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[Licence| Download | New Version Template] acqe_v1_0.gz(15 Kbytes)
Manuscript Title: Asymptotic solution of coupled equations for electron scattering.
Authors: D.W. Norcross
Program title: ASYM
Catalogue identifier: ACQE_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 1(1969)88
Programming language: Fortran.
Computer: IBM 360/65.
Operating system: SYSTEM/360.
RAM: 22K words
Word size: 32
Keywords: Atomic physics, Electron-atom, Scattering, Photoionization, Wave, Functions, Coupled equations, Long range potentials, Asymptotic region, Wbk, Threshold.
Classification: 2.4.

Other versions:
Cat Id Title Reference
ACRK_v1_0 ASYM VERSION FOR ICL 1990 CPC 5(1973)416

Nature of problem:
The program ASYM solves coupled second-order differential equations of the type encountered in the close-coupling formulation of electron-atom (ion) scattering problems, at some specified point in the asymptotic region. Lineraly independent sets of wave functions are found which could be used as boundary solutions for a complete solution of the close-coupling integro-differential equations.

Solution method:
For a particular reaction channel and associated boundary condition, the program uses the more appropriate of two methods for determining the asymptotic solutions. One method, which involves assuming the asymptotic form for the phase of the solution and solving for the amplitude by an asymptotic series expansion, is well known and widely used. The second method, which involves assuming the first order WBK solution for the phase and interating on the amplitude, is new and was designed to replace the first in regions where it fails. Asymptotic solutions can now be obtained for the equations representing scattering near thresholds, or from highly ionized atoms.

The program is designed to work for scattering from neutral atoms or positive ions, with at least one reaction channel open. It will cope with any number of channels up through six, and long range potentials up through r**-5. These limitations on the capacity of the program can be increased easily by the user if required.

Running time:
The "worst case" running time is of order of 1.5 X N**2 seconds, where N is the number of reaction channels, and compilation time is about 45 seconds. These figures are for the IBM 360/65 at University College. When some channels are closed or there are no near-threshold channels running time is greatly reduced.