Abstract

We are currently investigating the luminescent state of crystals in which the anion is a transition metal complex with the metal formally in a d^o configuration, tetrahedrally surrounded by oxygen. Examples under study are VO₄³⁻, MoO₄²⁻, and also the Cr₂O₇²⁻ ion in which two tetrahedra share a common oxygen. First we established the triplet character (S=1) of the emitting state of this type of ion - which had been proposed [1] but never proven [2] - in some qualitative ESR experiments with optical detection on YVO₄ and K₂Cr₂O₇ crystals. We then initiated a systematic study of the latter system, the results of which are here reported, by three experimental techniques [3]:

1. Excitation and fluorescence spectroscopy with simultaneous (variable frequency) microwave irradiation to induce ESR transitions between the sublevels of a spin triplet in zero field.

2. ESR with optical detection in an external field.

3. Optical Zeeman spectroscopy.

© 1984 Optical Society of America