High Ionization Potential Research Articles

Characterizing Extreme Emission-line Galaxies. I. A Four-zone Ionization Model for Very High-ionization Emission*

Abstract Stellar population models produce radiation fields that ionize oxygen up to O+2, defining the limit of standard H ii region models (<54.9 eV). Yet, some extreme emission-line galaxies, or EELGs, have surprisingly strong emission originating from much higher ionization potentials. We present UV HST/COS and optical LBT/MODS spectra of two nearby EELGs that have very high-ionization emission lines (e.g., He ii λλ1640,4686 C iv λλ1548,1550, [Fe v]λ4227, [Ar iv]λλ4711,4740). We define a four-zone ionization model that is augmented by a very high-ionization zone, as characterized by He+2 (>54.4 eV). The four-zone model has little to no effect on the measured total nebular abundances, but does change the interpretation of other EELG properties: we measure steeper central ionization gradients; higher volume-averaged ionization parameters; and higher central T e , n e , and log U values. Traditional three-zone estimates of the ionization parameter can underestimate the average log U by up to 0.5 dex. Additionally, we find a model-independent dichotomy in the abundance patterns, where the α/H abundances are consistent but N/H, C/H, and Fe/H are relatively deficient, suggesting these EELGs are α/Fe-enriched by more than three times. However, there still is a high-energy ionizing photon production problem (HEIP3). Even for such α/Fe enrichment and very high log U s, photoionization models cannot reproduce the very high-ionization emission lines observed in EELGs.

HEATER OF THE HOLLOW CATHODE WITH LaB6 FOR OPERATION WITH HALL THRUSTERS

The article presents the results of design, development and laboratory tests at Space Electric Thruster Systems (Dnipro, Ukraine) of a hollow filament cathode based on lanthanum hexaboride (LaB6). The cathode is designed for joint operation with Hall thrusters of various input powers. The emitter material LaB6 is very promising, because has a high emissivity and low ionization potential. However, to realize all the advantages of considerate material, it is necessary to provide a sufficiently high operating temperature (1400 ° C). Therefore, when developing the filament cathode, special attention was focused on the development and research of one of the key elements of the filament cathode - the heater. Thermal calculations of the hollow cathode were carried out when it was heated with a heater, as well as when the cathode was operating in auto mode. The results of thermal calculations made it possible to identify the shortcomings of the cathode structure and parameters and determine the ways to eliminate them. Laboratory tests of a cathode with a different number of heater thermal shields have been carried out. The results obtained made it possible to provide the required operating temperature of the cathode emitter with a minimum number of heat shields. Laboratory tests of the cathode were carried out both in diode mode (to the external anode) and in conjunction with the ST-25 Hall thruster developed by the company. In the course of laboratory tests of the cathode, the power supplies for the discharge, the keeper, and the heater, which are components of the power processing unit of the Hall thruster, were used. In the frame of experimental studies, a cyclogram of the cathode starting process was obtained, which is necessary to form the Hall thruster starting sequence. The tests carried out confirmed the correctness of the selected technical solutions for the choice of the cathode and its heater. The developed cathode can be used both in low-power (up to 200 W) Hall thrusters and in thrusters with increased input power (up to 5 kW).

Electro Oxidation of Methane Under Ambient Conditions

Methane is one of the main components of natural gas, which is generally used as a worldwide energy source for daily and industrial activities. However, methane is also a kind of greenhouse gas, which has 30 times more global warming potential than that of CO2.[1] The severe methane leak problem has been underestimated for a long time. It was not gaining increasing attention until recently. Environmentally friendly converting methane to other value-added chemicals is attractive. The large-scale conventional methane reforming is under practical application that converts methane to methanol, but the two-steps endothermic reaction requires high energy input.[2] Effective decomposition of methane still remains challenging, due to the methane intrinsic chemical feature of high bond strength and high ionization potential. The unique symmetric structure makes it hard to break the C-H chemical bond and overcome the activation energy.[3] Several strategies have been built to achieve a lower energy consumption without CO2 emission, for example, photocatalyst technology, plasma technology, methanotrophs technology, electrosynthesis technology, etc. Among them, the electrosynthesis method stands out as the ideal one to oxidize methane to valuable oxygenates in a wide range of PH values and temperatures with an easy scale-up modular design.[4]In this report, we experimentally and theoretically explored the methane partial oxidation on FeNi(OH)x electrocatalysts under ambient conditions. The mixed transition metal hydroxide nanoplate compositions (Ni(OH)2, Fe10%Ni90%(OH)x, Fe20%Ni80%(OH)x, Fe30%Ni70%(OH)x, Fe50% Ni50%(OH)x) were synthesized by the facial hydrothermal method and characterized by SEM, TEM, HRTEM, XPS, and XRD techniques. The effect of incorporating Fe in the nickel hydroxide lamella structure was discussed. Evidently, Fe doping content modified the electrochemical property. We could manipulate the methane conversion process and promote the reaction selectivity by controlling the ratio of Fe in the prepared electrocatalysts. Of all the catalyst materials, Fe30%Ni70%(OH)x exhibited the best methane oxidation activity that greatly enhanced the catalytic performance. Electrochemical behavior studies were then developed in a three electrodes system to investigate methane activation regarding reaction time, applied potential, and methane partial pressure. The optimum electrode potential was determined, involving a key intermediate formation of methane activation. Under this potential, peroxide (NiOOH) formed, but oxygen evolution reaction (OER) onsite potential yet reached, thus the electrochemical performance could attain a relatively high methane oxidation current density and low competition with water oxidation. From cyclic voltammogram (CV) cycling evidence, a slight increase in the NiOOH anodic current and decrease in the OER oxidation peak current was observed in the presence of methane. The oxygenate products from methane electrooxidation were collected and analyzed by NMR and gas chromatograph (GC) instruments. Ethanol turned out to be the main product. The integrated design with ultrathin Fe30%Ni70%(OH)x nanosheet catalyst resulted in a maximum ethanol formation rate of 9.09 mmol/gcatalyst·h under 1.46 V vs. RHE with 87 % faradaic efficiency (FE) and 0.26 s-1 turnover frequency (TOF). In order to further understand the reaction mechanism, in situ attenuated total reflectance fourier transform infrared (ATR-FTIR) experiments and density functional theory (DFT) calculation were provided. We detected the HCO and CH3OH intermediates generated at the catalyst surface. DFT calculation with an ab initio modeling strongly supported the experimental results and rationalized the room temperature selective methane upgrading reaction pathways on Fe30%Ni70%(OH)x. We believe this fundamental work will provide insight and guidance in economically efficient methane conversion.[1] S. M. Miller et al., “Anthropogenic emissions of methane in the United States,” Proc. Natl. Acad. Sci., vol. 110, no. 50, pp. 20018–20022, Dec. 2013, doi: 10.1073/PNAS.1314392110.[2] X. D. Peng, “Analysis of the thermal efficiency limit of the steam methane reforming process,” Ind. Eng. Chem. Res., vol. 51, no. 50, pp. 16385–16392, 2012.[3] A. A. Latimer et al., “Understanding trends in C–H bond activation in heterogeneous catalysis,” Nat. Mater., vol. 16, no. 2, pp. 225–229, 2017.[4] A. H. B. Mostaghimi, T. A. Al-Attas, M. G. Kibria, and S. Siahrostami, “A review on electrocatalytic oxidation of methane to oxygenates,” J. Mater. Chem. A, vol. 8, no. 31, pp. 15575–15590, 2020. Figure 1

Enhancing Doping Efficiency of Diketopyrrolopyrrole-Copolymers by Introducing Sparse Intramolecular Alkyl Chain Spacing

A synthetic approach that endows high doping efficiency on high-mobility diketopyrrolopyrrole (DPP)-copolymers is described in this paper. Typical DPP-copolymers are not suitable for molecular doping, which relies on intermolecular charge transfer, presumably because of their relatively high ionization potential or weak intermolecular charge transfer characteristics between the dopant and acceptor of copolymers. Herein, we introduce new DPP-copolymers with strategically designed sparse intramolecular alkyl chain spacing where dopant molecules can reside. The resulting two type A1-D1-A2-D1 and A1-D2-A2-D2 terpolymers consist of cyclopentadithiophenes or cyclopentadithiophenyl thiophene as alternative donors, diketopyrrolopyrrole as an acceptor, and difluorinated benzothiadiazole as another acceptor. These new DPP-copolymers have significantly enhanced doping efficiency compared to conventional DPP-copolymers, exhibiting typical features of integer charge transfer, as confirmed by ultraviolet-visible-near-infrared absorption spectroscopy, electron paramagnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and thin film conductivity analyses. Moreover, doping-induced solubility control, which is not possible with other conventional DPP-copolymers due to low doping efficiency, is applicable, thus resulting in arrays of high-mobility organic field-effect transistors and complementary all-polymer inverters. This study sheds light on the possibility of tuning the doping efficiency of donor-acceptor copolymers without sacrificing their intrinsic properties, such as their well-ordered molecular packing and high charge carrier mobility.

Boosting Nitrogen Activation via Bimetallic Organic Frameworks for Photocatalytic Ammonia Synthesis

Photocatalytic ammonia synthesis from N2 is a carbon-neutral strategy, although its efficiency is impeded by the activation of inert N≡N triple bonds. In N2 activation, the electron acceptance process is often strongly coupled with the electron donation process, leading to a high potential activation energy barrier and low photocatalytic activity. Herein, we proposed a strategy to decouple these two processes by bimetallic organic frameworks (BMOFs) for boosting N2 activation. The rationally designed BMOFs are composed of two functional metal nodes, in which the hard acid metal node with a high ionization potential (In) accepts the electron from N2 and the soft acid metal node with a low In donates the electron to N2. Owing to the bimetal synergistic effect, the potential activation energy barrier of N2 is reduced, as confirmed by the in situ Fourier transform infrared (FTIR) spectra and density functional theory (DFT) calculations. Via testing six kinds of bimetal combinations, it is found that, as the ionization potential difference (ΔIn) between the two metals is ≥6 eV and the proportion of high In metal reaches ∼20%, the bimetal synergistic effect becomes dominant. In all the as-prepared BMOFs, the optimal BMOF(Sr)–0.2Fe photocatalyst exhibits an NH3 evolution rate up to 780 μmol g–1 h–1. This work may unveil a corner of the hidden mechanism for the chemical bond activation in a broad range of catalytic processes.

Trace impurity analysis in uranium materials by rapid separation and ICP-MS/MS measurement with matrix matched external calibration

Analysis of trace impurities in uranium materials is crucial for quality control in the nuclear industry and also informative for nuclear forensics. Herein we developed a rapid and high efficient method for accurate determination of 15 impurity elements (Al, Ti, Cr, Mn, Fe, Ni, Zn, Zr, Nb, Mo, Ru, Sn, Sb, Pb, Th) in uranium materials by combining chemical separation with matrix matched external calibration measurement. Uranium sample was digested, separated with the UTEVA resin and directly diluted for ICP-MS/MS measurement under optimized He collision mode. Recoveries of all the impurities exceed 90%, most of which were more than 95%. The inter-element inferences as well as the solution matrix effects on the impurity signals were investigated. The ICP-MS/MS detected signals of Zn and Sb that have high first ionization potentials were relatively more susceptible to the solution matrix compared with other impurity element signals, and thus highlighted the necessity of solution matrix matched between sample and external calibration standards. The detection limits of the proposed method ranged from ng/g to μg/g level for different impurities. The method was validated and further applied to bulk uranium ore samples. Large variation of some impurities such as Mn, Zr, Nb. Pb and Th among different ore samples were observed, which might be attributed to their different origins.

Controllable fabrication of abundant nickel-nitrogen doped CNT electrocatalyst for robust hydrogen evolution reaction

Designing highly effective and durable non-noble metal based electrocatalysts for hydrogen evolution reaction (HER) is cardinal for the sustainability of clean energy technologies. This present work explores the fabrication of nickel-nitrogen doped CNT through a simplistic approach. The as-fabricated Ni-NCNT8.0 showcases a robust HER performance amongst the other catalysts (Ni-NCNT7.5, Ni-NCNT8.5, Ni-x, and Glu-x) with a small overpotential of 147 mV and Tafel slope of 57.6 mV dec-1 to approach a current density of 10 mA cm−2 in alkaline medium. It also exhibits an excellent stability for 20 h. The high HER performance originates from the abundant and well-formed N-doped CNT that serves as conductive support and the synergy between the nickel nanoparticles which suffice as the catalyst active sites and the N-doped CNT. Additionally, the optimized electronic structure of the nickel nitrogen-doped CNT provided by density functional theory calculations, revealed a low HOMO-LUMO energy gap and high ionization potential that enhanced the stability of the electrocatalyst and conveys an effective HER.

Unprecedented saturation limit achieved by inorganic polycationic cluster (Sb7Te8)5+ for light noble gases (He & Ne)

Among noble gases, Helium and Neon have smaller size, high ionization potential and low polarizability due to which these two gases exhibit weak binding affinities toward any surface. Bartlet’s discovery and subsequent similar successful discoveries of stable complexes of noble gases opened new avenues for the storage of noble gases particularly on the new surfaces and their interactions for the storage of these gases. Here, we report the adsorption of light noble gases on polycationic clusters. Our current work not only investigates the interaction behavior of He and Ne with (Sb7Te8)5+ cluster but also explores the saturation limit of the cluster for He and Ne. Stability of various complexes of He and Ne with cationic surfaces is determined by the calculation of their interaction energies which reveal that the adsorption of single and multiple atoms of noble gases at faces of double cubic cluster is comparatively more favorable than at the bond lengths. Electronic properties such as HOMO-LUMO gaps show that complexes of He and Ne are more stable electronically than that of pure cluster, because HOMO-LUMO gap of complexes are higher than the bare polycationic cluster. NCI analysis of iso-surfaces and RDG maps confirms the presence of van der Waals forces between light noble gases and polycationic clusters. Saturation studies reveal that cluster can adsorb eleven He and/or ten Ne atoms with no or minimum distortion in the geometry of cluster. The results showed that Ne has greater tendency to interact with polycationic clusters due to the large electronic cloud and polarizability value than He.

ExoMars Mars Organic Molecule Analyzer (MOMA) Laser Desorption/Ionization Mass Spectrometry (LDI-MS) Analysis of Phototrophic Communities from a Silica-Depositing Hot Spring in Yellowstone National Park, USA.

The Mars Organic Molecule Analyzer (MOMA) is a key scientific instrument on the ExoMars Rover mission. MOMA is designed to detect and characterize organic compounds, over a wide range of volatility and molecular weight, in samples obtained from up to 2 m below the martian surface. Thorough analog sample studies are required to best prepare to interpret MOMA data collected on Mars. We present here the MOMA characterization of Mars analog samples, microbial streamer communities composed primarily of oxygenic and anoxygenic phototrophs, collected from an alkaline silica-depositing hot spring in Yellowstone National Park, Wyoming, USA. Samples of partly mineralized microbial streamers and their total lipid extract (TLE) were measured on a MOMA Engineering Test Unit (ETU) instrument by using its laser desorption/ionization mass spectrometry (LDI-MS) mode. MOMA LDI-MS detected a variety of lipids and pigments such as chlorophyll a, monogalactosyldiacylglycerol, digalactosyldiacylglycerol, diacylglycerols, and β-carotene in the TLE sample. Only chlorophyll a was detected in the untreated streamer samples when using mass isolation, which was likely due to the higher background signal of this sample and the relative high ionization potential of the chlorophyll a compared with other compounds in unextracted samples. The results add to the LDI-MS sample characterization database and demonstrate the benefit of using mass isolation on the MOMA instrument to reveal the presence of complex organics and potential biomarkers preserved in a natural sample. This will also provide guidance to in situ analysis of surface samples during Mars operations.

Computational studies of the thermodynamic properties, and global and reactivity descriptors of fluorescein dye derivatives in acetonitrile using density functional theory

This work reports density functional theory calculations of the optimized geometries, molecular reactivity, energy gap, and thermodynamic properties of molecular dyes fluorescein (FS), fluorescein attached with methoxy (FSO), fluorescein attached with amine (FSA), fluorescein attached with methane (FSM), fluorescein attached with ethene (FSE), and fluorescein attached with thiophene (FST) using the hybrid functional B3LYP and 6-311G basis sets. When donating groups are attached to the molecular dye, the bond lengths are slightly decreased which is important for easy transfer of electron from donating to the accepting group. For all dyes, highest occupied molecular orbital/lowest occupied molecular orbital analysis results in positive outcomes upon electron injection to semiconductors and subsequent dye regeneration by the electrolyte. The ionization potential increases with increasing conjugation; therefore, the molecular dye attached to thiophene has the highest ionization potential. Meanwhile, a donating group with increased conjugation results in low electron affinity.

Trends towards Effective Analysis of Fluorinated Compounds Using Inductively Coupled Plasma Mass Spectrometry (ICP-MS).

Increased demand for monitoring and identification of novel and unknown fluorinated compounds (FCs) has demonstrated the need of sensitive fluorine-specific detectors for unknown FCs in both biological and environmental matrices. Inductively coupled plasma mass spectrometry (ICP-MS) is a promising technique for analysis of FCs and has been rated as the most powerful tool in analytical chemistry. However, direct determination of fluorine using this technique is challenged by high ionization potential of fluorine together with spectral and nonspectral interferences which affect the quality of results. To enhance the quality of results, several studies have reported modifications of a conventional ICP-MS analysis procedure on sample preparation, introduction, analysis, and instrument optimization. Therefore, the focus of this study is to discuss different ICP-MS optimizations and future trends towards the effective analysis of FCs using ICP-MS.

Does Through‐Space Charge Transfer in Bipolar Hosts Affect the Efficiency of Blue OLEDs?

AbstractAdditional energy loss pathways which occur in blue electrophosphorescent devices via through‐space charge transfer (TSCT) states of bipolar hosts are identified for the first time in this study. Blue phosphorescent organic light‐emitting diodes (PhOLEDs) with maximum external quantum efficiency from 22.7 to 30.5% are fabricated using new bipolar derivatives of benzimidazole, linked through phenyl spacer with different number of tert‐butyl substituted carbazoles, as hosts. Applicability of the newly synthesized compounds as hosts for blue PhOLEDs is justified by their high triplet levels (2.94–2.98 eV), bipolar charge‐transporting properties with charge mobilities up to 2.34 × 10−3 cm2 V−1 s−1 at electric field of 2.7 × 105 V cm−1, and high ionization potentials (5.63–5.81 eV). Weak microsecond‐lived emission, which is attributed to TSCT, is detected for the developed bipolar hosts. The different efficiencies of the fabricated PhOLEDs are partly related to energy losses via TSCT states, the presence of which is detected for the developed donor–acceptor hosts in both solution and solid‐state. To prevent energy losses through TSCT in PhOLEDs, the excited state energy of emitter has to be lower than triplet levels of bipolar host. It also has to be lower than the TSCT energy level of bipolar host for the fabrication highly efficient PhOLEDs.

QSAR studies on indole-azole Analogues using DTC tools; imidazole ring is more favorable for aromatase inhibition

Quantitative structure activity relationship (QSAR) studies have been performed on indole-azole based compounds to correlate molecular descriptors and aromatase inhibitory activity using Drug Theoretics and Cheminformatics (DTC) tools. For 2- and 3- [(aryl) (azolyl)methyl]indole derivatives (set-I), MATS4s, AATS4e, and ATSC7i showed good correlation with significant R2 and Q2 values as 0.93 and 0.83, while for 1-aryl-2-[(1H-imidazol-1-yl)methyl]-6-substituted-1H-indole derivatives (set-II), the derived QSAR model showed significant R2 and Q2 values as 0.93 and 0.82 respectively, with the descriptors AVP-0, MATS7s, minHaaCH. Electronic parameters such as high electronegativity and ionization potential have unfavourable influence on anti-aromatase activity of both series of compounds. Among the imidazole and 1, 2, 4-triazole rings, imidazole nucleus is more favourable due to its low electrostatic potential. The findings of the study might guide in future designing and development of more potent indole-azole based aromatase inhibitors.

Picene and PTCDI based solution processable ambipolar OFETs

Facile and efficient solution-processed bottom gate top contact organic field-effect transistor was fabricated by employing the active layer of picene (donor, D) and N,N′-di(dodecyl)-perylene-3,4,9,10-tetracarboxylic diimide (acceptor, A). Balanced hole (0.12 cm2/Vs) and electron (0.10 cm2/Vs) mobility with Ion/off of 104 ratio were obtained for 1:1 ratio of D/A blend. On increasing the ratio of either D or A, the charge carrier mobility and Ion/off ratio improved than that of the pristine molecules. Maximum hole (µmax,h) and electron mobilities (µmax,e) were achieved up to 0.44 cm2/Vs for 3:1 and 0.25 cm2/Vs for 1:3, (D/A) respectively. This improvement is due to the donor phase function as the trap center for minority holes and decreased trap density of the dielectric layer, and vice versa. High ionization potential (− 5.71 eV) of 3:1 and lower electron affinity of (− 3.09 eV) of 1:3 supports the fine tuning of frontier molecular orbitals in the blend. The additional peak formed for the blends at high negative potential of − 1.3 V in cyclic voltammetry supports the molecular level electronic interactions of D and A. Thermal studies supported the high thermal stability of D/A blends and SEM analysis of thin films indicated their efficient molecular packing. Quasi-π–π stacking owing to the large π conjugated plane and the crystallinity of the films are well proved by GIXRD. DFT calculations also supported the electronic distribution of the molecules. The electron density of states (DOS) of pristine D and A molecules specifies the non-negligible interaction coupling among the molecules. This D/A pair has unlimited prospective for plentiful electronic applications in non-volatile memory devices, inverters and logic circuits.

Too hot for helium to handle

Stellar Populations Helium has a high ionization potential of 24.6 electron volts. Galaxies that have emission lines of He ii in their spectra must contain sufficiently hot sources, such as extremely massive stars, to ionize interstellar helium. Perez-Montero et al. modeled multiple emission lines in the spectra of a sample of galaxies that each show He ii emission. They found that the effective temperatures of the radiation fields were higher than can be explained by conventional stellar population models. The authors argue that populations of Wolf-Rayet stars with low abundances of elements heavier than helium, surrounded by clumpy gas, can explain the observations. Astron. Astrophys. 643 , A80 (2020).

Polymer Electret Improves the Performance of the Oxygen-Doped Organic Field-Effect Transistors

Chemical doping is widely used in the electronic devices. In p-type semiconductor thin films, oxygen doping fills the hole traps and increases hole concentrations, improving the performance of the organic field-effect transistors (OFETs). Due to the low ionization potential for p-type semiconductors, the superfluous holes induced by the oxygen doping degrades the OFETs off-state leakage performance. On the other hand, for p-type semiconductors with high ionization potential (up to 5.5-6.0 eV), the limited oxidation of oxygen is hard to achieve satisfactory doping concentrations to fill the trap states. This refers to the well-known intrinsic incompatibility between the oxygen doping and high-performance OFETs. Herein, a novel strategy is introduced to overcome the incompatibility and achieve high-performance OFETs by using the structural polymer electret. That is, moderate hole concentrations induced by low-pressure (30 Pa) oxygen plasma fill the hole traps within semiconductor. And the built-in field resulted from polymer electret accumulates the holes inside semiconductor near the semiconductor/electret interface, thus improving the OFETs performance. Using a model organic semiconductor with high ionization potential-2,7-didodecyl[1]benzothieno [3,2-b][1]benzothiophene (C12-BTBT) as an example, the high-performance OFETs with field-effect mobility ( $\mu _{FET}$ ) of 3.5 cm2V−1 s−1, subthreshold-swing ( SS ) of 110 mV decade−1, on-off ratio of 104, and widely-tunable threshold voltage ( ${V} _{t}$ ) are realized at a low voltage below 2 V in the open air.

Study of laser-driven multielectron dynamics of Ne atom using time-dependent optimised second-order many-body perturbation theory

We calculate the high-harmonic generation (HHG) spectra, strong-field ionisation, and time-dependent dipole-moment of Ne using explicitly time-dependent optimised second-order many-body perturbation method (TD-OMP2) where both orbitals and amplitudes are time-dependent. We consider near-infrared (800 nm) and mid-infrared (1200 nm) laser pulses with very high intensities (, , and ), required for strong-field experiments with the high-ionisation potential (21.6 eV) atom. We compare the result of the TD-OMP2 method with the time-dependent complete-active-space self-consistent field method and the time-dependent Hartree-Fock method. Further, we report the implementation of the TD-CC2 method within the chosen active space, which is also a second-order approximation to the TD-CCSD method, and present results of time-dependent dipole-moment and HHG spectra with an intensity of at a wavelength of 800 nm. It is found that the TD-CC2 method is not stable in the case with a higher laser intensity, and it does not provide a gauge-invariant description of the physical properties, which makes TD-OMP2 a superior choice to reach out to larger chemical systems, especially for the study of strong-field dynamics. The obtained results indicate that the TD-OMP2 method shows moderate performance, overestimating the response of Ne, while TDHF underestimates it..

Global helium abundance measurements in the solar corona

Solar abundances have been historically assumed to be representative of cosmic abundances. However, our knowledge of the solar abundance of helium, the second most abundant element, relies mainly on models1 and indirect measurements through helioseismic observations2, because actual measurements of helium in the solar atmosphere are very scarce. Helium cannot be directly measured in the photosphere because of its high first ionization potential, and measurements of its abundance in the inner corona have been sporadic3,4. In this Letter, we present simultaneous global images of the helium (out to a heliocentric distance of 3R⊙ (solar radii)) and hydrogen emission in the solar corona during the minimum of solar activity of cycle 23 and directly derive the helium abundance in the streamer region and surrounding corona (out to 2.2R⊙). The morphology of the He+ corona is markedly different from that of the H corona, owing to significant spatial variations in helium abundance. The observations show that the helium abundance is shaped according to and modulated by the structure of the large-scale coronal magnetic field and that helium is almost completely depleted in the equatorial regions during the quiet Sun. This measurement provides a trace back to the coronal source of the anomalously slow solar wind observed in the heliosphere at the Sun–Earth Lagrangian point L1 in 2009, during the exceptionally long-lasting minimum of solar activity cycle 23. Global images of helium and hydrogen emission are used to directly derive the helium abundance out to 2.2R⊙. The helium abundance is shaped by the large-scale coronal magnetic field. Helium is almost completely depleted near the equator in the quiet Sun.

The theoretical investigation of the opto-electronic properties of designed molecules having 2-(2-Methylene-3-oxo-indane-1-ylidene)malononitrile as end-capped acceptors

Abstract Five acceptor-donor-acceptor molecules having different core units with 2-(2-Methylene-3-oxo-indane-1-ylidene)malononitrile as end capped terminal acceptor unit were designed. The ground state geometries and electronic properties were calculated by using density functional theory (DFT) at MPW1PW91/6-31G(d,p) level of theory. The absorption spectra were computed by using time dependent DFT at MPW1PW91/6-31G(d,p) level of theory. The designed molecules have broad absorption range in visible region. M3 shows relatively lower band gap so that having high light harvesting efficiency (LHE). The molecules consider as better hole blocking materials in term of high ionization potentials. The reorganization energies calculation of M1, M2 and M4 manifests that these molecules are the optimal candidate for electron transportation. High value of Voc has been observed for molecules which would favorably contribute in power conversion efficiency. M1, M2, M4 and M5 are more stable in terms of absolute hardness and electrostatic potential surfaces. All molecules show good opto-electronic properties in the aspect of their use in photovoltaic application.

The theoretical investigation of the opto-electronic properties of designed molecules having 2-(2-Methylene-3-oxo-indane-1-ylidene)malononitrile as end-capped acceptors

Abstract Five acceptor-donor-acceptor molecules having different core units with 2-(2-Methylene-3-oxo-indane-1-ylidene)malononitrile as end capped terminal acceptor unit were designed. The ground state geometries and electronic properties were calculated by using density functional theory (DFT) at MPW1PW91/6-31G(d,p) level of theory. The absorption spectra were computed by using time dependent DFT at MPW1PW91/6-31G(d,p) level of theory. The designed molecules have broad absorption range in visible region. M3 shows relatively lower band gap so that having high light harvesting efficiency (LHE). The molecules consider as better hole blocking materials in term of high ionization potentials. The reorganization energies calculation of M1, M2 and M4 manifests that these molecules are the optimal candidate for electron transportation. High value of Voc has been observed for molecules which would favorably contribute in power conversion efficiency. M1, M2, M4 and M5 are more stable in terms of absolute hardness and electrostatic potential surfaces. All molecules show good opto-electronic properties in the aspect of their use in photovoltaic application.