Narrow Results

The statistical moment method has been used to study the effect of isotopic mass difference on extended X-ray absorption fine structure (EXAFS) Debye–Waller factor of crystalline germanium. The effects on the parallel mean-square relative displacement and the atomic mean square displacements have been considered. This research also exposed that isotopic effect is noticeable where the correlated atomic motion is concerned. Numerical calculations have been performed for two isotopes ⁷⁰Ge and ⁷⁶Ge in range of temperature from 0 K to 600 K. Our results are compared with available experimental EXAFS data [J. Purans et al., Phys. Rev. Lett.100 (2008) 055901] as well as with lattice dynamics calculations [A. Sanson, Solid State Sci.12 (2010) 1988] and the good agreements are found.

We present reaction probabilities, branching ratios and vibrational product quantum state distributions for the reaction O(¹D)+HCl → OH+Cl (OCl+H), Boltzmann averaged over initial rotational quantum states at a temperature of 300 K and also for the deuterium isotopic variant. The quantum scattering dynamics are performed using the potential energy surfaces for all three contributing electronic states. Comparisons are presented with results computed using only the ground electronic state potential energy surface, with results computed using only the j = 0 initial rotational state and also with results obtained using an equal weighting for the lowest 10 rotational states. Inclusion of the higher initial rotational states significantly changes the form of the reaction probability as a function of collision energy, reducing the threshold for reaction on the 1A" and 2A' excited electronic states. We found that the combined inclusion of higher initial rotational states and all three contributing electronic states is crucial for obtaining a branching ratio that is within the range and trend given by experiment from our J = 0 calculations. Isotopic effects range from tunnelling effects for the hydrogen variant and enhancement of reactivity for the production of OD on the excited electronic states.

Quasi-Classical Trajectory (QCT) calculations have been carried out to study the stereodynamics of the reactions N + NH → N₂ + H and isotopic effects on the product polarization at collision energies of 10.0 kcal/mol and 25.0 kcal/mol which proceed on the Double-Many-Body-Expansion (DMBE) potential energy surface. The distribution of dihedral angle P(ϕ_r), and the distribution of angle between k and j′, P(θ_r) are discussed in detail. Furthermore, four generalized polarization dependent differential cross sections (PDDCSs) (2π/σ)(dσ₀₀/dω), (2π/σ)(dσ₂₀/dω), (2π/;σ)(dσ₂₂₊/dω), and (2π/σ)(dσ_{21 -}∕dω) are presented. The results reveal that isotope effect plays an important role for P(ϕ_r) and P(θ_r) distribution, and the PDDCSs exhibit similar collision energy dependency relationship at low and high collision energies.