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Manuscript Title: A general program to calculate atomic continuum processes incorporating model potentials and the Breit-Pauli Hamiltonian within the R-matrix method.
Authors: N.S. Scott, K.T. Taylor
Program title: RMATRX RECUP
Catalogue identifier: AANT_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 25(1982)347
Programming language: Fortran.
Computer: CRAY-1.
Operating system: COS 1.09.
RAM: 242K words
Word size: 64
Peripherals: magnetic tape, disc.
Keywords: Atomic physics, Electron-atom, Scattering, Photon, Electron-ion, Photoionization, R-matrix, Spin-orbit, Pair-coupling, Intermediate coupling, Unitary transformation, Term coupling Coefficients, Coefficients of Fractional parantage, Racah coefficient.
Classification: 2.4, 2.5.

Subprograms used:
Cat Id Title Reference
AANR_v1_0 RMATRX STG1R CPC 25(1982)347
AANS_v1_0 RMATRX STG2R CPC 25(1982)347
AANU_v1_0 RMATRX RECUD CPC 25(1982)347
AANV_v1_0 RMATRX STG3R CPC 25(1982)347

Nature of problem:
This program reads Hamiltonian matrices and long range potential coefficients calculated in LS-coupling by RMATRX STG2R. Using this information it constructs matrix elements of the Breit-Pauli Hamiltonian and long-range potential coefficients in pair coupling. These quantities are stored on magnetic tape or disc files for use by RMATRX RECUD and RMATRX STG3R.

Solution method:
Hamiltonian matrices and long range potential coefficients calculated in LS-coupling by RMATRX STG2R are transformed, by means of a unitary transformation to pair-coupling. Angular integrals of the spin-orbit operator are evaluated in LSJ-coupling using Racah algebra. These are added to the spin-orbit radial integrals originally calculated in RMATRX STG2R. These matrices are then transformed by means of a unitary transformation, to pair-coupling and added to the transformed matrices from RMATRX STG2R to form matrix elements of the Breit-Pauli Hamiltonian.

Restrictions:
See subroutine SETDIM in RMATRX RECUP for details of current dimensions.

Running time:
The running time depends on the number of channels, target states and configurations included. The test run took 3 s on the CRAY-1.