Oxygen Band Research Articles

Impact of molybdenum on structural and morphological properties of manganese ferrite nanoparticles by hydrothermal method

The study of transition metal ferrites have vast applications from microwave to radio-wave frequencies and are of great importance from both fundamental as well as in research aspect. Based on their magnetic properties, transition metal ferrites are found to have low magnetic anisotropies and are magnetically categorized as soft. Manganese ferrites are a group of soft spinel ferrite materials with high magnetic permeability, high electrical resistance and low loss. The doping of molybdenum improves its resistivity, strength and toughness. Due to their excellent electrical and magnetic properties, spinel ferrites are technologically important ceramic materials. As transition takes place from micron to nano regime, these materials are found to be with excellent chemical stability, moderate saturation magnetization and low eddy currents especially in spinel ferrites. In this present work, nanocrystalline ferrites MnxMo1-xFe2O4 of x varies as 0.4, 0.6 and 0.8 are synthesized by hydrothermal method. The prepared nanocrystalline ferrites are characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Energy Dispersive X-Ray Analysis (EDX) and Scanning Electron Microscopy (SEM) for analyzing its structural, functional groups and morphological structures. XRD analysis reveals that the resultant ferrite nanoparticles are found to have cubic structure. FT-IR spectral analysis shows two main broad metal–oxygen bands and confirms the presence of spinel ferrites. EDX analysis confirms the quantitative presence of elements without impurities. This study aims to fabricate the ferrites with better physical and magnetic properties that are useful in a variety of applications such as magnetic sensors, heavy metal removal and transducers.

Structural, dielectric and magnetic properties of (ZnFe2O4/Polystyrene) nanocomposites synthesized by micro-emuslion technique

This work aims to study the effect of polymer on the structure, magnetic and dielectric properties of spinel ferrite composite. Nanocomposites based on polystyrene (PST)/ZnFe2O4 were synthesized by using the micro-emulsion method. The novel composites with PST to ZnFe2O4 ratios (4:0, 4:1, 4:2, 4:3, 4:4, 0:4) were analyzed by X-ray diffractometer (XRD) which confirms the spinel structure of ZnFe2O4 with an average crystallite size of 15.3 nm for pure ZnFe2O4 and decreases by increasing the polystyrene concentration. Field Emission Scanning Electron Microscopy (FESEM) gave the optimized results of surface morphology and the crystallite size which are in accordance with XRD data. Fourier Transform Infrared (FTIR) spectra show two main broad metal–oxygen bands corresponding to the intrinsic stretching vibrations of the metal at the tetrahedral site (observed between 837.9 and 1034.3 cm−1) and traces of organic materials were observed at 1499.2 and 1766.4 cm−1, which are associated with CO and CC stretching vibration respectively. O–H stretch of COOH weak acid of the carboxyl group was found at 2978.7 cm-1. The composite with equal ZnFe2O4 to PST ratio (4:4) shows that real part of dielectric constant is independent of frequency at lower frequencies of an applied electric field. The resonance type behaviour was observed at higher frequency (2.5 GHz) which shows the material is excellent for dispersion of electric part of microwaves. The magnetization for pure ferrite (ZnFe2O4) at 15000 Oe was found to be 1.49 emu/g which decreases to 0.54 emu/g for the composite with the equal ferrite to polystyrene ratio. Based on their dielectric and magnetic characterization, these composites are considered suitable candidates to employ as microwave absorbing materials.

Synthesis and Characterisation of Copper Substituted Cobalt Ferrite Nanoparticles by Sol-Gel Auto Combustion Route

In the present study, the structural, functional, morphological and magnetic characteristics of copper substituted cobalt ferrite nanoparticles were investigated. The samples of Co1-xCuxFe2O4 at x = 0.06, 0.08 and 0.1 M were prepared by Sol-gel auto combustion route. X-ray diffraction technique was used to confirm the phase formation and structural analysis which matches with the JCPDS Data. The average crystallite size was found to be ∼25, ∼19 and ∼18 nm for x = 0.06, 0.08 and 0.1 respectively. The Micro Raman Spectroscopy revealed the stretching vibrations at 274 cm−1, 660 cm−1, and 466 cm−1, which are characteristic of Spinel Ferrites. From the FTIR analysis, the band observed at 3457cm−1 and 1650 cm−1 is assigned to hydrogen bonded O-H group and ionic stretching of C-H bond. The band assigned at 1105 cm−1, is due to Co – O and Cu - O or Fe – O vibrations. The existence of water adsorption band and metal oxygen band confirms the existence of Co and Cu in the synthesized sample. The surface morphology of samples was imaged by the field emission scanning electron microscope. The substitution of Cu2+ in the parent systems caused a significant reduction in particle size. The compositional analysis was done, which confirmed that the concentration of copper was increased in the samples. The samples were subjected to magnetic characterization because magnetic behavior is also affected by substitution of Copper in Cobalt ferrite. Magnetic hysteresis study at room temperature confirmed the reduction in saturation magnetization (MS = 14.25 to 8.33 emu/g.) and reduction in coercivity (HC = 602.64 to 380.94 Oe) when size is reduced. As the concentration of Cu into CoFe2O4 matrix increases, particle size decreases and the saturation magnetization decreases.

Symmetrical phthalocyanine bearing four triptycene moieties: Synthesis, photophysical and singlet oxygen generation

Novel metal-free (7) and zinc(II) (8) phthalocyanine derivatives bearing four substituted triptycene moieties were synthesized and fully characterized by various spectroscopic methods including 1H-NMR, 13C-NMR, mass, FT-IR and UV-vis. Photophysical and photochemical properties such as electronic absorption, fluorescence emission, fluorescence lifetimes and singlet oxygen generation were investigated in toluene. The UV-vis spectra of 7 and 8 exhibited absorption bands in the visible region. The fluorescence lifetimes of 7 and 8 phthalocyanines were found to be 6.2 and 3.6 ns, respectively. The ability of the examined zinc(II) (8) and metal-free (7) to produce the singlet oxygen has been determined by both chemical and direct methods. While the chemical method 1,3-diphenylisobenzofuran (DPBF) as a singlet oxygen quencher was used in the first method, the direct determination has been done by recording the weak emission band of the singlet oxygen in the near-infrared region (1270 nm). From the direct process, the quantum yields of the singlet oxygen were found to be 0.28 (for 7) and 0.60 (for 8) and similar values were also obtained by the chemical method. The fluorescence quenching behavior of the studied phthalocyanine compounds (8 and 7) by electron-accepting 1,4 benzoquinone (BQ) was also studied in toluene. The powerful nanosecond laser flash photolysis technique was also employed to record the transient absorption spectra of the long-lived triplet states of the investigated compounds.

Coupled cluster study of the x-ray absorption spectra of formaldehyde derivatives at the oxygen, carbon, and fluorine K-edges

We have investigated the performance of a core-valence separated scheme within the coupled cluster (CC) hierarchy of methods CC singles (CCS), CC singles and approximate doubles (CC2), and CC singles and doubles (CCSD) in reproducing the K-edge x-ray absorption spectra of the low-Z elements carbon, oxygen, and fluorine in formaldehyde (CH2O), carbonyl fluoride (CF2O), formyl fluoride (CHFO), and formic acid (CHOOH). The analysis covers the entire frequency region from the first 1s → π* excitation to the core-ionization limit, encompassing the region of Rydberg transitions. Moreover, a simulation of the vibronic progressions in the 1s → π* bands of both carbon and oxygen in formaldehyde has been performed at the core-valence separated CCSD level, and the results are critically compared with highly resolved experimental data for this molecule.

Instrument predevelopment activities for FLEX mission

The fluorescence imaging spectrometer (FLORIS) is the payload of the fluorescence explorer mission (FLEX) of the European Space Agency. The mission objective is to perform quantitative measurements of the solar-induced vegetation fluorescence aiming at monitoring photosynthetic activity. FLORIS works in a push-broom configuration, and it is designed to acquire data in the 500 to 780 nm spectral range with a sampling of 0.1 nm in the oxygen bands (759 to 769 nm and 686 to 697 nm) and 0.5 to 2.0 nm in the red edge, chlorophyll absorption, and photochemical reflectance index bands. FLEX will fly in formation with Sentinel-3 to benefit from the measurements made by Sentinel-3 instruments, OLCI, and SLSTR, particularly concerning the cloud screening, the proper characterization of the atmospheric state, and the determination of the surface temperature. The instrument concept is based on a common telescope and two modified Offner spectrometers with reflective concave gratings both for the high resolution (HR) and low resolution (LR) spectrometers. In the frame of the instrument predevelopment, Leonardo Company (Italy) has built and tested an elegant breadboard of the instrument consisting of the telescope and the HR spectrometer. OHB System AG (Germany) is in charge of the development of the LR spectrometer. The main objectives of the activity are to anticipate the development of the instrument and provide early risk retirement of the critical components; evaluate the system performances such as imaging quality parameters, straylight, ghost, polarization sensitivity, and environmental influences; verify the adequacy of critical tests such as spectral characterization and straylight; and define and optimize instrument alignment procedures. Following a brief overview of the FLEX mission, we will cover the design and the development of the optics breadboard with emphasis on the results obtained during the tests and the lessons learned for the flight unit.

Anomalous and near-zero group-velocity dispersion in the sub-THz and mm-band atmospheric windows.

Analysis of the complex refractive index of atmospheric air reveals remarkably broad and continuous regions of anomalous and near-zero group-velocity dispersion in the subterahertz (sub-THz) and millimeter-band atmospheric windows. One such broadband dispersion anomaly is shown to occur in the high-frequency wing of the 60-GHz band of molecular oxygen. Adjacent to this dispersion anomaly is a broadband atmospheric transparency region within which the group-velocity dispersion is unusually weak, enabling distortion-free long-distance transmission of broadband millimeter-wave field waveforms, as well as broadband remote sensing in the millimeter band. Although broad regions of anomalous and near-zero dispersion also exist in the sub-THz range, their utility for long-distance transmission and remote sensing is limited because of strong atmospheric absorption.

A Simple Approximation for the Reflectance of a Thick Cloud in Gaseous Absorption Band and Its Application for the Cloud-Top Height Determination

This paper presents a new, simple, fast method to retrieve cloud altitude from measurements of light absorption in the strongest molecular band of oxygen (the A-band), centered at 761 nm, by the polarization and directionality of the earth’s reflectance sensor. First, we assess the validity of the method against synthetic spectra as a function of realistic cloud scenarios and satellite observation geometries. The retrieval error estimate amounts, on average, to less than 500 m. Second, the hurricane Ileana, overpassed the August 30, 2012, off the coasts west of Mexico and Southern California, is selected as test bed for the comparison of our retrievals against independent and nearly coincident cloud data inferred with the Moderate Resolution Imaging Spectroradiometer onboard Aqua and the Global Ozone Monitoring Experiment 2 onboard MetOp-A. We find that our approach can accurately reproduce the cloud height patterns, as long as the clouds are not thin cirrus.

Vis-NIR responsive Bi24O31Br10 and corresponding composite with up-conversion phosphor towards efficient photocatalytic oxidation

Abstract In this work, series of Bi24O31Br10 semiconductors were respectively synthesized by precipitation, solvothermal and calcination methods to explore the influence of preparation methods on the photocatalytic performances of photocatalysts. The refractory antibiotics (CIP and TC) and low concentration of continuous flowing NO gas were used as photocatalytic targets with the irradiation of visible or NIR lights. Interestingly, Bi24O31Br10 fabricated by a simple room-temperature precipitation method (BOB-R) exhibited the best photocatalytic activity compared to the other two samples with high cost preparation. The characterizations and trapping experiments verified that the smaller nanoparticles, oxygen vacancy concentration, band structure and charge combination probability were contributed to the superior photocatalytic performance of Bi24O31Br10 prepared by precipitation method. Besides, due to the generation of oxygen vacancies, BOB-R sample not only showed excellent removal efficiency of NO by UV and short-wavelength visible light, but also had considerable photocatalytic activity induced by long-wavelength visible light (λ > 510 nm). To further broaden the range of light response to near-infrared light, the up-conversion phosphors were used to couple with BOB-R sample at room temperature. The up-conversion phosphors/BOB-R composites exhibited good UV light, short-wavelength and long-wavelength visible lights caused photocatalytic removal of NO, meanwhile valuable NIR light driven performance was found.

LaNixFe1-xO3 (0 ≤ x ≤1) as photothermal catalysts for hydrocarbon fuels production from CO2 and H2O

LaNixFe1-xO3 perovskite compounds (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) were successfully synthesized by a sol-gel combustion method. The crystal structure, morphology, BET surface area, oxygen vacancies, band gap and catalytic properties of the catalyst were characterized in detail. The results showed that LaNi0.4Fe0.6O3 compound exhibits the best photothermal catalytic performance. Under the same catalytic conditions (350 ℃ + Vis-light), CH4 and CH3OH yields are about 3.5 and 4.0 times, 1.8 and 2.1 times of that of LaFeO3 and LaNiO3. It was found that all the solid solutions possesses better catalytic properties than the pure end compounds. The doping of Ni lead to a significant modification with the quantity of oxygen vacancies and band gaps. These findings may further broaden the materials scope for photothermal conversion of CO2 and H2O.

Highly sensitive and selective isoprene sensing performance of ZnO quantum dots for a breath analyzer

We report the quantum-size effect on the sensing properties of ZnO nanoparticles for the detection of isoprene. For this purpose, two types of ZnO particles with different sizes, including nanoparticles (NPs, ˜25 nm) and quantum dots (QDs, ˜5 nm), were prepared by a wet chemical method. The ZnO QDs exhibited excellent sensing performance to 1 ppm isoprene compared to NPs. The maximum sensing response and response time were ˜42 and 8 s at 350 °C for the QDs, while ˜5.6 and 40 s at 500 °C for the NPs, respectively. The higher sensing response, rapid response, and lower optimal working temperature of the ZnO QDs can be attributed to an increase in oxygen vacancies, band gap, and specific surface area owing to the small size effect. Both ZnO NPs and QDs showed the lower limit of 0.01 ppm for detecting isoprene. It is noted that the sensing properties of ZnO QDs to 1 ppm isoprene are superior to previously reported isoprene sensors that are based on semiconducting metal oxides. Furthermore, we demonstrated that the low concentration (0.4–6.2 ppm) of isoprene can be selectively detected within ˜83 s using a recently developed miniaturized gas chromatography integrated with the ZnO QD sensor.

Collision-induced absorption between O2-CO2 for the a1Δg (v = 1) ← X3Σ (v = 0) transition of molecular oxygen at 1060 nm.

Collision-induced absorption between O2 and CO2 molecules associated with the a1Δg (v = 1) ← X3Σ-g (v = 0) band of oxygen around 1060 nm was measured using cavity ring-down spectroscopy. The lineshape for this transition is measured for the first time, and the integrated cross-section is found to be smaller than the only previous report. For pure oxygen, we find an integrated absorption value of (2.10 ± 0.31) × 10-4 cm-2 amg-2 which is in good agreement with the previous reported values. For O2-CO2 collisions we report an integrated value of (6.37 ± 1.09) × 10-5 cm-2 amg-2 which is small but still significant and not accounted for by theory.

Photocatalytic and Antibacterial Applications of Magnetic Fe3O4–CuO Nanocomposite

Fe3O4–CuO nanocomposite was prepared by hydrothermal method, which is simple and cost effective. The prepared nanocomposite was characterized for XRD that confirms the presence of crystalline peaks corresponding to both Fe3O4 and CuO. The morphology and phase composition were characterized by High resolution scanning electron microscope (HRSEM) and Energy dispersive X-ray analysis (EDAX). The Fourier transforms infrared (FTIR) spectra reveals information about metal oxygen bands in the composite. UV-visible spectroscopy was used to study their optical properties. The photocatalytic degradation of organic dye crystal violet using the composite as catalyst under visible light illumination was studied. The antibacterial activity of the sample was also examined.

Description of an air temperature sensor based on O2 absorption spectroscopy.

In this paper, we describe in detail an assembled open-path optical cavity to act as a temperature sensor of air. A metal absorption cell in a temperature-regulated tube furnace is placed at the center of an optical cavity. The optical cavity consists of two mirrors, two nitrogen buffer sleeves, and the open cell. The air is injected through a fitting in one extreme of the metal tube and travels half the tube length through a channel in the wall of the tube. The channel directs the air towards the center of the cell. The air flowing is heated at the temperature of the metal tube in contact with the furnace. The heated air injected at the center of the tube, flows towards the open extremes of the tube. The nitrogen buffer sleeves protect the mirrors from the heated air. The temperature of the air flowing through the tube is determined by measuring the absorption of the A band of oxygen as a function of the wavenumber in the 769-755 nm wavelength range. The absorption technique is phase-shift cavity ring down spectroscopy. To obtain the temperature, the energy of the lower rotational state for eleven selected rotational transitions is linearly fitted to a logarithmic function that contains the relative intensity of the rotational transition, the initial and final rotational quantum numbers and the energy of the transition. Accuracy of the measurement is determined by comparing the calculated temperature from the spectra with the analog reading of the temperature-regulated tube furnace. This technique is proposed for exhaust air temperature measurements of combustion chambers and cooling air after passing through the blades of a turbine.

Inhibition behavior of Tragia involucrata L. phenolic compounds against acidic medium corrosion in low carbon steel surface

Abstract The antioxidant and anticorrosive effect of Tragia involucrate L. (T. involucrate L.) was evaluated to aid in finding new compounds which can be used for various purposes. The total phenolic (TPC) and flavonoid content (TFC), antioxidant activity (DPPH, reducing potential and phosphomolybdenum), and electrochemical measurements, Fourier transform infrared (FT-IR), UV–visible (UV–vis) spectral analysis, scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM–EDX) and atomic force microscopy (AFM) were done to analyze the potency and also the inhibition efficiency of T. involucrate L. against 1 mol·L−1 HCl on low carbon steel. The TPC (145.21 mg GAE·g−1), TFC (52.32 mg QCE·g−1) and antioxidant activities were found to be significant. The electrochemical studies performed by AC impedance measurements showed significant changes in impedance spectra without causing any change in Nyquist plots. An increase in charge transfer resistance (Rct) values, a blockage in active sites exhibiting cathodic and anodic inhibition shows the action of inhibitor on low carbon steel. This was later confirmed by FT-IR and UV–vis which showed variation in absorption band at 270 nm and 273 nm (before immersion) and 208 and 281 nm (after immersion). The same was tested again by SEM–EDX through altered strength of iron and oxygen bands and using AFM by analyzing the change in average roughness values of low carbon steel before (61.65 nm) and after (97.87 nm) exposure to blank acid without inhibitor, while it was shifted to 81.58 nm in acid with inhibitor. All these results showed strong evidence adding values to T. involucrate L. plant extract in inhibiting corrosion on low carbon steel and by promoting antioxidant importance of the extract which helps in scavenging free radicals.

Application of Single-Pulse Charge Pumping Method on Evaluation of Indium Gallium Zinc Oxide Thin-Film Transistors

A novel single-pulse charge pumping (SPCP) method was proposed and implemented to profile the density of states (DOSs) in metal–oxide–semiconductor thin-film transistors (TFTs). The proposed SPCP method was demonstrated in characterizing the DOS below the conduction band of indium gallium zinc oxide TFTs. The DOSs, including oxygen vacancy donorlike states and band tail states, were characterized successfully with high resolution. This method has all the advantages of the conventional CP method and single-pulse characterization.

Oxygen electronic screening and hybridization determining the insulator-metal transition of Eu1−xBaxTiO3

An insulator-metal transition (IMT) is a fascinating yet hotly debated phenomenon in condensed-matter physics. Here we report on the evolution of electronic structure across IMT as in $\mathrm{E}{\mathrm{u}}_{1\ensuremath{-}x}\mathrm{B}{\mathrm{a}}_{x}\mathrm{Ti}{\mathrm{O}}_{3}$ as a function of $x$ ($x=0$ for ETO and $x=0.5$ for EBTO) and temperature comprehensively using high-resolution spectroscopic ellipsometry, soft x-ray absorption spectroscopy at Ti $L$ and O $K$ edges, and transport measurements. We observe different types of spectral weight transfers (SWTs), which are responsible for tuning optical band gaps, accompanied by dramatic changes in electrical conductivity. At room temperature, when $x$ increases, SWT occurs due to the high energy of O $2p$ to low-energy bands. Such a SWT increases Eu-O-Ti hybridization and enhances Drude response, which increases electrical conductivity in EBTO. Interestingly, upon cooling, SWT arises from low-energy to high-energy bands and opens up a gap of a low-energy oxygen band, which then suppresses electrical conductivity in EBTO. We argue that the unscreened electron-electron interaction in oxygen yields a metal-to-charge-transfer insulator-like transition. Our result reveals comprehensively the importance of oxygen screening effects and hybridizations in the IMT, and it provides insight into $\mathrm{E}{\mathrm{u}}_{1\ensuremath{-}x}\mathrm{B}{\mathrm{a}}_{x}\mathrm{Ti}{\mathrm{O}}_{3}$.

Luminescence of ND radicals during the destruction of molecular nitrogen nanoclusters

In this work we studied optical spectra of thermoluminescence accompanying the destruction of collections of molecular nitrogen nanoclusters containing stabilized nitrogen, oxygen, and deuterium atoms. These collections of nanoclusters were formed by the injection of products of a radio-frequency discharge in deuterium-nitrogen-helium gas mixtures into bulk superfluid 4He. In the range from 200 to 1650 nm, the bands at 336 nm, 473 nm along with a new band at 1170 nm as well as the known bands of atomic nitrogen and oxygen, and bands of molecular nitrogen, oxygen, and NO were observed. These three bands were assigned to the emission of the ND radicals formed due to recombinations of nitrogen atoms in excited metastable states and deuterium atoms in the ground state during the destruction of ensembles of molecular nitrogen nanoclusters.

VOn Complexes in RTA Treated Czochralski Silicon Wafers Investigated by FTIR Spectroscopy

Rapid thermal annealing (RTA) in silicon wafer processing is a technique used to control point defects, vacancies and silicon interstitials (1,2). The presence of these defects influences the nucleation and precipitation of supersaturated oxygen in Czochralski (CZ) silicon wafers. The precipitation of oxygen, which occurs during annealing of silicon wafers, is a very important phenomenon. This is because the oxygen precipitates provide a natural getter sink for unwanted metallic impurities which can get into the devices active region in the fabrication process. Vacancies are of high importance because they enhance oxygen precipitation. In CZ silicon vacancies are mainly bound with oxygen atoms forming so called VOn complexes where n is the number of oxygen atoms. The investigation of VOn complexes in silicon wafers is extremely difficult because of their low concentration, which is in the range of 1013 cm-3. So far, irradiation experiments are the main source of information about VOn complexes. The irradiation allows increasing their concentration to a much higher level compared to the level, which can be found in processed wafers. Akhmetov et al. (3) published the first detection of VOn complexes in non-irradiated but RTA pre-treated wafers. In order to be able to measure defects with very low concentration they used highly sensitive FTIR measurements at room temperature (RT). They found the absorption band at 985 cm-1 which they attributed to VO4. The estimated concentration of VO4 complexes was very close to calculated values from an ab initio model (4). In this work, we used a slightly modified method in order to investigate VOn complexes in RTA pre-treated wafers. The measurements were carried out at 6 K what allowed us to enhance the sensitivity. Moreover, the FWHM of the interstitial oxygen band is much smaller at 6 K compared to RT. This means that the range of wave numbers next to the Oi band typically covered by this band at RT can be investigated now. This range is very important because some absorption bands of VOn complexes with n > 4 are located there. In a previous study, in a wafer pre-treated by RTA at 1250 °C for 30 s in an Ar containing O2 atmosphere we found the absorption bands of VO4 at 985 cm-1 and 991 cm-1 in the measurements carried out at room temperature and at 6 K, respectively (5). In this wafer, we also detected an unknown band at 1030 cm-1 and the bands at 1096 cm-1 and 1099 cm-1, according to Murin et al. both assigned to VO5,6 (6). In order to better understand these complexes we performed additional experiments. The wafers were pre-treated by RTA in the range between 1250 °C and 1375 °C and the behavior of the detected bands was analyzed and correlated with simulations. The process of vacancy-oxygen complex formation after RTA was simulated using a rate equation model. It was found out that the most stable VOn complexes are the ones with n = 6, 5 and 4. In summary, the VOn complexes were investigated by FTIR spectroscopy at 6K in RTA pre-treated wafers. The process of vacancy-oxygen complex formation after RTA was modeled using a rate equation model. References R. Falster, M, Pagani, D. Gambaro, M. Cornara, M. Olmo, G. Ferrero, P. Pichler, M. Jacob, Solid State Phenom., 57-58, 129 (1997). M. Pagani, R. Falster, G. R. Fisher, G. C. Ferrero, M. Olmo, Appl. Phys. Lett., 70 (12), 1572 (1997).V. Akhmetov, G. Kissinger, and W. von Ammon, Appl. Phys. Lett., 94, 092105 (2009).G. Kissinger, J. Dabrowski, A. Sattler, C. Seuring, T. Müller, H. Richter, W. von Ammon, J. Electrochem. Soc., 154, H454 (2007).D. Kot, G. Kissinger, and A. Sattler, Semicond. Sci. Technol. 32, 104006 (2017).L.I. Murin, J. L. Lindström, B. G. Svensson, V. P. Markevich, A. R. Peaker, C. A. Londos, Solid State Phenomena, Vols. 108-109, pp. 267-272 (2005).

Exploration of the potential for using Spark-I observations to derive atmospheric parameters

ABSTRACTAs part of a low-cost nanosatellite constellation, Spark-I, a hyperspectral resolution instrument with 149 channels covering blue to near-infrared, has been successfully launched on 22 December 2016. In this study, we try to explore its potential to derive atmospheric parameters according to optimal estimation theory. From simulated measurements, we estimated the information content described as degrees of freedom for signal (DFS) and error reduction of typical aerosols, including dust, soot, sea salt, and sulphate, as well as water vapour (H2O), nitrogen dioxide (NO2), surface pressure, and Sun-induced fluorescence (SIF). Based on the results, only the H2O column, aerosol optical depth (AOD), and surface albedo could be derived with error reduction of 20%, 40%, and near 100%, respectively. The retrieval of aerosol was strongly correlated with surface albedo, especially dust, with a DFS of 0.3–0.9 due to surface variations. After investigating the impact of the oxygen and H2O absorption bands on the aerosol information content, we recommend retrieving aerosol characteristics using full channels, rather than sub-band channels. The more fraction one type of aerosol is, the larger information about it we can get. Different AOD results in 0.3–0.8 aerosol DFS change and solar zenith angle influences less. The information of atmospheric gases was sensitive to both signal-to-noise ratio (SNR) and spectral resolution due to their particular absorption patterns. However, improving only the SNR by double or more could allow for the derivation of SIF emissions, assuming the a priori estimation is accurate.