A solution of the calcium oxide F+centre problem using a two mode Jahn-Teller effect)

It is proposed that the excited state of the F + centre in CaO is an example of a new type of Jahn-Teller effect, considered by O'Brien (1969) in which coupling to two different symmetries of vibrational mode occurs. This explanation is capable of removing the apparently puzzling inconsistency between Faraday rotation results on the 355.7 nm zero-phonon line and uniaxial stress splitting data on the same line. It is shown that the new interpretation presents a tenable solution of the problem provided the coupling energies (Jahn-Teller energies) of the excited orbital triplet state to E g and T 2g vibrational modes are within about 70 cm -1 of each other.