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Manuscript Title: The multichannel eikonal theory program for electron-atom scattering.
Authors: E.J. Mansky, M.R. Flannery
Program title: MET_cross
Catalogue identifier: ADAW_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 88(1995)249
Programming language: Fortran.
Computer: IBM RS/6000 model 520.
Operating system: AIX 3.1.7, HP-UX 8.07, 9.01.
RAM: 14K words
Word size: 32
Peripherals: disc.
Keywords: Atomic physics, Scattering, Electron-atom, Hamilton-jacobi equation, Schrodinger's equation, Semiclassical, Partial Differential equations, Inelastic Cross sections.
Classification: 2.4.

Nature of problem:
Calculation of the complex scattering amplitudes, differential and integral cross sections for the elastic and inelastic scattering of electrons by atoms in the intermediate to high energy regime. In addition, a characterization of the orientation and alignment of the atomic charge clouds via calculation of the coherence and correlation parameters.

Solution method:
The semiclassical multichannel eikonal theory (MET) [1,2] is used to solve the Schrodinger equation describing the electron-atom scattering using an impact-parameter representation for the system wavefunction, for the complex amplitude functions. In the present paper the design of the algorithm used to implement the MET, for the case of straight-line trajectories and electron exchange neglected is described. The resulting set of Hamilton-Jacobi coupled partial differential equations for the amplitude functions is solved using the rational extrapolation technique of Bulirsch and Stoer [3]. Evaluation of the complex scattering amplitudes, differential and integral cross sections for each of the states in the basis set is then achieved by Gaussian quadrature.

Restrictions:
At present the MET code is limited to a maximum of 10 states in the basis set and 1600 points in the z-integration of the coupled Hamilton- Jacobi equations. Furthermore, the maximum number of impact parameters rho and electron scattering angles theta which can be considered is 250 and 126, respectively. All of the above limits are easily changed by adjusting the appropriate array lengths in the PARAMETER statements in the code (see instructions in the comment cards for details).

Running time:
1-3 CPU hours (depending on the energy)

References:
[1] M.R. Flannery and K.J. McCann, J. Phys. B: At. Mol. Phys. 7(1974).
[2] E.J. Mansky and M.R. Flannery, J. Phys. B: At. Mol. Opt. Phys. 23(1990)4549, 4573.
[3] R. Bulirsch and J. Stoer, Num. Math. 8(1966)1.