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Manuscript Title: A program to evaluate vibrationally inelastic collisional cross sections of atom-diatom systems.
Authors: M.M. Novak
Program title: EDWAVE
Catalogue identifier: AAXV_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 46(1987)417
Programming language: Fortran.
Computer: DEC VAX 11/750.
Operating system: VMS.
RAM: 375K words
Word size: 32
Peripherals: disc.
Keywords: Molecular physics, Cross sections, Scattering, Elastic, Inelastic scattering, Distorted waves, Collisions, Excitation of Diatomic molecules, Relaxation, Schrodinger equation.
Classification: 16.7.

Nature of problem:
The program EDWAVE calculates the vibrationally inelastic excitation and relaxation cross sections resulting from collisions between an atom and a diatomic molecule.

Solution method:
The cross sections are obtained using the distorted wave Born approximation. As the resulting S-matrix is non-unitary, an option to apply the expotential distorted wave method is also provided. The propagation step for the wavefunctions is automatically adjusted by the program. At large separations the WKBJ approximation may be used, if required, to calculate the distorted waves. In order to simplify the evaluation of the coupling between the distorted waves, the so called distorted wave integrals, the phase-amplitude representation of the wave functions is used. The cumulative contribution at each interval leads to the A-matrix. The integral cross sections are obtained from the corresponding S-matrix, which is in turn found using the A-matrix.

The interaction potential and its derivatives must be supplied by the user. The number of vibrational channels that the program can handle is limited only by the available core memory and the allocated CPU time.

Unusual features:
Access to the NAG library is required.

Running time:
These greatly depend on the values of various parameters. As a guide, He+I2 double precision calculations with 4 active vibrational levels using the expotential distorted wave approximation require around 15 minutes on the VAX 11/750.