OPTICAL FLUORESCENCE EXCITATION-SPECTRA OF FLUX-GROWN STOICHIOMETRIC EUROPIUM VANADATE CRYSTALS

The intrinsic site optical absorption of EuVO4 from F-7(0) to 5D0, 5D1, 5D2, and 5D3 exhibits normal behaviour, but sensitive laser excitation profiles measured in the Eu3+:F-7(0) --> 5D0 region (580 nm) map out more than 40-50 defect lines spread over some 60 cm-1. Each of these must be due to a distinct type of defect site in the crystal structure. A number of different EuVO4 crystals prepared from fluxes with different compositions have been used to show that some of these point defects are associated with specific chemical impurities while others seem to be present even in the purest crystals. Electronic Zeeman shifts of the Eu3+:F-7(0) --> D-5(0) optical lines for some of the low-symmetry perturbed sites provide additional information on defect geometry and on the low-lying F-7(1) electronic levels for those specific perturbed sites. High degrees of site distortion are indicated for some of the sites, and principal axes are shown to make oblique angles to normal crystal axes.