High Ionization Potential Research Articles

Herschel-PACS spectroscopic diagnostics of local ULIRGs: Conditions and kinematics in Markarian 231

In this first paper on the results of our Herschel PACS survey of local Ultraluminous Infrared Galaxies (ULIRGs), as part of our SHINING survey of local galaxies, we present far-infrared spectroscopy of Mrk 231, the most luminous of the local ULIRGs, and a type 1 broad absorption line AGN. For the first time in a ULIRG, all observed far-infrared fine-structure lines in the PACS range were detected and all were found to be deficient relative to the far infrared luminosity by 1 - 2 orders of magnitude compared with lower luminosity galaxies. The deficits are similar to those for the mid-infrared lines, with the most deficient lines showing high ionization potentials. Aged starbursts may account for part of the deficits, but partial covering of the highest excitation AGN powered regions may explain the remaining line deficits. A massive molecular outflow, discovered in OH and 18OH, showing outflow velocities out to at least 1400 km/sec, is a unique signature of the clearing out of the molecular disk that formed by dissipative collapse during the merger. The outflow is characterized by extremely high ratios of 18O / 16O suggestive of interstellar medium processing by advanced starbursts.

DENSITY FUNCTIONAL STUDY OF STRUCTURE AND STABILITY OF Al7OH CLUSTERS

We studied the structure and electronic properties of Al 7 OH clusters using density functional theory with generalized gradient approximation. OH prefers to the ontop site of Al atoms, and the hollow form is not stable. The Al 7 moieties can keep their structures in ontop form Al 7 OH cluster, while it dramatically changes for bridge form ones. The binding strength between Al 7 and OH are much larger than that of Al 7 I and Al 7 H . The bonding characteristic of Al 7– OH is mainly ionic according to the population analysis. Large binding energy, HOMO–LUMO gap, and high ionization potential imply that Al 7 OH cluster is physically high and chemically stable.

High work function transparent middle electrode for organic tandem solar cells

The use of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) in combination with ZnO as middle electrode in solution-processed organic tandem solar cells requires a pH modification of the PEDOT:PSS dispersion. We demonstrate that this neutralization leads to a reduced work function of PEDOT:PSS, which does not affect the performance of polythiophene:fullerene solar cells, but results in a lower open-circuit voltage of devices based on a polyfluorene derivative with a higher ionization potential. The introduction of a thin layer of a perfluorinated ionomer recovers the anode work function and gives an open-circuit voltage of 1.92 V for a double junction polyfluorene-based solar cell.

Nonlinear time-dependent density-functional-theory study of ionization and harmonic generation in CO2by ultrashort intense laser pulses: Orientational effects

Time-dependent density-functional-theory (TDDFT) methods are used to calculate the orientational dependence of ionization and molecular high-order harmonic generation (MHOHG) in the CO${}_{2}$ molecule as a function of laser intensity ${I}_{0}\ensuremath{\geqslant}{10}^{14}$ W$/$cm${}^{2}$ for few-cycle 800 nm laser pulses. A time-series analysis is used to confirm the recollision model in MHOHG for different density potentials. It is found that at intensities ${I}_{0}g3.5\ifmmode\times\else\texttimes\fi{}{10}^{14}$ W$/$cm${}^{2}$, lower highest occupied molecular orbitals (HOMO's) contribute significantly to ionization and to the MHOHG process. This is due to the symmetry of these orbitals. Even though such lower orbitals have higher ionization potentials (IP), ionization and MHOHG processes occur when orbital densities are maximum with laser polarization direction.

Structural, electronic, and optical properties of medium-sized Li n clusters ( n=20, 30, 40, 50) by density functional theory

The lowest-energy structures of medium-sized Li n ( n=20, 30, 40, 50) clusters are determined from simulated annealing technique followed by geometry optimization within the framework of density functional theory. The shapes of magic-number Li 20 and Li 40 clusters are nearly spherical while those of the other clusters are ellipsoid. The growth of Li n clusters is based on core of multi-layered pentagonal bipyramids with other atoms capped on the surface. The binding energies of the Li n clusters were computed and compared with experiments. At magic-number sizes ( n=20, 40), Li n clusters possess relatively larger HOMO–LUMO gaps and higher ionization potentials, corresponding to the closure of electron shell. The molecular orbitals of the lithium clusters can be grouped into electron shells and their spatial distributions resemble the atomic orbitals. The average polarizability of the Li clusters reduces rapidly with cluster size and can be approximately described by a classical metallic sphere model. The optical absorption spectra of Li n clusters from time-dependent density functional theory calculations show giant resonance phenomenon, and resonance peak blueshifts with increasing cluster size.

Hot and cool: two emission-line stars with constrasting behaviours in the same XMM-Newtonfield

High-energy emissions are good indicators of peculiar behaviours in stars. We have therefore obtained an XMM-Newton observation of HD155806 and 1RXSJ171502.4-333344, and derived their spectral properties for the first time. The X-ray spectrum of HD155806 appears soft, even slightly softer than usual for O-type stars (as shown by a comparison with the O9 star HD155889 in the same XMM field). It is well-fitted with a two-component thermal model with low temperatures (0.2 and 0.6 keV), and it shows no overluminosity (log[LX/Lbol]=-6.75). The high-resolution spectrum, though noisy, reveals a few broad, symmetric X-ray lines (FWHM ~ 2500 km/s). The X-ray emission is compatible with the wind-shock model and therefore appears unaffected by the putative dense equatorial regions at the origin of the Oe classification. 1RXSJ171502.4-333344 is a nearby flaring source of moderate X-ray luminosity (log[LX/Lbol]=-3), with a soft thermal spectrum composed of narrow lines and presenting a larger abundance of elements (e.g. Ne) with a high first ionization potential (FIP) compared to lower-FIP elements. All the evidence indicates a coronal origin for the X-ray emission, in agreement with the dMe classification of this source.

Signal enhancement of the laser-induced plasma in the soil mixed with carbon

An experimental investigation of the carbon concentration effects on the emission intensity has been carried out using laser-induced plasma spectroscopy. The results show that the intensity of Ca II 393.367 nm and 396.847 nm characteristic lines emitted in the sample with the carbon concentration of 25% is about five times larger than that in the pure soil sample. It can be attributed to the high heat transfer coefficient and low ionization potentials of carbon in the system. Using the best experimental condition, quantitative analysis of the trace element of lead is conducted and the detection limit of lead concentration is estimated to be below 0.02%.

Extension of high harmonic spectroscopy in molecules by a 1300 nm laser field

The emerging techniques of molecular spectroscopy by high order harmonic generation have hitherto been conducted only with Ti:Sapphire lasers which are restricted to molecules with high ionization potentials. In order to gain information on the molecular structure, a broad enough range of harmonics is required. This implies using high laser intensities which would saturate the ionization of most molecular systems of interest, e.g. organic molecules. Using a laser at 1300 nm, we are able to extend the technique to molecules with relatively low ionization potentials (approximately 11 eV), observing wide harmonic spectra reaching up to 60 eV. This energy range improves spatial resolution of the high harmonic spectroscopy to the point where interference minima in harmonic spectra of N(2)O and C(2)H(2) can be observed.

ELEMENTAL ABUNDANCES IN THE FAST SOLAR WIND EMANATING FROM CHROMOSPHERIC FUNNELS

We carry out a model study to determine whether a funnel-type flow geometry in the solar wind source region leads to sufficiently fast hydrogen flow to offset heavy element gravitational settling and can thus explain why solar wind abundances are not much smaller than photospheric abundances. We find that high first ionization potential (FIP) elements are more susceptible to gravitational settling than low-FIP elements, which are pulled up by Coulomb drag from protons, and hence the settling is more sensitive to the charge state of the elements than to their mass. Abundances at the top of the chromosphere, and hence solar wind abundances, can change by many orders of magnitude when the funnel areal expansion factor is changed by a small amount. The observed solar wind neon abundance provides the most severe constraint on the expansion, requiring a total flux tube expansion factor of at least 30-40.

Dual-Sensitive Probe of 2-(Benzoacridin)ethyl-imidazole-1-carboxylate for Determination of Aliphatic Amine with Fluorescence and Online Atmospheric Pressure Chemical Ionization Mass Spectrometry Identification

Using three different derivatization methods to mark the amine compounds, we compared the difference of derivatization efficiency and gave the optimal method. 5-(2-Hydroxyethyl)benzoacridine reacts with coupling agent N,N′-carbonyldiimidazole (CDI) to form an activated amide intermediate 2-(benzoacridin)ethyl-imidazole-1-carboxylate (BAEIC). BAEIC, which is dual-sensitive probe, reacts preferably with amino compounds at 80 °C in the presence of 4-dimethylaminopyridine (DMAP) catalyst in N,N-dimethylformamide (DMF) solvent to give the corresponding sensitively fluorescent derivatives with an excitation maximum at 280 nm of λex and an emission maximum at 510 nm of λem. BAEIC-amine derivatives simultaneously exhibited high-ionization potential with percent ionization δ changing from 5.62% to 58.08% in aqueous acetonitrile and from 2.14% to 56.58% in aqueous methanol. Derivatives are not only sensitive to fluorescence but also to MS ionizable potential. The fluorescence detection limits are 0.12–0.59 ng mL？1 (at a signal-to-noise ratio of 3). The online Atmospheric Pressure Chemical Ionization Mass Spectrometry (APCI-MS) detection limits are 1.89–14.12 ng mL？1 (at a signal-to-noise ratio of 5).

Engineering the electronic structure of the CuPc/BPE‐PTCDI interface by WO3 doping of CuPc

AbstractWe investigate the electronic interface properties of an organic bilayer heterojunction solar cell, built of CuPc/BPE‐PTCDI as donor/acceptor system. Band alignment of this interface and interface potentials were measured using synchrotron induced photoemission spectroscopy (SXPS) on stepwise deposited BPE‐PTCDI on doped and non doped CuPc. Using non doped CuPc at thermodynamic equilibrium the bands bend at the interface in a direction that hinders dissociation of geminate pairs.As a measure to form a band bending that supports geminate pair separation p‐doping of CuPc is tested. As dopant WO3 was applied being a promising material for p‐doping of CuPc due to its high ionization potential. At the doped CuPc/BPE‐PTCDI interface the internal field is actually reversed now driving holes in CuPc and electrons in BPE‐PTCDI away from the interface.

Are In 13M (M = Li, Na, K) magic clusters? – A comparison with Al 13M

Density functional study was performed on the stability of In n M ( n = 11–15, M = Li, Na, K) clusters. In 13M are characterized by electronic shell closure with enhanced stability, larger HOMO–LUMO gap, higher ionization potential, and lower electron affinity as compared with clusters of adjacent sizes, while very similar size dependence was found between In n M and Al n M in their electronic properties, suggesting that In 13M be magic clusters and promising as building blocks in developing cluster-assembled materials. The calculated AEA of In 13 is close to that of iodine, implying it would behave like a halogen atom in ionic In 13M molecule.

Penetration (intercalation) of copper atoms under a graphene layer on iridium (111)

The mechanisms of intercalation of a graphene layer (a two-dimensional graphite film) on a metal (iridium, the (111) face) with copper atoms are studied. It is shown that, in the rather narrow temperature range 1100–1200 K, a thin copper film deposited onto the graphene surface at room temperature totally breaks down, and the atoms transfer to the intercalated state, i.e., become arranged between the graphene layer and the substrate. The nature of the asymmetry of intercalation and backward escape of atoms with high ionization potentials is discussed. Due to the asymmetry, the graphene layer plays the role of a trap for such particles.

Enhanced High Harmonic Generation from Multiply Ionized Argon above 500 eV through Laser Pulse Self-Compression

By combining laser pulse self-compression and high harmonic generation within a single waveguide, we demonstrate high harmonic emission from multiply charged ions for the first time. This approach enhances the laser intensity and counteracts ionization-induced defocusing, extending the cutoff photon energy in argon above 500 eV for the first time, with higher spectral intensity and cutoff energy than He for the same input laser parameters. This Letter demonstrates a pathway for extending high harmonic emission to very high photon energies using large, multiply charged, ions with high ionization potentials.

AKARI Far-Infrared Spectroscopic Observations of the Galactic Center Region

Abstract We have observed the Quintuplet- and Arches-cluster regions with the Fourier Transform Spectrometer (FTS) of the Far-Infrared Surveyor (FIS) aboard AKARI to investigate the physical conditions of interstellar matter around the clusters. The FIS-FTS mapping data reveal differences in the spatial distribution among the far-infrared [O iii], [N ii], and [C ii] line emissions near the Arches cluster; the emission of an ionic line with a higher ionization potential is distributed closer to the Arches cluster. This clearly indicates that UV photons from the Arches cluster are ionizing the surface of nearby molecular clouds, and penetrating deeper to dissociate the cloud. We have estimated the effective temperature of the Arches cluster to be about 34000 K from the ratio of the [O iii]$/$[N ii] lines.

Fabrication of a Blue $M\times N$ Pixel Organic Light-Emitting Diode Video Display Incorporating a Thermally Stable Emitter

A 7 times 11 pixel blue OLED display was fabricated using a patterned indium-tin-oxide (ITO) substrate. The fabrication process for an M times N pixel organic light-emitting diode (OLED) video display including an electrical insulating layer and a physical pixel separator layer is presented. An efficient and thermally stable blue fluorescent organic material, 6,6'-bis((2-p -biphenyl)-4-phenylquinoline) (B2PPQ), was used in combination with an evaporated hole-transport small molecule with a high ionization potential.

Radical cations of aromatic molecules with high ionization potentials on the surfaces of oxide catalysts: Formation, properties, and reactivity

The results obtained by the authors on the formation and properties of the radical cations of benzene and other molecules with high ionization potentials on the surfaces of ZSM-5 zeolites and sulfated zirconium dioxide are analyzed in this paper. It was found that radical cations of aromatic compounds can be obtained both by a thermal process and under illumination with visible light. Radical cations were found to be key intermediates in the low-temperature polycondensation of aromatic compounds on these catalysts. A possible mechanism of the formation of radical cations and the nature of the sites responsible for these processes are discussed.

The role of carrier gases in the production of metastable argon atoms in a rf discharge

We investigate the role of carrier gases in the production of metastable argon atoms in a rf-driven discharge. The effects of different carrier gases (krypton, xenon, neon, and helium), carrier gas pressures, and rf discharge powers are examined. A xenon carrier gas provides the greatest metastable population of argon, yielding an optimal fractional metastable population of argon (Ar(*)/Ar) of 2x10(-4) at 0.2 mTorr of xenon gas. The optimal krypton configuration yields 60% of the xenon-supported population at 1.5 times higher pressure. Neon and helium perform considerably worse probably due to their higher ionization potentials.

Geometries and electronic structures of phosphorous-doped silicon fullerenes: A DFT study

Using density functional theory (DFT) calculations, we investigate the specie obtained from the stepwise on-cage P-doping of the silicon fullerene Si 20H 20. It is found that P-doping decreases the HOMO–LUMO energy gap of the fullerene and could be used to tailor its optical properties. Pairing of P atoms within the fullerene’s cage is not favored owing to the repulsion between the phosphorous lone-pairs and the preference for Si–P bond formation. Replacing all the SiH moieties with P affords the dodecahedral P 20 fullerene. The fully oxidized P 20O 20 species is characterized by exceptionally high ionization potential (10.73 eV) and large electron affinity (6.71 eV).

Doping effect of hydrogen on Al 3 cluster

The doping effect of hydrogen atoms on geometric and electronic properties of small aluminum cluster, Al 3, where deviation from the jellium model may occur, is investigated from a first-principle method. It is found that the most favorable sites for H atoms to be bound to Al atoms depend on amount of H atoms. For each cluster, Al–H bond lengths have the smallest values when the H atoms are on the top sites and have the largest values when the H atoms are on face sites, while those corresponding to bridge-site H atoms are of medium value. The doping of H increases the binding energy of the Al 3 cluster. Al 3H 3 and Al 3H 5 are found to have much lower electron affinities, higher ionization potentials and significantly larger HOMO–LUMO gaps than their neighbors, which are typical characteristics of magic clusters. The high stabilities of the Al 3H 3 and Al 3H 5 suggest that they may have a good potential applications in cluster-assembled materials.