eV Energy Research Articles

First-principles investigation of spin characteristics and thermoelectric properties in Ba2SmMoO6 and Ba2EuMoO6 double perovskites

This investigation employs first-principles calculations with the Generalized Gradient Approximation (GGA) and modified Becke-Johnson (mBJ) exchange-correlation functionals, employing the Full-Potential Linearized Augmented Plane Wave (FP-LAPW) method. The main objective is to investigate the double perovskites Ba2SmMoO6 and Ba2EuMoO6. We conduct a thorough analysis of the structural, electrical, magnetic, thermoelectric and optical properties of these materials. Both compounds are stable in ferromagnetic phase, according to structural studies. Ba2SmMoO6 has a 3.80 eV energy gap, aligned with the W-X direction, which exhibits half-metallic behavior. On the other hand, Ba2EuMoO6 has a 3.03 eV energy gap that is directly aligned with the X-X direction, using mBJ-GGA. Magnetic investigation revealed a total spin magnetic moment of 7 μB for Ba2EuMoO6, mainly due to Eu (5.98 μB) and 6 μB for Ba2SmMoO6, mainly due to Sm (4.53 μB). It was found that both materials have high Seebeck coefficients and electrical conductivities at high temperatures, with performance improving with temperature. However, the figure of merit (ZT) approaches a value of one, indicating their potential for use in thermoelectric applications at high temperatures. Ba2SmMoO6 and Ba2EuMoO6 are identified as highly favourable options for effective thermoelectric devices. The high UV absorption, the unique refractive and reflective properties offer potential in photonics, optical coatings, and other fields requiring precise light manipulation.

Probing room temperature indirect and minimum direct band gaps of h-BN

Hexagonal boron nitride (h-BN) has attracted considerable interest as an ultrawide bandgap (UWBG) semiconductor. Experimental studies focused on the detailed near band-edge structure of h-BN at room temperature are still lacking. We report a direct experimental measurement of the near band-edge structure performed on h-BN quasi-bulk wafers via photocurrent excitation spectroscopy (PES). PES resolved the band-to-band transitions near M- and K-points in the Brillion zone (BZ), from which the room temperature indirect band gap of EgMK ∼6.02 eV, minimum direct bandgap at M-point of EgM=6.36eV and next lowest direct energy bandgap at K-point of EgK=6.56eV, have been simultaneously determined for the first time experimentally. The measured energy differences between K- and M-points in the conduction band minimum (CBM) and valence band maximum (VBM) are Δ ECMK=0.54eV and Δ EVMK = 0.34 eV, respectively, in good agreement with the calculation results. Significantly differing from its III-nitride wurtzite counterparts, in which only electrons and holes in the conduction and valence band extremes at the Γ-point are predominantly involved in the optical and transport processes, the results highlighted that charge carriers associated with both M- and K-valleys control to the optical excitation, recombination and charge transport processes in h-BN.

Structure and spin of the low- and high-spin states of Fe2+(phen)3 studied by x-ray scattering and emission spectroscopy.

The structure and spin of photoexcited Fe2+(phen)3 in water are examined by x-ray scattering and x-ray emission spectroscopy with 100 ps time resolution. Excitation of the low-spin (LS) ground state (GS) to the charge transfer state 1MLCT* leads to the formation of a high-spin (HS) state that returns to the GS in 725 ps. Density functional theory (DFT) predicts a Fe-N bond elongation in HS by 0.19 Å in agreement with the scattering data. The angle between the ligands increases by 5.4° in HS, which allows the solvent to get 0.33 Å closer to Fe in spite of the expansion of the molecule. The rise in solvent temperature from the return of photoproducts to the GS is dominated by the formation dynamics of HS, 1MLCT* → HS, which is followed by a smaller rise from the HS → GS transition. The latter agrees with the 0.61 eV energy gap E(HS)-E(LS) calculated by DFT. However, the temperature rise from the 1MLCT → HS transition is greater than expected, by a factor of 2.1, which is explained by the re-excitation of nascent HS* by the 1.2 ps pump pulse. This hypothesis is supported by optical spectroscopy measurements showing that the 1.2 ps long pump pulse activates the HS* → 5MLCT* channel, which is followed by the ultrafast return to HS* via intersystem crossing. Finally, the spins of the photoproducts are monitored by the Kβ emission and the spectra confirm that the spins of LS and HS states are 0 and 2, respectively.

Study of inorganic perovskite RGaO3 (R = Rb and Na) oxide alloys for photocatalytic applications: A DFT insights

Photocatalytic technology has been hailed as one of the most promising ways to alleviate and potentially avoid both the global energy environment and consumption issues. In this regard, the perovskite RGaO3 (R = Rb and Na) oxides are investigated for water splitting applications. DFT based CASTEP code is utilized by employing GGA-PBE exchange-correlation functional. According to structural analysis, compounds have 221 space groups (cubic) with 5 atoms. The structural analysis and band structures of NaGaO3 and RbGaO3 crystals were described as having an indirect bandgap with 3.11 eV and 2.15 eV energy, respectively. Absorption, reflectivity, loss function, conductivity, refractive index, and dielectric function were all explored in terms of optical characteristics. According to the mechanical properties, compounds RGaO3 (R = Rb and Na) are mechanically stable, ductile, anisotropic, and hard by Born stability. These materials are best suited for photocatalytic applications to produce H2 fuel with the highest efficiency.

Doping dependence of boron–hydrogen dynamics in crystalline silicon

In this contribution, we investigate the formation and dissociation of boron–hydrogen (BH) pairs in crystalline silicon under thermal equilibrium conditions. Our samples span doping concentrations of nearly two orders of magnitude and are passivated with a layer stack consisting of thin aluminum oxide and hydrogen-rich silicon nitride (Al2O3/SiNx:H). This layer stack acts as a hydrogen source during a following rapid thermal annealing. We characterize the samples using low-temperature Fourier-transform infrared spectroscopy and four-point-probe resistivity measurements. Our findings show that the proportion of hydrogen atoms initially bound to boron (BH pairs) rises with increasing boron concentration. Upon isothermal dark annealing at (163 ± 2) °C, hydrogen present in molecular form, H2, dissociates at a rate directly proportional to the concentration of boron atoms, ∝ [B−], leading to the formation of BH pairs. With prolonged annealing, an unknown hydrogen complex is formed at a rate that is inversely proportional to the square of the boron concentration, ∝ 1/[B−]2, resulting in the disappearance of BH pairs. Based on experimental observations, we derive a kinetic model in which we describe the formation of the unknown complex through neutral hydrogen H0 binding to a sink. Additionally, we investigate the temperature dependence of the reaction rates and find that the H2 dissociation process has an activation energy of (1.11 ± 0.05) eV, which is in close agreement with theoretical predictions.

Cl©Li5Cl5-: A Star-like Superhalogen Anion Featuring a Planar Pentacoordinate Chlorine at the Center.

Among the known planar pentacoordinate atoms, chlorine is missing due to its large radius and high electronegativity. Herein, we report the first star-like superhalogen anion D5h Cl©Li5Cl5- (1), which contains a planar pentacoordinate chlorine (ppCl) at the center. Computer structural searches and high-level calculations reveal that 1 is a true global minimum (GM) on the potential energy surfaces. Molecular dynamics simulations indicate it is kinetically stable against isomerization or decomposition. Although detailed chemical bonding analyses reveal one delocalized 6c-2e σ bond over the Cl©Li5 central unit and five delocalized 3c-2e σ bonds along the periphery, while aromaticity has very little beneficial effect on stability, instead, ionic interaction dominates the stability of the system. More encouragingly, with the large HOMO-LUMO energy gap of 7.66 eV and vertical detachment energy of 7.87 eV, the highly chemically inert 1 can be viewed as a typical superhalogen anion and is possible to be synthesized and characterized in future experiments.

(Invited) Plasmon Induced Hot Electron Transfer from Doped Semiconductor Nanocrystals

In recent years, a new class of plasmonic materials based on doped semiconductor NCs has been developed. Similar to noble metals, localized surface plasmon resonances in doped semiconductor NCs arises from the coherent collective oscillation of free carriers within the NCs. The wide tunability of free carrier concentration results in tunable plasmon bands spanning from the visible to mid-infrared regime and these plasmonic semiconductor NCs have been reported to drive plasmonic hot carrier photocatalysis under near IR light illumination. These reports suggest that plasmonic semiconductors is an interesting material platform for efficient near IR driven hot carrier photocatalysis. So far the reported efficiencies are low and the mechanisms of hot carrier generation, transfer and recombination are unclear. There are interesting similarities and differences between metal and semiconductor plasmonics. First, plasmons in semiconductors can decay by inter- (band gap) and intra- band plasmon decay. Furthermore, charge transfer transition in semiconductor heterostructures have been extensively reported; can plasmon decay in plasmonic-semiconductor/semiconductor junctions proceed by exciting interfacial ET across the junction, similar to the PICTT pathway reported for metal/semiconductor junctions? Second, in plasmonic semiconductor materials, where there is a lack of states within the p-semiconductor bandgap, the transferred electrons in the accepting semiconductor CB can recombine only with the VB holes in the plasmonic semiconductor. This process requires dissipation of ~ >1 eV energy, which may slow down the recombination rate. In this talk, I will discuss our recent progresses in studying plasmon induced hot electron transfer and recombination in plasmonic semiconductor/semiconductor interfaces.

(Invited) Advanced Electrode Fabrication for Enhanced Battery Performance

In recent years, the highly emerging EV market evokes intensive search for more advanced batteries with higher energy density to increase the driving range and further reduce the cost. Compared to consumer electronics, automotive industry generally has critical requirements for specific characteristics of EV battery cells. Among many critical requirements on specific characteristics of EV batteries, cost and energy density are always interconnected as the main factors being considered in new battery cell designs. For advanced EV battery development, aside from scientific discovery, it’s very important to understand how cell designs, material properties, and the scaling up process play an important role in the final cost, energy density, and commercial feasibility of the batteries. When researching any new materials, In this talk, we will discuss what OEM is looking for and how to further unleash the power of battery chemistry and cell design as well as the manufacturing scaling up to expedite the advanced battery technologies for vehicle application.

Harnessing the potency of eco-friendly calcium oxide derived from eggshells for enhanced photocatalytic activity and biocompatibility evaluation in HepG2 cell line

Efforts towards sustainable development and pollution prevention are driving the exploration of bio-Calcium oxide (CaO) production from eggshell waste. This work investigates the thermal conversion of eggshell derived CaCO3 into CaO. Powder X-ray diffraction and Fourier transform infrared spectroscopy confirm CaO composition, displaying a cubic structure with 2.405 Å bond length and a mid-bond electron density of 0.2298 e/ų. Electron density studies corroborate this, revealing a three-dimensional distribution and one-dimensional profile. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirms spherical CaO particles and EDAX spectra displays the presence of calcium and oxygen. UV absorption spectra reveal a 3.3 eV energy bandgap, showcasing CaO's photocatalytic potential. It demonstrates exceptional photocatalytic against congo red and methylene blue dyes, degrading them by 96.4 % and 98 %, respectively, via pseudo first-order kinetics. Additionally, CaO demonstrates promising anticancer activity against HepG2 liver cancer cells, with an IC50 value of 31.2 μg/mL, positioning it as a cost-effective and potent agent for both wastewater treatment and cancer therapy.

Large-Scale Statistical Analysis of Defect Emission in hBN: Revealing Spectral Families and Influence of Flake Morphology.

Quantum emitters in two-dimensional layered hexagonal boron nitride are quickly emerging as a highly promising platform for next-generation quantum technologies. However, the precise identification and control of defects are key parameters to achieve the next step in their development. We conducted a comprehensive study by analyzing over 10,000 photoluminescence emission lines from liquid exfoliated hBN nanoflake samples, revealing 11 narrow sets of defect families within the 1.6 to 2.2 eV energy range. This challenges hypotheses of a random energy distribution. We also reported averaged defect parameters, including emission line widths, spatial density, phonon side bands, and Franck-Condon-related factors. These findings provide valuable insights into deciphering the microscopic origin of emitters in hBN hosts. We also explored the influence of the hBN host morphology on defect family formation, demonstrating its crucial impact. By tuning the flake size and arrangement, we achieve selective control of defect types while maintaining high spatial density. This offers a scalable approach to defect emission control, diverging from costly engineering methods. It emphasizes the significance of the morphological aspects of hBN hosts for gaining insights into defect origins and expanding their spectral control.

Ab Initio Study of the Graphyne-like γ-SiC Nanoflake for Toxic Gas-Sensing Applications.

This study focuses on the geometrical, electronic, and optical properties of the γ-graphyne-like novel γ-SiC nanoflake of the γ-silicon carbide (SiC) monolayer using density functional theory calculations. γ-SiC was revealed to be a stable semiconducting nanoflake confirmed by a negative cohesive energy, real vibrational frequencies, and a 1.749 eV energy gap. The adsorption of COCl2, HCN, PH3, AsH3, CNCl, and C2N2 toxic gases on the γ-SiC nanoflake is also studied, which revealed an attractive gas-nanoflake interaction with the adsorption energy ranging from -0.21 to -0.38 eV. The adsorption results in a significant charge transfer between gas-adsorbent complexes. A significant variation in the energy gap and electrical conductivity was observed due to gas adsorption. γ-SiC showed maximum sensitivity at room temperature for CNCl gas. The entire process of adsorption is exothermic and thermodynamically stable. γ-SiC showed a high absorption coefficient over 104 orders with a significant variation in the absorption peak intensity and blue peak shifting. According to the quantum theory and reduced density gradient analysis, all of the gases are physisorbed on the γ-SiC nanoflake due to van der Waals interactions. The obtained results signify the usability of γ-SiC as a potential toxic gas sensor.

Oblique instability of quasi-parallel whistler waves in the presence of cold and warm electron populations

Whistler waves propagating nearly parallel to the ambient magnetic field experience a nonlinear instability due to transverse currents when the background plasma has a population of sufficiently low energy electrons. Intriguingly, this nonlinear process may generate oblique electrostatic waves, including whistlers near the resonance cone with properties resembling oblique chorus waves in the Earth’s magnetosphere. Focusing on the generation of oblique whistlers, earlier analysis of the instability is extended here to the case where low-energy background plasma consists of both a “cold” population with energy of a few eV and a “warm” electron component with energy of the order of 100 eV. This is motivated by spacecraft observations in the Earth’s magnetosphere where oblique chorus waves were shown to interact resonantly with the warm electrons. The main new results are: 1) the instability producing oblique electrostatic waves is sensitive to the shape of the electron distribution at low energies. In the whistler range of frequencies, two distinct peaks in the growth rate are typically present for the model considered: a peak associated with the warm electron population at relatively low wavenumbers and a peak associated with the cold electron population at relatively high wavenumbers; 2) overall, the instability producing oblique whistler waves near the resonance cone persists (with a reduced growth rate) even in the cases where the temperature of the cold population is relatively high, including cases where cold population is absent and only the warm population is included; 3) particle-in-cell simulations show that the instability leads to heating of the background plasma and formation of characteristic plateau and beam features in the parallel electron distribution function in the range of energies resonant with the instability. The plateau/beam features have been previously detected in spacecraft observations of oblique chorus waves. However, they have been attributed to external sources and have been proposed to be the mechanism generating oblique chorus. In the present scenario, the causality link is reversed and the instability generating oblique whistler waves is shown to be a possible mechanism for formation of the plateau and beam features.

Synthesis of conjugated structural copolymer poly(3-hexylthiophene-random-benzoyl dithieno[3,2-b:2’,3’-d]pyrrole) by electrochemical method

Electrochemical copolymer synthesis of benzoyl dithieno[3,2-b:2’,3’-d]pyrrole and 3-hexylthiophene (3HT) promises to create new polymer with suitable improved HOMO and LUMO with the energy level of acceptor compounds such as Fullerene (C60) or the novel accepted organic compound in the heterojunction in organic solar cell. Electrochemical synthesis of copolymer (3-hexylthiophene-random-benzoylbdithieno[3,2-b:2’,3’-d]pyrrole by linear potential scanning method was studied and applied for synthesis of conjugated copolymer where three electrodes have been used for polymerisation including the working electrode of Indium Tin Oxide (ITO) substrate, the reference electrode of Ag/AgCl in saturated KCl and the counter electrode of platinum wire. The synthesised copolymer was characterised and evaluated through an electrochemical process, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and ultraviolet-visible spectroscopy (UV-Vis) measurements. The synthesised copolymer has a bandgap of 2.09 eV, HOMO and LUMO energy levels of -5.21 and -3.12 eV, respectively. The HOMO-LUMO of the synthesised conjugated copolymer is closed with the HOMO-LUMO of Fullerene; therefore, the conjugated copolymer is a potential material for the fabrication of organic solar cell.

Improved magnetic, electrical, and dielectric characteristics of graphene nano-platelets (GNPs)-Integrated Ni0·4Cd0·6Fe1.97Sm0.03O4 ferrite composites synthesized via sol-gel auto-combustion method

This research work analyzes the impact of graphene nanoplatelets (GNPs) on the structural, electrical, dielectric, optical, and magnetic properties of the Ni0·4Cd0·6Fe1.97Sm0.03O4/x-GNPs (SNCF/GNPs) composites (x = 0 %, 2.5 %, and 5 %) prepared via the sol-gel auto-combustion route. The results revealed that SNCF particles were distributed on GNPs which improved the multifaceted properties of SNCF spinel ferrites. XRD analysis confirmed the FCC spinel structure with a minimum crystallite size (D) of 18.99 nm for sample with 5 wt %GNPs. The DC electrical resistivity decreased from 9.06 × 1011 Ω-cm at 313K to 1.41 × 108 Ω-cm at 673K, revealing the semi-conducting nature of composites. The improved electroconductivity and reduced bandgap energy are observed for samples with minimum resistivity 1.02 × 105 Ω-cm at 673K and 1.70 eV energy, respectively, containing 5 wt %GNPs. Samples show higher permittivity values at low frequency and decreased at high frequency. The maximum ac conductivity is observed for composite with 5 wt %GNPs which is attributed to the hopping mechanism. Finally, the magnetization (Ms) increased from 52.24 to 79.71 emu/g with increasing GNPs contents. Hence, the synthesized composites with 5 wt %GNPs are more favorable than the pure sample for application in waste-water treatment, high-frequency devices, and energy storage devices.

Synthesis of bismuth vanadate by laser ablation in liquid route and its structural and optical characterization

In this work, a bottom up route was developed to obtain BiVO4 by dissociation of precursors by laser ablation. The process consisted of using a laser beam focusing on a mixture of bismuth oxide in an ammonium metavanadate solution under agitation. The precipitate obtained demonstrated high crystallinity as evidenced by the narrow peaks in the x-ray diffraction pattern and 20 nm crystallite size calculated by the Scherrer equation, approximately, and the presence of monoclinic Scheelite and tetragonal zirconia-like phases mixing. Particles showed a certain degree of agglomeration with size ranging from 400-200 nm according to SEM images. The Raman spectra showed the typical vibrational modes of mixed phases, which only changed into monoclinic scheelite after being calcined at 500 °C. The band gap was determined using Tauc plot and revealed a 2.5 eV energy band gap with a well-defined band in the visible range of spectrum for monoclinic phase samples material thermally treated. Photoluminescence results demonstrated low recombination rate for electron-hole pair indicating could be suitable in photocatalysis.

Optimal smart contracts for controlling the environment in electric vehicles based on an Internet of Things network

The scientific community has recently focused on intelligent models for predicting and optimizing EV energy management. Despite numerous studies in energy management optimization, there is a critical need to address the trade-off between energy consumption and occupant comfort. Existing IoT systems face challenges in data analytics security and authenticity, highlighting the need for contemporary models to overcome data privacy and cost-related issues. This study introduces a smart contract model based on optimization and control modules, aiming to manage energy consumption while satisfying user comfort requirements intelligently. Introducing a smart contract model with hierarchical layers—prediction, optimization, control, and Blockchain—the proposed approach intelligently manages energy consumption while meeting user comfort requirements. Utilizing a Kalman filter for prediction and the BAT algorithm for optimization, the model integrates modules to tailor user preferences and enhance comfort. The synergy between the optimization module and a convolutional FLC enhances system performance, ensuring minimized energy usage and elevated user comfort levels. The study also evaluates the model’s implementation of the Hyperledger Fabric network, assessing outcomes regarding caliper, latency, throughput, and resource utilization.

Pressure effects on the structural, electronic, elastic, optical, and vibrational properties of YMg intermetallic compounds: a first-principles study

The properties of YMg in B2 structure have been comprehensively analysed using the first-principles plane-wave pseudopotential method. Specifically, the structural, electronic, elastic, vibrational, and optical properties were investigated using the generalized gradient approximation (GGA) method in the context of density functional theory. The Vienna ab initio simulation package (VASP) was utilized for these calculations. The computed lattice parameter (3.803 Å) and bulk modulus (41.33 GPa) are consistent with the earlier data on ambient pressure. The electronic band structure and energy-dependent density of states reveal the metallic nature of the titled compounds. The Born stability requirements confirmed the mechanical stability. The analysis of Pugh’s and Poisson’s ratios and Cauchy’s pressure reveals that YMg is ductile under the pressures in consideration. According to several anisotropy indices, the compound is noticeably anisotropic both in ambient and under pressure. Our investigation includes an analysis of several fundamental mechanical parameters of the material, including the bulk modulus, the pressure derivative of the Zener anisotropy factor, Poisson’s ratio, isotropic shear modulus and Young’s modulus with a particular focus on their dependence on pressure. We have determined that the elastic constants obtained remain mechanically stable, satisfying the Born Stability conditions even at high pressures of up to 60 GPa. To explore the dynamic stability of YMg, we analysed the material’s phonon dispersion curves. The examined compound displays stability under dynamic conditions from 0 GPa to 30 GPa, as evidenced by its positive vibration frequencies. However, this stability is not sustained under higher pressure, as the compound becomes unstable after 30 GPa to 70 GPa. The electronic band structure and density of states diagrams demonstrate YMg’s metallic properties. At atmospheric pressure (0 GPa), the total density of states (TDOS) near the Fermi level is approximately 1.63 states/eV, with pressure application reducing DOS. The dielectric function, refractive index, and energy loss spectra are examined within the 0–20 eV energy range. YMg exhibits its highest absorption between 4 and 11 eV. The peak optical conductivity is observed around 0.78 eV (equivalent to 1589.5409 nm), while the most significant energy loss occurs at 11.90 eV, roughly corresponding to 2.8 Hz in the ultraviolet spectrum. Moreover, we extensively analyzed the material’s phonon thermodynamic and optical properties, providing insights into its behavior under various conditions. The outcomes acquired at zero pressure are generally coherent with the current theoretical values.

Physical and sensing characterization of nanostructured Ag doped TiO2 thin films

On glass substrates, silver (Ag) doped Titanium dioxide (TiO2) films at varied levels of concentrations (0, 2, and 4) % wt were synthesized by chemical spray pyrolysis (CSP). As per the X-ray diffraction pattern, the only phases present in the sample were anatase and rutile TiO2. Using AFM, it was discovered that the TiO2 thin films were smooth and compact; however, the surface roughness increases as the dopant amount decreases. SEM images display TiO2 films. Surface transformation is evident with uniform spherical nanograins after Ag doping. The optical characteristics of wavelength range (300-900) nm have been investigated using absorbance and transmittance spectra. The results revealed that the films have a 65-75 % transmittance in VIS-NIR spectra for all films. The allowable direct electronic transitions have (3.15-3.25) eV energy gaps. At 250 ppm, the NH3 gas sensor exhibited increased resistance, indicating heightened sensitivity. Sensitivity decreases with concentration increases to 0 %, 2 %, and 4 % of Ag for NH3 gas. Reduction observed: 18.4% to 4.6% (50 ppm), 20.7% to 6.8% (150 ppm), and 25.9% to 8.2% (250 ppm).

Predictive modeling of novel GaAgX2 (X = S, Se) chalcogenides: First-principles study of electronic, optical, and thermoelectric properties

The most prominent aspects of ternary-type chalcogenides are their tunable optical abilities and outstanding thermoelectric stability. Here the advanced density functional theory is used to examine the complicated interaction of the electronic structure, optical, thermodynamic, and thermoelectric properties of novel GaAgX2 (X = S, Se) chalcogenides. The total energies vs volume of the two materials were computed to formulate ground state characteristics. Both the materials confirmed to have direct band gap nature with an energy gap of 0.8 eV, and 2.2 eV, using TB-mBJ potential, respectively. As compared to GaAgS2, the crystal structure of GaAgSe2 have more covalent bonds that enlarged the covalency and results in wider energy gap of GaAgSe2 as compared to GaAgS2. For the negative value of ε1(ω), these materials display metallic nature, resulting to show a total reflection of the incoming photons. The GaAgS2 displays better absorption than GaAgSe2 materials with higher energy photons. With a few high peaks of refractive index in (2.8–5.5) eV energy range, suggesting these materials appropriate to be used in optical devices. These materials have positive Seebeck coefficients and are confirmed to have a p-type nature. At ambient temperature, GaAgS2 has lower thermal conductivity than GaAgSe2.

Photoionization and Dissociative Photoionization of Acetaldehyde in the 10.0-13.7 eV Range by Synchrotron Photoelectron Photoion Coincidence Spectroscopy.

Photoionization and dissociative photoionization of acetaldehyde (CH3CHO) in the 10.0-13.7 eV energy range are studied by using synchrotron radiation double imaging photoelectron photoion coincidence spectroscopy (i2PEPICO). The X2A' and A2A" electronic states of CH3CHO+ as well as the Franck-Condon gap region between these two states have been populated with several vibrational sequences and assigned in the high-resolution slow photoelectron spectrum (SPES). The adiabatic ionization energies (AIEs) of the X2A' and A2A" states are measured at 10.228±0.006 and 12.52±0.05 eV, respectively. The present results show that the X2A' state is a stable state while the A2A" state is fully dissociative to produce CH3CO+, CHO+ and CH4 + fragment ions. The 0 K appearance energies (AE0K) of CH3CO+ and CHO+ fragment ions are determined through the modeling of the breakdown diagram, i. e., AE0K(CH3CO+)=10.89±0.01 eV (including a reverse barrier of ~0.19 eV) and AE0K(CHO+)=11.54±0.05 eV. In addition, the dissociation mechanisms of CH3CHO+ including statistical dissociation, direct bond breaking and isomerization are discussed with the support of the calculated dissociation limits and transition state energies.