A detailed comparison of centrifugal sudden and J-shift estimates of the reactive properties of the N + N2 reaction

Abstract

An extended comparison of the reactive properties of the N + N(2) exchange reaction calculated on a non-collinear dominant potential energy surface using both a centrifugal sudden and a J-shift quantum method is reported. The choice of carrying out such an investigation for N + N(2) is motivated by the fact that the best available (and currently used for spacecraft re-entry simulations) computed set of kinetic data has been worked out using the low level J-shift approximation though based on exact quantum zero total angular momentum probabilities. The fact that our investigation is carried out for a heavy system and a potential energy surface free of wells in the strong interaction region minimizes the occurrence of tunnel, resonance and interference effects which would make the rationalization of the result difficult and the centrifugal sudden treatment less accurate. The study has provided evidence of two important limits of the J-shift approximation: the wrong determination of the maximum value of the total angular momentum quantum number J contributing to reactivity and the lack of deformation of the partial reactive probability dependence on energy at fixed J value. Accordingly, it has been found that the J-shift state-specific cross sections underestimate the corresponding CS values when the initial diatomic rotational energy is low while the situation reverses when the initial diatomic rotational energy is high.

An innovative computational comparison of exact and centrifugal sudden quantum properties of the N + N2reaction

“…12,16,[20][21][22][23][24][25][26][27][28][29] In contrast, no exact (that will be better defined later) quantum calculations have been yet performed. As a matter of fact, results published up to now in the literature are either of reduced dimensionality 16,[30][31][32] or limited to zero total angular momentum (J) 17,[33][34][35][36][37][38][39][40][41] from which thermal rate coefficients 17,[35][36][37] and state-specific cross sections 38 have been estimated by applying the J-shift approximation 49,50 (with J being the J quantum number). Other work was devoted to compare the J-shift estimates of the cross section with the CS (Centrifugal Sudden) 51,52 reduced dimensionality estimates.…”

“…Other work was devoted to compare the J-shift estimates of the cross section with the CS (Centrifugal Sudden) 51,52 reduced dimensionality estimates. 38 Further comparison with measured thermal rate coefficients was also performed using SemiClassical-Initial Value Representation and quantum Multi-Configurational Time-Dependent Hartree techniques. [42][43][44] Only in recent years the assemblage of the European Grid Infrastructure (EGI) 53 platform and the support provided by EGI to the Virtual Organization COMPCHEM 54,55 have made it possible to design and implement the so called Grid Empowered Molecular Simulator (GEMS) [56][57][58][59][60] that does not only allow to bridge High Performance Computing (HPC) with High Throughput Computing (HTC) but it does also enable the execution of highly concurrent parameter studiesw by dramatically cutting down the computing timez needed for the calculations.…”

“…More details about the application of the CS approximation to the N + N 2 system can be found in ref. 38.…”

On the Angular Distribution of the H+Li2 Cross Sections: a Converged Time-Independent Quantum Scattering Study

“…This way, we are able to compute the differential cross sections 37 :and the integral cross sections 38 :where E col stands for the collision energy, for the reactant reduced mass and for the Wigner small d-matrix elements.…”

Thermochemical Calculations Using Serviceoriented Architecture in the Web Service Form

“…Web services herein are used for the allocation of computing capacity. Quantum reactive scattering studies of atom-diatom systems have nowadays become routine computing applications when you need to either confirm the associated potential surface energy or to accurately estimate the effectiveness of the reactive system [43].…”