.

  6. Compendium of Current Total Ionizing Dose and Displacement Damage Results from NASA GSFC and NEPP

    Science.gov (United States)

    Topper, Alyson D.; Campola, Michael J.; Chen, Dakai; Casey, Megan C.; Yau, Ka-Yen; Label, Kenneth A.; Cochran, Donna J.; O'Bryan, Martha V.

    2017-01-01

    Total ionizing dose and displacement damage testing was performed to characterize and determine the suitability of candidate electronics for NASA space utilization. Devices tested include opto-electronics, digital, analog, linear bipolar devices, and hybrid devices.

  7. VUV photo-processing of PAH cations: quantitative study on the ionization versus fragmentation processes.

    Science.gov (United States)

    Zhen, Junfeng; Castillo, Sarah Rodriguez; Joblin, Christine; Mulas, Giacomo; Sabbah, Hassan; Giuliani, Alexandre; Nahon, Laurent; Martin, Serge; Champeaux, Jean-Philippe; Mayer, Paul M

    2016-05-10

    Interstellar polycyclic aromatic hydrocarbons (PAHs) are strongly affected by the absorption of vacuum ultraviolet (VUV) photons in the interstellar medium (ISM), yet the branching ratio between ionization and fragmentation is poorly studied. This is crucial for the stability and charge state of PAHs in the ISM in different environments, affecting in turn the chemistry, the energy balance, and the contribution of PAHs to the extinction and emission curves. We studied the interaction of PAH cations with VUV photons in the 7 - 20 eV range from the synchrotron SOLEIL beamline, DESIRS. We recorded by action spectroscopy the relative intensities of photo-fragmentation and photo-ionization for a set of eight PAH cations ranging in size from 14 to 24 carbon atoms, with different structures. At photon energies below ~13.6 eV fragmentation dominates for the smaller species, while for larger species ionization is immediately competitive after the second ionization potential (IP). At higher photon energies, all species behave similarly, the ionization yield gradually increases, leveling off between 0.8 and 0.9 at ~18 eV. Among isomers, PAH structure appears to mainly affect the fragmentation cross section, but not the ionization cross section. We also measured the second IP for all species and the third IP for two of them, all are in good agreement with theoretical ones confirming that PAH cations can be further ionized in the diffuse ISM. Determining actual PAH dication abundances in the ISM will require detailed modeling. Our measured photo-ionization yields for several PAH cations provide a necessary ingredient for such models.

  8. VUV PHOTO-PROCESSING OF PAH CATIONS: QUANTITATIVE STUDY ON THE IONIZATION VERSUS FRAGMENTATION PROCESSES

    Energy Technology Data Exchange (ETDEWEB)

    Zhen, Junfeng; Castillo, Sarah Rodriguez; Joblin, Christine; Mulas, Giacomo; Sabbah, Hassan [Université de Toulouse, UPS-OMP, Institut de Recherche en Astrophysique et Planétologie, Toulouse (France); Giuliani, Alexandre; Nahon, Laurent [Synchrotron SOLEIL, LOrme des Merisiers, F-91192 Gif sur Yvette Cedex (France); Martin, Serge [Institut Lumière Matière, Université Lyon 1-CNRS, Université de Lyon, F-69622 Villeurbanne cedex (France); Champeaux, Jean-Philippe [Laboratoire Collisions Agrégats Réactivité, Université de Toulouse, UPS-IRSAMC, CNRS, 118 Route de Narbonne, Bat 3R1B4, F-31062 Toulouse Cedex 9 (France); Mayer, Paul M., E-mail: christine.joblin@irap.omp.eu [Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa K1N 6N5 (Canada)

    2016-05-10

    Interstellar polycyclic aromatic hydrocarbons (PAHs) are strongly affected by the absorption of vacuum ultraviolet (VUV) photons in the interstellar medium (ISM), yet the branching ratio between ionization and fragmentation is poorly studied. This is crucial for the stability and charge state of PAHs in the ISM in different environments, affecting in turn the chemistry, the energy balance, and the contribution of PAHs to the extinction and emission curves. We studied the interaction of PAH cations with VUV photons in the 7–20 eV range from the synchrotron SOLEIL beamline, DESIRS. We recorded by action spectroscopy the relative intensities of photo-fragmentation and photo-ionization for a set of eight PAH cations ranging in size from 14 to 24 carbon atoms, with different structures. At photon energies below ∼13.6 eV fragmentation dominates for the smaller species, while for larger species ionization is immediately competitive after the second ionization potential (IP). At higher photon energies all species behave similarly; the ionization yield gradually increases, leveling off between 0.8 and 0.9 at ∼18 eV. Among isomers, PAH structure appears to mainly affect the fragmentation cross section but not the ionization cross section. We also measured the second IP for all species and the third IP for two of them; all are in good agreement with theoretical ones, confirming that PAH cations can be further ionized in the diffuse ISM. Determining actual PAH dication abundances in the ISM will require detailed modeling. Our measured photo-ionization yields for several PAH cations provide a necessary ingredient for such models.

  9. VUV PHOTO-PROCESSING OF PAH CATIONS: QUANTITATIVE STUDY ON THE IONIZATION VERSUS FRAGMENTATION PROCESSES

    International Nuclear Information System (INIS)

    Zhen, Junfeng; Castillo, Sarah Rodriguez; Joblin, Christine; Mulas, Giacomo; Sabbah, Hassan; Giuliani, Alexandre; Nahon, Laurent; Martin, Serge; Champeaux, Jean-Philippe; Mayer, Paul M.

    2016-01-01

    Interstellar polycyclic aromatic hydrocarbons (PAHs) are strongly affected by the absorption of vacuum ultraviolet (VUV) photons in the interstellar medium (ISM), yet the branching ratio between ionization and fragmentation is poorly studied. This is crucial for the stability and charge state of PAHs in the ISM in different environments, affecting in turn the chemistry, the energy balance, and the contribution of PAHs to the extinction and emission curves. We studied the interaction of PAH cations with VUV photons in the 7–20 eV range from the synchrotron SOLEIL beamline, DESIRS. We recorded by action spectroscopy the relative intensities of photo-fragmentation and photo-ionization for a set of eight PAH cations ranging in size from 14 to 24 carbon atoms, with different structures. At photon energies below ∼13.6 eV fragmentation dominates for the smaller species, while for larger species ionization is immediately competitive after the second ionization potential (IP). At higher photon energies all species behave similarly; the ionization yield gradually increases, leveling off between 0.8 and 0.9 at ∼18 eV. Among isomers, PAH structure appears to mainly affect the fragmentation cross section but not the ionization cross section. We also measured the second IP for all species and the third IP for two of them; all are in good agreement with theoretical ones, confirming that PAH cations can be further ionized in the diffuse ISM. Determining actual PAH dication abundances in the ISM will require detailed modeling. Our measured photo-ionization yields for several PAH cations provide a necessary ingredient for such models.

  10. VUV photo-processing of PAH cations: quantitative study on the ionization versus fragmentation processes

    Science.gov (United States)

    Zhen, Junfeng; Castillo, Sarah Rodriguez; Joblin, Christine; Mulas, Giacomo; Sabbah, Hassan; Giuliani, Alexandre; Nahon, Laurent; Martin, Serge; Champeaux, Jean-Philippe; Mayer, Paul M.

    2016-01-01

    Interstellar polycyclic aromatic hydrocarbons (PAHs) are strongly affected by the absorption of vacuum ultraviolet (VUV) photons in the interstellar medium (ISM), yet the branching ratio between ionization and fragmentation is poorly studied. This is crucial for the stability and charge state of PAHs in the ISM in different environments, affecting in turn the chemistry, the energy balance, and the contribution of PAHs to the extinction and emission curves. We studied the interaction of PAH cations with VUV photons in the 7 – 20 eV range from the synchrotron SOLEIL beamline, DESIRS. We recorded by action spectroscopy the relative intensities of photo-fragmentation and photo-ionization for a set of eight PAH cations ranging in size from 14 to 24 carbon atoms, with different structures. At photon energies below ~13.6 eV fragmentation dominates for the smaller species, while for larger species ionization is immediately competitive after the second ionization potential (IP). At higher photon energies, all species behave similarly, the ionization yield gradually increases, leveling off between 0.8 and 0.9 at ~18 eV. Among isomers, PAH structure appears to mainly affect the fragmentation cross section, but not the ionization cross section. We also measured the second IP for all species and the third IP for two of them, all are in good agreement with theoretical ones confirming that PAH cations can be further ionized in the diffuse ISM. Determining actual PAH dication abundances in the ISM will require detailed modeling. Our measured photo-ionization yields for several PAH cations provide a necessary ingredient for such models. PMID:27212712

  11. An approach to modelling radiation damage by fast ionizing particles

    International Nuclear Information System (INIS)

    Thomas, G.E.

    1987-01-01

    The paper presents a statistical approach to modelling radiation damage in small biological structures such as enzymes, viruses, and some cells. Irreparable damage is assumed to be caused by the occurrence of ionizations within sensitive regions. For structures containing double-stranded DNA, one or more ionizations occurring within each strand of the DNA will cause inactivation; for simpler structures without double-stranded DNA a single ionization within the structure will be sufficient for inactivation. Damaging ionizations occur along tracks of primary irradiating particles or along tracks of secondary particles released at primary ionizations. An inactivation probability is derived for each damage mechanism, expressed in integral form in terms of the radius of the biological structure (assumed spherical), rate of ionization along primary tracks, and maximum energy for secondary particles. The performance of each model is assessed by comparing results from the model with those derived from data from various experimental studies extracted from the literature. For structures where a single ionization is sufficient for inactivation, the model gives qualitatively promising results; for larger more complex structures containing double-stranded DNA, the model requires further refinements. (author)

  12. Effects of ionizing radiation on the metabolism and longitudinal growth of cartilaginous embryonic chick tibiae in vitro

    International Nuclear Information System (INIS)

    Ridder, L. de; Thierens, H.; Cornelissen, M.; Segaert, O.

    1988-01-01

    The effect of ionizing radiation on the metabolism and longitudinal growth of cartilaginous tibiae of 6.5-day-old chick embryos was studied in vitro over a 3-day period. Before being cultured, tibiae received absorbed doses of 2 to 200 Gy. Of each pair, the counterpart served as control. Compared to the strong inhibition of [ 3 H]thymidine incorporation, already 50% at 10 Gy, the effects of ionizing radiation on [ 3 H]uridine and [ 3 H]proline incorporation were limited: 20 and 40% respectively at 150 Gy. Metabolism of the cartilage cells in our organ culture was almost completely arrested at 200 Gy. Light and electron microscopy showed no morphological differences between irradiated and sham-irradiated tibiae until 150 Gy. At 200 Gy necrosis of most of the cells was observed. No differences in form and arrangement of extracellular fibers were noticed. The results of the metabolic studies and the morphological observations were correlated with the effects of ionizing radiation on the longitudinal growth. In contrast to DNA synthesis, RNA transcription and synthesis of collagen fibres were radioresistant processes. (author)

  13. Effects of ionizing radiation on the metabolism and longitudinal growth of cartilaginous embryonic chick tibiae in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Ridder, L. de; Thierens, H.; Cornelissen, M.; Segaert, O.

    1988-06-01

    The effect of ionizing radiation on the metabolism and longitudinal growth of cartilaginous tibiae of 6.5-day-old chick embryos was studied in vitro over a 3-day period. Before being cultured, tibiae received absorbed doses of 2 to 200 Gy. Of each pair, the counterpart served as control. Compared to the strong inhibition of (/sup 3/H)thymidine incorporation, already 50% at 10 Gy, the effects of ionizing radiation on (/sup 3/H)uridine and (/sup 3/H)proline incorporation were limited: 20 and 40% respectively at 150 Gy. Metabolism of the cartilage cells in our organ culture was almost completely arrested at 200 Gy. Light and electron microscopy showed no morphological differences between irradiated and sham-irradiated tibiae until 150 Gy. At 200 Gy necrosis of most of the cells was observed. No differences in form and arrangement of extracellular fibers were noticed. The results of the metabolic studies and the morphological observations were correlated with the effects of ionizing radiation on the longitudinal growth. In contrast to DNA synthesis, RNA transcription and synthesis of collagen fibres were radioresistant processes.

  14. Introduction to ionizing radiation physics

    International Nuclear Information System (INIS)

    Musilek, L.

    1979-01-01

    Basic properties are described of the atom, atomic nucleus and of ionizing radiation particles; nuclear reactions, ionizing radiation sources and ionizing radiation interaction with matter are explained. (J.P.)

  15. One-photon two-electron processes in helium close to the double ionization threshold

    International Nuclear Information System (INIS)

    Bouri, C.

    2007-04-01

    This work presents a study of the 1 P 0 excited states of He that can be reached by absorption of a single photon carrying an energy close to the double ionization threshold (DIT) (79 eV). Above the DIT, these states are the double continuum states; below, they are the double excited states. These two types of states are tightly coupled to the single continuum states with or without excitation of the residual ion He + , owing to their degeneracy in energy. In a one-photon process, these states can only be formed owing to the electronic correlations in the system which must be well described to obtain quantitative good results. Our study is a part of the work which aims at a united description of all these doubly excited, ionized-excited, and double continuum states. We use the Hyperspherical R-Matrix with Semiclassical Outgoing Waves (HRM-SOW) method, initially dedicated to double photoionization studies. We extend it to extract information on the single continuum. This extension allows us to compute cross sections of single photoionization with or without excitation up to n 50 for an excess of 100 meV just above the double ionization threshold. A deep insight into this process is given by a partial waves analysis. The results obtained shed light on the key role of angular and radial correlations. The numerous data we obtain on double and single ionization allow us to establish a continuity relation between these two processes. We show that single ionization with an infinite excitation of the residual ion merges into double photoionization when the excess energy is redistributed between the two electrons. It appears that this relation is valid not only for low but also for high photon energies. Since the HRM-SOW can produce the integrated cross section for double photoionization with high accuracy in the low energy domain, we check the Wannier threshold law. The parameters extracted support strongly this threshold law, and are in good agreement with experimental

  16. The importance of Rydberg orbitals in dissociative ionization of small hydrocarbon molecules in intense laser fields.

    Science.gov (United States)

    Jochim, Bethany; Siemering, R; Zohrabi, M; Voznyuk, O; Mahowald, J B; Schmitz, D G; Betsch, K J; Berry, Ben; Severt, T; Kling, Nora G; Burwitz, T G; Carnes, K D; Kling, M F; Ben-Itzhak, I; Wells, E; de Vivie-Riedle, R

    2017-06-30

    Much of our intuition about strong-field processes is built upon studies of diatomic molecules, which typically have electronic states that are relatively well separated in energy. In polyatomic molecules, however, the electronic states are closer together, leading to more complex interactions. A combined experimental and theoretical investigation of strong-field ionization followed by hydrogen elimination in the hydrocarbon series C 2 D 2 , C 2 D 4 and C 2 D 6 reveals that the photofragment angular distributions can only be understood when the field-dressed orbitals rather than the field-free orbitals are considered. Our measured angular distributions and intensity dependence show that these field-dressed orbitals can have strong Rydberg character for certain orientations of the molecule relative to the laser polarization and that they may contribute significantly to the hydrogen elimination dissociative ionization yield. These findings suggest that Rydberg contributions to field-dressed orbitals should be routinely considered when studying polyatomic molecules in intense laser fields.

  17. DWBA calculation of positron impact ionization of argon

    Energy Technology Data Exchange (ETDEWEB)

    Campeanu, R I; Alam, M, E-mail: campeanu@yorku.ca [Department of Physics and Astronomy, York University, Toronto, M3J 1P3 (Canada)

    2011-01-01

    The ionization of the 3p and 3s orbitals of argon by 200 eV incident positrons is studied with the DWBA approximation. Our TDCS results for the 3p orbital ionization are found to be in good agreement with recent CDW-EIS data.

  18. Collisional ionization

    International Nuclear Information System (INIS)

    Arnaud, M.

    1985-07-01

    In low density, thin plasmas (such as stellar coronae, interstellar medium, intracluster medium) the ionization process is governed by collision between electrons and ions in their ground state. In view of the recent improvements we thought an updating of ionization rates was really needed. The work is based on both experimental data and theoretical works and give separate estimates for the direct and autoionization rates

  19. Ideal gas behavior of a strongly coupled complex (dusty) plasma.

    Science.gov (United States)

    Oxtoby, Neil P; Griffith, Elias J; Durniak, Céline; Ralph, Jason F; Samsonov, Dmitry

    2013-07-05

    In a laboratory, a two-dimensional complex (dusty) plasma consists of a low-density ionized gas containing a confined suspension of Yukawa-coupled plastic microspheres. For an initial crystal-like form, we report ideal gas behavior in this strongly coupled system during shock-wave experiments. This evidence supports the use of the ideal gas law as the equation of state for soft crystals such as those formed by dusty plasmas.

  20. Ideal gas behavior of a strongly-coupled complex (dusty) plasma

    OpenAIRE

    Oxtoby, Neil P.; Griffith, Elias J.; Durniak, Céline; Ralph, Jason F.; Samsonov, Dmitry

    2012-01-01

    In a laboratory, a two-dimensional complex (dusty) plasma consists of a low-density ionized gas containing a confined suspension of Yukawa-coupled plastic microspheres. For an initial crystal-like form, we report ideal gas behavior in this strongly-coupled system during shock-wave experiments. This evidence supports the use of the ideal gas law as the equation of state for soft crystals such as those formed by dusty plasmas.

  1. Efficient ionizer for polarized H/sup -/ formation

    Energy Technology Data Exchange (ETDEWEB)

    Alessi, J.G.

    1985-01-01

    An ionizer is under development for a polarized H/sup -/ source based on the resonant charge exchange reaction polarized H/sup 0/ + D/sup -/ ..-->.. polarized H/sup -/ + D/sup 0/. The polarized H/sup 0/ beam passes through the center of a magnetron surface-plasma source having an annular geometry, where it crosses a high current (approx.0.5 A), 200 eV D/sup -/ beam. Calculations predict an H/sup 0/ ..-->.. H/sup -/ ionization efficiency of approx.7%, more than an order of magnitude higher than that obtained on present ground state atomic beam sources. In initial experiments using an unpolarized H/sup 0/ beam, H/sup -/ currents in excess of 100 ..mu..A have been measured. While the ionization efficiency is now only about the same as other methods (Cs beam, for example), the results are encouraging since it appears that by injecting positive ions to improve the space-charge neutralization, and by improving the extraction optics, considerable gains in intensity will be made. We will then use this ionizer with a polarized H/sup 0/ beam, and measure the polarization of the resulting H/sup -/ beam. If no depolarization is observed this ionizer will be combined with an atomic beam, cooled to 5 to 6 K, to give a polarized H/sup -/ beam expected to be in the milliampere range for use in the AGS.

  2. Effects of ionizing radiation and steady magnetic field on erythrocytes

    International Nuclear Information System (INIS)

    Ivanov, S. P.; Galutzov, B. P.; Kuzmanova, M. A.; Markov, M. S.

    1996-01-01

    A complex biophysical test for studying the effects of ionizing and non-ionizing radiation has been developed. The following cell and membrane parameters have been investigated: cell size, cell shape, cell distribution by size, electrophoretic mobility, extent of hemolysis, membrane transport and membrane impedance. Gamma ray doses of 2.2 Gy and 3.3 Gy were used as ionizing radiation and steady (DC) magnetic field of 5-90 mT representing the non-ionizing radiation. Erythrocytes from humans and rats were exposed in vitro to both ionizing and non-ionizing radiation. In some experiments ionizing radiation was applied in vivo as well. Each of the simultaneously studied parameters have been found to change as a function of applied radiation. The proposed test allows an estimation of the changes in the elastic, rheological and electrical parameters of cells and biological membranes. Results indicate that ionizing radiation is significantly more effective in an in vivo application, while magnetic fields are more effective when applied in vitro. Surprisingly, steady magnetic fields were found to act as protector against some harmful effects of ionizing radiation. (authors)

  3. Dosimetry of ionizing radiation

    International Nuclear Information System (INIS)

    Musilek, L.; Seda, J.; Trousil, J.

    1992-01-01

    The publication deals with a major field of ionizing radiation dosimetry, viz., integrating dosimetric methods, which are the basic means of operative dose determination. It is divided into the following sections: physical and chemical effects of ionizing radiation; integrating dosimetric methods for low radiation doses (film dosimetry, nuclear emulsions, thermoluminescence, radiophotoluminescence, solid-state track detectors, integrating ionization dosemeters); dosimetry of high ionizing radiation doses (chemical dosimetric methods, dosemeters based on the coloring effect, activation detectors); additional methods applicable to integrating dosimetry (exoelectron emission, electron spin resonance, lyoluminescence, etc.); and calibration techniques for dosimetric instrumentation. (Z.S.). 422 refs

  4. Scientific colloquium on medical supervision of workers exposed to ionizing and non ionizing radiations

    International Nuclear Information System (INIS)

    1975-01-01

    The general principles of medical surveillance for workers exposed to ionizing radiation were defined in the Euratom Basic Standards in 1959. These principles, which are in accordance with the early IGRP publications, have been adopted by the national authorities and implemented without difficulty. However, because of the forthcoming publication of the revised Basic Standards- in accordance with recent IGRP recommendations, the Commission decided to organize a meeting of doctors responsible for the medical surveillance of workers exposed to ionizing radiation in order to disseminate as widely as possible the results of experience gained in the field of radiological protection and to pinpoint the practical difficulties which might arise when the principles were applied. The Commission also considered it important to inform doctors specializing in radiological protection about the principles to be followed by those responsible for the health protection of workers exposed to non-ionizing radiation, particularly microwaves and Laser beams. The complete text of each report in the original language is given in this volume

  5. Interference effects in double ionization of spatially aligned hydrogen molecules by fast highly charged ions

    International Nuclear Information System (INIS)

    Landers, A.L.; Alnaser, A.S.; Tanis, J.A.; Wells, E.; Osipov, T.; Carnes, K.D.; Ben-Itzhak, I.; Cocke, C.L.; McGuire, J.H.

    2004-01-01

    Cross sections differential in target orientation angle were measured for 19 MeV F 8+ +D 2 collisions. Multihit position-sensitive detectors were used to isolate the double-ionization channel and determine a posteriori the full momentum vectors of both ejected D + fragments. A strong dependence of the double ionization cross section on the angle between the incident ion direction and the target molecular axis is observed with a ≅3.5:1 enhancement for molecules aligned perpendicular to the projectile axis. This clear asymmetry is attributed to interference effects, analogous to Young's two-slit experiment, arising from coherent contributions to the ionization from both atomic centers. The data are compared to a simple scattering model based on two center interference

  6. Effects of multiple electronic shells on strong-field multiphoton ionization and high-order harmonic generation of diatomic molecules with arbitrary orientation: An all-electron time-dependent density-functional approach

    International Nuclear Information System (INIS)

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

    2009-01-01

    We present a time-dependent density-functional theory approach with proper long-range potential for an ab initio study of the effect of correlated multielectron responses on the multiphoton ionization (MPI) and high-order harmonic generation (HHG) of diatomic molecules N 2 and F 2 in intense short laser pulse fields with arbitrary molecular orientation. We show that the contributions of inner molecular orbitals to the total MPI probability can be sufficiently large or even dominant over the highest-occupied molecular orbital, depending on detailed electronic structure and symmetry, laser field intensity, and orientation angle. The multielectron effects in HHG are also very important. They are responsible for enhanced HHG at some orientations of the molecular axis. Even strongly bound electrons may have a significant influence on the HHG process.

  7. Ionization in matrix-assisted laser desorption/ionization: singly charged molecular ions are the lucky survivors.

    Science.gov (United States)

    Karas, M; Glückmann, M; Schäfer, J

    2000-01-01

    A new model for the ionization processes in UV matrix-assisted laser desorption/ionization (MALDI) which accounts for the major phenomena observed is presented and discussed. The model retains elements of earlier approaches, such as photoionization and photochemical reactions, but it redefines these in the light of new working questions, most importantly why only singly charged ions are detected. Based on experimental evidence, the formation of singly and multiply charged clusters by a deficiency/excess of ions and also by photoionization and subsequent photochemical processes is pointed out to be the major ionization processes, which typically occur in parallel. The generation of electrons and their partial loss into the surrounding vacuum and solid, on the one hand, results in a positively charged ion-neutral plume facilitating a high overall ionization yield. On the other hand, these electrons, and also the large excess of protonated matrix ions in the negative ion mode, induce effective ion reneutralization in the plume. These neutralization processes are most effective for the highly charged cluster ions initially formed. Their fragmentation behaviour is evidenced in fast metastable fragmentation characteristics and agrees well with an electron capture dissociation mechanism and the enthalpy transfer upon neutralization forms the rationale for the prominent fragmentation and intense chemical noise accompanying successful MALDI. Within the course of the paper, cross-correlations with other desorption/ionization techniques and with earlier discussions on their mechanisms are drawn. Copyright 2000 John Wiley & Sons, Ltd.

  8. First successful ionization of Lr (Z = 103) by a surface-ionization technique

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Tetsuya K., E-mail: sato.tetsuya@jaea.go.jp; Sato, Nozomi; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Ooe, Kazuhiro; Miyashita, Sunao; Schädel, Matthias [Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), 2-4 Shirakata-shirane, Tokai-mura, Ibaraki 319-1195 (Japan); Kaneya, Yusuke; Nagame, Yuichiro [Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), 2-4 Shirakata-shirane, Tokai-mura, Ibaraki 319-1195 (Japan); Graduate School of Science and Engineering, Ibaraki University, 2-1-1, Bunkyo, Mito, Ibaraki 310-8512 (Japan); Osa, Akihiko [Department of Research Reactor and Tandem Accelerator, Japan Atomic Energy Agency (JAEA), 2-4 Shirakata shirane, Tokai-mura, Ibaraki 319-1195 (Japan); Ichikawa, Shin-ichi [Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), 2-4 Shirakata-shirane, Tokai-mura, Ibaraki 319-1195 (Japan); Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Stora, Thierry [ISOLDE, CERN, CH-1211 Geneva 23 (Switzerland); Kratz, Jens Volker [Institut für Kernchemie, Universität Mainz, D-55099 Mainz (Germany)

    2013-02-15

    We have developed a surface ionization ion-source as part of the JAEA-ISOL (Isotope Separator On-Line) setup, which is coupled to a He/CdI{sub 2} gas-jet transport system to determine the first ionization potential of the heaviest actinide lawrencium (Lr, Z = 103). The new ion-source is an improved version of the previous source that provided good ionization efficiencies for lanthanides. An additional filament was newly installed to give better control over its operation. We report, here, on the development of the new gas-jet coupled surface ion-source and on the first successful ionization and mass separation of 27-s {sup 256}Lr produced in the {sup 249}Cf + {sup 11}B reaction.

  9. Ionizing Energy Depositions After Fast Neutron Interactions in Silicon

    CERN Document Server

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

    2016-01-01

    In this 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 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. The data give supplementary information to the results of a previous measurement and are compared with different theoretical predictions.

  10. Study of the ionization of H{sup +}{sub 2} ions in strong laser fields; Untersuchung der Ionisation von H{sup +}{sub 2}-Ionen in starken Laserfeldern

    Energy Technology Data Exchange (ETDEWEB)

    Odenweller, Matthias

    2010-07-01

    In the framework of this thesis it has been succeeded to develop a worldwide unique measurement apparatur, by which hydrogen-molecule ions can be ionized by means of short laser pulses and the reaction product kinematically completely measured. For this a detection method following the Coltrims technique, in which both protons and electrons can be detected over the complete spatial angle. The H{sup +}{sub 2} ions origin from a high-frequency ion source and are accelerated to 400 keV. This ion beam is overlapped with a 780-nm laser pulse othe pulse length 40 fs. After the reaction the molecule ions fragments either via the dissociation channel H{sup +}{sub 2}+nh{nu}{yields}H+H{sup +} or via an ionization followed by a Coulomb explosion: H{sup +}{sub 2}+nh{nu}{yields}H{sup +}+H{sup +}+e{sup -}. The projectiles are detected after a drift path of about 3 m on an ion detector. For the detection of the electrons a special spectrometer was concipated. In the reaction it comes by the comparatively long pulse length already at low intensities to dissociation processes. The dissociating molecule reaches still during the increasing side of the laser pulse in this way distances, in which the charge-resonance-enhanced-ionization (CREI) can take place. Also the angular distribution of the measured protons lying in a very small angular range around the polarization direction of the laser suggests that CREI is the dominant ionization process. At circular polarization however a netto-acceleration of the electrons perpendicularly to the direction of the electric field at the ionization time takes place, so that the measurement of the electron momenta represents a suited measurement quantity for the study of the ionization process. By this way angular distributions of the electrons relatively to the internuclear axis within the polarization plane could be measured.

  11. Ionization chamber

    International Nuclear Information System (INIS)

    Jilbert, P.H.

    1975-01-01

    The invention concerns ionization chambers with particular reference to air-equivalent ionization chambers. In order to ensure that similar chambers have similar sensitivities and responses the surface of the chamber bounding the active volume carries a conducting material, which may be a colloidal graphite, arranged in the form of lines so that the area of the conducting material occupies only a small proportion of the area of said surface. (U.S.)

  12. Electron-impact ionization of Pbq+ ions for q=1-10

    International Nuclear Information System (INIS)

    Loch, S.D.; Ludlow, J.A.; Pindzola, M.S.; Scheuermann, F.; Kramer, K.; Fabian, B.; Huber, K.; Salzborn, E.

    2005-01-01

    Theoretical calculations and experimental crossed-beam measurements are compared for electron-impact single ionization of Pb q+ ions for q=1-10. We compare with two main theoretical methods. First, we check against configuration-average distorted-wave calculations, which include both direct-ionization and indirect excitation-autoionization contributions. Second, for ion stages Pb + through to Pb 5+ , we calculate the dominant excitation-autoionization channels using level-resolved distorted-wave theory to evaluate the excitation cross sections. We find that for ion stages Pb + , Pb 2+ , and Pb 3+ , distorted-wave theory significantly overestimates the total-ionization cross section, due to an overestimation of the direct-ionization cross section from the 5d subshell. For ion stages Pb 4+ through to Pb 10+ there is good agreement between theory and experiment. We find evidence for significant metastable fraction in the ion beam of the experiment for ion stages Pb 2+ , Pb 3+ , Pb 4+ , Pb 5+ , and Pb 6+ . For ion stage Pb 3+ we find that the level-resolved distorted-wave calculation of the excitation autoionization results in a slight reduction of the configuration-average theoretical results, due to splitting of levels within the autoionizing configurations. We also investigate two semiempirical methods of calculating the direct-ionization cross sections: namely, the Lotz method and the binary encounter Bethe method. We find that both methods provide results which are significantly lower than the distorted-wave method for the 5d-subshell direct ionization of Pb + , Pb 2+ , and Pb 3+ . For the higher ion stages, both methods are lower than the distorted-wave direct-ionization cross-section results, trending towards the distorted-wave results as the ion stage increases

  13. Spectrum and energy levels of four-times-ionized niobium

    International Nuclear Information System (INIS)

    Kagan, D.T.; Conway, J.G.; Meinders, E.

    1981-01-01

    The 4p 6 nl spectrum of Nb 4+ was measured and analyzed. The spectrum was excited in a vacuum sliding spark source with a peak current of 800 A and a pulse width of 70 μsec. The analysis of the spectrum has extended the 12 known lines to 84 and the 10 known levels to 30. The ionization energy was calculated to be 407897 +- 40 cm -1 . There is strong evidence that the 4p 5 4d 2 configurations interacts strongly with the 4p 6 nf configuration. In addition, the hyperfine splitting of the 4p 6 6s level has been observed and measured to be 1.1 cm -1

  14. Plasma production via field ionization

    Directory of Open Access Journals (Sweden)

    C. L. O’Connell

    2006-10-01

    Full Text Available 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.

  15. One- and two-photon single ionization of 1D helium: resolving the role of individual decay channels and resonance states

    Energy Technology Data Exchange (ETDEWEB)

    Neimanns, Vera; Zimmermann, Klaus; Joerder, Felix; Buchleitner, Andreas [Albert-Ludwigs-Univ., Freiburg im Breisgau (Germany). Quantum Optics and Statistics; Lugan, Pierre [Laboratory of Theoretical Physics of Nanosystems, Institute of Theoretical Physics, EPF Lausanne (Switzerland)

    2012-07-01

    We combine the method of complex rotation and Floquet theory to analyze the multiphoton ionization of helium atoms in strong laser fields. We focus on 1D Z{sup 2+}e{sup -}e{sup -} helium to highlight the methods that allow us to extract the partial decay rates associated with various decay channels. In the regime of one-photon single ionization, we study the dependence of the partial rates associated with the singly ionized He{sup +}(N) states on the field frequency. We show that the electron-electron interaction provides couplings to higher single-ionization continua. Finally, we examine two-photon single-ionization processes, and analyze the role of the internal electronic structure of the atom, specifically the signature of resonant coupling to intermediate bound states on the decay rates.

  16. Exact results relating spin-orbit interactions in two-dimensional strongly correlated systems

    Science.gov (United States)

    Kucska, Nóra; Gulácsi, Zsolt

    2018-06-01

    A 2D square, two-bands, strongly correlated and non-integrable system is analysed exactly in the presence of many-body spin-orbit interactions via the method of Positive Semidefinite Operators. The deduced exact ground states in the high concentration limit are strongly entangled, and given by the spin-orbit coupling are ferromagnetic and present an enhanced carrier mobility, which substantially differs for different spin projections. The described state emerges in a restricted parameter space region, which however is clearly accessible experimentally. The exact solutions are provided via the solution of a matching system of equations containing 74 coupled, non-linear and complex algebraic equations. In our knowledge, other exact results for 2D interacting systems with spin-orbit interactions are not present in the literature.

  17. Ionizing radiation in hospitals

    International Nuclear Information System (INIS)

    Blok, K.; Ginkel, G. van; Leun, K. van der; Muller, H.; Oude Elferink, J.; Vesseur, A.

    1985-10-01

    This booklet dels with the risks of the use of ionizing radiation for people working in a hospital. It is subdivided in three parts. Part 1 treats the properties of ionizing radiation in general. In part 2 the various applications are discussed of ionizing radiation in hospitals. Part 3 indicates how a not completely safe situation may be improved. (H.W.). 14 figs.; 4 tabs

  18. Auger transitions in singly and multiply ionized atoms

    International Nuclear Information System (INIS)

    Mehlhorn, W.

    1978-01-01

    Some recent progress in Auger and autoionizing electron spectrometry of free metal atoms and of multiply ionized atoms is reviewed. The differences which arise between the spectra of atoms in the gaseous and the solid state are due to solid state effects. This will be shown for Cd as an example. The super Coster-Kronig transitions 3p-3d 2 (hole notation) and Coster-Kronig transitions 3p-3d 4s have been measured and compared with free-atom calculations for free Zn atoms. The experimental width GAMMA(3p)=(2.1+-0.2)eV found for the free atom agrees with the value obtained for solid Zn but is considerably smaller than the theoretical value for the free atom. Autoionizing spectra of Na following an L-shell excitation or ionization by different particles are compared and discussed. The nonisotropic angular distribution of electrons from the transition 2p 5 3s 2 2 Psub(3/2)→2p 6 +e - is compared with theoretical calculations. Two examples for Auger spectrometry of multiply ionized atoms are given: (1) excitation of neon target atoms by light and heavy ions, and (2) excitation of projectile ions Be + and B + in single gas collisions with CH 4 . A strong alignment of the excited atoms has also been found here

  19. Electron impact ionization of cycloalkanes, aldehydes, and ketones

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Dhanoj; Antony, Bobby, E-mail: bka.ism@gmail.com [Department of Applied Physics, Indian School of Mines, Dhanbad, JH 826 004 (India)

    2014-08-07

    The theoretical calculations of electron impact total ionization cross section for cycloalkane, aldehyde, and ketone group molecules are undertaken from ionization threshold to 2 keV. The present calculations are based on the spherical complex optical potential formalism and complex scattering potential ionization contribution method. The results of most of the targets studied compare fairly well with the recent measurements, wherever available and the cross sections for many targets are predicted for the first time. The correlation between the peak of ionization cross sections with number of target electrons and target parameters is also reported. It was found that the cross sections at their maximum depend linearly with the number of target electrons and with other target parameters, confirming the consistency of the values reported here.

  20. The health effects of low-dose ionizing radiation

    International Nuclear Information System (INIS)

    Dixit, A.N.; Dixit, Nishant

    2012-01-01

    It has been established by various researches, that high doses of ionizing radiation are harmful to health. There is substantial controversy regarding the effects of low doses of ionizing radiation despite the large amount of work carried out (both laboratory and epidemiological). Exposure to high levels of radiation can cause radiation injury, and these injuries can be relatively severe with sufficiently high radiation doses. Prolonged exposure to low levels of radiation may lead to cancer, although the nature of our response to very low radiation levels is not well known at this time. Many of our radiation safety regulations and procedures are designed to protect the health of those exposed to radiation occupationally or as members of the public. According to the linear no-threshold (LNT) hypothesis, any amount, however small, of radiation is potentially harmful, even down to zero levels. The threshold hypothesis, on the other hand, emphasizes that below a certain threshold level of radiation exposure, any deleterious effects are absent. At the same time, there are strong arguments, both experimental and epidemiological, which support the radiation hormesis (beneficial effects of low-level ionizing radiation). These effects cannot be anticipated by extrapolating from harmful effects noted at high doses. Evidence indicates an inverse relationship between chronic low-dose radiation levels and cancer incidence and/or mortality rates. Examples are drawn from: 1) state surveys for more than 200 million people in the United States; 2) state cancer hospitals for 200 million people in India; 3) 10,000 residents of Taipei who lived in cobalt-60 contaminated homes; 4) high-radiation areas of Ramsar, Iran; 5) 12 million person-years of exposed and carefully selected control nuclear workers; 6) almost 300,000 radon measurements of homes in the United States; and 7) non-smokers in high-radon areas of early Saxony, Germany. This evidence conforms to the hypothesis that

  1. Improved field emission properties of carbon nanotubes grown on stainless steel substrate and its application in ionization gauge

    Energy Technology Data Exchange (ETDEWEB)

    Li, Detian; Cheng, Yongjun [Science and Technology on Vacuum Technology and Physics Laboratory, Lanzhou Institute of Physics, Lanzhou 730000 (China); Wang, Yongjun, E-mail: wyjlxlz@163.com [Science and Technology on Vacuum Technology and Physics Laboratory, Lanzhou Institute of Physics, Lanzhou 730000 (China); Zhang, Huzhong [Science and Technology on Vacuum Technology and Physics Laboratory, Lanzhou Institute of Physics, Lanzhou 730000 (China); Dong, Changkun [Institute of Micro-Nano Structures and Optoelectronics, Wenzhou University, Wenzhou 325035 (China); Li, Da [Division of Advanced Nanomaterials, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215125 (China)

    2016-03-01

    Graphical abstract: - Highlights: • The high quality CNT arrays were successfully grown on conductive stainless steel substrates. • The CNT array grown on stainless steel substrate exhibited superior field emission properties. • A high vacuum level about 10–8 Pa was measured by resultant CNT-based ionization gauge. • The ionization gauge with CNT cathode demonstrated a high stability. - Abstract: Vertically aligned carbon nanotube (CNT) arrays were fabricated by chemical vapor deposition (CVD) technique on different substrates. Microstructures and field emission characteristics of the as-grown CNT arrays were investigated systematically, and its application in ionization gauge was also evaluated preliminarily. The results indicate that the as-grown CNT arrays are vertically well-aligned relating to the substrate surfaces, but the CNTs grown on stainless steel substrate are longer and more crystalline than the ones grown on silicon wafer substrate. The field emission behaviors of the as-grown CNT arrays are strongly dependent upon substrate properties. Namely, the CNT array grown on stainless steel substrate has better field emission properties, including lower turn on and threshold fields, better emission stability and repeatability, compared with the one grown on silicon wafer substrate. The superior field emission properties of the CNT array grown on stainless steel substrate are mainly attributed to low contact resistance, high thermal conductivity, good adhesion strength, etc. In addition, the metrological behaviors of ionization gauge with the CNT array grown on stainless steel substrate as an electron source were investigated, and this novel cathode ionization gauge extends the lower limit of linear pressure measurement to 10{sup −8} Pa, which is one order of magnitude lower than the result reported for the same of gauge with CNT cathode.

  2. Evaluation of the operational characteristics of a CT ionization chamber

    International Nuclear Information System (INIS)

    Maia, Ana F.; Caldas, Linda V.E.

    2006-01-01

    The most common ionization chamber used in computed tomography dosimetry is the 'pencil ionization chamber'. It is a special cylindrical dosimeter developed for attending computed tomography beams particularities. In this study, a Victoreen pencil ionization chamber was submitted to a set of tests for a detailed evaluation of its operational characteristics. Such as many kinds of detectors, especially field instruments, this ionization chamber had originally a preamplifier to keep it electrically more stable. In this study, the performance of the chamber was analyzed with the original preamplifier and after its removal, and the results were compared. The objective of the preamplifier removal was to enable connecting the chamber to other kinds of electrometers available in laboratories. The behavior of the pencil ionization chamber before and after the removal of the preamplifier was very similar, and the results obtained were always within the limits of international recommendations. The results obtained in both situations allow, if necessary, the preamplifier removal of the system without lack of precision in the measurements

  3. Ionization of EPA contaminants in direct and dopant-assisted atmospheric pressure photoionization and atmospheric pressure laser ionization.

    Science.gov (United States)

    Kauppila, Tiina J; Kersten, Hendrik; Benter, Thorsten

    2015-06-01

    Seventy-seven EPA priority environmental pollutants were analyzed using gas chromatography-mass spectrometry (GC-MS) equipped with an optimized atmospheric pressure photoionization (APPI) and an atmospheric pressure laser ionization (APLI) interface with and without dopants. The analyzed compounds included e.g., polycyclic aromatic hydrocarbons (PAHs), nitro compounds, halogenated compounds, aromatic compounds with phenolic, acidic, alcohol, and amino groups, phthalate and adipatic esters, and aliphatic ethers. Toluene, anisole, chlorobenzene, and acetone were tested as dopants. The widest range of analytes was ionized using direct APPI (66/77 compounds). The introduction of dopants decreased the amount of compounds ionized in APPI (e.g., 54/77 with toluene), but in many cases the ionization efficiency increased. While in direct APPI the formation of molecular ions via photoionization was the main ionization reaction, dopant-assisted (DA) APPI promoted ionization reactions, such as charge exchange and proton transfer. Direct APLI ionized a much smaller amount of compounds than APPI (41/77 compounds), showing selectivity towards compounds with low ionization energies (IEs) and long-lived resonantly excited intermediate states. DA-APLI, however, was able to ionize a higher amount of compounds (e.g. 51/77 with toluene), as the ionization took place entirely through dopant-assisted ion/molecule reactions similar to those in DA-APPI. Best ionization efficiency in APPI and APLI (both direct and DA) was obtained for PAHs and aromatics with O- and N-functionalities, whereas nitro compounds and aliphatic ethers were the most difficult to ionize. Halogenated aromatics and esters were (mainly) ionized in APPI, but not in APLI.

  4. Health consequences of ionizing radiation exposure

    International Nuclear Information System (INIS)

    Dalci, D.; Dorter, G.; Guclu, I.

    2004-01-01

    The increasing use of ionizing radiations all over the world induces an ever increasing interest of the professionals as well as of the whole society in health protection and the risk due to these practices. Shortly after its discovery, it was recognized that ionizing radiation can have adverse health effects and knowledge of its detrimental effects has accumulated. The fact that ionizing radiation produces biological damage has been known for many years. The biological effects of ionizing radiation for radiation protection considerations are grouped into two categories: The deterministic and the stochastic ones. Deterministic radiation effects can be clinically diagnosed in the exposed individual and occur when above a certain 'threshold' an appropriately high dose is absorbed in the tissues and organs to cause the death of a large number of cells and consequently to impair tissue or organ functions early after exposure. A clinically observable biological effect (Acute Radiation Syndromes, ARS) that occurs days to months after an acute radiation dose. ARS is a complex of acute injury manifestations that occur after a sufficiently large portion of a person's body is exposed to a high dose of ionizing radiation. Such irradiation initially injures all organs to some extent, but the timing and extent of the injury manifestations depend upon the type, rate, and dose of radiation received. Stochastic radiation effects are the chronic effects of radiation result from relatively low exposure levels delivered over long periods of time. These are sort of effects that might result from occupational exposure, or to the background exposure levels (includes radioactive pollution). Such late effects might be the development of malignant (cancerous) disease and of the hereditary consequences. These effects may be observed many years after the radiation exposure. There is a latent period between the initial radiation exposure and the development of the biological effect. In this

  5. Targeted and non-targeted effects of ionizing radiation

    Directory of Open Access Journals (Sweden)

    Omar Desouky

    2015-04-01

    Full Text Available For a long time it was generally accepted that effects of ionizing radiation such as cell death, chromosomal aberrations, DNA damage, mutagenesis, and carcinogenesis result from direct ionization of cell structures, particularly DNA, or from indirect damage through reactive oxygen species produced by radiolysis of water, and these biological effects were attributed to irreparable or misrepaired DNA damage in cells directly hit by radiation. Using linear non-threshold model (LNT, possible risks from exposure to low dose ionizing radiation (below 100 mSv are estimated by extrapolating from data obtained after exposure to higher doses of radiation. This model has been challenged by numerous observations, in which cells that were not directly traversed by the ionizing radiation exhibited responses similar to those of the directly irradiated cells. Therefore, it is nowadays accepted that the detrimental effects of ionizing radiation are not restricted only in the irradiated cells, but also to non-irradiated bystander or even distant cells manifesting various biological effects.

  6. Physiological benefits from low levels of ionizing radiation

    International Nuclear Information System (INIS)

    Luckey, T.D.

    1982-01-01

    Extensive literature indicates that minute doses of ionizing radiation benefit animal growth and development, fecundity, health and longevity. Specific improvements appear in neurologic function, growth rate and survival of young, wound healing, immune competence, and resistance to infection, radiation morbidity, and tumor induction and growth. Decreased mortality from these debilitating factors results in increased average life span following exposure to minute doses of ionizing radiation. The above phenomena suggest the possibility that ionizing radiation may be essential for life. Limited data with protozoa suggest that reproduction rates decrease when they are maintained in subambient radiation environments. This may be interpreted to be a radiation deficiency. Evidence must now be obtained to determine whether or not ionizing radiation is essential for growth, development, nutrient utilization, fecundity, health and longevity of higher animals. Whether or not ionizing radiation is found to be essential for these physiologic functions, the evidence reviewed indicates that the optimal amount of this ubiquitous agent is imperceptibly above ambient levels. (author)

  7. Miniature ionization chamber

    International Nuclear Information System (INIS)

    Alexeev, V.I.; Emelyanov, I.Y.; Ivanov, V.M.; Konstantinov, L.V.; Lysikov, B.V.; Postnikov, V.V.; Rybakov, J.V.

    1976-01-01

    A miniature ionization chamber having a gas-filled housing which accommodates a guard electrode made in the form of a hollow perforated cylinder is described. The cylinder is electrically associated with the intermediate coaxial conductor of a triaxial cable used as the lead-in of the ionization chamber. The gas-filled housing of the ionization chamber also accommodates a collecting electrode shaped as a rod electrically connected to the center conductor of the cable and to tubular members. The rod is disposed internally of the guard electrode and is electrically connected, by means of jumpers passing through the holes in the guard electrode, to the tubular members. The tubular members embrace the guard electrode and are spaced a certain distance apart along its entire length. Arranged intermediate of these tubular members are spacers secured to the guard electrode and fixing the collecting electrode throughout its length with respect to the housing of the ionization chamber

  8. Calibration of ionization chambers used in LDR brachytherapy

    International Nuclear Information System (INIS)

    Alvarez, Oscar T.B.; Caldas, Linda V.E.

    2005-01-01

    In this work was developed a calibration procedure of well-type ionization chambers used for measurements of I-125, seed type. It was used as a standard an ionization chamber Capintec CRC-15BT, with calibration certificate of the University of Wisconsin. It were calibrated two well-type ionization chambers of Capintec CRC-15R model. A source of I-125 was used in clinical use (18.5 to 7.4 MBq). The results showed that with the application of calibration factors was possible to decrease read deviate from 16% to just 1.0%

  9. Multiphoton ionization/dissociation of osmium tetroxide

    International Nuclear Information System (INIS)

    Ding, D.; Puretzky, A.A.; Compton, R.N.

    1993-01-01

    The mechanisms leading to laser multiphoton ionization and dissociation (MPI/MPD) of osmium tetroxide (OsO 4 ) have been investigated from measurements of the kinetic energies of product ions (Os + , Os 2+ , OsO + , O 2 + , O + ) and photoelectrons as a function of the laser wavelength. Neutral channels, intermediate to the dominant Os + ionization channel, such as OsO 4 →OsO 4-n +nO are examined using resonance-enhanced multiphoton ionization (REMPI) of the fast O atoms. Equipartition of the available photon energy among the fragments is observed. The wavelength dependence of the Os + ion signal suggests that one or more of the steps leading to Os + ions involve molecular ions and/or excited neutral atoms. The observed preponderance of very slow ( 2+ is shown to result primarily from REMPI of Os +

  10. Is ionizing radiation regulated more stringently than chemical carcinogens

    International Nuclear Information System (INIS)

    Travis, C.C.; Pack, S.R.; Hattemer-Frey, H.A.

    1989-01-01

    It is widely believed that United States government agencies regulate exposure to ionizing radiation more stringently than exposure to chemical carcinogens. It is difficult to verify this perception, however, because chemical carcinogens and ionizing radiation are regulated using vastly different strategies. Chemical carcinogens are generally regulated individually. Regulators consider the risk of exposure to one chemical rather than the cumulative radiation exposure from all sources. Moreover, standards for chemical carcinogens are generally set in terms of quantities released or resultant environmental concentrations, while standards for ionizing radiation are set in terms of dose to the human body. Since chemicals and ionizing radiation cannot be compared on the basis of equal dose to the exposed individual, standards regulating chemicals and ionizing radiation cannot be compared directly. It is feasible, however, to compare the two sets of standards on the basis of equal risk to the exposed individual, assuming that standards for chemicals and ionizing radiation are equivalent if estimated risk levels are equitable. This paper compares risk levels associated with current standards for ionizing radiation and chemical carcinogens. The authors do not attempt to determine whether either type of risk is regulated too stringently or not stringently enough but endeavor only to ascertain if ionizing radiation is actually regulated more strictly than chemical carcinogens

  11. New plantain (AAB) somaclones from biotechnology and ionizing radiations

    International Nuclear Information System (INIS)

    De la C. Ventura, J.; Lopez, J.; Rodriguez, S.; Gonzalez, J.; Medero, V.; Garcia, Magalys; Landa, R.; Raya, Ayme; Finalet, J.; Gonzalez, Lianet; Ramirez, Teresa; Milian, O.; Del Sol, L.; Cabrera, M; Galvez, J. R.; Reynaldo, Damisela; Montano, Nery; Torres, Marlenys; Pons, Carmen; Altanez, Sonia

    2001-01-01

    A relatively wide clonal base results to be highly important to avoid an excess of genetic uniformity. Undoubtedly, plantain is the staple crop in Cuban conditions to obtain stability at the market all the year round. Plant breeding systems developed up to now have been based on in vitro techniques to induce mutations in plantains through ionizing radiations. Three new somaclones from Zanzibar (AAB) clone have been selected and they are being delivered using sustainable and integral cropping technologies with our environmental competition. Phenologic and molecular characterizations in relation to donor clone Zanzibar are shown, as well as, field evaluations during four growing cycles in comparison with Zanzibar clone and CEMSA 3/4 clone which is the most cultivated one in the Cuban agriculture. These short stature somaclones which are high yielding are recommended to avoid losses due to plant dropping (30 %) as a result of strong winds in our conditions

  12. A compact high resolution electrospray ionization ion mobility spectrometer.

    Science.gov (United States)

    Reinecke, T; Kirk, A T; Ahrens, A; Raddatz, C-R; Thoben, C; Zimmermann, S

    2016-04-01

    Electrospray is a commonly used ionization method for the analysis of liquids. An electrospray is a dispersed nebular of charged droplets produced under the influence of a strong electrical field. Subsequently, ions are produced in a complex process initiated by evaporation of neutral solvent molecules from these droplets. We coupled an electrospray ionization source to our previously described high resolution ion mobility spectrometer with 75 mm drift tube length and a drift voltage of 5 kV. When using a tritium source for chemical gas phase ionization, a resolving power of R=100 was reported for this setup. We replaced the tritium source and the field switching shutter by an electrospray needle, a desolvation region with variable length and a three-grid shutter for injecting ions into the drift region. Preliminary measurements with tetraalkylammonium halides show that the current configuration with the electrospray ionization source maintains the resolving power of R=100. In this work, we present the characterization of our setup. One major advantage of our setup is that the desolvation region can be heated separately from the drift region so that the temperature in the drift region stays at room temperature even up to desolvation region temperatures of 100 °C. We perform parametric studies for the investigation of the influence of temperature on solvent evaporation with different ratios of water and methanol in the solvent for different analyte substances. Furthermore, the setup is operated in negative mode and spectra of bentazon with different solvents are presented. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Propagation characteristics of electromagnetic waves in dusty plasma with full ionization

    Science.gov (United States)

    Dan, Li; Guo, Li-Xin; Li, Jiang-Ting

    2018-01-01

    This study investigates the propagation characteristics of electromagnetic (EM) waves in fully ionized dusty plasmas. The propagation characteristics of fully ionized plasma with and without dust under the Fokker-Planck-Landau (FPL) and Bhatnagar-Gross-Krook (BGK) models are compared to those of weakly ionized plasmas by using the propagation matrix method. It is shown that the FPL model is suitable for the analysis of the propagation characteristics of weakly collisional and fully ionized dusty plasmas, as is the BGK model. The influence of varying the dust parameters on the propagation properties of EM waves in the fully ionized dusty plasma was analyzed using the FPL model. The simulation results indicated that the densities and average radii of dust grains influence the reflection and transmission coefficients of fully ionized dusty plasma slabs. These results may be utilized to analyze the effects of interaction between EM waves and dusty plasmas, such as those associated with hypersonic vehicles.

  14. Electrospray ionization and matrix assisted laser desorption/ionization mass spectrometry: powerful analytical tools in recombinant protein chemistry

    DEFF Research Database (Denmark)

    Andersen, Jens S.; Svensson, B; Roepstorff, P

    1996-01-01

    Electrospray ionization and matrix assisted laser desorption/ionization are effective ionization methods for mass spectrometry of biomolecules. Here we describe the capabilities of these methods for peptide and protein characterization in biotechnology. An integrated analytical strategy is presen......Electrospray ionization and matrix assisted laser desorption/ionization are effective ionization methods for mass spectrometry of biomolecules. Here we describe the capabilities of these methods for peptide and protein characterization in biotechnology. An integrated analytical strategy...... is presented encompassing protein characterization prior to and after cloning of the corresponding gene....

  15. Pregnancy and ionizing radiation

    International Nuclear Information System (INIS)

    Plataniotis, Th.N.; Nikolaou, K.I.; Syrgiamiotis, G.V.; Dousi, M.; Panou, Th.; Georgiadis, K.; Bougias, C.

    2008-01-01

    Full text: In this report there will be presented the effects of ionizing radiation at the fetus and the necessary radioprotection. The biological results on the fetus, caused by the irradiation, depend on the dose of ionizing radiation that it receives and the phase of its evolution. The imminent effects of the irradiation can cause the fetus death, abnormalities and mental retardation, which are the result of overdose. The effects are carcinogenesis and leukemia, which are relative to the acceptable irradiating dose at the fetus and accounts about 0,015 % per 1 mSv. The effects of ionizing radiation depend on the phase of the fetus evolution: 1 st phase (1 st - 2 nd week): presence of low danger; 2 nd phase (3 rd - 8 th week): for doses >100 mSv there is the possibility of dysplasia; 3 rd phase (8 th week - birth): this phase concerns the results with a percentage 0,015 % per 1 mSv. We always must follow some rules of radioprotection and especially at Classical radiation use of necessary protocols (low dose), at Nuclear Medicine use of the right radioisotope and the relative field of irradiation for the protection of the adjacent healthy tissues and at Radiotherapy extreme caution is required regarding the dose and the treatment. In any case, it is forbidden to end a pregnancy when the pregnant undergoes medical exams, in which the uterus is in the beam of irradiation. The radiographer must always discuss the possibility of pregnancy. (author)

  16. Surface ionization ion source with high current

    International Nuclear Information System (INIS)

    Fang Jinqing; Lin Zhizhou; Yu Lihua; Zhan Rongan; Huang Guojun; Wu Jianhua

    1986-04-01

    The working principle and structure of a surface ionization ion source with high current is described systematically. Some technological keypoints of the ion source are given in more detail, mainly including: choosing and shaping of the material of the surface ionizer, heating of the ionizer, distributing of working vapour on the ionizer surface, the flow control, the cooling problem at the non-ionization surface and the ion optics, etc. This ion source has been used since 1972 in the electromagnetic isotope separator with 180 deg angle. It is suitable for separating isotopes of alkali metals and rare earth metals. For instance, in the case of separating Rubidium, the maximum ion current of Rbsup(+) extracted from the ion source is about 120 mA, the maximum ion current accepted by the receiver is about 66 mA, the average ion current is more than 25 mA. The results show that our ion source have advantages of high ion current, good characteristics of focusing ion beam, working stability and structure reliability etc. It may be extended to other fields. Finally, some interesting phenomena in the experiment are disccused briefly. Some problems which should be investigated are further pointed out

  17. Ionization and bound-state relativistic quantum dynamics in laser-driven multiply charged ions

    International Nuclear Information System (INIS)

    Hetzheim, Henrik

    2009-01-01

    The interaction of ultra-strong laser fields with multiply charged hydrogen-like ions can be distinguished in an ionization and a bound dynamics regime. Both are investigated by means of numerically solving the Dirac equation in two dimensions and by a classical relativistic Monte-Carlo simulation. For a better understanding of highly nonlinear physical processes the development of a well characterized ultra-intense relativistic laser field strength has been driven forward, capable of studying e.g. the magnetic field effects of the laser resulting in an additional electron motion in the laser propagation direction. A novel method to sensitively measure these ultra-strong laser intensities is developed and employed from the optical via the UV towards the XUV frequency regime. In the bound dynamics field, the determination of multiphoton transition matrixelements has been investigated between different bound states via Rabi oscillations. (orig.)

  18. Ionization and bound-state relativistic quantum dynamics in laser-driven multiply charged ions

    Energy Technology Data Exchange (ETDEWEB)

    Hetzheim, Henrik

    2009-01-14

    The interaction of ultra-strong laser fields with multiply charged hydrogen-like ions can be distinguished in an ionization and a bound dynamics regime. Both are investigated by means of numerically solving the Dirac equation in two dimensions and by a classical relativistic Monte-Carlo simulation. For a better understanding of highly nonlinear physical processes the development of a well characterized ultra-intense relativistic laser field strength has been driven forward, capable of studying e.g. the magnetic field effects of the laser resulting in an additional electron motion in the laser propagation direction. A novel method to sensitively measure these ultra-strong laser intensities is developed and employed from the optical via the UV towards the XUV frequency regime. In the bound dynamics field, the determination of multiphoton transition matrixelements has been investigated between different bound states via Rabi oscillations. (orig.)

  19. Antiproton impact ionization of atomic hydrogen and helium

    Energy Technology Data Exchange (ETDEWEB)

    McGovern, M; Walters, H R J [Department of Applied Mathematics and Theoretical Physics, Queen' s University, Belfast BT7 INN (United Kingdom); Assafrao, D; Mohallem, J R [Laboratorio de Atomos e Moleculas Especiais, Departamento de Fisica, ICEx, Universidade Federal de Minas Gerais, P.O Box 702, 30123-970 Belo Horizonte, MG (Brazil); Whelan, Colm T, E-mail: mmcgovern06@qub.ac.u [Department of Physics, Old Dominion University, Norfolk, VA 23529-0116 (United States)

    2009-11-01

    We shall present results for antiproton ionization of H and He ranging from fully differential cross sections to total ionization. The calculations have been made in a coupled pseudostate impact parameter approximation. It will be shown that the interaction between the antiproton and the target nucleus is very important at low energies.

  20. Doubly excited helium. From strong correlation to chaos

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yuhai

    2006-03-15

    In the present dissertation, the double excitation states of helium including the autoionization decay of these states were studied experimentally and theoretically in a broad energy region, which includes the transition from strong correlation below the low single ionization thresholds (SIT) to the region of quantum chaos at energies very close to the double-ionization threshold. Two kind of experiments were performed, namely total-ion-yield measurements with the aim to observe total cross sections (TCS) and electron time-of-flight (TOF) measurements to obtain partial cross sections (PCS) as well as angular distribution parameters (ADP). Both types of measurements were performed at the third generation synchrotron radiation facility BESSY II in Berlin. The TCSs were recorded up to the SIT I{sub 15}, and they were found to be in in excellent agreement with state-of-the-art complex-rotation calculations performed recently by D. Delande. These experimental and theoretical data on the TCSs were analyzed in order to study quantum chaos in doubly excited helium, and interesting signatures of quantum chaos were found. The TOF technique allowed to measure PCSs and ADPs in the energy regions from I{sub 5} to I{sub 9} and I{sub 7}, respectively. These experimental data provide a critical assessment of theoretical models that can be used to explore the dynamics of strong correlation as well as quantum chaos in helium. In the theoretical part of this dissertation, the n- and l-specific PCSs and ADPs below I{sub 4} were calculated employing the R-matrix method. The present theoretical results agree well with a recent experimental study of l-specific PCSs below I{sub 4} by J.R. Harries et al. An analysis of patterns in the PCSs and ADPs on the basis of the present experimental and theoretical l-specific data allowed to improve the present understanding of autoionization decay dynamics in this two-electron atom. (orig.)

  1. Ionizing radiation effect study by electron beam on acrylonitrile butadiene styrene - ABS terpolymer

    International Nuclear Information System (INIS)

    Landi, Tania Regina Lourenco

    2003-01-01

    The great advantage in the researches involving development has as objective to increase significantly the quality of the products. The ABS (acrylonitrile, butadiene, styrene) resins are terpolymers formed by an elastomer and two thermoplastics amorphous components. The three different monomeric units from the terpolymer ABS contribute separately to the material characteristics exhibited. The molecular stiffness originating from polystyrene and the benzene ring hanging on the chain is responsible for the flexion module ABS. The acrylonitrile and the styrene incorporated butadiene exercises strong influence in the resistance to the impact because it reduces the bonding among them. The engineering use of this terpolymer became important due their mechanical properties and mainly, for the responses of this to tensions or deformations applied. The polymeric materials, when submitted to the ionizing radiation are modified by the transference of energy to these materials, introducing excitation and ionization of the molecules, generating chemical reactions that can produce permanent modifications in the polymeric physicochemical structure. The induced modifications can result in the polymeric material degradation or crosslinking, which can result in the improvement of some properties. This work has, as objective, to study the electron beam ionizing radiation effect, at different doses, in the properties of the polymer ABS. The studied properties were: tensile strength at break, elongation at break, Izod impact strength, flexural strength, melt flow index, Vicat softening temperature and the thermic distortion temperature. Also researches on Differential Scanning Calorimetry (DSC) and Thermogravimetric Analyses (TGA) were accomplished. From the experimental results, it was showed that for doses until 500 kGy, at 22.6 kGy/s dose rate, in the presence of air, the crosslinking process of ABS prevails. (author)

  2. Electrical pulse burnout of transistors in intense ionizing radiation

    International Nuclear Information System (INIS)

    Hartman, E.F.; Evans, D.C.

    1975-01-01

    Tests examining possible synergistic effects of electrical pulses and ionizing radiation on transistors were performed and energy/power thresholds for transistor burnout determined. The effect of ionizing radiation on burnout thresholds was found to be minimal, indicating that electrical pulse testing in the absence of radiation produces burnout-threshold results which are applicable to IEMP studies. The conditions of ionized transistor junctions and radiation induced current surges at semiconductor device terminals are inherent in IEMP studies of electrical circuits

  3. Development of special ionization chambers for a quality control program in mammography

    International Nuclear Information System (INIS)

    Silva, Jonas Oliveira da

    2013-01-01

    Mammography is an imaging method that uses X-rays. The use of ionization chambers in mammography quality control programs presents an essential role which is to verify whether the parameters of the patient exposure are correct. However, the commercial ionization chambers for dosimetry in mammography represent a high cost for small and medium size clinics that wish to have this equipment or for professionals that work with quality control programs. The innovative feature of this work was to develop ionization chambers for this purpose. In this work ionization chambers for X radiation beams in the mammography energy range were designed, constructed and characterized. The ionization chambers were tested in standard X radiation beams at the LCI/IPEN. The main characterization tests performed with the ionization chambers were: saturation curve, linearity of response, angular and energy dependence. The response stability tests of the ionization chambers were also conducted at the LCI, presenting results within 2.0 % for long-term stability. The results of the remaining tests are in accordance with international standards. These ionization chambers were also submitted to quality control tests of mammography equipment: linearity of the air kerma rates, determination of half-value layers and mean glandular doses. The results for air kerma rate linearity were less than 10 %, as recommended in international standards. The mean glandular dose obtained with the developed chambers presented values comparable to those of commercial ionization chambers tested, with an estimated variation within international standards. (author)

  4. Final 6D Muon Ionization Colling using Strong Focusing Quadrupoles

    Energy Technology Data Exchange (ETDEWEB)

    Hart, T. L. [Mississippi U.; Acosta, J. G. [Mississippi U.; Cremaldi, L. M. [Mississippi U.; Oliveros, S. J. [Mississippi U.; Summers, D. J. [Mississippi U.; Neuffer, D. V. [Fermilab

    2016-11-15

    Abstract Low emittance muon beam lines and muon colliders are potentially a rich source of BSM physics for future exper- imenters. A muon beam normalized emittance of ax,y,z = (280, 280, 1570)µm has been achieved in simulation with short solenoids and a betatron function of 3 cm. Here we use ICOOL and MAD-X to explore using a 400 MeV/c muon beam and strong focusing quadrupoles to achieve a normalized transverse emittance of 100 µm and complete 6D cooling. The low beta regions, as low as 5 mm, produced by the quadrupoles are occupied by dense, low Z absorbers, such as lithium hydride or beryllium, that cool the beam transversely. Equilibrium transverse emittance is linearly proportional to the transverse betatron function. Reverse emittance exchange with septa and/or wedges is then used to decrease transverse emittance from 100 to 25 µm at the expense of longitudinal emittance for a high energy lepton collider. Cooling challenges include chromaticity correction, ssband overlap, quadrupole acceptance, and staying in phase with RF.

  5. Saturation curves of Tandem ionization chambers for Hp(10) measurement

    International Nuclear Information System (INIS)

    Vivolo, Vitor; Caldas, Linda V.E.

    2005-01-01

    It is very important that the radiation detectors measure doses with high precision and accuracy. The verification of the standard dosemeters such as ionization chambers is a very important step in quality control programs of calibration laboratories and in radioprotection procedures. In this work the polarity effect and ionic recombination of two ionization chambers were studied. Saturation curves were obtained using two identical in shape, parallel-plate ionization chambers developed at IPEN (radioprotection level), with collecting electrodes made of different materials (to obtain different energy dependences of their responses) in standard X radiation beams of low and medium energies. The tests were performed following international standard recommendations (IEC 60731). The results show that both ionization chambers were approved in the tests; the variation on the readings were lower than 1%, for bias voltage between - 400V and + 400V. The results of the polarity tests of the ionization chambers show that the response variation is within the standard IEC 60731 limits. The determined ionic recombination agrees with the recommendation of IAEA (TRS 398). Therefore, the ionization chambers tested in this work were approved. (author)

  6. On the ionization of interstellar magnesium

    International Nuclear Information System (INIS)

    Gurzadyan, G.A.

    1977-01-01

    It has been shown that two concentric ionization zones of interstellar magnesium must exist around each star: internal, with a radius coinciding with that of the zone of hydrogen ionization Ssub(H); and external, with a radius greater than Ssub(H), by one order. Unlike interstellar hydrogen, interstellar magnesium is ionized throughout the Galaxy. It also transpires that the ionizing radiation of ordinary hot stars cannot provide for the observed high degree of ionization of interstellar magnesium. The discrepance can be eliminated by assuming the existence of circumstellar clouds or additional ionization sources of interstellar magnesium (X-ray background radiation, high-energy particles, etc.). Stars of the B5 and BO class play the main role in the formation of ionization zones of interstellar magnesium; the contribution of O class stars is negligible (<1%). (Auth.)

  7. Study on time response properties of ionization chamber in profile gauge

    International Nuclear Information System (INIS)

    Wang Zhentao; Shen Yixiong; Wang Liqiang; Hao Pengfei

    2011-01-01

    The drift time of ions in the ionization chamber was measured by means of using a shortly pulsed X-ray device and through analyzing the voltage signals on the load resistor of the chamber recorded by a digital oscilloscope. By using this method, the time response properties of the ionization chamber in the profile gauge were studied, results of ion drift time for ionization chambers with different internal structures, different voltages and different gas pressures were introduced and the sources of error were discussed. The experiment results show that the time response of ionization chamber in profile gauge meets the requirement of on-line hot strip measuring. (authors)

  8. Responses of populations of small mammals to ionizing radiation

    International Nuclear Information System (INIS)

    Kitchings, J.T.

    1978-01-01

    Studies on the responses of small mammals to ionizing radiation have, over the past 30 years, documented numerous effects on direct mortality, reproduction, the hemopoietic systems, and radionuclide metabolism. Three general findings have resulted from past efforts: (1) ionizing radiation is a factor in environmental stress, (2) the response of wild small mammals to ionizing radiation is a mosaic of varying radiosensitivities interacting with environmental variables, and (3) one of the most sensitive organismal processes to radiation is reproduction. While an excellent understanding of the biological effects resulting from high or intermediate-level radiation exposures has been developed, this is not the case for effects of low-level doses

  9. Dual ionization chamber

    International Nuclear Information System (INIS)

    Mallory, J.; Turlej, Z.

    1981-01-01

    Dual ionization chambers are provided for use with an electronic smoke detector. The chambers are separated by electrically-conductive partition. A single radiation source extends through the partition into both chambers, ionizing the air in each. The mid-point current of the device may be balanced by adjusting the position of the source

  10. SDSS-IV MaNGA: the impact of diffuse ionized gas on emission-line ratios, interpretation of diagnostic diagrams and gas metallicity measurements

    Science.gov (United States)

    Zhang, Kai; Yan, Renbin; Bundy, Kevin; Bershady, Matthew; Haffner, L. Matthew; Walterbos, René; Maiolino, Roberto; Tremonti, Christy; Thomas, Daniel; Drory, Niv; Jones, Amy; Belfiore, Francesco; Sánchez, Sebastian F.; Diamond-Stanic, Aleksandar M.; Bizyaev, Dmitry; Nitschelm, Christian; Andrews, Brett; Brinkmann, Jon; Brownstein, Joel R.; Cheung, Edmond; Li, Cheng; Law, David R.; Roman Lopes, Alexandre; Oravetz, Daniel; Pan, Kaike; Storchi Bergmann, Thaisa; Simmons, Audrey

    2017-04-01

    Diffuse ionized gas (DIG) is prevalent in star-forming galaxies. Using a sample of 365 nearly face-on star-forming galaxies observed by Mapping Nearby Galaxies at APO, we demonstrate how DIG in star-forming galaxies impacts the measurements of emission-line ratios, hence the interpretation of diagnostic diagrams and gas-phase metallicity measurements. At fixed metallicity, DIG-dominated low ΣHα regions display enhanced [S II]/Hα, [N II]/Hα, [O II]/Hβ and [O I]/Hα. The gradients in these line ratios are determined by metallicity gradients and ΣHα. In line ratio diagnostic diagrams, contamination by DIG moves H II regions towards composite or low-ionization nuclear emission-line region (LI(N)ER)-like regions. A harder ionizing spectrum is needed to explain DIG line ratios. Leaky H II region models can only shift line ratios slightly relative to H II region models, and thus fail to explain the composite/LI(N)ER line ratios displayed by DIG. Our result favours ionization by evolved stars as a major ionization source for DIG with LI(N)ER-like emission. DIG can significantly bias the measurement of gas metallicity and metallicity gradients derived using strong-line methods. Metallicities derived using N2O2 are optimal because they exhibit the smallest bias and error. Using O3N2, R23, N2 = [N II]/Hα and N2S2Hα to derive metallicities introduces bias in the derived metallicity gradients as large as the gradient itself. The strong-line method of Blanc et al. (IZI hereafter) cannot be applied to DIG to get an accurate metallicity because it currently contains only H II region models that fail to describe the DIG.

  11. Resonance ionization scheme development for europium

    Energy Technology Data Exchange (ETDEWEB)

    Chrysalidis, K., E-mail: katerina.chrysalidis@cern.ch; Goodacre, T. Day; Fedosseev, V. N.; Marsh, B. A. [CERN (Switzerland); Naubereit, P. [Johannes Gutenberg-Universität, Institiut für Physik (Germany); Rothe, S.; Seiffert, C. [CERN (Switzerland); Kron, T.; Wendt, K. [Johannes Gutenberg-Universität, Institiut für Physik (Germany)

    2017-11-15

    Odd-parity autoionizing states of europium have been investigated by resonance ionization spectroscopy via two-step, two-resonance excitations. The aim of this work was to establish ionization schemes specifically suited for europium ion beam production using the ISOLDE Resonance Ionization Laser Ion Source (RILIS). 13 new RILIS-compatible ionization schemes are proposed. The scheme development was the first application of the Photo Ionization Spectroscopy Apparatus (PISA) which has recently been integrated into the RILIS setup.

  12. Electron Impact Ionization of C60

    International Nuclear Information System (INIS)

    Duenser, B.; Lezius, M.; Scheier, P.; Deutsch, H.; Maerk, T.D.

    1995-01-01

    Absolute partial and total cross sections for the electron impact ionization of C 60 have been measured using a novel approach for the absolute calibration. The results obtained reveal not only an anomalous large parent ion cross section (as compared to the other ionization channels), but also anomalies for the production of multiply charged parent and fragment ions. This special behavior has its origin in the specific electronic and geometric structure of C 60 . Semiclassical calculations for singly charged ions support the measured data

  13. Effects of ionizing scrape-off layers on local recycling in Tore Supra pump limiter experiments

    International Nuclear Information System (INIS)

    Owen, L.W.; Hogan, J.T.; Klepper, C.C.; Mioduszewski, P.K.; Uckan, T.; Chatelier, M.; Loarer, T.

    1992-01-01

    A series of ohmic discharges with active pumping in the Tore Supra outboard pump limiter has been analyzed with the DEGAS neutrals transport code and an analysis scrape-off layer (SOL) plasma model. Pumping speed and plenum pressure measurements indicated 5--10 torr-L/s throughput with only modest effects on density (dN core /dt + source rate from ionization and dissociation of wall-desorbed molecules is seen to peak very near the radial position of the limiter throat. Consequently, a strong recycling vortex is created in the region of the limiter, with the ion flux amplified by factors of ∼2 at the outer limiter surfaces and >3 within the limiter throat. The calculations indicate that less than 30% of the pump throughput is due to first-generation ions from the core efflux, with the balance from local recycling in the strongly ionizing scrape-off layer

  14. Two-colour ionization of hydrogen

    International Nuclear Information System (INIS)

    Fifirig, M.; Cionga, A.; Florescu, V.

    1995-01-01

    The studies of different radiative processes in hydrogen continue to be of interest, as they provide a comparison basis for calculations done on many electron atoms. We consider the case of the hydrogen atom interacting simultaneously with two electromagnetic fields of incommensurable frequencies. Our attention is focused on three-photon transitions between the ground state and a final state in the continuum. The existence of compact forms for the first and second-order corrections to the wave functions of a Coulomb-field electron due to the electromagnetic field leads to compact results for the matrix element of the transitions. Numerical results are presented for the total ionization rate and the angular distribution of ejected electrons in a regime in which none of the fields is able to ionize alone the atom. (author)

  15. Effects of ionizing scrape-off layers on local recycling in Tore Supra pump limiter experiments

    International Nuclear Information System (INIS)

    Chatelier, M.; Loarer, T.

    1992-01-01

    A series of ohmic discharges with active pumping in the Tore Supra outboard pump limiter has been analyzed with the DEGAS neutrals transport code and an analytic scrape-off layer (SOL) plasma model. Pumping speed and plenum pressure measurements indicated 5-10 torr.L/s throughput with only modest effects on density. A model is developed in which large exhaust fluxes, with little attendant effect on core plasma density, are explained in terms of SOL ionization of recycled and wall-desorbed neutrals. Particle balance with active pumping and constant line density requires that the wall return flux exceed the incident flux by approximately the pump throughput in the absence of external fueling. The radial profile of the H + source rate from ionization and dissociation of wall-desorbed molecules is seen to peak very near the radial position of the limiter throat. Consequently, a strong recycling vortex is created in the region of the limiter, with the ion flux amplified by factors of 2 at the outer limiter surfaces and > 3 within the limiter throat. The calculations indicate that less than 30% of the pump throughput is due to first-generation ions from the core efflux, with the balance from local recycling in the strongly ionizing SOL

  16. Electron-Impact Ionization and Dissociative Ionization of Biomolecules

    Science.gov (United States)

    Huo, Winifred M.; Chaban, Galina M.; Dateo, Christopher E.

    2006-01-01

    It is well recognized that secondary electrons play an important role in radiation damage to humans. Particularly important is the damage of DNA by electrons, potentially leading to mutagenesis. Molecular-level study of electron interaction with DNA provides information on the damage pathways and dominant mechanisms. Our study of electron-impact ionization of DNA fragments uses the improved binary-encounter dipole model and covers DNA bases, sugar phosphate backbone, and nucleotides. An additivity principle is observed. For example, the sum of the ionization cross sections of the separate deoxyribose and phosphate fragments is in close agreement with the C3(sup prime)- and C5 (sup prime)-deoxyribose-phospate cross sections, differing by less than 5%. Investigation of tandem double lesion initiated by electron-impact dissociative ionization of guanine, followed by proton reaction with the cytosine in the Watson-Crick pair, is currently being studied to see if tandem double lesion can be initiated by electron impact. Up to now only OH-induced tandem double lesion has been studied.

  17. Near-Threshold Ionization of Argon by Positron Impact

    Science.gov (United States)

    Babij, T. J.; Machacek, J. R.; Murtagh, D. J.; Buckman, S. J.; Sullivan, J. P.

    2018-03-01

    The direct single-ionization cross section for Ar by positron impact has been measured in the region above the first ionization threshold. These measurements are compared to semiclassical calculations which give rise to a power law variation of the cross section in the threshold region. The experimental results appear to be in disagreement with extensions to the Wannier theory applied to positron impact ionization, with a smaller exponent than that calculated by most previous works. In fact, in this work, we see no difference in threshold behavior between the positron and electron cases. Possible reasons for this discrepancy are discussed.

  18. Clusters of DNA damage induced by ionizing radiation: Formation of short DNA fragments. I. Theoretical modeling

    International Nuclear Information System (INIS)

    Holley, W.R.; Chatterjee, A.

    1996-01-01

    We have developed a general theoretical model for the interaction of ionizing radiation with chromatin. Chromatin is modeled as a 30-nm-diameter solenoidal fiber composed of 20 turns of nucleosomes, 6 nucleosomes per turn. Charged-particle tracks are modeled by partitioning the energy deposition between primary track core, resulting from glancing collisions with 100 eV or less per event, and δ rays due to knock-on collisions involving energy transfers > 100 eV. A Monte Carlo simulation incorporates damages due to the following molecular mechanisms: (1) ionization of water molecules leading to the formation of circ OH, circ H, e aq , etc.; circ OH attack on sugar molecules leading to strand breaks; circ OH attack on bases; direct ionization of the sugar molecules leading to strand breaks; direct ionization of the bases. Our calculations predict significant clustering of damage both locally, over regions up to 40 hp and over regions extending to several kilobase pairs. A characteristic feature of the regional damage predicted by our model is the production of short fragments of DNA associated with multiple nearby strand breaks. Such fragments have subsequently been detected experimentally and are reported in an accompanying paper after exposure to both high- and low-LET radiation. The overall measured yields agree well quantitatively with the theoretical predictions. Our theoretical results predict the existence of a strong peak at about 85 bp, which represents the revolution period about the nucleosome. Other peaks at multiples of about 1,000 bp correspond to the periodicity of the particular solenoid model of chromatin used in these calculations. Theoretical results in combination with experimental data on fragmentation spectra may help determine the consensus or average structure of the chromatin fibers in mammalian DNA. 27 refs., 7 figs

  19. Determination of Nerve Agent Metabolites by Ultraviolet Femtosecond Laser Ionization Mass Spectrometry.

    Science.gov (United States)

    Hamachi, Akifumi; Imasaka, Tomoko; Nakamura, Hiroshi; Li, Adan; Imasaka, Totaro

    2017-05-02

    Nerve agent metabolites, i.e., isopropyl methylphosphonic acid (IMPA) and pinacolyl methylphosphonic acid (PMPA), were derivatized by reacting them with 2,3,4,5,6-pentafluorobenzyl bromide (PFBBr) and were determined by mass spectrometry using an ultraviolet femtosecond laser emitting at 267 and 200 nm as the ionization source. The analytes of the derivatized compounds, i.e., IMPA-PFB and PMPA-PFB, contain a large side-chain, and molecular ions are very weak or absent in electron ionization mass spectrometry. The use of ultraviolet femtosecond laser ionization mass spectrometry, however, resulted in the formation of a molecular ion, even for compounds such as these that contain a highly bulky functional group. The signal intensity was larger at 200 nm due to resonance-enhanced two-photon ionization. In contrast, fragmentation was suppressed at 267 nm (nonresonant two-photon ionization) especially for PMPA-PFB, thus resulting in a lower background signal. This favorable result can be explained by the small excess energy in ionization at 267 nm and by the low-frequency vibrational mode of a bulky trimethylpropyl group in PMPA.

  20. Resonance ionization in a gas cell: a feasibility study for a laser ion source

    International Nuclear Information System (INIS)

    Qamhieh, Z.N.; Vandeweert, E.; Silverans, R.E.; Duppen, P. van; Huyse, M.; Vermeeren, L.

    1992-01-01

    A laser ion source based on resonance photo-ionization in a gas cell is proposed. The gas cell, filled with helium, consists of a target chamber in which the recoil products are stopped and neutralized, and an ionization chamber where the atoms of interest are selectively ionized by the laser light. The extraction of the ions from the ionization chamber through the exit hole-skimmer setup is similar to the ion-guide system. The conditions to obtain an optimal system are given. The results of a two-step one-laser resonance photo-ionization of nickel and the first results of laser ionization in a helium buffer gas cell are presented. (orig.)

  1. Studies of Flow in Ionized Gas: Historical Perspective, Contemporary Experiments, and Applications

    International Nuclear Information System (INIS)

    Popovic, S.; Vuskovic, L.

    2007-01-01

    Since the first observations that a very small ionized fraction (order of 1 ppm) could strongly affect the gas flow, numerous experiments with partially or fully wall-free discharges have demonstrated the dispersion of shock waves, the enhancement of lateral forces in the flow, the prospects of levitation, and other aerodynamic effects with vast potential of application. A review of physical effects and observations are given along with current status of their interpretation. Special attention will be given to the physical problems of energy efficiency in generating wall-free discharges and the phenomenology of filamentary discharges. Comments and case examples are given on the current status of availability of necessary data for modelling and simulation of the aerodynamic phenomena in weakly ionized gas

  2. Electron ionization and dissociation of aliphatic amino acids

    Science.gov (United States)

    Papp, P.; Shchukin, P.; Kočíšek, J.; Matejčík, Š.

    2012-09-01

    We present experimental and theoretical study of electron ionization and dissociative ionization to the gas phase amino acids valine, leucine, and isoleucine. A crossed electron/molecular beams technique equipped with quadrupole mass analyzer has been applied to measure mass spectra and ion efficiency curves for formation of particular ions. From experimental data the ionization energies of the molecules and the appearance energies of the fragment ions were determined. Ab initio calculations (Density Functional Theory and G3MP2 methods) were performed in order to calculate the fragmentation paths and interpret the experimental data. The experimental ionization energies of parent molecules [P]+ 8.91 ± 0.05, 8.85 ± 0.05, and 8.79 ± 0.05 eV and G3MP2 ionization energies (adiabatic) of 8.89, 8.88, and 8.81 eV were determined for valine, leucine, and isoleucine, respectively, as well as the experimental and theoretical threshold energies for dissociative ionization channels. The comparison of experimental data with calculations resulted in identification of the ions as well as the neutral fragments formed in the dissociative reactions. Around 15 mass/charge ratio fragments were identified from the mass spectra by comparison of experimental appearance energies with calculated reaction enthalpies for particular dissociative reactions.

  3. Ionization of amphiphilic acidic block copolymers.

    Science.gov (United States)

    Colombani, Olivier; Lejeune, Elise; Charbonneau, Céline; Chassenieux, Christophe; Nicolai, Taco

    2012-06-28

    The ionization behavior of an amphiphilic diblock copolymer poly(n-butyl acrylate(50%)-stat-acrylic acid(50%))(100)-block-poly(acrylic acid)(100) (P(nBA(50%)-stat-AA(50%))(100)-b-PAA(100), DH50) and of its equivalent triblock copolymer P(nBA(50%)-stat-AA(50%))(100)-b-PAA(200)-b-P(nBA(50%)-stat-AA(50%))(100) (TH50) were studied by potentiometric titration either in pure water or in 0.5 M NaCl. These polymers consist of a hydrophilic acidic block (PAA) connected to a hydrophobic block, P(nBA(50%)-stat-AA(50%))(100), whose hydrophobic character has been mitigated by copolymerization with hydrophilic units. We show that all AA units, even those in the hydrophobic block could be ionized. However, the AA units within the hydrophobic block were less acidic than those in the hydrophilic block, resulting in the preferential ionization of the latter block. The preferential ionization of PAA over that of P(nBA(50%)-stat-AA(50%))(100) was stronger at higher ionic strength. Remarkably, the covalent bonds between the PAA and P(nBA(50%)-stat-AA(50%))(100) blocks in the diblock or the triblock did not affect the ionization of each block, although the self-association of the block copolymers into spherical aggregates modified the environment of the PAA blocks compared to when PAA was molecularly dispersed.

  4. Double ionization of molecule H2 in intense ultrashort laser fields

    International Nuclear Information System (INIS)

    Le, Thu-Thuy; Nguyen, Ngoc-Ty

    2015-01-01

    By solving numerically the time-dependent Schrödinger equation (TDSE), we have calculated the double ionization probability when a vibrating hydrogen molecule interacts with intense ultrashort laser pulses. The results show that in the case of vibrating nuclei the double ionization probability is higher than that of the fixed nuclei. Additionally, the double ionization probability is larger if the molecule is vibrating in a higher level. This is due to the decreasing of ionization potential when the inter-nuclei separation increases. (paper)

  5. An investigation of electronic states of some molecules and molecular cations using mass analyzed threshold ionization and photoinduced Rydberg ionization spectroscopy

    Science.gov (United States)

    Hofstein, Jason David

    1999-11-01

    Mass analyzed threshold ionization (MATI) experiments have enabled mapping of the n-dependent Rydberg state survival probability for a series of molecules. Utilizing vacuum and extreme ultraviolet (VUV/XUV) photons, one photon Rydberg manifold spectra of argon, hydrogen chloride, nitrogen, benzene, and oxygen were produced, and the prospects of photoinduced Rydberg ionization (PIRI) experiments examined. It was found that the widths of Rydberg manifolds for the molecules studied are quite different. Hydrogen chloride and nitrogen have the narrowest manifold width, followed by benzene, and then oxygen. These varying widths are most strongly correlated with the angular momentum (i.e., quantum defect) of the initially prepared Rydberg orbital. PIRI experiments required the use of a static cell, rather than a molecular jet assembly, for the more efficient production of higher amounts of VUV/XUV radiation, and hence more Rydberg signal needed to observe PIRI. Armed with the ability to produce tunable VUV/XUV radiation, and to determine the feasibility of a PIRI experiment, the MATI and fragment PIRI spectra of trans-1,3-butadiene (BD) were recorded. The MATI spectrum is vibrationally resolved and was analyzed with the help of ab initio calculations and other published results. The fragment PIRI spectrum of the Aproduction of C3H3+ dominates, but at higher photon energies, C2H4 + is also produced. The production of each fragment showed a definite PIRI wavelength dependence.

  6. Laser post-ionization secondary neutral mass spectroscopy

    International Nuclear Information System (INIS)

    Gruen, D.M.; Pellin, M.J.; Calaway, W.F.; Young, C.E.

    1987-01-01

    Three different instruments using laser ionization techniques will be described. Results from the SARISA instrument with a demonstrated figure of merit of .05 (atoms detected/atoms sputtered) for resonance ionization; detection of Fe at the sub-part-per-billion level in ultrapure Si; and features of the instrument such as energy and angle refocusing time-of-flight (EARTOF) mass spectrometer and multiplexing for simultaneous detection of secondary ions and neutrals. 12 refs., 3 figs

  7. Collective-field-corrected strong field approximation for laser-irradiated metal clusters

    International Nuclear Information System (INIS)

    Keil, Th; Bauer, D

    2014-01-01

    The strong field approximation (SFA) formulated in terms of so-called ‘quantum orbits’ led to much insight into intense-laser driven ionization dynamics. In plain SFA, the emitted electron is treated as a free electron in the laser field alone. However, with improving experimental techniques and more advanced numerical simulations, it becomes more and more obvious that the plain SFA misses interesting effects even on a qualitative level. Examples are holographic side lobes, the low-energy structure, radial patterns in photoelectron spectra at low kinetic energies and strongly rotated angular distributions. For this reason, increasing efforts have been recently devoted to Coulomb corrections of the SFA. In the current paper, we follow a similar line but consider ionization of metal clusters. It is known that photoelectrons from clusters can be much more energetic than those emitted from atoms or small molecules, especially if the Mie resonance of the expanding cluster is evoked. We develop a SFA that takes the collective field inside the cluster via the simple rigid-sphere model into account. Our approach is based on field-corrected quantum orbits so that the acceleration process (or any other spectral feature of interest) can be investigated in detail. (paper)

  8. Design, construction and characterization of special ionization chambers for X radiation beams monitoring

    International Nuclear Information System (INIS)

    Yoshizumi, Maira Tiemi

    2010-01-01

    X radiation equipment may show fluctuations in the radiation beam intensity, as they are connected to the power net. These intensity variations can, in turn, modify the air kerma rate produced by this radiation beam. In a calibration laboratory, where radiation detectors (from clinics and hospital services) are calibrated, variations in the radiation beam intensity may cause an error in the absorbed dose determination. The monitor ionization chambers are used to verify the radiation beam intensity constancy, and to provide a correction for possible fluctuations. In this work, monitor ionization chambers for X radiation beams were designed, assembled and characterized. The developed ionization chambers have an innovative design, ring-shaped, with aluminium or graphite electrodes. These ring-shaped ionization chambers have the advantage of not interfering in the direct radiation beams. A double-volume ionization chamber with graphite electrodes was also developed. This ionization chamber is similar to the commercial monitor ionization chamber used in the Calibration Laboratory of the Instituto de Pesquisas Energeticas e Nucleares. All developed ionization chambers were tested in several standardized radiation beams and their performances were compared with those of commercial ionization chambers. The results show that two of the four ionization chambers developed showed performance comparable to that of the commercial ionization chambers tested. Besides presenting good results, the ionization chambers were designed and manufactured using low cost materials, which are easily found on the Brazilian market. (author)

  9. Effects of molecular orientation in the laser ionization of molecules

    International Nuclear Information System (INIS)

    Xinhua Xie; Gerald Jordan; Christopher Ede; Armin Scrinzi

    2006-01-01

    Complete test of publication follows. Time-dependent electron momentum distributions are calculated during ionization of linear molecules by a strong laser pulse and upon recollision. For typical experimental laser parameters, we find a strong influence of molecular orientation and initial state symmetry on the total ionization rates and also on momentum distributions, compared to which the effect of electron correlation is less important for simple molecules. The dynamics of electron release and subsequent recollision with the parent ion largely determines the time-frequency structure of harmonic radiation, which underlies the generation of attosecond XUV pulses and the time-resolved imaging techniques for the electronic structure of molecules. In the present work, the effects of orientation and initial orbital symmetry are investigated by solving the time-dependent Schroedinger equation for a two-dimensional diatomic molecule in the single-active electron approximation. As in the presence of strong external fields recolliding electrons cannot be easily separated from bound electrons, the electron wave packet is probed at some distance from where all electrons can be safety considered as detached. We find that momentum distributions strongly depend on molecular size, orientation of the molecular axis, and node structure of the initial state. In order to determine the momentum spectra at the time of electron release and upon recollision, we classically propagate the Wigner distributions of probed wavepackets backward and forward in time, respectively. We find that the times of peak recollision current can vary strongly with the orientation of the molecule. Moreover, correlation effects on the electron spectra are included using the multi-configuration time-dependent Hartree-Fock method. The calculations are performed in three spatial dimensions with the restriction to cylindrical symmetry, where the molecule is aligned with the laser field. Correlation is studied

  10. Optimum conditions for the determination of ionization potentials, appearance potentials and fine structure in ionization efficiency curves using edd technique

    International Nuclear Information System (INIS)

    Selim, Ezzat T.; El-Kholy, S.B.; Zahran, Nagwa F.

    1978-01-01

    The optimum conditions for determining ionization potentials as well as fine structure in electron impact ionization efficiency curves are studied using energy distribution difference technique. Applying these conditions to Ar + , Kr + , CO + 2 and N + from N 2 , very good agreement is obtained when compared with results determined by other techniques including UV spectroscopy. The merits and limitation of the technique are also discussed

  11. An easy way to obtain strong duality results in linear, linear semidefinite and linear semi-infinite programming

    NARCIS (Netherlands)

    Pop, P.C.; Still, Georg J.

    1999-01-01

    In linear programming it is known that an appropriate non-homogeneous Farkas Lemma leads to a short proof of the strong duality results for a pair of primal and dual programs. By using a corresponding generalized Farkas lemma we give a similar proof of the strong duality results for semidefinite

  12. Specific cationic emission of cisplatin following ionization by swift protons

    International Nuclear Information System (INIS)

    Moretto-Capelle, P.; Champeaux, J.P.; Deville, C.; Sence, M.; Cafarelli, P.

    2016-01-01

    We have investigated collision-induced ionization and fragmentation by 100 keV protons of the radio sensitizing molecule cisplatin, which is used in cancer treatments. A large emission of HCl"+ and NH_2"+ is observed, but surprisingly, no cationic fragments containing platinum are detected, in contrast to ionization-dissociation induced by electronic collision. Theoretical investigations show that the ionization processes take place on platinum and on chlorine atoms. We propose new ionization potentials for cisplatin. Dissociation limits corresponding to the measured fragmentation mass spectrum have been evaluated and the theoretical results show that the non-observed cationic fragments containing platinum are mostly associated with low dissociation energies. We have also investigated the reaction path for the hydrogen transfer from the NH_3 group to the Cl atom, as well as the corresponding dissociation limits from this tautomeric form. Here again the cations containing platinum correspond to lower dissociation limits. Thus, the experimental results suggest that excited states, probably formed via inner-shell ionization of the platinum atom of the molecule, correlated to higher dissociation limits are favored. (authors)

  13. Specific cationic emission of cisplatin following ionization by swift protons

    Science.gov (United States)

    Moretto-Capelle, Patrick; Champeaux, Jean-Philippe; Deville, Charlotte; Sence, Martine; Cafarelli, Pierre

    2016-05-01

    We have investigated collision-induced ionization and fragmentation by 100 keV protons of the radio sensitizing molecule cisplatin, which is used in cancer treatments. A large emission of HCl+ and NH2+ is observed, but surprisingly, no cationic fragments containing platinum are detected, in contrast to ionization-dissociation induced by electronic collision. Theoretical investigations show that the ionization processes take place on platinum and on chlorine atoms. We propose new ionization potentials for cisplatin. Dissociation limits corresponding to the measured fragmentation mass spectrum have been evaluated and the theoretical results show that the non-observed cationic fragments containing platinum are mostly associated with low dissociation energies. We have also investigated the reaction path for the hydrogen transfer from the NH3 group to the Cl atom, as well as the corresponding dissociation limits from this tautomeric form. Here again the cations containing platinum correspond to lower dissociation limits. Thus, the experimental results suggest that excited states, probably formed via inner-shell ionization of the platinum atom of the molecule, correlated to higher dissociation limits are favored.

  14. The Possible Role of Penning Ionization Processes in Planetary Atmospheres

    Directory of Open Access Journals (Sweden)

    Stefano Falcinelli

    2015-03-01

    Full Text Available In this paper we suggest Penning ionization as an important route of formation for ionic species in upper planetary atmospheres. Our goal is to provide relevant tools to researchers working on kinetic models of atmospheric interest, in order to include Penning ionizations in their calculations as fast processes promoting reactions that cannot be neglected. Ions are extremely important for the transmission of radio and satellite signals, and they govern the chemistry of planetary ionospheres. Molecular ions have also been detected in comet tails. In this paper recent experimental results concerning production of simple ionic species of atmospheric interest are presented and discussed. Such results concern the formation of free ions in collisional ionization of H2O, H2S, and NH3 induced by highly excited species (Penning ionization as metastable noble gas atoms. The effect of Penning ionization still has not been considered in the modeling of terrestrial and extraterrestrial objects so far, even, though metastable helium is formed by radiative recombination of He+ ions with electrons. Because helium is the second most abundant element of the universe, Penning ionization of atomic or molecular species by He*(23S1 is plausibly an active route of ionization in relatively dense environments exposed to cosmic rays.

  15. Collective acceleration investigations with the ionization front accelerator

    International Nuclear Information System (INIS)

    Olson, C.L.; Poukey, J.W.; VanDevender, J.P.; Owyoung, A.; Pearlman, J.S.

    1977-01-01

    Part I of a three part program to demonstrate feasibility of the Ionization Front Accelerator (IFA) has been completed and is successful. Experiments describing intense relativistic electron beam (IREB) propagation in Cs are reported. The threshold pressure for electron beam ionization of Cs is found to agree with earlier theoretical predictions. These results experimentally establish Cs as a feasible working gas for the IFA. Numerical simulation results are also reported which demonstrate controlled potential well motion and collective ion acceleration with the IFA

  16. Physicochemical processes occurring under action of ionizing radiation in sarcophagus

    International Nuclear Information System (INIS)

    Azarov, S.I.; Pshenichny, V.A.; Vilenskaya, L.N.; Korchevnaya, O.V.; Martseniuk, L.S.

    1998-01-01

    The result of analysis of environment ionization process inside Sarcophagus owing to alpha-, beta- and gamma-radiation processes with forming of ions. It is shown that as a result of ionization and physicochemical transformations gaseous mixtures, which are dangerous for personnel's health and can influence upon general technical safety of Sarcophagus, can release into atmosphere

  17. A prototype ionization profile monitor for RHIC

    International Nuclear Information System (INIS)

    Connolly, R.; Cameron, P.; Ryan, W.

    1997-01-01

    Transverse beam profiles in the Relativistic Heavy-Ion Collider (RHIC) will be measured with ionization profile monitors (IPM's). Each IPM collects and measures the distribution of electrons in the beamline resulting from residual gas ionization during bunch passage. The electrons are swept transversely from the beamline and collected on strip anodes oriented parallel to the beam axis. At each bunch passage the charge pulses are amplified, integrated, and digitized for display as a profile histogram. A prototype detector was tested in the injection line during the RHIC Sextant Test. This paper describes the detector and gives results from the beam tests

  18. Ionizing radiation decreases human cancer mortality rates

    International Nuclear Information System (INIS)

    Luckey, T.D.

    1997-01-01

    Information from nine studies with exposed nuclear workers and military observers of atmospheric bomb explosions confirms the results from animal studies which showed that low doses of ionizing radiation are beneficial. The usual ''healthy worker effect'' was eliminated by using carefully selected control populations. The results from 13 million person-years show the cancer mortality rate of exposed persons is only 65.6% that of carefully selected unexposed controls. This overwhelming evidence makes it politically untenable and morally wrong to withhold public health benefits of low dose irradiation. Safe supplementation of ionizing radiation should become a public health service. (author)

  19. A prototype ionization profile monitor for RHIC

    Energy Technology Data Exchange (ETDEWEB)

    Connolly, R.; Cameron, P.; Ryan, W. [and others

    1997-07-01

    Transverse beam profiles in the Relativistic Heavy-Ion Collider (RHIC) will be measured with ionization profile monitors (IPM`s). Each IPM collects and measures the distribution of electrons in the beamline resulting from residual gas ionization during bunch passage. The electrons are swept transversely from the beamline and collected on strip anodes oriented parallel to the beam axis. At each bunch passage the charge pulses are amplified, integrated, and digitized for display as a profile histogram. A prototype detector was tested in the injection line during the RHIC Sextant Test. This paper describes the detector and gives results from the beam tests.

  20. Study of the strongly ionized medium in active galactic n ('Warm Absorber'): multi-wavelength modelling and plasma diagnostics in the X-ray spectral range

    International Nuclear Information System (INIS)

    Porquet, Delphine

    1999-01-01

    The so-called 'Warm Absorber' medium is observed in the central region of Active Galactic Nuclei and particularly in Seyfert l galaxies. lt is mainly characterized by O(VII) and O(VIII) absorption edges detected in the soft X-rays. Its study (modelization and observation) is an important key tool to understand Active Galactic Nuclei. The work presented here consists in modelling the Warm Absorber, and in developing X-ray spectroscopy diagnostics to constrain the physical parameters of any hot medium such as the Warm Absorber. The physical parameters of the Warm Absorber (density, temperature, ionization processes..) are difficult to determine only on the basis of present X-ray data. In particular, the value of the density cannot be derived only from the modelling of the resonance lines and of the soft X-ray absorption edges since there are almost insensitive to the density in the range of values expected for the Warm Absorber. lt is why we have developed diagnostic methods based on a multi-wavelength approach. The modelling is made with two complementary computational codes: PEGAS, and IRIS which takes into account the most accurate atomic data. With these two codes, we have modelled several types of plasma ionisation processes (photoionized plasmas and/or collisional). Results for the Warm Absorber were compared to multi-wavelength observations (mainly the optical iron coronal lines [Fe X] 6375 Angstroms, [Fe XI] 7892 Angstroms, and [Fe XIV] 5303 Angstroms). The proposed method has allowed to show that the Warm Absorber could be responsible of the emission of these lines totally or partially. All models of the Warm Absorber producing coronal line equivalent widths larger than observed were ruled out. This strongly constrains the physical parameters of the Warm Absorber, and particularly its density (n H ≥10 10 cm -3 ). The new generation of X-ray satellites (Chandra/AXAF, XMM...) will produce spectra at high spectral resolution and high sensitivity

  1. Motion of ionizing electric-field solitons in a bounded plasma

    International Nuclear Information System (INIS)

    Lagar'kov, A.; Rutkevich, I.

    1981-01-01

    A theory is derived for the motion of fast ionization waves along a plane slab of a weakly ionized plasma. The properties of the ionization wave are shown to be closely related to the motion of a two-dimensional surface-charge wave along the slab boundaries. As a result, the ionization wave is quite different from a one-dimensional wave. A quasi-one-dimensional description is used for the wave motion, in which the initial equations are averaged over the transverse coordinate. The relationship between the normal component of the current density at the plasma boundary and the amplitude of the electric potential from the linear theory for a surface wave is used to close the system of averaged equations. Self-similar solutions are derived for these equations; the solutions describe space-charge solitons and electric-field solitons which ionize the plasma. The theory is used to explain the motion of fast ionization waves in long discharge tubes

  2. Threshold Law For Positron Impact Ionization of Atoms

    International Nuclear Information System (INIS)

    Ihra, W.; Mota-Furtado, F.; OMahony, P.F.; Macek, J.H.; Macek, J.H.

    1997-01-01

    We demonstrate that recent experiments for positron impact ionization of He and H 2 can be interpreted by extending Wannier theory to higher energies. Anharmonicities in the expansion of the three-particle potential around the Wannier configuration give rise to corrections in the threshold behavior of the breakup cross section. These corrections are taken into account perturbatively by employing the hidden crossing theory. The resulting threshold law is σ(E)∝E 2.640 exp[ -0.73√(E)] . The actual energy range for which the Wannier law is valid is found to be smaller for positron impact ionization than for electron impact ionization. copyright 1997 The American Physical Society

  3. Lyman-continuum leakage as dominant source of diffuse ionized gas in the Antennae galaxy

    Science.gov (United States)

    Weilbacher, Peter M.; Monreal-Ibero, Ana; Verhamme, Anne; Sandin, Christer; Steinmetz, Matthias; Kollatschny, Wolfram; Krajnović, Davor; Kamann, Sebastian; Roth, Martin M.; Erroz-Ferrer, Santiago; Marino, Raffaella Anna; Maseda, Michael V.; Wendt, Martin; Bacon, Roland; Dreizler, Stefan; Richard, Johan; Wisotzki, Lutz

    2018-04-01

    The Antennae galaxy (NGC 4038/39) is the closest major interacting galaxy system and is therefore often studied as a merger prototype. We present the first comprehensive integral field spectroscopic dataset of this system, observed with the MUSE instrument at the ESO VLT. We cover the two regions in this system which exhibit recent star formation: the central galaxy interaction and a region near the tip of the southern tidal tail. In these fields, we detect HII regions and diffuse ionized gas to unprecedented depth. About 15% of the ionized gas was undetected by previous observing campaigns. This newly detected faint ionized gas is visible everywhere around the central merger, and shows filamentary structure. We estimate diffuse gas fractions of about 60% in the central field and 10% in the southern region. We are able to show that the southern region contains a significantly different population of HII regions, showing fainter luminosities. By comparing HII region luminosities with the HST catalog of young star clusters in the central field, we estimate that there is enough Lyman-continuum leakage in the merger to explain the amount of diffuse ionized gas that we detect. We compare the Lyman-continuum escape fraction of each HII region against emission line ratios that are sensitive to the ionization parameter. While we find no systematic trend between these properties, the most extreme line ratios seem to be strong indicators of density bounded ionization. Extrapolating the Lyman-continuum escape fractions to the southern region, we conclude that simply from the comparison of the young stellar populations to the ionized gas there is no need to invoke other ionization mechanisms than Lyman-continuum leaking HII regions for the diffuse ionized gas in the Antennae. FITS images and Table of HII regions are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/611/A95 and at http://muse-vlt.eu/science/antennae/

  4. Study of the multiple ionization in the ion-atom collisions with highly charged sulfur as well as with neutral and lowly charged fluorine projectiles

    International Nuclear Information System (INIS)

    Konrad, J.

    1986-01-01

    With the collisional systems 115 MeV S +Q (Q=+13, +15, +16) on He, Ne, Ar, and Kr as well as 4 MeV F +Q (Q=-1, 0, +1) on Ne the multiple ionization in the ion-atom collision was studied. With the collisional system 4 MeV F +Q on Ne the multiple ionization of target and projectile was studied by coincidence measurement between the recoil ions and projectiles with the charge state Q' after the collision (Q'=-1 to +3). In the pure ionization (no change of the projectile charge) the measured ionization cross sections for the single positive and negative charged projectile are equally large, those of the neutral F projectiles are lower. The comparison with the point particles protons and electrons resulted that the ionization cross sections of the F projectiles are larger and more strongly higher charged recoil ions are produced. The measured ionization cross sections of the F projectile are larger than those of the Ne target atom which is to be reduced to the lower ionization energies of the F projectile. With the highly charged S projectiles the multiple ionization with capture into the projectile was studied. By the measurement of triple coincidcences between recoil ions, projectiles, and SKX-radiation the cases with and without capture into the K shell can be discriminated. The charge distribution with is shifted against that without capture into the K shell to higher charges. This shift is to be reduced to the decay of autoionization states which arise by the capture into the K shell. (orig./HSI) [de

  5. Radiation and genetic consequences of ionizing radiation on population of Pinus sylvestris L. within the zone of the Chernobyl NPP

    International Nuclear Information System (INIS)

    Fedotov, I.S.; Kal'chenko, V.A.; Igonina, E.V.; Rubanovich, A.V.

    2006-01-01

    Main results of the nineteen year monitoring of genetic radiation effects of ionizing radiations on pines of forest plantation in the zone of the Chernobylsk NPP accident are presented. It is shown that the acute ionizing irradiation at radiation doses >1 Gy induces the formation of morphosis and depressed growth, and at doses >2 Gy, the reproductive ability of pines is declined. The radiobiological parameters have practically linear dose-dependence relationship. The acute irradiation at dose of 0.5 Gy induces cytogenetic and genetic effects that are significantly higher than corresponding control values. The relationship between the cytogenetic effects and the absorbed dose is exponential. The dependence of mutation frequency at specific loci on the absorbed dose is described by a nonlinear curve. The results of the cytogenetic analysis of seedlings obtained from seeds annually collected in zones of slight, moderate and strong damages of pines are presented [ru

  6. The ionization mechanisms in direct and dopant-assisted atmospheric pressure photoionization and atmospheric pressure laser ionization.

    Science.gov (United States)

    Kauppila, Tiina J; Kersten, Hendrik; Benter, Thorsten

    2014-11-01

    A novel, gas-tight API interface for gas chromatography-mass spectrometry was used to study the ionization mechanism in direct and dopant-assisted atmospheric pressure photoionization (APPI) and atmospheric pressure laser ionization (APLI). Eight analytes (ethylbenzene, bromobenzene, naphthalene, anthracene, benzaldehyde, pyridine, quinolone, and acridine) with varying ionization energies (IEs) and proton affinities (PAs), and four common APPI dopants (toluene, acetone, anisole, and chlorobenzene) were chosen. All the studied compounds were ionized by direct APPI, forming mainly molecular ions. Addition of dopants suppressed the signal of the analytes with IEs above the IE of the dopant. For compounds with suitable IEs or Pas, the dopants increased the ionization efficiency as the analytes could be ionized through dopant-mediated gas-phase reactions, such as charge exchange, proton transfer, and other rather unexpected reactions, such as formation of [M + 77](+) in the presence of chlorobenzene. Experiments with deuterated toluene as the dopant verified that in case of proton transfer, the proton originated from the dopant instead of proton-bound solvent clusters, as in conventional open or non-tight APPI sources. In direct APLI using a 266 nm laser, a narrower range of compounds was ionized than in direct APPI, because of exceedingly high IEs or unfavorable two-photon absorption cross-sections. Introduction of dopants in the APLI system changed the ionization mechanism to similar dopant-mediated gas-phase reactions with the dopant as in APPI, which produced mainly ions of the same form as in APPI, and ionized a wider range of analytes than direct APLI.

  7. Electron-electron Thomas peak in fast transfer ionization

    International Nuclear Information System (INIS)

    Tolmanov, S. G.; McGuire, J. H.

    2000-01-01

    ''Thomas process'' is a name used for a family of singular two-step processes that can lead to electron transfer. The Thomas process of the ''second kind,'' occurring in reactions with both transfer and ionization, utilizes the e-e scattering in the second step, so this Thomas process requires the dynamics of the electron-electron interaction. We calculate numerically the second order element of an S matrix and corresponding cross sections for the transfer ionization process. We find that the position and shape of the Thomas peak depend on both electron-electron and the electron-nucleus interaction. Also the direct and exchange amplitudes are equal at the peak position. We test the peaking approximation used for transfer ionization. Our results can be compared to experimental results for p + +He→H+He 2+ +e - . (c) 2000 The American Physical Society

  8. Mass spectrometry of solid samples in open air using combined laser ionization and ambient metastable ionization

    International Nuclear Information System (INIS)

    He, X.N.; Xie, Z.Q.; Gao, Y.; Hu, W.; Guo, L.B.; Jiang, L.; Lu, Y.F.

    2012-01-01

    Mass spectrometry of solid samples in open air was carried out using combined laser ionization and metastable ionization time-of-flight mass spectrometry (LI-MI-TOFMS) in ambient environment for qualitative and semiquantitative (relative analyte information, not absolute information) analysis. Ambient metastable ionization using a direct analysis in realtime (DART) ion source was combined with laser ionization time-of-flight mass spectrometry (LI-TOFMS) to study the effects of combining metastable and laser ionization. A series of metallic samples from the National Institute of Standards and Technology (NIST 494, 495, 498, 499, and 500) and a pure carbon target were characterized using LI-TOFMS in open air. LI-MI-TOFMS was found to be superior to laser-induced breakdown spectroscopy (LIBS). Laser pulse energies between 10 and 200 mJ at the second harmonic (532 nm) of an Nd:YAG laser were applied in the experiment to obtain a high degree of ionization in plasmas. Higher laser pulse energy improves signal intensities of trace elements (such as Fe, Cr, Mn, Ni, Ca, Al, and Ag). Data were analyzed by numerically calculating relative sensitivity coefficients (RSCs) and limit of detections (LODs) from mass spectrometry (MS) and LIBS spectra. Different parameters, such as boiling point, ionization potential, RSC, LOD, and atomic weight, were shown to analyze the ionization and MS detection processes in open air.

  9. Generation of polypeptide-templated gold nanoparticles using ionizing radiation.

    Science.gov (United States)

    Walker, Candace Rae; Pushpavanam, Karthik; Nair, Divya Geetha; Potta, Thrimoorthy; Sutiyoso, Caesario; Kodibagkar, Vikram D; Sapareto, Stephen; Chang, John; Rege, Kaushal

    2013-08-13

    Ionizing radiation, including γ rays and X-rays, are high-energy electromagnetic radiation with diverse applications in nuclear energy, astrophysics, and medicine. In this work, we describe the use of ionizing radiation and cysteine-containing elastin-like polypeptides (C(n)ELPs, where n = 2 or 12 cysteines in the polypeptide sequence) for the generation of gold nanoparticles. In the presence of C(n)ELPs, ionizing radiation doses higher than 175 Gy resulted in the formation of maroon-colored gold nanoparticle dispersions, with maximal absorbance at 520 nm, from colorless metal salts. Visible color changes were not observed in any of the control systems, indicating that ionizing radiation, gold salt solution, and C(n)ELPs were all required for nanoparticle formation. The hydrodynamic diameters of nanoparticles, determined using dynamic light scattering, were in the range of 80-150 nm, while TEM imaging indicated the formation of gold cores 10-20 nm in diameter. Interestingly, C2ELPs formed 1-2 nm diameter gold nanoparticles in the absence of radiation. Our results describe a facile method of nanoparticle formation in which nanoparticle size can be tailored based on radiation dose and C(n)ELP type. Further improvements in these polypeptide-based systems can lead to colorimetric detection of ionizing radiation in a variety of applications.

  10. MAGNETIC RECONNECTION IN NON-EQUILIBRIUM IONIZATION PLASMA

    International Nuclear Information System (INIS)

    Imada, S.; Shimizu, T.; Murakami, I.; Watanabe, T.; Hara, H.

    2011-01-01

    We have studied the effect of time-dependent ionization and the recombination processes on magnetic reconnection in the solar corona. Petschek-type steady reconnection, in which the magnetic energy is mainly converted at the slow-mode shocks, was assumed. We carried out the time-dependent ionization calculation in the magnetic reconnection structure. We only calculated the transient ionization of iron; the other species were assumed to be in ionization equilibrium. The intensity of line emissions at specific wavelengths was also calculated for comparison with Hinode or other observations in future. We found the following: (1) iron is mostly in non-equilibrium ionization in the reconnection region; (2) the intensity of line emission estimated by the time-dependent ionization calculation is significantly different from that determined from the ionization equilibrium assumption; (3) the effect of time-dependent ionization is sensitive to the electron density in the case where the electron density is less than 10 10 cm –3 ; (4) the effect of thermal conduction lessens the time-dependent ionization effect; and (5) the effect of radiative cooling is negligibly small even if we take into account time-dependent ionization.

  11. Detoxification of snake venom using ionizing radiation

    International Nuclear Information System (INIS)

    Rogero, J.R.; Nascimento, N.

    1995-01-01

    It is generally recognized that energy absorbed by ionizing radiation (gamma rays) can inactivate biological material in tow ways. A direct effects occurs when the primary event, i.e., ionization, is produced in the molecule itself. This is the case when a compound is irradiated in dry state. When a compound is irradiated in a solution, the indirect effect joins the direct. Since water is the most abundant constituent of biological material, it is important to consider the species produced by excitation and ionization of water itself, and the reaction of these species with the target molecules of biological importance. This indirect effect results from the reactions among the studied molecules and the products of radiation interaction with water or other solvents. Highly reactive compounds, the so-called free radicals, which are formed many reactions among themselves, with the dissolved gas, and with other molecules in the solution. With water, the excitation is less important than ionization which is followed within picosecond by the formation of free hydroxyl radicals and hydrated electrons. Alexander and Hamilton showed that irradiation of proteins has revealed damage to aminoacid side chains, production of new groups, splitting of peptide bonds and formation of intramolecular and intermolecular cross-links. With these results it would be possible to use ionizing radiation to change those proteins molecules in order to improve some of their properties according to the necessity. On the other hand, it is recognized that venoms in general are poorly immunogenic, yet fairly toxic. This cause problems because serotherapy is the treatment of choice in snakebite envenomations, and horse antivenom availability is dependent upon. (author)

  12. Effects of ionizing radiation on modern ion exchange materials

    International Nuclear Information System (INIS)

    Marsh, S.F.; Pillay, K.K.S.

    1993-10-01

    We review published studies of the effects of ionizing radiation on ion exchange materials, emphasizing those published in recent years. A brief overview is followed by a more detailed examination of recent developments. Our review includes styrene/divinylbenzene copolymers with cation-exchange or anion-exchange functional groups, polyvinylpyridine anion exchangers, chelating resins, multifunctional resins, and inorganic exchangers. In general, strong-acid cation exchange resins are more resistant to radiation than are strong-base anion exchange resins, and polyvinylpyridine resins are more resistant than polystyrene resins. Cross-linkage, salt form, moisture content, and the surrounding medium all affect the radiation stability of a specific exchanger. Inorganic exchangers usually, but not always, exhibit high radiation resistance. Liquid ion exchangers, which have been used so extensively in nuclear processing applications, also are included

  13. Field-dependent molecular ionization and excitation energies: Implications for electrically insulating liquids

    Directory of Open Access Journals (Sweden)

    N. Davari

    2014-03-01

    Full Text Available The molecular ionization potential has a relatively strong electric-field dependence as compared to the excitation energies which has implications for electrical insulation since the excited states work as an energy sink emitting light in the UV/VIS region. At some threshold field, all the excited states of the molecule have vanished and the molecule is a two-state system with the ground state and the ionized state, which has been hypothesized as a possible origin of different streamer propagation modes. Constrained density-functional theory is used to calculate the field-dependent ionization potential of different types of molecules relevant for electrically insulating liquids. The low singlet-singlet excitation energies of each molecule have also been calculated using time-dependent density functional theory. It is shown that low-energy singlet-singlet excitation of the type n → π* (lone pair to unoccupied π* orbital has the ability to survive at higher fields. This type of excitation can for example be found in esters, diketones and many color dyes. For alkanes (as for example n-tridecane and cyclohexane on the other hand, all the excited states, in particular the σ → σ* excitations vanish in electric fields higher than 10 MV/cm. Further implications for the design of electrically insulating dielectric liquids based on the molecular ionization potential and excitation energies are discussed.

  14. Ionization front accelerator

    International Nuclear Information System (INIS)

    Olson, C.L.

    1975-01-01

    In a recently proposed linear collective accelerator, ions are accelerated in a steep, moving potential well created at the head of an intense relativistic electron beam. The steepness of the potential well and its motion are controlled by the external ionization of a suitable background gas. Calculations concerning optimum choices for the background gas and the ionization method are presented; a two-step photoionization process employing Cs vapor is proposed. In this process, a super-radiant light source is used to excite the gas, and a UV laser is used to photoionize the excited state. The appropriate line widths and coupled ionization growth rate equations are discussed. Parameter estimates are given for a feasibility experiment, for a 1 GeV proton accelerator, and for a heavy ion accelerator (50 MeV/nucleon uranium). (auth)

  15. Foundations of ionizing radiation dosimetry

    International Nuclear Information System (INIS)

    Denisenko, O.N.; Pereslegin, I.A.

    1985-01-01

    Foundations of dosimetry in application to radiotherapy are presented. General characteristics of ionizing radiations and main characteristics of ionizing radiation sources, mostly used in radiotherapy, are given. Values and units for measuring ionizing radiation (activity of a radioactive substance, absorbed dose, exposure dose, integral dose and dose equivalent are considered. Different methods and instruments for ionizing radiation dosimetry are discussed. The attention is paid to the foundations of clinical dosimetry (representation of anatomo-topographic information, choice of radiation conditions, realization of radiation methods, corrections for a configuration and inhomogeneity of a patient's body, account of biological factors of radiation effects, instruments of dose field formation, control of irradiation procedure chosen)

  16. Review Ionizing Radiation In The Environment

    International Nuclear Information System (INIS)

    Hassan, K.M.

    2007-01-01

    Our environment is pervaded by ionizing radiation of natural origin including terrestrial radionuclides and extra-terrestrial sources but man's activities can increase radiation levels by acting on natural sources or by producing artificial radionuclides. The energy released by radionuclides can be measured. The amount of energy generated in our bodies from the radioactive decay of within- body radionuclides is called internal dose. External dose results from gamma rays emitted by terrestrial sources such as the ground, building materials and from extraterrestrial sources. The major contributors to human exposure are radon and its daughters in the air that we breathe. Ionizing radiation can penetrate into matter and thus, causing damage by interacting with the atoms and molecules of the medium. If the medium is living tissue, damage to cells can take place. Very large doses of radiation will result in serious tissue, damage that may lead to death of the organism. Lower doses may also be harmful and do not cause the immediate damage of high doses but instead act to increase the likelihood of developing cancer. So, exposure to ionizing radiation can have health consequences, which is why we are concerned about and, to a large extent, is why this review paper was written. Exposure to ionizing radiation should be kept as minimum as practically possible. People are advised to monitor the concentrations of radon in their houses. In addition, the levels of radionuclides in drinking water should also be monitored in accordance with the guidelines used in the USA

  17. Indirect mechanisms in electron-impact ionization of multiply charged ions

    International Nuclear Information System (INIS)

    Phaneuf, R.A.; Gregory, D.C.

    1986-09-01

    The important role of indirect-ionization mechanisms in electron-impact ionization of multiply charged ions has been emphasized by some recent experiments conducted with the ORNL-ECR multicharged ion source. Illustrative examples of investigations of the Mg-isoelectronic and Fe-isonuclear sequences are presented and compared with the results of detailed theoretical calculations. New experimental data is also presented concerning the role of resonance effects in the ionization of Li-like O 5+ and Na-like Fe 15+ ions

  18. Working with MRI: An investigation of occupational exposure to strong static magnetic fields and associated symptoms

    NARCIS (Netherlands)

    Schaap, K.

    2015-01-01

    Magnetic resonance imaging (MRI) makes use of electromagnetic fields in the non-ionizing radiation frequency ranges. One of them is a continuously present strong static magnetic field (SMF), which extends up to several meters around the scanner. Each time an MRI worker performs tasks near the

  19. Free-air ionization intensity in the lower atmosphere due to cosmic-ray

    International Nuclear Information System (INIS)

    Urabe, Itsumasa; Katsurayama, Kousuke

    1979-01-01

    Being able to be determined by subtracting the gamma-ray ionization intensity from that obtained with ionization chamber, cosmic-ray ionization intensity in free air was estimated by using with 15l air-filled ionization chamber and 3''diameter spherical NaI(Tl) scintillation spectrometer. Optimum applied voltage to 15l air-filled ionization chamber was determined in accordance with Scott and Greening's formula to obtain the ionization intensity caused by gamma-rays and cosmic-rays. Pulse-height distribution of cosmic-rays created in 3''diameter spherical NaI(Tl) scintillation spectrometer was investigated for the precise determination of gamma-ray ionization intensity. Field measurements were carried out by using with these two instruments at about 1.5 meter above the ground in the several locations around Research Reactor Institute of Kyoto University. Cosmic-ray ionization intensity in free air was estimated from the results obtained with air-filled ionization chamber and was 3.33 +- 0.15 μR/hr equivalent in natural environment near Research Reactor Institute of Kyoto University. (author)

  20. Ionization of xenon by electrons: Partial cross sections for single, double, and triple ionization

    International Nuclear Information System (INIS)

    Mathur, D.; Badrinathan, C.

    1987-01-01

    High-sensitivity measurements of relative partial cross sections for single, double, and triple ionization of Xe by electron impact have been carried out in the energy region from threshold to 100 eV using a crossed-beam apparatus incorporating a quadrupole mass spectrometer. The weighted sum of the relative partial cross sections at 50 eV are normalized to the total ionization cross section of Rapp and Englander-Golden to yield absolute cross-section functions. Shapes of the partial cross sections for single and double ionization are difficult to account for within a single-particle picture. Comparison of the Xe + data with 4d partial photoionization cross-section measurements indicates the important role played by many-body effects in describing electron-impact ionization of high-Z atoms

  1. Ionization loss in BGO

    International Nuclear Information System (INIS)

    Bakken, J.A.; Denes, P.; Piroue, P.A.; Stickland, D.P.; Sumner, R.L.; Taylor, C.; Barone, L.; Borgia, B.; Diemoz, M.; Dionisi, C.; Falciano, S.; Ferroni, F.; Gratta, G.; Longo, E.; Luminari, L.; Morganti, S.; Valente, E.; Blaising, J.J.; Boutigny, D.; Coignet, G.; Karyotakis, Y.; Sauvage, G.; Schneegans, M.; Vivargent, M.; Extermann, P.; Morand, G.; Ossmann, J.; Ruckstuhl, W.; Schaad, T.P.; Lecoq, P.; Walk, W.; Li, P.J.; Micke, M.; Micke, U.; Schmitz, D.

    1988-01-01

    We report on a precise measurement of the energy loss through ionization by pions in bismuth germanate performed at several values of the incident particles momentum with a prototype of the L3 electromagnetic calorimeter. The experimental results are in good agreement with theoretical predictions showing the relativistic rise modified by density effect. (orig.)

  2. Ionization particle detector

    International Nuclear Information System (INIS)

    Ried, L.

    1982-01-01

    A new device is claimed for detecting particles in a gas. The invention comprises a low cost, easy to assemble, and highly accurate particle detector using a single ionization chamber to contain a reference region and a sensing region. The chamber is designed with the radioactive source near one electrode and the second electrode located at a distance less than the distance of maximum ionization from the radioactive source

  3. Novel target configurations for selective ionization state studies in molybdenum

    International Nuclear Information System (INIS)

    Ilcisin, K.J.; Feldman, U.; Schwob, J.L.; Wouters, A.; Suckewer, S.; Princeton Univ., NJ

    1990-03-01

    Details of experiments aimed at achieving low ionization state selectivity in molybdenum are presented. Targets are excited with a 10 J CO 2 laser and the resultant VUV spectrum (300--700 Angstrom) has been studied. Combinations of focal spot size, target depth, and target geometries are compared. Simple attenuation of energy is shown not to vary ionization stage composition significantly. Experiments conducted with grazing incidence targets result only in a hot plasma. Modular targets with cooling cylinders of various radii demonstrated good selectivity of the ionization states, but with low absolute signals. Finally, results from combinations of focal spot adjustment and radiative cooling illustrate increased control over desired plasma temperature and density for spectroscopic studies of molybdenum. 7 refs., 14 figs

  4. The influence of the electron wave function on the Pt Lsub(I) and Lsub(III) ionization probabilities by 3.6 MeV He impact

    International Nuclear Information System (INIS)

    Ullrich, J.; Dangendorf, V.; Dexheimer, K.; Do, K.; Kelbch, C.; Kelbch, S.; Schadt, W.; Schmidt-Boecking, H.; Stiebing, K.E.; Roesel, F.; Trautmann, D.

    1986-01-01

    For 3.6 MeV He impact the Lsub(I) and Lsub(III) subshell ionization probabilities of Pt have been measured. Due to relativistic effects in the electron wave functions, the Lsub(I) subshell ionization probability Isub(LI)(b) is strong enhanced at small impact parameters exceeding even Isub(LIII)(b) in nice agreement with the SCA theory. (orig.)

  5. Influence of field emission on the propagation of cylindrical fast ionization wave in atmospheric-pressure nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Levko, Dmitry; Raja, Laxminarayan L. [Department of Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin, Austin, Texas 78712 (United States)

    2016-04-21

    The influence of field emission of electrons from surfaces on the fast ionization wave (FIW) propagation in high-voltage nanosecond pulse discharge in the atmospheric-pressure nitrogen is studied by a one-dimensional Particle-in-Cell Monte Carlo Collisions model. A strong influence of field emission on the FIW dynamics and plasma parameters is obtained. Namely, the accounting for the field emission makes possible the bridging of the cathode–anode gap by rather dense plasma (∼10{sup 13 }cm{sup −3}) in less than 1 ns. This is explained by the generation of runaway electrons from the field emitted electrons. These electrons are able to cross the entire gap pre-ionizing it and promoting the ionization wave propagation. We have found that the propagation of runaway electrons through the gap cannot be accompanied by the streamer propagation, because the runaway electrons align the plasma density gradients. In addition, we have obtained that the field enhancement factor allows controlling the speed of ionization wave propagation.

  6. Exact time-dependent exchange-correlation potentials for strong-field electron dynamics

    International Nuclear Information System (INIS)

    Lein, Manfred; Kuemmel, Stephan

    2005-01-01

    By solving the time-dependent Schroedinger equation and inverting the time-dependent Kohn-Sham scheme we obtain the exact time-dependent exchange-correlation potential of density-functional theory for the strong-field dynamics of a correlated system. We demonstrate that essential features of the exact exchange-correlation potential can be related to derivative discontinuities in stationary density-functional theory. Incorporating the discontinuity in a time-dependent density-functional calculation greatly improves the description of the ionization process

  7. Morphology and steroidogenesis of cultured granulosa cells obtained from ovaries of women treated with ionizing radiation

    International Nuclear Information System (INIS)

    Skrzypczak, J.

    1997-01-01

    The object of the study was the morphology and steroidogenesis of cultured granulosa cells obtained from 6 women aged 28-39 years who, because of Ib cervix carcinoma, were treated with ionizing radiation and later underwent surgery. It was observed that the granulosa cells were viable, had strong proliferative ability, and formed a monolayer on day 2 of culture. Contrary to our expectations, these cells produced larger amounts of steroids in culture than the control cells harvested from normal ovaries in late follicular phase. It was also found that the cells treated with ionizing radiation responded to exogenous gonadotropins with higher production of progesterone and estradiol than the controls. It is concluded that the increase in metabolic activity by granulosa cells from ovaries which had been indirectly affected by ionizing radiation is manifested by the stimulating influence of radiation on steroidogenesis. (author)

  8. Potential for the Vishniac instability in ionizing shock waves propagating into cold gases

    Science.gov (United States)

    Robinson, A. P. L.; Pasley, J.

    2018-05-01

    The Vishniac instability was posited as an instability that could affect supernova remnants in their late stage of evolution when subject to strong radiative cooling, which can drive the effective ratio of specific heats below 1.3. The potential importance of this instability to these astrophysical objects has motivated a number of laser-driven laboratory studies. However, the Vishniac instability is essentially a dynamical instability that should operate independently of whatever physical processes happen to reduce the ratio of specific heats. In this paper, we examine the possibility that ionization and molecular dissociation processes can achieve this, and we show that this is possible for a certain range of shock wave Mach numbers for ionizing/dissociating shock waves propagating into cold atomic and molecular gases.

  9. Perception of the mexican public about the warning symbols of ionizing radiations

    International Nuclear Information System (INIS)

    Paredes, L.; Ramos, L.; Avila, G.; Canales, G.; Altamirano, R.

    2007-01-01

    The perception and familiarization of the mexican public on the terms of 'ionizing radiation' and 'radioactive material' and the traditional warning symbol of ionizing radiation, it has been strongly influenced by the television series 'The Simpson' and their character 'Homero Simpson', which has been the means of communication that of agreement to the results of the anonymous survey carried out in the cities of Mexico, Guadalajara, Monterrey, Veracruz and Merida, it has treated these impact topics in the public opinion in a simple way in different chapters of the series, jointly with the medical common practice of carrying out studies of X rays to the patients and the signals placed in the access doors in the imagenology areas. A bigger percentage is reported to 70% of those interviewed that they have listened the terms of 'ionizing radiation' and 'radioactive material. The traditional symbol of warning of ionizing radiation, 12% recognizes it at first sight, the logo doesn't mean him anything, and only a small group that knows the safety color code associates the yellow color of the bottom with the message of warning-danger. For the case of the new symbol, 100% of the interviewees indicates to ignore it at first sight, however the logo stops in 95% of the cases an opinion to have a meaning, being the perception of death 68%, danger 24%, to run 8% and the red color the message of danger. Inside the public with more familiarity with terminology and the derived traditional symbol of warning of their activities in the work, they were identified the firemen. Of the analysis of the surveys it is observed that the perception of fear to the radioactive material is of 42%, continued by that of ionizing radiations with 32% of the mentions. The presented arguments are that it produces cancer 80% and it can exploit 20% for the first case and it produces cancer 100% for the second case. 98% of the public is interested one in receiving bigger information on these topics and

  10. News about ionized food identification

    International Nuclear Information System (INIS)

    Raffi, J.

    1995-01-01

    The ionizing radiations are used to clean food and increase their preservation life. If a lot of countries permits ionized products commercialization, others are opposed to it. To control the commercial exchanges, check the applied treatment aim and give to the consumers a better information, several ionized food identification methods were perfected and several are about to be recognized as european standards. 4 refs. 3 figs, 1 tab

  11. Comparative analysis of inflamed and non-inflamed colon biopsies reveals strong proteomic inflammation profile in patients with ulcerative colitis

    DEFF Research Database (Denmark)

    Poulsen, Nina Aagaard; Andersen, Vibeke; Moller, Jens Christian

    2012-01-01

    colonic biopsies were characterized using 2D-gel electrophoresis, and peptide mass fingerprinting using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was applied for identification of differently expressed protein spots. Results: A total of 597 spots were...... mucosa with acute UC is strong. Totally, 43 individual protein spots were identified, including proteins involved in energy metabolism (triosephosphate isomerase, glycerol-3-phosphate-dehydrogenase, alpha enolase and L-lactate dehydrogenase B-chain) and in oxidative stress (superoxide dismutase...

  12. Clusters of DNA induced by ionizing radiation: formation of short DNA fragments. I. Theoretical modeling

    Science.gov (United States)

    Holley, W. R.; Chatterjee, A.

    1996-01-01

    We have developed a general theoretical model for the interaction of ionizing radiation with chromatin. Chromatin is modeled as a 30-nm-diameter solenoidal fiber comprised of 20 turns of nucleosomes, 6 nucleosomes per turn. Charged-particle tracks are modeled by partitioning the energy deposition between primary track core, resulting from glancing collisions with 100 eV or less per event, and delta rays due to knock-on collisions involving energy transfers >100 eV. A Monte Carlo simulation incorporates damages due to the following molecular mechanisms: (1) ionization of water molecules leading to the formation of OH, H, eaq, etc.; (2) OH attack on sugar molecules leading to strand breaks: (3) OH attack on bases; (4) direct ionization of the sugar molecules leading to strand breaks; (5) direct ionization of the bases. Our calculations predict significant clustering of damage both locally, over regions up to 40 bp and over regions extending to several kilobase pairs. A characteristic feature of the regional damage predicted by our model is the production of short fragments of DNA associated with multiple nearby strand breaks. The shapes of the spectra of DNA fragment lengths depend on the symmetries or approximate symmetries of the chromatin structure. Such fragments have subsequently been detected experimentally and are reported in an accompanying paper (B. Rydberg, Radiat, Res. 145, 200-209, 1996) after exposure to both high- and low-LET radiation. The overall measured yields agree well quantitatively with the theoretical predictions. Our theoretical results predict the existence of a strong peak at about 85 bp, which represents the revolution period about the nucleosome. Other peaks at multiples of about 1,000 bp correspond to the periodicity of the particular solenoid model of chromatin used in these calculations. Theoretical results in combination with experimental data on fragmentation spectra may help determine the consensus or average structure of the

  13. An ionization chamber shower detector for the LHC luminosity monitor

    CERN Document Server

    Beche, J F; Datte, P S; Haguenauer, Maurice; Manfredi, P F; Millaud, J E; Placidi, Massimo; Ratti, L; Re, V; Riot, V J; Schmickler, Hermann; Speziali, V; Turner, W C

    2000-01-01

    The front IR quadrupole absorbers (TAS) and the IR neutral particle absorbers (TAN) in the high luminosity insertions of the Large Hadron Collider (LHC) each absorb approximately 1.8 TeV of forward collision products on average per pp interaction (~235 W at design luminosity 10/sup 34/ cm/sup -2/ s/sup -1/). This secondary particle flux can be exploited to provide a useful storage ring operations tool for optimization of luminosity. A novel segmented, multi-gap, pressurized gas ionization chamber is being developed for sampling the energy deposited near the maxima of the hadronic/electromagnetic showers in these absorbers. The system design choices have been strongly influenced by optimization of signal to noise ratio and by the very high radiation environment. The ionization chambers are instrumented with low noise, fast, pulse shaping electronics to be capable of resolving individual bunch crossings at 40 MHz. Data on each bunch are to be separately accumulated over multiple bunch crossings until the desire...

  14. What is ''ionizing radiation''?

    International Nuclear Information System (INIS)

    Tschurlovits, M.

    1997-01-01

    The scientific background of radiation protection and hence ''ionizing radiation'' is undergoing substantial regress since a century. Radiations as we are concerned with are from the beginning defined based upon their effects rather than upon the physical origin and their properties. This might be one of the reasons why the definition of the term ''ionizing radiation'' in radiation protection is still weak from an up to date point of view in texts as well as in international and national standards. The general meaning is unambiguous, but a numerical value depends on a number of conditions and the purpose. Hence, a clear statement on a numerical value of the energy threshold beyond a radiation has to be considered as ''ionizing'' is still missing. The existing definitions are, therefore, either correct but very general or theoretical and hence not applicable. This paper reviews existing definitions and suggests some issues to be taken into account for possible improvement of the definition of ''ionizing radiation''. (author)

  15. Loss of ions in cavity ionization chambers

    International Nuclear Information System (INIS)

    Takata, N.; Tran, N.T.; Kim, E.; Marsoem, P.; Kurosawa, T.; Koyama, Y.

    2005-01-01

    Ion losses due to initial recombination, volume recombination, and back diffusion were each determined by measurements and calculations for different size cylindrical ionization chambers and spherical ionization chambers. By measuring signal currents from these ionization chambers irradiated with 60 Co gamma rays, two groups of ion losses were obtained. (Group 1) Ion loss due to initial recombination and diffusion, which changes proportionally to the inverse of the voltage applied to the ionization chambers; (and group 2) ion loss due to volume recombination, which changes proportionally to the inverse of the square of the applied voltage. The diffusion loss was obtained separately by computing electric field distributions in the ionization chambers. It was found that diffusion loss is larger than initial recombination loss for the cylindrical ionization chambers and vise versa for the spherical ionization chambers

  16. Escape of ionizing radiation from high redshift dwarf galaxies: role of AGN feedback

    Science.gov (United States)

    Trebitsch, Maxime; Volonteri, Marta; Dubois, Yohan; Madau, Piero

    2018-05-01

    While low mass, star forming galaxies are often considered as the primary driver of reionization, their actual contribution to the cosmic ultraviolet background is still uncertain, mostly because the escape fraction of ionizing photons is only poorly constrained. Theoretical studies have shown that efficient supernova feedback is a necessary condition to create paths through which ionizing radiation can escape into the intergalactic medium. We investigate the possibility that accreting supermassive black holes in early dwarf galaxies may provide additional feedback and enhance the leakage of ionizing radiation. We use a series of high resolution cosmological radiation hydrodynamics simulations where we isolate the different sources of feedback. We find that supernova feedback prevents the growth of the black hole, thus quenching its associated feedback. Even in cases where the black hole can grow, the structure of the interstellar medium is strongly dominated by supernova feedback. We conclude that, in the dwarf galaxy regime, supermassive black holes do not appear to play a significant role in enhancing the escape fraction and in contributing to the early UV background.

  17. Many-electron model for multiple ionization in atomic collisions

    International Nuclear Information System (INIS)

    Archubi, C D; Montanari, C C; Miraglia, J E

    2007-01-01

    We have developed a many-electron model for multiple ionization of heavy atoms bombarded by bare ions. It is based on the transport equation for an ion in an inhomogeneous electronic density. Ionization probabilities are obtained by employing the shell-to-shell local plasma approximation with the Levine and Louie dielectric function to take into account the binding energy of each shell. Post-collisional contributions due to Auger-like processes are taken into account by employing recent photoemission data. Results for single-to-quadruple ionization of Ne, Ar, Kr and Xe by protons are presented showing a very good agreement with experimental data

  18. Many-electron model for multiple ionization in atomic collisions

    Energy Technology Data Exchange (ETDEWEB)

    Archubi, C D [Instituto de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28 (C1428EGA) Buenos Aires (Argentina); Montanari, C C [Instituto de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28 (C1428EGA) Buenos Aires (Argentina); Miraglia, J E [Instituto de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28 (C1428EGA) Buenos Aires (Argentina)

    2007-03-14

    We have developed a many-electron model for multiple ionization of heavy atoms bombarded by bare ions. It is based on the transport equation for an ion in an inhomogeneous electronic density. Ionization probabilities are obtained by employing the shell-to-shell local plasma approximation with the Levine and Louie dielectric function to take into account the binding energy of each shell. Post-collisional contributions due to Auger-like processes are taken into account by employing recent photoemission data. Results for single-to-quadruple ionization of Ne, Ar, Kr and Xe by protons are presented showing a very good agreement with experimental data.

  19. Ionization and scintillation of nuclear recoils in gaseous xenon

    Energy Technology Data Exchange (ETDEWEB)

    Renner, J., E-mail: jrenner@lbl.gov [Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Berkeley, CA 94720 (United States); Department of Physics, University of California, Berkeley, CA 94720 (United States); Gehman, V.M.; Goldschmidt, A.; Matis, H.S.; Miller, T.; Nakajima, Y.; Nygren, D.; Oliveira, C.A.B.; Shuman, D. [Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Berkeley, CA 94720 (United States); Álvarez, V. [Instituto de Física Corpuscular (IFIC), CSIC & Universitat de València, Calle Catedrático José Beltrán, 2, 46980 Paterna, Valencia (Spain); Borges, F.I.G. [Departamento de Fisica, Universidade de Coimbra, Rua Larga, 3004-516 Coimbra (Portugal); Cárcel, S. [Instituto de Física Corpuscular (IFIC), CSIC & Universitat de València, Calle Catedrático José Beltrán, 2, 46980 Paterna, Valencia (Spain); Castel, J.; Cebrián, S. [Laboratorio de Física Nuclear y Astropartículas, Universidad de Zaragoza, Calle Pedro Cerbuna 12, 50009 Zaragoza (Spain); Cervera, A. [Instituto de Física Corpuscular (IFIC), CSIC & Universitat de València, Calle Catedrático José Beltrán, 2, 46980 Paterna, Valencia (Spain); Conde, C.A.N. [Departamento de Fisica, Universidade de Coimbra, Rua Larga, 3004-516 Coimbra (Portugal); and others

    2015-09-01

    Ionization and scintillation produced by nuclear recoils in gaseous xenon at approximately 14 bar have been simultaneously observed in an electroluminescent time projection chamber. Neutrons from radioisotope α-Be neutron sources were used to induce xenon nuclear recoils, and the observed recoil spectra were compared to a detailed Monte Carlo employing estimated ionization and scintillation yields for nuclear recoils. The ability to discriminate between electronic and nuclear recoils using the ratio of ionization to primary scintillation is demonstrated. These results encourage further investigation on the use of xenon in the gas phase as a detector medium in dark matter direct detection experiments.

  20. Double ionization of atomic helium under heavy ion impact

    International Nuclear Information System (INIS)

    Presnyakov, L.P.; Uskov, D.B.

    1995-01-01

    Cross sections for double ionization of helium by multiply-charged ion impact and the corresponding ratios of double-to-single ionization are presented as a sum of the contributions given by the one-step (shake-off) and two-step (TS) processes. An analytic form is found for the continuum wavefunction which is valid in both limiting cases of low and high velocities of the relative motion. Using this wavefunction, the TS cross sections are calculated within the independent-event model. The results for the ratios of double-to-single ionization show satisfactory agreement with the experimental data available. (author)