Reference configuration permutational symmetry

It has been demonstrated that a given electronic configuration can yield several space- and spin- adapted determinental wavefunctions such functions are referred to as configuration state functions (CSFs). These CSF wavefunctions are not the exact eigenfunctions of the many-electron Hamiltonian, H they are simply functions which possess the space, spin, and permutational symmetry of the exact eigenstates. As such, they comprise an acceptable set of functions to use in, for example, a linear variational treatment of the true states. 

The n.m.r. spectra of (71) and (72) show no changes in the temperature range +30° to +100°, at which point irreversible decomposition of the molecules become apparent. The n.m.r. data of these and of related phosphoranes are summarized in Table 15. The syntheses of (47) and of (64) were described above.111,114 Their variable temperature proton n.m.r. will be discussed in the appropriate sections corresponding to the symmetry properties of the molecule. Note, for further reference, the Permutational Description- " of the energetically preferred isomer (47-(l 5)) of the 1,4,2-dioxaphospholane with the cis-H/H configuration, made from the reaction of trimethyl phosphite with pentafluoro-benzaldehyde. 

In the case of permutation isomers with some indistinguishable ligands and/or with skeletal symmetry there are different but equivalent ligand permutations leading to the reference isomer of the configuration. Among the numerically ordered equivalent ligand index permutations that one is chosen for the descriptor which contains the lowest number of transpositions ). 

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