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Manuscript Title: Intermediate coupling collision strengths from LS coupled R-matrix elements.
Authors: R.E.H. Clark
Program title: LSTOIC
Catalogue identifier: AAKY_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 16(1978)119
Programming language: Fortran.
Computer: IBM 370/168.
Operating system: OS/360.
RAM: 70K words
Word size: 32
Keywords: Atomic physics, Electron-atom, Scattering, Fine structure Transition, Intermediate coupling, Ls coupling, Collision strength, Mixing coefficient, R-matrix, Wigner coefficient, Configuration mixing.
Classification: 2.4.

Nature of problem:
Fine structure collision strengths for transitions between two groups of states in intermediate coupling and with inclusion of configuration mixing are obtained from LS coupled reactance matrix elements (R-matrix elements) and a set of mixing coefficients.

Solution method:
The LS coupled R-matrix elements are transformed to pair coupling, using Wigner 6-j coefficients. From these pair coupled R-matrix elements together with a set of mixing coefficients, R-matrix elements are obtained which include the intermediate coupling and configuration mixing effects. Finally, from the latter R-matrix elements, collision strengths for fine structure transitions are computed (with inclusion of both intermediate coupling and configuration mixing).

Restrictions:
Array lengths may be adjusted to suit the user's needs and the available core storage. Only one Ja and J'a value may be computed at a time.

Unusual features:
LS coupled collision strengths for transitions between energy terms are computed as a check on input R-matrix data. The program also computes LS coupled collision strengths for transitions between fine structure levels to be compared with the calculated fine structure collision strengths which include both intermediate coupling and configuration mixing. It can do this from either pure configuration LS coupled R-matrix elements so that configuration mixing need not have been done separately, or it can instead use as input LS coupled R-matrix elements which already include configuration mixing. Of course, the set of mixing coefficients required as input in obtaining the final results for collision strengths for fine structure transitions with inclusion of both intermediate coupling and configuration mixing are different in the two cases. Users are warned that arrays with more than three dimensions occur in the program.

Running time:
The sample data comprising one energy, 2 initial states, 2 final states and 12 intermediate states took 16 s of computer system time of which 5 s was actual execution time.