Abstract: In diffuse interstellar clouds the chemistry that leads to the formation of the oxygen-bearing ions OH+, H2O+, and H3O+ begins with the ionization of atomic hydrogen by cosmic rays, and continues through subsequent hydrogen abstraction reactions involving H2 Given these reaction pathways, the observed abundances of these molecules are useful in constraining both the total cosmic-ray ionization rate of atomic hydrogen (ζH) and molecular hydrogen fraction (f_H_2) We present observations targeting transitions of OH+, H2O+, and H3O+ made with the Herschel Space Observatory along 20 Galactic sight lines toward bright submillimeter continuum sources Both OH+ and H2O+ are detected in absorption in multiple velocity components along every sight line, but H3O+ is only detected along 7 sight lines From the molecular abundances we compute f_H_2 in multiple distinct components along each line of sight, and find a Gaussian distribution with mean and standard deviation 0042 ± 0018 This confirms previous findings that OH+ and H2O+ primarily reside in gas with low H2 fractions We also infer ζH throughout our sample, and find a lognormal distribution with mean log (ζH) = –1575 (ζH = 178 × 10–16 s–1) and standard deviation 029 for gas within the Galactic disk, but outside of the Galactic center This is in good agreement with the mean and distribution of cosmic-ray ionization rates previously inferred from H_3^+ observations Ionization rates in the Galactic center tend to be 10-100 times larger than found in the Galactic disk, also in accord with prior studies

Abstract: We present an observational and theoretical study of the primary ionizing agents (cosmic rays (CRs) and X-rays) in the TW Hya protoplanetary disk. We use a set of resolved and unresolved observations of molecular ions and other molecular species, encompassing 11 lines total, in concert with a grid of disk chemistry models. The molecular ion constraints comprise new data from the Submillimeter Array on HCO+, acquired at unprecedented spatial resolution, and data from the literature, including ALMA observations of N2H+. We vary the model incident CR flux and stellar X-ray spectra and find that TW Hya's HCO+ and N2H+ emission are best-fit by a moderately hard X-ray spectra, as would be expected during the flaring state of the star, and a low CR ionization rate, ?CR 10?19 s?1. This low CR rate is the first indication of the presence of CR exclusion by winds and/or magnetic fields in an actively accreting T Tauri disk system. With this new constraint, our best-fit ionization structure predicts a low turbulence dead-zone extending from the inner edge of the disk out to 50-65 AU. This region coincides with an observed concentration of millimeter grains, and we propose that the inner region of TW Hya is a dust (and possibly planet) growth factory as predicted by previous theoretical work.

Abstract: We review the status of the theory of ionization of atoms and ions by intense laser radiation (Keldysh's theory). We discuss the applicability of the theory, its relation to the Landau–Dykhne method, and its application to the ionization of atoms by ultrashort nonmonochromatic laser pulses of an arbitrary shape. The semiclassical imaginary time method is applied to describe electron sub-barrier motion using classical equations of motion with an imaginary time i for an electron in the field of an electromagnetic wave. We also discuss tunneling interference of transition amplitudes, a phenomenon occurring due to the existence of several saddle points in the complex time plane and leading to fast oscillations in the momentum distribution of photoelectrons. Nonperturbatively taking the Coulomb interaction between an outgoing electron and the atomic residual into account causes significant changes in the photoelectron momentum distribution and in the level ionization rates, the latter usually increasing by orders of magnitude for both tunneling and multiquantum ionization. The effect of a static magnetic field on the ionization rate and the magnetic cumulation process is examined. The theory of relativistic tunneling is discussed, relativistic and spin corrections to the ionization rate are calculated, and the applicability limits of the nonrelativistic Keldysh theory are determined. Finally, the application of the Fock method to the covariant description of nonlinear ionization in the relativistic regime is discussed.

Abstract: Atmospheric pressure plasma propagation inside long dielectric tubes is analyzed for the first time through nonintrusive and nonperturbative time resolved bi-directional electric field (EF) measurements. This study unveils that plasma propagation occurs in a region where longitudinal EF exists ahead the ionization front position usually revealed from plasma emission with ICCD measurement. The ionization front propagation induces the sudden rise of a radial EF component. Both of these EF components have an amplitude of several kV/cm for helium or neon plasmas and are preserved almost constant along a few tens of cm inside a capillary. All these experimental measurements are in excellent agreement with previous model calculations. The key roles of the voltage pulse polarity and of the target nature on the helium flow patterns when plasma jet is emerging in ambient air are documented from Schlieren visualization. The second part of this work is then dedicated to the development of multi jet systems, using two different setups, based on a single plasma source. Plasma splitting in dielectric tubes drilled with sub millimetric orifices, but also plasma transfer across metallic tubes equipped with such orifices are reported and analyzed from ICCD imaging and time resolved EF measurements. This allows for the design and the feasibility validation of plasma jet arrays but also emphasizes the necessity to account for voltage pulse polarity, target potential status, consecutive helium flow modulation, and electrostatic influence between the produced secondary jets.

Abstract: This paper demonstrates that the CO2 conversion in a dielectric barrier discharge rises drastically upon addition of Ar or He, and the effect is more pronounced for Ar than for He. The effective CO2 conversion, on the other hand, drops upon addition of Ar or He, which is logical due to the lower CO2 content in the gas mixture, and the same is true for the energy efficiency, because a considerable fraction of the energy is then consumed into ionization/excitation of Ar or He atoms. The higher absolute CO2 conversion upon addition of Ar or He can be explained by studying in detail the Lissajous plots and the current profiles. The breakdown voltage is lower in the CO2/Ar and CO2/He mixtures, and the discharge gap is more filled with plasma, which enhances the possibility for CO2 conversion. The rates of electron impact excitation–dissociation of CO2, estimated from the electron densities and mean electron energies, are indeed higher in the CO2/Ar and (to a lower extent) in the CO2/He mixtures, compared to the pure CO2 plasma. Moreover, charge transfer between Ar+ or Ar2+ ions and CO2, followed by electron-ion dissociative recombination of the CO2+ ions, might also contribute to, or even be dominant for the CO2 dissociation. All these effects can explain the higher CO2 conversion, especially upon addition of Ar, but also upon addition of He.

Abstract: We have measured the scintillation and ionization yield of recoiling nuclei in liquid argon as a function of applied electric field by exposing a dual-phase liquid argon time projection chamber (LAr-TPC) to a low energy pulsed narrow band neutron beam produced at the Notre Dame Institute for Structure and Nuclear Astrophysics. Liquid scintillation counters were arranged to detect and identify neutrons scattered in the TPC and to select the energy of the recoiling nuclei. We report measurements of the scintillation yields for nuclear recoils with energies from 10.3 to 57.3 keV and for median applied electric fields from 0 to $970\text{ }\text{ }\mathrm{V}/\mathrm{cm}$. For the ionization yields, we report measurements from 16.9 to 57.3 keV and for electric fields from 96.4 to $486\text{ }\text{ }\mathrm{V}/\mathrm{cm}$. We also report the observation of an anticorrelation between scintillation and ionization from nuclear recoils, which is similar to the anticorrelation between scintillation and ionization from electron recoils. Assuming that the energy loss partitions into excitons and ion pairs from $^{83m}\mathrm{Kr}$ internal conversion electrons is comparable to that from $^{207}\mathrm{Bi}$ conversion electrons, we obtained the numbers of excitons (${N}_{\text{ex}}$) and ion pairs (${N}_{\mathrm{i}}$) and their ratio (${N}_{\text{ex}}/{N}_{\mathrm{i}}$) produced by nuclear recoils from 16.9 to 57.3 keV. Motivated by arguments suggesting direction sensitivity in LAr-TPC signals due to columnar recombination, a comparison of the light and charge yield of recoils parallel and perpendicular to the applied electric field is presented for the first time.

Abstract: Ionization-induced injection mechanism was introduced in 2010 to reduce the laser intensity threshold for controllable electron trapping in laser wakefield accelerators (LWFA). However, usually it generates electron beams with continuous energy spectra. Subsequently, a dual-stage target separating the injection and acceleration processes was regarded as essential to achieve narrow energy-spread electron beams by ionization injection. Recently, we numerically proposed a self-truncation scenario of the ionization injection process based upon overshooting of the laser-focusing in plasma which can reduce the electron injection length down to a few hundred micrometers, leading to accelerated beams with extremely low energy-spread in a single-stage. Here, using 100 TW-class laser pulses we report experimental observations of this injection scenario in centimeter-long plasma leading to the generation of narrow energy-spread GeV electron beams, demonstrating its robustness and scalability. Compared with the self-injection and dual-stage schemes, the self-truncated ionization injection generates higher-quality electron beams at lower intensities and densities, and is therefore promising for practical applications.

Abstract: We study the ionization and kinematics of the ionized gas in the nuclear region of the barred Seyfert 2 galaxy NGC~5643 using MUSE integral field observations in the framework of the MAGNUM (Measuring Active Galactic Nuclei Under MUSE Microscope) survey. The data were used to identify regions with different ionization conditions and to map the gas density and the dust extinction. We find evidence for a double sided ionization cone, possibly collimated by a dusty structure surrounding the nucleus. At the center of the ionization cone, outflowing ionized gas is revealed as a blueshifted, asymmetric wing of the [OIII] emission line, up to projected velocity v(10)~-450 km/s. The outflow is also seen as a diffuse, low luminosity radio and X-ray jet, with similar extension. The outflowing material points in the direction of two clumps characterized by prominent line emission with spectra typical of HII regions, located at the edge of the dust lane of the bar. We propose that the star formation in the clumps is due to `positive feedback' induced by gas compression by the nuclear outflow, providing the first candidate for outflow induced star formation in a Seyfert-like radio quiet AGN. This suggests that positive feedback may be a relevant mechanism in shaping the black hole-host galaxy coevolution.

Abstract: The ionization dynamics in geometrically symmetric parallel plate capacitively coupled plasmas driven by radio frequency tailored voltage waveforms is investigated using phase resolved optical emission spectroscopy (PROES) and particle-in-cell (PIC) simulations. Temporally asymmetric waveforms induce spatial asymmetries and offer control of the spatiotemporal dynamics of electron heating and associated ionization structures. Sawtooth waveforms with different rise and fall rates are employed using truncated Fourier series approximations of an ideal sawtooth. Experimental PROES results obtained in argon plasmas are compared with PIC simulations, showing excellent agreement. With waveforms comprising a fast voltage drop followed by a slower rise, the faster sheath expansion in front of the powered electrode causes strongly enhanced ionization in this region. The complementary waveform causes an analogous effect in front of the grounded electrode.

Abstract: We present a study of X-ray ionization of MHD accretion-disk winds in an effort to constrain the physics underlying the highly ionized ultra-fast outflows (UFOs) inferred by X-ray absorbers often detected in various sub classes of Seyfert active galactic nuclei (AGNs). Our primary focus is to show that magnetically driven outflows are indeed physically plausible candidates for the observed outflows accounting for the AGN absorption properties of the present X-ray spectroscopic observations. Employing a stratified MHD wind launched across the entire AGN accretion disk, we calculate its X-ray ionization and the ensuing X-ray absorption-line spectra. Assuming an appropriate ionizing AGN spectrum, we apply our MHD winds to model the absorption features in an XMM-Newton/EPIC spectrum of the narrow-line Seyfert, PG 1211+143. We find, through identifying the detected features with Fe Kα transitions, that the absorber has a characteristic ionization parameter of log (ξc[erg cm s−1]) 5–6 and a column density on the order of NH 1023 cm−2 outflowing at a characteristic velocity of vc/c 0.1–0.2 (where c is the speed of light). The best-fit model favors its radial location at rc 200 Ro (Ro is the black hole's innermost stable circular orbit), with an inner wind truncation radius at Rt 30 Ro. The overall K-shell feature in the data is suggested to be dominated by Fe xxv with very little contribution from Fe xxvi and weakly ionized iron, which is in good agreement with a series of earlier analyses of the UFOs in various AGNs, including PG 1211+143.

Abstract: Recent studies have demonstrated that femtosecond laser pulses have high potential in application to environmental science. Because of the properties of ultrafast, broadband and high power, the propagation of femtosecond laser pulses in air can lead to the generation of a strong field of 1013–1014 W/cm2 with a large distance range from meter to kilometers. The strong laser field induces ionization and fragmentation of molecules in the laser propagation path, resulting in characteristic fingerprint emissions. This paper mainly focuses on recent research advances in environmental sensing by using femtosecond laser pulses through strong-field-induced ionization and fragmentation of molecules. The fingerprint emissions of molecules in strong laser fields are discussed based on the understanding of strong-field–molecule interactions in atmospheric as well as in vacuum environments. This is followed by a comprehensive review of several recently developed optical methods for coherent control of fingerprint emissions of molecules. Lastly, both current challenges and a future perspective of this dynamic field are discussed.

Abstract: An experimental and numerical study of the laser-induced damage of the surface of optical material in the femtosecond regime is presented The objective of this work is to investigate the different processes involved as a function of the ratio of photon to bandgap energies and compare the results to models based on nonlinear ionization processes Experimentally, the laser-induced damage threshold of optical materials has been studied in a range of wavelengths from 1030 nm (12 eV) to 310 nm (4 eV) with pulse durations of 100 fs with the use of an optical parametric amplifier system Semi-conductors and dielectrics materials, in bulk or thin film forms, in a range of bandgap from 1 to 10 eV have been tested in order to investigate the scaling of the femtosecond laser damage threshold with the bandgap and photon energy A model based on the Keldysh photo-ionization theory and the description of impact ionization by a multiple-rate-equation system is used to explain the dependence of laser-breakdown with the

Abstract: The band gap and defect states of MgO thin films were investigated by using reflection electron energy loss spectroscopy (REELS) and high-energy resolution REELS (HR-REELS) HR-REELS with a primary electron energy of 03 keV revealed that the surface F center (FS) energy was located at approximately 42 eV above the valence band maximum (VBM) and the surface band gap width (EgS) was approximately 63 eV The bulk F center (FB) energy was located approximately 49 eV above the VBM and the bulk band gap width was about 78 eV, when measured by REELS with 3 keV primary electrons From a first-principles calculation, we confirmed that the 42 eV and 49 eV peaks were FS and FB, induced by oxygen vacancies We also experimentally demonstrated that the HR-REELS peak height increases with increasing number of oxygen vacancies Finally, we calculated the secondary electron emission yields (γ) for various noble gases He and Ne were not influenced by the defect states owing to their higher ionization energies, but

Abstract: Ultrathin graphitic carbon nitride (g-C3N4) nanosheets served as a novel matrix for the detection of small molecules by negative ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was described for the first time. In comparison with conventional organic matrices and graphene matrix, the use of g-C3N4 nanosheet matrix showed free matrix background interference and increased signal intensity in the analysis of amino acids, nucleobases, peptides, bisphenols (BPs), and nitropolycyclic aromatic hydrocarbons (nitro-PAHs). A systematic comparison of g-C3N4 nanosheets with positive and negative ion modes revealed that mass spectra produced by g-C3N4 nanosheets in negative ion mode were featured by singly deprotonated ion without matrix interference, which was rather different from the complicated alkali metal complexes in positive ion mode. Good salt tolerance and reproducibility allowed the determination of 1-nitropyrene (1-NP) in sewage, and its corresponding detecti...

Abstract: The first nitryl chloride (ClNO2) measurements in the UK were made during the summer 2012 ClearfLo campaign with a chemical ionization mass spectrometer, utilizing an I− ionization scheme. Concentrations of ClNO2 exceeded detectable limits (11 ppt) every night with a maximum concentration of 724 ppt. A diurnal profile of ClNO2 peaking between 4 and 5 A.M., decreasing directly after sunrise, was observed. Concentrations of ClNO2 above the detection limit are generally observed between 8 P.M. and 11 A.M. Different ratios of the production of ClNO2:N2O5 were observed throughout with both positive and negative correlations between the two species being reported. The photolysis of ClNO2 and a box model utilizing the Master Chemical Mechanism modified to include chlorine chemistry was used to calculate Cl atom concentrations. Simultaneous measurements of hydroxyl radicals (OH) using low pressure laser-induced fluorescence and ozone enabled the relative importance of the oxidation of three groups of measured VOCs (alkanes, alkenes, and alkynes) by OH radicals, Cl atoms, and O3 to be compared. For the day with the maximum calculated Cl atom concentration, Cl atoms in the early morning were the dominant oxidant for alkanes and, over the entire day, contributed 15%, 3%, and 26% toward the oxidation of alkanes, alkenes, and alkynes, respectively.

Abstract: Time-delays in the photoionization of molecules are investigated. As compared to atomic ionization, the time-delays expected from molecular ionization present a much richer phenomenon, with a strong spatial dependence due to the anisotropic nature of the molecular scattering potential. We investigate this from a scattering theory perspective, and make use of molecular photoionization calculations to examine this effect in representative homonuclear and hetronuclear diatomic molecules, nitrogen and carbon monoxide. We present energy and angle-resolved maps of the Wigner delay time for single-photon valence ionization, and discuss the possibilities for experimental measurements.

Abstract: Cross section data are compiled from the literature for electron collisions with methane (CH4) molecules Cross sections are collected and reviewed for total scattering, elastic scattering, momentum transfer, excitations of rotational and vibrational states, dissociation, ionization, and dissociative attachment The data derived from swarm experiments are also considered For each of these processes, the recommended values of the cross sections are presented The literature has been surveyed through early 2014

Abstract: Aims. We study the deuteration and ionization structure of the DM Tau disk via interferometric observations and modelling of the key molecular ions, HCO+ and DCO+ .Methods. The Plateau de Bure Array is used to observe DM Tau in lines of HCO+ (1−0), (3−2) and DCO+ (3−2) with a ~ 1.5′′ angular and ~0.2 km s-1 spectral resolution. Using a power-law fitting approach the observed column densities profiles are derived and thus the isotopic ratio R D = DCO+ /HCO+ . Chemical modelling allowed an exploration of the sensitivity of HCO+ and DCO+ abundances to physical parameters out with temperature. A steady state approximation was employed to observationally constrain the ionization fraction x (e− ).Results. Fitting of radiative transfer models suggests that there is a chemical hole in HCO+ and DCO+ , extending up to 50 AU from the star. More work is required to discern the cause of this. The observed column densities of HCO+ and DCO+ at 100 AU were (9.8+0.3 -0.7 ) × 1012 and (1.2 ± 0.7) × 1012 cm-2 respectively. Where both HCO+ and DCO+ were present, R D was found to increase radially from 0.1 at 50 AU to 0.2 at 450 AU. This behaviour was well reproduced by the chemical model. The X-ray luminosity of the central star, the interstellar UV and CO depletion were found to be the most important physical parameters controlling the abundances of HCO+ and DCO+ . Differences in the vertical extent of HCO+ and DCO+ molecular layers resulted in different responses to changing physical parameters, manifesting as radial gradients in R D . The ionization fraction was found to be x (e− ) ~ 10-7 in the molecular layer, comparable to the disk averaged value. Modelling shows that while HCO+ is the most dominant charged molecular ion in our disk model, atomic ions, such as C+ , S+ , H+ , Na+ and Mg+ , dominate the charge in both the molecular layer and disk atmosphere.Conclusions. A high value of R D is indicative of continued deuterium fractionation in a protoplanetary disk after pre/protostellar phases. Radial properties of R D can be employed to discern the importance of ionization from X-rays and UV, thus necessitating the need for more, high resolution observations of DCO+ and other deuterated species in disks. A steady-state approach commonly adopted for constraining ionization degree in prestellar cores is not applicable for disks where accurate determination of the ionization fraction in the molecular layer requires knowledge of the atomic ions present as molecular ions are relatively sparse.

Abstract: In most PIC/MCC simulations of radio frequency capacitively coupled plasmas (CCPs) several simplifications are commonly made: (i) fast neutrals are not traced, (ii) heavy particle induced excitation and ionization are neglected, (iii) secondary electron emission from boundary surfaces due to neutral particle impact is not taken into account, and (iv) the secondary electron emission coefficient is assumed to be constant, i.e. independent of the incident particle energy and the surface conditions. Here, we examine the validity of these simplifications under conditions typical for plasma processing applications. We study the effects of including fast neutrals and using realistic energy-dependent secondary electron emission coefficients for ions and fast neutrals in simulations of CCPs operated in argon at 13.56 MHz and at neutral gas pressures between 5 Pa and 100 Pa. We find an increase of the plasma density and the ion flux to the electrodes under most conditions when heavy particles are included realistically in the simulation. The sheath widths are found to be smaller and the simulations are found to diverge at high pressures for high voltage amplitudes in qualitative agreement with experimental findings. By switching individual processes on and off in the simulations we identify their individual effects on the ionization dynamics and plasma parameters. While the gas-phase effects of heavy particle processes are found to be moderate at most conditions, the self-consistent calculation of the effective secondary electron yield proves to be important in simulations of CCPs in order to yield realistic results.

Abstract: The presence of a weak second-harmonic field in an intense-laser ionization experiment affects the momentum-resolved electron yield, depending on the relative phase between the ω and the 2ω component. The proposed two-color "phase-of-the-phase spectroscopy" quantifies for each final electron momentum a relative-phase contrast (RPC) and a phase of the phase (PP) describing how much and with which phase lag, respectively, the yield changes as a function of the relative phase. Experimental results for RPC and PP spectra for rare gas atoms and CO_{2} are presented. The spectra demonstrate a rather universal structure that is analyzed with the help of a simple model based on electron trajectories, wave-packet spreading, and (multiple) rescattering. Details in the PP and RPC spectra are target sensitive and, thus, may be used to extract structural (or even dynamical) information with high accuracy.

Abstract: Winds outflowing from active galactic nuclei (AGNs) may carry significant amounts of mass and energy out to their host galaxies. In this paper we report the detection of a sub-relativistic outflow observed in the narrow line Seyfert 1 galaxy IRAS 17020+4544 as a series of absorption lines corresponding to at least five absorption components with an unprecedented wide range of associated column densities and ionization levels and velocities in the range of 23,000–33,000 km s−1, detected at X-ray high spectral resolution (E/ΔE ~ 1000) with the ESA's observatory XMM-Newton. The charge states of the material constituting the wind clearly indicate a range of low to moderate ionization states in the outflowing gas and column densities that are significantly lower than observed in highly ionized ultra-fast outflows. We estimate that at least one of the outflow components may carry sufficient energy to substantially suppress star formation and heat the gas in the host galaxy. IRAS 17020+4544 therefore provides an interesting example of feedback by a moderately luminous AGN that is hosted in a spiral galaxy, a case barely envisaged in most evolution models, which often predict that feedback processes take place in massive elliptical galaxies hosting luminous quasars in a post-merger phase.

Abstract: We present X-ray timing and spectral analyses of simultaneous 150 ks Nuclear Spectroscopic Telescope Array (NuSTAR) and Suzaku X-ray observations of the Seyfert 1.5 galaxy NGC 4151. We disentangle the continuum emission, absorption, and reflection properties of the active galactic nucleus (AGN) by applying inner accretion disk reflection and absorption-dominated models. With a time-averaged spectral analysis, we find strong evidence for relativistic reflection from the inner accretion disk. We find that relativistic emission arises from a highly ionized inner accretion disk with a steep emissivity profile, which suggests an intense, compact illuminating source. We find a preliminary, near-maximal black hole spin_(ɑ > 0.9) accounting for statistical and systematic modeling errors. We find a relatively moderate reflection fraction with respect to predictions for the lamp post geometry, in which the illuminating corona is modeled as a point source. Through a time-resolved spectral analysis, we find that modest coronal and inner disk reflection (IDR) flux variation drives the spectral variability during the observations. We discuss various physical scenarios for the IDR model and we find that a compact corona is consistent with the observed features.

Abstract: The electrons in a plasma can further ionize the ions when the two collide. Vinko et al. now study this ultrafast process in an unconventional plasma with a density similar to that of a solid, and show that the rate is several times higher than that predicted by standard theoretical models.

Abstract: A temperature dependence of impact ionization coefficients in 4H-SiC was studied in a wide range of electric field toward the accurate designing of ultrahigh-voltage devices. The photomultiplication measurement was conducted for various photodiodes with different multiplication layer structures to obtain multiplication factors and ionization coefficients in a wide range of electric field strength. Especially, using multiplication layer structure with low doping concentration, the hole impact ionization coefficient was extracted at low electric field of 1 MV/cm. In high-temperature measurement, the hole ionization coefficient decreased with the increase of temperature, as observed in other semiconductor materials. For the electron ionization coefficient, however, its temperature dependence was very small and values obtained at room temperature could be used, at least up to 150 °C.