The luminescent triplet state of the Ba3(VO4)2crystal

Abstract

An E.P.R. study with optical detection is reported of the luminescent state of the Ba3(VO4)2 crystal. The results of the experiments, carried out in zero-field and in an external magnetic field, can be fitted by a spin hamiltonian for an orbitally nondegenerate spin triplet state. Three sets of signals are observed which correspond to three congruent excited species interrelated by the C 3 symmetry about the crystal c axis. The luminescence originates from VO3- 4 ions, the symmetry of which on excitation is lowered from C 3v to Cs by a static Jahn-Teller effect. The zero-field splitting is described by the parameters |D| = 14·185, |E| = 8·729 GHz; the g matrix has as principal values 1·961, 1·976, 1·997; the lifetimes of the three sublevels in zero-field are τ x = 0·5, τ y ⩽ 0>·017, τ z = 1·7 ms. A tentative interpretation is put forward that relates the observed g values to the splitting of a Jahn-Teller unstable 3 T 2 multiplet in a crystal field of C 3v symmetry.