eV Energy Research Articles

Electron reservoir enhances methane conversion on Zn dimer supported by N doped graphene: A DFT study

Catalytic conversion of methane to commodity chemicals is highly desired. With methods of density functional theory (DFT) computations, we investigated methane conversion to methanol (MCM) with H2O2 as oxidant over Zn dimer supported by amino nitrogen and pyridinic nitrogen co-doped porous graphene (Zn2@NPG). The facile oxidation of Zn dimer gives rise to the formation of reactive site toward methane activation. The CH3-H bond cleavage with 0.24 eV energy barrier is directly followed by the formation of methanol and regeneration of Zn2@NPG. Further analysis revealed that Zn dimer is strongly stabilized and positive charged by sharing 4 s electrons with N atoms, which ensures high-stability and good electronic conductivity of the Zn2@NPG. Amino N atom exhibits efficient electronic transfer with Zn dimer by forming two Zn-N bonds, endowing its function as an electron reservoir. Amino N as an electron donator promotes oxidation of Zn dimer and as an electron acceptor facilitates deoxidation of Zn dimer and methane conversion. The combined effect of Zn dimer and amino N atoms endows Zn2@NPG with excellent electronic structure for high activity in catalyzing MCM. This work opens a new door to accomplish low-temperature methane conversion on bi-atom catalysts (BACs).

Structural and optoelectronic properties change in Bi/In2Se3 heterostructure films by thermal annealing and laser irradiation

The amorphous materials are sensitive to external radiations and thermal annealing that brings changes in their structural and optical properties for optoelectronic applications. The present report shows the amorphous to crystalline structure transformation in Bi/In2Se3 by energy radiation and thermal annealing that modifies the linear as well as the nonlinear optical properties. The thermally evaporated Bi/In2Se3 film was subjected to 2.35 eV energy irradiation and 150 °C thermal annealing. The structural transition was probed by XRD, which revealed the formation of BiSe, Bi4Se3, and Bi2Se3 phases by replacing indium with an average crystallite size of ∼20 nm. The diffusion of Bi into In2Se3 host matrix modified the interfacial region as noticed from the field effect scanning electron microscopy pictures. The linear and nonlinear optical constants were evaluated from the UV–Visible data that show a significant change in the irradiated and annealed films due to the new phases. The change in direct and indirect bandgap is explained on the basis of density of defect states and degree of disorder. The significant change in the refractive index brings more freedom in designing multifunctional optoelectronic devices. The σopt and σelect changed noticeably with heat and energy treatment. The high value of χ3 (18.81 × 10−10 esu) for the Bi/In2Se3 film decreased significantly to 3.68 × 10−10 and 2.13 × 10−10 esu for the annealed and irradiated film. All the optical parameter changes due to annealing and irradiation are confined between the two-host materials In2Se3 and Bi/In2Se3. The corresponding changes were also observed in Raman spectroscopy data. The tuning of these linear and nonlinear parameters is useful for optoelectronics and photovoltaics.

EV Energy Convergence Plan for Reshaping the European Automobile Industry According to the Green Deal Policy

The paper dealt with the fact that the green deal took place when the demand for electrical energy surged. However, the procurement of electric vehicles and much of the electric energy of the future still depends on fossil fuels. Accordingly, the importance of the IT industry is highlighted, and the demand for hydrogen-electric vehicles and related industries increases. The method of this study investigated the relevance of EV charging as a future next-generation power source rather than the electric energy demand of the IT industry. This study derives the correlation between industrial electricity and household energy PPP according to economic growth through empirical regression analysis. As the result, it was found that the amount of change, including electric and next-generation electric vehicles, was significant for on thirds of the countries in the change in purchasing power compared to GDP. This affects overall purchasing power as twelve out of thirty two countries with EV demand (Italy, Canada, Switzerland, Poland, Slovenia, Germany, Slovakia, Finland, Sweden, Czech Republic, Estonia, Denmark) are more sensitive to electric energy. This is related to the charging of EVs or hydrogen as the next-generation power of the future rather than the electric energy demand of the IT industry. By preventing waste of unused electricity of IT-electric energy sources and charging-preserving hydrogen electricity, it seems indispensable to prepare for the national IT power conservation buffer facility for supply and demand in future growth.

Abstract P-47: Analysis of Phosphorus Distribution in Giant Bacteriophage Capsid by Electron Energy Loss Spectroscopy

Background: We have recently developed a method to visualize the distribution of DNA in the cytoplasm of bacteria by analytical electron microscopy (EM), using the Phosphorus signal (dsDNA contains two phosphate groups per each nucleotide pair), that was detected and mapped onto the image of the cell (Danilova et al, 2020; Loiko et al, 2020). Here we applied this technique to study much smaller objects – the DNA packing inside bacteriophage heads. We studied phiEL, giant phiKZ-like bacteriophage of the Myoviridae family that infects Pseudomonas aeruginosa (Krylov et al, 2003). We have earlier demonstrated that this phage contains an ‘inner body’ inside its capsid, which is responsible for the specific DNA packing (Sokolova et al, 2014). Methods: The phage propagation was performed as described before (Sokolova et al, 2014). A 3 ul sample of purified bacteriophage phiEL was applied to the glow-discharged carbon-coated copper grid and stained with freshly prepared ammonium Molybdate 2% aquatic solution for 30 sec. Grids were loaded into Gatan cooling holder and the temperature of the specimen was kept at -180°C. EELS spectra and phosphorus elemental maps were obtained on JEOL2100 microscope, operating at 200 kV with the Gatan GIF Quantum ER spectrometer in STEM mode. Pixel size was set to 15-20 nm. STEM drift correction was applied after each 40-50 pixels. Each spectrum was obtained at a 6.0 mrad collection angle, 0.25 eV dispersion, and 132 eV energy shift. The spectra from different pixels were aligned to carbon K-edge. Results: Phosphorus mapping inside and outside the bacteriophage capsid was performed (Fig. 1). Outside the capsid, the phosphorus signal was practically absent, which corresponds to the presence of DNA only inside the capsid. The distribution of phosphorus inside the capsid was uneven: the rectangular area in the middle of the capsid contained a weak signal, while a more intense signal was detected on the periphery. This can be explained by the presence of an ‘inner body’ inside (Fig. 1C). Conclusion: Thus, our results justify the possibility of using the analytical EM technique to study the distribution of DNA by mapping Phosphorus in biological nano-objects at relatively low content of the element.

A europium (III) complex tested for deoxyribonucleic acid-binding, bovine serum albumin binding, and antibacterial activity

An original complex with europium is fabricated and characterized using infra-red spectroscopy, ultraviolet–visible spectroscopy, and elemental analysis as well as an Extended X-ray Absorption Fine Structure (EXAFS) for europium absorption edge at 6977 eV energy. The ligands were completely coordinated regarding the metal with four nitrogen sites for [Eu(dafone)2Cl2.(H2O)2]Cl·H2O, such that dafone is 4,5-diazafluoren-9-one. Close-neighbor correlations from nitrogen atoms on macrocyclic cages are evident within the EXAFS spectrum. Distorted octahedral structures of the europium (III) complex were examined by utilizing EXAFS and XANES methods. The final resulted bond-length for Eu atom with O, N, and Cl are 2.36±0.05Å, 2.52±0.08Å, and 2.76±0.06Å, respectively. The coordination number for O, N, and Cl atoms are 1.94, 4.48, and 1.89, where the total coordination number is 8.31 for the central Eu atom. The binding properties of the europium samples with bovine serum albumin (BSA) and deoxyribonucleic acid (DNA) were also evaluated. The interaction mode of DNA and the complex in this work was studied based on the UV–Vis absorption titration, fluorescence titration, circular dichroism spectroscopy, viscometric assessment, thermodynamic study, ionic strength measurement and competitive binding test. The outcomes show that the complex binds to fish salmon DNA at adequate intercalation. Also, this study reveals an excellent binding property of this complex with BSA proteins. The in vitro fish salmon DNA binding activity of the samples was studied to determine the antibacterial effect of the Eu-complex on an on several gram-negative and gram-positive bacteria.

Self-cleaning and bouncing behaviour of ion irradiation produced nanostructured superhydrophobic PTFE surfaces

The bouncing dynamics of impacting water droplet on low energy ion beam produced superhydrophobic PTFE surfaces was investigated for the self-cleaning application. Ion beam with 300 eV and 800 eV energies was used to produce nanostructures on PTFE surfaces having the bouncing behaviour. The bouncing dynamics of water droplet was studied using dynamics parameters like spreading factor (β), contact time (tc), time of flight (ta) and number of bounces. The maximum spreading factor for the impact velocity of 0.5 m s−1 and 1.0 m s−1 was found to be 1.4 and 2.0, respectively for both 300 eV and 800 eV irradiated surfaces. The contact time of impacted droplet on 800 eV irradiated surface with 0.5 m s−1 velocity was found to be much lower (tc = 13.00 ms) than 300 eV ion irradiated surface (tc = 19.67 ms). Post impact bouncing number as high as 14 was found for 800 eV irradiated surface. Depending on ion energy and irradiation time the surface was converted from complete wetting to complete bouncing at low impact velocity of 0.5 m s−1 and from complete bouncing to partial bouncing at 1.0 m s−1. The self-cleaning property on 800 eV irradiated surface was successfully demonstrated using carbon powder.

Decomposition mechanism on different surfaces of copper azide

Copper azide, a potential primary explosives that may replace traditional primers such as lead azide, mercury fulminate and silver azide, has received widespread attention, but its decomposition mechanism remains unclear. Here, based on first-principles calculations, (010)N3, (100)N3 and (001) facets with a copper/nitrogen atom ratio of 1/6 are found to be the most stable surfaces of copper azide crystal. Through transition state (TS) calculations, we find that during the decomposition process on the surface, there is a synergy effect between two Cu–N1–N2–N3 chains, where the terminal N2–N3 bonds on two chains break simultaneously, and the dissociated N3 atom bonds with another N3′ atom of adjacent chain to form a N2 molecule. Next, the Cu–N bond will rupture, and two more N2 molecules (N1–N2, N1′–N2′) desorb from the surface. The overall reaction releases above 4 eV energy at a barrier of 1.23 eV on (001) surface. Electronic structure calculations reveal that the TS of N2–N3 rupture is more stabilized than that of N1–N2. According to the above results, we propose a new decomposition mechanism based on simulations of N–N bond breaking on different surfaces of copper azide. The results underscore the surface effect in decomposition of energetic materials.

Fabrication NiO: Cu / Si Heterojunction by the Aerosol-Assisted Chemical Vapor Deposition (AACVD)

In this research, as the thin films were formed by an AACVD process, copper doped nickel oxide was used to prepare the Cu doped Ni thin films by ratio doping (Cu/Ni = 0, 7.5, 10 and 12.8 at w.t %). Thin films of Cu doped NiO were heated at a crystallization temperature of 400 °C for 2 hours. The thin films obtained by the AACVD method have a film thickness of the order (45-62 nm). Promising solar cells that could be created by NiO film as the absorber using Cu doping. The NiO:Cu film has promising optical characteristics; about (3.5-2.8 eV) energy gap band and a high absorption coefficient, which means that the most suitable absorber can be commercially developed using the NiO:Cu film. Furthermore, there are no rare metals in the NiO: Cu film The best conversion efficiency with the heterojunction of NiO: Cu/Si and NiO:Cu was 2.8571429% which showed the possibility of a very low cost solar cell.

Photoionization Cross-Sections of Carbon-Like N+ Near the K-Edge (390–440 eV)

High-resolution K-shell photoionization cross-sections for the C-like atomic nitrogen ion (N+) are reported in the 398 eV (31.15 Å) to 450 eV (27.55 Å) energy (wavelength) range. The results were obtained from absolute ion-yield measurements using the SOLEIL synchrotron radiation facility for spectral bandpasses of 65 meV or 250 meV. In the photon energy region 398–403 eV, 1s⟶2p autoionizing resonance states dominated the cross section spectrum. Analyses of the experimental profiles yielded resonance strengths and Auger widths. In the 415–440 eV photon region 1s⟶(1s2s22p2 4P)np and 1s⟶(1s2s22p2 2P)np resonances forming well-developed Rydberg series up n=7 and n=8 , respectively, were identified in both the single and double ionization spectra. Theoretical photoionization cross-section calculations, performed using the R-matrix plus pseudo-states (RMPS) method and the multiconfiguration Dirac-Fock (MCDF) approach were bench marked against these high-resolution experimental results. Comparison of the state-of-the-art theoretical work with the experimental studies allowed the identification of new resonance features. Resonance strengths, energies and Auger widths (where available) are compared quantitatively with the theoretical values. Contributions from excited metastable states of the N+ ions were carefully considered throughout.

Recent Advances in the Plasma-Assisted Synthesis of Zinc Oxide Nanoparticles

An overview of recent work on the low-temperature plasma-assisted synthesis of zinc oxide (ZnO) nanoparticles is presented and interpreted in terms of gas-phase and surface reactions with illustrated examples. The thermodynamical nonequilibrium conditions allow the formation of chemically reactive species with a potential energy of several eV, which readily interact with the Zn precursors and initiate reactions leading to the formation of nanoparticles or nanowires. The high-quality nanowires were synthesized from Zn powders only upon interaction with moderately ionized plasma in a narrow range of plasma parameters. This technique is promising for the synthesis of large quantities of nanowires with aspect ratios well above 10, but the exact range of parameters remains to be determined. Apart from the ex situ techniques, the ZnO nanoparticles can be synthesized by depositing a film of precursors (often Zn salts or Zn-containing organometallic compounds) and exposing them to oxygen plasma. This technique is useful for the synthesis of well-adherent ZnO nanoparticles on heat-sensitive objects but requires further scientific validation as it often leads to the formation of a semicontinuous ZnO film rather than nanoparticles. Both low-pressure and atmospheric plasmas are useful in converting the precursor film into ZnO nanoparticles despite completely different mechanisms.

Probing of nuclear radiation attenuation and mechanical features for lithium bismuth borate glasses with improving Bi2O3 content for B2O3 + Li2O amounts

Against photon energies extending from 0.015 to 15 MeV, MCNPX, FLUKA and PHITS codes are operated to simulate mass attenuation coefficients (μ/ρ) for a total of ten B2O3-Bi2O3-Li2O glass compositions with added Bi2O3 amount from 10 to 55 mol% (5 mol% growth gradually) as a substitute for total (B2O3 + Li2O) mol% content. All the computed μ/ρ values correctness is examined by Py-MLBUF and WinXCOM programs’ μ/ρ outcomes and we found a good agreement among them. 55Bi2O3-35B2O3-10Li2O (mol%) glass half-value layer (HVL) and mean free path (MFP) quantities are compared with distinct commercial γ-ray attenuating glasses, alloys, polymers, concretes and lead and ceramics corresponding values. Next, equivalent atomic numbers (Zeq) and by employing geometric progression (G–P) fitting method at 1–40 mfp PDs (penetration depths), at 0.015–15 MeV energy range ‘buildup factors’ were calculated. At all chosen twenty-five energies derived radiation protection efficiency (RPE) results assured investigated samples exemplary competence for low energy photons absorption. Applying SRIM codes ΨP and ΦP and ΨA and ΦA (mass stopping powers (MSPs) and projected ranges (PRs) for protons and α-particles), and making use of ESTAR database ΨE (electron MSP) and continuous slowing‐down approximation (CSDA) range for electrons are determined at KE (kinetic energy) range of 0.015–15 MeV. Moreover, fast neutron removal cross-sections (ΣR), for 0.0253 eV energy neutrons absorption cross-sections have been estimated. Deduced ΣR was altered at 0.1105–0.1205 cm−1 range with Bi2O3 inclusion in studied samples. 10Bi2O3-70B2O3-20Li2O (mol%) glass has greater total cross-section (=23.251 cm−1) for thermal neutrons absorption while 55Bi2O3-35B2O3-10Li2O (mol%) sample exhibits quality shielding factors for photons and fast neutrons confirming the included Bi2O3 positive impact. Along with nuclear attenuation features various physical and mechanical aspects are also inspected. Derived Vm (molar volume), OPD (oxygen packing density), Vo (oxygen molar volume), Vt (packing density) and Gt (dissociation energy per unit volume) values indicated glasses rigidity. Following Makishima–Mackenzie's theoretical model primary mechanical features like Y, K, S and L (Young's, bulk, shear and longitudinal modulus) and σ (Poisson's ratio) are evaluated where 10Bi2O3-70B2O3-20Li2O (mol%) glass shows better elastic moduli in all samples.

IceCube-Gen2: the window to the extreme Universe

The observation of electromagnetic radiation from radio to γ-ray wavelengths has provided a wealth of information about the Universe. However, at PeV (1015 eV) energies and above, most of the Universe is impenetrable to photons. New messengers, namely cosmic neutrinos, are needed to explore the most extreme environments of the Universe where black holes, neutron stars, and stellar explosions transform gravitational energy into non-thermal cosmic rays. These energetic particles have millions of times higher energies than those produced in the most powerful particle accelerators on Earth. As neutrinos can escape from regions otherwise opaque to radiation, they allow an unique view deep into exploding stars and the vicinity of the event horizons of black holes. The discovery of cosmic neutrinos with IceCube has opened this new window on the Universe. IceCube has been successful in finding first evidence for cosmic particle acceleration in the jet of an active galactic nucleus. Yet, ultimately, its sensitivity is too limited to detect even the brightest neutrino sources with high significance, or to detect populations of less luminous sources. In this white paper, we present an overview of a next-generation instrument, IceCube-Gen2, which will sharpen our understanding of the processes and environments that govern the Universe at the highest energies. IceCube-Gen2 is designed to:(a) Resolve the high-energy neutrino sky from TeV to EeV energies(b) Investigate cosmic particle acceleration through multi-messenger observations(c) Reveal the sources and propagation of the highest energy particles in the Universe(d) Probe fundamental physics with high-energy neutrinosIceCube-Gen2 will enhance the existing IceCube detector at the South Pole. It will increase the annual rate of observed cosmic neutrinos by a factor of ten compared to IceCube, and will be able to detect sources five times fainter than its predecessor. Furthermore, through the addition of a radio array, IceCube-Gen2 will extend the energy range by several orders of magnitude compared to IceCube. Construction will take 8 years and cost about $350M. The goal is to have IceCube-Gen2 fully operational by 2033.IceCube-Gen2 will play an essential role in shaping the new era of multi-messenger astronomy, fundamentally advancing our knowledge of the high-energy Universe. This challenging mission can be fully addressed only through the combination of the information from the neutrino, electromagnetic, and gravitational wave emission of high-energy sources, in concert with the new survey instruments across the electromagnetic spectrum and gravitational wave detectors which will be available in the coming years.

Green Perovskite Light‐Emitting Diodes with 200 Hours Stability and 16% Efficiency: Cross‐Linking Strategy and Mechanism

AbstractAccording to the thinner emitting layer and stronger electric field in perovskite light‐emitting diodes (PeLEDs) than those in perovskite solar cells, the strong electric‐field‐driven ion‐migration is a key issue for the operational stability of PeLEDs. Here, a methylene‐bis‐acrylamide cross‐linking strategy is proposed to both passivate defects and suppress ion‐migration with an emphasis on the suppressing mechanism via in situ investigations. As typical results, in addition to the enhanced external quantum efficiency (EQE, 16.8%), PeLEDs exhibit preferable operational stability with a half lifetime (T50) of 208 h under continuous operation with an initial luminance of 100 cd m−2. Moreover, the EQE of cross‐linked LEDs can maintain above 15% during 25 times scanning as the devices are measured every 4 days. To the authors’ knowledge, this is the highest stability published until now for high‐efficiency PeLEDs with EQE over 15%. The in situ/ex situ mechanism investigation demonstrates that such cross‐linking increases binding energy from 0.54 to 0.92 eV and activation energy from 0.21 to 0.5 eV. Hence, it suppresses ligands breaking away and ion migration, which prevents ions from moving inside and across crystals. The proposed cross‐linking passivation strategy thus provides an effective methodology to fabricate stable perovskites‐based photoelectric devices.

Ro-vibrational Distribution of NO+ Dissociated from NO2+ Ions in the a3B2 and b3A2 States: A Slow "Impulsive" Dissociation Example Revealed from Threshold Photoelectron-Photoion Coincidence Imaging.

To clarify the contentions about dissociative photoionization mechanism of nitrogen dioxide via the a3B2 and b3A2 ionic states, a new threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging has been conducted in the 12.8-14.0 eV energy range at the Hefei Light Source. The fine vibrational-resolved threshold photoelectron spectrum agrees well with the previous measurements. The ro-vibrational distributions of NO+, as the unique fragment ion in the dissociation of NO2+ in specific vibronic levels of a3B2 and b3A2 states, are derived from the recorded TPEPICO velocity images. A "cold" vibrational (v+ = 0) and "hot" rotational population is observed at the a3B2(0,3,0) and (0,4,0) vibronic levels, while the dissociation of NO2+ in b3A2(0,0,0) leads to the NO+ fragment with both hot vibrational and rotational populations. With the aid of the quantum chemical calculations at the time-dependent B3LYP level, minimum energy paths on the potential energy surfaces of the a3B2 and b3A2 states clarify their adiabatic dissociation mechanisms near the thresholds, and this study proposes reliable explanations for the observed internal energy distributions of fragment ions. Additionally, this study provides valuable insights into the application of the classical "impulsive" model on an overall slow dissociation process.

Experimental studies on photoabsorption by endohedral fullerene ions with a focus on Xe@C60 + confinement resonances

A brief overview on the status of experimental investigations into photoionization and fragmentation of fullerenes and endohedral fullerenes by absorption of a single short-wavelength photon is presented. The focus of this paper is on the endohedral Xe@C60 + molecular ion in which a xenon atom is centrally encapsulated inside a fullerene cage. Confinement resonances that result from the interference of Xe photoelectron matter waves emerging from the cavity were studied by exposing Xe@C60 + ions to synchrotron radiation of 60 to 150 eV energy which is the region of the well-known giant atomic Xe excitation resonance. Photoions Xe@C n q+ (with final charge states of the product ions and numbers of carbon atoms left in the cage) were recorded as a function of photon energy and cross sections for the individual reaction channels were determined. In addition to previous work, new final channels ( and ) were observed, and thus, about 70% of the oscillator strength expected for the encapsulated Xe atom in the investigated energy range could be recovered. The present results establish the first and, so far, only conclusive experimental observation of confinement resonances in an endohedral fullerene. The data are in remarkable agreement with relativistic R-matrix calculations that accompanied the previous experimental work.

Computational Exploration of Structural, Electronic, and Optical Properties of Novel Combinations of Inorganic Ruddlesden–Popper Layered Perovskites Bi2XO4(X = Be, Mg) using Tran and Blaha‐Modified Becke–Johnson Approach for Optoelectronic Applications

Herein, the layered perovskites Bi2XO4(X = Be, Mg) have been taken into account to probe into their structural and optoelectronic behavior using an ab initio technique which is solely reliant on density functional theory (DFT). To compute an improved electronic bandgap and encounter accurate contribution from d/f electronic states, the Tran and Blaha‐modified Becke–Johnson functional is used systematically, which has been considered an adequate approach to overcome limitations of the PBE–GGA functional. The conduction band minima (CBM) and the valence band maxima (VBM) are located at different values of the wave vectors yielding a noticeable indirect energy gap such as 2.80 eV for Bi2BeO4and 2.40 eV for Bi2MgO4, which discloses that studied perovskites belong to the semiconductor category. The density of states exposes that Bi‐6p states contribute in the conduction region in vicinity of 5 eV energy. Whereas Be‐s orbitals are contributing in the far region of the conduction bands. O‐2p states are located in lower energy range associated with valence bands. Large values of formation and cohesive energy of compounds indicate that these are more stable and not easily decomposable under ambient conditions. The minimal reflectivity endorses our contention that these perovskites might be very useful for potential applications in optoelectronics.

Experimental investigation on particle size and launch angle distribution of lofted dust particles by electrostatic forces

Electrostatic dust transportation is one of the fundamental sources for dust activity on airless planetary bodies. Even though a series of laboratory experiments have been performed to improve our understanding of the physics behind the electrostatic dust mobilization, there are several factors to investigate such as the launch angles, the lofted particle sizes, the traveling distance of the lofted grains, the initial acceleration to the launching velocities and so on. In this experimental study, an electron beam is used with 450 eV energy to produce secondary electrons to initiate lofting of the silica microspheres in the vacuum chamber, and the particle trajectories are recorded with a microscopic telescope and a high-speed camera. The dust samples are prepared as a mixture of particles with sizes from several micrometers to approximately 90.0 μ m in radius. In addition, a polyimide tape with the adhesive surface is placed around the dust sample to collect the lofted particles up to approximately 10.0 cm distance. The collected silica microspheres are studied under the microscope to measure the size variation over the distance from the dust source. The experiment results show that spherical particles and residues effortlessly reach up to 10 cm distance, whereas the fluffy dust aggregates are observed particularly near the dust sample. In addition, the analysis of trajectories shows that the dust grains accelerate rapidly to their launching velocities below 12.0 ms due to the repulsion between the neighboring dust particles. Finally, the peak of the dust launching angle distribution is determined to be around 43.5–45° from the surface normal.

First principles study of Bi12GeO20: Electronic, optical and thermodynamic characterizations

Bismuth germanium oxide (Bi12GeO20) is one of the attractive members of sillenite compounds having fascinating photorefractive characteristics. The electronic, optical and thermodynamic properties of Bi12GeO20 were investigated using density functional theory (DFT) calculations. The experimental and calculated X-ray diffraction patterns were obtained as well-consistent with each other. The lattice constant of the cubic crystalline structure of Bi12GeO20 compound was calculated as 10.304 Å. The electronic band structure and partial density of states plots were reported and contribution of constituent atoms (Bi, Ge, O) to the valence and conduction bands was presented. The band gap energy of the Bi12GeO20 was calculated as 3.20 eV. This wide direct band gap energy provides Bi12GeO20 significant potential in ultraviolet applications. The spectra of real and imaginary components of dielectric function, refractive index, extinction coefficient and absorption coefficient were drawn in the 0−10 eV energy range. Temperature-dependent heat capacity plot indicated the Dulong-Petit limit as 825 J/mol.K. The results of the present study would present worthwhile information to device application areas of Bi12GeO20 compound.

Photoionization Cross Section of the NH2 Free Radical in the 11.1-15.7 eV Energy Range.

The NH2 radical is a key component in many astrophysical environments, both in its neutral and cationic forms, being involved in the formation of complex N-bearing species. To gain insight into the photochemical processes into which it operates and to model accurately the ensuing chemical networks, the knowledge of its photoionization efficiency is required, but no quantitative determination has been carried out so far. Combining a flow-tube H-abstraction radical source, a double imaging photoelectron-photoion spectrometer, and a vacuum-ultraviolet synchrotron excitation, the absolute photoionization cross section of the amino radical has been measured in the present work for the first time at two photon energies: σionNH2(12.7 eV) = 7.8 ± 2.2 Mb and σionNH2(13.2 eV) = 7.8 ± 2.0 Mb. These values have been employed to scale the total ion yield previously recorded by Gibson et al. ( J. Chem. Phys. 1985, 83, 4319-4328). The resulting cross section curve spanning the 11.1-15.7 eV energy range will help in refining the current astrophysical models.

Electron-impact ionization and ionic fragmentation of O2from threshold to 120 eV energy range

We study the electron-impact induced ionization of O2from threshold to 120 eV using the electron spectroscopy method. Our approach is simple in concept and embodies the ion source with a collision chamber and a mass spectrometer with a quadruple filter as a selector for the product ions. The combination of these two devices makes it possible to unequivocally collect all energetic fragment ions formed in ionization and dissociative processes and to detect them with known efficiency. The ion source allows varying and tuning the electron-impact ionization energy and the target-gas pressure. We demonstrate that for obtaining reliable results of cross-sections for inelastic processes and determining mechanisms for the formation of O[Formula: see text] ions, it is crucial to control the electron-impact energy for production of ion and the pressure in the ion source. A comparison of our results with other experimental and theoretical data shows good agreement and proves the validity of our approach.