Numerical Regge pole analysis of resonance structures in state-to-state reactive differential cross sections

TL;DR

This paper presents a FORTRAN code for complex angular momentum analysis of resonance effects in reactive differential cross sections, enabling detailed interpretation of atom-diatom reaction scattering data.

Contribution

It provides a detailed description of a numerical code for Regge pole analysis of resonance structures in reactive scattering, extending previous methods with practical implementation details.

Findings

Successfully tested on model systems and benchmark reactions.

Allows evaluation of Regge trajectory contributions to differential cross sections.

Enables detailed analysis of resonance effects in atom-diatom reactions.

Abstract

This is the third (and the last) code in a collection of three programs [Sokolovski et al (2011), Akhmatskaya et al (2014)] dedicated to the analysis of numerical data, obtained in an accurate simulation of an atom-diatom chemical reaction. Our purpose is to provide a detailed description of a FORTRAN code for complex angular momentum (CAM) analysis of the resonance effects in reactive angular scattering [for CAM analysis of integral reactive cross sections see [Akhmatskaya et al (2014)]. The code evaluates the contributions of a Regge trajectory (or trajectories) to a differential cross section in a specified range of energies. The contribution is computed with the help of the methods described in [Dobbyn et al (2007), Sokolovski and Msezane (2004), Sokolovski et al (2007)]. Regge pole positions and residues are obtained by analytically continuing S-matrix element, calculated numerically for the physical integer values of the total angular momentum, into the complex angular momentum plane using the PADE II program [Sokolovski et al (2011)]. The code represents a reactive scattering amplitude as a sum of the components corresponding to a rapid "direct" exchange of the atom, and the various scenarios in which the reactants form long-lived intermediate complexes, able to complete several rotations before breaking up into products. The package has been successfully tested on the representative models, as well as the F + H2->HF+H benchmark reaction. Several detailed examples are given in the text. PACS:34.50.Lf,34.50.Pi