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1.
This study investigated the characteristics of an atmospheric pressure air-glow discharge with a liquid cathode. Distilled water was utilized as the cathode. The electric field strength, gas temperature as well as the emission intensity of some N2(C3Πu → B3Πg) and OH (A2Σ+ → X2Π) bands were measured at a discharge current ranging from 15 to 50 mA. Based upon the data obtained, the reduced electric field strength, E/N, and effective vibrational temperatures for N2(C3Πu, X1Σ g + ) and OH (A2Σ+) were examined. The electron energy distribution function (EEDF) and some electron parameters (average energy, electron density and rate coefficients) were obtained based on a numerical solution of the Boltzmann kinetic equation. The result showed that the EEDF was not in equilibrium and the effective vibrational temperatures for N2(C3Πu, X1Σ g + ) were essentially higher than the gas temperatures.  相似文献   

2.
Collision-induced photon emissions (CIE) were observed for keV CO2/He collisions from 190 to 1020 nm. The emissions were assigned to the Δν=0 band of the CO2 B 2Σu+ → X 2Πg electronic transition and the Δν = +3, +2, +1, 0, −1, −2, −3 vibrational transition progression in the CO2 A 2Πu → X 2Πg electronic transition. The other peaks arise from the emissions of excited O· fragment atoms and the target gas. The relative intensities of the CO2 and O· emissions are independent of the ion translational energy above 3 keV, supporting the curve-crossing mechanism for collisional excitation. Investigation of the relative intensities within the A 2Πu → X 2Πg emission of CO2 indicates that the vibrational distribution is well described by the Franck-Condon principle at high collision energy, a consequence of short collision time but not necessarily an indication of vertical transitions. Below 3 keV ion translational energy, vibrational excitation in the A 2Πu electronic state was observed. The observation is consistent with the explanation that the reaction occurs at small impact parameters, in which short-range, repulsive interactions between the projectile and the target result in direct translational-vibrational excitation.  相似文献   

3.
A quasi-classical trajectory (QCT) calculation with the fourth-order explicit symplectic algorithm for the N(4S) + O2(X3Σg) → NO(X2Π) + O(3P) reaction has been performed by employing the ground and first-excited potential energy surfaces (PESs). Since the translational temperature considered is up to 5000 K, the larger relative translational energy and the higher vibrational and rotational level of O2 molecule have been taken into account. The affect of the relative translational energy, the vibrational and rotational level of O2 molecule in the reaction cross-sections of the ground and first-excited PESs has been discussed in a extensive range. And we exhibit the dependence of microscopic rate constants on the vibrational and rotational level of O2 molecule at T = 4000 K. The thermal rate constants at the translational temperature betweem 300 and 5000 K have been evaluated and the corresponding Arrhenius curve has been fitted for reaction (1). It is found by comparison that the thermal rate constants determined in this work have a better agreement with the experimental data and provide a more valid theoretical reference.  相似文献   

4.
The N-loss predissociation mechanisms of the A 2Σ+ (2 2 A′) state of N2O+ to the first and second dissociation limits were studied in the C s symmetry. The potential energy curves (PECs) and minimum energy crossing points (MECPs) for the C s states of N2O+ were calculated at the CAS levels. On the basis of our CAS calculation results (CASPT2 energetic results and CASSCF spin orbit couplings), we suggest two processes for N-loss predissociation mechanisms of A 2Σ+ (2 2 A′) to the first and second limits. The first two steps in the two processes are the same: A 2Σ+ passes through the 2 2 A′/1 4 A″ MECP and then reaches the 1 4 A″ (1 4Σ) PEC. The 2 2 A′/1 4 A″ MECP has a bent geometry and is slightly higher in energy than the transition state along the 1 4 A″ PEC. Our mechanisms are different from the previously suggested mechanisms (via 1 4Π).  相似文献   

5.
Electrocatalytic oxygen reduction was studied on a RuxFeySez(CO)n cluster catalyst with Vulcan carbon powder dispersed into a Nafion film coated on a glassy carbon electrode. The synthesis of the electrocatalyst as a mixture of crystallites and amorphous nanoparticles was carried out by refluxing the transition metal carbonyl compounds in an organic solvent. Electrocatalysis by the cluster compound is discussed, based on the results of rotating disc electrode measurements in a 0.5 M H2SO4. A Tafel slope of −80.00±4.72 mV dec−1 and an exchange current density of 1.1±0.17×10−6 mA cm−2 was calculated from the mass transfer-corrected curve. It was found that the electrochemical reduction reaction follows the kinetics of a multielectronic (n=4e) charge transfer process producing water, i.e. O2+4H++4e→2H2O. Electronic Publication  相似文献   

6.
The vibrational, rotational, and centrifugal constants are calculated for the B 1Π u , C 1Π u , (1) 1Π g , and (2) electronic states of a 85Rb2 molecule. The calculations are based on the semi-empirical potential curves obtained in this work. The results from calculating the molecular constants are compared with experimental data. The Franck-Condon factors and R v′v″ centroids are calculated for the electronic transitions B 1Π u -X 1Σ g +, C 1Π u -X 1Σ g +, C 1Π u -(1) 1Π g , and C 1Π u -(2) 1Σ g +.  相似文献   

7.
Homogeneous manganocolumbite (MnNb2O6) was synthesized from Nb2O5 and MnO oxides. Powder sample was orthorhombic with unit cell parameters: α = 0.5766 nm, b = 1.4439 nm, c = 0.5085 nm and V = 0.4234 nm3. Heat capacity over the temperature range of 313–1253 K was measured in an inert atmosphere with combined thermogravimetry and calorimetry using NETZSCH STA 449C Jupiter thermoanalyzer. Melting point was 1767 ± 3 K, enthalpy of melting was 144 ± 4 kJ mol−1. Experimental heat capacity of MnNb2O6 is fitted to polynomial C pm = 221.46 + 3.03 · 10−3 T + −39.79 · 105 T −2 + 40.59 · 10−6 T 2.  相似文献   

8.
Plasma produced by a (1064 nm) Nd:YAG laser focused onto a graphite target at different nitrogen pressures in the range of 1–90 mTorr, was studied spectroscopically. In the spectral range of 350–600 nm, emission lines of CI neutral carbon (501.12, and 505.21 nm), NI neutral nitrogen (493.5 nm), CII (426.72, 463.7, 515.11 nm), and CIII ions (465.02 and 569.59 nm), and NII ions (501.06, and 500.73 nm), were dominating. Bands of C2 Swan (d3Πg → a3Πu, Δ ν=2, 1, 0, −1), and CN Violet (B2Σ +→ X2Σ+, Δ ν=1, 0, −1) systems, and ionic emissions from the First Negative system N2+ (band head at 391.44 nm), were faintly observed under our specific experimental conditions. From the band intensities, vibrational temperature for CN and C2 was calculated to be 1.25 and 0.31 eV at 90 mTorr, respectively. The electron density and temperature, measured by Stark broadening, assuming a local thermodynamic equilibrium (LTE), were found to be 2.1× 1017 cm−3 and 0.33 eV at 1mTorr, respectively. The validity of the LTE is discussed according to the results discussed. Pressure dependence shows a decrease in the vibrational temperature when nitrogen pressure increases, while the electron density and temperature increase.  相似文献   

9.
Nano-composites of SnO(V2O3) x (x = 0, 0.25, and 0.5) and SnO(VO)0.5 are prepared from SnO and V2O3/VO by high-energy ball milling (HEB) and are characterized by X-ray diffraction (XRD), scanning electron microscopy, and high-resolution transmission electron microscopy techniques. Interestingly, SnO and SnO(VO)0.5 are unstable to HEB and disproportionate to Sn and SnO2, whereas HEB of SnO(V2O3) x gives rise to SnO2.VO x . Galvanostatic cycling of the phases is carried out at 60 mA g−1 (0.12 C) in the voltage range 0.005–0.8 V vs. Li. The nano-SnO(V2O3)0.5 showed a first-charge capacity of 435 (±5) mAh g−1 which stabilized to 380 (±5) mAh g−1 with no noticeable fading in the range of 10–60 cycles. Under similar cycling conditions, nano-SnO (x = 0), nano-SnO(V2O3)0.25, and nano-SnO(VO)0.5 showed initial reversible capacities between 630 and 390 (±5) mAh g−1. Between 10 and 50 cycles, nano-SnO showed a capacity fade as high as 59%, whereas the above two VO x -containing composites showed capacity fade ranging from 10% to 28%. In all the nano-composites, the average discharge potential is 0.2–0.3 V and average charge potential is 0.5–0.6 V vs. Li, and the coulombic efficiency is 96–98% after 10 cycles. The observed galvanostatic cycling, cyclic voltammetry, and ex situ XRD data are interpreted in terms of the alloying–de-alloying reaction of Sn in the nano-composite “Sn-VO x -Li2O” with VO x acting as an electronically conducting matrix.  相似文献   

10.
The mechanism of the spin-forbidden reaction Ti+(4F, 3d24s1) + C2H4→TiC2H2 + (2A2) + H2 on both doublet and quartet potential energy surfaces has been investigated at the B3LYP level of theory. Crossing points between the potential energy surfaces and the possible spin inversion process are discussed by means of spin-orbit coupling (SOC) calculations. The strength of the SOC between the low-lying quartet state and the doublet state is 59.3 cm−1 in the intermediate complex IM1-4B2. Thus, the changes of its spin multiplicity may occur from the quartet to the doublet surface to form IM1-2A1, leading to a sig-nificant decrease in the barrier height on the quartet PES. After the insertion intermediate IM2, two distinct reaction paths on the doublet PES have been found, i.e., a stepwise path and a concerted path. The latter is found to be the lowest energy path on the doublet PES to exothermic TiC2H2 +(2A2) + H2 products, with the active barrier of 4.52 kcal/mol. In other words, this reaction proceeds in the following way: Ti++C2H44IC→IM1-4B24,2ISC→IM1-2A1→[2TSins]→IM2→[2TSMCTS]→IM5→TiC2H2 +(2A2)+H2. Supported by ‘Qinglan’ Talent Engineering Funds by Tianshui Normal University.  相似文献   

11.
The A1, O, AlO, A12O, Al2O2, WO2, and WO3, partial pressures in the vapor over Al2O3 in a tungsten Knudsen effusion cell between 2300 and 2600 K were derived from A1+, O+, AlO+, A12O+, Al2O2+, WO2+, and WO3+, ion intensities. The mass spectrometer was calibrated against the equilibrium constant of the WO3(g) = WO2(g) + O(g) reaction. Refined values of the ionization cross sections of AlO and A12O2 were used in the partial pressure calculations. The enthalpies of atomization of aluminum suboxides were determined to be Δat H o(AlO, g, 0) = 510.7 ± 3.3 kJ mol−1, Δat H o(Al2O, g, 0) = 1067.2 ± 6.9 kJ mol−1, and Δat H o(Al2O2, g, 0) = 1556.7 ± 9.9 kJ mol−1.  相似文献   

12.
The molar heat capacities of the room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluoroborate (BMIPF6) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity on temperature is given as a function of the reduced temperature (X) by polynomial equations, C P,m (J K−1 mol−1) = 204.75 + 81.421X − 23.828 X 2 + 12.044X 3 + 2.5442X 4 [X = (T − 132.5)/52.5] for the solid phase (80–185 K), C P,m (J K−1 mol−1) = 368.99 + 2.4199X + 1.0027X 2 + 0.43395X 3 [X = (T − 230)/35] for the glass state (195 − 265 K), and C P,m (J K−1 mol−1) = 415.01 + 21.992X − 0.24656X 2 + 0.57770X 3 [X = (T − 337.5)/52.5] for the liquid phase (285–390 K), respectively. According to the polynomial equations and thermodynamic relationship, the values of thermodynamic function of the BMIPF6 relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass transition of BMIPF6 was measured to be 190.41 K, the enthalpy and entropy of the glass transition were determined to be ΔH g = 2.853 kJ mol−1 and ΔS g = 14.98 J K−1 mol−1, respectively. The results showed that the milting point of the BMIPF6 is 281.83 K, the enthalpy and entropy of phase transition were calculated to be ΔH m = 20.67 kJ mol−1 and ΔS m = 73.34 J K−1 mol−1.  相似文献   

13.
Yttrium-doped lithium manganese oxide (LiMn0.98Y0.02O2) was prepared by ion exchange of lithium for sodium in NaMn0.98Y0.02O2 precursors obtained by using rheological phase reaction method. This material had small particle size, which was composed of grain size of about 100 nm. Especially, LiMn0.98Y0.02O2 delivered the initial discharge capacity of about 191 mA h g−1 at room temperature when cycled between 2.0 and 4.4 V vs Li/Li+. Moreover, it showed an excellent cycling behavior, its specific capacity remained above 173 mA h g−1 after 20 cycles, and the material did not transform into spinel structure during the electrochemical cycling according to the cyclic voltammograms and X-ray powder diffraction. The electrochemical results revealed that the doping of Y3+ improved the performance of LiMnO2 considerably.  相似文献   

14.
A DFT/B3LYP method using the 6-311++G(3df) basis set is employed to calculate the geometric, electronic, and thermodynamic parameters of O=NO-ON=O peroxide as an isomer of N2O4 dinitrogen tetraoxide. Calculations of the configuration interaction in a system of three paramagnetic particles with open shells have shown for the first time that the formation of cis-cis peroxide in the oxidation reaction of nitrogen oxide 2NO (2Π) + O2 (3Σg) → O=NO-ON=O (1 A) proceeds without an energy barrier in accordance with recently performed studies. The molecular orbital scheme of the barrierless activation of molecular oxygen and the driving force of the NO oxidation reaction are considered. A spontaneous character of the process is based on the idea of spin-catalysis when the reaction proceeds in the two-triplet state with total zero spin. The obtained results are in agreement with the experimental data on a spontaneous and irreversible process characterized by the observed negative activation energy.  相似文献   

15.
Complete active space self-consistent-field (CASSCF) and multiconfigurational second-order perturbation theory (CASPT2) calculations in conjunction with the ANO-L basis set were performed to investigate systematically the low-lying electronic states of HNCS and its ions in C s symmetry. Our highly accurate calculation indicated that theoretically determined geometric parameters and harmonic vibrational frequencies for the ground-state X 1A′ are in good agreement with observed experimental data. The geometry of triplet HNCS is clearly favored C 1 symmetry, and the relative energy is predicted to be 3.000 eV (69.2 kcal/mol). The vertical transition energies for the selected excited states of HNCS were calculated at CASSCF/CASPT2/ANO-L level of theory based on CASSCF optimized geometry. Except for a few linear states of X 2Π (12A′, 12A″), 14Σ (14A″), and 12Σ+ (32A′) states of HNCS+, our results confirmed that the majority of excited states are twisted trans-bend structures. The existence of bound excited anion states has been found for the first time in HNCS. A more elaborate examination of ionization potential of HNCS (AIP, VIP) than previous reports has been presented.  相似文献   

16.
The spin-orbit and the spin-spin coupling constants of the 4Πg state of the He2 ion, of the parent a3Σu +, and of the b3Πg states of He2 have been evaluated by a multireference configuration interaction method. The theoretical spin-spin splittings of the a3Σu + state and the R-dependent spin-spin function are found to be in excellent agreement with experiment, with deviations in the range of a few MHz. The theoretical spin-orbit constants and splittings of the b3Πg state are larger than the experimental values by about 370 MHz. The spin-orbit coupling constant of the 4Πg state of He2 is␣estimated to be three times smaller than in the b3Πg state, but one of the intramultiplet off-diagonal spin-spin interactions is predicted to give a large contribution to the fine structure of the metastable ion. The theoretical fine structure constants for the He2 ion are expected to␣aid future spectroscopic investigations of the fine structure splittings of the negative ion. Received: 14 April 1998 / Accepted: 27 July 1998 / Published online: 19 October 1998  相似文献   

17.
Chromium(III)-lutidinato complexes of general formula [Cr(lutH) n (H2O)6−2n ]3−n (where lutH is N,O-bonded lutidinic acid anion) were obtained and characterized in solution. Acid-catalysed aquation of [Cr(lutH)3]0 leads to only one ligand dissociation, whereas base hydrolysis produces chromates(III) as a result of subsequent ligand liberation steps. The kinetics of the first ligand dissociation were studied spectrophotometrically, within the 0.1–1.0 M HClO4 and 0.4–1.0 M NaOH range. In acidic media, two reaction stages, the chelate-ring opening and the ligand dissociation, were characterized. The dependencies of pseudo-first-order rate constants on [H+] are as follows: k obs1 = k 1 + k −1/K 1[H+] and k obs2 = k 2 K 2[H+]/(1 + K 2[H+]), where k 1 and k 2 are the rate constants for the chelate-ring opening and the ligand dissociation, respectively, k −1 is the rate constant for the chelate-ring closure, and K 1 and K 2 are the protonation constants of the pyridine nitrogen atom and coordinated 2-carboxylate group in the one-end bonded intermediate, respectively. In alkaline media, the rate constant for the first ligand dissociation depends on [OH]: k obs1 = k OH(1) + k O[OH], where k OH(1) and k O are rate constants of the first ligand liberation from the hydroxo- and oxo-forms of the intermediate, respectively, and K 2 is an equilibrium constant between these two protolytic forms. Kinetic parameters were determined and a mechanism for the first ligand dissociation is proposed. The kinetics of the ligand liberation from [Cr(lut)(OH)4]3− were also studied and the values of the pseudo-first-order rate constants are [OH] independent.  相似文献   

18.
The macroporous Li3V2(PO4)3/C composite was synthesized by oxalic acid-assisted carbon thermal reaction, and the common Li3V2(PO4)3/C composite was also prepared for comparison. These samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and electrochemical performance tests. Based on XRD and SEM results, the sample has monoclinic structure and macroporous morphology when oxalic acid is introduced. Electrochemical tests show that the macroporous Li3V2(PO4)3/C sample has a high initial discharge capacity (130 mAh g−1 at 0.1 C) and a reversible discharge capacity of 124.9 mAh g−1 over 20 cycles. Moreover, the discharge capacity of the sample is still 91.5 mAh g−1, even at a high rate of 2 C, which is better than that of the sample with common morphology. The improvement in electrochemical performance should be attributed to its improved lithium ion diffusion coefficient for the macroporous morphology, which was verfied by cyclic voltammetry and electrochemical impedance spectroscopy.  相似文献   

19.
The influence of the ion background (NaClO4, LiClO4, and HClO4) on the kinetics of the reaction PtdientH2O2++X→PtdientX++H2O(X=Cl, Br, I, SCN, and N3) was studied at 25°C by spectrophotometry. Changes in the rate constant with increase in the ionic strength are described by the Debye-Hückel and Gosh-Bjerrum equations. The reaction PtdienCl++H2O→PtdientH2O2++Cl was studied by potentiometry and its rate constant was established to depend weakly on variations of the medium. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1918–1921, October, 1998.  相似文献   

20.
The interaction of acetonitrile with superoxide radicals over a polycrystalline TiO2 (Degussa P25) surface was investigated using continuous-wave electron paramagnetic resonance (cw-EPR) spectroscopy. For the first time, a thermally unstable radical intermediate has been observed following the low-temperature exposure of acetonitrile to surface-adsorbed O2 radicals. The radical intermediate has been identified as an [O2···CH3CN] type surface complex characterised by the g values of g 1 = 2.031, g 2 = 2.010 and g 3 = 2.003. This surface complex is thermally unstable and decomposes at temperatures of T > 240 K. A second oxygen-centred species was also observed following acetonitrile adsorption, characterised by the spin Hamiltonian parameters of g 1 = 2.028, g 2 = 2.010, g 3 = 2.004, A 1 = 1.2 mT, A 2 = 1.0 mT and A 3 = 1.0 mT, and was assigned to a hydroperoxy radical (HO2).  相似文献   

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