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391.
Pomerantz AE Camden JP Chiou AS Ausfelder F Chawla N Hase WL Zare RN 《Journal of the American Chemical Society》2005,127(47):16368-16369
The importance of reactive trajectories straying far from the minimum energy path is demonstrated for the bimolecular reaction H + HBr --> H2(v', j') + Br at 53 kcal/mol collision energy. Product quantum state distributions are measured and calculated using the quasi-classical trajectory technique, and the calculations indicate that highly internally excited H2 products result from indirect reactive trajectories with bent transition states. A general argument is made suggesting that reaction products with internal energy exceeding a kinematic constraint can, in general, be attributed to reactive collisions straying far from the minimum energy path. 相似文献
392.
A pulsed beam of metastable atoms traverses a scattering chamber filled with oxidant gas at low pressures (beam + gas arrangement); the resulting chemiluminescence is spectroscopically resolved as a function of time to yield a time-of-flight (TOF) spectrum for different internal states. From this data, the initial relative translational energy distribution is derived for the reactants that populate the excited internal state observed. Lower bounds are placed on the barium halide (BaX) dissociation energies, using the reactions Ba(3D) + X2 → BaX* + X, where X = Br, I. Arguments are presented to show that these lower bounds represent measurements of the true bond energies: it is concluded that D00(BaBr) = 85.8 ± 2 kcal/mole and D00(BaI) = 72.9 ± 2 kcal/mole. The present work corrects previous determinations of bond energies from single-collision chemiluminescent studies which were in error because of unrecognized metastable contamination in the high-temperature atomic beam. 相似文献
393.
In order to study the radiative properties of the isolated benzophenone molecule, a molecular beam of benzophenone is excited by a pulsed nitrogen laser or a pulsed tunable dye laser and the subsequent emission intensity is measured as a function of time. We find the decay to be exponential with a lifetime of about O.5μs. This value is shorter than the radiative lifetime calculated from absorption measurements. As the background pressure in the molecular beam chamber is raised from 10?6 torr to 10?4 torr, the decay of the emission lengthens and becomes biexponential. An explanation involving giant self-collision-induced cross sections for intersystem crossing is advanced to reconcile these observations with results from previous studies of benzophenone emission decay. 相似文献
394.
A very stable electroactive film of catechin was electrochemically deposited on the surface of activated glassy carbon electrode.
The electrochemical behavior of catechin modified glassy carbon electrode (CMGCE) was extensively studied using cyclic voltammetry.
The properties of the electrodeposited films, during preparation under different conditions, and the stability of the deposited
film were examined. The charge transfer coefficient (α) and charge transfer rate constant (k
s) for catechin deposited film were calculated. It was found that the modified electrode exhibited excellent electrocatalytic
activity toward hydrazine oxidation and it also showed a very large decrease in the overpotential for the oxidation of hydrazine.
The CMGCE was employed to study electrocatalytic oxidation of hydrazine using cyclic voltammetry, rotating disk voltammetry,
chronoamperometry, amperometry and square-wave voltammetry as diagnostic techniques. The catalytic rate constant of the modified
electrode for the oxidation of hydrazine was determined by cyclic voltammetry, chronoamperometry and rotating disk voltammetry
and was found to be around 10−3 cm s−1 . In the used different voltammetric methods, the plot of the electrocatalytic current versus hydrazine concentration is
constituted of two linear segments with different ranges of hydrazine concentration. Furthermore, amperometry in stirred solution
exhibits a detection limit of 0.165 μM and the precision of 4.7% for replicate measurements of 40.0 μM solution of hydrazine. 相似文献
395.
The spectra of vibrationally excited nf Rydberg states of nitric oxide were recorded by monitoring the photoion current produced using two-photon double resonance excitation via the NO A (2)Sigma(+) state followed by photoexcitation of the Rydberg state that undergoes autoionization. The optical transition intensities from NO A state to nf Rydberg states were calculated, and the results agree closely with experiment. These results combined with circular dichroism measurements allow us to assign rotational quantum numbers to the nf Rydberg states even in a spectrum of relatively low resolution. We report the positions of these nf (upsilon,N,N(c)) Rydberg levels converging to the NO X (1)Sigma(+) upsilon(+) = 1 and 2 ionization limits where N is the total angular momentum excluding electron and nuclear spin and N(c) represents the rotational quantum number of the ion core. Our two-color optical-optical double resonance measurements cover the range of N from 15 to 28, N(c) from 14 to 29, and the principal quantum number n from 9 to 21. The electrostatic interaction between the Rydberg electron and the ion core is used to account for the rotational fine structure and a corresponding model is used to fit the energy levels to obtain the quadrupole moment and polarizability of the NO(+) core. Comparison with a multichannel quantum defect theory fit to the same data confirms that the model we use for the electrostatic interaction between the nf Rydberg electron and the ion core of NO well describes the rotational fine structure. 相似文献
396.
397.
R. Karimi Shervedani H. R. Zare Mehrdjardi S. H. Kazemi Ghahfarokhi 《Journal of the Iranian Chemical Society》2007,4(2):221-228
Electrochemical characterization and application of nickel ruthenium dioxide (Ni-RuO2) as a pH sensor for the determination of petroleum oil acid number is described. The sensor consists of RuCl3 thermally decomposed onto the upper side of a polycrystalline nickel electrode at 400 °C in an open furnace. The advantages of the sensor are: (i) easy preparation, (ii) fast response in a large pH range, (iii) high physical and chemical stability, and (iv) excellent reproducibility as determined by the reproducible linear variation of charge transfer resistance (Rct) as a function of overpotential (η) obtained by electrochemical impedance spectroscopy (EIS), and the Nernstian slope of the electrode potential in a wide range of pH (1.5–12.5) obtained by potentiometric measurements. The potentiometric selectivity coefficients of the sensor toward some anions and cations were evaluated in aqueous solution. The characterized Ni-RuO2 pH sensor was successfully tested for the determination of petroleum oil acid number. 相似文献
398.
Mohammad Yazdanbakhsh Dr. M. H. Alizadeh H. Zare Khorramdel W. Frank 《无机化学与普通化学杂志》2007,633(8):1193-1198
Three new oxo‐centered trinuclear mixed‐bridged carboxylate complexes with terminal unsaturated ligands ([M2M′(μ3‐O)(μ‐O2C3H3)5(μ‐O4C6H7)(O2C3H3) (H2O)2]·2H2O [M = Fe, M′ = Fe ( 1 ); M = Fe, M′ = Cr ( 2 ); M = Cr, M′ = Fe ( 3 )]) have been synthesized and characterized by means of elemental analyses, IR spectra and crystal structure analyses. The compounds crystallize isotypically in the orthorhombic space group type Pbcn with a = 24.622(3) Å, b = 16.304(2) Å, c = 17.491(2) Å, V = 7021.5(15) Å3 ( 1 ), a = 24.708(5) Å, b = 16.290(2) Å, c = 17.394(2) Å, V = 7001.0(18) Å3 ( 2 ), a = 24.611(4) Å, b = 16.300(3) Å, c = 17.359(3) Å, V = 6964(2) Å3 ( 3 ), and Z = 8. The infrared spectra show resolved bands arising from νasym(OCO) and νsym(OCO) vibrations of monodentate and bridging carboxylate ligands along with those of νasym(M2M′O) vibrations in the complexes. 相似文献
399.
A. Hasaninejad A. Zare M. R. Mohammadizadeh Z. Karami 《Journal of the Iranian Chemical Society》2009,6(1):153-158
Ammonium heptamolybdate tetrahydrate [(NH4)6Mo7O24.4H2O] efficiently catalyzes the condensation of aryl-1,2-diamines with 1,2-diketones in EtOH/H2O as a green media at room temperature to afford quinoxaline derivatives as biologically interesting compounds. Ease of recycling of the catalyst is one of the most advantages of the proposed method. 相似文献
400.
A new sulfate-selective electrode based on the complex N,N'-bis(2-amino-1-oxo-phenelenyl)phenylenediamine copper(II) (CuL) as the membrane carrier was developed. The electrode exhibited a good Nernstian slope of -29.5 +/- 0.5 mV/decade and a linear range of 1.0 x 10(-7) - 1.0 x 10(-1) M for sulfate. The limit of detection was 1.0 x 10(-8) M. It has a fast response time of 10 s and can be used for more than three months. The selective coefficients were determined by the fixed interference method (FIM). The electrode could be used in the pH range 3.5 - 8.0. It was employed as an indicator electrode for direct determination of sulfate in pharmacy and cement samples. 相似文献