State-to-state quantum dynamics calculations of the C + OH reaction on the second excited potential energy surface

Accurate three-dimensional quantum-mechanical scattering calculations using a time-indepedent hyperspherical method have been performed for the C((3)P) + OH(X(2)Π) → CO(a(3)Π) + H((2)S) reaction on the second excited potential energy surface of 1(4)A″ symmetry. State-to-state reaction probabilities at a total angular momentum J = 0 have been computed in a wide range of collision energies. Many pronounced resonances have been found, espcially at low energy. The product vibrational distributions are noninverted. The present results therefore suggest that the title reaction proceeds via a long-lived intermediate complex. An approximate quantum-mechanical rate constant has also been calculated, and large differences are observed with the quasi-classical trajectory prediction.     

Accurate time dependent wave packet calculations for the N + OH reaction

We present accurate quantum calculations of state-to-state cross sections for the N + OH → NO + H reaction performed on the ground (3)A' global adiabatic potential energy surface of Guadagnini et al. [J. Chem. Phys. 102, 774 (1995)]. The OH reagent is initially considered in the rovibrational state ν = 0, j = 0 and wave packet calculations have been performed for selected total angular momentum, J = 0, 10, 20, 30, 40,...,120. Converged integral state-to-state cross sections are obtained up to a collision energy of 0.5 eV, considering a maximum number of eight helicity components, Ω = 0,...,7. Reaction probabilities for J = 0 obtained as a function of collision energy, using the wave packet method, are compared with the recently published time-independent quantum mechanical one. Total reaction cross sections, state-specific rate constants, opacity functions, and product state-resolved integral cross-sections have been obtained by means of the wave packet method for several collision energies and compared with recent quasi-classical trajectory results obtained with the same potential energy surface. The rate constant for OH(ν = 0, j = 0) is in good agreement with the previous theoretical values, but in disagreement with the experimental data, except at 300 K.     

Quasi-classical trajectory study of the S + OH → SO + H reaction: from reaction probability to thermal rate constant

First quasi-classical trajectory calculations have been carried out for the S((3)P) + OH(X?(2)Π) → SO(X?(3)Σ(-)) + H((2)S) reaction on an ab initio global potential energy surface for the ground electronic state, X?(2)A', of HSO. Cross sections, computed for collision energies up to 1 eV, show no energy threshold and decrease with the increasing collision energy. Rate constants have been calculated in the 5-500 K temperature range. The thermal rate constant is in good agreement with approximate quantum results, while a disagreement is found at 298 K with the experimental data. Product energy distributions have also been reported at four collision energies from 0.001 to 0.5 eV. The shapes of the rovibrational and angular distributions suggest the formation of an intermediate complex that is more and more long-lived as the collision energy increases.     

An accurate study of the dynamics of the C+OH reaction on the second excited 1(4)A" potential energy surface

The dynamics of the C((3)P)+OH(X(2)Π) → CO(a(3)Π)+H((2)S) on its second excited potential energy surface, 1(4)A", have been investigated in detail by means of an accurate quantum mechanical (QM) time-dependent wave packet (TDWP) approach. Reaction probabilities for values of the total angular momentum J up to 50 are calculated and integral cross sections for a collision energy range which extends up to 0.1 eV are shown. The comparison with quasi-classical trajectory (QCT) and statistical methods reveals the important role played by the double well structure existing in the potential energy surface. The TDWP differential cross sections exhibit a forward-backward symmetry which could be interpreted as indicative of a complex-forming mechanism governing the dynamics of the process. The QM statistical method employed in this study, however, is not capable to reproduce the main features of the possible insertion nature in the reactive collision. The ability to stop individual trajectories selectively at specific locations inside the potential energy surface makes the QCT version of the statistical approach a better option to understand the overall dynamics of the process.     

Synthesis and characterization of nanosized NiO2 and NiO using Triton® X-100

Nanosized NiO₂ particles with an average diameter of 15 nm are prepared by treating of Ni(NO₃)₂ · 6H₂O with an aqueous solution of KClO in the presence of Triton® X-100. This black fine powder of nickel peroxide was characterized by XRD diffraction, energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The as-prepared NiO₂ can be easily transformed to nanosized NiO merely by washing it with acetone. The obtained NiO has an average diameter of 40 nm and was characterized by the same means used for NiO₂. The nanoparticles of NiO₂ and NiO were obtained in high yields and purities.      

Rapid chemical synthesis of four ferrate(VI) compounds

The preparation of four novel Fe(VI) salts, including PbFeO₄, ZnFeO₄, CdFeO₄ and HgFeO₄ is demonstrated. These Fe(VI) salts were synthesized from a solid phase reaction merely by grinding K₂FeO₄ with M (C₂H₃O₂)₂.nH₂O (M = Pb²⁺, Zn²⁺) or M (NO₃)₂.nH₂O (M = Cd²⁺, Hg²⁺) at room temperature. A rapid and efficient reaction occurred upon grinding the solid reactants to afford high yield ferrate(VI) salts which were characterized by XRD, EDS and FTIR techniques. All of the synthesized ferrates were rather stable and could be stored at room temperature for more than a month with no significant decomposition.     

Ortho-para H₂ conversion by proton exchange at low temperature: an accurate quantum mechanical study

We report extensive, accurate fully quantum, time-independent calculations of cross sections at low collision energies, and rate coefficients at low temperatures for the H? + H?(v = 0, j) → H? + H?(v = 0, j') reaction. Different transitions are considered, especially the ortho-para conversion (j = 1 → j' = 0) which is of key importance in astrophysics. This conversion process appears to be very efficient and dominant at low temperature, with a rate coefficient of 4.15 × 10?1? cm3 molecule?1 s?1 at 10 K. The quantum mechanical results are also compared with statistical quantum predictions and the reaction is found to be statistical in the low temperature regime (T < 100 K).     

Quasiclassical trajectory scattering calculations for the OH + O → H + O2 reaction: Cross sections and rate constants

We report quasiclassical trajectory studies of the OH + O → H + O₂ reaction using a recently developed ab initio potential energy surface for the ground electronic state of HO₂. The total reaction probability is in good agreement with the quantum result. Integral cross sections show no energy threshold and decrease as the collision energy increases. Rate constants have been calculated in the (1–500 K) temperature range. They exhibit a negative temperature dependence for temperatures above 50 K, and the thermal rate constant is in quantitative agreement with the most recent experimental data. The reactivity is slightly enhanced by rotational excitation of OH.     

Influence of ro-vibrational and isotope effects on the dynamics of the C(3 P)+ OD(X 2Π) → CO(X 1 Σ+) + D(2 S) reaction

The C(³ P)+OD(X ²Π) reaction has been studied by means of quantum mechanical real wave packet (RWP) and quasiclassical trajectory (QCT) methodologies on the ground potential energy surface of Zanchet et al. [J. Phys. Chem. A 110, 12017 (2006)]. Initial state selected total reaction probabilities at J?=?0 total angular momentum have been calculated for a wide range of collision energies. Product state-resolved integral cross-sections at selected collision energies and excitation functions have been determined from the RWP calculations using the J-shifting approximation and from QCT calculations. State-specific and thermal rate coefficients have been calculated using both methodologies up to 500 K. The effect of reagent rotational excitation on the dynamics for the C(³ P)+OH(X ²Π) and C(³ P)+OD(X ²Π) reactions has been investigated and interesting discrepancies between the QCT and RWP results have been found. The RWP results are found to be in an overall good agreement with the corresponding QCT results, although the QCT integral cross-section and rate coefficients are slightly smaller than those obtained from the RWP calculations.