共查询到20条相似文献,搜索用时 15 毫秒
1.
Hyung Kyu Shin 《Chemical physics letters》1976,37(1):143-146
A semiclassical approach is developed to study vibrational energy transfer in H2 + He by use of the a priori interaction potential including all nonzero impact parameter collisions. The calculated values of the rate coefficient are found to be in excellent agreement with experimental data which are available in the temperature ranges 60–450 K and 1350-3000 K. The temperature dependence is shown to seriously deviate from the Landau-Teller prediction below 1000 K. The calculation was carried out over the temperature range of 30 to 10000 K. 相似文献
2.
Isochoric PVTx measurements have been performed for the binary system of nitrous oxide + CH3F (R41), +CH2F2 (R32), and +CHF3 (R23) using a new experimental set-up. The experiments covered both the two-phase region and the superheated vapor region and were performed within the temperature range 214–358 K and within a pressure range from 270 to 5600 kPa. Data have been collected for not less than four compositions for each system. The vapor–liquid equilibrium data were derived correlating the experimental data by means of the Carnahan–Starling–De Santis equation of state. The studied systems show a positive deviation from the Raoult's law. The results obtained were compared with the Burnett PVTx data. The two methods showed a mutual consistency within an acceptable margin of error. No other experimental PVTx data were found in the literature for these binary systems. 相似文献
3.
FTIR studies of the CH3CN–BF3 complex in solid Ar, N2, and Xe: Matrix effects on vibrational spectra
FTIR spectra of the four isotopically substituted 1:1 complexes of acetonitrile and boron trifluoride were recorded in Ar, N2 and Xe matrices. In Ar, previously unreported three vibrational modes of the complex were clearly observed. Several significant vibrational bands were also observed in N2 and Xe. The observed frequency shifts on complexation, Δν, were qualitatively in good agreement with the computational results, which were calculated at the B3LYP/6-311++G(d,p) level using the optimized geometry of the C3v eclipsed conformation. The observed magnitudes of Δν for most of the complex bands were larger than the calculated values. The BF3 symmetric deformation mode is an exception. The observed frequency shits for this mode were smaller than the calculated values, especially in N2. This suggests that even an inert matrix can significantly affect the vibrational spectrum of the complex. 相似文献
4.
A Bayard-Alpert (BA) gauge was used to determine apparent relative sensitivites Srel,X for O2, N2O, NO, NO2, NH3, CClF3 and CH3OH from gauge calibration measurements in the range 1.3×10–1 Pap1.3·10–3Pa. Nitrogen was used as a calibration standard. 相似文献
5.
Infrared fluorescence has been observed from the ν1, ν6, 2ν9, ν8 and ν4 levels of CH2F2 following excitation by a 9.6 μ Q-switch CO2 laser. All the observed states exhibit a single exponential decay rate of approximately 44 msec?1 torr?1. The rare gas dependence of this rate has also been measured and found to be up to 20 times slower than the rate for the pure gas. Measurements of the risetimes of the observed fluorescence signals yielded an upper limit of 5 μsec at 1 torr for the ν1, ν6 and ν8 levels. The 2ν9 and ν4 risetimes were effectively instantaneous under the experimental conditions that prevailed. The relative magnitudes of the measured rate are discussed in terms of existing V-T/R theories and collisional energy transfer processes. 相似文献
6.
Inefficient vibrational energy exchange between the lowest vibrational mode and the higher lying vibrational modes of CH2Cl2, CD2Cl2, CH2ClBr and CH2Br2 was investigated by ultrasonic absorption experiments. Breathing sphere theory is used to interpret the data available for VV and VR, T transfer in methylene halides. 相似文献
7.
Rate coefficients for collisional removal of O(1D) by six atmospheric gases have been measured by monitoring the appearance of O(3P) following photolytic production of O(1D). The measured values, kM±2σ, in units of 10?11 cm?3 molecule ?1 s?1 are kO3 = 22.8±2.3, kN2 = 2.52 ± 0.25, kCO2 = 10.4 ± 1.0,kH2O 195± 2.0, kN2O = 11.7 ± 1.2, and kH2, = 11.8±1.2. 相似文献
8.
An infrared spectroscopic study of the diatomic molecules O2, N2, NO and H2 adsorbed under different conditions on Fe2O3 has been performed.Complex patterns of absorption on both α-Fe2O3 and γ-Fe2O3 activated in O2 at high temperature are assigned to vibrations of two different chemisorbed O2 species.N2 molecules do not interact with “oxygen rich” α-Fe2O3 surfaces, but give N2O? and N2O22? species when chemisorbed on evacuated surfaces.NO molecules give complex patterns of absorption, depending on the gas pressure. Three different types of nitrate structures can be identified, as well as NO, NO? and cis-N2O2 chemisorbed species. Chemisorbed water molecules are formed by contact of H2 with Fe2O3 surfaces even at room temperature. 相似文献
9.
10.
A. I. Volkov G. G. Volkova V. K. Yermolaev L. A. Sazonov 《Reaction Kinetics and Catalysis Letters》1982,20(3-4):283-288
Radiolysis of adsorbed N2O is shown to occur due to both the dissociative capture of electrons and direct energy transfer from the excited states of alumina to N2O. One excited state ensures the decomposition of three N2O molecules.
, N2O , N2O, N2O.相似文献
11.
Iti GuptaMangalampalli Ravikanth 《Tetrahedron》2003,59(32):6131-6139
A series of meso-furyl porphyrins with four different porphyrin cores (N4, N3S, N2S2 and N3O) were synthesized and characterized. The comparison of NMR, optical and fluorescence properties of meso-furyl porphyrins with porphyrins with six-membered aryl groups indicates that electronic properties of porphyrins were changed drastically on the introduction of furyl groups at meso positions. The maximum shifts in spectral bands were observed for meso-furyl porphyrins with N2S2 core. On protonation, the absorption bands of meso-furyl porphyrins were further red shifted. All these changes were ascribed to the possibility of more planarity of the meso-furyl porphyrins due to the small size of the furyl groups which results in extending the π-delocalisation of the porphyrin ring in to the furyl groups. 相似文献
12.
The liquid—solid equilibrium temperatures in the binary systems between n-octacosane and methyl or ethyl octadecanoate are determined in order to obtain the interchange parameters between CH3 or CH2 and COO groups by means of the statistics of group interaction. 相似文献
13.
Charles W. Bauschlicher 《Chemical physics letters》1978,56(1):31-34
The abstraction reaction of methylene with hydrogen reinvestigated with a double zeta plus polarization basis at the configuration interaction level. The results are found to be very similar to those previously obtained without polarization functions, in line with previous findings at the SCF level. The barrier is computed to be 11.8 kcal/mole when an estimate of the effect of quadruple excitations is included. 相似文献
14.
15.
Yanli Zeng Qiao Sun Lingpeng Meng Shijun Zheng Dianxun Wang 《Chemical physics letters》2004,390(4-6):362-369
Mechanisms of RN3 (R=CH3, CH3CH2, (CH3)2CH, (CH3)3C) dissociations are proposed based on CAS, MP2 and B3LYP methods. The energy gaps between the ground-state reactants RN3 and the intersystem crossing (ISC) points are only a little lower than respective potential energy barriers of the spin-allowed reactions, 1RN3 → 1RN + 1N2. The ISC point, therefore, is considered as a transition state of the spin-forbidden reactions, 1RN3 → 3RN + 1N2. The methods of IRC and topological analysis of electron density are used to explain and predict the thermal dissociation pathways of the reactions studied. 相似文献
16.
Carlo Bellitto Elvira M. Bauer Alain Meerschaut Guido Righini 《Journal of solid state chemistry》2006,179(2):579-589
Fe[(CH3(CH2)2PO3)(H2O)] (1) and Fe[(CH3(CH2)17PO3)(H2O)] (2) were synthesized by reaction of FeCl2·6H2O and the relevant phosphonic acid in water in presence of urea and under inert atmosphere. The compounds were characterized by elemental and thermogravimetric analyses, UV-visible and IR spectroscopy. The crystal structure of (1) was determined from X-ray single crystal diffraction studies at room temperature: monoclinic symmetry, space group P21, , , , and β=98.62(3)°. The compound is lamellar and the structure is hybrid, made of alternating inorganic and organic layers along the c direction. The inorganic layers consist of Fe(II) ions octahedrally coordinated by five phosphonate oxygen atoms and one from the water molecule, separated by bi-layers of propyl groups. A preliminary structure characterization of compound (2) suggests a similar layered structure, but with an interlayer spacing of 40.3 Å. The magnetic properties of the compounds were both studied by a dc and ac SQUID magnetometer. Fe[(CH3(CH2)2PO3)(H2O)] (1) obeys the Curie-Weiss law at temperatures above 50 K (, ), indicating a Fe +II oxidation state, a high-spin d6 (S=2) electronic configuration and an antiferromagnetic exchange couplings between the near-neighbouring Fe(II) ions. Below , Fe[(CH3(CH2)2PO3)(H2O)] exhibits a weak ferromagnetism. The critical temperature of has been determined by ac magnetic susceptibility measurements. Compound (2) shows the same paramagnetic behaviour of the iron (II) propyl derivative. The values of C and θ were found to be and −44 K, respectively, thus suggesting the presence of Fe +II ion in the S=2 spin state and antiferromagnetic interactions between Fe(II) ions at low temperatures. Zero-field and field cooled magnetic susceptibility vs. T plots do not overlap below , suggesting the presence of an ordered magnetic state. The critical temperature, TN, has been located by the peaks at from the ac susceptibility (χ′and χ″) vs. T plots. Below TN hysteresis loops recorded in the temperature region show an S-shape, while below 15 K assume an ellipsoid form. They reveal that compound (2) is a weak ferromagnet. The critical temperature TN in these layered Fe(II) alkylphosphonates is independent of the distance between the inorganic layers. 相似文献
17.
Branko S. Jursic 《Journal of Molecular Structure》1998,430(1-3):17-22
The activation barrier for the CH4 + H → CH3 + H2 reaction was evaluated with traditional ab initio and Density Functional Theory (DFT) methods. None of the applied ab initio and DFT methods was able to reproduce the experimental activation barrier of 11.0-12.0 kcal/mol. All ab initio methods (HF, MP2, MP3, MP4, QCISD, QCISD(T), G1, G2, and G2MP2) overestimated the activation energy. The best results were obtained with the G2 and G2MP2 ab initio computational approaches. The zero-point corrected energy was 14.4 kcal mol−1. Some of the exchange DFT methods (HFB) computed energies which were similar to the highly accurate ab initio methods, while the B3LYP hybrid DFT methods underestimated the activation barrier by 3 kcal mol−1. Gradient-corrected DFT methods underestimated the barrier even more. The gradient-corrected DFT method that incorporated the PW91 correlational functional even generated a negative reaction barrier. The suitability of some computational methods for accurately predicting the potential energy surface for this hydrogen radical abstraction reaction was discussed. 相似文献
18.
V. V. Gurzhiy P. A. Mikhailenko S. V. Krivovichev I. G. Tananaev B. F. Myasoedov 《Russian Journal of General Chemistry》2012,82(1):23-26
Crystals of a new uranyl selenate complex [CH3(CH2)3NH3](H5O2)[(UO2)2(SeO4)3(H2O)] were obtained by isothermal evaporation at room temperature of its aqueous solution. The crystal structure was determined
by the X-ray diffraction analysis. The observed character of the arrangement of organic molecules in the interlayer space
confirms the concept of hydrophilic and hydrophobic zones. 相似文献
19.
S. -W. Chiu K. -C. Lau W. -K. Li N. L. Ma Y. -S. Cheung C. Y. Ng 《Journal of Molecular Structure》1999,490(1-3):109-124
Gaussian-2 ab initio calculations were performed to examine the six modes of unimolecular dissociation of cis-CH3CHSH+ (1+), trans-CH3CHSH+ (2+), and CH3SCH2+ (3+): 1+→CH3++trans-HCSH (1); 1+→CH3+trans-HCSH+ (2); 1+→CH4+HCS+ (3); 1+→H2+c-CH2CHS+ (4); 2+→H2+CH3CS+ (5); and 3+→H2+c-CH2CHS+ (6). Reactions (1) and (2) have endothermicities of 584 and 496 kJ mol−1, respectively. Loss of CH4 from 1+ (reaction (3)) proceeds through proton transfer from the S atom to the methyl group, followed by cleavage of the C–C bond. The reaction pathway has an energy barrier of 292 kJ mol−1 and a transition state with a wide spectrum of nonclassical structures. Reaction (4) has a critical energy of 296 kJ mol−1 and it also proceeds through the same proton transfer step as reaction (3), followed by elimination of H2. Formation of CH3CS+ from 2+ (reaction (5)) by loss of H2 proceeds through protonation of the methine (CH) group, followed by dissociation of the H2 moiety. Its energy barrier is 276 kJ mol−1. On both the MP2/6-31G* and QCISD/6-31G* potential-energy surfaces, the H2 1,1-elimination from 3+ (reaction (6)) proceeds via a nonclassical intermediate resembling c-CH3SCH2+ and has a critical energy of 269 kJ mol−1. 相似文献
20.
CH3NO2和CH3自由基吸氢反应途径和变分速率常数计算 总被引:1,自引:0,他引:1
采用MP2(full)/6-311G(d, p)从头算方法,优化了硝基甲烷和甲基自由基吸氢反应的过渡态结构,经QCISD(T)方法进行能量校正,得出该反应的正逆向反应的活化位垒分别是58.21 kJ•mol-1和67.17 kJ•mol-1.沿IRC分析指出该反应是氢转移协同反应,而且在反应途径上存在一个引导反应进行的振动模式,这一反应模式引导反应进行的区间在反应坐标S的-0.9~1.0(amu)1/2bohr之间;在温度为800~2600 K范围内,运用改进的变分过渡态理论(ICVT),计算了该反应的速率常数,并与实验类比所得的速率常数随温度的变化趋势进行了比较. 相似文献