EMISSION-SPECTRUM OF V4+-ALPHA-AL2O3 - JAHN-TELLER EFFECT IN THE FUNDAMENTAL 2T2G AND EXCITED 2EG STATES

An emission spectrum attributed to V4+- alpha Al 2O3 is observed in the visible region at low temperatures. The zero-phonon lines are due to transitions between the spin-orbit levels from a 2Eg to a 2T2g state split by the trigonal field. A Jahn-Teller effect is shown to occur both in the fundamental and the excited states. A diagram of the potential curves corresponding to these states is proposed to explain the high intensity of the zero-photon line in relation to its difference in energy from the maximum of the band. A weak band is tentatively assigned to the electronic Raman spectrum of the 3E(3T1) level of V3+- alpha Al 2O3.