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Manuscript Title: Fractional parentage coefficients for equivalent p shell and equivalent d shell electrons.
Authors: D.C.S. Allison
Program title: P SHELL C.F.P.
Catalogue identifier: ACQB_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 1(1969)15
Programming language: Fortran.
Computer: ICL 1907, 1900 SERIES.
Operating system: QUBE.
RAM: 3K words
Word size: 24
Keywords: General purpose, Rotation group, Racah c.f.p..
Classification: 4.1.

Nature of problem:
The subroutine CFPP evaluates the Racah coefficient of fractional parentage for equivalent p shell electrons.

Solution method:
Since any state of a p**n multiplet may be completely specified by the two quantum numbers L and S, it is possible to set up two two- dimensional arrays Lij and Sij, where the subscript i refers to the number of electrons and the subscript j refers to a label which denotes a particular allowed combination of L and S values. If the state in question is identified by the labels n and j1 then its parent state can be identified by the labels (n-1) and j2 where j2 j2 refers to a particular allowed combination of L and S values for the p**n-1 configuration. The labels n, j1 and j2 may then be used to define a unique element of a table Tn(j1,j2) where n refers to a particular table, j1 to a row index and j2 to a column index. This is the required fractional parentage coefficient.

Unusual features:
If the state in question or its parent state is forbidden on account of an incorrect combination of L and S values then an erroneous value (in practice 9.9) is given to the fractional parentage coefficient. This may be replaced by an error statement if required. The program CFPP shares its long write-up with CFPD, a similar program for d shell coefficients of fractional parentage.

Running time:
<<1 second for one fractional parentage coefficient.