Coupled channel calculations and computer code ECIS

The code ECIS has been developed to study polarization effects in inelastic proton scattering around 20MeV. It takes into account spin-orbit deformation which has large effects on the inelastic analyzing powers. The version ECIS79 was presented at the workshop on Nuclear Model Computer Codes in January 1984 at Trieste. Since then, it has been extended to include compound nucleus features which were described at that workshop by Peter Moldauer (code ANLECIS) and also the Dirac phenomenology which has been used down to 20MeV proton scattering. The code uses an iteration procedure which will be described in details because it is not secure. The convergence of results can be obtained with Pade approximants but there is some numerical limit which must be understood. This iteration procedure is necessary with pin- orbit deformation. We shall give some information on the integration methods in order to show how to check the precision of the results and on automatic search methods on the parameters. ECIS79 was also used for heavy ion scattering and included a special method to deal with long range contributions of the Coulomb interaction. This method is used in the Dirac phenomenology, where such problems arise even for neutron scattering if the tensor coupling of the magnetic moment with the Coulomb field is taken into account. In the Schrodinger phenomenology, to which we shall restrict ourselves, such problems arise from the Mott- Schwinger interaction (Coulomb spin-orbit), necessary to describe the polarization in elastic neutron scattering. The method described had to be revised for neutron scattering and for Dirac phenomenology. In this paper, the authors describe briefly its use and also the use of compound nucleus. There are two versions of the code: a single precision one for CDC or CRAY computers and a mixed single-double precision one for IBM, UNIVAC, VAX, PIRME, CONVEX, or GOULD computer