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Manuscript Title: A-THREE: a general optical model code especially suited to heavy-ion calculations.
Authors: E.H. Auerbach
Program title: A-THREE
Catalogue identifier: ABII_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 15(1978)165
Programming language: Fortran.
Computer: CDC-7600.
Operating system: CDC SCOPE 2.1.
Program overlaid: yes
RAM: 21K words
Word size: 60
Peripherals: disc.
Keywords: Nuclear physics, Elastic, Schrodinger equation, Optical model, Scattering, Phase shift, Complex potential, Nuclear bound state.
Classification: 17.9.

Subprograms used:
Cat Id Title Reference
ABPC_v1_0 RCWFN CPC 8(1974)377

Nature of problem:
The non-relativistic radial Schrodinger equation with complex potential is solved partial wave by partial wave to obtain phase shifts, from which total (reaction) cross sections, elastic scattering angular distributions and polarization angular distributions are obtained. Optionally, radial wave functions may be retained. The complex optical potential may take a large number of forms and may, as well, have the parts of the potential read in (from other calculations) or calculated by user supplied subroutines. Within the same structure, bound states for a real potential may be calculated. Provision is made for search for an eigenvalue or potential which produces a given eigenvalue, in the bound state case and to fit given data or sets of data, with or without angular resolution, in the scattering case. The parameter space may also be scanned, without search.

Solution method:
The radial differential equation is integrated by the Noumerov method (with mesh refinement, if necessary); the principal search method is a variable metric minimization after Fletcher-Powell and Davidon.

Partial waves are limited to l=800 for no spin and l=400 with spin; the total number of partial waves actually computed is limited to 400, absorption for the lower uncomputed partial waves being set to 1.0. Potential specification must be made in an equally spaced grid of not over 500 intervals.

Unusual features:
All arrays requiring more significant figures than 32-bit machines allow are noted; similarly for alphanumeric words of more than four characters.