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

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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.