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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.

Restrictions:
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.