EQUALLY COUPLED (S AND P) PSEUDO-JAHN-TELLER SYSTEM

The SO(4)-invariant pseudo-Jahn-Teller system (s(+)p)(X)( alpha 1g(+) tau 1u(+) epsilon g(+) tau 2g) in equal coupling and with electronic degeneracy is examined. Phonon states with definite SO(4) symmetry are defined in terms of the group chain U(9) contains/implies SO(9) contained in/implied by SO(4) and a method for obtaining matrix elements of phonon-creation operators is derived. It is shown how a quantitative calculation might be performed and a relation between ground-state reduction factors is found. The possibility of applying the model to F-centres in the alkali halides and to the CaO:F+ centre is discussed.