Numerical Regge pole analysis of resonance structures in elastic, inelastic and reactive state-to-state integral cross sections

Abstract

We present a detailed description of a FORTRAN code for evaluation of the resonance contribution a Regge trajectory makes to the integral state-to-state cross section (ICS) within a specified range of energies. The contribution is evaluated with the help of the Mulholland formula (Macek et al., 2004) and its variants (Sokolovski et al., 2007; Sokolovski and Akhmatskaya, 2011). Regge pole positions and residues are obtained by analytically continuing S-matrix element, evaluated numerically for the physical values of the total angular momentum, into the complex angular momentum plane using the PADE_II program (Sokolovski et al., 2011). The code decomposes an elastic, inelastic, or reactive ICS into a structured, resonance, and a smooth, ‘direct’, components, and attributes observed resonance structure to resonance Regge trajectories. The package has been successfully tested on various models, as well as the F+H2→HF+H benchmark reaction. Several detailed examples are given in the text. Program summaryProgram title: ICS ReggeCatalogue identifier: AEST_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEST_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 71962No. of bytes in distributed program, including test data, etc.: 1405035Distribution format: tar.gzProgramming language: FORTRAN 90.Computer: Any computer equipped with a FORTRAN 90 compiler.Operating system: UNIX, LINUX.RAM: 256 MbClassification: 16.8.External routines: MPFUN (http://crd-legacy.lbl.gov/~dhbailey/mpdist/), QUADPACK http://www.netlib.org/quadpack/ (included in the distribution file)Subprograms used:Cat IdTitleReferenceAEHO_v1_0PADE IICPC 182 (2011) 448Nature of problem:The package extracts the positions and residues of resonance poles from numerical scattering data supplied by the user. This information is then used for the analysis of resonance structures observed in elastic, inelastic and reactive integral cross sections.Solution method:The S-matrix element is analytically continued in the complex plane of either energy or angular momentum with the help of Padé approximation of type II. Resonance Regge trajectories are identified and their contributions to the integral cross section are evaluated.Unusual features:Use of multiple precision MPFUN package.Additional comments:The following are included in the distribution file: PADE II, MPFUN and QUADPACK packages, validation suites, script files, input files, readme files, Installation and User GuideRunning time:From several minutes to hours depending on the number of energies involved, the precision level chosen and the number of iterations performed.