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1.
The reaction of C3H8+O(3P)→C3H7+OH is investigated using ab initio calculation and dynamical methods. Electronic structure calculations for all stationary points are obtained using a dual-level strategy. The geometry optimization is performed using the unrestricted second-order Møller-Plesset perturbation method and the single-point energy is computed using the coupled-cluster singles and doubles augmented by a perturbative treatment of triple excitations method. Results indicate that the main reaction channel is C3H8+O(3P)→i-C3H7+OH. Based upon the ab initio data, thermal rate constants are calculated using the variational transition state theory method with the temperature ranging from 298 K to 1000 K. These calculated rate constants are in better agreement with experiments than those reported in previous theoretical studies, and the branching ratios of the reaction are also calculated in the present work. Furthermore, the isotope effects of the title reaction are calculated and discussed. The present work reveals the reaction mechanism of hydrogen-abstraction from propane involving reaction channel competitions is helpful for the under-standing of propane combustion. 相似文献
2.
CALCULATIONS OF STRETCHING VIBRATIONAL ENERGY LEVELS OF THE CH3I MOLECULE BY A NONLINEAR MODEL 下载免费PDF全文
A nonlinear model, i.e. the quantized discrete self-trapping equation, is applied to calculate the highly excited CH stretching vibrational energy levels of the CH3I molecule in the liquid phase at the electronic ground state up to n=8. The obtained results agree well with the experimental data and with those obtained from local mode model calculations. We note that the dominant feature of the methyl CH stretching vibrational energy levels of the CH3I molecule is a pattern of local mode pairs. When n≥7, all the vibrational energy of the CH3 group can nearly be localized on a single CH bond. 相似文献
3.
Activated carbon supported Mo-based catalysts were prepared and reduced under different activation atmospheres, including pure H2, syngas (H2/CO=2/1), and pure CO. The catalysts structures were characterized by X-ray diffraction, X-ray absorption fine structure, and in situ diffuse reflectance infrared Fourier transform spectroscopy. The catalytic performance for the higher alcohol synthesis from syngas was tested. The pure H2 treatment showed a high reduction capacity. The presence of a large amount of metallic Co0. and low valence state Moφ+ (0<φ<2) on the surface suggested a super activity for the CO dissociation and hydrogenation, which promoted hydrocarbons formation and reduced the alcohol selectivity. In contrast, the pure CO-reduced catalyst had a low reduction degree. The Mo and Co species at the catalyst mainly existed in the form of Mo4+ and Co2+. The syngas-reduced catalyst showed the highest activity and selectivity for the higher alcohols synthesis. We suggest that the syngas treatment had an appropriate reduction capacity that is between those of pure H2 and pure CO and led to the coexistence of multivalent Co species as well as the enrichment of Moδ+ on the catalyst''s surface. The synergistic effects between these active species provided a better cooperativity and equilibrium between the CO dissociation, hydrogenation and CO insertion and thus contributed beneficially to the formation of higher alcohols. 相似文献
4.
The electrode reaction was examined on ceria coated YSZ by a platinum point electrode in H2-H2O atmosphere at 973 K- 1173 K. The thickness of the ceria coating layer was altered from 0 to 2.5 μm, fabricated by a laser
ablation and by a vacuum vapor deposition method on YSZ single crystals. The electrode / electrolyte interface conductivity
increased with 1/4 powers ofp(H2) andp(H2O) on both ceria coated and non-coated YSZ. The interface conductivity was significantly improved on a thicker ceria coating
surface than 1 μm. The effective electrode reaction radius also increased in a thick ceria coating. The18O/16O exchange experiment at low oxygen partial pressure revealed that the oxygen surface exchange rate of ceria is not high compared
with that of YSZ. It can be concluded that the bulk ionic conduction of ceria makes a more effective contribution to the electrode
reaction than the surface catalytic activity in H2-H2O atmosphere.
Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997 相似文献
5.
The impact of excited state muon transfer in dμ + H2 collisions has been investigated. The formation of metastable pdμ* molecules and their subsequent decay into the pμ (1s) + d channel opens a transfer channel that is otherwise closed at the n=2 level. This mechanism enlarges the fraction of muons arriving to the ground state of the lighter isotope. The resulting ground
state population P
1s
pμ
as function of deuterium concentration appears to be in qualitative agreement with recent measurements of the K
α
X-ray yield in H2/D2 mixtures.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
The possible existence of complexes formed by the C60 fullerene or its derivatives with transition metals interacting with the carbon cage via η6−π type bonding is discussed. The derivatives C60
R
6 of the C60 fullerene (R = −, H, F, Cl, Br, CN) are analyzed using the density functional method within the Perdew-Burke-Ernzerhof approximation.
In these molecules, the R groups are attached to carbon atoms located in the α positions with respect to the common hexagon of the C60 fullerene. The structure and electron configuration of complexes formed by these molecules with Cr(C6H6), Cr(CO)3, MoC6H6, and Mo(CO)3 particles are modeled. The “dimer” systems C60R6-M-R
6C60 (M = Cr, Mo, R =-, H, F) are investigated in which two fullerene molecules interact via a transition-metal atom. It is found that the introduction
of six R groups in the α sites with respect to the common hexagon of C60 favors the formation of complexes of these derivatives of the C60 fullerene with the Cr(C6H6), Cr(CO), Mo(C6H6), and Mo(CO)3 particles in which η6-π type bonds arise between the metal and the atoms of the hexagon fringed with the R groups. It is also demonstrated that analogous complexes with a “bare” C60 fullerene are possible, but they are significantly less stable. The (C6H6) M-R
6C60
R
6-M (C6H6) complexes of particles M(C6H6) (M= Cr, Mo) and derivatives R
6C60
R
6 (R =-, H, F, Cl, Br) are studied. In the R
6C60
R
6 molecule, six R groups are located in the α sites with respect to the common hexagon of the C60 fullerene and six other groups fringe the opposite hexagon. The obtained results can be applied to planning synthesis of
new complexes that C60 fullerene derivatives can form with transition metals.
Original Russian Text ¢ E.G. Gal’pern, A.R. Sabirov, I.V. Stankevich, 2007, published in Fizika Tverdogo Tela, 2007, Vol.
49, No. 12, pp. 2220–2223. 相似文献
7.
The complex balance of processes occurring at the cascade of exotic H-atoms is usually described by the so-called standard
cascade model, but this model neglects variations of the kinetic energy T of the exotic atom during the cascade which are crucial for the analysis of several important experiments. New experimental
results on T
μp at H2 pressures between 0.063 and 4 hPa demonstrate the importance of acceleration due to Coulomb de-excitation processes at highly
excited μp levels n > 9. The data at the lowest density are sensitive to the initial values of the kinetic energy and n-levels at the moment of atomic capture. From the measured low-energy tail of the T
μp-distribution it can be concluded that a considerable part of the μp(2s) atoms is metastable at pressures of a few hPa.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
Keka Chakraborty S K Paranjpe V Siruguri O D Jayakumar S K Kulshreshtha 《Pramana》1997,48(6):1115-1122
Neutron diffraction and M?ssbauer measurements have been carried out on the cubic Laves phase intermetallic TbMnFe. The magnetic
moment on the transition metal atom is found to be low, 0.2μ
B, at room temperature. This moment is temperature independent down to 10 K. Magnetic moment on the rare earth atom varies
from 2.5μ
B at 296 K to 7.27μ
B at 10 K. M?ssbauer spectra recorded at 298 K and 78 K have magnetic character but there is a large distribution of hyperfine
field values. Both these features arise due to magnetic frustration created in the sample due to the competing ferro and antiferromagnetic
interactions between the transition metal atoms. 相似文献
9.
We study the role of dislocation loops defects on the elasticity of lamellar phases by investigating the variation of the
lamellar elastic constants, ˉ and K, induced by the proliferation of these defects. We focus our interest on one particular lamellar phase made up of a mixture
of C12E5 and DMPC in water, which is already well-characterised. This lamellar phase undergoes a second-order (or weakly first-order)
lamellar-to-nematic phase transition at about 19°C and dislocation loops are seen to proliferate within the lamellar structure when temperature is decreased below 30°C. The values of both elastic constants of this given lamellar phase are measured as a function of temperature, approaching
the lamellar-to-nematic transition, with the help of Quasi-Elastic Light Scattering (QELS) on oriented lamellar phases. Very
surprisingly we observe a strong and rapid increase in both ˉ and K as the lamellar-to-nematic transition temperature is approached. These increases are seen to start as soon as dislocation
loops can be observed in the lamellar phase. We interpret our results as being the consequence of the appearance and proliferation
of dislocation loops within the lamellar structure. According to a simple model we developped we show that ˉ and K are proportional to the density of dislocation loops in the lamellar phase. 相似文献
10.
Close coupling calculations have been carried out for rotational excitations in He-H2 collisions with symmetric isotopic substitution (He-H2, D2, T2) and asymmetric isotopic substitution (He-HD, HT, DT). Cross sections have been obtained at the incidence energy of 0.3eV. Based on the calculations, the effect of isotopic substitution on atom-diatom collisions is discussed. 相似文献
11.
K.V. Ivanovskikh A. Meijerink A. Speghini C. Ronda M. Bettinelli 《Journal of luminescence》2010,130(5):893-16384
The silicates Ca3Sc2Si3O12, Ca3Y2Si3O12 and Ca3Lu2Si3O12, both undoped and doped with Pr3+ ions, have been synthesized by solid-state reaction at high temperature. The luminescence spectroscopy and the excited state dynamics of the materials have been studied upon VUV and X-ray excitation using synchrotron radiation. All doped samples have shown efficient 5d-4f emission upon direct VUV excitation of 5d levels, but only Ca3Sc2Si3O12:Pr3+ shows luminescence upon interband VUV or X-ray excitation. The VUV excited emission spectra of Ca3Y2Si3O12:Pr3+ and Ca3Lu2Si3O12:Pr3+ show features attributed to emission from two distinct sites accommodating the Pr3+ dopant. The decay kinetics of the Pr3+ 5d-4f emission in Ca3Sc2Si3O12:Pr3+ upon VUV excitation across the band gap are characterized by decay times in the range 25-28 ns with no significant rise after the excitation pulse. They appear to be faster upon X-ray irradiation than for VUV excitation. Weak afterglow components are attributed to defect luminescence. 相似文献
12.
13.
R.Z. Mehdiyeva Mir Hasan Yu. Seyidov I.B. Baykulov 《Journal of Physics and Chemistry of Solids》2006,67(12):2623-2627
Boundaries of morphotropic phase transitions region in the system of solid solutions K2Pb4Nb10O30-Na2Pb4Nb10O30-K6W4Nb6O30 with the structure of the tetragonal tungsten bronze have been specified. Presence of the second morphotropic phase transition, perpendicular to the first one has been revealed. The temperature dependences of the structural parameters of some compounds have been investigated. The compounds with high values of Curie temperatures and working temperatures have been obtained. 相似文献
14.
15.
Arti Gupta 《Journal of magnetism and magnetic materials》2010,322(8):1020-3390
Results of detailed structural, dielectric, magnetic and magnetoelectric studies of (x)PbZr0.52Ti0.48O3-(1−x)Mn0.3Co0.6Zn0.4Fe1.7O4 composites where x=65, 70, 75 and 80 are shown in this work. Manganese substituted cobalt ferrites are known to exhibit large strain derivative (dx/dH) and on the other hand substitution of Zn in pure cobalt ferrite is known to enhance its permeability μ and permittivity ε. The choice of ferrite as Mn, Zn simultaneously substituted cobalt ferrite (MCZFO) is made keeping in view that for good magnetoelectric (ME) voltage coefficient the magnetostrictive constituent phase of the composite should have large strain derivative (dx/dH) along with large permittivity and permeability. It is shown here that although the dielectric transition temperature changes significantly with change in the mole ratio of the two component phases, magnetic transition temperature (much less compared to the bulk cobalt ferrite) is relatively non-responsive to the changing molar ratio of the two component phases. In the vicinity of the magnetic transition temperature we observed an anomaly in tan δ vs. T plots, which indicates a possible magnetoelectric coupling in the samples. Magnetoelectric voltage coefficient (αE) has been measured using static magnetoelectric method. Highest magnetoelectric voltage coefficient (αE=0.312 mV/cmOe) is obtained for sample 80:20 at HDC=1000 Oe. 相似文献
16.
An experimental study of proximity effect in La0.67Sr0.33MnO3-YBa2CU3O7-La0.67Sr0.33MnO3 trilayers is reported. Transport measurements on these samples show clear oscillations in critical current (I
c) as the thickness of La0.67Sr0.33MnO3 layers (d
F) is scanned from ∼50 ? to ∼ 1100 ?. In the light of existing theories of ferromagnet-superconductor (FM-SC) heterostructures,
this observation suggests a long range proximity effect in the manganite, modulated by its weak exchange energy (∼2 meV).
The observed modulation of the magnetic coupling between the ferromagnetic LSMO layers as a function of d
F, also suggests an oscillatory behavior of the SC order parameter near the FM-SC interface.
相似文献
17.
D.V. Bugg 《Physics letters. [Part B]》1974,52(1):102-104
Recent data on the reaction show four conspicuous dips in the angular distribution at fixed values of ν = t?u. The conjecture is made that the channel π?π+ → π?π+ has zeros at the same ν values. Using data of the CERN-Munich group, one can follow the zeros through the whole Mandelstam plane. The zeros pass through the intersections of s and t channel poles, as the Veneziano model predicts; however, away from these intersections, they propagate in a fashion systematically quite different from Veneziano's ansatz. 相似文献
18.
The Aurivillius type oxide Bi1.9Te0.1SrNb1.9Hf0.1O9 has been studied by Perturbed Angular Correlations spectroscopy using 181Ta probes. The spin precession curves were measured from room temperature up to 873 K. Two sites are occupied by probes and the temperature dependence of both indicates a continuous phase transition at about 625 K. One site is ordered while the other is disordered. This situation is analyzed in terms of simple models already applied to perovskites. The transition temperature of the solid solution Bi2−xTexSrNb2−xHfxO9 (with 0≤x≤0.5) shows a strong dependence on composition. 相似文献
19.
Marcel Snels 《Journal of Molecular Spectroscopy》2004,224(1):13-17
The infrared spectrum of isotopically pure CH279BrCl has been recorded at a resolution of 0.0023 cm−1 (FWHM) in the range 550-800 cm−1 with a Bruker IFS 120 HR Fourier transform spectrometer in Wuppertal. Here we report the full rotational analysis of the ν4 and ν5 fundamentals and of the hot-bands ν4+ν6−ν6 and ν5+ν6−ν6. Ground state combination differences were constructed for all bands, yielding improved ground state constants, up to quartic terms, as well as reliable rotational constants for the ν4, ν5, and ν6 states. 相似文献
20.
R.I. Dzhelyadin S.V. Golovkin M.V. Gritsuk D.B. Kakauridze V.A. Kachanov A.K. Konoplyannikov A.S. Konstantinov V.F. Konstantinov V.P. Kubarovski A.V. Kulik L.G. Landsberg V.M. Leontiev V.A. Mukhin V.F. Obraztsov T.I. Petrunina N.S. Pokrovski Yu.D. Prokoshkin V.A. Victorov A.M. Zaitsev 《Physics letters. [Part B]》1979,84(1):143-144
The results of studying the mass spectrum of μ+μ?γγ systems produced in π?p collisions at 25 and 33 GeV/c presented. The wide-aperture magnetic spectrometer with a hodoscope γ-detector was used to identify muon pairs and photons. There is a clear peak in the mass spectrum which corresponds to the decay ω → π0μ+μ? previously not observed. The branching ratio for the decay is estimated to be 9 × 10?5 with a systematic error of 50%. 相似文献