Jahn-Teller effect in trigonal symmetry

Abstract
The Jahn-Teller effect in trigonal symmetry is treated in the case where a pair of electronic levels, one singlet and one doublet, are linearly coupled to a vibrational doublet. Methods of calculation are given for the vibronic levels and for the matrix elements of electronic operators. A few numerical examples are presented and the theory is used to explain the uniaxial stress effect on Co3+ in corundum.
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