Oxygen Molecules O2 Research Articles

A Study on Dielectric Breakdown Properties of Hot CO2/O2/C5F10O Gas Mixture: Focus on Concentration Rate of O2 Gas

A gaseous mixture of CO2 and C5F10O has been widely investigated as one of the alternative gases for SF6. Due to the better electron attachment ability of oxygen molecule O2, it is generally expected that adding of O2 gas would improve the dielectric strength of arc quenching and insulating gas for electric power equipment. Therefore, in this paper, the dielectric breakdown properties of hot CO2/O2/C5F10O gas mixture were numerically estimated. The calculation results revealed that the critical electric field strength of the CO2/C5F10O gas mixture is disappointingly decreased by the addition of O2 gas, especially in the temperature range of 3000 K to 1000 K. This is brought about by the increase of ionization reaction of CO2 molecules with an increase in the O2 concentration in the arc‐quenching gas of CO2/O2/C5F10O. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Diatomic molecular energy spectra and thermodynamic properties of exponential inversely quadratic plus improved deformed exponential-type potential

By employing the Pekeris-type approximation to deal with the centrifugal term, we study the thermodynamic properties and approximate analytical solutions of the Schrödinger equation with the exponential inversely quadratic plus improved deformed exponential-type potential using parametric Nikiforov–Uvarov method and hypergeometric functional analysis method. The complex eigen energy equation was presented in a closed and compact form and extended to study partition function and other thermodynamic properties. The total normalized wave functions were also obtained and expressed in terms of hypergeometric Jacobi polynomial. The mathematical accuracy of analytical calculation can be verified consistently by comparing numerical data and results of different arbitrarily l state. The potential also reduces to improved deformed exponential-type potential as a special case. We calculated energy spectra for some selected diatomic molecules namely: Silicon Flouride (SiF+ (X1∑+), Oxygen molecule O2+ (X2∏g), Nitrogen molecule, N2+ (X1∑g+), Sulphur chloride SCl and Rubidium hydride RbH using standard molecular spectroscopic constants as applied to the two methods. The results show that the energy eigenvalues for these selected diatomic molecules are in excellent agreement using the two methods and also increases with an increase in quantum state.

Ozone destruction due to the recombination of oxygen atoms.

Kinetics of ozone destruction due to the recombination of oxygen atoms produced by pulsed 266nm laser photolysis of O3/M (M = CO2 and/or N2) mixtures was studied using the absorption and emission spectroscopy to follow time evolutions of O3 and electronically excited molecules O2* formed in the recombination process 2O(3P) + M → O2* + M. An unexpected high ozone destruction rate was observed when O2* was present in the system. The kinetic model developed for the oxygen nightglow on the terrestrial planets was adapted to interpret the detected temporal profiles of the ozone number density and the O2* emission intensities. It was deduced that the vibrationally excited singlet delta oxygen molecule O2(a1Δ, υ) formed in the secondary processes reacts efficiently with ozone in the process O2(a1Δ, υ ≥ 3) + O3 → 2O2 + O, and the rate constant of this process was estimated to be 3 × 10-11cm3s-1. Ab initio calculations at the CASPT2(14, 12)/cc-pVTZ/UωB97XD/cc-pVTZ level of theory were applied to find the reaction pathway from the reactants to products on the O5 potential energy surface. These calculations revealed that the O2(a1Δ) + O3 reaction is likely to proceed via singlet-triplet intersystem crossing exhibiting an energy barrier of 9.6 kcal/mol, which lies between two and three quanta of vibrational excitation of O2(a1Δ), and hence, O2(a1Δ, υ) with υ ≥ 3 could rapidly react with ozone.

Monitoring adaptation of skin tissue oxygenation during cycling ergometer exercise by frequency-domain diffuse optical spectroscopy.

In addition to supplying oxygen molecule O2 for metabolic functions during the adaptation to exercise, blood also plays a critical role in heat dissipation for core temperature stabilization. This study investigates the status of hemodynamic oxygenation in the forearm's skin tissue of three participants during a complete ergometer exercise from the resting to exercising, and to recovering conditions using a three-wavelength frequency-domain diffuse reflectance spectroscopy (FD DRS) alongside the monitoring of heartbeat rate and skin temperature. The FD DRS system was synchronized with radiofrequency (RF)-modulated input photon sources and the respective output to extract time-course absorption and scattering coefficients of the skin tissue, which, through the fitting of lambert's law of absorbance, can be used to determine the concentration of oxygenated/deoxygenated hemoglobin molecules, and consequentially, the oxygen saturation of skin tissue and total hemoglobin (THb) concentration. Expressly, a sudden jump in heartbeat rate at the beginning of the exercise, a temporal lag of the rising edge of skin temperature behind that of the THb concentration in the procession of step-wise incremental working intensity, and the uprising of THb in the exhaustion zone in responses to the physiological adaptation to exercise were identified. Finally, conclusive remarks were drawn that the FD DRS system is useful in extracting the hemodynamic properties of forearm skin which is often being neglected in previous exercise physiology studies by DRS-related techniques. The detailed variation of hemodynamic and optical scattering parameters of forearm skin elucidated in the studies can be applied for the analysis of athletes' physiological status, and may be a potential reference for the design of future wearable devices.

Molecular oxygen dissociation on tin carbide monolayers with gold adatoms

In this work, the interactions between oxygen molecule O2 with pristine and gold-decorated tin carbide (SnC) monolayers were investigated by using density functional calculations. The results indicate that O2 is adsorbed, with an energy of 0.95 eV, on the pristine SnC nanosheet in a bond-like configuration with each oxygen close to a carbon and a tin atom, respectively. There is a large electronic charge transfer from the SnC monolayer to the O2 molecule, which enlarges the molecule internal bond, indicating an activation towards a peroxo-like state. Also, a gold adatom can strongly bind to the SnC monolayer over a C atom. Furthermore, when O2 interacts with this Au adatom, it is spontaneously dissociated with an energy gain of 1.84 eV and where the final adsorption configuration consists of each oxygen on the top of different tin atoms but sharing the gold one.

New techniques for retrieving the [O(3P)], [O3] and [CO2] altitude profiles from dayglow oxygen emissions: Uncertainty analysis by the Monte Carlo method

This study presents methods for retrieving the altitude profiles of atomic oxygen, [O(3P)], ozone, [O3], and carbon dioxide, [CO2], concentrations in the daytime mesosphere and lower thermosphere (MLT) in the framework of the YM2011 model of the electronic-vibrational oxygen kinetics. The emissions of singlet oxygen molecules O2(b1Σ+g, v ≤ 2), O2(a1Δg, v = 0) and the O(1D) atom are used as proxy of the [O(3P)], [O3] and [CO2]. For all the proposed techniques, we compare the uncertainty values of the retrieved [O(3P)], [O3] and [CO2], obtained by the Monte Carlo method, with estimations obtained by the sensitivity analysis method in the earlier works. For all the above mentioned methods for retrieving the [O(3P)], [O3] and [CO2] profiles, we obtained analytical expressions that include the concentrations of excited substances considered as proxies. In addition, the optimal altitude ranges for using these remote sensing methods were determined based on the results of numerical experiments by the Monte Carlo method.

Reduction Site in Ce n V m O k + Revealed by Gas Phase Thermal Desorption Spectrometry

Vanadia supported on ceria shows particularly high catalytic reactivity. To elucidate its reduction site, cationic cerium-vanadium oxide clusters, Ce n V m O x + (n = 1–6, m = 0–5), were generated in the gas phase and their thermal response, such as reduction by oxygen release, was investigated by gas phase thermal desorption spectrometry. Stoichiometric and near-stoichiometric Ce n V m O x + clusters were dominantly formed, suggesting that Ce and V atoms in thermally stable clusters at 310 K have the oxidation states of + 4 and + 5, respectively. An oxygen molecule O2 was found to desorb from the clusters, resulting in formation of Ce n V m O x−2 +, upon heating. Presence of more than two Ce atoms in the clusters for odd values of m, or more than three Ce atoms for even values of m lowered the desorption temperature, indicating that not V atoms (+ 5 to + 4) but Ce atoms (+ 4 to + 3) in Ce n V m O x + tend to be reduced.

A study of the oxygen dynamics in a reactive Ar/O2 high power impulse magnetron sputtering discharge using an ionization region model

The oxygen dynamics in a reactive Ar/O2 high power impulse magnetron sputtering discharge has been studied using a new reactive ionization region model. The aim has been to identify the dominating physical and chemical reactions in the plasma and on the surfaces of the reactor affecting the oxygen plasma chemistry. We explore the temporal evolution of the density of the ground state oxygen molecule O2(X1Σg−), the singlet metastable oxygen molecules O2(a1Δg) and O2(b1Σg), the oxygen atom in the ground state O(3P), the metastable oxygen atom O(1D), the positive ions O2+ and O+, and the negative ion O−. We furthermore investigate the reaction rates for the gain and loss of these species. The density of atomic oxygen increases significantly as we move from the metal mode to the transition mode, and finally into the compound (poisoned) mode. The main gain rate responsible for the increase is sputtering of atomic oxygen from the oxidized target. Both in the poisoned mode and in the transition mode, sputtering makes up more than 80% of the total gain rate for atomic oxygen. We also investigate the possibility of depositing stoichiometric TiO2 in the transition mode.

Enhancement of hydrogen sulfide oxidation via excitation of oxygen molecules to the singlet delta state

Comprehensive analysis of the effect of the presence of excited singlet oxygen molecules O2(a1Δg) on the enhancement of ignition and combustion in the H2S–air mixture is conducted on the basis of developed reaction mechanism. This mechanism incorporates the results of ab initio calculations of potential energy surfaces for the H2S+O2(X3Σg−) and H2S+O2(a1Δg) systems. The existing experimental data on the ignition delay and laminar flame speed in the H2S–air mixture are used for the validation of the constructed reaction mechanism. It has been demonstrated that the abundance of O2(a1Δg) molecules even in small amounts (only 1% in total oxygen) could substantially intensify the chain-branching in the H2S–air mixture. This allows one to reduce notably the ignition delay, especially at low initial temperatures (T0 = 600–800K), and to increase the flame speed. The major effect is observed for the fuel-lean and stoichiometric mixtures. So, at ϕ = 0.6, the presence of 5% O2(a1Δg) molecules in total oxygen increases the flame speed by 25%. Kinetic mechanisms, responsible for shortening the ignition delay and for the increase of flame speed, are discussed in a detailed manner.

Kinetic modeling and determination role of sono/photo nanocatalyst-generated radical species on degradation of hydroquinone in aqueous solution.

Experimental findings of sonophotocatalytic process were used in degradation of hydroquinone to assess kinetic modeling and determine the effect of various active radical species. First, the effects of three photocatalytic, sonocatalytic, and sonophotocatalytic processes were studied for hydroquinone removal to determine kinetic constants and calculate the activation energy of reactions, and then the selected process was evaluated to determine active radical species. The reactor was composed of two parts, one included ultrasonic probe (sonocatalytic part) with powers 22, 80, and 176W and the second part was the location of UV lamp (photocatalytic part) with tubular flow and power 15W. After three systems were examined and the efficient system was selected, the role of different active species such as hydroxyl radical (OH(·)), superoxide radical (O2 (·-)), hole (h(+)), electrons (e (-)), and single oxygen molecule ((1)O2) and contribution of each of them were determined in hydroquinone degradation. According to tests, the results of this study showed that sonophotocatalytic integrated method as selected system among three systems studied followed the first-order equation for hydroquinone degradation and active hydroxyl species with 45% and electron and hole with 15 and 10%, respectively, had the highest and lowest contributions to conversion of hydroquinone. The findings showed that dissolved oxygen increases the capability of active radical formation so that 28.2% of hydroquinone removal was increased under aeration compared to without aeration. Also, removal efficiency decreased 62% with N2 injection due to the withdrawal of oxygen from the sample. By adding 25Mm of sodium azide (NaN3) to stock solution, 46.5% reduction was developed because single oxygen ((1)O2) played the role of an active species. The advantages of integrated sonocatalytic and photocatalytic method are the generation of active radical species with more variety and ultimately the formation of higher amounts of powerful hydroxyl radical that increases degradation rates of refractory compounds and low-risk internal and final products. It has an appropriate performance in the degradation of refractory compounds by optimizing effective operational factors.

Luminescence of the (O2(a(1)Δ(g)))2 collisional complex in the temperature range of 90-315 K: Experiment and theory.

Experimental and theoretical studies of collision induced emission of singlet oxygen molecules O2(a(1)Δg) in the visible range have been performed. The rate constants, half-widths, and position of peaks for the emission bands of the (O2(a(1)Δg))2 collisional complex centered around 634 nm (2) and 703 nm (3) have been measured in the temperature range of 90-315 K using a flow-tube apparatus that utilized a gas-liquid chemical singlet oxygen generator. The absolute values of the spontaneous emission rate constants k2 and k3 are found to be similar, with the k3/k2 ratio monotonically decreasing from 1.1 at 300 K to 0.96 at 90 K. k2 slowly decreases with decreasing temperature but a sharp increase in its values is measured below 100 K. The experimental results were rationalized in terms of ab initio calculations of the ground and excited potential energy and transition dipole moment surfaces of singlet electronic states of the (O2)2 dimole, which were utilized to compute rate constants k2 and k3 within a statistical model. The best theoretical results reproduced experimental rate constants with the accuracy of under 40% and correctly described the observed temperature dependence. The main contribution to emission process (2), which does not involve vibrational excitation of O2 molecules at the ground electronic level, comes from the spin- and symmetry-allowed 1(1)Ag←(1)B3u transition in the rectangular H configuration of the dimole. Alternatively, emission process (3), in which one of the monomers becomes vibrationally excited in the ground electronic state, is found to be predominantly due to the vibronically allowed 1(1)Ag←2(1)Ag transition induced by the asymmetric O-O stretch vibration in the collisional complex. The strong vibronic coupling between nearly degenerate excited singlet states of the dimole makes the intensities of vibronically and symmetry-allowed transitions comparable and hence the rate constants k2 and k3 close to one another.

Physics and chemistry of the influence of excited molecules on combustion enhancement.

The paper addresses detailed analysis of kinetic processes in the H(2)-O(2), CO-O(2) and CH(4)-O(2)-reactive systems upon the presence of singlet oxygen molecules O(2)(a(1)Δg) and [Formula: see text] and the influence of the activation of oxygen molecules in electric discharge on the acceleration of ignition in the H(2)-O(2) and CH(4)-O(2) mixtures. The possibility of the intensification of CO oxidation due to excitation of O(2) and N(2) molecule vibrations and generation of singlet oxygen molecules is also considered. It is shown that the effect of accelerating the ignition strongly depends on the reduced electric field and, as a consequence, on the composition of discharge plasma as well as on the features of chain mechanism development in oxy-fuel systems. It is revealed that the most effective approach for the intensification of CO oxidation both in the moist air and in the products of hydrocarbon combustion in air is the generation of O(2)(a(1)Δg) molecules by electric discharge. Computations showed that the presence of 1% O(2)(a(1)Δg) in the total oxygen allowed one to convert CO to CO(2) even at the temperature T=850-900 K in the time of 10(-2) s. The excitation of O(2) and N(2) molecule vibrations is less effective for such a conversion.

Specific features of the kinetics of H2-O2-O2(a 1Δ g ) mixtures: I. formation and quenching of electronically and vibrationally excited (A′) molecules in H2-O2-O2(A 1Δ g ) mixtures at a temperature of 300 K

Available data on the kinetic processes in H2-O2-O2(a 1Δ g ) mixtures are analyzed theoretically, and the ranges in which the rate constants of these processes can vary are determined. The processes of energy transformation in an O2(a 1Δ g )-H2-H-HO2 system in the approximations of the fast and slow (in comparison with the vibrational relaxation time of the HO2 radical) quenching of the electronically excited state are considered. The experiments on the quenching of singlet delta oxygen (SDO) molecules O2(a 1Δ g ) excited in a microwave discharge at a temperature of 300 K and pressure of 6 Torr in a lean hydrogen-oxygen mixture are simulated (by a lean fuel mixture is meant a mixture in which the ratio of the fuel to the oxidizer mass fraction is less than the stoichiometric ratio, which is 2: 1 for a hydrogen-oxygen mixture). It is shown that, over the experimental observation times, the SDO quenching frequency depends on the concentration of molecular hydrogen, the residual odd oxygen fraction in the gas flow, and the ratio between the rate constants of kinetic processes involving HO2 and HO2* radicals. Simulations of the microwave discharge and the transport of excited oxygen along the drift tube make it possible to determine the residual odd oxygen concentration in the gas flow. Recommendations on the choice of the rate constants for the O2(a 1Δ g ) + HO2)A″, v3″ = 0) ↔ O2 + HO2*(A′, v3′ = 1), HO2*(A′v3′ ≤ 1) + O2(a 1Δ g ) → HO2*(A′,v3′ ≥ 6) + O2, and HO2*(A′,v3′ ≤ 1) + O2(a 1Δ g ) → H + O2 + O2 processes are given. It is shown that, in the case of slow quenching in a H2-O2-O2(a 1Δ g ) mixture at a low temperature, the intensity of hydrogen oxidation is enhanced due to the reaction + HO2*(A′,v3′ ≤ 1) + O2(1Δ) → H + O2 + O2.

Coupled cluster calculations in the (0,2) and (2,0) sectors of the Fock space for the lowest electronic states of the O2 molecule

The Fock space (FS) multireference coupled cluster (CC) method in the (0,2) and (2,0) sectors has been applied to study the ground and excited states of the oxygen molecule O2. The considered FS sectors – when used for the neutral molecule – yield double ionisation potential (DIP) or double electron affinity (DEA) values. Once they are applied to the doubly negative/doubly positive ions the results provide description of the neutral molecule. In the current case the FS(0,2)-CC variant was used to generate potential energy curves (PEC) for the ground X3Σ−g and two lowest excited states, a1Δg and b1Σ+g, of the O2 molecule. Due to a closed shell nature of the reference function, the PECs could be easily extended to the ca. 6 Å which is not very common for the system as complex as the oxygen molecule. A similar attempt has been made to use the FS(2,0)-CC scheme by doing calculations for the ion (isoelectronic with the N2 molecule). The energy values obtained for the equilibrium bond length could be considered as acceptable; however, the PECs are limited to the short range of interatomic distances.

Long-range interactions in the ozone molecule: Spectroscopic and dynamical points of view

Using the multipolar expansion of the electrostatic energy, we characterized the asymptotic interactions between an oxygen atom O((3)P) and an oxygen molecule O(2)((3)Σ(g)(-)), both in their electronic ground state. We calculated the interaction energy induced by the permanent electric quadrupoles of O and O(2) and the van der Waals energy. On one hand, we determined the 27 electronic potential energy surfaces including spin-orbit connected to the O((3)P) + O(2)((3)Σ(g)(-)) dissociation limit of the O-O(2) complex. On the other hand, we computed the potential energy curves characterizing the interaction between O((3)P) and a rotating O(2)((3)Σ(g)(-)) molecule in its lowest vibrational level. Such curves are found adiabatic to a good approximation, namely, they are only weakly coupled to each other. These results represent a first step for modeling the spectroscopy of ozone bound levels close to the dissociation limit, as well as the low energy collisions between O and O(2) thus complementing the knowledge relevant for the ozone formation mechanism.

On the influence of singlet oxygen molecules on the NOx formation in methane-air laminar flame

Effect of the presence of singlet oxygen molecules O2(a1Δg) on nitric oxide formation in the CH4-air laminar flame is analyzed with the use of extended kinetic model. The developed model is based on the methane oxidation mechanism developed previously for the case of the abundance of excited O2 molecules in the mixture and incorporates new ab initio studies of N+O2(a1Δg) and N2+O2(a1Δg) reaction channels. It was revealed that the reactivity of O2(a1Δg) molecule in the reaction with atomic nitrogen is significantly smaller than that of normal ground state oxygen. Numerical simulations show that, despite this fact, the abundance of singlet delta oxygen in the CH4-air mixture results in an increase in the concentration of nitric oxide in the combustion exhaust. The major relative rise of NO concentration is observed for the fuel-lean mixture and can mount to 30% at the presence of 5% O2(a1Δg) in molecular oxygen. This phenomenon is due to the appearance of additional amount of atomic oxygen in the flame via acceleration of chain-branching in the mixture by adding O2(a1Δg) molecules. It is shown that, due to extending the flammability thresholds via abundance of singlet delta oxygen in the CH4-air mixture, it is possible to reduce significantly the NO emission without diminishing the flame speed.

Laser control of the low-temperature e −+O 2 + reaction

The dissociative recombination theory of slow electrons with molecular ions in a strong monochromatic light field is developed. Classifications of all possible transitions and reaction mechanisms are presented. The potential energy curves of the oxygen molecule O2** dissociative states and partial cross sections are calculated.

Electroreduction of molecular oxygen on metal-ion exchanger nanocomposites

The dioxygen electroreduction reaction has been studied on nanosized metal (Cu0, Ag0)-ionexchange matrix (macroporous sulfonated cation-exchange resin KU-23, sulfonated cation-exchange membrane MK-40) electrode materials. An increase in the half-wave potential of oxygen electroreduction from ∼0.10 to 0.29 V on passing from the Na+-to the H+-form of the Me0-ion exchanger nanocomposite indicates the involvement of the H+-ion in the step of attachment of the first electron to the oxygen molecule O2. The reaction of oxygen on the copper-KU-23 nanocomposite is accompanied by the appearance of an additional wave in the polarization curve of oxygen electroreduction in a neutral medium, which is associated with stabilization of hydrogen peroxide, a reaction intermediate, on nanosized copper. In the region of limiting current potentials, the rate-determining step of the array of electrochemical, chemical, and external- and internal-diffusion processes occurring during the electroreduction of oxygen is the external diffusion of O2 molecules to the electrode surface.

Photolysis of O3 at Hartley, Chappuis, Huggins, and Wulf bands in the middle atmosphere: Vibrational kinetics of oxygen molecules O2(X3Σ g − , ν ≤ 35)

The advanced version of the full model of O2 and O3 photodissociation in the mesosphere and thermosphere (Yankovsky V.A., Manuilova R.O., Atmospheric and Oceanic optics, 2003, V. 16, No. 7, P. 582) was used for the calculation of vertical profiles of vibrationally excited O2(X, ν) molecular concentrations in the ground electronic state for ν = 1–35. Recent data on the rate constants for reactions O2(X, ν ≤ 30) + O(3P) → O2(X, ν′ < ν) + O(3P) and O2(X, ν) were included for the first time in this model. These reactions play a significant role not only in the quenching of O2(X, ν) molecules, but also in the population of underlying vibrational levels of O2 molecules. In addition to direct processes of the production of O2(X, ν ≤ 35), resulting from O3 photolysis, the processes of population of O2(X, ν ≤ 9) molecules through the energy transfer from O(1D), O2(b, ν ≤ 2), and O2(a, ν ≤ 5) were used in the model. The resulting quantum output (RQO) for O2(X, ν = 1) molecules in process of ozone photolysis in spectral bands of not only Hartley, but also Chappuis, Huggins, and Wulf were calculated in the interval of 200–900 nm. The accounting for new processes caused an increase of RQO by 5–9% in the mesosphere. Vertical profiles of RQO and the populations of O2(X, ν ≤ 35) at heights of 50–120 km, depending on SZA, in a range from 36.0 to 90.1° for a series of TIMED/SABER experiments in the latitude interval from 30.2 to 47.7° N are presented during the period of vernal equinox.

A calibration method for broad-bandwidth cavity enhanced absorption spectroscopy performed with supercontinuum radiation

An efficient calibration method has been developed for broad-bandwidth cavity enhanced absorption spectroscopy. The calibration is performed using phase shift cavity ring-down spectroscopy, which is conveniently implemented through use of an acousto-optic tunable filter (AOTF). The AOTF permits a narrowband portion of the SC spectrum to be scanned over the full high-reflectivity bandwidth of the cavity mirrors. After calibration the AOTF is switched off and broad-bandwidth CEAS can be performed with the same light source without any loss of alignment to the set-up. We demonstrate the merits of the method by probing transitions of oxygen molecules O2 and collisional pairs of oxygen molecules (O2)2 in the visible spectral range.