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Manuscript Title: IMPACT: a program for the solution of the coupled integro- differential equations of electron-atom collision theory.
Authors: M.A. Crees, M.J. Seaton, P.M.H. Wilson
Program title: IMPACT
Catalogue identifier: ACYE_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 15(1978)23
Programming language: Fortran.
Computer: CDC 7600.
Operating system: SCOPE 2.1.4.
Program overlaid: yes
RAM: 20K words
Word size: 60
Peripherals: disc.
Keywords: Atomic physics, Electron-atom, Electron-ion, Scattering.
Classification: 2.4.

Subprograms used:
Cat Id Title Reference
ACYF_v1_0 IMPPRO CPC 15(1978)23

Other versions:
Cat Id Title Reference
ACZK_v1_0 ECSIMPACT CPC 18(1979)287

Nature of problem:
It is required to obtain approximate solutions of the Schroedinger equation (H-E)Psi=0 where Psi is the wave function for a system containing (M+1)-electrons and a nucleus of charge z. Using a variational principle, one obtains a system of coupled integro- differential (ID) equations for the radial functions F(r) and coefficients c. IMPACT is a computer program for the solution of these equations. Put E = ELOW + EKLSQ where ELOW is the energy for the ground state of the M electron system and EKLSQ is input to the program. For EKLSQ less than 0, IMPACT obtains approximate solutions of the Schroedinger equation for the bound state Psin of the (M+1) electron system with energy EN closest to ELOW + EKLSQ. For EKLSQ greater than 0, IMPACT solves the corresponding electron-atom or electron-ion collision problem.

Solution method:
The radial functions Fi(r) are tabulated at points r = R(1), R(2), ..., R(N), and matched to functions for r> R(N) obtained using a modified version of the program ASYM of Norcross. Using numerical methods, the ID equations are replaced by linear algebraic (LA) equations which are solved using standard techniques.

The program IMPACT is provided in a form which must be pre-processed by a program IMPPRO, which inserts dimensions. Restrictions on the complexity of the problems which can be solved are determined entirely by available machine time and core store.