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1.
Emission spectra of SrH and SrD have been studied at high resolution using a Fourier transform spectrometer. The molecules have been produced in a high temperature furnace from the reaction of strontium metal vapor with H2/D2 in the presence of a slow flow of Ar gas. The spectra observed in the 18 000–19 500 cm?1 region consist of the 0–0 and 1–1 bands of the E2Π–X2Σ+ transition of the two isotopologues. A rotational analysis of these bands has been obtained by combining the present measurements with previously available pure rotation and vibration–rotation measurements for the ground state, and improved spectroscopic constants have been obtained for the E2Π state. The present analysis provides spectroscopic constants for the E2Π state as ΔG(½) = 1166.1011(15) cm?1, Be = 3.805503(32) cm?1, αe = 0.098880(47) cm?1, re = 2.1083727(89) Å for SrH, and ΔG(½) = 839.1283(23) cm?1, Be = 1.918564(15) cm?1, αe = 0.034719(23) cm?1, re = 2.1121943(83) Å for SrD.  相似文献   

2.
Kinetic models for complex chemical mechanisms are comprised of tens to thousands of reactions with rate constants informed by data from a wide variety of sources – rate constant measurements, global combustion experiments, and theoretical kinetics calculations. In order to integrate information from distinct data types in a self-consistent manner, a framework for combustion model development is presented that encapsulates behavior across a wide range of chemically relevant scales from fundamental molecular interactions to global combustion phenomena. The resulting kinetic model consists of a set of theoretical kinetics parameters (with constrained uncertainties), which are related through kinetics calculations to temperature/pressure/bath-gas-dependent rate constants (with propagated uncertainties), which in turn are related through physical models to combustion behavior (with propagated uncertainties). Direct incorporation of theory in combustion model development is expected to yield more reliable extrapolation of limited data to conditions outside the validation set, which is particularly useful for extrapolating to engine-relevant conditions where relatively limited data are available. Several key features of the approach are demonstrated for the H2O2 decomposition mechanism, where a number of its constituent reactions continue to have large uncertainties in their temperature and pressure dependence despite their relevance to high-pressure, low-temperature combustion of a variety of fuels. Here, we use the approach to provide a quantitative explanation for the apparent anomalous temperature dependence of OH + HO2 = H2O + O2 – in a manner consistent with experimental data from the entire temperature range and ab initio transition-state theory within their associated uncertainties. Interestingly, we do find a rate minimum near 1200 K, although the temperature dependence is substantially less pronounced than previously suggested.  相似文献   

3.
Photo-absorption spectrum of carbonyl sulphide (OCS) is recorded in 30,000–91,000 cm?1 (3300–1050 Å) region at an average resolution of 1.2 Å using Photo-physics beamline on the 450 MeV Indus-1 synchrotron radiation source at RRCAT Indore, India. Owing to significant absorption cross section dependence, spectra of OCS are recorded at various pressures (0.001–5 mbar) to optimize the S/N ratio for band systems appearing at different energy regions. The spectral region below 70,000 cm?1 has contributions from dissociation mechanism of the ground state of OCS and three valence band systems arising from promotion of a 3π electron to 4π and 10σ orbital. Improved S/N ratio helped in unambiguous assignment of the valence band progressions at 42,000–48,000 cm?1, 53,000–62,000 cm?1 and 63,500–70,000 cm?1 regions to the 1Δ←X1Σ+ transition, the relatively intense and sharp bands of 1Π←X1Σ+ transition and intense but broad bands of 1Σ+←X1Σ+ transition, respectively, and obtain the vibrational frequencies. Above 70,000 cm?1 Rydberg series arising from s, p, d and f orbitals converging to the ionic ground state X2Π of OCS+ (90,121 cm?1) are identified. Long progression in the first few members of the Rydberg series is suggestive of mixed valence character. Quantum defects are evaluated and used to discuss the nature of the molecular orbital. The present study provides a unifying picture of the VUV photo-absorption spectrum of OCS up to its first ionization limit.  相似文献   

4.
The absorption spectrum of the 18O3 isotopologue of ozone was recorded by CW-Cavity Ring Down Spectroscopy in the 6950–7125 cm?1 region. The typical noise equivalent absorption of the recordings is αmin ≈1×10?10 cm?1. The spectrum is dominated by three very weak bands: 3ν1+5ν3 near 7009 cm?1 and the ν2+7ν3 and 4ν2+5ν3 interacting bands near 7100 cm?1. In total 260, 206 and 133 transitions were assigned for the 3ν1+5ν3, ν2+7ν3 and 4ν2+5ν3 bands, respectively. The line positions of the 3ν1+5ν3 band were modelled using an effective Hamiltonian (EH) model involving two dark states – (6 0 1) and (2 5 2) – in interaction with the (3 0 5) bright state. The EH model developed for the ν2+7ν3 and 4ν2+5ν3 bands involves only the (0 1 7) and (0 4 5) interacting bright states. Line positions could be reproduced with rms deviations on the order of 0.01 cm?1 and the dipole transition moment parameters were determined for the three observed bands. The obtained set of parameters and the experimentally determined energy levels were used to generate a list of 984 transitions of the three bands which is provided as Supplementary Material.  相似文献   

5.
The effects of ultraviolet radiation-B (UVBR) in apical segments of the red macroalgae Gracilaria domingensis (Kützing) Sonder ex Dickie were examined in vitro. Over a period of 21 days, the segments were cultivated and exposed to photosynthetically active radiation (PAR) at 80 μmol photons m?2 s?1 and PAR + UVBR at 1.6 W m?2 for 3 h per day. The samples were processed for electron microscopy, as well as histochemical analysis, and growth rate, photosynthetic pigment contents and photosynthetic performance were measured. Toluidine Blue reaction showed metachromatic granulations in vacuole and lenticular thickness, while Coomassie Brilliant Blue showed a higher concentration of cytoplasmic organelles, and Periodic Acid Schiff stain showed an increase in the number of floridean starch grains. UVBR also caused changes in the ultrastructure of cortical and subcortical cells, which included an increased number of plastoglobuli, changes in mitochondrial organization, destruction of chloroplast internal organization, and the disappearance of phycobilisomes. The algae cultivated under PAR-only showed growth rates of 6.0% day?1, while algae exposed to PAR + UVBR grew only 2.8% day?1. Compared with algae cultivated with PAR-only, the contents of photosynthetic pigments, including chlorophyll a, phycoerythrin, phycocyanin and allophycocyanin, decreased after exposure to PAR + UVBR, and significant differences were observed. Finally, analysis of these four photosynthetic parameters also showed reduction after exposure to PAR + UVBR: maximum photosynthetic rate, photosynthetic efficiency, photoinhibition and relative electron transport rate. Taken together, these findings strongly suggested that UVBR negatively affects the agarophyte G. domingensis.  相似文献   

6.
Densities and viscosities of ternary mixtures of 2-pyrrolidone + 1,2-propanediol + water and corresponding binary mixtures of 1,2-propanediol + water, 2-pyrrolidone + water and 2-pyrrolidone + 1,2-propanediol have been measured over the whole composition range at 313.15 K. From the obtained data, the excess molar volumes (VE), the deviations in viscosity (Δη) and the excess Gibbs free energy of activation (ΔG?E) have been calculated. The VE, Δη and ΔG?E results were correlated and fitted by the Redlich–Kister equation for binary mixtures and by the Cibulka equation for ternary mixtures, as a function of mole fraction. Several predictive empirical relations were applied to predict the excess molar volumes of ternary mixtures from the binary mixing data.  相似文献   

7.
《Solid State Ionics》2006,177(19-25):1619-1624
The kinetics of the electrochemical reduction of molecular nitrogen at gold micro electrodes on yttria stabilized zirconia (YSZ) solid oxide electrolyte is studied by steady state polarization measurements. From the η / lg i plot for both cathodic and anodic polarization the apparent transfer coefficients αa and αc are evaluated. The sum of αa + αc exceeds unity and thus a multistep electron transfer process is suggested. The concept of the stoichiometric number is applied to the electrode reaction N2 + 6e = 2N3− supposing that the overall process involves at least two intermediate species. On the basis of the evaluation of the experimental results the reaction N2 + e  N22− is suggested as the rate determining reaction step for the cathodic nitrogen reduction and nitride formation.  相似文献   

8.
Hydrogen peroxide (H2O2) and hydroperoxy (HO2) reactions present in the H2O2 thermal decomposition system are important in combustion kinetics. H2O2 thermal decomposition has been studied behind reflected shock waves using H2O and OH diagnostics in previous studies (Hong et al. (2009) [9] and Hong et al. (2010) [6,8]) to determine the rate constants of two major reactions: H2O2 + M  2OH + M (k1) and OH + H2O2  H2O + HO2 (k2). With the addition of a third diagnostic for HO2 at 227 nm, the H2O2 thermal decomposition system can be comprehensively characterized for the first time. Specifically, the rate constants of two remaining major reactions in the system, OH + HO2  H2O + O2 (k3) and HO2 + HO2  H2O2 + O2 (k4) can be determined with high-fidelity.No strong temperature dependency was found between 1072 and 1283 K for the rate constant of OH + HO2  H2O + O2, which can be expressed by the combination of two Arrhenius forms: k3 = 7.0 × 1012 exp(550/T) + 4.5 × 1014 exp(?5500/T) [cm3 mol?1 s?1]. The rate constants of reaction HO2 + HO2  H2O2 + O2 determined agree very well with those reported by Kappel et al. (2002) [5]; the recommendation therefore remains unchanged: k4 = 1.0 × 1014 exp(?5556/T) + 1.9 × 1011+exp(709/T) [cm3 mol?1 s?1]. All the tests were performed near 1.7 atm.  相似文献   

9.
The absorption spectrum of the 16O3 isotopologue of ozone was recorded in the 7000–7920 cm?1 region by using high sensitivity CW-Cavity Ring Down Spectroscopy (αmin  10?10 cm?1). This report is devoted to the analysis of the 7300–7600 cm?1 region dominated by four A-type bands: 6ν1 + ν3 centred around 7395 cm?1, 3ν1 + 5ν2 + ν3 and 2ν1 + 4ν2 + 3ν3 lying in the 7450 cm?1 region and 5ν1 + 2ν2 + ν3 centred around 7579 cm?1. 213 transitions of the 6ν1 + ν3 band were assigned and the corresponding line positions were modeled using an effective Hamiltonian including a Coriolis resonance interaction between the (601) upper state and a A-type dark state. The two very close 3ν1 + 5ν2 + ν3 and 2ν1 + 4ν2 + 3ν3 bands were analysed using a similar effective Hamiltonian scheme involving the anharmonic resonance coupling between the (351) and (243) states. For these two bands, 304 transitions were assigned. The modelling also includes a first Coriolis resonance interaction between the (351) bright state and the (530) dark state, and a second one between the (243) bright state and the (144) dark state. In the 7579 cm?1 region, 205 transitions of the 5ν1 + 2ν2 + ν3 band were assigned and modelled taking into account the Coriolis resonance interactions between the (521) upper state and the (700), (342) and (280) dark states.The dipole transition moment parameters of the four analysed bands were determined by a least-squares fit to the measured line intensities. For the studied band systems, the effective Hamiltonian and transition moment operator parameters were used to generate line lists provided as Supplementary Materials.  相似文献   

10.
The kinetics of the reaction of hydrogen atoms with 2,5-dimethylfuran (25DMF), a promising liquid transport biofuel, was experimentally studied in a shock tube at temperatures between 970 and 1240 K and pressures of 1.6 and 4.8 bar. The hydrogen atoms were produced by pyrolysis of ethyl iodide and monitored by atom resonance absorption spectrometry. From the hydrogen atom concentration–time profiles, overall rate coefficients for the reaction H + 25DMF  products (R1) were inferred. The results can be expressed by the Arrhenius equation k1 = 4.4 × 10?11 exp(?1180 K/T) cm?3 s?1 with an estimated uncertainty of ±30%. A significant pressure dependence was not observed. The results were analyzed in terms of statistical rate theory with molecular and transition state data from quantum chemical calculations. Three different compound methods were used to characterize the potential energy surface: CBS-QB3, CBS-APNO, and G3. It is found that reaction (R1) mainly (>75%) proceeds via an addition–elimination mechanism to yield 2-methylfuran + CH3. Kinetic parameters for the most important competing channels of the net reaction (R1) were calculated.  相似文献   

11.
Continuous-time photoelectron spectroscopy (PES) and photon-exposure-dependent photon-stimulated desorption (PSD) were employed to investigate the monochromatic soft X-ray-induced dissociation of SF6 molecules adsorbed on Si(111)-7 × 7 at 30 K (SF6 dose = 3.4 × 1013 molecules/cm2, ~ 0.5 monolayer). The photon-induced evolution of adsorbed SF6 was monitored at photon energies of 98 and 120 eV [near the Si(2p) edge], and sequential valence-level PES spectra made it possible to deduce the photolysis cross section as a function of energy. It was found that the photolysis cross sections for 98 and 120 eV photons are ~ 2.7 × 10? 17 and ~ 3.7 × 10?17 cm2, respectively. The changes in the F? and F+ PSD ion yields were also measured during irradiation of 120 eV photons. The photon-exposure dependencies of the F? and F+ ion yields show the characteristics: (a) the dissociation of adsorbed SF6 molecules is ascribable to the substrate-mediated dissociations [dissociative attachment (DA) and dipolar dissociation (DD) induced by the photoelectrons emitting from the silicon substrate]; (b) at early stages of photolysis, the F? yield is mainly due to DA and DD of the adsorbed SF6 molecules, while at high photon exposure the F? formation by electron capture of the F+ ion is likely to be the dominant mechanism; (c) the F+ ion desorption is associated with the bond breaking of the surface SiF species; (d) the surface SiF is formed by reaction of the surface Si atom with the fluorine atom or F? ion produced by scission of S–F bond of SFn (n = 1–6) species.  相似文献   

12.
T.B. Wang  H.Y. Xie  W.J. Xu 《Optik》2012,123(2):181-184
We proposed a spectrum method to determine birefraction of the sample. When the infrared incident light transmits in the birefraction direction of the cube crystal, because of the birefraction of the sample, the transmit spectrum appears interference fringes. The equation Δn = 1/[D(/dm)] shows the relationship between the birefraction and the wave-number, with the interference-number of crystals in the infrared band at room temperature. Via the infrared transmitting along the x-axis of cube lithium niobate crystal, the interference fringes were found. By the fitted polynomial method, the relationship of the birefraction and the wave-number or wavelength of the lithium niobate crystal be educed, which is, Δn = 0.4149 ? 9.00174 × 10?5υ + 5.64347 × 10?9υ2,or n = 0.05366 ? 5.20334 × 10?5λ + 3.99694 × 10?8λ2.  相似文献   

13.
Using high-resolution Fourier transform spectra of trans-HCOOH recorded at 5.6 μm, we carried out an extensive analysis of the strong ν3 fundamental band (carbonyl stretching mode) at 1776.83 cm?1, starting from results of a previous analysis [Weber WH, Maker PD, Johns JWC, Weinberger E. J Mol Spectrosc 1987; 121: 243–60]. As pointed out in the literature, the ν3 band is significantly perturbed by resonances due to numerous dark bands. We were able to assign series belonging to the ν57, ν59, ν67 and ν69 dark bands, located at 1843.48, 1792.63, 1737.96 and 1726.40 cm?1, respectively. The model used to calculate energy levels accounts partly for the observed resonances, and enabled us to reproduce most of the observed line positions, within their experimental uncertainties. We also determined absolute line intensities with an accuracy estimated to 15%. Finally, we generated, for the first time, a list of line parameters for the 5.6 μm region of trans-formic acid.  相似文献   

14.
The radiation stability of the mixed crystals M1 ? xRxF2 + x (M = Ca, Sr, Ba) depends on types of the alkaline-earth and rare-earth ions. Different to Eu- and Ce-containing systems, M1 ? xPrxF2 + x solid solutions have a low radiation resistance, which may be associated with hole trapping on praseodymium ion according to the reaction Pr3+  Pr4+ which is typical for praseodymium. The coloration efficiency of M1 ? xPrxF2 + x crystals grows in the row Ca  Sr  Ba, which is explained satisfactorily within the model of rare-earth clusters, the structure of which is determined by the ratio of the base alkaline-earth cation to the praseodymium ion radii.  相似文献   

15.
In this paper we report an analytical modeling of N+-InP/n0-In0.53Ga0.47As/p+-In0.53Ga0.47As p-i-n photodetector for optical fiber communication. The results obtained on the basis of our model have been compared and contrasted with the simulated results using ATLAS? and experimental results reported by others. The photodetector has been studied in respect of energy band diagram, electric field profile, doping profile, dark current, resistance area-product, quantum efficiency, spectral response, responsivity and detectivity by analytical method using closed form equations and also been simulated by using device simulation software ATLAS? from SILVACO® international. The photodetector exhibits a high quantum efficiency ~90%, responsivity ~1.152–1.2 A/W in the same order as reported experimentally by others, specific detectivity ~5 × 109 cm Hz1/2 W?1at wavelength 1.55–1.65 μm, dark current of the order of 10?11 A at reverse bias of 1.5 V and 10?13–10?12 A near zero bias. These values are comparable to those obtained for practical p-i-n detectors. The estimated noise equivalent power (NEP) is of the order of 2.5 × 10?14 W.  相似文献   

16.
An analysis of the intense blue upconversion emission at 476 and 488 nm in Tm3 +/Yb3 + codoped Y2O3 under excitation power density of 86.7 W/cm2 available from a diode laser emitting at 976 nm, has been undertaken. Fluorescence intensity ratio (FIR) variation of temperature-sensitive blue upconversion emission at 476 and 488 nm in this material was recorded in the temperature range from 303 to 753 K. The maximum sensitivity derived from the FIR technique of the blue upconversion emission is approximately 0.0035 K? 1. The results imply that Tm3 +/Yb3 + codoped Y2O3 is a potential candidate for the optical temperature sensor.  相似文献   

17.
18.
Total charge-changing cross sections and cross sections for the production of projectile-like fragments were determined for fragmentation reactions induced by 370 MeV/n 20Ne ions in water and lucite, and 490 MeV/n 24Mg ions in polyethylene, carbon and aluminum targets sandwiched with CR-39 plastic nuclear track detectors. An automated microscope system and a track-to-track matching algorithm were used to count and recognize the primary and secondary particles. The measured cross sections were then compared with published cross sections and predictions of different models. Two models and the three-dimensional Monte Carlo Particle Heavy Ion Transport Code System (PHITS) were used to calculate total charge-changing cross sections. Both models agreed within a few percent for the system 24Mg + CH2, however a deviation up to 20% was observed for the systems 20Ne + H2O and C5H8O2, when using one of the models. For all the studied systems, PHITS systematically underestimated the total charge-changing cross section. It was also found that the partial fragmentation cross sections for 24Mg + CH2 measured in present and earlier works deviated up to 20% for Z = 6–11. Measured cross sections for the production of fragments (Z = 4–9) for 20Ne + H2O and C5H8O2 were compared with predictions of three different semi-empirical models and JQMD which is used in the PHITS code. The calculated cross sections differed from the measured data by 10–90% depending on which fragment and charge was studied, and which model was used.  相似文献   

19.
Here we explore the exceptional structural characteristics of a set of graphene-related materials prepared by a wet chemical approach. We present a comprehensive study of the effects of morphology, sonication, temperature, probe species, and stacking behaviour on the measurement of graphene surface area. Nitrogen gas was used in the solid state gas adsorption measurements and methylene blue dye for adsorption measurements on aqueous dispersions of graphene. The surface area values obtained are among the highest reported for synthetic graphenes: 1700 m2 g? 1 in aqueous dispersions and 612 m2 g? 1 in the solid state. Microscopy revealed the graphene used in the study was present in large part as free sheets and electron diffraction confirmed the successful synthesis of high quality graphene with a regular C–C bond length of 1.41 ± 0.02 Å.  相似文献   

20.
The adsorption and desorption of the system CO/Pt(111) and C6H6/Pt(111) at 300 K has been investigated with a pulsed molecular beam method in combination with a microcalorimeter. For benzene the sticking probability has been measured in dependence of the coverage θ. For coverages θ > 0.8 transient adsorption is observed. From an analysis of the time-dependence of the molecular beam pulses the rate constant for desorption is determined to be 5.6 s? 1. With a precursor-mediated kinetic adsorption model this allows to obtain also the hopping rate constant of 95.5 s? 1. The measured adsorption enthalpies could be best described by (199 ? 77θ ? 51θ2) kJ/mol, in good agreement with the literature values. For CO on Pt(111) also transient adsorption has been observed for θ > 0.95 at 300 K. The kinetic analysis yields rate constants for desorption and hopping of 20 s?1 and 51 s?1, respectively. The heats of adsorption show a linear dependence on coverage (131 ? 38θ) kJ/mol between 0  θ  0.3, which is consistent with the desorption data from the literature. For higher coverage (up to θ = 0.9ML) a slope of ?63 kJ/mol describes the decrease of the differential heat of adsorption best. This result is only compatible with desorption experiments, if the pre-exponential factor decreases strongly at higher coverage. We found good agreement with recent quantum chemical calculations made for (θ = 0.5ML).  相似文献   

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