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Manuscript Title: ELSEPA-Dirac partial-wave calculation of elastic scattering of electrons and positrons by atoms, positive ions and molecules.
Authors: Francesc Salvat, Aleksander Jablonski, Cedric J. Powell
Program title: ELSEPA
Catalogue identifier: ADUS_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 165(2005)157
Programming language: FORTRAN 77.
Computer: Any computer with a FORTRAN 77 compiler.
Operating system: Windows XP, Windows 2000, Debian GNU/Linux 3.0r0 (sarge).
RAM: 0.6Mb
Word size: 32
Keywords: Dirac partial-wave analysis, electron elastic scattering, positron elastic scattering, differential cross sections, momentum transfer cross sections, transport cross sections, scattering amplitudes, spin polarization, scattering by complex potentials, highenergy atomic screening functions.
PACS: 34.80.Bm, 34.85.+x.
Classification: 2.4.

Nature of problem:
The code calculates differential cross sections, total cross sections and transport cross sections for single elastic scattering of electrons and positrons by neutral atoms, positive ions and randomly oriented molecules. For projectiles with kinetic energies less than about 5 MeV, the programs can also compute scattering amplitudes and spin polarization functions.

Solution method:
The effective interaction between the projectile and a target atom is represented by a local central potential that can optionally include an imaginary (absorptive) part to account approximately for the coupling with inelastic channels. For projectiles with kinetic energy less than about 5 MeV, the code performs a conventional relativistic Dirac partial-wave analysis. For higher kinetic energies, where the convergence of the partial-wave series is too slow, approximate factorization methods are used.

The calculations are based on the static-field approximation. The optional correlation-polarization and inelastic absorption corrections are obtained from approximate, semiempirical models. Calculations for molecules are based on a single-scattering independent-atom approximation. To ensure accuracy of the results for scattering by ions, the electron density of the ion must be supplied by the user.

Unusual features:
The program calculates elastic cross sections for electrons and positrons with kinetic energies in a wide range, from a few tens of eV up to about 1 GeV. Calculations can be performed for neutral atoms of all elements, from hydrogen to lawrencium (Z = 1 - 103), ions and simple molecules.

Running time:
On a 2.8 GHz Pentium 4, the calculation of elastic scattering by atoms and ions takes between a few seconds and about two minutes, depending on the atomic number of the target, the adopted potential model and the kinetic energy of the projectile.